2021-10-25 23:25:31 +02:00
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#define ASM_SOURCE
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#include "segment.h"
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.file "syscall_wrappers.S"
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.text
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/* The address of the real "C" syscall function */
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.extern syscall_execute
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/** Update the kernel TSS in case we are switching to a thread in user
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mode in order to come back into the correct kernel stack */
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.extern cpu_context_update_kernel_tss
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/* The address of the function to call to set back the user thread's
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MMU configuration upon return to user context */
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2021-10-30 13:58:12 +02:00
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.extern threadPrepareSyscallSwitchBack
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2021-10-25 23:25:31 +02:00
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.p2align 2, 0x90
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.globl syscallHandler
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syscallHandler:
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.type syscallHandler,@function
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/* Fake error code */
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pushl $0
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/* Backup the context */
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pushl %ebp
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movl %esp, %ebp
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pushl %eax
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pushl %ecx
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pushl %edx
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pushl %ebx
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pushl %esi
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pushl %edi
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subl $2,%esp
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pushw %ss
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pushw %ds
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pushw %es
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pushw %fs
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pushw %gs
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/* Set correct kernel segment descriptors' value */
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movw $BUILD_SEGMENT_REG_VALUE(0, 0, SEG_KDATA), %di
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pushw %di ; popw %ds
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pushw %di ; popw %es
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pushw %di ; popw %fs
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pushw %di ; popw %gs
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/* Prepare the call to do_syscall */
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pushl %esp /* user_ctxt */
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pushl %eax /* syscall ID */
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call syscall_execute
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/* Unallocate the stack used by the
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do_syscall arguments */
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addl $8, %esp
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/* store the do_syscall return value into interrupted context */
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movl %eax, 12(%esp)
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/* Set the MMU configuration to that of the user thread's process */
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pushl %esp /* user_ctxt */
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2021-10-30 13:58:12 +02:00
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call threadPrepareSyscallSwitchBack
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2021-10-25 23:25:31 +02:00
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addl $4, %esp /* Unallocate the stack */
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/* Prepare kernel TSS because we are switching back to a user
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thread: we make sure that we will come back into the kernel at a
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correct stack location */
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pushl %esp /* Pass the location of the context we are
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restoring to the function */
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call cpu_context_update_kernel_tss
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addl $4, %esp
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/* Restore the user context */
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popw %gs
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popw %fs
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popw %es
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popw %ds
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popw %ss
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addl $2,%esp
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popl %edi
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popl %esi
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popl %ebx
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popl %edx
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popl %ecx
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popl %eax
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popl %ebp
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/* Remove fake error code */
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addl $4, %esp
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iret
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