cosmopolitan/libc/runtime/piro.c

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
vi: set net ft=c ts=8 sts=2 sw=2 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
αcτµαlly pδrταblε εxεcµταblε § post-initialization read-only
*/
#include "libc/bits/safemacros.h"
#include "libc/bits/weaken.h"
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#include "libc/calls/calls.h"
#include "libc/runtime/internal.h"
#include "libc/runtime/runtime.h"
#include "libc/sysv/consts/prot.h"
#define getaddr(section) ((intptr_t)weakaddr(section))
static textstartup void _piro_protect(intptr_t start, intptr_t end, int prot) {
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ssize_t len = end - start;
if (len > 0 && start && start % PAGESIZE == 0 && len % PAGESIZE == 0) {
if (mprotect((void *)(unsigned long)start, len, prot) == -1) abort();
}
}
/**
* Protects memory initialized at startup.
* e.g. function hooks, unpacked data structures, etc.
*
* This is only performed for executables of nontrivial size. It won't
* break the build if the αpε linker script wasn't used. Test code is
* protected too, so we don't end up like Knight Capital.
*
* @param prot can have PROT_{NONE,READ,WRITE,EXEC}
* @see ape/ape.lds
* @see libc/_start.S
*/
textstartup void _piro(int prot) {
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if (getaddr("main") < getaddr("__test_start")) {
_piro_protect(getaddr("__test_start"), getaddr("__test_end"), PROT_NONE);
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}
_piro_protect(getaddr("__ro"), getaddr("_etext"), PROT_READ);
_piro_protect(getaddr("__piro_start"), getaddr("__piro_end"), prot);
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}