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Differences between /sos/main.c (Article 1) and /sos/main.c (Article 6)


001 /* Copyright (C) 2004  The SOS Team               001 /* Copyright (C) 2004  The SOS Team
002    Copyright (C) 1999  Free Software Foundatio    002    Copyright (C) 1999  Free Software Foundation, Inc.
003                                                   003 
004    This program is free software; you can redi    004    This program is free software; you can redistribute it and/or
005    modify it under the terms of the GNU Genera    005    modify it under the terms of the GNU General Public License
006    as published by the Free Software Foundatio    006    as published by the Free Software Foundation; either version 2
007    of the License, or (at your option) any lat    007    of the License, or (at your option) any later version.
008                                                   008    
009    This program is distributed in the hope tha    009    This program is distributed in the hope that it will be useful,
010    but WITHOUT ANY WARRANTY; without even the     010    but WITHOUT ANY WARRANTY; without even the implied warranty of
011    MERCHANTABILITY or FITNESS FOR A PARTICULAR    011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
012    GNU General Public License for more details    012    GNU General Public License for more details.
013                                                   013    
014    You should have received a copy of the GNU     014    You should have received a copy of the GNU General Public License
015    along with this program; if not, write to t    015    along with this program; if not, write to the Free Software
016    Foundation, Inc., 59 Temple Place - Suite 3    016    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
017    USA.                                           017    USA. 
018 */                                                018 */
019                                                   019 
020 /* Include definitions of the multiboot standa    020 /* Include definitions of the multiboot standard */
021 #include <bootstrap/multiboot.h>                  021 #include <bootstrap/multiboot.h>
                                                   >> 022 #include <hwcore/idt.h>
                                                   >> 023 #include <hwcore/gdt.h>
                                                   >> 024 #include <hwcore/irq.h>
                                                   >> 025 #include <hwcore/exception.h>
                                                   >> 026 #include <hwcore/i8254.h>
                                                   >> 027 #include <sos/list.h>
                                                   >> 028 #include <sos/physmem.h>
                                                   >> 029 #include <hwcore/paging.h>
                                                   >> 030 #include <sos/kmem_vmm.h>
                                                   >> 031 #include <sos/kmalloc.h>
022 #include <sos/klibc.h>                            032 #include <sos/klibc.h>
023 #include <sos/assert.h>                           033 #include <sos/assert.h>
024 #include <drivers/x86_videomem.h>                 034 #include <drivers/x86_videomem.h>
025 #include <drivers/bochs.h>                        035 #include <drivers/bochs.h>
026                                                   036 
027                                                   037 
                                                   >> 038 /* Helper function to display each bits of a 32bits integer on the
                                                   >> 039    screen as dark or light carrets */
                                                   >> 040 void display_bits(unsigned char row, unsigned char col,
                                                   >> 041                   unsigned char attribute,
                                                   >> 042                   sos_ui32_t integer)
                                                   >> 043 {
                                                   >> 044   int i;
                                                   >> 045   /* Scan each bit of the integer, MSb first */
                                                   >> 046   for (i = 31 ; i >= 0 ; i--)
                                                   >> 047     {
                                                   >> 048       /* Test if bit i of 'integer' is set */
                                                   >> 049       int bit_i = (integer & (1 << i));
                                                   >> 050       /* Ascii 219 => dark carret, Ascii 177 => light carret */
                                                   >> 051       unsigned char ascii_code = bit_i?219:177;
                                                   >> 052       sos_x86_videomem_putchar(row, col++,
                                                   >> 053                                attribute,
                                                   >> 054                                ascii_code);
                                                   >> 055     }
                                                   >> 056 }
                                                   >> 057 
                                                   >> 058 
                                                   >> 059 /* Clock IRQ handler */
                                                   >> 060 static void clk_it(int intid,
                                                   >> 061                    const struct sos_cpu_kstate *cpu_kstate)
                                                   >> 062 {
                                                   >> 063   static sos_ui32_t clock_count = 0;
                                                   >> 064 
                                                   >> 065   display_bits(0, 48,
                                                   >> 066                SOS_X86_VIDEO_FG_LTGREEN | SOS_X86_VIDEO_BG_BLUE,
                                                   >> 067                clock_count);
                                                   >> 068   clock_count++;
                                                   >> 069 }
                                                   >> 070 
                                                   >> 071 
                                                   >> 072 /* ======================================================================
                                                   >> 073  * Page fault exception handling
                                                   >> 074  */
                                                   >> 075 
                                                   >> 076 /* Helper function to dump a backtrace on bochs and/or the console */
                                                   >> 077 static void dump_backtrace(const struct sos_cpu_kstate *cpu_kstate,
                                                   >> 078                            sos_vaddr_t stack_bottom,
                                                   >> 079                            sos_size_t  stack_size,
                                                   >> 080                            sos_bool_t on_console,
                                                   >> 081                            sos_bool_t on_bochs)
                                                   >> 082 {
                                                   >> 083   static void backtracer(sos_vaddr_t PC,
                                                   >> 084                          sos_vaddr_t params,
                                                   >> 085                          sos_ui32_t depth,
                                                   >> 086                          void *custom_arg)
                                                   >> 087     {
                                                   >> 088       sos_ui32_t invalid = 0xffffffff, *arg1, *arg2, *arg3, *arg4;
                                                   >> 089 
                                                   >> 090       /* Get the address of the first 3 arguments from the
                                                   >> 091          frame. Among these arguments, 0, 1, 2, 3 arguments might be
                                                   >> 092          meaningful (depending on how many arguments the function may
                                                   >> 093          take). */
                                                   >> 094       arg1 = (sos_ui32_t*)params;
                                                   >> 095       arg2 = (sos_ui32_t*)(params+4);
                                                   >> 096       arg3 = (sos_ui32_t*)(params+8);
                                                   >> 097       arg4 = (sos_ui32_t*)(params+12);
                                                   >> 098 
                                                   >> 099       /* Make sure the addresses of these arguments fit inside the
                                                   >> 100          stack boundaries */
                                                   >> 101 #define INTERVAL_OK(b,v,u) ( ((b) <= (sos_vaddr_t)(v)) \
                                                   >> 102                              && ((sos_vaddr_t)(v) < (u)) )
                                                   >> 103       if (!INTERVAL_OK(stack_bottom, arg1, stack_bottom + stack_size))
                                                   >> 104         arg1 = &invalid;
                                                   >> 105       if (!INTERVAL_OK(stack_bottom, arg2, stack_bottom + stack_size))
                                                   >> 106         arg2 = &invalid;
                                                   >> 107       if (!INTERVAL_OK(stack_bottom, arg3, stack_bottom + stack_size))
                                                   >> 108         arg3 = &invalid;
                                                   >> 109       if (!INTERVAL_OK(stack_bottom, arg4, stack_bottom + stack_size))
                                                   >> 110         arg4 = &invalid;
                                                   >> 111 
                                                   >> 112       /* Print the function context for this frame */
                                                   >> 113       if (on_bochs)
                                                   >> 114         sos_bochs_printf("[%d] PC=0x%x arg1=0x%x arg2=0x%x arg3=0x%x\n",
                                                   >> 115                          (unsigned)depth, (unsigned)PC,
                                                   >> 116                          (unsigned)*arg1, (unsigned)*arg2,
                                                   >> 117                          (unsigned)*arg3);
                                                   >> 118 
                                                   >> 119       if (on_console)
                                                   >> 120         sos_x86_videomem_printf(23-depth, 3,
                                                   >> 121                                 SOS_X86_VIDEO_BG_BLUE
                                                   >> 122                                   | SOS_X86_VIDEO_FG_LTGREEN,
                                                   >> 123                                 "[%d] PC=0x%x arg1=0x%x arg2=0x%x arg3=0x%x arg4=0x%x",
                                                   >> 124                                 (unsigned)depth, PC,
                                                   >> 125                                 (unsigned)*arg1, (unsigned)*arg2,
                                                   >> 126                                 (unsigned)*arg3, (unsigned)*arg4);
                                                   >> 127       
                                                   >> 128     }
                                                   >> 129 
                                                   >> 130   sos_backtrace(cpu_kstate, 15, stack_bottom, stack_size, backtracer, NULL);
                                                   >> 131 }
                                                   >> 132 
                                                   >> 133 
                                                   >> 134 /* Page fault exception handler with demand paging for the kernel */
                                                   >> 135 static void pgflt_ex(int intid, const struct sos_cpu_kstate *ctxt)
                                                   >> 136 {
                                                   >> 137   static sos_ui32_t demand_paging_count = 0;
