How to get the .config from a Linux kernel image?

I have a Linux kernel image in elf format and I want to find out what .config file was used to build this kernel. When I do an objdump of the image, I see a section called kernel_config_data that contains text but does not look like the config file. Is there a way to retrieve this information?

Answer

Assuming your kernel was built with the IKCONFIG option, you can use the scripts/extract-ikconfig tool to extract the original .config file.

Alternately, you can boot that kernel and find the embedded configuration in /proc/config.gz.