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Commit 1332429b authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds
Browse files

./Makefile: explain stack-protector-strong CONFIG logic 



This adds a hopefully helpful comment above the (seemingly weird) compiler
flag selection logic.

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5838d444

Makefile

+16 −0
Original line number Diff line number Diff line
@@ -636,6 +636,22 @@ KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN}) 
endif



# Handle stack protector mode.

#

# Since kbuild can potentially perform two passes (first with the old

# .config values and then with updated .config values), we cannot error out

# if a desired compiler option is unsupported. If we were to error, kbuild

# could never get to the second pass and actually notice that we changed

# the option to something that was supported.

#

# Additionally, we don't want to fallback and/or silently change which compiler

# flags will be used, since that leads to producing kernels with different

# security feature characteristics depending on the compiler used. ("But I

# selected CC_STACKPROTECTOR_STRONG! Why did it build with _REGULAR?!")

#

# The middle ground is to warn here so that the failed option is obvious, but

# to let the build fail with bad compiler flags so that we can't produce a

# kernel when there is a CONFIG and compiler mismatch.

#

ifdef CONFIG_CC_STACKPROTECTOR_REGULAR

  stackp-flag := -fstack-protector

  ifeq ($(call cc-option, $(stackp-flag)),)