                                                   >> 138   sos_vaddr_t faulting_vaddr = sos_cpu_kstate_get_EX_faulting_vaddr(ctxt);
                                                   >> 139   sos_paddr_t ppage_paddr;
                                                   >> 140 
                                                   >> 141   /* Check if address is covered by any VMM range */
                                                   >> 142   if (! sos_kmem_vmm_is_valid_vaddr(faulting_vaddr))
                                                   >> 143     {
                                                   >> 144       /* No: The page fault is out of any kernel virtual region. For
                                                   >> 145          the moment, we don't handle this. */
                                                   >> 146       dump_backtrace(ctxt,
                                                   >> 147                      bootstrap_stack_bottom,
                                                   >> 148                      bootstrap_stack_size,
                                                   >> 149                      TRUE, TRUE);
                                                   >> 150       sos_display_fatal_error("Unresolved page Fault on access to address 0x%x (info=%x)!",
                                                   >> 151                               (unsigned)faulting_vaddr,
                                                   >> 152                               (unsigned)sos_cpu_kstate_get_EX_info(ctxt));
                                                   >> 153       SOS_ASSERT_FATAL(! "Got page fault (note: demand paging is disabled)");
                                                   >> 154     }
                                                   >> 155 
                                                   >> 156 
                                                   >> 157   /*
                                                   >> 158    * Demand paging
                                                   >> 159    */
                                                   >> 160  
                                                   >> 161   /* Update the number of demand paging requests handled */
                                                   >> 162   demand_paging_count ++;
                                                   >> 163   display_bits(0, 0,
                                                   >> 164                SOS_X86_VIDEO_FG_LTRED | SOS_X86_VIDEO_BG_BLUE,
                                                   >> 165                demand_paging_count);
                                                   >> 166 
                                                   >> 167   /* Allocate a new page for the virtual address */
                                                   >> 168   ppage_paddr = sos_physmem_ref_physpage_new(FALSE);
                                                   >> 169   if (! ppage_paddr)
                                                   >> 170     SOS_ASSERT_FATAL(! "TODO: implement swap. (Out of mem in demand paging because no swap for kernel yet !)");
                                                   >> 171   SOS_ASSERT_FATAL(SOS_OK == sos_paging_map(ppage_paddr,
                                                   >> 172                                             SOS_PAGE_ALIGN_INF(faulting_vaddr),
                                                   >> 173                                             FALSE,
                                                   >> 174                                             SOS_VM_MAP_PROT_READ
                                                   >> 175                                             | SOS_VM_MAP_PROT_WRITE
                                                   >> 176                                             | SOS_VM_MAP_ATOMIC));
                                                   >> 177   sos_physmem_unref_physpage(ppage_paddr);
                                                   >> 178 
                                                   >> 179   /* Ok, we can now return to interrupted context */
                                                   >> 180 }
                                                   >> 181 
                                                   >> 182 
                                                   >> 183 
                                                   >> 184 /* ======================================================================
                                                   >> 185  * Demonstrate the use of the CPU kernet context management API:
                                                   >> 186  *  - A coroutine prints "Hlowrd" and switches to the other after each
                                                   >> 187  *    letter
                                                   >> 188  *  - A coroutine prints "el ol\n" and switches back to the other after
                                                   >> 189  *    each letter.
                                                   >> 190  * The first to reach the '\n' returns back to main.
                                                   >> 191  */
                                                   >> 192 struct sos_cpu_kstate *ctxt_hello1;
                                                   >> 193 struct sos_cpu_kstate *ctxt_hello2;
                                                   >> 194 struct sos_cpu_kstate *ctxt_main;
                                                   >> 195 sos_vaddr_t hello1_stack, hello2_stack;
                                                   >> 196 
                                                   >> 197 static void reclaim_stack(sos_vaddr_t stack_vaddr)
                                                   >> 198 {
                                                   >> 199   sos_kfree(stack_vaddr);
                                                   >> 200 }
                                                   >> 201 
                                                   >> 202 
                                                   >> 203 static void exit_hello12(sos_vaddr_t stack_vaddr)
                                                   >> 204 {
                                                   >> 205   sos_cpu_kstate_exit_to(ctxt_main,
                                                   >> 206                          (sos_cpu_kstate_function_arg1_t*) reclaim_stack,
                                                   >> 207                          stack_vaddr);
                                                   >> 208 }
                                                   >> 209 
                                                   >> 210 
                                                   >> 211 static void hello1 (char *str)
                                                   >> 212 {
                                                   >> 213   for ( ; *str != '\n' ; str++)
                                                   >> 214     {
                                                   >> 215       sos_bochs_printf("hello1: %c\n", *str);
                                                   >> 216       sos_cpu_kstate_switch(& ctxt_hello1, ctxt_hello2);
                                                   >> 217     }
                                                   >> 218 
                                                   >> 219   /* You can uncomment this in case you explicitly want to exit
                                                   >> 220      now. But returning from the function will do the same */
                                                   >> 221   /* sos_cpu_kstate_exit_to(ctxt_main,
                                                   >> 222                          (sos_cpu_kstate_function_arg1_t*) reclaim_stack,
                                                   >> 223                          hello1_stack); */
                                                   >> 224 }
                                                   >> 225 
                                                   >> 226 
                                                   >> 227 static void hello2 (char *str)
                                                   >> 228 {
                                                   >> 229   for ( ; *str != '\n' ; str++)
                                                   >> 230     {
                                                   >> 231       sos_bochs_printf("hello2: %c\n", *str);
                                                   >> 232       sos_cpu_kstate_switch(& ctxt_hello2, ctxt_hello1);
                                                   >> 233     }
                                                   >> 234 
                                                   >> 235   /* You can uncomment this in case you explicitly want to exit
                                                   >> 236      now. But returning from the function will do the same */
                                                   >> 237   /* sos_cpu_kstate_exit_to(ctxt_main,
                                                   >> 238                          (sos_cpu_kstate_function_arg1_t*) reclaim_stack,
                                                   >> 239                          hello2_stack); */
                                                   >> 240 }
                                                   >> 241 
                                                   >> 242 
                                                   >> 243 void print_hello_world ()
                                                   >> 244 {
                                                   >> 245 #define DEMO_STACK_SIZE 1024
                                                   >> 246   /* Allocate the stacks */
                                                   >> 247   hello1_stack = sos_kmalloc(DEMO_STACK_SIZE, 0);
                                                   >> 248   hello2_stack = sos_kmalloc(DEMO_STACK_SIZE, 0);
                                                   >> 249 
                                                   >> 250   /* Initialize the coroutines' contexts */
                                                   >> 251   sos_cpu_kstate_init(&ctxt_hello1,
                                                   >> 252                       (sos_cpu_kstate_function_arg1_t*) hello1,
                                                   >> 253                       (sos_ui32_t) "Hlowrd",
                                                   >> 254                       (sos_vaddr_t) hello1_stack, DEMO_STACK_SIZE,
                                                   >> 255                       (sos_cpu_kstate_function_arg1_t*) exit_hello12,
                                                   >> 256                       (sos_ui32_t) hello1_stack);
                                                   >> 257   sos_cpu_kstate_init(&ctxt_hello2,
                                                   >> 258                       (sos_cpu_kstate_function_arg1_t*) hello2,
                                                   >> 259                       (sos_ui32_t) "el ol\n",
                                                   >> 260                       (sos_vaddr_t) hello2_stack, DEMO_STACK_SIZE,
                                                   >> 261                       (sos_cpu_kstate_function_arg1_t*) exit_hello12,
                                                   >> 262                       (sos_ui32_t) hello2_stack);
                                                   >> 263 
                                                   >> 264   /* Go to first coroutine */
                                                   >> 265   sos_bochs_printf("Printing Hello World\\n...\n");
                                                   >> 266   sos_cpu_kstate_switch(& ctxt_main, ctxt_hello1);
                                                   >> 267 
                                                   >> 268   /* The first coroutine to reach the '\n' switched back to us */
                                                   >> 269   sos_bochs_printf("Back in main !\n");
                                                   >> 270 }
                                                   >> 271 
                                                   >> 272 
                                                   >> 273 /* ======================================================================
                                                   >> 274  * Generate page faults on an unmapped but allocated kernel virtual
                                                   >> 275  * region, which results in a series of physical memory mappings for the
                                                   >> 276  * faulted pages.
