The nm - Listing Symbols From Object File

nm
GNU nm lists the symbols from object files objfile. If no object files are listed as arguments, nm assumes the file is a.out.
Usage: nm [option(s)] [file(s)] List symbols in [file(s)] (a.out by default).
The options are:
-a, --debug-syms	Display debugger-only symbols
-A, --print-file-name	Print name of the input file before every symbol
-B	Same as --format=bsd
-C, -- demangle[={none, auto, gnu,lucid,arm,hp,edg,gnu-v3,java,gnat,compaq}]	Decode low-level symbol names into user-level names
--no-demangle	Do not demangle low-level symbol names
--demangler=<dso:function>	Set dso and demangler function
-D, --dynamic	Display dynamic symbols instead of normal symbols
--defined-only	Display only defined symbols
-f, --format=FORMAT	Use the output format FORMAT. FORMAT can be 'bsd', 'sysv' or 'posix'. The default is 'bsd'
-g, --extern-only	Display only external symbols
-l, --line-numbers	Use debugging information to find a filename and line number for each symbol
-n, --numeric-sort	Sort symbols numerically by address
-o	Same as -A
-p, --no-sort	Do not sort the symbols
-P, --portability	Same as --format=posix
-r, --reverse-sort	Reverse the sense of the sort
-S, --print-size	Print size of defined symbols
-s, --print-armap	Include index for symbols from archive members
--size-sort	Sort symbols by size
--synthetic	Display synthetic symbols as well
-t, --radix=RADIX	Use RADIX for printing symbol values
--target=BFDNAME	Specify the target object format as BFDNAME
-u, --undefined-only	Display only undefined symbols
-h, --help	Display this information
-V, --version	Display this program's version number

Examples Using nm

[bodo@bakawali testbed5]$ ls -l

total 20

-rwxrwxr-x 1 bodo bodo 6403 Feb 19 11:35 testbuff

-rw-rw-r-- 1 bodo bodo 179 Feb 19 11:35 testbuff.c

[bodo@bakawali testbed5]$ cat testbuff.c

/* test buffer program */
#include <unistd.h>

void Test()
{
    char buff[4];
    printf("Some input: ");
    gets(buff);
    puts(buff);
}

