source: mainline/kernel/arch/amd64/src/context.S@ e98f1c3e

#
# Copyright (c) 2001-2004 Jakub Jermar
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# modification, are permitted provided that the following conditions
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#include <abi/asmtool.h>
#include <arch/context_struct.h>
#include <arch/vreg.h>

.text

## Save current CPU context
#
# Save CPU context to context_t variable
# pointed by the 1st argument. Returns 1 in EAX.
#
FUNCTION_BEGIN(context_save_arch)
        movq (%rsp), %rdx     # the caller's return %rip
        
        movq %rdx, CONTEXT_OFFSET_PC(%rdi)
        movq %rsp, CONTEXT_OFFSET_SP(%rdi)
        
        movq %rbx, CONTEXT_OFFSET_RBX(%rdi)
        movq %rbp, CONTEXT_OFFSET_RBP(%rdi)
        movq %r12, CONTEXT_OFFSET_R12(%rdi)
        movq %r13, CONTEXT_OFFSET_R13(%rdi)
        movq %r14, CONTEXT_OFFSET_R14(%rdi)
        movq %r15, CONTEXT_OFFSET_R15(%rdi)

        movq vreg_ptr, %rsi
        movq %fs:VREG_TP(%rsi), %rsi
        movq %rsi, CONTEXT_OFFSET_TP(%rdi)
        
        xorl %eax, %eax       # context_save returns 1
        incl %eax
        ret
FUNCTION_END(context_save_arch)


## Restore current CPU context
#
# Restore CPU context from context_t variable
# pointed by the 1st argument. Returns 0 in EAX.
#
FUNCTION_BEGIN(context_restore_arch)
        movq CONTEXT_OFFSET_R15(%rdi), %r15
        movq CONTEXT_OFFSET_R14(%rdi), %r14
        movq CONTEXT_OFFSET_R13(%rdi), %r13
        movq CONTEXT_OFFSET_R12(%rdi), %r12
        movq CONTEXT_OFFSET_RBP(%rdi), %rbp
        movq CONTEXT_OFFSET_RBX(%rdi), %rbx
        
        movq CONTEXT_OFFSET_SP(%rdi), %rsp
        
        movq CONTEXT_OFFSET_PC(%rdi), %rdx
        movq %rdx, (%rsp)
        
        movq CONTEXT_OFFSET_TP(%rdi), %rcx 
        movq vreg_ptr, %rsi
        movq %rcx, %fs:VREG_TP(%rsi)
        
        xorl %eax, %eax       # context_restore returns 0
        ret
FUNCTION_END(context_restore_arch)