Date:	Tue, 26 Apr 2016 23:40:47 +0900
From:	Masami Hiramatsu <mhiramat@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Hemant Kumar <hemant@...ux.vnet.ibm.com>,
	Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
Subject: Re: [PATCH perf/core v4 01/19] perf probe: Use strbuf for making
 strings

On Tue, 26 Apr 2016 10:36:57 -0300
Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> Em Tue, Apr 26, 2016 at 06:02:11PM +0900, Masami Hiramatsu escreveu:
> > From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> > 
> > Replace many fixed-length char array with strbuf to
> > stringify perf_probe_event and probe_trace_event etc.
> 
> Sure you want to do that? From time to time I try to reduce the strbuf
> usage, not grow it :-\

Aah, I got what you want.

> 
> That is one of the last users of xrealloc(), via that ALLOC_GROW()
> thing.

Hmm I'm not sure what you considering, memory usage? or code reducing?
I also would like to remove e_snprintf() use in perf probe by replacing
with strbuf functions. I'd like to find better way.

Thank you,

> 
> - Arnaldo
>  
> > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> > 
> > ---
> > Changes in v4:
> >  - Update for the latest kernel.
> >  - Remove "probe-event.c" from title and body, because
> >    this also changes probe-finder.c too :)
> > 
> > Changes in v3:
> >  - Remove unneeded strbuf_release(). (Thanks Namhyung!)
> > 
> > Changes in v2:
> >  - Make perf_probe_event__sprintf() simpler.
> > ---
> >  tools/perf/util/probe-event.c  |  246 ++++++++++++++--------------------------
> >  tools/perf/util/probe-event.h  |    2 
> >  tools/perf/util/probe-finder.c |   14 +-
> >  3 files changed, 93 insertions(+), 169 deletions(-)
> > 
> > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > index 8319fbb..148af81 100644
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -1618,69 +1618,51 @@ out:
> >  }
> >  
> >  /* Compose only probe arg */
> > -int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf, size_t len)
> > +char *synthesize_perf_probe_arg(struct perf_probe_arg *pa)
> >  {
> >  	struct perf_probe_arg_field *field = pa->field;
> > -	int ret;
> > -	char *tmp = buf;
> > +	struct strbuf buf;
> > +	char *ret;
> >  
> > +	strbuf_init(&buf, 64);
> >  	if (pa->name && pa->var)
> > -		ret = e_snprintf(tmp, len, "%s=%s", pa->name, pa->var);
> > +		strbuf_addf(&buf, "%s=%s", pa->name, pa->var);
> >  	else
> > -		ret = e_snprintf(tmp, len, "%s", pa->name ? pa->name : pa->var);
> > -	if (ret <= 0)
> > -		goto error;
> > -	tmp += ret;
> > -	len -= ret;
> > +		strbuf_addstr(&buf, pa->name ?: pa->var);
> >  
> >  	while (field) {
> >  		if (field->name[0] == '[')
> > -			ret = e_snprintf(tmp, len, "%s", field->name);
> > +			strbuf_addstr(&buf, field->name);
> >  		else
> > -			ret = e_snprintf(tmp, len, "%s%s",
> > -					 field->ref ? "->" : ".", field->name);
> > -		if (ret <= 0)
> > -			goto error;
> > -		tmp += ret;
> > -		len -= ret;
> > +			strbuf_addf(&buf, "%s%s", field->ref ? "->" : ".",
