linux-kernel - Re: [PATCH] perf script: Show binary offsets for userspace addr

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Date:   Wed, 27 Oct 2021 20:58:55 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Lexi Shao <shaolexi@...wei.com>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, mark.rutland@....com,
        peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        qiuxi1@...wei.com, nixiaoming@...wei.com, wangbing6@...wei.com
Subject: Re: [PATCH] perf script: Show binary offsets for userspace addr

Em Wed, Oct 20, 2021 at 03:24:19PM +0200, Jiri Olsa escreveu:
> On Tue, Oct 19, 2021 at 03:24:17PM +0800, Lexi Shao wrote:
> > Show binary offsets for userspace addr with map in perf script output
> > with callchain.
> > 
> > In commit 19610184693c("perf script: Show virtual addresses instead of
> > offsets"), the addr shown in perf script output with callchain is changed
> > from binary offsets to virtual address to fix the incorrectness when
> > displaying symbol offset.
> > 
> > This is inconvenient in scenario that the binary is stripped and
> > symbol cannot be resolved. If someone wants to further resolve symbols for
> > specific binaries later, he would need an extra step to translate virtual
> > address to binary offset with mapping information recorded in perf.data,
> > which can be difficult for people not familiar with perf.
> > 
> > This patch modifies function sample__fprintf_callchain to print binary
> > offset for userspace addr with dsos, and virtual address otherwise. It
> > does not affect symbol offset calculation so symoff remains correct.
> > 
> > Before applying this patch:
> > test  1512    78.711307:     533129 cycles:
> > 	aaaae0da07f4 [unknown] (/tmp/test)
> > 	aaaae0da0704 [unknown] (/tmp/test)
> > 	ffffbe9f7ef4 __libc_start_main+0xe4 (/lib64/libc-2.31.so)
> > 
> > After this patch:
> > test  1519   111.330127:     406953 cycles:
> > 	7f4 [unknown] (/tmp/test)
> > 	704 [unknown] (/tmp/test)
> > 	20ef4 __libc_start_main+0xe4 (/lib64/libc-2.31.so)
> > 
> > Fixes: 19610184693c("perf script: Show virtual addresses instead of offsets")
> > 
> > Signed-off-by: Lexi Shao <shaolexi@...wei.com>
> 
> makes sense to me
> 
> Acked-/Tested-by Jiri Olsa <jolsa@...hat.com>

Thanks, applied.

- Arnaldo

 
> should we have a way to display these callchain detail in perf report output as well?
> 
> thanks,
> jirka
> 
> > ---
> >  tools/perf/util/evsel_fprintf.c | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/perf/util/evsel_fprintf.c b/tools/perf/util/evsel_fprintf.c
> > index bfedd7b23521..8c2ea8001329 100644
> > --- a/tools/perf/util/evsel_fprintf.c
> > +++ b/tools/perf/util/evsel_fprintf.c
> > @@ -11,6 +11,7 @@
> >  #include "strlist.h"
> >  #include "symbol.h"
> >  #include "srcline.h"
> > +#include "dso.h"
> >  
> >  static int comma_fprintf(FILE *fp, bool *first, const char *fmt, ...)
> >  {
> > @@ -144,12 +145,17 @@ int sample__fprintf_callchain(struct perf_sample *sample, int left_alignment,
> >  			if (print_arrow && !first)
> >  				printed += fprintf(fp, " <-");
> >  
> > -			if (print_ip)
> > -				printed += fprintf(fp, "%c%16" PRIx64, s, node->ip);
> > -
> >  			if (map)
> >  				addr = map->map_ip(map, node->ip);
> >  
> > +			if (print_ip) {
> > +				/* Show binary offset for userspace addr */
> > +				if (map && !map->dso->kernel)
> > +					printed += fprintf(fp, "%c%16" PRIx64, s, addr);
> > +				else
> > +					printed += fprintf(fp, "%c%16" PRIx64, s, node->ip);
> > +			}
> > +
> >  			if (print_sym) {
> >  				printed += fprintf(fp, " ");
> >  				node_al.addr = addr;
> > -- 
> > 2.12.3
> > 

-- 

- Arnaldo