/proc/config.gz - kernel build configuration

/proc/config.gz (since Linux 2.6) This file exposes the configuration options that were used to build the currently running kernel, in the same format as they would be shown in the .config file that resulted when configuring the kernel (using make xconfig, make config, or similar). The file contents are compressed; view or search them using zcat(1) and zgrep(1). As long as no changes have been made to the following file, the contents of /proc/config.gz are the same as those provided by:

cat /lib/modules/$(uname -r)/build/.config

/proc/config.gz is provided only if the kernel is configured with CONFIG_IKCONFIG_PROC.

proc(5)