/* Copyright (C) 2004  The SOS Team
    Copyright (C) 1999  Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.
    
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
    
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
    USA. 
 */
 
 /* Include definitions of the multiboot standard */
 #include <bootstrap/multiboot.h>
 #include <hwcore/idt.h>
 #include <hwcore/gdt.h>
 #include <hwcore/irq.h>
 #include <hwcore/exception.h>
 #include <hwcore/i8254.h>
 #include <sos/klibc.h>
 #include <sos/assert.h>
 #include <drivers/x86_videomem.h>
 #include <drivers/bochs.h>
 
 
 /* Helper function to display each bits of a 32bits integer on the
    screen as dark or light carrets */
 static void display_bits(unsigned char row, unsigned char col,
                          unsigned char attribute,
                          sos_ui32_t integer)
 {
   int i;
   /* Scan each bit of the integer, MSb first */
   for (i = 31 ; i >= 0 ; i--)
     {
       /* Test if bit i of 'integer' is set */
       int bit_i = (integer & (1 << i));
       /* Ascii 219 => dark carret, Ascii 177 => light carret */
       unsigned char ascii_code = bit_i?219:177;
       sos_x86_videomem_putchar(row, col++,
                                attribute,
                                ascii_code);
     }
 }
 
 
 /* Clock IRQ handler */
 static void clk_it(int intid)
 {
   static sos_ui32_t clock_count = 0;
 
   display_bits(0, 48,
                SOS_X86_VIDEO_FG_LTGREEN | SOS_X86_VIDEO_BG_BLUE,
                clock_count);
   clock_count++;
 
 }
 
 /* Division by zero exception handler */
 static void divide_ex(int exid)
 {
   static sos_ui32_t div_count = 0;
   display_bits(0, 0,
                SOS_X86_VIDEO_FG_LTRED | SOS_X86_VIDEO_BG_BLUE,
                div_count);
   div_count++;
 }
 
 /* The C entry point of our operating system */
 void sos_main(unsigned long magic, unsigned long addr)
 {
   unsigned i;
 
   /* Grub sends us a structure, called multiboot_info_t with a lot of
      precious informations about the system, see the multiboot
      documentation for more information. */
   multiboot_info_t *mbi;
   mbi = (multiboot_info_t *) addr;
 
   /* Setup bochs and console, and clear the console */
   sos_bochs_setup();
 
   sos_x86_videomem_setup();
   sos_x86_videomem_cls(SOS_X86_VIDEO_BG_BLUE);
 
   /* Greetings from SOS */
   if (magic == MULTIBOOT_BOOTLOADER_MAGIC)
     /* Loaded with Grub */
     sos_x86_videomem_printf(1, 0,
                             SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
                             "Welcome From GRUB to %s%c RAM is %dMB (upper mem = 0x%x kB)",
                             "SOS", ',',
                             (unsigned)(mbi->mem_upper >> 10) + 1,
                             (unsigned)mbi->mem_upper);
   else
     /* Not loaded with grub */
     sos_x86_videomem_printf(1, 0,
                             SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
                             "Welcome to SOS");
 
   sos_bochs_putstring("Message in a bochs\n");
 
   /* Setup CPU segmentation and IRQ subsystem */
   sos_gdt_setup();
   sos_idt_setup();
 
   /* Setup SOS IRQs and exceptions subsystem */
   sos_exceptions_setup();
   sos_irq_setup();
 
   /* Configure the timer so as to raise the IRQ0 at a 100Hz rate */
   sos_i8254_set_frequency(100);
 
   /* Binding some HW interrupts and exceptions to software routines */
   sos_irq_set_routine(SOS_IRQ_TIMER,
                             clk_it);
   sos_exception_set_routine(SOS_EXCEPT_DIVIDE_ERROR,
                             divide_ex);
   /* Enabling the HW interrupts here, this will make the timer HW
      interrupt call our clk_it handler */
   asm volatile ("sti\n");
 
   /* Raise a rafale of 'division by 0' exceptions. All this code is
      not really needed (equivalent to a bare "i=1/0;"), except when
      compiling with -O3: "i=1/0;" is considered dead code with gcc
      -O3. */
   i = 10;
   while (1)
     {
       /* Stupid function call to fool gcc optimizations */
       sos_bochs_printf("i = 1 / %d...\n", i);
       i = 1 / i;
     }
 
   /* Will never print this since the "divide by zero" exception always
      returns to the faulting instruction (see Intel x86 doc vol 3,
      section 5.12), thus re-evaluating the "divide-by-zero" exprssion
      and raising the "divide by zero" exception again and again... */
   sos_x86_videomem_putstring(2, 0,
                              SOS_X86_VIDEO_FG_LTRED | SOS_X86_VIDEO_BG_BLUE,
                              "Invisible");
 
   return;
 }