Search notes:

include/generated/autoconf.h

include/generated/autoconf.h contains a list of CONFIG_* macro definitions:

/*
 * Automatically generated file; DO NOT EDIT.
 * Linux/x86 6.5.0-rc7 Kernel Configuration
 */
#define CONFIG_RING_BUFFER 1
#define CONFIG_HAVE_ARCH_SECCOMP_FILTER 1
#define CONFIG_SND_PROC_FS 1
#define CONFIG_SCSI_DMA 1
…

This file is updated by make syncconfig when .config (or the file referred to by KCONFIG_CONFIG) changes.

kernel/gen_kheaders.sh says this about autoconf.h:

When Kconfig regenerates include/generated/autoconf.h, its timestamp is updated, but the contents might be still the same. When any CONFIG option is changed, Kconfig touches the corresponding timestamp file include/config/*. Hence, the md5sum detects the configuration change anyway. We do not need to check include/generated/autoconf.h explicitly.

include/generated/autoconf.h

See also