> > +				    field->name);
> >  		field = field->next;
> >  	}
> >  
> > -	if (pa->type) {
> > -		ret = e_snprintf(tmp, len, ":%s", pa->type);
> > -		if (ret <= 0)
> > -			goto error;
> > -		tmp += ret;
> > -		len -= ret;
> > -	}
> > +	if (pa->type)
> > +		strbuf_addf(&buf, ":%s", pa->type);
> > +
> > +	ret = strbuf_detach(&buf, NULL);
> >  
> > -	return tmp - buf;
> > -error:
> > -	pr_debug("Failed to synthesize perf probe argument: %d\n", ret);
> >  	return ret;
> >  }
> >  
> >  /* Compose only probe point (not argument) */
> >  static char *synthesize_perf_probe_point(struct perf_probe_point *pp)
> >  {
> > -	char *buf, *tmp;
> > -	char offs[32] = "", line[32] = "", file[32] = "";
> > -	int ret, len;
> > -
> > -	buf = zalloc(MAX_CMDLEN);
> > -	if (buf == NULL) {
> > -		ret = -ENOMEM;
> > -		goto error;
> > -	}
> > -	if (pp->offset) {
> > -		ret = e_snprintf(offs, 32, "+%lu", pp->offset);
> > -		if (ret <= 0)
> > -			goto error;
> > -	}
> > -	if (pp->line) {
> > -		ret = e_snprintf(line, 32, ":%d", pp->line);
> > -		if (ret <= 0)
> > -			goto error;
> > +	struct strbuf buf;
> > +	char *tmp;
> > +	int len;
> > +
> > +	strbuf_init(&buf, 64);
> > +	if (pp->function) {
> > +		strbuf_addstr(&buf, pp->function);
> > +		if (pp->offset)
> > +			strbuf_addf(&buf, "+%lu", pp->offset);
> > +		else if (pp->line)
> > +			strbuf_addf(&buf, ":%d", pp->line);
> > +		else if (pp->retprobe)
> > +			strbuf_addstr(&buf, "%return");
> >  	}
> >  	if (pp->file) {
> >  		tmp = pp->file;
> > @@ -1689,25 +1671,12 @@ static char *synthesize_perf_probe_point(struct perf_probe_point *pp)
> >  			tmp = strchr(pp->file + len - 30, '/');
> >  			tmp = tmp ? tmp + 1 : pp->file + len - 30;
> >  		}
> > -		ret = e_snprintf(file, 32, "@%s", tmp);
> > -		if (ret <= 0)
> > -			goto error;
> > +		strbuf_addf(&buf, "@%s", tmp);
> > +		if (!pp->function && pp->line)
> > +			strbuf_addf(&buf, ":%d", pp->line);
> >  	}
> >  
> > -	if (pp->function)
> > -		ret = e_snprintf(buf, MAX_CMDLEN, "%s%s%s%s%s", pp->function,
> > -				 offs, pp->retprobe ? "%return" : "", line,
> > -				 file);
> > -	else
> > -		ret = e_snprintf(buf, MAX_CMDLEN, "%s%s", file, line);
> > -	if (ret <= 0)
> > -		goto error;
> > -
> > -	return buf;
> > -error:
> > -	pr_debug("Failed to synthesize perf probe point: %d\n", ret);
> > -	free(buf);
> > -	return NULL;
> > +	return strbuf_detach(&buf, NULL);
> >  }
> >  
> >  #if 0
> > @@ -1736,45 +1705,30 @@ char *synthesize_perf_probe_command(struct perf_probe_event *pev)
> >  #endif
> >  
> >  static int __synthesize_probe_trace_arg_ref(struct probe_trace_arg_ref *ref,
> > -					     char **buf, size_t *buflen,
> > -					     int depth)
> > +					    struct strbuf *buf, int depth)
> >  {
> > -	int ret;
> >  	if (ref->next) {
> >  		depth = __synthesize_probe_trace_arg_ref(ref->next, buf,
> > -							 buflen, depth + 1);
> > +							 depth + 1);
> >  		if (depth < 0)
> >  			goto out;
> >  	}
> > -
> > -	ret = e_snprintf(*buf, *buflen, "%+ld(", ref->offset);
> > -	if (ret < 0)
