cosmopolitan/libc/sysv/macros.h

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/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
2020-06-15 14:18:57 +00:00
vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#ifndef COSMOPOLITAN_LIBC_SYSV_MACROS_H_
#define COSMOPOLITAN_LIBC_SYSV_MACROS_H_
#ifdef __ASSEMBLER__
#include "libc/macros.inc"
/* clang-format off */
/**
* @fileoverview System Five jump slot generator.
*
* We need to pass a magic number to the SYSCALL instruction in %rax.
* That's only possible to do in C using asm() macro wrappers, like in
* Chromium's "System Call Support" library. This technique is simpler
* to implement, gains us object-level ABI compatibility, hookability,
* and the ability to support significantly more functions, without the
* risk of slowing down builds too much with complicated headers.
*/
.macro .scall name:req num:req kw1 kw2
.ifnb \kw2
.align 16
\name: movabs $\num,%rax
jmp *systemfive(%rip)
.else
\name: push %rbp
mov %rsp,%rbp
movabs $\num,%rax
.hookable
call *systemfive(%rip)
pop %rbp
ret
.endif
.endfn \name,\kw1,\kw2
.previous
.endm
/* clang-format on */
#endif /* __ASSEMBLER__ */
#endif /* COSMOPOLITAN_LIBC_SYSV_MACROS_H_ */