                                                   >> 277  */
                                                   >> 278 static void test_demand_paging(int nb_alloc_vpages, int nb_alloc_ppages)
                                                   >> 279 {
                                                   >> 280   int i;
                                                   >> 281   sos_vaddr_t base_vaddr;
                                                   >> 282 
                                                   >> 283   sos_x86_videomem_printf(10, 0,
                                                   >> 284                           SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_LTGREEN,
                                                   >> 285                           "Demand paging test (alloc %dMB of VMM, test %dkB RAM)",
                                                   >> 286                           nb_alloc_vpages >> 8, nb_alloc_ppages << 2);
                                                   >> 287   
                                                   >> 288   /* Allocate virtual memory */
                                                   >> 289   base_vaddr = sos_kmem_vmm_alloc(nb_alloc_vpages, 0);
                                                   >> 290 
                                                   >> 291   SOS_ASSERT_FATAL(base_vaddr != (sos_vaddr_t)NULL);
                                                   >> 292   sos_x86_videomem_printf(11, 0,
                                                   >> 293                           SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 294                           "Allocated virtual region [0x%x, 0x%x[",
                                                   >> 295                           base_vaddr,
                                                   >> 296                           base_vaddr + nb_alloc_vpages*SOS_PAGE_SIZE);
                                                   >> 297 
                                                   >> 298   /* Now use part of it in physical memory */
                                                   >> 299   for (i = 0 ; (i < nb_alloc_ppages) && (i < nb_alloc_vpages) ; i++)
                                                   >> 300     {
                                                   >> 301       /* Compute an address inside the range */
                                                   >> 302       sos_ui32_t *value, j;
                                                   >> 303       sos_vaddr_t vaddr = base_vaddr;
                                                   >> 304       vaddr += (nb_alloc_vpages - (i + 1))*SOS_PAGE_SIZE;
                                                   >> 305       vaddr += 2345;
                                                   >> 306 
                                                   >> 307       sos_x86_videomem_printf(12, 0,
                                                   >> 308                               SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 309                               "Writing %d at virtual address 0x%x...",
                                                   >> 310                               i, vaddr);
                                                   >> 311 
                                                   >> 312       /* Write at this address */
                                                   >> 313       value = (sos_ui32_t*)vaddr;
                                                   >> 314       *value = i;
                                                   >> 315 
                                                   >> 316       /* Yep ! A new page should normally have been allocated for us */
                                                   >> 317       sos_x86_videomem_printf(13, 0,
                                                   >> 318                               SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 319                               "Value read at address 0x%x = %d",
                                                   >> 320                               vaddr, (unsigned)*value);
                                                   >> 321     }
                                                   >> 322 
                                                   >> 323   SOS_ASSERT_FATAL(SOS_OK == sos_kmem_vmm_free(base_vaddr));
                                                   >> 324   /* Yep ! A new page should normally have been allocated for us */
                                                   >> 325   sos_x86_videomem_printf(14, 0,
                                                   >> 326                           SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 327                           "Done (area un-allocated)");
                                                   >> 328 }
                                                   >> 329 
                                                   >> 330 
                                                   >> 331 
                                                   >> 332 /* ======================================================================
                                                   >> 333  * Shows how the backtrace stuff works
                                                   >> 334  */
                                                   >> 335 
                                                   >> 336 /* Recursive function. Print the backtrace from the innermost function */
                                                   >> 337 static void test_backtrace(int i, int magic, sos_vaddr_t stack_bottom,
                                                   >> 338                            sos_size_t  stack_size)
                                                   >> 339 {
                                                   >> 340   if (i <= 0)
                                                   >> 341     {
                                                   >> 342       /* The page fault exception handler will print the backtrace of
                                                   >> 343          this function, because address 0x42 is not mapped */
                                                   >> 344       *((char*)0x42) = 12;
                                                   >> 345 
                                                   >> 346       /* More direct variant: */
                                                   >> 347       /* dump_backtrace(NULL, stack_bottom, stack_size, TRUE, TRUE); */
                                                   >> 348     }
                                                   >> 349   else
                                                   >> 350     test_backtrace(i-1, magic, stack_bottom, stack_size);
                                                   >> 351 }
                                                   >> 352 
                                                   >> 353 
                                                   >> 354 /* ======================================================================
                                                   >> 355  * Parsing of Mathematical expressions
                                                   >> 356  *
                                                   >> 357  * This is a recursive lexer/parser/evaluator for arithmetical
                                                   >> 358  * expressions. Supports both binary +/-* and unary +- operators, as
                                                   >> 359  * well as parentheses.
                                                   >> 360  *
                                                   >> 361  * Terminal tokens (Lexer):
                                                   >> 362  *  - Number: positive integer number
                                                   >> 363  *  - Variable: ascii name (regexp: [a-zA-Z]+)
                                                   >> 364  *  - Operator: +*-/
                                                   >> 365  *  - Opening/closing parentheses
                                                   >> 366  *
                                                   >> 367  * Grammar (Parser):
                                                   >> 368  *  Expression ::= Term E'
                                                   >> 369  *  Expr_lr    ::= + Term Expr_lr | - Term Expr_lr | Nothing
                                                   >> 370  *  Term       ::= Factor Term_lr
                                                   >> 371  *  Term_lr    ::= * Factor Term_lr | / Factor Term_lr | Nothing
                                                   >> 372  *  Factor     ::= - Factor | + Factor | Scalar | ( Expression )
                                                   >> 373  *  Scalar     ::= Number | Variable
                                                   >> 374  *
                                                   >> 375  * Note. This is the left-recursive equivalent of the following basic grammar:
                                                   >> 376  *  Expression ::= Expression + Term | Expression - Term
                                                   >> 377  *  Term       ::= Term * Factor | Term / Factor
                                                   >> 378  *  factor     ::= - Factor | + Factor | Scalar | Variable | ( Expression )
                                                   >> 379  *  Scalar     ::= Number | Variable
                                                   >> 380  *
                                                   >> 381  * The parsing is composed of a 3 stages pipeline:
                                                   >> 382  *  - The reader: reads a string 1 character at a time, transferring
                                                   >> 383  *    the control back to lexer after each char. This function shows the
                                                   >> 384  *    interest in using coroutines, because its state (str) is
                                                   >> 385  *    implicitely stored in the stack between each iteration.
                                                   >> 386  *  - The lexer: consumes the characters from the reader and identifies
                                                   >> 387  *    the terminal tokens, 1 token at a time, transferring control back
                                                   >> 388  *    to the parser after each token. This function shows the interest
                                                   >> 389  *    in using coroutines, because its state (c and got_what_before) is
                                                   >> 390  *    implicitely stored in the stack between each iteration.
                                                   >> 391  *  - The parser: consumes the tokens from the lexer and builds the
                                                   >> 392  *    syntax tree of the expression. There is no real algorithmic
                                                   >> 393  *    interest in defining a coroutine devoted to do this. HOWEVER, we
                                                   >> 394  *    do use one for that because this allows us to switch to a much
                                                   >> 395  *    deeper stack. Actually, the parser is highly recursive, so that
                                                   >> 396  *    the default 16kB stack of the sos_main() function might not be
                                                   >> 397  *    enough. Here, we switch to a 64kB stack, which is safer for
                                                   >> 398  *    recursive functions. The Parser uses intermediary functions: these
                                                   >> 399  *    are defined and implemented as internal nested functions. This is
                                                   >> 400  *    just for the sake of clarity, and is absolutely not mandatory for
                                                   >> 401  *    the algorithm: one can transfer these functions out of the parser
                                                   >> 402  *    function without restriction.
                                                   >> 403  *
                                                   >> 404  * The evaluator is another recursive function that reuses the
                                                   >> 405  * parser's stack to evaluate the parsed expression with the given
                                                   >> 406  * values for the variables present in the expression. As for the
                                                   >> 407  * parser function, this function defines and uses a nested function,
                                                   >> 408  * which can be extracted from the main evaluation function at will.
