Commit 51d42f0f authored Feb 28, 2018 by Segher Boessenkool Committed by Michael Ellerman Mar 06, 2018

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>

parent 661e50bc

arch/powerpc/Makefile

+2 −0

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

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