The LXR Cross Referencer for SOS

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001 /* Copyright (C) 2005  David Decotigny
002    Copyright (C) 2000-2004, The KOS team
003 
004    This program is free software; you can redistribute it and/or
005    modify it under the terms of the GNU General Public License
006    as published by the Free Software Foundation; either version 2
007    of the License, or (at your option) any later version.
008    
009    This program is distributed in the hope that it will be useful,
010    but WITHOUT ANY WARRANTY; without even the implied warranty of
011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
012    GNU General Public License for more details.
013    
014    You should have received a copy of the GNU General Public License
015    along with this program; if not, write to the Free Software
016    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
017    USA. 
018 */
019 #define ASM_SOURCE 1
020 
021 
022 #include "segment.h"
023         
024          
025 .file "cpu_context_switch.S"
026 
027 .text
028 
029 
030 /**
031  * C Function called by the routines below in order to tell the CPU
032  * where will be the kernel stack (needed by the interrupt handlers)
033  * when next_ctxt will come back into kernel mode.
034  *
035  * void sos_cpu_context_update_kernel_tss(struct sos_cpu_state *next_ctxt)
036  *
037  * @see end of cpu_context.c
038  */
039 .extern sos_cpu_context_update_kernel_tss
040 
041         
042 .globl sos_cpu_context_switch
043 .type sos_cpu_context_switch, @function
044 sos_cpu_context_switch:
045         // arg2= to_context    --    esp+64
046         // arg1= from_context  --    esp+60
047         // caller ip           --    esp+56
048   pushf              // (eflags)     esp+52
049   pushl %cs          // (cs)         esp+48
050   pushl $resume_pc   // (ip)         esp+44
051   pushl $0           // (error code) esp+40
052   pushl %ebp         //              esp+36
053   pushl %edi         //              esp+32
054   pushl %esi         //              esp+28
055   pushl %edx         //              esp+24
056   pushl %ecx         //              esp+20
057   pushl %ebx         //              esp+16
058   pushl %eax         //              esp+12
059   subl $2, %esp      // (alignment)  esp+10
060   pushw %ss          //              esp+8
061   pushw %ds          //              esp+6
062   pushw %es          //              esp+4
063   pushw %fs          //              esp+2
064   pushw %gs          //              esp
065 
066   /*
067    * Now that the original eax/ebx are stored, we can use them safely
068    */
069         
070   /* Store the address of the saved context */
071   movl  60(%esp), %ebx
072   movl  %esp, (%ebx)
073 
074   /* This is the proper context switch ! We change the stack here */
075   movl 64(%esp), %esp
076 
077   /* Prepare kernel TSS in case we are switching to a user thread: we
078      make sure that we will come back into the kernel at a correct
079      stack location */
080   pushl %esp /* Pass the location of the context we are
081                 restoring to the function */
082   call sos_cpu_context_update_kernel_tss
083   addl $4, %esp
084 
085   /* Restore the CPU context */
086   popw %gs
087   popw %fs
088   popw %es
089   popw %ds
090   popw %ss
091   addl $2,%esp
092   popl %eax
093   popl %ebx
094   popl %ecx
095   popl %edx
096   popl %esi
097   popl %edi
098   popl %ebp
099   addl $4, %esp /* Ignore "error code" */
100 
101   /* This restores the eflags, the cs and the eip registers */
102   iret /* equivalent to: popfl ; ret */
103 
104 resume_pc:
105         // Same context as that when sos_cpu_context_switch got called
106         // arg2= to_context    -- esp+8
107         // arg1= from_context  -- esp+4
108         // caller ip           -- esp
109   ret
110 
111 
112 
113 /* ------------------------- */
114 .globl sos_cpu_context_exit_to
115 .type sos_cpu_context_exit_to, @function
116 sos_cpu_context_exit_to:
117         // arg3= reclaiming_arg  -- esp+12
118         // arg2= reclaiming_func -- esp+8
119         // arg1= to_context      -- esp+4
120         // caller ip             -- esp
121 
122   /* Store the current SP in a temporary register */
123   movl %esp, %eax
124 
125   /* This is the proper context switch ! We change the stack here */
126   movl 4(%eax), %esp
127 
128   /* Call the reclaiming function (remember: the old frame address
129      is stored in eax) */
130   pushl 12(%eax)
131   call  *8(%eax)
132   addl  $4, %esp
133 
134   /* Prepare kernel TSS in case we are switching to a user thread: we
135      make sure that we will come back into the kernel at a correct
136      stack location */
137   pushl %esp /* Pass the location of the context we are
138                 restoring to the function */
139   call sos_cpu_context_update_kernel_tss
140   addl $4, %esp
141 
142   /* Restore the CPU context */
143   popw %gs
144   popw %fs
145   popw %es
146   popw %ds
147   popw %ss
148   addl $2,%esp
149   popl %eax
150   popl %ebx
151   popl %ecx
152   popl %edx
153   popl %esi
154   popl %edi
155   popl %ebp
156   addl $4, %esp /* Ignore "error code" */
157 
158   /* This restores the eflags, the cs and the eip registers */
159   iret /* equivalent to: popfl ; ret */
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