1. Reuse the implementation of memcpy and memset instead of relying on __builtin_memcpy and __builtin_memset as it causes infinite recursion in Clang (at any opt level) or GCC at -O2. 2. Don't reset KBUILD_CFLAGS, rather filter CONFIG_FUNCTION_TRACER, CONFIG_STACKPROTECTOR, CONFIG_STACKPROTECTOR_STRONG, and CONFIG_RETPOLINE flags via `CFLAGS_REMOVE_<file>.o'.
A good test of this series (besides boot testing a kexec kernel): * There should be no undefined symbols in arch/x86/purgatory/purgatory.ro: $ nm arch/x86/purgatory/purgatory.ro particularly `warn`, `bcmp`, `__stack_chk_fail`, `memcpy` or `memset`. * `-pg`, `-fstack-protector`, `-fstack-protector-strong`, and $(RETPOLINE_CFLAGS) should not be added to the command line for the C source files under arch/x86/purgatory/ when compiling with CONFIG_FUNCTION_TRACER=y, CONFIG_STACKPROTECTOR=y, CONFIG_STACKPROTECTOR_STRONG=y, and CONFIG_RETPOLINE=y. V5 of: https://lkml.org/lkml/2019/7/25/1276 Nick Desaulniers (2): x86/purgatory: do not use __builtin_memcpy and __builtin_memset x86/purgatory: use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS arch/x86/boot/string.c | 7 +++++++ arch/x86/purgatory/Makefile | 29 ++++++++++++++++++++++++----- arch/x86/purgatory/purgatory.c | 6 ++++++ arch/x86/purgatory/string.c | 23 ----------------------- 4 files changed, 37 insertions(+), 28 deletions(-) delete mode 100644 arch/x86/purgatory/string.c -- 2.22.0.709.g102302147b-goog
