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[PATCH] tracing: Fix $mcount_regex for MIPS.

Subject: [PATCH] tracing: Fix $mcount_regex for MIPS.
From: David Daney <>
Date: Fri, 9 Jul 2010 14:52:05 -0700
Cc:,, David Daney <>, Li Hong <>, Ingo Molnar <>, Matt Fleming <>, Ralf Baechle <>
Original-recipient: rfc822;
I found this issue in a locally patched 2.6.32.x, current kernels have
moved the offending code to an __init function which is skipped by, so the bug is not currently being exercised.
However, I think the patch is still a good idea, to avoid future
problems if _mcount were to ever have its address taken in normal

This is what I originally saw:

    Although arch/mips/kernel/ftrace.c is built without -pg, and thus
    contains no calls to _mcount, it does use the address of _mcount
    in ftrace_make_nop().  This was causing relocations to be emitted
    for _mcount which erronously took to be _mcount
    call sites.  The result was that the text of ftrace_make_nop()
    would be patched with garbage leading to a system crash.

In non-module code, all _mcount call sites will have R_MIPS_26
relocations, so we restrict $mcount_regex to only match on these.

Signed-off-by: David Daney <>
Cc: Steven Rostedt <>
Cc: Li Hong <>
Cc: Ingo Molnar <>
Cc: Matt Fleming <>
Cc: Ralf Baechle <>
 scripts/ |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/scripts/ b/scripts/
index f3c9c0a..0171060 100755
--- a/scripts/
+++ b/scripts/
@@ -326,7 +326,7 @@ if ($arch eq "x86_64") {
     #                    14: R_MIPS_NONE *ABS*
     #   18:   00020021        nop
     if ($is_module eq "0") {
-           $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
+           $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
     } else {
            $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";

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