On 03/09/2019 17.50, Andreas Smas wrote: > Hi, > > For me, kernels built including this commit > b059f801a937 (x86/purgatory: Use CFLAGS_REMOVE rather than reset > KBUILD_CFLAGS) > > results in kexec() failing to load the kernel: > > kexec: Undefined symbol: __stack_chk_fail > kexec-bzImage64: Loading purgatory failed > > Can be seen: > > $ readelf -a arch/x86/purgatory/purgatory.ro | grep UND > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND > 51: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __stack_chk_fail > > Using: gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
Ubuntu's gcc has -fstack-protector enabled by default, so this happens if one doesn't pass -fno-stack-protector (which I guess is implied by -ffreestanding) explicitly. > Adding -ffreestanding or -fno-stack-protector to ccflags-y in > arch/x86/purgatory/Makefile > fixes the problem. Not sure which would be preferred. Probably -fno-stack-protector, guarded by CONFIG_CC_HAS_STACKPROTECTOR_NONE (because not all gccs understand -fno-stack-protector), so ifdef CONFIG_CC_HAS_STACKPROTECTOR_NONE ccflags-y += -fno-stack-protector endif Rasmus
