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x86/purgatory: Add -fno-stack-protector

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The purgatory Makefile removes -fstack-protector options if they were
configured in, but does not currently add -fno-stack-protector.

If gcc was configured with the --enable-default-ssp configure option,
this results in the stack protector still being enabled for the
purgatory (absent distro-specific specs files that might disable it
again for freestanding compilations), if the main kernel is being
compiled with stack protection enabled (if it's disabled for the main
kernel, the top-level Makefile will add -fno-stack-protector).

This will break the build since commit
  e4160b2e4b ("x86/purgatory: Fail the build if purgatory.ro has missing symbols")
and prior to that would have caused runtime failure when trying to use
kexec.

Explicitly add -fno-stack-protector to avoid this, as done in other
Makefiles that need to disable the stack protector.

Reported-by: Gabriel C <nix.or.die@googlemail.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Arvind Sankar 2020-06-16 18:25:47 -04:00 committed by Linus Torvalds
parent 651220e2ae
commit ff58155ca4
1 changed files with 1 additions and 0 deletions
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arch/x86/purgatory/Makefile
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@ -34,6 +34,7 @@ KCOV_INSTRUMENT := n
PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss
PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING
PURGATORY_CFLAGS += $(call cc-option,-fno-stack-protector)
# 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