                                                   >> 409  *
                                                   >> 410  * All these functions support a kind of "exception" feature: when
                                                   >> 411  * something goes wrong, control is transferred DIRECTLY back to the
                                                   >> 412  * sos_main() context, without unrolling the recursions. This shows
                                                   >> 413  * how exceptions basically work, but one should not consider this as
                                                   >> 414  * a reference exceptions implementation. Real exception mechanisms
                                                   >> 415  * (such as that in the C++ language) call the destructors to the
                                                   >> 416  * objects allocated on the stack during the "stack unwinding" process
                                                   >> 417  * upon exception handling, which complicates a lot the mechanism. We
                                                   >> 418  * don't have real Objects here (in the OOP sense, full-featured with
                                                   >> 419  * destructors), so we don't have to complicate things.
                                                   >> 420  *
                                                   >> 421  * After this little coroutine demo, one should forget all about such
                                                   >> 422  * a low-level manual direct manipulation of stacks. This would
                                                   >> 423  * probably mess up the whole kernel to do what we do here (locked
                                                   >> 424  * resources such as mutex/semaphore won't be correctly unlocked,
                                                   >> 425  * ...). Higher level "kernel thread" primitives will soon be
                                                   >> 426  * presented, which provide a higher-level set of APIs to manage CPU
                                                   >> 427  * contexts. You'll have to use EXCLUSIVELY those APIs. If you still
                                                   >> 428  * need a huge stack to do recursion for example, please don't even
                                                   >> 429  * think of changing manually the stack for something bigger ! Simply
                                                   >> 430  * rethink your algorithm, making it non-recursive.
                                                   >> 431  */
                                                   >> 432 
                                                   >> 433 
                                                   >> 434 /* The stacks involved */
                                                   >> 435 static char stack_reader[1024];
                                                   >> 436 static char stack_lexer[1024];
                                                   >> 437 static char deep_stack[65536]; /* For the parser and the evaluator */
                                                   >> 438 
                                                   >> 439 /* The CPU states for the various coroutines */
                                                   >> 440 static struct sos_cpu_kstate *st_reader, *st_lexer, *st_parser,
                                                   >> 441   *st_eval, *st_free, *st_main;
                                                   >> 442 
                                                   >> 443 
                                                   >> 444 /*
                                                   >> 445  * Default exit/reclaim functions: return control to the "sos_main()"
                                                   >> 446  * context
                                                   >> 447  */
                                                   >> 448 static void reclaim(int unused)
                                                   >> 449 {
                                                   >> 450 }
                                                   >> 451 static void func_exit(sos_ui32_t unused)
                                                   >> 452 {
                                                   >> 453   sos_cpu_kstate_exit_to(st_main, (sos_cpu_kstate_function_arg1_t*)reclaim, 0);
                                                   >> 454 }
                                                   >> 455 
                                                   >> 456 
                                                   >> 457 /*
                                                   >> 458  * The reader coroutine and associated variable. This coroutine could
                                                   >> 459  * have been a normal function, except that the current parsed
                                                   >> 460  * character would have to be stored somewhere.
                                                   >> 461  */
                                                   >> 462 static char data_reader_to_lexer;
                                                   >> 463 
                                                   >> 464 static void func_reader(const char *str)
                                                   >> 465 {
                                                   >> 466   for ( ; str && (*str != '\0') ; str++)
                                                   >> 467     {
                                                   >> 468       data_reader_to_lexer = *str;
                                                   >> 469       sos_cpu_kstate_switch(& st_reader, st_lexer);
                                                   >> 470     }
                                                   >> 471 
                                                   >> 472   data_reader_to_lexer = '\0';
                                                   >> 473   sos_cpu_kstate_switch(& st_reader, st_lexer);
                                                   >> 474 }
                                                   >> 475 
028                                                   476 
029 /* The C entry point of our operating system * !! 477 /*
                                                   >> 478  * The Lexer coroutine and associated types/variables. This coroutine
                                                   >> 479  * could have been a normal function, except that the current parsed
                                                   >> 480  * character, token and previous token would have to be stored
                                                   >> 481  * somewhere.
                                                   >> 482  */
                                                   >> 483 #define STR_VAR_MAXLEN 16
                                                   >> 484 static struct lex_elem
                                                   >> 485 {
                                                   >> 486   enum { LEX_IS_NUMBER, LEX_IS_OPER, LEX_IS_VAR,
                                                   >> 487          LEX_IS_OPENPAR, LEX_IS_CLOSEPAR, LEX_END } type;
                                                   >> 488   union {
                                                   >> 489     int  number;
                                                   >> 490     char operator;
                                                   >> 491     char var[STR_VAR_MAXLEN];
                                                   >> 492   };
                                                   >> 493 } data_lexer_to_parser;
                                                   >> 494 
                                                   >> 495 static void func_lexer(sos_ui32_t unused)
                                                   >> 496 {
                                                   >> 497   char c;
                                                   >> 498   enum { GOT_SPACE, GOT_NUM, GOT_OP, GOT_STR,
                                                   >> 499          GOT_OPENPAR, GOT_CLOSEPAR } got_what, got_what_before;
                                                   >> 500 
                                                   >> 501   data_lexer_to_parser.number = 0;
                                                   >> 502   got_what_before = GOT_SPACE;
                                                   >> 503   do
                                                   >> 504     {
                                                   >> 505       /* Consume one character from the reader */
                                                   >> 506       sos_cpu_kstate_switch(& st_lexer, st_reader);
                                                   >> 507       c = data_reader_to_lexer;
                                                   >> 508 
                                                   >> 509       /* Classify the consumed character */
                                                   >> 510       if ( (c >= '0') && (c <= '9') )
                                                   >> 511         got_what = GOT_NUM;
                                                   >> 512       else if ( (c == '+') || (c == '-') || (c == '*') || (c == '/') )
                                                   >> 513         got_what = GOT_OP;
                                                   >> 514       else if ( ( (c >= 'a') && (c <= 'z') )
                                                   >> 515                 || ( (c >= 'A') && (c <= 'Z') ) )
                                                   >> 516         got_what = GOT_STR;
                                                   >> 517       else if (c == '(')
                                                   >> 518         got_what = GOT_OPENPAR;
                                                   >> 519       else if (c == ')')
                                                   >> 520         got_what = GOT_CLOSEPAR;
                                                   >> 521       else
                                                   >> 522         got_what = GOT_SPACE;
                                                   >> 523 
                                                   >> 524       /* Determine whether the current token is ended */
                                                   >> 525       if ( (got_what != got_what_before)
                                                   >> 526            || (got_what_before == GOT_OP)
                                                   >> 527            || (got_what_before == GOT_OPENPAR)
                                                   >> 528            || (got_what_before == GOT_CLOSEPAR) )
                                                   >> 529         {
                                                   >> 530           /* return control back to the parser if the previous token
                                                   >> 531              has been recognized */
                                                   >> 532           if ( (got_what_before != GOT_SPACE) )
                                                   >> 533             sos_cpu_kstate_switch(& st_lexer, st_parser);
                                                   >> 534 
                                                   >> 535           data_lexer_to_parser.number = 0;
                                                   >> 536         }
                                                   >> 537 
                                                   >> 538       /* Update the token being currently recognized */
                                                   >> 539       if (got_what == GOT_OP)
                                                   >> 540         {
                                                   >> 541           data_lexer_to_parser.type = LEX_IS_OPER;
                                                   >> 542           data_lexer_to_parser.operator = c;
                                                   >> 543         }
                                                   >> 544       else if (got_what == GOT_NUM)
                                                   >> 545         {
                                                   >> 546           data_lexer_to_parser.type = LEX_IS_NUMBER;
                                                   >> 547           data_lexer_to_parser.number *= 10;
                                                   >> 548           data_lexer_to_parser.number += (c - '0');
                                                   >> 549         }
                                                   >> 550       else if (got_what == GOT_STR)
                                                   >> 551         {
                                                   >> 552           char to_cat[] = { c, '\0' };
                                                   >> 553           data_lexer_to_parser.type = LEX_IS_VAR;
                                                   >> 554           strzcat(data_lexer_to_parser.var, to_cat, STR_VAR_MAXLEN);
                                                   >> 555         }
                                                   >> 556       else if (got_what == GOT_OPENPAR)
                                                   >> 557         data_lexer_to_parser.type = LEX_IS_OPENPAR;
