x86/purgatory: undefined symbol __stack_chk_fail

[Andreas Smas]

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)

Adding -ffreestanding or -fno-stack-protector to ccflags-y in
arch/x86/purgatory/Makefile
fixes the problem. Not sure which would be preferred.