1. gcc 에서 컴파일된 결과 물인  *.o 도 elf 포맷인가요?

    예... 컴파일 된 오브젝트 파일도 elf 포맷입니다.

    다음과 같이  test.c 를 만든후 컴파일하고 readelf 를 이용하여 검토해 봅시다.
   
    # cat test.c
   
        #include <stdio.h>
       
        int count = 3;
       
        int test_function( int a )
        {
            int b;
            int c;
       
            b = a + 1;
            c = a * 4 >> 4;
       
           return b+c;
        }
        frog@eabi:tmp$    
   
   
    # gcc -c test.c

        frog@eabi:tmp$ readelf -a  test.o                                                  
        ELF Header:                                                                        
          Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00                     
          Class:                             ELF32                                     
          Data:                              2's complement, little endian             
          Version:                           1 (current)                               
          OS/ABI:                            UNIX - System V                           
          ABI Version:                       0                                         
          Type:                              REL (Relocatable file)                    
          Machine:                           Intel 80386                               
          Version:                           0x1                                       
          Entry point address:               0x0                                       
          Start of program headers:          0 (bytes into file)                       
          Start of section headers:          204 (bytes into file)                     
          Flags:                             0x0                                       
          Size of this header:               52 (bytes)                                
          Size of program headers:           0 (bytes)                                 
          Number of program headers:         0                                         
          Size of section headers:           40 (bytes)                                
          Number of section headers:         9                                         
          Section header string table index: 6                                         
                                                                                       
        Section Headers:                                                               
          [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
          [ 0]                   NULL            00000000 000000 000000 00      0   0  0
          [ 1] .text             PROGBITS        00000000 000034 000026 00  AX  0   0  4
          [ 2] .data             PROGBITS        00000000 00005c 000004 00  WA  0   0  4
          [ 3] .bss              NOBITS          00000000 000060 000000 00  WA  0   0  4
          [ 4] .comment          PROGBITS        00000000 000060 000024 01  MS  0   0  1
          [ 5] .note.GNU-stack   PROGBITS        00000000 000084 000000 00      0   0  1
          [ 6] .shstrtab         STRTAB          00000000 000084 000045 00      0   0  1
          [ 7] .symtab           SYMTAB          00000000 000234 000090 10      8   7  4
          [ 8] .strtab           STRTAB          00000000 0002c4 00001c 00      0   0  1
        Key to Flags:                                                                  
          W (write), A (alloc), X (execute), M (merge), S (strings)                    
          I (info), L (link order), G (group), x (unknown)                             
          O (extra OS processing required) o (OS specific), p (processor specific)     
                                                                                       
        There are no section groups in this file.                                      
                                                                                       
        There are no program headers in this file.                                     
                                                                                       
        There are no relocations in this file.                                         
                                                                                       
        There are no unwind sections in this file.                                     
                                                                                       
        Symbol table '.symtab' contains 9 entries:                                     
           Num:    Value  Size Type    Bind   Vis      Ndx Name                        
             0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND                             
             1: 00000000     0 FILE    LOCAL  DEFAULT  ABS test.c                      
             2: 00000000     0 SECTION LOCAL  DEFAULT    1                             
             3: 00000000     0 SECTION LOCAL  DEFAULT    2                             
             4: 00000000     0 SECTION LOCAL  DEFAULT    3                             
             5: 00000000     0 SECTION LOCAL  DEFAULT    5                             
             6: 00000000     0 SECTION LOCAL  DEFAULT    4                             
             7: 00000000     4 OBJECT  GLOBAL DEFAULT    2 count                       
             8: 00000000    38 FUNC    GLOBAL DEFAULT    1 test_function               
                                                                                       
        No version information found in this file.                                     
        frog@eabi:tmp$                                                                 
       

2. elf 포맷 파일을 다루는 라이브러리가 있을까요?

    우선 LibElf 는 다음 위치에 있습니다. BSD 라이센스라서 괜찮은 것 같습니다.
   
    다음 위치에 가면 찾을 수 있습니다.
   
            http://wiki.freebsd.org/LibElf
       

3. 괜찮은 자료

    기사 : (영문)
        http://developers.sun.com/solaris/articles/elf.html
   
    라이브러리 사용 예제    
        http://sourceforge.net/projects/elftoolchain/files/Documentation/libelf-by-example/