                                                   >> 558       else if (got_what == GOT_CLOSEPAR)
                                                   >> 559         data_lexer_to_parser.type = LEX_IS_CLOSEPAR;
                                                   >> 560 
                                                   >> 561       got_what_before = got_what;
                                                   >> 562     }
                                                   >> 563   while (c != '\0');
                                                   >> 564 
                                                   >> 565   /* Transfer last recognized token to the parser */
                                                   >> 566   if ( (got_what_before != GOT_SPACE) )
                                                   >> 567     sos_cpu_kstate_switch(& st_lexer, st_parser);
                                                   >> 568 
                                                   >> 569   /* Signal that no more token are available */
                                                   >> 570   data_lexer_to_parser.type = LEX_END;
                                                   >> 571   sos_cpu_kstate_switch(& st_lexer, st_parser);
                                                   >> 572 
                                                   >> 573   /* Exception: parser asks for a token AFTER having received the last
                                                   >> 574      one */
                                                   >> 575   sos_bochs_printf("Error: end of string already reached !\n");
                                                   >> 576   sos_cpu_kstate_switch(& st_lexer, st_main);
                                                   >> 577 }
                                                   >> 578 
                                                   >> 579 
                                                   >> 580 /*
                                                   >> 581  * The Parser coroutine and associated types/variables
                                                   >> 582  */
                                                   >> 583 struct syntax_node
                                                   >> 584 {
                                                   >> 585   enum { YY_IS_BINOP, YY_IS_UNAROP, YY_IS_NUM, YY_IS_VAR } type;
                                                   >> 586   union
                                                   >> 587   {
                                                   >> 588     int  number;
                                                   >> 589     char var[STR_VAR_MAXLEN];
                                                   >> 590     struct
                                                   >> 591     {
                                                   >> 592       char op;
                                                   >> 593       struct syntax_node *parm_left, *parm_right;
                                                   >> 594     } binop;
                                                   >> 595     struct
                                                   >> 596     {
                                                   >> 597       char op;
                                                   >> 598       struct syntax_node *parm;
                                                   >> 599     } unarop;
                                                   >> 600   };
                                                   >> 601 };
                                                   >> 602 
                                                   >> 603 static void func_parser(struct syntax_node ** syntax_tree)
                                                   >> 604 {
                                                   >> 605   static struct syntax_node *alloc_node_num(int val);
                                                   >> 606   static struct syntax_node *alloc_node_var(const char * name);
                                                   >> 607   static struct syntax_node *alloc_node_binop(char op,
                                                   >> 608                                               struct syntax_node *parm_left,
                                                   >> 609                                               struct syntax_node *parm_right);
                                                   >> 610   static struct syntax_node *alloc_node_unarop(char op,
                                                   >> 611                                                struct syntax_node *parm);
                                                   >> 612   static struct syntax_node * get_expr();
                                                   >> 613   static struct syntax_node * get_expr_lr(struct syntax_node *n);
                                                   >> 614   static struct syntax_node * get_term();
                                                   >> 615   static struct syntax_node * get_term_lr(struct syntax_node *n);
                                                   >> 616   static struct syntax_node * get_factor();
                                                   >> 617   static struct syntax_node * get_scalar();
                                                   >> 618 
                                                   >> 619   /* Create a new node to store a number */
                                                   >> 620   static struct syntax_node *alloc_node_num(int val)
                                                   >> 621     {
                                                   >> 622       struct syntax_node *n
                                                   >> 623         = (struct syntax_node*) sos_kmalloc(sizeof(struct syntax_node), 0);
                                                   >> 624       n->type   = YY_IS_NUM;
                                                   >> 625       n->number = val;
                                                   >> 626       return n;
                                                   >> 627     }
                                                   >> 628   /* Create a new node to store a variable */
                                                   >> 629   static struct syntax_node *alloc_node_var(const char * name)
                                                   >> 630     {
                                                   >> 631       struct syntax_node *n
                                                   >> 632         = (struct syntax_node*) sos_kmalloc(sizeof(struct syntax_node), 0);
                                                   >> 633       n->type   = YY_IS_VAR;
                                                   >> 634       strzcpy(n->var, name, STR_VAR_MAXLEN);
                                                   >> 635       return n;
                                                   >> 636     }
                                                   >> 637   /* Create a new node to store a binary operator */
                                                   >> 638   static struct syntax_node *alloc_node_binop(char op,
                                                   >> 639                                               struct syntax_node *parm_left,
                                                   >> 640                                               struct syntax_node *parm_right)
                                                   >> 641     {
                                                   >> 642       struct syntax_node *n
                                                   >> 643         = (struct syntax_node*) sos_kmalloc(sizeof(struct syntax_node), 0);
                                                   >> 644       n->type             = YY_IS_BINOP;
                                                   >> 645       n->binop.op         = op;
                                                   >> 646       n->binop.parm_left  = parm_left;
                                                   >> 647       n->binop.parm_right = parm_right;
                                                   >> 648       return n;
                                                   >> 649     }
                                                   >> 650   /* Create a new node to store a unary operator */
                                                   >> 651   static struct syntax_node *alloc_node_unarop(char op,
                                                   >> 652                                                struct syntax_node *parm)
                                                   >> 653     {
                                                   >> 654       struct syntax_node *n
                                                   >> 655         = (struct syntax_node*) sos_kmalloc(sizeof(struct syntax_node), 0);
                                                   >> 656       n->type        = YY_IS_UNAROP;
                                                   >> 657       n->unarop.op   = op;
                                                   >> 658       n->unarop.parm = parm;
                                                   >> 659       return n;
                                                   >> 660     }
                                                   >> 661 
                                                   >> 662   /* Raise an exception: transfer control back to main context,
                                                   >> 663      without unrolling the whole recursion */
                                                   >> 664   static void parser_exception(const char *str)
                                                   >> 665     {
                                                   >> 666       sos_bochs_printf("Parser exception: %s\n", str);
                                                   >> 667       sos_cpu_kstate_switch(& st_parser, st_main);
                                                   >> 668     }
                                                   >> 669 
                                                   >> 670   /* Consume the current terminal "number" token and ask for a new
                                                   >> 671      token */
                                                   >> 672   static int get_number()
                                                   >> 673     {
                                                   >> 674       int v;
                                                   >> 675       if (data_lexer_to_parser.type != LEX_IS_NUMBER)
                                                   >> 676         parser_exception("Expected number");
                                                   >> 677       v = data_lexer_to_parser.number;
                                                   >> 678       sos_cpu_kstate_switch(& st_parser, st_lexer);
                                                   >> 679       return v;
                                                   >> 680     }
                                                   >> 681   /* Consume the current terminal "variable" token and ask for a new
                                                   >> 682      token */
                                                   >> 683   static void get_str(char name[STR_VAR_MAXLEN])
                                                   >> 684     {
                                                   >> 685       if (data_lexer_to_parser.type != LEX_IS_VAR)
                                                   >> 686         parser_exception("Expected variable");
                                                   >> 687       strzcpy(name, data_lexer_to_parser.var, STR_VAR_MAXLEN);
                                                   >> 688       sos_cpu_kstate_switch(& st_parser, st_lexer);
                                                   >> 689     }
                                                   >> 690   /* Consume the current terminal "operator" token and ask for a new
                                                   >> 691      token */
                                                   >> 692   static char get_op()
                                                   >> 693     {
                                                   >> 694       char op;
                                                   >> 695       if (data_lexer_to_parser.type != LEX_IS_OPER)
                                                   >> 696         parser_exception("Expected operator");
                                                   >> 697       op = data_lexer_to_parser.operator;
                                                   >> 698       sos_cpu_kstate_switch(& st_parser, st_lexer);
                                                   >> 699       return op;
                                                   >> 700     }
                                                   >> 701   /* Consume the current terminal "parenthese" token and ask for a new
                                                   >> 702      token */
                                                   >> 703   static void get_par()
                                                   >> 704     {
                                                   >> 705       if ( (data_lexer_to_parser.type != LEX_IS_OPENPAR)
                                                   >> 706            && (data_lexer_to_parser.type != LEX_IS_CLOSEPAR) )
                                                   >> 707         parser_exception("Expected parenthese");
