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
recordmcount.pl, 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
code.
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 recordmcount.pl 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 $mcount_regex to only match on these.
Signed-off-by: David Daney <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Li Hong <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Ralf Baechle <[email protected]>
---
scripts/recordmcount.pl | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index f3c9c0a..0171060 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -326,7 +326,7 @@ if ($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\$";
}
--
1.6.6.1
On Fri, 2010-07-09 at 14:52 -0700, David Daney wrote:
> 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
> recordmcount.pl, 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
> code.
>
> 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 recordmcount.pl 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 $mcount_regex to only match on these.
>
I'd like to get an Acked-by from Ralf and Wu before pulling this.
Thanks,
-- Steve
> Signed-off-by: David Daney <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Li Hong <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Matt Fleming <[email protected]>
> Cc: Ralf Baechle <[email protected]>
> ---
> scripts/recordmcount.pl | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
> index f3c9c0a..0171060 100755
> --- a/scripts/recordmcount.pl
> +++ b/scripts/recordmcount.pl
> @@ -326,7 +326,7 @@ if ($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\$";
> }
On Fri, Jul 09, 2010 at 08:26:02PM -0400, Steven Rostedt wrote:
> I'd like to get an Acked-by from Ralf and Wu before pulling this.
I talked through this on irc with David and it is the right thing to do.
Acked-by: Ralf Baechle <[email protected]>
Ralf
On Fri, 2010-07-09 at 20:26 -0400, Steven Rostedt wrote:
>
> I'd like to get an Acked-by from Ralf and Wu before pulling this.
>
It is ok for me ;)
Acked-by: Wu Zhangjin <[email protected]>
Regards,
Wu Zhangjin
Commit-ID: a484e54fae891703cbe1c9ec1b536605f11f5482
Gitweb: http://git.kernel.org/tip/a484e54fae891703cbe1c9ec1b536605f11f5482
Author: David Daney <[email protected]>
AuthorDate: Fri, 9 Jul 2010 14:52:05 -0700
Committer: Steven Rostedt <[email protected]>
CommitDate: Thu, 22 Jul 2010 14:55:43 -0400
tracing: Fix $mcount_regex for MIPS in recordmcount.pl
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
recordmcount.pl, 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
code.
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 recordmcount.pl 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 $mcount_regex to only match on these.
Acked-by: Ralf Baechle <[email protected]>
Acked-by: Wu Zhangjin <[email protected]>
Signed-off-by: David Daney <[email protected]>
LKML-Reference: <[email protected]>
Cc: Li Hong <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Matt Fleming <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
---
scripts/recordmcount.pl | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index f3c9c0a..0171060 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -326,7 +326,7 @@ if ($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\$";
}