ELFとか

$ more hello.c
#include 
int main(){
        puts("Hellom World!");
        return 0;
}

$ hd hello.o
00000000  7f 45 4c 46  01 01 01 00  00 00 00 00  00 00 00 00 |.ELF............|
00000010  01 00 03 00  01 00 00 00  00 00 00 00  00 00 00 00 |................|
00000020  fc 00 00 00  00 00 00 00  34 00 00 00  00 00 28 00 |........4.....(.|
00000030  0b 00 08 00  00 00 00 00  00 00 00 00  00 00 00 00 |................|
00000040  55 89 e5 83  ec 08 83 c4  f4 68 00 00  00 00 e8 fc |U........h......|
00000050  ff ff ff 83  c4 10 31 c0  eb 06 8d b6  00 00 00 00 |......1.........|
00000060  c9 c3 00 00  08 00 00 00  00 00 00 00  01 00 00 00 |................|
00000070  30 31 2e 30  31 00 00 00  48 65 6c 6c  6f 6d 20 57 |01.01...Hellom W|
00000080  6f 72 6c 64  21 00 00 47  43 43 3a 20  28 47 4e 55 |orld!..GCC: (GNU|
00000090  29 20 32 2e  39 35 2e 33  20 32 30 30  31 30 33 31 |) 2.95.3 2001031|
000000a0  35 20 28 72  65 6c 65 61  73 65 29 00  00 2e 73 79 |5 (release)...sy|
000000b0  6d 74 61 62  00 2e 73 74  72 74 61 62  00 2e 73 68 |mtab..strtab..sh|
000000c0  73 74 72 74  61 62 00 2e  74 65 78 74  00 2e 72 65 |strtab..text..re|
000000d0  6c 2e 74 65  78 74 00 2e  64 61 74 61  00 2e 62 73 |l.text..data..bs|
000000e0  73 00 2e 6e  6f 74 65 00  2e 72 6f 64  61 74 61 00 |s..note..rodata.|
000000f0  2e 63 6f 6d  6d 65 6e 74  00 00 00 00  00 00 00 00 |.comment........|
00000100  00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00 |................|

$ objdump -d hello.o

hello.o:     file format elf32-i386

Disassembly of section .text:

00000000 
:
   0:   55                      push   %ebp
   1:   89 e5                   mov    %esp,%ebp
   3:   83 ec 08                sub    $0x8,%esp
   6:   83 c4 f4                add    $0xfffffff4,%esp
   9:   68 00 00 00 00          push   $0x0
   e:   e8 fc ff ff ff          call   f 
  13:   83 c4 10                add    $0x10,%esp
  16:   31 c0                   xor    %eax,%eax
  18:   eb 06                   jmp    20 
  1a:   8d b6 00 00 00 00       lea    0x0(%esi),%esi
  20:   c9                      leave  
  21:   c3                      ret    

$ objdump -j .rodata -s hello.o

hello.o:     file format elf32-i386

Contents of section .rodata:
 0000 48656c6c 6f6d2057 6f726c64 2100      Hellom World!.  

$ objdump -h hello.o

hello.o:     file format elf32-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00000022  00000000  00000000  00000040  2**4
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  1 .data         00000000  00000000  00000000  00000064  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          00000000  00000000  00000000  00000064  2**2
                  ALLOC
  3 .note         00000014  00000000  00000000  00000064  2**0
                  CONTENTS, READONLY
  4 .rodata       0000000e  00000000  00000000  00000078  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  5 .comment      00000026  00000000  00000000  00000086  2**0
                  CONTENTS, READONLY

readelfが無いから、objdump -hを使わんと...