mirror of
https://github.com/jart/cosmopolitan.git
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e4584ace81
Imported functions are now aspected with a trampoline that blocks signals and changes the thread-local storage register. This means bigger more complicated libraries can now be imported even though the whole technique remains fundamentally unsafe.
57 lines
3.2 KiB
C
57 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 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 "ape/sections.internal.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/runtime/memtrack.internal.h"
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#include "libc/runtime/stack.h"
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#include "libc/thread/posixthread.internal.h"
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#include "libc/thread/tls.h"
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#include "libc/thread/tls2.internal.h"
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/**
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* Computes safer buffer size for alloca().
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*
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* @param want defines an upper limit on the return value
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* @param extraspace is how much stack caller needs that isn't buffer
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* @return number of bytes to use for your buffer, or negative if the
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* allocation would likely cause a stack overflow
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*/
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privileged long __get_safe_size(long want, long extraspace) {
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if (!__tls_enabled) return want;
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struct PosixThread *pt;
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struct CosmoTib *tib = __get_tls_privileged();
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if (!IsAutoFrame((uintptr_t)tib >> 16) &&
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!(__executable_start <= (const unsigned char *)tib &&
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(const unsigned char *)tib < _end)) {
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return want;
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}
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long bottom, sp = GetStackPointer();
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if ((char *)sp >= tib->tib_sigstack_addr &&
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(char *)sp <= tib->tib_sigstack_addr + tib->tib_sigstack_size) {
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bottom = (long)tib->tib_sigstack_addr;
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} else if ((pt = (struct PosixThread *)tib->tib_pthread) &&
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pt->pt_attr.__stacksize) {
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bottom = (long)pt->pt_attr.__stackaddr + pt->pt_attr.__guardsize;
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} else {
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return want;
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}
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long size = sp - bottom - extraspace;
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if (size > want) size = want;
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return size;
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}
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