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author | Steven Rostedt <rostedt@goodmis.org> | 2009-08-05 22:00:14 -0400 |
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committer | Steven Rostedt <rostedt@goodmis.org> | 2009-08-05 22:45:07 -0400 |
commit | 3f6e968ef4e1d8d93d8a8505461b0e50a9e97ad8 (patch) | |
tree | ebce859414e81a677bb28b171673a47a5f8fdbfe /scripts/recordmcount.pl | |
parent | 464e85eb0e63096bd52e4c3e2a6fb8357fb95828 (diff) | |
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tracing: do not use functions starting with .L in recordmcount.pl
On Wed, 5 Aug 2009, Ingo Molnar wrote:
> * Dave Airlie <airlied@gmail.com> wrote:
>
> > Hey,
> >
> > So I spent 3-4 hrs today (I'm stupid yes) tracking down a .o
> > breakage by blaming rawhide gcc/binutils as I was using make
> > V=1and seeing only the compiler chain running,
>
> Hm, is this that powerpc related build bug you just reported?
Well we tracked it down and it is powerpc64 specific.
Seems that in drivers/hwmon/lm93.c there's a function called:
LM93_IN_FROM_REG()
But PPC64 has function descriptors and the real function names (the ones
you see in objdump) start with a '.'. Thus this in objdump you have:
Disassembly of section .text:
0000000000000000 <.LM93_IN_FROM_REG>:
0: 7c 08 02 a6 mflr r0
4: fb 81 ff e0 std r28,-32(r1)
The function name used is .LM93_IN_FROM_REG. But gcc considers symbols
that start with ".L" as a special symbol that is used inside the assembly
stage.
The nm passed into recordmcount uses the --synthetic option which shows
the ".L" symbols (my runs outside of the build did not include the
--synthetic option, so my older patch worked). We see the function as a
local.
Now to capture all the locations that use "mcount" we need to have a
reference to link into the object file a list of mcount callers. We need a
reference that will not disappear. We try to use a global function and if
that does not work, we use a local function as a reference. But to relink
the section back into the object, we need to make it global. In this case,
we run objcopy using --globalize-symbol and --localize-symbol to convert
the symbol into a global symbol, link the mcount list, then convert it
back to a local symbol.
This works great except for this case. .L* symbols can not be converted
into a global symbol, and the mcount section referencing it will remain
unresolved.
Reported-by: Dave Airlie <airlied@gmail.com>
LKML-Reference: <alpine.DEB.2.00.0908052011590.5010@gandalf.stny.rr.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'scripts/recordmcount.pl')
-rwxr-xr-x | scripts/recordmcount.pl | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl index d29baa2..4889c44 100755 --- a/scripts/recordmcount.pl +++ b/scripts/recordmcount.pl @@ -414,7 +414,10 @@ while (<IN>) { $offset = hex $1; } else { # if we already have a function, and this is weak, skip it - if (!defined($ref_func) && !defined($weak{$text})) { + if (!defined($ref_func) && !defined($weak{$text}) && + # PPC64 can have symbols that start with .L and + # gcc considers these special. Don't use them! + $text !~ /^\.L/) { $ref_func = $text; $offset = hex $1; } |