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powerpc: Keep const vars out of writable .sdata 

Newer gcc will support "-mno-readonly-in-sdata"[1], which makes sure that
the optimization on PPC32 for variables getting moved into the .sdata
section will not apply to const variables (which must be in .rodata).

This was originally noticed in mm/rodata_test.c when rodata_test_data
was not static:

c0695034 g     O .data	00000004 rodata_test_data

After this patch with an updated compiler, this is correctly in .rodata.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82411

Reported-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
hifive-unleashed-5.1
Segher Boessenkool 2018-02-28 17:02:49 -08:00 committed by Michael Ellerman
parent 661e50bc85
commit 51d42f0f5f
1 changed files with 2 additions and 0 deletions
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2
arch/powerpc/Makefile
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@ -141,7 +141,9 @@ AFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv1)
endif
CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mcmodel=medium,$(call cc-option,-mminimal-toc))
CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mno-pointers-to-nested-functions)
CFLAGS-$(CONFIG_PPC32) := -ffixed-r2 $(MULTIPLEWORD)
CFLAGS-$(CONFIG_PPC32) += $(call cc-option,-mno-readonly-in-sdata)
ifeq ($(CONFIG_PPC_BOOK3S_64),y)
CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=power7,-mtune=power4)