/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│ │vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│ ╞══════════════════════════════════════════════════════════════════════════════╡ │ Copyright 2022 Justine Alexandra Roberts Tunney │ │ │ │ Permission to use, copy, modify, and/or distribute this software for │ │ any purpose with or without fee is hereby granted, provided that the │ │ above copyright notice and this permission notice appear in all copies. │ │ │ │ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │ │ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │ │ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │ │ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │ │ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │ │ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │ │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │ │ PERFORMANCE OF THIS SOFTWARE. │ ╚─────────────────────────────────────────────────────────────────────────────*/ #include "libc/calls/calls.h" #include "libc/dce.h" #include "libc/intrin/asan.internal.h" #include "libc/intrin/asancodes.h" #include "libc/runtime/memtrack.internal.h" #include "libc/runtime/runtime.h" #include "libc/runtime/stack.h" #include "libc/sysv/consts/map.h" #include "libc/sysv/consts/prot.h" static char *_stkbase; __attribute__((__constructor__)) static void init(void) { _stkbase = (char *)kFixedmapStart; } /** * Allocates stack. * * The size of your returned stack is always GetStackSize(). * * The bottom 4096 bytes of your stack can't be used, since it's always * reserved for a read-only guard page. With ASAN it'll be poisoned too. * * The top 16 bytes of a stack can't be used due to openbsd:stackbound * and those bytes are also poisoned under ASAN build modes. * * @return stack bottom address on success, or null w/ errrno */ void *_mapstack(void) { char *p; if ((p = mmap(_stkbase, GetStackSize(), PROT_READ | PROT_WRITE, MAP_STACK | MAP_ANONYMOUS | MAP_FIXED, -1, 0)) != MAP_FAILED) { if (IsAsan()) { __asan_poison(p + GetStackSize() - 16, 16, kAsanStackOverflow); __asan_poison(p, 4096, kAsanStackOverflow); } _stkbase += GetStackSize() * 4; return p; } else { return 0; } } /** * Frees stack. * * @param stk was allocated by _mapstack() */ int _freestack(void *stk) { return munmap(stk, GetStackSize()); }