mirror of
https://github.com/jart/cosmopolitan.git
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78 lines
4.2 KiB
C
78 lines
4.2 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 2022 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/errno.h"
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#include "libc/limits.h"
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#include "libc/runtime/runtime.h"
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#include "libc/thread/thread.h"
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/**
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* Defines size of cosmo-owned signal stack for thread.
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*
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* The sigaltstack() function is useful for writing robust programs that
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* can recover from the occasional thread having a stack overflow rather
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* than having the entire process crash. To use it normally, sigaltstack
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* needs to be called at the start of each thread with a unique piece of
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* memory. However this is challenging to do *correctly* without support
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* from the POSIX threads runtime, since canceled or crashed threads may
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* need to execute on the signal stack during pthread_exit() which would
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* prevent a thread-local storage key destructor from free()'ing it.
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*
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* By default pthread_create() will not install a sigaltstack() on newly
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* created threads. If this function is called, on the attributes object
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* that gets passed to pthread_create(), then it'll use malloc() to make
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* a stack for the thread using the size you specify here. The threading
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* runtime will also free that memory safely after complete termination.
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*
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* pthread_t id;
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* pthread_attr_t attr;
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* pthread_attr_init(&attr);
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* pthread_attr_setguardsize(&attr, getpagesize());
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* pthread_attr_setsigaltstacksize_np(&attr, stacksize);
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* pthread_create(&id, &attr, func, 0);
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* pthread_attr_destroy(&attr);
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* pthread_join(id, 0);
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*
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* Try using a size of `sysconf(_SC_SIGSTKSZ)`. If you want the smallest
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* size possible, then `sysconf(_SC_MINSIGSTKSZ) + 2048` is probably the
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* smallest value that can reasonably expected to work with pthread_exit
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*
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* struct sigaction sa;
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* sigemptyset(&sa.sa_mask);
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* sa.sa_flags = SA_SIGINFO | SA_ONSTACK;
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* sa.sa_sigaction = on_crash_signal;
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* sigaction(SIGSEGV, &sa, 0);
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*
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* Please note that in order for this to work, your handlers for signals
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* such as SIGSEGV and SIGBUS need to use SA_ONSTACK in your sa_flags.
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*
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* @param stacksize contains stack size in bytes, or 0 to disable
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* @return 0 on success, or errno on error
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* @raise EINVAL if `stacksize` is less than `sysconf(_SC_MINSIGSTKSZ)`
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*/
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errno_t pthread_attr_setsigaltstacksize_np(pthread_attr_t *a,
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size_t stacksize) {
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if (stacksize) {
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if (stacksize > INT_MAX)
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return EINVAL;
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if (stacksize < __get_minsigstksz())
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return EINVAL;
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}
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a->__sigaltstacksize = stacksize;
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return 0;
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}
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