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sortix--sortix/libc/x86/syscall.s

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/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2013.
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/>.
x86/syscall.s
Function for performing system calls.
*******************************************************************************/
# i386 system call conventions:
# interrupt 128
# system call number: %eax
# parameters: %ebx, %ecx, %edx, %edi, %esi
# return value: %eax, %edx
# return errno: %ecx
# clobbered: %ebx, %edi, %esi
# preserved: %ebp, %esp
.section .text
.global asm_syscall
asm_syscall: /* syscall num in %eax. */
push %ebp
mov %esp, %ebp
push %ebx
push %edi
push %esi
# 0 (%ebp) # saved_ebp
# 4 (%ebp) # return_eip
mov 8 (%ebp), %ebx # param_word1
mov 12(%ebp), %ecx # param_word2
mov 16(%ebp), %edx # param_word3
mov 20(%ebp), %edi # param_word4
mov 24(%ebp), %esi # param_word5
int $0x80
test %ecx, %ecx # ret_errno & ret_errno
jz 1f # if ( !(ret_errno & ret_errno) )
mov %eax, %ebx # preserve: ret_low
mov %edx, %edi # preserve: ret_high
mov %ecx, %esi # preserve: ret_errno
call get_errno_location # get_errno_location()
mov %esi, (%eax) # *get_errno_location() = ret_errno
mov %ebx, %eax # restore: ret_low
mov %edi, %edx # restore: ret_high
1:
pop %esi
pop %edi
pop %ebx
pop %ebp
ret
2013-05-22 16:06:18 -04:00
.size asm_syscall, .-asm_syscall