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authorSteven Rostedt <rostedt@goodmis.org>2009-08-05 22:00:14 -0400
committerSteven Rostedt <rostedt@goodmis.org>2009-08-05 22:45:07 -0400
commit3f6e968ef4e1d8d93d8a8505461b0e50a9e97ad8 (patch)
treeebce859414e81a677bb28b171673a47a5f8fdbfe /scripts/recordmcount.pl
parent464e85eb0e63096bd52e4c3e2a6fb8357fb95828 (diff)
downloadlinux-linaro-stable-3f6e968ef4e1d8d93d8a8505461b0e50a9e97ad8.tar.gz
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-xscripts/recordmcount.pl5
1 files changed, 4 insertions, 1 deletions
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index d29baa2e063a..4889c44d71b5 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;
}