From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-x243.google.com (mail-pf0-x243.google.com [IPv6:2607:f8b0:400e:c00::243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3zsDgk2RgyzF1dj for ; Thu, 1 Mar 2018 12:02:55 +1100 (AEDT) Received: by mail-pf0-x243.google.com with SMTP id h19so874947pfd.12 for ; Wed, 28 Feb 2018 17:02:54 -0800 (PST) Date: Wed, 28 Feb 2018 17:02:49 -0800 From: Kees Cook To: Michael Ellerman Cc: Christophe Leroy , linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, Segher Boessenkool Subject: [PATCH] powerpc: Keep const vars out of writable .sdata Message-ID: <20180301010249.GA18370@beast> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Segher Boessenkool 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 Signed-off-by: Segher Boessenkool Signed-off-by: Kees Cook --- arch/powerpc/Makefile | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index ccd2556bdb53..c7628e973084 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile @@ -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) -- 2.7.4 -- Kees Cook Pixel Security