int main(int argc, char *argv[ ])
{
    Test();
    return 0;
}

[bodo@bakawali testbed5]$ nm -t d -l -S -v testbuff

U gets@@GLIBC_2.0

w __gmon_start__

w _Jv_RegisterClasses

U __libc_start_main@@GLIBC_2.0

U printf@@GLIBC_2.0

U puts@@GLIBC_2.0

134513344 T _init

134513448 T _start

134513484 t call_gmon_start

134513520 t __do_global_dtors_aux

134513572 t frame_dummy

134513616 00000054 T Test /home/bodo/testbed5/testbuff.c:5

134513670 00000040 T main /home/bodo/testbed5/testbuff.c:13

134513712 00000082 T __libc_csu_init

134513796 00000066 T __libc_csu_fini

134513864 t __do_global_ctors_aux

134513900 T _fini

134513928 00000004 R _fp_hw

134513932 00000004 R _IO_stdin_used

134513952 r __FRAME_END__

134518052 d __CTOR_LIST__

134518052 A __fini_array_end

134518052 A __fini_array_start

134518052 A __init_array_end

134518052 A __init_array_start

134518052 A __preinit_array_end

134518052 A __preinit_array_start

134518056 d __CTOR_END__

134518060 d __DTOR_LIST__

134518064 d __DTOR_END__

134518068 d __JCR_END__

134518068 d __JCR_LIST__

134518072 D _DYNAMIC

134518276 D _GLOBAL_OFFSET_TABLE_

134518304 D __data_start

134518304 W data_start

134518308 D __dso_handle

134518312 d p.0

134518316 A __bss_start

134518316 00000001 b completed.1

134518316 A _edata

134518320 A _end

[bodo@bakawali testbed5]$

The objdump - Viewing Object File's Information

objdump
objdump will display information from object files. objdump displays information about one or more object files. The options control what particular information to display. This information is mostly useful to programmers who are working on the compilation tools, as opposed to programmers who just want their program to compile and work. objfile are the object files to be examined. When you specify archives, objdump shows information on each of the member object files.
Display information from object <file(s)>.
At least one of the following switches must be given:
-a, --archive-headers	Display archive header information
-f, --file-headers	Display the contents of the overall file header
-p, --private-headers	Display object format specific file header contents
-h, --[section-]headers	Display the contents of the section headers
-x, --all-headers	Display the contents of all headers
-d, --disassemble	Display assembler contents of executable sections
-D, --disassemble-all	Display assembler contents of all sections
-S, --source	Intermix source code with disassembly
-s, --full-contents	Display the full contents of all sections requested
-g, --debugging	Display debug information in object file
-e, --debugging-tags	Display debug information using ctags style
-G, --stabs	Display (in raw form) any STABS info in the file
-t, --syms	Display the contents of the symbol table(s)
-T, --dynamic-syms	Display the contents of the dynamic symbol table
-r, --reloc	Display the relocation entries in the file
-R, --dynamic-reloc	Display the dynamic relocation entries in the file
-v, --version	Display this program's version number
-i, --info	List object formats and architectures supported
-H, --help	Display this information
The following switches are optional:
-b, --target=BFDNAME		Specify the target object format as BFDNAME
-m, --architecture=MACHINE		Specify the target architecture as MACHINE
-j, --section=NAME		Only display information for section NAME
-M, --disassembler-options=OPT		Pass text OPT on to the disassembler
-EB --endian=big		Assume big endian format when disassembling
-EL --endian=little		Assume little endian format when disassembling
--file-start-context		Include context from start of file (with -S)
-I, --include=DIR		Add DIR to search list for source files
-l, --line-numbers		Include line numbers and filenames in output
-C, --demangle[={none,auto, gnu,lucid,arm,hp,edg,gnu-v3,java,gnat,compaq}]		Decode mangled/processed symbol names
--demangler=<dso:function>		Set dso and demangler function
-w, --wide		Format output for more than 80 columns
-z, --disassemble-zeroes		Do not skip blocks of zeroes when disassembling
--start-address=ADDR		Only process data whose address is >= ADDR
--stop-address=ADDR		Only process data whose address is <= ADDR
--prefix-addresses		Print complete address alongside disassembly
--[no-]show-raw-insn		Display hex alongside symbolic disassembly
--adjust-vma=OFFSET		Add OFFSET to all displayed section addresses

Examples Using objdump

[bodo@bakawali testbed5]$ objdump -d testbuff.o

testbuff.o: file format elf32-i386

Disassembly of section .text:

00000000 <Test>:

0: 55 push %ebp

1: 89 e5 mov %esp, %ebp

3: 83 ec 08 sub $0x8, %esp

6: 83 ec 0c sub $0xc, %esp

9: 68 00 00 00 00 push $0x0

e: e8 fc ff ff ff call f <Test+0xf>

13: 83 c4 10 add $0x10, %esp

16: 83 ec 0c sub $0xc, %esp

19: 8d 45 fc lea 0xfffffffc(%ebp), %eax

1c: 50 push %eax

1d: e8 fc ff ff ff call 1e <Test+0x1e>

22: 83 c4 10 add $0x10, %esp

25: 83 ec 0c sub $0xc, %esp

28: 8d 45 fc lea 0xfffffffc(%ebp), %eax

2b: 50 push %eax

2c: e8 fc ff ff ff call 2d <Test+0x2d>

31: 83 c4 10 add $0x10, %esp

34: c9 leave

35: c3 ret

00000036 <main>:

36: 55 push %ebp

37: 89 e5 mov %esp, %ebp

39: 83 ec 08 sub $0x8, %esp

3c: 83 e4 f0 and $0xfffffff0, %esp

3f: b8 00 00 00 00 mov $0x0, %eax

44: 83 c0 0f add $0xf, %eax

47: 83 c0 0f add $0xf, %eax

4a: c1 e8 04 shr $0x4, %eax

4d: c1 e0 04 shl $0x4, %eax

50: 29 c4 sub %eax, %esp

52: e8 fc ff ff ff call 53 <main+0x1d>

57: b8 00 00 00 00 mov $0x0, %eax

5c: c9 leave

5d: c3 ret

[bodo@bakawali testbed5]$

[bodo@bakawali testbed5]$ objdump -t testbuff.o

testbuff.o: file format elf32-i386

SYMBOL TABLE:

00000000 l df *ABS* 00000000 testbuff.c

00000000 l d .text 00000000

00000000 l d .data 00000000

00000000 l d .bss 00000000

00000000 l d .rodata 00000000

00000000 l d .note.GNU-stack 00000000

00000000 l d .comment 00000000

00000000 g F .text 00000036 Test

00000000 *UND* 00000000 printf

00000000 *UND* 00000000 gets

00000000 *UND* 00000000 puts

00000036 g F .text 00000028 main

[bodo@bakawali testbed5]$ objdump -r testbuff.o

testbuff.o: file format elf32-i386

RELOCATION RECORDS FOR [.text]:

OFFSET TYPE VALUE

0000000a R_386_32 .rodata

0000000f R_386_PC32 printf

0000001e R_386_PC32 gets

0000002d R_386_PC32 puts

00000053 R_386_PC32 Test

[bodo@bakawali testbed5]$ objdump -T testbuff

testbuff: file format elf32-i386

DYNAMIC SYMBOL TABLE:

