jos/kernel-stab-dump.c

   1 /*
   2  * stab-dump: Dump JOS kernel symbol table
   3  *
   4  * Stab format info at:
   5  * http://sources.redhat.com/gdb/onlinedocs/stabs_toc.html
   6  *
   7  * Luiz Fernando N. Capitulino
   8  * <lcapitulino@gmail.com
   9  */
  10
  11 #include <stdio.h>
  12 #include <stdint.h>
  13 #include <string.h>
  14 #include <unistd.h>
  15 #include <stdlib.h>
  16 #include <fcntl.h>
  17 #include <sys/types.h>
  18 #include <sys/stat.h>
  19 #include <sys/mman.h>
  20 #include <elf.h>
  21
  22 struct Stab {
  23         uint32_t n_strx;        // index into string table of name
  24         uint8_t n_type;         // type of symbol
  25         uint8_t n_other;        // misc info (usually empty)
  26         uint16_t n_desc;        // description field
  27         uintptr_t n_value;      // value of symbol
  28 };
  29
  30 int main(int argc, char *argv[])
  31 {
  32         int err, fd;
  33         char *stabstr;
  34         struct stat buf;
  35         Elf32_Ehdr *header;
  36         Elf32_Shdr *sh, *esh;
  37         struct Stab *stab, *estab;
  38
  39         if (argc != 2) {
  40                 printf("usage: %s < file >\n", argv[0]);
  41                 exit(1);
  42         }
  43
  44         fd = open(argv[1], O_RDONLY);
  45         if (fd < 0) {
  46                 perror("open()");
  47                 exit(1);
  48         }
  49
  50         memset(&buf, 0, sizeof(buf));
  51         err = fstat(fd, &buf);
  52         if (err) {
  53                 perror("fstat()");
  54                 exit(1);
  55         }
  56
  57         header = (Elf32_Ehdr *) mmap(NULL, buf.st_size, PROT_READ,
  58                                      MAP_PRIVATE, fd, 0);
  59         if (header == MAP_FAILED) {
  60                 perror("mmap()");
  61                 exit(1);
  62         }
  63         close(fd);
  64
  65         /*
  66          * Get .stabstr and .stab
  67          *
  68          * XXX: The code makes the following assumptions:
  69          *
  70          * 1 .stabstr is the first SHT_STRTAB section
  71          * 2 .stab section is the section that comes before .stabstr
  72          *
  73          * This looks like hardcoded info for me, since we're couting
  74          * on the format of our kernel binary image. But I don't know
  75          * how to make this right.
  76          */
  77         sh = (Elf32_Shdr *) ((void *) header + header->e_shoff);
  78         esh = sh + header->e_shnum;
  79         for (; sh < esh; sh++)
  80                 if (sh->sh_type == SHT_STRTAB) {
  81                         stabstr = (char *) ((void *) header + sh->sh_offset);
  82                         --sh;
  83                         break;
  84                 }
  85
  86         stab = (struct Stab *) ((void *) header + sh->sh_offset);
  87         estab = stab + sh->sh_size / sh->sh_entsize;
  88         for (; stab < estab; stab++)
  89                 if (stab->n_type == 0x24) {
  90                         char *p;
  91
  92                         printf("%#x ", stab->n_value);
  93
  94                         /* Stab format for functions is:
  95                          *
  96                          *     func_name:F(x,y)
  97                          *
  98                          * But we're only interested in func_name
  99                          */
 100                         for (p = stab->n_strx + stabstr; *p != ':'; p++)
 101                                 putchar(*p);
 102                         putchar('\n');
 103                 }
 104
 105         munmap(header, buf.st_size);
 106         return 0;
 107 }