src/runtime/elf.c

   1 #include <string.h>
   2 #include <fcntl.h>
   3 #include <unistd.h>
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <elf.h>
   7
   8 // Return the offset to a file section named 'lisp.core' if there is one
   9 off_t search_for_elf_core(int fd)
  10 {
  11     Elf64_Ehdr ehdr;
  12
  13     if (lseek(fd, 0, SEEK_SET) != 0 ||
  14         read(fd, &ehdr, sizeof ehdr) != sizeof ehdr) {
  15         fprintf(stderr, "failed to read elf header\n");
  16         return 0;
  17     }
  18     // Seek to and read the section header of the section header string table
  19     Elf64_Shdr shdr;
  20     off_t offset = ehdr.e_shoff + ehdr.e_shstrndx * ehdr.e_shentsize;
  21     if (lseek(fd, offset, SEEK_SET) != offset ||
  22         read(fd, &shdr, sizeof shdr) != sizeof shdr) {
  23         fprintf(stderr, "read failed\n");
  24         return 0;
  25     }
  26     // Scan the section header string table
  27     unsigned long result = 0;
  28     char * shstrtab_strbuf = 0;
  29     int i;
  30     if ((shstrtab_strbuf = malloc(shdr.sh_size)) == NULL ||
  31         lseek(fd, shdr.sh_offset, SEEK_SET) != (Elf64_Sxword)shdr.sh_offset ||
  32         read(fd, shstrtab_strbuf, shdr.sh_size) != (Elf64_Sxword)shdr.sh_size ||
  33         lseek(fd, ehdr.e_shoff, SEEK_SET) != (Elf64_Sxword)ehdr.e_shoff)
  34         fprintf(stderr, "read failed\n");
  35     else for(i=0;i<ehdr.e_shnum;++i)
  36         if (read(fd, &shdr, sizeof shdr) == sizeof shdr
  37             && !strcmp(&shstrtab_strbuf[shdr.sh_name], "lisp.core")) {
  38             result = shdr.sh_offset;
  39             break;
  40         }
  41     if (shstrtab_strbuf)
  42         free(shstrtab_strbuf);
  43     return result;
  44 }