From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38689 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753011AbbJMUmo (ORCPT ); Tue, 13 Oct 2015 16:42:44 -0400 Subject: Patch "ARM: 8429/1: disable GCC SRA optimization" has been added to the 3.14-stable tree To: ard.biesheuvel@linaro.org, gregkh@linuxfoundation.org, nico@linaro.org, rmk+kernel@arm.linux.org.uk Cc: , From: Date: Tue, 13 Oct 2015 13:38:02 -0700 Message-ID: <1444768682227203@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled ARM: 8429/1: disable GCC SRA optimization to the 3.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm-8429-1-disable-gcc-sra-optimization.patch and it can be found in the queue-3.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From a077224fd35b2f7fbc93f14cf67074fc792fbac2 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Thu, 3 Sep 2015 13:24:40 +0100 Subject: ARM: 8429/1: disable GCC SRA optimization From: Ard Biesheuvel commit a077224fd35b2f7fbc93f14cf67074fc792fbac2 upstream. While working on the 32-bit ARM port of UEFI, I noticed a strange corruption in the kernel log. The following snprintf() statement (in drivers/firmware/efi/efi.c:efi_md_typeattr_format()) snprintf(pos, size, "|%3s|%2s|%2s|%2s|%3s|%2s|%2s|%2s|%2s]", was producing the following output in the log: | | | | | |WB|WT|WC|UC] | | | | | |WB|WT|WC|UC] | | | | | |WB|WT|WC|UC] |RUN| | | | |WB|WT|WC|UC]* |RUN| | | | |WB|WT|WC|UC]* | | | | | |WB|WT|WC|UC] |RUN| | | | |WB|WT|WC|UC]* | | | | | |WB|WT|WC|UC] |RUN| | | | | | | |UC] |RUN| | | | | | | |UC] As it turns out, this is caused by incorrect code being emitted for the string() function in lib/vsprintf.c. The following code if (!(spec.flags & LEFT)) { while (len < spec.field_width--) { if (buf < end) *buf = ' '; ++buf; } } for (i = 0; i < len; ++i) { if (buf < end) *buf = *s; ++buf; ++s; } while (len < spec.field_width--) { if (buf < end) *buf = ' '; ++buf; } when called with len == 0, triggers an issue in the GCC SRA optimization pass (Scalar Replacement of Aggregates), which handles promotion of signed struct members incorrectly. This is a known but as yet unresolved issue. (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65932). In this particular case, it is causing the second while loop to be executed erroneously a single time, causing the additional space characters to be printed. So disable the optimization by passing -fno-ipa-sra. Acked-by: Nicolas Pitre Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King Signed-off-by: Greg Kroah-Hartman --- arch/arm/Makefile | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -52,6 +52,14 @@ endif comma = , +# +# The Scalar Replacement of Aggregates (SRA) optimization pass in GCC 4.9 and +# later may result in code being generated that handles signed short and signed +# char struct members incorrectly. So disable it. +# (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65932) +# +KBUILD_CFLAGS += $(call cc-option,-fno-ipa-sra) + # This selects which instruction set is used. # Note that GCC does not numerically define an architecture version # macro, but instead defines a whole series of macros which makes Patches currently in stable-queue which might be from ard.biesheuvel@linaro.org are queue-3.14/arm-8429-1-disable-gcc-sra-optimization.patch