The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b059f801a937d164e03b33c1848bb3dca67c0b04 Mon Sep 17 00:00:00 2001
From: Nick Desaulniers ndesaulniers@google.com Date: Wed, 7 Aug 2019 15:15:33 -0700 Subject: [PATCH] x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS
KBUILD_CFLAGS is very carefully built up in the top level Makefile, particularly when cross compiling or using different build tools. Resetting KBUILD_CFLAGS via := assignment is an antipattern.
The comment above the reset mentions that -pg is problematic. Other Makefiles use `CFLAGS_REMOVE_file.o = $(CC_FLAGS_FTRACE)` when CONFIG_FUNCTION_TRACER is set. Prefer that pattern to wiping out all of the important KBUILD_CFLAGS then manually having to re-add them. Seems also that __stack_chk_fail references are generated when using CONFIG_STACKPROTECTOR or CONFIG_STACKPROTECTOR_STRONG.
Fixes: 8fc5b4d4121c ("purgatory: core purgatory functionality") Reported-by: Vaibhav Rustagi vaibhavrustagi@google.com Suggested-by: Peter Zijlstra peterz@infradead.org Suggested-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Vaibhav Rustagi vaibhavrustagi@google.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190807221539.94583-2-ndesaulniers@google.com
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile index 91ef244026d2..8901a1f89cf5 100644 --- a/arch/x86/purgatory/Makefile +++ b/arch/x86/purgatory/Makefile @@ -20,11 +20,34 @@ KCOV_INSTRUMENT := n
# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That # in turn leaves some undefined symbols like __fentry__ in purgatory and not -# sure how to relocate those. Like kexec-tools, use custom flags. - -KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large -KBUILD_CFLAGS += -m$(BITS) -KBUILD_CFLAGS += $(call cc-option,-fno-PIE) +# sure how to relocate those. +ifdef CONFIG_FUNCTION_TRACER +CFLAGS_REMOVE_sha256.o += $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_purgatory.o += $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_string.o += $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_kexec-purgatory.o += $(CC_FLAGS_FTRACE) +endif + +ifdef CONFIG_STACKPROTECTOR +CFLAGS_REMOVE_sha256.o += -fstack-protector +CFLAGS_REMOVE_purgatory.o += -fstack-protector +CFLAGS_REMOVE_string.o += -fstack-protector +CFLAGS_REMOVE_kexec-purgatory.o += -fstack-protector +endif + +ifdef CONFIG_STACKPROTECTOR_STRONG +CFLAGS_REMOVE_sha256.o += -fstack-protector-strong +CFLAGS_REMOVE_purgatory.o += -fstack-protector-strong +CFLAGS_REMOVE_string.o += -fstack-protector-strong +CFLAGS_REMOVE_kexec-purgatory.o += -fstack-protector-strong +endif + +ifdef CONFIG_RETPOLINE +CFLAGS_REMOVE_sha256.o += $(RETPOLINE_CFLAGS) +CFLAGS_REMOVE_purgatory.o += $(RETPOLINE_CFLAGS) +CFLAGS_REMOVE_string.o += $(RETPOLINE_CFLAGS) +CFLAGS_REMOVE_kexec-purgatory.o += $(RETPOLINE_CFLAGS) +endif
$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE $(call if_changed,ld)