mirror of
https://github.com/jart/cosmopolitan.git
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148 lines
4.5 KiB
ArmAsm
148 lines
4.5 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│ vi: set noet ft=asm ts=8 sw=8 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/dce.h"
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#include "libc/intrin/strace.internal.h"
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#include "libc/thread/tls.h"
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#include "libc/macros.internal.h"
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// Forks process without copying page tables.
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//
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// This function lets a process spawn another process without
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// copying the page tables. The parent process gets suspended
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// until the child calls either execve() or _Exit(), and they
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// share memory during that time. That's at least how we want
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// vfork() to work. Support for these behaviors is patchy. It
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// is also error-prone to use this function in an environment
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// with signal handlers and threads. The best way to use this
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// is by calling posix_spawn() which works around the dangers
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// and determines at runtime the best way to pass error codes
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//
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// @return pid of child process or 0 if forked process
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// @returnstwice
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// @vforksafe
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.ftrace1
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vfork:
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.ftrace2
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#ifdef __SANITIZE_ADDRESS__
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jmp fork
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#endif
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#ifdef __x86_64__
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#if SupportsWindows()
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// these platforms disagree with vfork
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testb $_HOSTXNU|_HOSTOPENBSD|_HOSTWINDOWS,__hostos(%rip)
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jnz fork
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#endif
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#if !IsTiny()
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push %rbp
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mov %rsp,%rbp
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#if SYSDEBUG
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ezlea .Llog,di
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call __stracef
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#endif
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pop %rbp
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#endif
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mov %fs:0,%r9 // get thread information block
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mov 0x3c(%r9),%r8d // avoid question of @vforksafe errno
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pop %rsi // saves return address in a register
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mov __NR_vfork(%rip),%eax
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#if SupportsBsd()
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clc
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#endif
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syscall
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#if SupportsBsd()
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jnc 0f
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neg %rax
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0:
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#endif
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push %rsi // note it happens twice in same page
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cmp $-4095,%eax
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jae systemfive_error
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mov %r8d,0x3c(%r9) // restore errno
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1: test %eax,%eax
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jnz .Lpar
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.Lchi: orb $TIB_FLAG_VFORKED,0x40(%r9)
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ret
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.Lpar: andb $~TIB_FLAG_VFORKED,0x40(%r9)
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ret
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#elif defined(__aarch64__)
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adrp x8,__hostos
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ldr w8,[x8,#:lo12:__hostos]
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tbz x8,3,1f // bit 3 is xnu
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b fork // which doesn't support vfork()
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1:
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#if SYSDEBUG
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stp x29,x30,[sp,-16]!
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adrp x0,.Llog
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add x0,x0,:lo12:.Llog
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mov x29,sp
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bl __stracef
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ldp x29,x30,[sp],16
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#endif
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tbnz w8,5,1f // bit 5 is freebsd
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mov x8,#220 // clone (linux)
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mov x0,#0x4111 // SIGCHLD | CLONE_VM | CLONE_VFORK
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mov x1,#0
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svc 0
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b 2f
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1: mov x8,#66 // vfork (freebsd)
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svc 0 // call kernel
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bcc 2f // jump if not carry
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neg x0,x0 // linux style errno
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2:
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// if (!rc) {
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// __get_tls()->tib_flags |= TIB_FLAG_VFORKED;
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// } else {
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// __get_tls()->tib_flags &= ~TIB_FLAG_VFORKED;
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// }
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sub x1,x28,#192 // sizeof(CosmoTib)
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ldr x2,[x1,64]
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cbnz x0,2f
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orr x2,x2,#TIB_FLAG_VFORKED
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1: str x2,[x1,64]
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b 3f
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2: and x2,x2,#~TIB_FLAG_VFORKED
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b 1b
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// if (rc < 0) errno = -rc, rc = -1;
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3: .hidden _sysret
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b _sysret
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#else
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#error "architecture unsupported"
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#endif
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.endfn vfork,globl
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#if SYSDEBUG
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.rodata.str1.1
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.Llog: .ascii STRACE_PROLOGUE
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.asciz "vfork()\n"
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.previous
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#endif /* DEBUGSYS */
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