objdump

Additional Notes

objdump displays information about object files, executables, and shared libraries. It can disassemble machine code, show symbol tables, display section headers, dump raw binary content, and report file headers. It works primarily with ELF format files on Linux systems.

Developers use objdump for reverse engineering, debugging compiler output, comparing optimized versus unoptimized code, inspecting binary sizes, verifying linker operations, and analyzing malware or unknown binaries. It is a standard tool in the binutils package and is available on virtually all Linux distributions.

Syntax

objdump [options] [object-files...]

Parameters

• object-files: One or more object files, executables, static libraries, or shared libraries to inspect.

Common Options

• -d, --disassemble: Disassemble executable sections into assembly instructions.
• -D, --disassemble-all: Disassemble all sections, not just executable ones.
• -S, --source: Interleave source code with disassembly when debug information is available.
• -x, --all-headers: Display all available header information.
• -f, --file-headers: Display only the ELF file header.
• -p, --private-headers: Display format-specific header information.
• -h, --section-headers: Display section header table.
• -t, --syms: Display symbol table entries.
• -T, --dynamic-syms: Display dynamic symbol table entries.
• -r, --reloc: Display relocation entries.
• -R, --dynamic-reloc: Display dynamic relocation entries.
• -s, --full-contents: Display the full contents of all sections.
• -j section: Display information only for a specific section.
• -M options: Pass disassembler options (e.g., intel for Intel syntax).
• --no-show-raw-insn: Omit raw instruction bytes in disassembly output.
• -C, --demangle: Demangle C++ symbol names.
• -l, --line-numbers: Include source line numbers.
• -g, --debugging: Display debug information.

Examples

objdump -d main

Disassemble executable code sections.

objdump -d -M intel main

Disassemble using Intel syntax instead of AT&T syntax.

objdump -S main

Interleave source code with disassembly. Compile with -g for best results.

objdump -x libfoo.so

Show all headers and metadata for a shared library.

objdump -t main.o

Display the symbol table of an object file.

objdump -s -j .rodata main

Dump the contents of the read-only data section.

objdump -r main.o

Show relocation entries, useful for understanding linker operations.

objdump -C -d libapp.so

Disassemble a shared library with demangled C++ symbol names.

objdump -h /bin/ls

List section headers and sizes in the ls binary.

Practical Notes

• objdump -S requires debug symbols. Compile with -g for annotated disassembly.
• Use -M intel for Intel syntax, which most developers find easier to read than the default AT&T syntax.
• For stripped binaries, objdump -d still works, but symbol names are lost.
• The binutils package also includes readelf, nm, size, strings, and strip for complementary binary analysis.
• For cross-platform development, use the cross-compilation version like aarch64-linux-gnu-objdump.
• For deeper debugging, combine objdump with gdb, strace, and ltrace.