mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-02-24 14:59:03 +00:00
42a3bb729a
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
136 lines
5.1 KiB
C
136 lines
5.1 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2023 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/assert.h"
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#include "libc/atomic.h"
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#include "libc/calls/struct/rlimit.h"
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#include "libc/calls/struct/sigaction.h"
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#include "libc/calls/struct/sigaltstack.h"
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#include "libc/calls/struct/siginfo.h"
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#include "libc/calls/struct/ucontext.internal.h"
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#include "libc/calls/ucontext.h"
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#include "libc/dce.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/limits.h"
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#include "libc/mem/gc.h"
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#include "libc/mem/mem.h"
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#include "libc/runtime/runtime.h"
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#include "libc/runtime/sysconf.h"
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#include "libc/stdio/rand.h"
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#include "libc/stdio/stdio.h"
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#include "libc/stdio/sysparam.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/sysv/consts/prot.h"
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#include "libc/sysv/consts/rlimit.h"
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#include "libc/sysv/consts/sa.h"
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#include "libc/sysv/consts/sig.h"
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#include "libc/sysv/consts/ss.h"
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#include "libc/thread/thread.h"
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/**
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* stack overflow recovery technique #1
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* overflow the gigantic main process stack
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* simple but it can upset kernels / libraries
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*/
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jmp_buf recover;
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atomic_bool g_isdone;
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atomic_bool smashed_stack;
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void CrashHandler(int sig, siginfo_t *si, void *ctx) {
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struct sigaltstack ss;
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unassert(!sigaltstack(0, &ss));
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unassert(SS_ONSTACK == ss.ss_flags);
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kprintf("kprintf avoids overflowing %G si_addr=%lx sp=%lx\n", si->si_signo,
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si->si_addr, ((ucontext_t *)ctx)->uc_mcontext.SP);
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smashed_stack = true;
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// unassert(__is_stack_overflow(si, ctx)); // fuzzy with main thread
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longjmp(recover, 123);
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}
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void SetUp(void) {
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// tune down the main process's stack size to a reasonable amount
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// some operating systems, e.g. freebsd, will do things like have
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// 500mb RLIMIT_STACK by default, even on machines with 400mb RAM
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if (!IsWindows() && !IsXnu()) {
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struct rlimit rl;
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getrlimit(RLIMIT_STACK, &rl);
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rl.rlim_cur = MIN(rl.rlim_cur, 2 * 1024 * 1024);
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unassert(!setrlimit(RLIMIT_STACK, &rl));
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}
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// set up the signal handler and alternative stack
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struct sigaction sa;
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struct sigaltstack ss;
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ss.ss_flags = 0;
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ss.ss_size = sysconf(_SC_MINSIGSTKSZ) + 8192;
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ss.ss_sp = _mapanon(ss.ss_size);
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unassert(!sigaltstack(&ss, 0));
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sa.sa_flags = SA_SIGINFO | SA_ONSTACK; // <-- important
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sigemptyset(&sa.sa_mask);
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sa.sa_sigaction = CrashHandler;
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sigaction(SIGBUS, &sa, 0);
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sigaction(SIGSEGV, &sa, 0);
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}
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int StackOverflow(int d) {
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char A[8];
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for (int i = 0; i < sizeof(A); i++)
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A[i] = d + i;
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if (__veil("r", d))
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return StackOverflow(d + 1) + A[d % sizeof(A)];
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return 0;
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}
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void *innocent_thread(void *arg) {
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atomic_long dont_clobber_me_bro = 0;
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while (!g_isdone)
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unassert(!dont_clobber_me_bro);
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return 0;
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}
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int main() {
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// libc/intrin/stack.c is designed so that this thread's stack should
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// be allocated right beneath the main thread's stack. our goal is to
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// make sure overflowing the main stack won't clobber our poor thread
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pthread_t th;
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unassert(!pthread_create(&th, 0, innocent_thread, 0));
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SetUp();
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int jumpcode;
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if (!(jumpcode = setjmp(recover)))
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exit(StackOverflow(1));
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unassert(123 == jumpcode);
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unassert(smashed_stack);
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// join the thread
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g_isdone = true;
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unassert(!pthread_join(th, 0));
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// here's where longjmp() gets us into trouble
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struct sigaltstack ss;
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unassert(!sigaltstack(0, &ss));
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if (IsXnu() || IsNetbsd()) {
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unassert(SS_ONSTACK == ss.ss_flags); // wut
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} else {
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unassert(0 == ss.ss_flags);
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}
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}
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