replace strings in ELF .rodata sections

tool/build/renamestr.c

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