Dependencies
GNU Binutils
Binary File Descriptor library (BFD)
Instruction Set Architecture (ISA)
Object File Format (executable files, object code, shared libraries, and core dumps)
Deutsch
a.out
ELF
COFF
Fat Binary
Universal Binary
English
An object file is a file containing object code, meaning relocatable format machine code that is usually not directly executable. In addition to the object code itself, object files may contain metadata used for linking or debugging, including: information to resolve symbolic cross-references between different modules, relocation information, stack unwinding information, comments, program symbols, debugging or profiling information.
Executable
Object file
a.out
ELF
COFF
Mach-O
Debugging formats
GNU Debugger
Debugging formats DWARF and STAB
DWARF
stabs
Target Selection
$ objdump.exe -i $ objdump.exe -H supported targets (object file format): pe-x86-64 pei-x86-64 pe-bigobj-x86-64 elf64-x86-64 elf64-l1om elf64-k1om pe-i386 pei-i386 elf32-i386 elf32-iamcu elf64-little elf64-big elf32-little elf32-big plugin srec symbolsrec verilog tekhex binary ihex supported architectures: i386 i386:x86-64 i386:x64-32 i8086 i386:intel i386:x86-64:intel i386:x64-32:intel i386:nacl i386:x86-64:nacl i386:x64-32:nacl iamcu iamcu:intel l1om l1om:intel k1om k1om:intel plugin $ arm-none-eabi-objdump.exe -i $ arm-none-eabi-objdump.exe -H supported targets (object file format): elf32-littlearm elf32-bigarm elf32-little elf32-big plugin srec symbolsrec verilog tekhex binary ihex supported architectures: arm armv2 armv2a armv3 armv3m armv4 armv4t armv5 armv5t armv5te xscale ep9312 iwmmxt iwmmxt2 arm_any plugin
ld
| Option | Purpose |
-b input-format |
What input format is used. You may want to use this option if you are linking files with an unusual binary format. You can also use -b to switch formats explicitly. You can list the available binary formats with objdump -i |
-r |
Generate relocatable output—i.e., generate an output file that can in turn serve as input to ld. This is often called partial linking.This option does the same thing as -i. |
-i |
Perform an incremental link (same as option -r). |
-o output |
Use output as the name for the program produced by ld; if this option is not specified, the name a.out is used by default. |
-T scriptfile |
Use scriptfile as the linker script. This script replaces ld‘s default linker script (rather than adding to it), so commandfile must specify everything necessary to describe the output file. If scriptfile does not exist in the current directory, ld looks for it in the directories specified by any preceding -L options. Multiple -T options accumulate. |
Linker Script
LD
LD: Linker Scripts
Linker Scripts
Linker Scripts
Red Hat Enterprise Linux 4: Using ld, the Gnu Linker – Linker Scripts
Chapter 4. Linker Scripts
4.2. Linker Script Format
4.3. Simple Linker Script Example
4.4. Simple Linker Script Commands
4.5. Assigning Values to Symbols
4.6. SECTIONS Command
4.7. MEMORY Command
4.8. PHDRS Command
4.9. VERSION Command
4.10. Expressions in Linker Scripts
4.11. Implicit Linker Scripts
objdump – displays information about one or more object files
Linux Objdump Command Examples (Disassemble a Binary File)
objcopy – copies the contents of an object file to another
| Option | Purpose |
-I bfdname |
Consider the source file’s object format to be bfdname, rather than attempting to deduce (herleiten/rückschliessen) it. |
-O bfdname |
Write the output file using the object format bfdname. |
-B bfdarch |
Useful when transforming a architecture-less input file into an object file. In this case the output architecture can be set to bfdarch. |
--rename-section oldname=newname[,flags] |
Rename a section from oldname to newname, optionally changing the section’s flags to flags in the process. This option is particularly helpful when the input format is binary, since this will always create a section called .data. If for example, you wanted instead to create a section called .rodata containing binary data you could use a command line to achieve it. |
objcopy \ -I binary \ -O <output_format> \ -B <architecture> \ --rename-section .data=.rodata,alloc,load,readonly,data,contents \ <input_binary_file> \ <output_object_file>
nm – list symbols from object file
Example Scripts
#!/bin/sh
# Convert a raw binary image into an ELF file suitable for loading into a disassembler
cat > raw$$.ld <<EOF
SECTIONS
{
EOF
echo " . = $3;" >> raw$$.ld
cat >> raw$$.ld <<EOF
.text : { *(.text) }
}
EOF
CROSS_PREFIX=arm-none-eabi-
${CROSS_PREFIX}ld -b binary -r -o raw$$.elf $1
${CROSS_PREFIX}objcopy --rename-section .data=.text \
--set-section-flags .data=alloc,code,load raw$$.elf
${CROSS_PREFIX}ld raw$$.elf -T raw$$.ld -o $2
${CROSS_PREFIX}strip -s $2
rm -rf raw$$.elf raw$$.ld