cosmopolitan/libc/calls/hefty/vfork.S
Justine Tunney db33973e0a Get fork() working on Windows
This is done without using Microsoft's internal APIs. MAP_PRIVATE
mappings are copied to the subprocess via a pipe, since Microsoft
doesn't want us to have proper COW pages. MAP_SHARED mappings are
remapped without needing to do any copying. Global variables need
copying along with the stack and the whole heap of anonymous mem.
This actually improves the reliability of the redbean http server
although one shouldn't expect 10k+ connections on a home computer
that isn't running software built to serve like Linux or FreeBSD.
2020-11-13 03:14:39 -08:00

50 lines
2.5 KiB
ArmAsm

/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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
*/
#include "libc/dce.h"
#include "libc/macros.h"
/ Forks process without copying page tables.
/
/ This is the same as fork() except it's optimized for the case
/ where the caller invokes exec() immediately afterwards.
/
/ @return pid of child process or 0 if forked process
/ @returnstwice
vfork: testb IsWindows()
jnz fork$nt
mov __NR_vfork(%rip),%eax
cmp $-1,%eax
je systemfive.enosys
pop %rsi
testb IsBsd()
jnz vfork.bsd
syscall
push %rsi
cmp $-4095,%rax
jae systemfive.error
ret
.endfn vfork,globl
vfork.bsd:
syscall
push %rsi
jc systemfive.errno
ret
.endfn vfork.bsd