                                                   >> 708       sos_cpu_kstate_switch(& st_parser, st_lexer);
                                                   >> 709     }
                                                   >> 710 
                                                   >> 711   /* Parse an Expression */
                                                   >> 712   static struct syntax_node * get_expr()
                                                   >> 713     {
                                                   >> 714       struct syntax_node *t = get_term();
                                                   >> 715       return get_expr_lr(t);
                                                   >> 716     }
                                                   >> 717   /* Parse an Expr_lr */
                                                   >> 718   static struct syntax_node * get_expr_lr(struct syntax_node *n)
                                                   >> 719     {
                                                   >> 720       if ( (data_lexer_to_parser.type == LEX_IS_OPER)
                                                   >> 721            && ( (data_lexer_to_parser.operator == '+')
                                                   >> 722                 || (data_lexer_to_parser.operator == '-') ) )
                                                   >> 723         {
                                                   >> 724           char op = get_op();
                                                   >> 725           struct syntax_node *term = get_term();
                                                   >> 726           struct syntax_node *node_op = alloc_node_binop(op, n, term);
                                                   >> 727           return get_expr_lr(node_op);
                                                   >> 728         }
                                                   >> 729       return n;
                                                   >> 730     }
                                                   >> 731   /* Parse a Term */
                                                   >> 732   static struct syntax_node * get_term()
                                                   >> 733     {
                                                   >> 734       struct syntax_node *f1 = get_factor();
                                                   >> 735       return get_term_lr(f1);
                                                   >> 736     }
                                                   >> 737   /* Parse a Term_lr */
                                                   >> 738   static struct syntax_node * get_term_lr(struct syntax_node *n)
                                                   >> 739     {
                                                   >> 740       if ( (data_lexer_to_parser.type == LEX_IS_OPER)
                                                   >> 741            && ( (data_lexer_to_parser.operator == '*')
                                                   >> 742                 || (data_lexer_to_parser.operator == '/') ) )
                                                   >> 743         {
                                                   >> 744           char op = get_op();
                                                   >> 745           struct syntax_node *factor = get_factor();
                                                   >> 746           struct syntax_node *node_op = alloc_node_binop(op, n, factor);
                                                   >> 747           return get_term_lr(node_op);
                                                   >> 748         }
                                                   >> 749       return n;
                                                   >> 750     }
                                                   >> 751   /* Parse a Factor */
                                                   >> 752   static struct syntax_node * get_factor()
                                                   >> 753     {
                                                   >> 754       if ( (data_lexer_to_parser.type == LEX_IS_OPER)
                                                   >> 755            && ( (data_lexer_to_parser.operator == '-')
                                                   >> 756                 || (data_lexer_to_parser.operator == '+') ) )
                                                   >> 757         { char op = data_lexer_to_parser.operator;
                                                   >> 758         get_op(); return alloc_node_unarop(op, get_factor()); }
                                                   >> 759       else if (data_lexer_to_parser.type == LEX_IS_OPENPAR)
                                                   >> 760         {
                                                   >> 761           struct syntax_node *expr;
                                                   >> 762           get_par();
                                                   >> 763           expr = get_expr();
                                                   >> 764           if (data_lexer_to_parser.type != LEX_IS_CLOSEPAR)
                                                   >> 765             parser_exception("Mismatched parentheses");
                                                   >> 766           get_par();
                                                   >> 767           return expr;
                                                   >> 768         }
                                                   >> 769   
                                                   >> 770       return get_scalar();
                                                   >> 771     }
                                                   >> 772   /* Parse a Scalar */
                                                   >> 773   static struct syntax_node * get_scalar()
                                                   >> 774     {
                                                   >> 775       if (data_lexer_to_parser.type != LEX_IS_NUMBER)
                                                   >> 776         {
                                                   >> 777           char var[STR_VAR_MAXLEN];
                                                   >> 778           get_str(var);
                                                   >> 779           return alloc_node_var(var);
                                                   >> 780         }
                                                   >> 781       return alloc_node_num(get_number());
                                                   >> 782     }
                                                   >> 783 
                                                   >> 784 
                                                   >> 785   /*
                                                   >> 786    * Body of the function
                                                   >> 787    */
                                                   >> 788 
                                                   >> 789   /* Get the first token */
                                                   >> 790   sos_cpu_kstate_switch(& st_parser, st_lexer);
                                                   >> 791 
                                                   >> 792   /* Begin the parsing ! */
                                                   >> 793   *syntax_tree = get_expr();
                                                   >> 794   /* The result is returned in the syntax_tree parameter */
                                                   >> 795 }
                                                   >> 796 
                                                   >> 797 
                                                   >> 798 /*
                                                   >> 799  * Setup the parser's pipeline
                                                   >> 800  */
                                                   >> 801 static struct syntax_node * parse_expression(const char *expr)
                                                   >> 802 {
                                                   >> 803   struct syntax_node *retval = NULL;
                                                   >> 804 
                                                   >> 805   /* Build the context of the functions in the pipeline */
                                                   >> 806   sos_cpu_kstate_init(& st_reader,
                                                   >> 807                       (sos_cpu_kstate_function_arg1_t*)func_reader,
                                                   >> 808                       (sos_ui32_t)expr,
                                                   >> 809                       (sos_vaddr_t)stack_reader, sizeof(stack_reader),
                                                   >> 810                       (sos_cpu_kstate_function_arg1_t*)func_exit, 0);
                                                   >> 811   sos_cpu_kstate_init(& st_lexer,
                                                   >> 812                       (sos_cpu_kstate_function_arg1_t*)func_lexer,
                                                   >> 813                       0,
                                                   >> 814                       (sos_vaddr_t)stack_lexer, sizeof(stack_lexer),
                                                   >> 815                       (sos_cpu_kstate_function_arg1_t*)func_exit, 0);
                                                   >> 816   sos_cpu_kstate_init(& st_parser,
                                                   >> 817                       (sos_cpu_kstate_function_arg1_t*)func_parser,
                                                   >> 818                       (sos_ui32_t) /* syntax tree ! */&retval,
                                                   >> 819                       (sos_vaddr_t)deep_stack, sizeof(deep_stack),
                                                   >> 820                       (sos_cpu_kstate_function_arg1_t*)func_exit, 0);
                                                   >> 821 
                                                   >> 822   /* Parse the expression */
                                                   >> 823   sos_cpu_kstate_switch(& st_main, st_parser);
                                                   >> 824   return retval;
                                                   >> 825 }
                                                   >> 826 
                                                   >> 827 
                                                   >> 828 /*
                                                   >> 829  * The Evaluator coroutine and associated types/variables
                                                   >> 830  */
                                                   >> 831 struct func_eval_params
                                                   >> 832 {
                                                   >> 833   const struct syntax_node *e;
                                                   >> 834   const char **var_name;
                                                   >> 835   int *var_val;
                                                   >> 836   int nb_vars;
                                                   >> 837 
                                                   >> 838   int result;
                                                   >> 839 };
                                                   >> 840 
                                                   >> 841 static void func_eval(struct func_eval_params *parms)
                                                   >> 842 {
                                                   >> 843   /* The internal (recursive) nested function to evaluate each node of
                                                   >> 844      the syntax tree */
                                                   >> 845   static int rec_eval(const struct syntax_node *n,
                                                   >> 846                       const char* var_name[], int var_val[], int nb_vars)
                                                   >> 847     {
                                                   >> 848       switch (n->type)
                                                   >> 849         {
                                                   >> 850         case YY_IS_NUM:
                                                   >> 851           return n->number;
                                                   >> 852 
                                                   >> 853         case YY_IS_VAR:
                                                   >> 854           {
                                                   >> 855             int i;
                                                   >> 856             for (i = 0 ; i < nb_vars ; i++)
                                                   >> 857               if (0 == strcmp(var_name[i], n->var))
                                                   >> 858                 return var_val[i];
                                                   >> 859 
                                                   >> 860             /* Exception: no variable with that name ! */
                                                   >> 861             sos_bochs_printf("ERROR: unknown variable %s\n", n->var);
