linux-kernel - [PATCH] perf, tool: Fix perf stack to non executable on x86

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Date:	Wed,  1 Feb 2012 13:54:08 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	acme@...hat.com, a.p.zijlstra@...llo.nl, mingo@...e.hu,
	paulus@...ba.org, cjashfor@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>
Subject: [PATCH] perf, tool: Fix perf stack to non executable on x86_64

By adding following objects:
  bench/mem-memset-x86-64-asm.o
  bench/mem-memcpy-x86-64-asm.o
the x86_64 perf binary ended up with executable stack.

The reason was that above objects are assembler sourced and
are missing the GNU-stack note section. In such case the linker
assumes that the final binary should not be restricted at all
and mark the stack as RWX.

Adding section ".note.GNU-stack" definition to mentioned objects,
with all flags disabled, thus omiting those objects from linker
stack flags decision.

Signed-off-by: Jiri Olsa <jolsa@...hat.com>
---
 tools/perf/bench/mem-memcpy-x86-64-asm.S |    7 +++++++
 tools/perf/bench/mem-memset-x86-64-asm.S |    7 +++++++
 2 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/tools/perf/bench/mem-memcpy-x86-64-asm.S b/tools/perf/bench/mem-memcpy-x86-64-asm.S
index a20780b..a6c8909 100644
--- a/tools/perf/bench/mem-memcpy-x86-64-asm.S
+++ b/tools/perf/bench/mem-memcpy-x86-64-asm.S
@@ -4,3 +4,10 @@
 #define Lmemcpy_c globl memcpy_c; memcpy_c
 #define Lmemcpy_c_e globl memcpy_c_e; memcpy_c_e
 #include "../../../arch/x86/lib/memcpy_64.S"
+
+/*
+ * 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/bench/mem-memset-x86-64-asm.S b/tools/perf/bench/mem-memset-x86-64-asm.S
index cb92170..9e5af89 100644
--- a/tools/perf/bench/mem-memset-x86-64-asm.S
+++ b/tools/perf/bench/mem-memset-x86-64-asm.S
@@ -4,3 +4,10 @@
 #define Lmemset_c globl memset_c; memset_c
 #define Lmemset_c_e globl memset_c_e; memset_c_e
 #include "../../../arch/x86/lib/memset_64.S"
+
+/*
+ * 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
-- 
1.7.1
--
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