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sortix--sortix/libc/x64/fork.S

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/*
* Copyright (c) 2012, 2014 Jonas 'Sortie' Termansen.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* x64/fork.S
* Assembly functions related to forking x64 processes.
*/
#define MSRID_FSBASE 0xC0000100
#define MSRID_GSBASE 0xC0000101
.section .text
.globl __sfork
.type __sfork, @function
__sfork:
pushq %rbp
movq %rsp, %rbp
pushq %rdi
pushq %rsi
movq $.Lafter_fork, (0 * 8)(%rsi) # rip
movq $0, (1 * 8)(%rsi) # rax, result is 0 for child
movq %rbx, (2 * 8)(%rsi)
movq %rcx, (3 * 8)(%rsi)
movq %rdx, (4 * 8)(%rsi)
movq %rdi, (5 * 8)(%rsi)
movq %rsi, (6 * 8)(%rsi)
movq %rsp, (7 * 8)(%rsi)
movq %rbp, (8 * 8)(%rsi)
movq %r8, (9 * 8)(%rsi)
movq %r9, (10 * 8)(%rsi)
movq %r10, (11 * 8)(%rsi)
movq %r11, (12 * 8)(%rsi)
movq %r12, (13 * 8)(%rsi)
movq %r13, (14 * 8)(%rsi)
movq %r14, (15 * 8)(%rsi)
movq %r15, (16 * 8)(%rsi)
pushfq
popq %rax
movq %rax, (17 * 8)(%rsi) # rflags
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movl $MSRID_FSBASE, %edi
call rdmsr
movq 0(%rsp), %rsi
movq %rax, (18 * 8)(%rsi) # fsbase
movl $MSRID_GSBASE, %edi
call rdmsr
movq 0(%rsp), %rsi
movq %rax, (19 * 8)(%rsi) # gsbase
movq 8(%rsp), %rdi
call tfork
.Lafter_fork:
# The value in %rax determines whether we are child or parent. There is no
# need to clean up the stack from the above pushes, leaveq sets %rsp to %rbp
# which does that for us.
leaveq
retq
.size __sfork, . - __sfork