                                                   >> 862             sos_cpu_kstate_switch(& st_eval, st_main);
                                                   >> 863           }
                                                   >> 864 
                                                   >> 865         case YY_IS_BINOP:
                                                   >> 866           {
                                                   >> 867             int left = rec_eval(n->binop.parm_left,
                                                   >> 868                                 var_name, var_val, nb_vars);
                                                   >> 869             int right = rec_eval(n->binop.parm_right,
                                                   >> 870                                  var_name, var_val, nb_vars);
                                                   >> 871             switch (n->binop.op)
                                                   >> 872               {
                                                   >> 873               case '+': return left + right;
                                                   >> 874               case '-': return left - right;
                                                   >> 875               case '*': return left * right;
                                                   >> 876               case '/': return left / right;
                                                   >> 877               default:
                                                   >> 878                 /* Exception: no such operator (INTERNAL error) ! */
                                                   >> 879                 sos_bochs_printf("ERROR: unknown binop %c\n", n->binop.op);
                                                   >> 880                 sos_cpu_kstate_switch(& st_eval, st_main);
                                                   >> 881               }
                                                   >> 882           }
                                                   >> 883 
                                                   >> 884         case YY_IS_UNAROP:
                                                   >> 885           {
                                                   >> 886             int arg = rec_eval(n->unarop.parm, var_name, var_val, nb_vars);
                                                   >> 887             switch (n->unarop.op)
                                                   >> 888               {
                                                   >> 889               case '-': return -arg;
                                                   >> 890               case '+': return arg;
                                                   >> 891               default:
                                                   >> 892                 /* Exception: no such operator (INTERNAL error) ! */
                                                   >> 893                 sos_bochs_printf("ERROR: unknown unarop %c\n", n->unarop.op);
                                                   >> 894                 sos_cpu_kstate_switch(& st_eval, st_main);
                                                   >> 895               }
                                                   >> 896           }
                                                   >> 897         }
                                                   >> 898       
                                                   >> 899       /* Exception: no such syntax node (INTERNAL error) ! */
                                                   >> 900       sos_bochs_printf("ERROR: invalid node type\n");
                                                   >> 901       sos_cpu_kstate_switch(& st_eval, st_main);
                                                   >> 902       return -1; /* let's make gcc happy */
                                                   >> 903     }
                                                   >> 904 
                                                   >> 905 
                                                   >> 906   /*
                                                   >> 907    * Function BODY
                                                   >> 908    */
                                                   >> 909   /* Update p.result returned back to calling function */
                                                   >> 910   parms->result
                                                   >> 911     = rec_eval(parms->e, parms->var_name, parms->var_val, parms->nb_vars);
                                                   >> 912 }
                                                   >> 913 
                                                   >> 914 /*
                                                   >> 915  * Change the stack for something larger in order to call the
                                                   >> 916  * recursive function above in a safe way
                                                   >> 917  */
                                                   >> 918 static int eval_expression(const struct syntax_node *e,
                                                   >> 919                            const char* var_name[], int var_val[], int nb_vars)
                                                   >> 920 {
                                                   >> 921   struct func_eval_params p
                                                   >> 922     = (struct func_eval_params){ .e=e,
                                                   >> 923                                  .var_name=var_name,
                                                   >> 924                                  .var_val=var_val,
                                                   >> 925                                  .nb_vars=nb_vars,
                                                   >> 926                                  .result = 0 };
                                                   >> 927 
                                                   >> 928   sos_cpu_kstate_init(& st_eval,
                                                   >> 929                       (sos_cpu_kstate_function_arg1_t*)func_eval,
                                                   >> 930                       (sos_ui32_t)/* p.result is modified upon success */&p,
                                                   >> 931                       (sos_vaddr_t)deep_stack, sizeof(deep_stack),
                                                   >> 932                       (sos_cpu_kstate_function_arg1_t*)func_exit, 0);
                                                   >> 933 
                                                   >> 934   /* Go ! */
                                                   >> 935   sos_cpu_kstate_switch(& st_main, st_eval);
                                                   >> 936   return p.result;
                                                   >> 937 }
                                                   >> 938 
                                                   >> 939 
                                                   >> 940 /*
                                                   >> 941  * Function to free the syntax tree
                                                   >> 942  */
                                                   >> 943 static void func_free(struct syntax_node *n)
                                                   >> 944 {
                                                   >> 945   switch (n->type)
                                                   >> 946     {
                                                   >> 947     case YY_IS_NUM:
                                                   >> 948     case YY_IS_VAR:
                                                   >> 949       break;
                                                   >> 950       
                                                   >> 951     case YY_IS_BINOP:
                                                   >> 952       func_free(n->binop.parm_left);
                                                   >> 953       func_free(n->binop.parm_right);
                                                   >> 954       break;
                                                   >> 955       
                                                   >> 956     case YY_IS_UNAROP:
                                                   >> 957       func_free(n->unarop.parm);
                                                   >> 958       break;
                                                   >> 959     }
                                                   >> 960   
                                                   >> 961   sos_kfree((sos_vaddr_t)n);
                                                   >> 962 }
                                                   >> 963 
                                                   >> 964 /*
                                                   >> 965  * Change the stack for something larger in order to call the
                                                   >> 966  * recursive function above in a safe way
                                                   >> 967  */
                                                   >> 968 static void free_syntax_tree(struct syntax_node *tree)
                                                   >> 969 {
                                                   >> 970   sos_cpu_kstate_init(& st_free,
                                                   >> 971                       (sos_cpu_kstate_function_arg1_t*)func_free,
                                                   >> 972                       (sos_ui32_t)tree,
                                                   >> 973                       (sos_vaddr_t)deep_stack, sizeof(deep_stack),
                                                   >> 974                       (sos_cpu_kstate_function_arg1_t*)func_exit, 0);
                                                   >> 975 
                                                   >> 976   /* Go ! */
                                                   >> 977   sos_cpu_kstate_switch(& st_main, st_free);
                                                   >> 978 }
                                                   >> 979 
                                                   >> 980 
                                                   >> 981 /* ======================================================================
                                                   >> 982  * The C entry point of our operating system
                                                   >> 983  */
030 void sos_main(unsigned long magic, unsigned lo    984 void sos_main(unsigned long magic, unsigned long addr)
031 {                                                 985 {
032   unsigned i;                                     986   unsigned i;
                                                   >> 987   sos_paddr_t sos_kernel_core_base_paddr, sos_kernel_core_top_paddr;
                                                   >> 988   struct syntax_node *syntax_tree;
033                                                   989 
034   /* Grub sends us a structure, called multibo    990   /* Grub sends us a structure, called multiboot_info_t with a lot of
035      precious informations about the system, s    991      precious informations about the system, see the multiboot
036      documentation for more information. */       992      documentation for more information. */
037   multiboot_info_t *mbi;                          993   multiboot_info_t *mbi;
038   mbi = (multiboot_info_t *) addr;                994   mbi = (multiboot_info_t *) addr;
039                                                   995 
040   /* Setup bochs and console, and clear the co    996   /* Setup bochs and console, and clear the console */
041   sos_bochs_setup();                              997   sos_bochs_setup();
042                                                   998 
043   sos_x86_videomem_setup();                       999   sos_x86_videomem_setup();
044   sos_x86_videomem_cls(SOS_X86_VIDEO_BG_BLUE);    1000   sos_x86_videomem_cls(SOS_X86_VIDEO_BG_BLUE);
045                                                   1001 
046   /* Greetings from SOS */                        1002   /* Greetings from SOS */
047   if (magic == MULTIBOOT_BOOTLOADER_MAGIC)        1003   if (magic == MULTIBOOT_BOOTLOADER_MAGIC)
048     /* Loaded with Grub */                        1004     /* Loaded with Grub */
049     sos_x86_videomem_printf(1, 0,                 1005     sos_x86_videomem_printf(1, 0,
050                             SOS_X86_VIDEO_FG_Y    1006                             SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
051                             "Welcome From GRUB    1007                             "Welcome From GRUB to %s%c RAM is %dMB (upper mem = 0x%x kB)",
052                             "SOS", ',',           1008                             "SOS", ',',
053                             (unsigned)(mbi->me    1009                             (unsigned)(mbi->mem_upper >> 10) + 1,
054                             (unsigned)mbi->mem    1010                             (unsigned)mbi->mem_upper);
055   else                                            1011   else
056     /* Not loaded with grub */                    1012     /* Not loaded with grub */
057     sos_x86_videomem_printf(1, 0,                 1013     sos_x86_videomem_printf(1, 0,
