HelenOS sources

ESR_EC_IA_LOWER_EL  127 boot/arch/arm64/include/arch/regutils.h #define ESR_EC_IA_LOWER_EL  0x20
ESR_EC_IA_LOWER_EL  127 kernel/arch/arm64/include/arch/regutils.h #define ESR_EC_IA_LOWER_EL  0x20
ESR_EC_IA_LOWER_EL  127 uspace/lib/c/arch/arm64/include/libarch/regutils.h #define ESR_EC_IA_LOWER_EL  0x20

HelenOS homepage, sources at GitHub