|< Linux gnu as and ld 3 | Main | More related utilities 5 >| Site Index | Download |


 

 

 

 

MODULE 000-4

GCC, G++, GDB AND FRIENDS 4

 

 

 

 

 

 

 

 

My Training Period: xx hours   

 

 

 

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

Further related reading:

 

  1. Check the best selling C / C++, Networking, Linux and Open Source books at Amazon.com.

  2. Linux Socket programming tutorial.

  3. C, Buffer overflow and stack frame (construction and destruction).

  4. C, Compiler, Assembler and Linker.

 

 

 

|< Linux gnu as and ld 3 | Main | More related utilities 5 >| Site Index | Download |


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