From patchwork Tue Mar 27 05:29:25 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahiro Yamada X-Patchwork-Id: 10309269 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id BAB1460212 for ; Tue, 27 Mar 2018 05:33:57 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A946E29ADF for ; Tue, 27 Mar 2018 05:33:57 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9D1EA29ADE; Tue, 27 Mar 2018 05:33:57 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C61EC29ADE for ; Tue, 27 Mar 2018 05:33:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751073AbeC0FcH (ORCPT ); Tue, 27 Mar 2018 01:32:07 -0400 Received: from conuserg-09.nifty.com ([210.131.2.76]:44864 "EHLO conuserg-09.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751805AbeC0FcG (ORCPT ); Tue, 27 Mar 2018 01:32:06 -0400 Received: from pug.e01.socionext.com (p14092-ipngnfx01kyoto.kyoto.ocn.ne.jp [153.142.97.92]) (authenticated) by conuserg-09.nifty.com with ESMTP id w2R5TaLu011947; Tue, 27 Mar 2018 14:29:51 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conuserg-09.nifty.com w2R5TaLu011947 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1522128592; bh=CY3e32fP7VlTo1A1pABM84pkB3a/uXldaQMydua0XXU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NR0YYPTcoaEI39sh3dWThbX6xTQ7VvO+903mnibBquvFzZ52X76jDl9c91xEU04PO ewwbb1wg72Eir2N33xsqzL2fXvypu7EEco6tk7XmMzCX40JWzIHlrB47VkKdHHL6tx id8CH+CB9QMB4LW4ILENuYw0IGJTVu9vyWBo8fHZEGgXhOwi+SImtuRazZ4AkaHAzX IAuBaHXaiG7aanTI+kdB08dAhgMSgwYCMbWjVqwOOHPQjmO3nG7leINGAFlLYSiFBL IOBlJwohbB0nrMuA7BFxC20IRl4UNbfTJX/wmLPMAnUE1uv35AAODmQ+0bY1KqCuyq ADivMHNSd4yHQ== X-Nifty-SrcIP: [153.142.97.92] From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: Sam Ravnborg , Linus Torvalds , Arnd Bergmann , Ulf Magnusson , Kees Cook , Thomas Gleixner , Greg Kroah-Hartman , Randy Dunlap , "Luis R . Rodriguez" , Nicolas Pitre , Masahiro Yamada , linux-kernel@vger.kernel.org, Ingo Molnar Subject: [PATCH v2 11/21] stack-protector: test compiler capability in Kconfig and drop AUTO mode Date: Tue, 27 Mar 2018 14:29:25 +0900 Message-Id: <1522128575-5326-12-git-send-email-yamada.masahiro@socionext.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1522128575-5326-1-git-send-email-yamada.masahiro@socionext.com> References: <1522128575-5326-1-git-send-email-yamada.masahiro@socionext.com> Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Move the test for -fstack-protector(-strong) option to Kconfig. If the compiler does not support the option, the corresponding menu is automatically hidden. If _STRONG is not supported, it will fall back to _REGULAR. If _REGULAR is not supported, it will be disabled. This means, _AUTO is implicitly handled by the dependency solver of Kconfig, hence removed. I also turned the 'choice' into only two boolean symbols. The use of 'choice' is not a good idea here, because all of all{yes,mod,no}config would choose the first visible value, while we want allnoconfig to disable as many features as possible. X86 has additional shell scripts in case the compiler supports the option, but generates broken code. I added CC_HAS_SANE_STACKPROTECTOR to test this. I had to add -m32 to gcc-x86_32-has-stack-protector.sh to make it work correctly. Signed-off-by: Masahiro Yamada --- Changes in v2: - Describe $(cc-option ...) directly in depends on context Makefile | 93 ++----------------------------- arch/Kconfig | 29 +++------- arch/x86/Kconfig | 8 ++- scripts/gcc-x86_32-has-stack-protector.sh | 7 +-- scripts/gcc-x86_64-has-stack-protector.sh | 5 -- 5 files changed, 22 insertions(+), 120 deletions(-) diff --git a/Makefile b/Makefile index 5c395ed..5cadffa 100644 --- a/Makefile +++ b/Makefile @@ -675,55 +675,11 @@ ifneq ($(CONFIG_FRAME_WARN),0) KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN}) endif -# This selects the stack protector compiler flag. Testing it is delayed -# until after .config has been reprocessed, in the prepare-compiler-check -# target. -ifdef CONFIG_CC_STACKPROTECTOR_AUTO - stackp-flag := $(call cc-option,-fstack-protector-strong,$(call cc-option,-fstack-protector)) - stackp-name := AUTO -else -ifdef CONFIG_CC_STACKPROTECTOR_REGULAR - stackp-flag := -fstack-protector - stackp-name := REGULAR -else -ifdef CONFIG_CC_STACKPROTECTOR_STRONG - stackp-flag := -fstack-protector-strong - stackp-name := STRONG -else - # If either there is no stack protector for this architecture or - # CONFIG_CC_STACKPROTECTOR_NONE is selected, we're done, and $(stackp-name) - # is empty, skipping all remaining stack protector tests. - # - # Force off for distro compilers that enable stack protector by default. - KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector) -endif -endif -endif -# Find arch-specific stack protector compiler sanity-checking script. -ifdef stackp-name -ifneq ($(stackp-flag),) - stackp-path := $(srctree)/scripts/gcc-$(SRCARCH)_$(BITS)-has-stack-protector.sh - stackp-check := $(wildcard $(stackp-path)) - # If the wildcard test matches a test script, run it to check functionality. - ifdef stackp-check - ifneq ($(shell $(CONFIG_SHELL) $(stackp-check) $(CC) $(KBUILD_CPPFLAGS) $(biarch)),y) - stackp-broken := y - endif - endif - ifndef stackp-broken - # If the stack protector is functional, enable code that depends on it. - KBUILD_CPPFLAGS += -DCONFIG_CC_STACKPROTECTOR - # Either we've already detected the flag (for AUTO) or we'll fail the - # build in the prepare-compiler-check rule (for specific flag). - KBUILD_CFLAGS += $(stackp-flag) - else - # We have to make sure stack protector is unconditionally disabled if - # the compiler is broken (in case we're going to continue the build in - # AUTO mode). - KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector) - endif -endif -endif +stackp-flags-y := -fno-stack-protector +stackp-flags-$(CONFIG_CC_STACKPROTECTOR) := -fstack-protector +stackp-flags-$(CONFIG_CC_STACKPROTECTOR_STRONG) := -fstack-protector-strong + +KBUILD_CFLAGS += $(stackp-flags-y) ifeq ($(cc-name),clang) KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) @@ -1092,7 +1048,7 @@ endif # prepare2 creates a makefile if using a separate output directory. # From this point forward, .config has been reprocessed, so any rules # that need to depend on updated CONFIG_* values can be checked here. -prepare2: prepare3 prepare-compiler-check outputmakefile asm-generic +prepare2: prepare3 outputmakefile asm-generic prepare1: prepare2 $(version_h) $(autoksyms_h) include/generated/utsrelease.h \ include/config/auto.conf @@ -1118,43 +1074,6 @@ uapi-asm-generic: PHONY += prepare-objtool prepare-objtool: $(objtool_target) -# Check for CONFIG flags that require compiler support. Abort the build -# after .config has been processed, but before the kernel build starts. -# -# For security-sensitive CONFIG options, we don't want to fallback and/or -# silently change which compiler flags will be used, since that leads to -# producing kernels with different security feature characteristics -# depending on the compiler used. (For example, "But I selected -# CC_STACKPROTECTOR_STRONG! Why did it build with _REGULAR?!") -PHONY += prepare-compiler-check -prepare-compiler-check: FORCE -# Make sure compiler supports requested stack protector flag. -ifdef stackp-name - # Warn about CONFIG_CC_STACKPROTECTOR_AUTO having found no option. - ifeq ($(stackp-flag),) - @echo CONFIG_CC_STACKPROTECTOR_$(stackp-name): \ - Compiler does not support any known stack-protector >&2 - else - # Fail if specifically requested stack protector is missing. - ifeq ($(call cc-option, $(stackp-flag)),) - @echo Cannot use CONFIG_CC_STACKPROTECTOR_$(stackp-name): \ - $(stackp-flag) not supported by compiler >&2 && exit 1 - endif - endif -endif -# Make sure compiler does not have buggy stack-protector support. If a -# specific stack-protector was requested, fail the build, otherwise warn. -ifdef stackp-broken - ifeq ($(stackp-name),AUTO) - @echo CONFIG_CC_STACKPROTECTOR_$(stackp-name): \ - $(stackp-flag) available but compiler is