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Usefull build tools

This documents includes some useful tools and how to use them for development and debugging.

Most of these tools print output in terminal, which can be problematic if the output is large or you want to save it.

For inspecting the contents and discarding the result I just pipe the output into less:

<command> <options> <input file> | less

For saving file, you can redirect the output into a new file:

<command> <options> <input file> > outputFile.txt

NOTE: > redirection will overwrite the file. If you want to append to it, use >>.

objdump

This tool is used to view contents of object files, such as .o and .elf.The arm toolchain provides arm-none-eabi-objdump.

In context of executable .elf, this can be used to disassemble a section or the entire file. With this tool you can inspect the assembly and state of sections and variables.

Command:

arm-none-eabi-objdump <options> <file.[elf/o]>

Options:

  • -d: disassemble all "runnable" sections (code)
  • -D: disassemble all sections (code and data)
  • -j <section name>: used along with -d/D will display only a selected section
  • -C: demangle symbol names (C++)
  • -h: view only headers (used alone without other options)

Examples

Dump a specific section (example: .rodata):

arm-none-eabi-objdump -D -j .rodata -C ./firmware.bin

Dump the entire file:

arm-none-eabi-objdump -D -C ./firmware.bin

View section headers:

arm-none-eabi-objdump -h ./firmware.bin

readelf

This tool is similar in function to objdump but displays a bit more information. It is also limited to .elf files. The arm toolchain provides arm-none-eabi-readelf.

Command:

arm-none-eabi-readelf <options> <file.elf>

Options:

  • -h: display ELF file header (file information)
  • -S: display sections (a bit nicer than objdump -h, but missing some information)
  • -s: display all symbols (functions, global variables)
  • -C: demangle symbol names (C++), used with -s
  • -x <section name>: hexdumps the section contents (4 groups of 4 byte strings per line)
  • -p <section name>: stringdumps the section contents

Examples

View file information:

arm-none-eabi-readelf -h ./firmware.elf

View sections headers:

arm-none-eabi-readelf -S -C ./firmware.elf

View all symbols:

arm-none-eabi-readelf -s -C ./firmware.elf

Hexdump section:

arm-none-eabi-readelf -x .rodata ./firmware.elf

Stringdump section:

arm-none-eabi-readelf -p .rodata ./firmware.elf

hexdump

Hexdump is used to view and filter raw contents of a file. The output format can be changed. The utility is not specific to arm toolchain and can be found on most linux distributions already installed.

It doesn't do much, therefore it doesn't have as many options, so I use it mainly for viewing bin files:

hexdump -C <file.bin>

This command will display output in hex (two characted per byte, 16 bytes per line) as well as ascii (similar to objdump with -x).