00000000 DF *UND* 00000165 GLIBC_2.0 gets

00000000 DF *UND* 000001ab GLIBC_2.0 puts

00000000 DF *UND* 000000ef GLIBC_2.0 __libc_start_main

00000000 DF *UND* 00000036 GLIBC_2.0 printf

0804850c g DO .rodata 00000004 Base _IO_stdin_used

00000000 w D *UND* 00000000 _Jv_RegisterClasses

00000000 w D *UND* 00000000 __gmon_start__

bodo@bakawali testbed5]$ objdump -R testbuff

testbuff: file format elf32-i386

DYNAMIC RELOCATION RECORDS

OFFSET TYPE VALUE

08049600 R_386_GLOB_DAT __gmon_start__

08049610 R_386_JUMP_SLOT gets

08049614 R_386_JUMP_SLOT puts

08049618 R_386_JUMP_SLOT __libc_start_main

0804961c R_386_JUMP_SLOT printf

[bodo@bakawali testbed5]$ objdump -h testbuff

testbuff: file format elf32-i386

Sections:

Idx Name Size VMA LMA File off Algn

0 .interp 00000013 08048114 08048114 00000114 2**0

CONTENTS, ALLOC, LOAD, READONLY, DATA

1 .note.ABI-tag 00000020 08048128 08048128 00000128 2**2

CONTENTS, ALLOC, LOAD, READONLY, DATA

2 .hash 00000034 08048148 08048148 00000148 2**2

CONTENTS, ALLOC, LOAD, READONLY, DATA

3 .dynsym 00000080 0804817c 0804817c 0000017c 2**2

CONTENTS, ALLOC, LOAD, READONLY, DATA

4 .dynstr 0000006a 080481fc 080481fc 000001fc 2**0

CONTENTS, ALLOC, LOAD, READONLY, DATA

5 .gnu.version 00000010 08048266 08048266 00000266 2**1

CONTENTS, ALLOC, LOAD, READONLY, DATA

6 .gnu.version_r 00000020 08048278 08048278 00000278 2**2

CONTENTS, ALLOC, LOAD, READONLY, DATA

7 .rel.dyn 00000008 08048298 08048298 00000298 2**2

CONTENTS, ALLOC, LOAD, READONLY, DATA

8 .rel.plt 00000020 080482a0 080482a0 000002a0 2**2

CONTENTS, ALLOC, LOAD, READONLY, DATA

9 .init 00000017 080482c0 080482c0 000002c0 2**2

CONTENTS, ALLOC, LOAD, READONLY, CODE

10 .plt 00000050 080482d8 080482d8 000002d8 2**2

CONTENTS, ALLOC, LOAD, READONLY, CODE

11 .text 000001c4 08048328 08048328 00000328 2**2

CONTENTS, ALLOC, LOAD, READONLY, CODE

12 .fini 0000001a 080484ec 080484ec 000004ec 2**2

CONTENTS, ALLOC, LOAD, READONLY, CODE

13 .rodata 00000015 08048508 08048508 00000508 2**2

CONTENTS, ALLOC, LOAD, READONLY, DATA

14 .eh_frame 00000004 08048520 08048520 00000520 2**2

CONTENTS, ALLOC, LOAD, READONLY, DATA

15 .ctors 00000008 08049524 08049524 00000524 2**2

CONTENTS, ALLOC, LOAD, DATA

16 .dtors 00000008 0804952c 0804952c 0000052c 2**2

CONTENTS, ALLOC, LOAD, DATA

17 .jcr 00000004 08049534 08049534 00000534 2**2

CONTENTS, ALLOC, LOAD, DATA

18 .dynamic 000000c8 08049538 08049538 00000538 2**2

CONTENTS, ALLOC, LOAD, DATA

19 .got 00000004 08049600 08049600 00000600 2**2

CONTENTS, ALLOC, LOAD, DATA

20 .got.plt 0000001c 08049604 08049604 00000604 2**2

CONTENTS, ALLOC, LOAD, DATA

21 .data 0000000c 08049620 08049620 00000620 2**2

CONTENTS, ALLOC, LOAD, DATA

22 .bss 00000004 0804962c 0804962c 0000062c 2**2

ALLOC

23 .comment 00000126 00000000 00000000 0000062c 2**0

CONTENTS, READONLY

24 .debug_aranges 00000020 00000000 00000000 00000752 2**0

CONTENTS, READONLY, DEBUGGING

25 .debug_pubnames 00000024 00000000 00000000 00000772 2**0

CONTENTS, READONLY, DEBUGGING

26 .debug_info 000001de 00000000 00000000 00000796 2**0

CONTENTS, READONLY, DEBUGGING

27 .debug_abbrev 000000df 00000000 00000000 00000974 2**0

CONTENTS, READONLY, DEBUGGING

28 .debug_line 0000004c 00000000 00000000 00000a53 2**0

CONTENTS, READONLY, DEBUGGING

29 .debug_frame 00000048 00000000 00000000 00000aa0 2**2

CONTENTS, READONLY, DEBUGGING

30 .debug_str 0000000d 00000000 00000000 00000ae8 2**0

CONTENTS, READONLY, DEBUGGING

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MODULE 000-4

GCC, G++, GDB AND FRIENDS 4

The nm - Listing Symbols From Object File

nm

Examples Using nm

The objdump - Viewing Object File's Information

Examples Using objdump

Further related reading:

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C & Linux GNU Related Utilities: Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6