Re: [PATCHv2 5/8] perf probe powerpc: Allow matching against dot symbols

["Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>]

On 2015/03/12 05:30PM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Dec 15, 2014 at 08:20:35PM +0530, Naveen N. Rao escreveu:
> > Allow perf probe to work on powerpc ABIv1 without the need to specify
> > the leading dot '.' for functions. 'perf probe do_fork' works with this
> > patch.
> > 
> > Introduce HAVE_ARCH_SYMBOL_HANDLING to indicate need for special
> > handling of symbols. In this patch, we override probe_function_filter()
> > on powerpc to account for dot symbols.
> 
> This one looks better, does arch specific stuff in tools/perf/arch,
> good, some nits below.
> 
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> > ---
> > Changes from the previous patchset:
> > Introduced arch helper to override the way probe function filter works.
> > 
> >  tools/perf/arch/powerpc/Makefile            |  1 +
> >  tools/perf/arch/powerpc/util/sym-handling.c | 28 ++++++++++++++++++++++++++++
> >  tools/perf/config/Makefile                  |  1 +
> >  tools/perf/util/probe-event.c               | 10 +++++-----
> >  tools/perf/util/probe-event.h               |  5 +++++
> >  5 files changed, 40 insertions(+), 5 deletions(-)
> >  create mode 100644 tools/perf/arch/powerpc/util/sym-handling.c
> > 
> > diff --git a/tools/perf/arch/powerpc/Makefile b/tools/perf/arch/powerpc/Makefile
> > index 6f7782b..1c3d435 100644
> > --- a/tools/perf/arch/powerpc/Makefile
> > +++ b/tools/perf/arch/powerpc/Makefile
> > @@ -3,4 +3,5 @@ PERF_HAVE_DWARF_REGS := 1
> >  LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/dwarf-regs.o
> >  LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/skip-callchain-idx.o
> >  endif
> > +LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/sym-handling.o
> >  LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/header.o
> > diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c
> > new file mode 100644
> > index 0000000..0a77825
> > --- /dev/null
> > +++ b/tools/perf/arch/powerpc/util/sym-handling.c
> > @@ -0,0 +1,28 @@
> > +/*
> > + * Special symbol handling for PowerPC:
> > + * - Handle dot symbols on ABIv1
> > + *
> > + * Copyright (C) 2014 Naveen N Rao, IBM Corporation.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; either version
> > + * 2 of the License, or (at your option) any later version.
> > + */
> > +
> > +#include "map.h"
> > +#include "symbol.h"
> > +#include "probe-event.h"
> > +
> > +int probe_function_filter(struct map *map __maybe_unused, struct symbol *sym)
> > +{
> > +	if (sym->binding == STB_GLOBAL || sym->binding == STB_LOCAL) {
> > +		if ((strcmp(looking_function_name, sym->name) == 0) ||
> > +		    (sym->name[0] == '.' && looking_function_name[0] != '.' &&
> > +		     strcmp(looking_function_name, sym->name+1) == 0)) {
> > +			num_matched_functions++;
> > +			return 0;
> > +		}
> > +	}
> > +	return 1;
> > +}
> > diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
> > index 5d4b039..35cf934 100644
> > --- a/tools/perf/config/Makefile
> > +++ b/tools/perf/config/Makefile
> > @@ -383,6 +383,7 @@ ifeq ($(ARCH),powerpc)
> >    ifndef NO_DWARF
> >      CFLAGS += -DHAVE_SKIP_CALLCHAIN_IDX
> >    endif
> > +  CFLAGS += -DHAVE_ARCH_SYMBOL_HANDLING
> 
> 
> Dunno about this naming, looks too general: SYMBOL_HANDLING, but can't
> come to some better one now, anyone?
> 
> >  endif
> >  
> >  ifndef NO_LIBUNWIND
> > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > index 74b7fef..7eb9b27 100644
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -50,6 +50,8 @@
> >  #define PERFPROBE_GROUP "probe"
> >  
> >  bool probe_event_dry_run;	/* Dry run flag */
> > +char *looking_function_name;
> > +int num_matched_functions;
> >  
> >  #define semantic_error(msg ...) pr_err("Semantic error :" msg)
> >  
> > @@ -2210,11 +2212,8 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
> >  	return ret;
> >  }
> >  
> > -static char *looking_function_name;
> > -static int num_matched_functions;
> > -
> > -static int probe_function_filter(struct map *map __maybe_unused,
> > -				      struct symbol *sym)
> > +#ifndef HAVE_ARCH_SYMBOL_HANDLING
> > +int probe_function_filter(struct map *map __maybe_unused, struct symbol *sym)
> >  {
> >  	if ((sym->binding == STB_GLOBAL || sym->binding == STB_LOCAL) &&
> >  	    strcmp(looking_function_name, sym->name) == 0) {
> > @@ -2223,6 +2222,7 @@ static int probe_function_filter(struct map *map __maybe_unused,
> >  	}
> >  	return 1;
> >  }
> > +#endif /* HAVE_ARCH_SYMBOL_HANDLING */
> 
> Can't we do something like providing a weak function and let the linked
> to its work? I guess we have cases like this in tools/ already. I.e. not
> using the ifndef block. Minor nit tho.

That sounds like a good idea. I will move these over to use __weak 
functions.

> 
> >  
> >  #define strdup_or_goto(str, label)	\
> >  	({ char *__p = strdup(str); if (!__p) goto label; __p; })
> > diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
> > index e01e994..8564451 100644
> > --- a/tools/perf/util/probe-event.h
> > +++ b/tools/perf/util/probe-event.h
> > @@ -7,6 +7,8 @@
> >  #include "strfilter.h"
> >  
> >  extern bool probe_event_dry_run;
> > +extern char *looking_function_name;
> > +extern int num_matched_functions;
> 
> >  
> >  /* kprobe-tracer and uprobe-tracer tracing point */
> >  struct probe_trace_point {
> > @@ -136,6 +138,9 @@ extern int show_available_vars(struct perf_probe_event *pevs, int npevs,
> >  extern int show_available_funcs(const char *module, struct strfilter *filter,
> >  				bool user);
> >  
> > +extern int probe_function_filter(struct map *map __maybe_unused,
> > +					struct symbol *sym);
> > +
> 
> Please do not prefix function declarations with 'extern', even when we
> have one just before, its not needed, patches removing the existing ones
> would be accepted.

Sure.

- Naveen

> 
> >  /* Maximum index number of event-name postfix */
> >  #define MAX_EVENT_INDEX	1024
> >  
> > -- 
> > 2.1.3
>