Thread (36 messages) 36 messages, 3 authors, 2012-02-20

[04/28] perf tools: Fix perf stack to non executable on x86_64

From: Greg KH <gregkh@linuxfoundation.org>
Date: 2012-02-17 01:00:24
Also in: lkml

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Olsa <redacted>

commit 7a0153ee15575a4d07b5da8c96b79e0b0fd41a12 upstream.

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

The reason was that above object are assembler sourced and is 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 object, with all
flags disabled, thus omiting this object from linker stack flags decision.

Problem introduced in:

  $ git describe ea7872b
  v2.6.37-rc2-19-gea7872b

Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=783570
Reported-by: Clark Williams <redacted>
Acked-by: Eric Dumazet <redacted>
Cc: Corey Ashford <redacted>
Cc: Ingo Molnar <redacted>
Cc: Paul Mackerras <redacted>
Cc: Peter Zijlstra <redacted>
Link: http://lkml.kernel.org/r/1328100848-5630-1-git-send-email-jolsa@redhat.com
Signed-off-by: Jiri Olsa <redacted>
[ committer note: Backported fix to perf/urgent (3.3-rc2+) ]
Signed-off-by: Arnaldo Carvalho de Melo <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 tools/perf/bench/mem-memcpy-x86-64-asm.S |    6 ++++++
 1 file changed, 6 insertions(+)
--- a/tools/perf/bench/mem-memcpy-x86-64-asm.S
+++ b/tools/perf/bench/mem-memcpy-x86-64-asm.S
@@ -1,2 +1,8 @@
 
 #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

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