Re: [PATCH] perf probe: support signedness casting

[Naohiro Aota <Naohiro.Aota@hgst.com>]

2016-08-05 (金) の 18:10 +0900 に Masami Hiramatsu さんは書きました:
> On Fri, 5 Aug 2016 14:33:53 +0900
> Naohiro Aota <naohiro.aota@hgst.com> wrote:
> 
> > 
> > Perf-probe detects a variable's type and use the detected type to
> > add new
> > probe. Then, kprobes prints its variable in hexadecimal format if
> > the
> > variable is unsigned and prints in decimal if it is signed.
> > 
> > We sometimes want to see unsigned variable in decimal format (e.g.
> > sector_t or size_t). In that case, we need to investigate
> > variable's
> > size manually to specify just signedness.
> > 
> > This patch add signedness casting support. By specifying "s" or "u"
> > as a
> > type, perf-probe will investigate variable size as usual and use
> > the specified signedness.
> OK, I could understand what the patch does from code. Please add an
> example, and update tools/perf/Documentation/perf-probe.txt too.

Thanks for the review. I'm posting updated patch with type
descriptions.

> Thank you,
> 
> > 
> > 
> > Signed-off-by: Naohiro Aota <naohiro.aota@hgst.com>
> > ---
> >  tools/perf/util/probe-finder.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/perf/util/probe-finder.c
> > b/tools/perf/util/probe-finder.c
> > index f2d9ff0..5c290c6 100644
> > --- a/tools/perf/util/probe-finder.c
> > +++ b/tools/perf/util/probe-finder.c
> > @@ -297,10 +297,13 @@ static int convert_variable_type(Dwarf_Die
> > *vr_die,
> >  	char sbuf[STRERR_BUFSIZE];
> >  	int bsize, boffs, total;
> >  	int ret;
> > +	char sign;
> >  
> >  	/* TODO: check all types */
> > -	if (cast && strcmp(cast, "string") != 0) {
> > +	if (cast && strcmp(cast, "string") != 0 &&
> > +	    strcmp(cast, "s") != 0 && strcmp(cast, "u") != 0) {
> >  		/* Non string type is OK */
> > +		/* and respect signedness cast */
> >  		tvar->type = strdup(cast);
> >  		return (tvar->type == NULL) ? -ENOMEM : 0;
> >  	}
> > @@ -361,6 +364,13 @@ static int convert_variable_type(Dwarf_Die
> > *vr_die,
> >  		return (tvar->type == NULL) ? -ENOMEM : 0;
> >  	}
> >  
> > +	if (cast && (strcmp(cast, "u") == 0))
> > +		sign = 'u';
> > +	else if (cast && (strcmp(cast, "s") == 0))
> > +		sign = 's';
> > +	else
> > +		sign = die_is_signed_type(&type) ? 's' : 'u';
> > +
> >  	ret = dwarf_bytesize(&type);
> >  	if (ret <= 0)
> >  		/* No size ... try to use default type */
> > @@ -373,8 +383,7 @@ static int convert_variable_type(Dwarf_Die
> > *vr_die,
> >  			dwarf_diename(&type),
> > MAX_BASIC_TYPE_BITS);
> >  		ret = MAX_BASIC_TYPE_BITS;
> >  	}
> > -	ret = snprintf(buf, 16, "%c%d",
> > -		       die_is_signed_type(&type) ? 's' : 'u',
> > ret);
> > +	ret = snprintf(buf, 16, "%c%d", sign, ret);
> >  
> >  formatted:
> >  	if (ret < 0 || ret >= 16) {
> > -- 
> > 2.7.3
> > 
> 
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