x86/purgatory: Use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS (b059f801) · Commits · 戴 / test

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: ("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

arch/x86/purgatory/Makefile

+28 −5

Original line number	Diff line number	Diff line
		@@ -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)

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