broken: disabling >&2 - else - @echo Cannot use CONFIG_CC_STACKPROTECTOR_$(stackp-name): \ - $(stackp-flag) available but compiler is broken >&2 && exit 1 - endif -endif - @: - # Generate some files # --------------------------------------------------------------------------- diff --git a/arch/Kconfig b/arch/Kconfig index 8e0d665..b42378d 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -535,13 +535,13 @@ config HAVE_CC_STACKPROTECTOR bool help An arch should select this symbol if: - - its compiler supports the -fstack-protector option - it has implemented a stack canary (e.g. __stack_chk_guard) -choice - prompt "Stack Protector buffer overflow detection" +config CC_STACKPROTECTOR + bool "Stack Protector buffer overflow detection" depends on HAVE_CC_STACKPROTECTOR - default CC_STACKPROTECTOR_AUTO + depends on $(cc-option -fstack-protector) + default y help This option turns on the "stack-protector" GCC feature. This feature puts, at the beginning of functions, a canary value on @@ -551,14 +551,6 @@ choice overwrite the canary, which gets detected and the attack is then neutralized via a kernel panic. -config CC_STACKPROTECTOR_NONE - bool "None" - help - Disable "stack-protector" GCC feature. - -config CC_STACKPROTECTOR_REGULAR - bool "Regular" - help Functions will have the stack-protector canary logic added if they have an 8-byte or larger character array on the stack. @@ -570,7 +562,10 @@ config CC_STACKPROTECTOR_REGULAR by about 0.3%. config CC_STACKPROTECTOR_STRONG - bool "Strong" + bool "Strong Stack Protector" + depends on CC_STACKPROTECTOR + depends on $(cc-option -fstack-protector-strong) + default y help Functions will have the stack-protector canary logic added in any of the following conditions: @@ -588,14 +583,6 @@ config CC_STACKPROTECTOR_STRONG about 20% of all kernel functions, which increases the kernel code size by about 2%. -config CC_STACKPROTECTOR_AUTO - bool "Automatic" - help - If the compiler supports it, the best available stack-protector - option will be chosen. - -endchoice - config LD_DEAD_CODE_DATA_ELIMINATION bool help diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 986fb0a..946bd9b 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -124,7 +124,7 @@ config X86 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64 select HAVE_ARCH_VMAP_STACK if X86_64 select HAVE_ARCH_WITHIN_STACK_FRAMES - select HAVE_CC_STACKPROTECTOR + select HAVE_CC_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR select HAVE_CMPXCHG_DOUBLE select HAVE_CMPXCHG_LOCAL select HAVE_CONTEXT_TRACKING if X86_64 @@ -340,6 +340,12 @@ config PGTABLE_LEVELS default 2 source "init/Kconfig" + +config CC_HAS_SANE_STACKPROTECTOR + bool + default $(success $srctree/scripts/gcc-x86_64-has-stack-protector.sh $CC) if 64BIT + default $(success $srctree/scripts/gcc-x86_32-has-stack-protector.sh $CC) + source "kernel/Kconfig.freezer" menu "Processor type and features" diff --git a/scripts/gcc-x86_32-has-stack-protector.sh b/scripts/gcc-x86_32-has-stack-protector.sh index 6b2aeef..f5c1194 100755 --- a/scripts/gcc-x86_32-has-stack-protector.sh +++ b/scripts/gcc-x86_32-has-stack-protector.sh @@ -1,9 +1,4 @@ #!/bin/sh # SPDX-License-Identifier: GPL-2.0 -echo "int foo(void) { char X[200]; return 3; }" | $* -S -x c -c -O0 -fstack-protector - -o - 2> /dev/null | grep -q "%gs" -if [ "$?" -eq "0" ] ; then - echo y -else - echo n -fi +echo "int foo(void) { char X[200]; return 3; }" | $* -S -x c -c -m32 -O0 -fstack-protector - -o - 2> /dev/null | grep -q "%gs" diff --git a/scripts/gcc-x86_64-has-stack-protector.sh b/scripts/gcc-x86_64-has-stack-protector.sh index 4a48bdc..3755af0 100755 --- a/scripts/gcc-x86_64-has-stack-protector.sh +++ b/scripts/gcc-x86_64-has-stack-protector.sh @@ -2,8 +2,3 @@ # SPDX-License-Identifier: GPL-2.0 echo "int foo(void) { char X[200]; return 3; }" | $* -S -x c -c -O0 -mcmodel=kernel -fno-PIE -fstack-protector - -o - 2> /dev/null | grep -q "%gs" -if [ "$?" -eq "0" ] ; then - echo y -else - echo n -fi