Making objdump -S find your source code
We all know the situation: We want to disassemble the most awesome pre-compiled object file, with accompanying sources, using objdump and we would like to view the assembly and C-code interleaved, so we use -S. Unfortunately, objdump fails to find the sources, and we are sad 🙁
How does objdump look for the sources? Normally the paths are hardcoded in the object file in the DWARF information. To inspect the DWARF debug info:
$ objdump --dwarf myobject.o | less
and look for DW_TAG_compile_unit sections, where the paths should exist like:
<25> DW_AT_name : C:/ARM/myfile.c
Of course, this might not be the path you have on your machine, and thus objdump gives up.
However, we can use an undocumented option to objdump: the -I or –include:
$ objdump -I ../mysources -S myobject.o | less
and voila, objdump finds the sources, inlines the C-code, and everything is awesome!
Nice idea! Thank you very much! But it more or less only works if the source files are all in the same directory. I need it for the Linux kernel and after some strace and looking at the man page of objdump I’ve finally found the correct commands to make it work there: cd /usr/src/linux; objdump –prefix=”.” –prefix-strip=3 -S /usr/lib/debug/vmlinux # This strips the first 3 parts from the absolute path and replaces them with “.” so that I get relative paths to the current working directory. The level required depends on the absolute path which is already set.