From 3f6e968ef4e1d8d93d8a8505461b0e50a9e97ad8 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 5 Aug 2009 22:00:14 -0400 Subject: tracing: do not use functions starting with .L in recordmcount.pl On Wed, 5 Aug 2009, Ingo Molnar wrote: > * Dave Airlie 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 LKML-Reference: Signed-off-by: Steven Rostedt --- scripts/recordmcount.pl | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'scripts/recordmcount.pl') 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 () { $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; } -- cgit v1.2.3