HelenOS sources

ID_PFR1_SEC_EXT_MASK  154 boot/arch/arm32/include/arch/cp15.h 	ID_PFR1_SEC_EXT_MASK = 0xf << 4,
ID_PFR1_SEC_EXT_MASK  154 kernel/arch/arm32/include/arch/cp15.h 	ID_PFR1_SEC_EXT_MASK = 0xf << 4,
ID_PFR1_SEC_EXT_MASK  154 uspace/lib/c/arch/arm32/include/libarch/cp15.h 	ID_PFR1_SEC_EXT_MASK = 0xf << 4,
HelenOS homepage, sources at GitHub