cosmopolitan/libc/str/findembeddedape.c
2022-08-11 12:13:18 -07:00

50 lines
2.7 KiB
C

/*-*- 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 2021 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/intrin/bits.h"
#include "libc/log/libfatal.internal.h"
#include "libc/macros.internal.h"
#include "libc/str/str.h"
#define TRIES 8
/**
* Returns offset of binary embedded inside binary.
*
* This can be used to load zip assets from an executable that hasn't
* gone through the `objcopy -S -O binary` step. We make the assumption
* that an x86_64-pc-linux-gnu toolchain is being used. This routine
* would need to be changed to accommodate binaries built locally on
* Apple, FreeBSD, etc.
*
* @param p needs to be page aligned
* @param n is byte length of p
* @return base address of image or NULL if not found
*/
uint8_t *FindEmbeddedApe(const uint8_t *p, size_t n) {
size_t i;
uint64_t w;
n = MIN(n, TRIES * PAGESIZE);
for (i = 0; i + 8 <= n; i += PAGESIZE) {
w = READ64LE(p + i);
if (w == READ64LE("MZqFpD='") || w == READ64LE("\177ELF\2\1\1\11")) {
return (/*unconst*/ uint8_t *)(p + i);
}
}
return 0;
}