> > -		depth = ret;
> > -	else {
> > -		*buf += ret;
> > -		*buflen -= ret;
> > -	}
> > +	strbuf_addf(buf, "%+ld(", ref->offset);
> >  out:
> >  	return depth;
> > -
> >  }
> >  
> >  static int synthesize_probe_trace_arg(struct probe_trace_arg *arg,
> > -				       char *buf, size_t buflen)
> > +				      struct strbuf *buf)
> >  {
> >  	struct probe_trace_arg_ref *ref = arg->ref;
> > -	int ret, depth = 0;
> > -	char *tmp = buf;
> > +	int depth = 0;
> >  
> >  	/* Argument name or separator */
> >  	if (arg->name)
> > -		ret = e_snprintf(buf, buflen, " %s=", arg->name);
> > +		strbuf_addf(buf, " %s=", arg->name);
> >  	else
> > -		ret = e_snprintf(buf, buflen, " ");
> > -	if (ret < 0)
> > -		return ret;
> > -	buf += ret;
> > -	buflen -= ret;
> > +		strbuf_addch(buf, ' ');
> >  
> >  	/* Special case: @XXX */
> >  	if (arg->value[0] == '@' && arg->ref)
> > @@ -1782,60 +1736,41 @@ static int synthesize_probe_trace_arg(struct probe_trace_arg *arg,
> >  
> >  	/* Dereferencing arguments */
> >  	if (ref) {
> > -		depth = __synthesize_probe_trace_arg_ref(ref, &buf,
> > -							  &buflen, 1);
> > +		depth = __synthesize_probe_trace_arg_ref(ref, buf, 1);
> >  		if (depth < 0)
> >  			return depth;
> >  	}
> >  
> >  	/* Print argument value */
> >  	if (arg->value[0] == '@' && arg->ref)
> > -		ret = e_snprintf(buf, buflen, "%s%+ld", arg->value,
> > -				 arg->ref->offset);
> > +		strbuf_addf(buf, "%s%+ld", arg->value, arg->ref->offset);
> >  	else
> > -		ret = e_snprintf(buf, buflen, "%s", arg->value);
> > -	if (ret < 0)
> > -		return ret;
> > -	buf += ret;
> > -	buflen -= ret;
> > +		strbuf_addstr(buf, arg->value);
> >  
> >  	/* Closing */
> > -	while (depth--) {
> > -		ret = e_snprintf(buf, buflen, ")");
> > -		if (ret < 0)
> > -			return ret;
> > -		buf += ret;
> > -		buflen -= ret;
> > -	}
> > +	while (depth--)
> > +		strbuf_addch(buf, ')');
> >  	/* Print argument type */
> > -	if (arg->type) {
> > -		ret = e_snprintf(buf, buflen, ":%s", arg->type);
> > -		if (ret <= 0)
> > -			return ret;
> > -		buf += ret;
> > -	}
> > +	if (arg->type)
> > +		strbuf_addf(buf, ":%s", arg->type);
> >  
> > -	return buf - tmp;
> > +	return 0;
> >  }
> >  
> >  char *synthesize_probe_trace_command(struct probe_trace_event *tev)
> >  {
> >  	struct probe_trace_point *tp = &tev->point;
> > -	char *buf;
> > -	int i, len, ret;
> > -
> > -	buf = zalloc(MAX_CMDLEN);
> > -	if (buf == NULL)
> > -		return NULL;
> > -
> > -	len = e_snprintf(buf, MAX_CMDLEN, "%c:%s/%s ", tp->retprobe ? 'r' : 'p',
> > -			 tev->group, tev->event);
> > -	if (len <= 0)
> > -		goto error;
> > +	struct strbuf buf;
> > +	char *ret = NULL;
> > +	int i;
> >  
> >  	/* Uprobes must have tp->module */
> >  	if (tev->uprobes && !tp->module)
> > -		goto error;
> > +		return NULL;
> > +
> > +	strbuf_init(&buf, 32);
> > +	strbuf_addf(&buf, "%c:%s/%s ", tp->retprobe ? 'r' : 'p',
> > +		    tev->group, tev->event);
> >  	/*
> >  	 * If tp->address == 0, then this point must be a
> >  	 * absolute address uprobe.
