Re: [PATCH v7 13/14] perf callchain: Support x86 target platform

[Hekuang]

å 2016/6/1 16:40, Jiri Olsa åé:
> On Tue, May 31, 2016 at 11:19:11AM +0000, He Kuang wrote:
>
> SNIP
>
> > diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
> > index e183390..5774317 100644
> > --- a/tools/perf/util/unwind-libunwind.c
> > +++ b/tools/perf/util/unwind-libunwind.c
> > @@ -5,6 +5,7 @@
> >   #include "arch/common.h"
> >   
> >   struct unwind_libunwind_ops __weak *local_unwind_libunwind_ops;
> > +struct unwind_libunwind_ops __weak *x86_32_unwind_libunwind_ops;
> >   
> >   void unwind__register_ops(struct thread *thread,
> >   			  struct unwind_libunwind_ops *ops)
> > @@ -30,7 +31,13 @@ int unwind__prepare_access(struct thread *thread, struct map *map)
> >   			 dso_type == DSO__TYPE_64BIT, map->dso->name);
> >   
> >   	arch = normalize_arch(thread->mg->machine->env->arch);
> > -	pr_debug("unwind: target platform=%s\n", arch);
> > +
> > +	if (!strcmp(arch, "x86"))
> > +		if (dso_type != DSO__TYPE_64BIT)
> > +			ops = x86_32_unwind_libunwind_ops;
> > +
> > +	if (!ops)
> > +		pr_err("unwind: target platform=%s is not supported\n", arch);
> how could ops become NULL in here? it starts with local_unwind_libunwind_ops
> I dont think this check is needed in here

x86_32_unwind_libunwind_ops is a null pointer when x86_32
libunwind is not supported.

There's a weak defination if CONFIG_LIBUNWIND_X86 is not set.

   struct unwind_libunwind_ops __weak *x86_32_unwind_libunwind_ops;

In this case, ops is null and "x86_32 is not supported" error
message is showed up.

> jirka