What is objdump?
5 objdump examples
Syntax and Options
Related Commands
What is objdump?
The Linux objdump command is used to display various types of information stored in object files. This command is mostly used while debugging or by the developers who are working on compilation tools.
5 objdump Examples
1. Display file header using -f option
Output consisting of only the file header (ELF header) can be displayed using -f option with this command.
Consider the following example :
$ objdump -f assert assert: file format elf64-x86-64 architecture: i386:x86-64, flags 0x00000112: EXEC_P, HAS_SYMS, D_PAGED start address 0x0000000000400620
So we see that the file header was produced in the output.
2. Display information related to all the sections using -s option
An object file may consist of various sections. To retrieve information related to all the sections, supply the -s option along with this command.
Consider the following example :
$ objdump -s assert assert: file format elf64-x86-64 Contents of section .interp: 400238 2f6c6962 36342f6c 642d6c69 6e75782d /lib64/ld-linux- 400248 7838362d 36342e73 6f2e3200 x86-64.so.2. Contents of section .note.ABI-tag: 400254 04000000 10000000 01000000 474e5500 ............GNU. 400264 00000000 02000000 06000000 0f000000 ................ Contents of section .note.gnu.build-id: 400274 04000000 14000000 03000000 474e5500 ............GNU. 400284 80100856 ae7aa679 536a6d82 8401e8cc ...V.z.ySjm..... 400294 7e6019d6 ~`.. Contents of section .hash: 400298 03000000 0a000000 09000000 08000000 ................ 4002a8 05000000 00000000 00000000 00000000 ................ 4002b8 00000000 03000000 01000000 02000000 ................ 4002c8 06000000 07000000 04000000 ............ Contents of section .gnu.hash: 4002d8 01000000 01000000 01000000 00000000 ................ 4002e8 00000000 00000000 00000000 ... ... ...
So we see that information related to all the sections was produced in the output.
3. Display a particular section using -j option
If we want that the output should consist only of a particular section. Then this can be done using the -j option along with this command.
Consider the following example :
$ objdump -s -j.interp assert assert: file format elf64-x86-64 Contents of section .interp: 400238 2f6c6962 36342f6c 642d6c69 6e75782d /lib64/ld-linux- 400248 7838362d 36342e73 6f2e3200 x86-64.so.2.
So we see that details related to the section .interp was produced in the output.
4. Accept the options from file by using @ option
Rather than supplying options through command line, a file can be used to supply options to the objdump command.
Consider the following example :
$ cat options.txt -s -j.interp assert $ objdump @options.txt assert: file format elf64-x86-64. Contents of section .interp: 400238 2f6c6962 36342f6c 642d6c69 6e75782d /lib64/ld-linux- 400248 7838362d 36342e73 6f2e3200 x86-64.so.2.
So we see that objdump command successfully accepted the options from a file and produced a relevant output.
5. Display all the header information using -x option
Information related to all the headers can be retrieved using -x option along with this command.
