What is the objdump command used for?

The objdump command displays detailed information about object files, executables, and libraries. It can show disassembly, section headers, symbol tables, and other binary file information useful for debugging and reverse engineering.

How do I disassemble an executable file?

Use 'objdump -d executable_name' to disassemble the executable. For more detailed output, use 'objdump -D executable_name' to disassemble all sections, or 'objdump -S executable_name' to include source code if available.

How do I view the file headers and sections?

Use 'objdump -h executable_name' to display section headers, 'objdump -f executable_name' to show file headers, and 'objdump -x executable_name' to display all header information including symbols and relocations.

objdump

Display information about object files, executables, and libraries

Syntax

objdump [options] objfile...

Basic Usage

Display file headers

objdump -f program

Shows the file header information of the specified executable.

Display section headers

objdump -h program

Disassemble executable

objdump -d program

Display all headers

objdump -x program

Common Options

-a, --archive-headers: Display archive header information
-d, --disassemble: Disassemble sections with instructions
-D, --disassemble-all: Disassemble all sections
-f, --file-headers: Display file header information
-h, --section-headers: Display section headers
-H, --help: Display help information
-j, --section: Only display information for specified section
-l, --line-numbers: Include line numbers and filenames
-p, --private-headers: Display object format specific information
-r, --reloc: Display relocation entries
-R, --dynamic-reloc: Display dynamic relocation entries
-s, --full-contents: Display full contents of sections
-S, --source: Intermix source code with disassembly
-t, --syms: Display symbol table
-T, --dynamic-syms: Display dynamic symbol table
-x, --all-headers: Display all available header information

Practical Examples

Basic disassembly

objdump -d program

Disassembly with source code

objdump -S program

Show symbol table

objdump -t program

Show section headers

objdump -h program

Show file headers

objdump -f program

Show all headers

objdump -x program

Show specific section

objdump -j .text -d program

Show relocation information

objdump -r program

Show full section contents

objdump -s program

Show archive information

objdump -a library.a

Understanding Output

Disassembly Output

Disassembly shows:

Address: Memory address of instruction
Machine code: Hexadecimal representation
Assembly: Human-readable assembly code
Comments: Additional information if available

Section Headers

Idx: Section index
Name: Section name
Size: Section size in bytes
VMA: Virtual memory address
LMA: Load memory address
File off: File offset
Algn: Alignment requirements

Symbol Table

Address: Symbol address
Flags: Symbol attributes
Section: Section containing symbol
Name: Symbol name

Best Practices

Use Cases

Debugging binary files and executables
Reverse engineering and analysis
Understanding program structure
Analyzing compiler output
Security research and vulnerability analysis

Important Notes

Debug information may be stripped from release builds
Disassembly can be complex for optimized code
Some sections may not be disassemblable
Output format varies by architecture
Use appropriate options for your analysis needs