From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753143AbaD0QvV (ORCPT ); Sun, 27 Apr 2014 12:51:21 -0400 Received: from mail-ee0-f43.google.com ([74.125.83.43]:54281 "EHLO mail-ee0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752252AbaD0QvU (ORCPT ); Sun, 27 Apr 2014 12:51:20 -0400 From: Mathias Krause To: Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo Cc: linux-kernel@vger.kernel.org, Mathias Krause , Jiri Olsa Subject: [PATCH v2] perf x86: Fix perf to use non-executable stack, again Date: Sun, 27 Apr 2014 18:51:05 +0200 Message-Id: <1398617466-22749-1-git-send-email-minipli@googlemail.com> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org arch/x86/tests/regs_load.S is missing the linker note about the stack requirements, therefore making the linker fall back to an executable stack. As this object gets linked against the final perf binary, it'll needlessly end up with an executable stack. Fix this by adding the appropriate linker note. Also add a global linker flag to prevent future regressions, as suggested by Jiri. This way perf won't get an executable stack even if we fail to add the .GNU-stack linker note to future assembler files. Though, doing so might create regressions the other way around, when (statically) linking against libraries needing an executable stack. But, apparently, regressing in that direction is wanted as it is an indicator of poor code quality -- or just missing linker notes. Fixes: 3c8b06f981 ("perf tests x86: Introduce perf_regs_load function") Acked-by: Ingo Molnar Signed-off-by: Mathias Krause Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa --- tools/perf/arch/x86/tests/regs_load.S | 8 +++++++- tools/perf/config/Makefile | 4 ++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/tools/perf/arch/x86/tests/regs_load.S b/tools/perf/arch/x86/tests/regs_load.S index 99167bf644..60875d5c55 100644 --- a/tools/perf/arch/x86/tests/regs_load.S +++ b/tools/perf/arch/x86/tests/regs_load.S @@ -1,4 +1,3 @@ - #include #define AX 0 @@ -90,3 +89,10 @@ ENTRY(perf_regs_load) ret ENDPROC(perf_regs_load) #endif + +/* + * We need to provide note.GNU-stack section, saying that we want + * NOT executable stack. Otherwise the final linking will assume that + * the ELF stack should not be restricted at all and set it RWX. + */ +.section .note.GNU-stack,"",@progbits diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile index ee21fa95eb..d529291287 100644 --- a/tools/perf/config/Makefile +++ b/tools/perf/config/Makefile @@ -109,6 +109,10 @@ CFLAGS += -Wall CFLAGS += -Wextra CFLAGS += -std=gnu99 +# Enforce a non-executable stack, as we may regress (again) in the future by +# adding assembler files missing the .GNU-stack linker note. +LDFLAGS += -Wl,-z,noexecstack + EXTLIBS = -lelf -lpthread -lrt -lm -ldl ifneq ($(OUTPUT),) -- 1.7.10.4