Consider the following example :
$ objdump -x assert
assert: file format elf64-x86-64
assert
architecture: i386:x86-64, flags 0x00000112:
EXEC_P, HAS_SYMS, D_PAGED
start address 0x0000000000400620
Program Header:
PHDR off 0x0000000000000040 vaddr 0x0000000000400040 paddr 0x0000000000400040 align 2**3
filesz 0x00000000000001f8 memsz 0x00000000000001f8 flags r-x
INTERP off 0x0000000000000238 vaddr 0x0000000000400238 paddr 0x0000000000400238 align 2**0
filesz 0x000000000000001c memsz 0x000000000000001c flags r--
LOAD off 0x0000000000000000 vaddr 0x0000000000400000 paddr 0x0000000000400000 align 2**21
filesz 0x00000000000009d4 memsz 0x00000000000009d4 flags r-x
LOAD off 0x0000000000000e18 vaddr 0x0000000000600e18 paddr 0x0000000000600e18 align 2**21
filesz 0x0000000000000238 memsz 0x0000000000000248 flags rw-
DYNAMIC off 0x0000000000000e40 vaddr 0x0000000000600e40 paddr 0x0000000000600e40 align 2**3
filesz 0x00000000000001a0 memsz 0x00000000000001a0 flags rw-
NOTE off 0x0000000000000254 vaddr 0x0000000000400254 paddr 0x0000000000400254 align 2**2
filesz 0x0000000000000044 memsz 0x0000000000000044 flags r--
EH_FRAME off 0x0000000000000930 vaddr 0x0000000000400930 paddr 0x0000000000400930 align 2**2
filesz 0x0000000000000024 memsz 0x0000000000000024 flags r--
STACK off 0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**3
filesz 0x0000000000000000 memsz 0x0000000000000000 flags rw-
RELRO off 0x0000000000000e18 vaddr 0x0000000000600e18 paddr 0x0000000000600e18 align 2**0
filesz 0x00000000000001e8 memsz 0x00000000000001e8 flags r--
Dynamic Section:
NEEDED libc.so.6
INIT 0x0000000000400578
FINI 0x00000000004008b8
HASH 0x0000000000400298
GNU_HASH 0x00000000004002d8
STRTAB 0x00000000004003e8
SYMTAB 0x00000000004002f8
STRSZ 0x000000000000007e
SYMENT 0x0000000000000018
DEBUG 0x0000000000000000
PLTGOT 0x0000000000600fe8
PLTRELSZ 0x00000000000000c0
PLTREL 0x0000000000000007
JMPREL 0x00000000004004b8
RELA 0x00000000004004a0
RELASZ 0x0000000000000018
RELAENT 0x0000000000000018
VERNEED 0x0000000000400480
VERNEEDNUM 0x0000000000000001
VERSYM 0x0000000000400466
Version References:
required from libc.so.6:
0x09691a75 0x00 02 GLIBC_2.2.5
Sections:
Idx Name Size VMA LMA File off Algn
0 .interp 0000001c 0000000000400238 0000000000400238 00000238 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
1 .note.ABI-tag 00000020 0000000000400254 0000000000400254 00000254 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
2 .note.gnu.build-id 00000024 0000000000400274 0000000000400274 00000274 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
3 .hash 0000003c 0000000000400298 0000000000400298 00000298 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .gnu.hash 0000001c 00000000004002d8 00000000004002d8 000002d8 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
5 .dynsym 000000f0 00000000004002f8 00000000004002f8 000002f8 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
6 .dynstr 0000007e 00000000004003e8 00000000004003e8 000003e8 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
7 .gnu.version 00000014 0000000000400466 0000000000400466 00000466 2**1
CONTENTS, ALLOC, LOAD, READONLY, DATA
8 .gnu.version_r 00000020 0000000000400480 0000000000400480 00000480 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
9 .rela.dyn 00000018 00000000004004a0 00000000004004a0 000004a0 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
10 .rela.plt 000000c0 00000000004004b8 00000000004004b8 000004b8 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
11 .init 00000018 0000000000400578 0000000000400578 00000578 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
12 .plt 00000090 0000000000400590 0000000000400590 00000590 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
13 .text 00000298 0000000000400620 0000000000400620 00000620 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE
14 .fini 0000000e 00000000004008b8 00000000004008b8 000008b8 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
15 .rodata 00000068 00000000004008c8 00000000004008c8 000008c8 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
16 .eh_frame_hdr 00000024 0000000000400930 0000000000400930 00000930 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
17 .eh_frame 0000007c 0000000000400958 0000000000400958 00000958 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
