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sortix--sortix/libc/x64/syscall.S

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/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2013, 2014.
This file is part of the Sortix C Library.
The Sortix C Library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
The Sortix C Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
x64/syscall.S
Function for performing system calls.
*******************************************************************************/
# x86_64 system call conventions:
# interrupt 128
# system call number: %rax
# parameters: %rdi, %rsi, %rdx, %rcx, %r8, %r9
# return value: %rax, %rdx
# return errno: %rcx
# clobbered: %rdi, %rsi, %r8, %r9, %r10, %r11
# preserved: %rbx, %rsp, %rbp, %r12, %r13, %r14, %r15
.global asm_syscall
asm_syscall: /* syscall num in %rax. */
push %rbp
mov %rsp, %rbp
int $0x80
test %ecx, %ecx
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jz 1f
mov %fs:0, %rsi
mov %ecx, errno@tpoff(%rsi)
1:
pop %rbp
ret
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.size asm_syscall, .-asm_syscall