mirror of
https://github.com/jart/cosmopolitan.git
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5005f2e446
This change reduces the .bss memory requirement for all executables by O(64kb). The brk system calls are now fully tested and figured out and might be useful for tiny programs that only target System Five.
63 lines
3.2 KiB
C
63 lines
3.2 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net 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/assert.h"
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#include "libc/atomic.h"
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#include "libc/calls/struct/sigaction.h"
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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/intrin/atomic.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/testlib/testlib.h"
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#include "third_party/xed/x86.h"
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static volatile _Thread_local int gotsignal;
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static void ContinueOnError(int sig, siginfo_t *si, void *vctx) {
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struct XedDecodedInst xedd;
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struct ucontext *ctx = vctx;
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xed_decoded_inst_zero_set_mode(&xedd, XED_MACHINE_MODE_LONG_64);
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xed_instruction_length_decode(&xedd, (void *)ctx->uc_mcontext.rip, 15);
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ctx->uc_mcontext.rip += xedd.length;
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gotsignal = sig;
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}
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/**
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* Returns true if byte at address `p` is readable.
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*
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* This function temporarily catches `SIGSEGV` and `SIGBUS` to recover
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* on error. It then attempts a volatile read and if it faults, then
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* this function shall return false. The value at `p` isn't considered.
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*/
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noasan bool testlib_memoryexists(const void *p) {
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volatile char c;
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const atomic_char *mem = p;
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struct sigaction old[2];
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struct sigaction sa = {
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.sa_sigaction = ContinueOnError,
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.sa_flags = SA_SIGINFO,
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};
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gotsignal = 0;
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_npassert(!sigaction(SIGSEGV, &sa, old + 0));
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_npassert(!sigaction(SIGBUS, &sa, old + 1));
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c = atomic_load(mem);
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_npassert(!sigaction(SIGBUS, old + 1, 0));
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_npassert(!sigaction(SIGSEGV, old + 0, 0));
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return !gotsignal;
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}
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