From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753107Ab3J2SHT (ORCPT ); Tue, 29 Oct 2013 14:07:19 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:59286 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752242Ab3J2SFN (ORCPT ); Tue, 29 Oct 2013 14:05:13 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Linus Torvalds , Andrew Morton , Ingo Molnar , Kamal Mostafa Subject: [PATCH 3.8 19/81] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Date: Tue, 29 Oct 2013 11:03:40 -0700 Message-Id: <1383069882-11437-20-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1383069882-11437-1-git-send-email-kamal@canonical.com> References: <1383069882-11437-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.8.13.12 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Ingo Molnar commit 3f0116c3238a96bc18ad4b4acefe4e7be32fa861 upstream. Fengguang Wu, Oleg Nesterov and Peter Zijlstra tracked down a kernel crash to a GCC bug: GCC miscompiles certain 'asm goto' constructs, as outlined here: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 Implement a workaround suggested by Jakub Jelinek. Reported-and-tested-by: Fengguang Wu Reported-by: Oleg Nesterov Reported-by: Peter Zijlstra Suggested-by: Jakub Jelinek Reviewed-by: Richard Henderson Cc: Linus Torvalds Cc: Andrew Morton Signed-off-by: Ingo Molnar [ kamal: backport to 3.8 ] Signed-off-by: Kamal Mostafa --- arch/arm/include/asm/jump_label.h | 2 +- arch/mips/include/asm/jump_label.h | 2 +- arch/powerpc/include/asm/jump_label.h | 2 +- arch/s390/include/asm/jump_label.h | 2 +- arch/sparc/include/asm/jump_label.h | 2 +- arch/x86/include/asm/cpufeature.h | 2 +- arch/x86/include/asm/jump_label.h | 2 +- include/linux/compiler-gcc4.h | 15 +++++++++++++++ 8 files changed, 22 insertions(+), 7 deletions(-) diff --git a/arch/arm/include/asm/jump_label.h b/arch/arm/include/asm/jump_label.h index bfc198c..863c892 100644 --- a/arch/arm/include/asm/jump_label.h +++ b/arch/arm/include/asm/jump_label.h @@ -16,7 +16,7 @@ static __always_inline bool arch_static_branch(struct static_key *key) { - asm goto("1:\n\t" + asm_volatile_goto("1:\n\t" JUMP_LABEL_NOP "\n\t" ".pushsection __jump_table, \"aw\"\n\t" ".word 1b, %l[l_yes], %c0\n\t" diff --git a/arch/mips/include/asm/jump_label.h b/arch/mips/include/asm/jump_label.h index 4d6d77e..e194f95 100644 --- a/arch/mips/include/asm/jump_label.h +++ b/arch/mips/include/asm/jump_label.h @@ -22,7 +22,7 @@ static __always_inline bool arch_static_branch(struct static_key *key) { - asm goto("1:\tnop\n\t" + asm_volatile_goto("1:\tnop\n\t" "nop\n\t" ".pushsection __jump_table, \"aw\"\n\t" WORD_INSN " 1b, %l[l_yes], %0\n\t" diff --git a/arch/powerpc/include/asm/jump_label.h b/arch/powerpc/include/asm/jump_label.h index ae098c4..f016bb6 100644 --- a/arch/powerpc/include/asm/jump_label.h +++ b/arch/powerpc/include/asm/jump_label.h @@ -19,7 +19,7 @@ static __always_inline bool arch_static_branch(struct static_key *key) { - asm goto("1:\n\t" + asm_volatile_goto("1:\n\t" "nop\n\t" ".pushsection __jump_table, \"aw\"\n\t" JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t" diff --git a/arch/s390/include/asm/jump_label.h b/arch/s390/include/asm/jump_label.h index 6c32190..346b1c8 100644 --- a/arch/s390/include/asm/jump_label.h +++ b/arch/s390/include/asm/jump_label.h @@ -15,7 +15,7 @@ static __always_inline bool arch_static_branch(struct static_key *key) { - asm goto("0: brcl 0,0\n" + asm_volatile_goto("0: brcl 0,0\n" ".pushsection __jump_table, \"aw\"\n" ASM_ALIGN "\n" ASM_PTR " 0b, %l[label], %0\n" diff --git a/arch/sparc/include/asm/jump_label.h b/arch/sparc/include/asm/jump_label.h index 5080d16..ec2e2e2 100644 --- a/arch/sparc/include/asm/jump_label.h +++ b/arch/sparc/include/asm/jump_label.h @@ -9,7 +9,7 @@ static __always_inline bool arch_static_branch(struct static_key *key) { - asm goto("1:\n\t" + asm_volatile_goto("1:\n\t" "nop\n\t" "nop\n\t" ".pushsection __jump_table, \"aw\"\n\t" diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 2d9075e..d3f0db1 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -346,7 +346,7 @@ extern const char * const x86_power_flags[32]; static __always_inline __pure bool __static_cpu_has(u16 bit) { #if __GNUC__ > 4 || __GNUC_MINOR__ >= 5 - asm goto("1: jmp %l[t_no]\n" + asm_volatile_goto("1: jmp %l[t_no]\n" "2:\n" ".section .altinstructions,\"a\"\n" " .long 1b - .\n" diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index 3a16c14..0297669 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -13,7 +13,7 @@ static __always_inline bool arch_static_branch(struct static_key *key) { - asm goto("1:" + asm_volatile_goto("1:" STATIC_KEY_INITIAL_NOP ".pushsection __jump_table, \"aw\" \n\t" _ASM_ALIGN "\n\t" diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h index c9785c2..e8f0bf9 100644 --- a/include/linux/compiler-gcc4.h +++ b/include/linux/compiler-gcc4.h @@ -67,6 +67,21 @@ #define __visible __attribute__((externally_visible)) #endif +/* + * GCC 'asm goto' miscompiles certain code sequences: + * + * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 + * + * Work it around via a compiler barrier quirk suggested by Jakub Jelinek. + * Fixed in GCC 4.8.2 and later versions. + * + * (asm goto is automatically volatile - the naming reflects this.) + */ +#if GCC_VERSION <= 40801 +# define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0) +#else +# define asm_volatile_goto(x...) do { asm goto(x); } while (0) +#endif #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP #if __GNUC_MINOR__ >= 4 -- 1.8.1.2