18 .ctors 00000010 0000000000600e18 0000000000600e18 00000e18 2**3
CONTENTS, ALLOC, LOAD, DATA
19 .dtors 00000010 0000000000600e28 0000000000600e28 00000e28 2**3
CONTENTS, ALLOC, LOAD, DATA
20 .jcr 00000008 0000000000600e38 0000000000600e38 00000e38 2**3
CONTENTS, ALLOC, LOAD, DATA
21 .dynamic 000001a0 0000000000600e40 0000000000600e40 00000e40 2**3
CONTENTS, ALLOC, LOAD, DATA
22 .got 00000008 0000000000600fe0 0000000000600fe0 00000fe0 2**3
CONTENTS, ALLOC, LOAD, DATA
23 .got.plt 00000058 0000000000600fe8 0000000000600fe8 00000fe8 2**3
CONTENTS, ALLOC, LOAD, DATA
24 .data 00000010 0000000000601040 0000000000601040 00001040 2**3
CONTENTS, ALLOC, LOAD, DATA
25 .bss 00000010 0000000000601050 0000000000601050 00001050 2**3
ALLOC
26 .comment 00000023 0000000000000000 0000000000000000 00001050 2**0
CONTENTS, READONLY
27 .debug_aranges 00000030 0000000000000000 0000000000000000 00001073 2**0
CONTENTS, READONLY, DEBUGGING
28 .debug_pubnames 0000001b 0000000000000000 0000000000000000 000010a3 2**0
CONTENTS, READONLY, DEBUGGING
29 .debug_info 000001a5 0000000000000000 0000000000000000 000010be 2**0
CONTENTS, READONLY, DEBUGGING
30 .debug_abbrev 000000cb 0000000000000000 0000000000000000 00001263 2**0
CONTENTS, READONLY, DEBUGGING
31 .debug_line 0000007b 0000000000000000 0000000000000000 0000132e 2**0
CONTENTS, READONLY, DEBUGGING
32 .debug_str 000001ce 0000000000000000 0000000000000000 000013a9 2**0
CONTENTS, READONLY, DEBUGGING
33 .debug_loc 0000004c 0000000000000000 0000000000000000 00001577 2**0
CONTENTS, READONLY, DEBUGGING
SYMBOL TABLE:
0000000000400238 l d .interp 0000000000000000 .interp
0000000000400254 l d .note.ABI-tag 0000000000000000 .note.ABI-tag
0000000000400274 l d .note.gnu.build-id 0000000000000000 .note.gnu.build-id
0000000000400298 l d .hash 0000000000000000 .hash
00000000004002d8 l d .gnu.hash 0000000000000000 .gnu.hash
00000000004002f8 l d .dynsym 0000000000000000 .dynsym
00000000004003e8 l d .dynstr 0000000000000000 .dynstr
0000000000400466 l d .gnu.version 0000000000000000 .gnu.version
...
...
...
So we see that a detailed information was produced in the output.
Syntax and Options
objdump [options] objfile...
| Short Option | Long Option | Option Description |
|---|---|---|
| -a | –archive-header | If any of the objfile files are archives, display the archive header information (in a format similar to ls -l). Besides the information you could list with ar tv, objdump -a shows the object file format of each archive member. |
| –adjust-vma=offset | When dumping information, first add offset to all the section addresses. This is useful if the section addresses do not correspond to the symbol table, which can happen when putting sections at particular addresses when using a format which can not represent section addresses, such as a.out. | |
| -C | –demangle[=style] | Decode (demangle) low-level symbol names into user-level names. Besides removing any initial underscore perpended by the system, this makes C++ function names readable. Different compilers have different mangling styles. The optional demangling style argument can be used to choose an appropriate demangling style for your compiler. |
| -e | –debugging-tags | Like -g, but the information is generated in a format compatible with ctags tool. |
| -D | –disassemble-all | Like -d, but disassemble the contents of all sections, not just those expected to contain instructions. If the target is an ARM architecture this switch also has the effect of forcing the disassembler to decode pieces of data found in code sections as if they were instructions. |
| -EB, -EL | –endian={big|little} | Specify the endianness of the object files. This only affects disassembly. This can be useful when disassembling a file format which does not describe endianness information, such as S-records. |
| -F | –file-offsets | When disassembling sections, whenever a symbol is displayed, also display the file offset of the region of data that is about to be dumped. If zeros are being skipped, then when disassembly resumes, tell the user how many zeros were skipped and the file offset of the location from where the disassembly resumes. When dumping sections, display the file offset of the location from where the dump starts. |
| -j name | –section=name | Display information only for section name. |
Related Commands
nm
readelf