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Make tool for replacing ELF strings (#1344)
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Gautham
GitHub
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283
tool/build/renamestr.c
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283
tool/build/renamestr.c
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2024 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/calls/calls.h"
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#include "libc/elf/def.h"
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#include "libc/elf/elf.h"
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#include "libc/elf/scalar.h"
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#include "libc/elf/struct/ehdr.h"
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#include "libc/elf/struct/phdr.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/intrin/likely.h"
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#include "libc/macros.h"
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#include "libc/mem/mem.h"
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#include "libc/runtime/runtime.h"
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#include "libc/runtime/symbols.internal.h"
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#include "libc/stdio/stdio.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/sysv/consts/o.h"
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#include "libc/sysv/consts/prot.h"
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#include "third_party/getopt/getopt.internal.h"
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#define VERSION \
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"renamestr v0.1\n" \
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"https://github.com/jart/cosmopolitan\n"
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#define MANUAL \
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" -f FROM -t TO INPUT \n" \
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"\n" \
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"DESCRIPTION\n" \
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"\n" \
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" in-place string replacement in ELF binary .rodata\n" \
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"\n" \
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" this program may be used to replace strings in the\n" \
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" .rodata sections of ELF binaries, in-place.\n" \
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"\n" \
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"FLAGS\n" \
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"\n" \
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" -h show usage\n" \
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"\n" \
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" -v show version\n" \
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"\n" \
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" -f FROM source string to replace\n" \
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"\n" \
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" -t TO target string replacement. must be shorter\n" \
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" than FROM string for replacement to work\n" \
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"\n" \
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" INPUT ELF binary containing strings to replace\n" \
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"\n"
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static const char *prog;
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static const char *exepath;
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static Elf64_Shdr *rodata;
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static char *rostart;
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static char *roend;
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static int exefd;
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static wontreturn void Die(const char *thing, const char *reason) {
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tinyprint(2, thing, ": ", reason, "\n", NULL);
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exit(1);
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}
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static wontreturn void DieSys(const char *thing) {
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perror(thing);
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exit(1);
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}
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static wontreturn void ShowUsage(int rc, int fd) {
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tinyprint(fd, "USAGE\n\n ", prog, MANUAL, NULL);
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exit(rc);
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}
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static void Pwrite(const void *data, size_t size, uint64_t offset) {
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ssize_t rc;
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const char *p, *e;
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for (p = data, e = p + size; p < e; p += (size_t)rc, offset += (size_t)rc) {
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if ((rc = pwrite(exefd, p, e - p, offset)) == -1) {
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DieSys(exepath);
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}
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}
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}
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struct String {
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const char *str;
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size_t len;
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};
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struct Param {
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struct String from;
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struct String to;
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int count;
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char *roloc;
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};
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struct Params {
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int n;
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struct Param p[4];
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};
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static struct Params params;
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static void GetOpts(int argc, char *argv[]) {
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int opt;
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bool partial = false;
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params.n = 0;
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struct Param *param;
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while ((opt = getopt(argc, argv, "hvf:t:")) != -1) {
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if (params.n >= ARRAYLEN(params.p)) {
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param = NULL;
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} else {
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param = &(params.p[params.n]);
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}
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switch (opt) {
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case 'f':
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if (!param) {
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Die(prog, "too many replacements provided");
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}
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if (param->from.str) {
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Die(prog, "from string already provided");
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}
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param->from.str = optarg;
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param->from.len = strlen(optarg);
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partial = !partial;
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break;
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case 't':
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if (!param) {
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Die(prog, "too many replacements provided");
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}
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if (param->to.str) {
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Die(prog, "to string already provided");
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}
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param->to.str = optarg;
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param->to.len = strlen(optarg);
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partial = !partial;
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break;
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case 'v':
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tinyprint(0, VERSION, NULL);
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exit(0);
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case 'h':
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ShowUsage(0, 1);
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default:
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ShowUsage(1, 2);
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}
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if (param->from.str && param->to.str) {
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if (param->from.len < param->to.len) {
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Die(prog, "to.str longer than from.str, cannot replace");
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}
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params.n++;
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}
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}
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if (params.n == 0) {
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Die(prog, "no replacements provided");
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}
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if (partial) {
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Die(prog, "partial replacement provided");
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}
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if (optind == argc) {
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Die(prog, "missing input argument");
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}
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if (optind != argc - 1) {
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Die(prog, "too many args");
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}
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exepath = argv[optind];
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}
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struct Input {
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union {
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char *map;
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Elf64_Ehdr *elf;
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unsigned char *umap;
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};
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size_t size;
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const char *path;
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};
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static struct Input input;
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static void OpenInput(const char *path) {
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int fd;
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if ((fd = open(path, O_RDWR)) == -1)
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DieSys(path);
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if ((input.size = lseek(fd, 0, SEEK_END)) == -1)
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DieSys(path);
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input.path = path;
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input.map = mmap(0, input.size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
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if (input.map == MAP_FAILED)
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DieSys(path);
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if (!IsElf64Binary(input.elf, input.size))
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Die(path, "not an elf64 binary");
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exefd = fd;
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}
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static void ReplaceString(struct Param *param) {
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size_t len;
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char *x = (char *)memchr(param->roloc, 0, roend - param->roloc);
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memmove(param->roloc, param->to.str, param->to.len);
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if (UNLIKELY(x == NULL)) {
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len = roend - param->roloc;
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memmove(param->roloc + param->to.len, param->roloc + param->from.len,
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len - param->from.len);
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} else {
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len = x - param->roloc;
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memmove(param->roloc + param->to.len, param->roloc + param->from.len,
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len + 1 - param->from.len);
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}
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param->roloc += param->to.len;
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}
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int main(int argc, char *argv[]) {
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#ifdef MODE_DBG
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ShowCrashReports();
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#endif
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prog = argv[0];
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if (!prog)
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prog = "renamestr";
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GetOpts(argc, argv);
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OpenInput(exepath);
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rodata = FindElfSectionByName(
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input.elf, input.size,
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GetElfSectionNameStringTable(input.elf, input.size), ".rodata");
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if (!rodata)
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Die(exepath, "doesn't have .rodata");
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rostart = GetElfSectionAddress(input.elf, input.size, rodata);
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if (!rostart)
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Die(prog, "could not get to start of .rodata");
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roend = rostart + rodata->sh_size;
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#ifdef MODE_DBG
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kprintf("elf file to process: %s\n", exepath);
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kprintf("file size is %ld\n", input.size);
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#endif
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for (int i = 0; i < params.n; ++i) {
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struct Param *param = &(params.p[i]);
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param->roloc = rostart;
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param->count = 0;
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#ifdef MODE_DBG
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kprintf("need to replace '%s' with '%s'\n", param->from.str, param->to.str);
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#endif
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}
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#define NEXT_ROLOC(z) \
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memmem((z)->roloc, roend - (z)->roloc, (z)->from.str, (z)->from.len)
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for (int i = 0; i < params.n; ++i) {
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struct Param *param = &(params.p[i]);
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for (param->roloc = NEXT_ROLOC(param); param->roloc != NULL;
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param->roloc = NEXT_ROLOC(param)) {
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ReplaceString(param);
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param->count++;
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}
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}
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#undef NEXT_ROLOC
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Pwrite(input.map, input.size, 0);
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if (close(exefd)) {
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Die(prog, "unable to close file after writing");
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}
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for (int i = 0; i < params.n; ++i) {
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struct Param *param = &(params.p[i]);
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printf("'%s' -> '%s': %d replacements\n", param->from.str, param->to.str,
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param->count);
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}
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return 0;
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}
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