058                             SOS_X86_VIDEO_FG_Y    1014                             SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
059                             "Welcome to SOS");    1015                             "Welcome to SOS");
060                                                   1016 
061   sos_bochs_putstring("Message in a bochs\n");    1017   sos_bochs_putstring("Message in a bochs\n");
062                                                   1018 
                                                   >> 1019   /* Setup CPU segmentation and IRQ subsystem */
                                                   >> 1020   sos_gdt_subsystem_setup();
                                                   >> 1021   sos_idt_subsystem_setup();
                                                   >> 1022 
                                                   >> 1023   /* Setup SOS IRQs and exceptions subsystem */
                                                   >> 1024   sos_exception_subsystem_setup();
                                                   >> 1025   sos_irq_subsystem_setup();
                                                   >> 1026 
                                                   >> 1027   /* Configure the timer so as to raise the IRQ0 at a 100Hz rate */
                                                   >> 1028   sos_i8254_set_frequency(100);
                                                   >> 1029 
                                                   >> 1030   /* We need a multiboot-compliant boot loader to get the size of the RAM */
                                                   >> 1031   if (magic != MULTIBOOT_BOOTLOADER_MAGIC)
                                                   >> 1032     {
                                                   >> 1033       sos_x86_videomem_putstring(20, 0,
                                                   >> 1034                                  SOS_X86_VIDEO_FG_LTRED
                                                   >> 1035                                    | SOS_X86_VIDEO_BG_BLUE
                                                   >> 1036                                    | SOS_X86_VIDEO_FG_BLINKING,
                                                   >> 1037                                  "I'm not loaded with Grub !");
                                                   >> 1038       /* STOP ! */
                                                   >> 1039       for (;;)
                                                   >> 1040         continue;
                                                   >> 1041     }
                                                   >> 1042 
                                                   >> 1043   /*
                                                   >> 1044    * Some interrupt handlers
                                                   >> 1045    */
                                                   >> 1046 
                                                   >> 1047   /* Binding some HW interrupts and exceptions to software routines */
                                                   >> 1048   sos_irq_set_routine(SOS_IRQ_TIMER,
                                                   >> 1049                       clk_it);
                                                   >> 1050 
                                                   >> 1051   /*
                                                   >> 1052    * Setup physical memory management
                                                   >> 1053    */
                                                   >> 1054 
                                                   >> 1055   /* Multiboot says: "The value returned for upper memory is maximally
                                                   >> 1056      the address of the first upper memory hole minus 1 megabyte.". It
                                                   >> 1057      also adds: "It is not guaranteed to be this value." aka "YMMV" ;) */
                                                   >> 1058   sos_physmem_subsystem_setup((mbi->mem_upper<<10) + (1<<20),
                                                   >> 1059                               & sos_kernel_core_base_paddr,
                                                   >> 1060                               & sos_kernel_core_top_paddr);
                                                   >> 1061   
                                                   >> 1062   /*
                                                   >> 1063    * Switch to paged-memory mode
                                                   >> 1064    */
                                                   >> 1065 
                                                   >> 1066   /* Disabling interrupts should seem more correct, but it's not really
                                                   >> 1067      necessary at this stage */
                                                   >> 1068   SOS_ASSERT_FATAL(SOS_OK ==
                                                   >> 1069                    sos_paging_subsystem_setup(sos_kernel_core_base_paddr,
                                                   >> 1070                                               sos_kernel_core_top_paddr));
                                                   >> 1071   
                                                   >> 1072   /* Bind the page fault exception */
                                                   >> 1073   sos_exception_set_routine(SOS_EXCEPT_PAGE_FAULT,
                                                   >> 1074                             pgflt_ex);
                                                   >> 1075 
                                                   >> 1076   /*
                                                   >> 1077    * Setup kernel virtual memory allocator
                                                   >> 1078    */ 
                                                   >> 1079 
                                                   >> 1080   if (sos_kmem_vmm_subsystem_setup(sos_kernel_core_base_paddr,
                                                   >> 1081                                    sos_kernel_core_top_paddr,
                                                   >> 1082                                    bootstrap_stack_bottom,
                                                   >> 1083                                    bootstrap_stack_bottom
                                                   >> 1084                                    + bootstrap_stack_size))
                                                   >> 1085     sos_bochs_printf("Could not setup the Kernel virtual space allocator\n");
                                                   >> 1086 
                                                   >> 1087   if (sos_kmalloc_subsystem_setup())
                                                   >> 1088     sos_bochs_printf("Could not setup the Kmalloc subsystem\n");
                                                   >> 1089 
                                                   >> 1090   /*
                                                   >> 1091    * Enabling the HW interrupts here, this will make the timer HW
                                                   >> 1092    * interrupt call our clk_it handler
                                                   >> 1093    */
                                                   >> 1094   asm volatile ("sti\n");
                                                   >> 1095 
                                                   >> 1096   /*
                                                   >> 1097    * Print hello world using coroutines
                                                   >> 1098    */
                                                   >> 1099   print_hello_world();
                                                   >> 1100 
                                                   >> 1101 
                                                   >> 1102   /*
                                                   >> 1103    * Run coroutine tests
                                                   >> 1104    */
                                                   >> 1105   sos_x86_videomem_printf(4, 0,
                                                   >> 1106                           SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_LTGREEN,
                                                   >> 1107                           "Coroutine test");
                                                   >> 1108   sos_x86_videomem_printf(5, 0,
                                                   >> 1109                           SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 1110                           "Parsing...");
                                                   >> 1111   syntax_tree = parse_expression(" -  ( (69/ toto)+ ( (( - +-- 1))) + --toto*((toto+ - - y - +2*(y-toto))*y) +2*(y-toto) )/- (( y - toto)*2)");
                                                   >> 1112 
                                                   >> 1113   if (syntax_tree != NULL)
                                                   >> 1114     {
                                                   >> 1115       sos_x86_videomem_printf(6, 0,
                                                   >> 1116                               SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 1117                               "Evaluating...");
                                                   >> 1118       sos_x86_videomem_printf(7, 0,
                                                   >> 1119                               SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 1120                               "Result=%d (if 0: check bochs output)",
                                                   >> 1121                               eval_expression(syntax_tree,
                                                   >> 1122                                               (const char*[]){"toto", "y"},
                                                   >> 1123                                               (int[]){3, 4},
                                                   >> 1124                                               2));
                                                   >> 1125       free_syntax_tree(syntax_tree);
                                                   >> 1126       sos_x86_videomem_printf(8, 0,
                                                   >> 1127                               SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 1128                               "Done (un-allocated syntax tree)");
                                                   >> 1129     }
                                                   >> 1130   else
                                                   >> 1131     {
                                                   >> 1132       sos_x86_videomem_printf(6, 0,
                                                   >> 1133                               SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_YELLOW,
                                                   >> 1134                               "Error in parsing (see bochs output)");
                                                   >> 1135     }
                                                   >> 1136 
                                                   >> 1137   /*
                                                   >> 1138    * Run some demand-paging tests
                                                   >> 1139    */
                                                   >> 1140   test_demand_paging(234567, 500);
                                                   >> 1141 
                                                   >> 1142 
                                                   >> 1143   /*
                                                   >> 1144    * Create an un-resolved page fault, which will make the page fault
                                                   >> 1145    * handler print the backtrace.
                                                   >> 1146    */
                                                   >> 1147   test_backtrace(6, 0xdeadbeef, bootstrap_stack_bottom, bootstrap_stack_size);
                                                   >> 1148 
                                                   >> 1149   /*
                                                   >> 1150    * System should be halted BEFORE here !
                                                   >> 1151    */
                                                   >> 1152 
063                                                   1153 
064   /* An operatig system never ends */             1154   /* An operatig system never ends */
065   for (;;)                                        1155   for (;;)
066     continue;                                  !! 1156     {
                                                   >> 1157       /* Remove this instruction if you get an "Invalid opcode" CPU
                                                   >> 1158          exception (old 80386 CPU) */
                                                   >> 1159       asm("hlt\n");
067                                                   1160 
068   return;                                      !! 1161       continue;
                                                   >> 1162     }
069 }                                                 1163 }
                                                      

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