objtool: Fix STACK_FRAME_NON_STANDARD macro checking for function symbols

Mathieu Desnoyers reported that the STACK_FRAME_NON_STANDARD macro
wasn't working with the lttng_filter_interpret_bytecode() function in
the lttng-modules code.

Usually the relocation created by STACK_FRAME_NON_STANDARD creates a
reference to a section symbol like this:

  Offset              Type            Value               Addend Name
  000000000000000000  X86_64_64       000000000000000000   +3136 .text

But in this case it created a reference to a function symbol:

  Offset              Type            Value               Addend Name
  000000000000000000  X86_64_64       0x00000000000003a0      +0 lttng_filter_interpret_bytecode

To be honest I have no idea what causes gcc to decide to do one over the
other.  But both are valid ELF, so add support for the function symbol.

Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: lttng-dev@lists.lttng.org
Link: http://lkml.kernel.org/r/9cee42843bc6d94e990a152e4e0319cfdf6756ef.1466023450.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index e8a1e69eb92c..25d803148f5c 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -122,10 +122,14 @@ static bool ignore_func(struct objtool_file *file, struct symbol *func)
 
         /* check for STACK_FRAME_NON_STANDARD */
         if (file->whitelist && file->whitelist->rela)
-                list_for_each_entry(rela, &file->whitelist->rela->rela_list, list)
-                        if (rela->sym->sec == func->sec &&
+                list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
+                        if (rela->sym->type == STT_SECTION &&
+                            rela->sym->sec == func->sec &&
                             rela->addend == func->offset)
                                 return true;
+                        if (rela->sym->type == STT_FUNC && rela->sym == func)
+                                return true;
+                }
 
         /* check if it has a context switching instruction */
         func_for_each_insn(file, func, insn)