uclibc-ng/libc/sysdeps/linux/x86_64/syscall.S

/* Copyright (C) 2001, 2003 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU 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 2.1 of the License, or (at your option) any later version.

   The GNU 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 GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

/* Please consult the file sysdeps/unix/sysv/linux/x86-64/sysdep.h for
   more information about the value -4095 used below.  */

/* Usage: long syscall (syscall_number, arg1, arg2, arg3, arg4, arg5, arg6)
   We need to do some arg shifting, the syscall_number will be in
   rax.  */

.text
.globl syscall
.type	syscall,%function
.align 16
syscall:
	movq %rdi, %rax		/* Syscall number -> rax.  */
	movq %rsi, %rdi		/* shift arg1 - arg5.  */
	movq %rdx, %rsi
	movq %rcx, %rdx
	movq %r8, %r10
	movq %r9, %r8
	movq 8(%rsp),%r9	/* arg6 is on the stack.  */
	syscall			/* Do the system call.  */
	cmpq $-4095, %rax	/* Check %rax for error.  */
	jae __error		/* Branch forward if it failed.  */
	ret			/* Return to caller.  */

__error:
	jmp __syscall_error

.size syscall,.-syscall