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Make execve() linger when it can't spoof parent

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It's now possible to use execve() when the parent process isn't built by
cosmo. In such cases, the current process will kill all threads and then
linger around, waiting for the newly created process to die, and then we
propagate its exit code to the parent. This should help bazel and others

Allocating private anonymous memory is now 5x faster on Windows. This is
thanks to VirtualAlloc() which is faster than the file mapping APIs. The
fork() function also now goes 30% faster, since we are able to avoid the
VirtualProtect() calls on mappings in most cases now.

Fixes #1253
This commit is contained in:
Justine Tunney 2025-01-04 21:11:53 -08:00
parent c97a858470
commit 42a3bb729a
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40 changed files with 612 additions and 656 deletions
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58
libc/thread/isstackoverflow.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2023 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/struct/siginfo.h"
#include "libc/calls/struct/ucontext.internal.h"
#include "libc/calls/ucontext.h"
#include "libc/macros.h"
#include "libc/runtime/runtime.h"
#include "libc/sysv/consts/auxv.h"
#include "libc/sysv/consts/sig.h"
#include "libc/thread/thread.h"
/**
* Returns true if signal is caused by stack overflow.
*/
char __is_stack_overflow(siginfo_t *si, void *arg) {
// sanity check
ucontext_t *uc = arg;
if (!si || !uc)
return false;
if (si->si_signo != SIGSEGV && //
si->si_signo != SIGBUS)
return false;
// get stack information
pthread_attr_t attr;
if (pthread_getattr_np(pthread_self(), &attr))
return false;
size_t guardsize;
if (pthread_attr_getguardsize(&attr, &guardsize))
return false;
void *stackaddr;
size_t stacksize;
if (pthread_attr_getstack(&attr, &stackaddr, &stacksize))
return false;
// determine if faulting address is inside guard region
char *x = (char *)si->si_addr;
char *lo = (char *)stackaddr - guardsize;
char *hi = (char *)stackaddr;
return lo <= x && x < hi;
}