The LXR Cross Referencer for SOS

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001 /* Copyright (C) 2005  David Decotigny
002    Copyright (C) 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 #include "segment.h"
020 
021 
022 /**
023  * @file swintr_wrappers.S
024  *
025  * The SOS low-level handlers for the software interrupts. Currently
026  * only 1 wrapper: that for the SOS syscalls.
027  */
028 .file "swintr_wrappers.S"
029 
030 .text
031 
032 /* The address of the real "C" syscall function */
033 .extern sos_do_syscall
034 
035 /** Update the kernel TSS in case we are switching to a thread in user
036         mode in order to come back into the correct kernel stack */
037 .extern sos_cpu_context_update_kernel_tss
038 
039 /* The address of the function to call to set back the user thread's
040    MMU configuration upon return to user context */
041 .extern sos_thread_prepare_syscall_switch_back
042 
043 .p2align 2, 0x90
044 .globl sos_syscall_wrapper
045 sos_syscall_wrapper:
046 .type sos_syscall_wrapper,@function
047  
048   /* Fake error code */
049   pushl $0
050   /* Backup the context */
051   pushl %ebp
052   movl %esp, %ebp
053  
054   pushl %edi
055   pushl %esi
056   pushl %edx
057   pushl %ecx
058   pushl %ebx
059   pushl %eax
060   subl  $2,%esp
061   pushw %ss
062   pushw %ds
063   pushw %es
064   pushw %fs
065   pushw %gs
066 
067   /* Set correct kernel segment descriptors' value */
068   movw $SOS_BUILD_SEGMENT_REG_VALUE(0, 0, SOS_SEG_KDATA), %di
069   pushw %di ; popw %ds
070   pushw %di ; popw %es
071   pushw %di ; popw %fs
072   pushw %di ; popw %gs
073 
074   /* Prepare the call to do_syscall */ 
075   pushl %esp /* user_ctxt */
076   pushl %eax /* syscall ID */
077 
078   call  sos_do_syscall
079   /* Unallocate the stack used by the
080      do_syscall arguments */
081   addl  $8, %esp
082 
083   /* store the do_syscall return value into interrupted context */
084   movl %eax, 12(%esp)
085 
086   /* Set the MMU configuration to that of the user thread's process */
087   pushl %esp /* user_ctxt */
088   call sos_thread_prepare_syscall_switch_back
089   addl  $4, %esp /* Unallocate the stack */
090 
091   /* Prepare kernel TSS because we are switching back to a user
092      thread: we make sure that we will come back into the kernel at a
093      correct stack location */
094   pushl %esp /* Pass the location of the context we are
095                 restoring to the function */
096   call sos_cpu_context_update_kernel_tss
097   addl $4, %esp
098 
099   /* Restore the user context */
100   popw  %gs
101   popw  %fs
102   popw  %es
103   popw  %ds
104   popw  %ss
105   addl  $2,%esp
106   popl  %eax /* This is the return value of do_syscall (see above) */
107   popl  %ebx
108   popl  %ecx
109   popl  %edx
110   popl  %esi
111   popl  %edi
112  
113   popl  %ebp
114   /* Remove fake error code */
115   addl $4, %esp
116   iret
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