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379cd77078
On Windows, mmap() now chooses addresses transactionally. It reduces the risk of badness when interacting with the WIN32 memory manager. We don't throw darts anymore. There is also no more retry limit, since we recover from mystery maps more gracefully. The subroutine for combining adjacent maps has been rewritten for clarity. The print maps subroutine is better This change goes to great lengths to perfect the stack overflow code. On Windows you can now longjmp() out of a crash signal handler. Guard pages previously weren't being restored properly by the signal handler. That's fixed, so on Windows you can now handle a stack overflow multiple times. Great thought has been put into selecting the perfect SIGSTKSZ constants so you can save sigaltstack() memory. You can now use kprintf() with 512 bytes of stack available. The guard pages beneath the main stack are now recorded in the memory manager. This change fixes getcontext() so it works right with the %rax register.
62 lines
3.6 KiB
C
62 lines
3.6 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/calls/struct/siginfo.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/getauxval.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sysv/consts/auxv.h"
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#include "libc/sysv/consts/ss.h"
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long __get_minsigstksz(void) {
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struct AuxiliaryValue av;
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av = __getauxval(AT_MINSIGSTKSZ);
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if (av.isfound) {
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long res = av.value;
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if (!IsLinux())
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res += sizeof(struct ucontext) + sizeof(struct siginfo) + 128;
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if (res < _MINSIGSTKSZ)
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res = _MINSIGSTKSZ;
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return res;
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} else {
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// _MINSIGSTKSZ takes these things into consideration:
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//
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// 1. The platform definition of MINSIGSTKSZ. This will probably be
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// enforced by the kernel when calling sys_sigaltstack(). On ARM
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// platforms this might be several kilobytes larger than x86. On
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// Linux they really want you to use AT_MINSIGSTKSZ instead. The
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// kernel should ideally set this to be the number of bytes that
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// get subtracted from the stack pointer when delivering signals
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// meaning that if you use this for a stack size your handler is
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// called successfully but if it uses the stack then it'll crash
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//
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// 2. Cosmo sigenter overhead. On non-Linux OSes the kernel calls a
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// trampoline in the libc runtime, which translates the platform
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// specific signal frame to the Linux memory layout. It means we
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// need to push ~1024 extra bytes on the stack to call a handler
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//
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// 3. Sanity testing. Assume we use sysconf(_SC_MINSIGSTKSZ) + 2048
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// as our stack size (see stackoverflow1_test.c). Then we should
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// have enough room to use kprintf() from our signal handler. If
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// that isn't the case, then this should be increased a bit more
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// noting that if 1024 is used then kprintf should print refusal
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//
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return _MINSIGSTKSZ;
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}
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}
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