matos/arch/x86/syscall_wrappers.S
2021-11-06 00:13:19 +01:00

92 lines
2.0 KiB
ArmAsm

#define ASM_SOURCE
#include "segment.h"
.file "syscall_wrappers.S"
.text
/* The address of the real "C" syscall function */
.extern syscallExecute
/** Update the kernel TSS in case we are switching to a thread in user
mode in order to come back into the correct kernel stack */
.extern cpu_context_update_kernel_tss
/* The address of the function to call to set back the user thread's
MMU configuration upon return to user context */
.extern threadPrepareSyscallSwitchBack
.p2align 2, 0x90
.globl syscallHandler
syscallHandler:
.type syscallHandler,@function
/* Fake error code */
pushl $0
/* Backup the context */
pushl %ebp
movl %esp, %ebp
pushl %eax
pushl %ecx
pushl %edx
pushl %ebx
pushl %esi
pushl %edi
subl $2,%esp
pushw %ss
pushw %ds
pushw %es
pushw %fs
pushw %gs
/* Set correct kernel segment descriptors' value */
movw $BUILD_SEGMENT_REG_VALUE(0, 0, SEG_KDATA), %di
pushw %di ; popw %ds
pushw %di ; popw %es
pushw %di ; popw %fs
pushw %di ; popw %gs
/* Prepare the call to do_syscall */
pushl %esp /* user_ctxt */
pushl %eax /* syscall ID */
call syscallExecute
/* Unallocate the stack used by the
do_syscall arguments */
addl $8, %esp
/* store the do_syscall return value into interrupted context */
movl %eax, 32(%esp)
/* Set the MMU configuration to that of the user thread's process */
pushl %esp /* user_ctxt */
call threadPrepareSyscallSwitchBack
addl $4, %esp /* Unallocate the stack */
/* Prepare kernel TSS because we are switching back to a user
thread: we make sure that we will come back into the kernel at a
correct stack location */
pushl %esp /* Pass the location of the context we are
restoring to the function */
call cpu_context_update_kernel_tss
addl $4, %esp
/* Restore the user context */
popw %gs
popw %fs
popw %es
popw %ds
popw %ss
addl $2,%esp
popl %edi
popl %esi
popl %ebx
popl %edx
popl %ecx
popl %eax
popl %ebp
/* Remove fake error code */
addl $4, %esp
iret