> > @@ -1849,34 +1784,23 @@ char *synthesize_probe_trace_command(struct probe_trace_event *tev)
> >  
> >  	/* Use the tp->address for uprobes */
> >  	if (tev->uprobes)
> > -		ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s:0x%lx",
> > -				 tp->module, tp->address);
> > +		strbuf_addf(&buf, "%s:0x%lx", tp->module, tp->address);
> >  	else if (!strncmp(tp->symbol, "0x", 2))
> >  		/* Absolute address. See try_to_find_absolute_address() */
> > -		ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s%s0x%lx",
> > -				 tp->module ?: "", tp->module ? ":" : "",
> > -				 tp->address);
> > +		strbuf_addf(&buf, "%s%s0x%lx", tp->module ?: "",
> > +			    tp->module ? ":" : "", tp->address);
> >  	else
> > -		ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s%s%s+%lu",
> > -				 tp->module ?: "", tp->module ? ":" : "",
> > -				 tp->symbol, tp->offset);
> > -
> > -	if (ret <= 0)
> > -		goto error;
> > -	len += ret;
> > +		strbuf_addf(&buf, "%s%s%s+%lu", tp->module ?: "",
> > +			    tp->module ? ":" : "", tp->symbol, tp->offset);
> >  
> > -	for (i = 0; i < tev->nargs; i++) {
> > -		ret = synthesize_probe_trace_arg(&tev->args[i], buf + len,
> > -						  MAX_CMDLEN - len);
> > -		if (ret <= 0)
> > +	for (i = 0; i < tev->nargs; i++)
> > +		if (synthesize_probe_trace_arg(&tev->args[i], &buf) < 0)
> >  			goto error;
> > -		len += ret;
> > -	}
> >  
> > -	return buf;
> > +	ret = strbuf_detach(&buf, NULL);
> >  error:
> > -	free(buf);
> > -	return NULL;
> > +	strbuf_release(&buf);
> > +	return ret;
> >  }
> >  
> >  static int find_perf_probe_point_from_map(struct probe_trace_point *tp,
> > @@ -1958,7 +1882,7 @@ static int convert_to_perf_probe_point(struct probe_trace_point *tp,
> >  static int convert_to_perf_probe_event(struct probe_trace_event *tev,
> >  			       struct perf_probe_event *pev, bool is_kprobe)
> >  {
> > -	char buf[64] = "";
> > +	struct strbuf buf = STRBUF_INIT;
> >  	int i, ret;
> >  
> >  	/* Convert event/group name */
> > @@ -1981,9 +1905,9 @@ static int convert_to_perf_probe_event(struct probe_trace_event *tev,
> >  		if (tev->args[i].name)
> >  			pev->args[i].name = strdup(tev->args[i].name);
> >  		else {
> > -			ret = synthesize_probe_trace_arg(&tev->args[i],
> > -							  buf, 64);
> > -			pev->args[i].name = strdup(buf);
> > +			strbuf_init(&buf, 32);
> > +			ret = synthesize_probe_trace_arg(&tev->args[i], &buf);
> > +			pev->args[i].name = strbuf_detach(&buf, NULL);
> >  		}
> >  		if (pev->args[i].name == NULL && ret >= 0)
> >  			ret = -ENOMEM;
> > @@ -2161,37 +2085,37 @@ static int perf_probe_event__sprintf(const char *group, const char *event,
> >  				     const char *module,
> >  				     struct strbuf *result)
> >  {
> > -	int i, ret;
> > -	char buf[128];
> > -	char *place;
> > +	int i;
> > +	char *buf;
> >  
> > -	/* Synthesize only event probe point */
> > -	place = synthesize_perf_probe_point(&pev->point);
> > -	if (!place)
> > -		return -EINVAL;
> > +	if (asprintf(&buf, "%s:%s", group, event) < 0)
> > +		return -errno;
> > +	strbuf_addf(result, "  %-20s (on ", buf);
> > +	free(buf);
> >  
> > -	ret = e_snprintf(buf, 128, "%s:%s", group, event);
> > -	if (ret < 0)
> > -		goto out;
> > +	/* Synthesize only event probe point */
> > +	buf = synthesize_perf_probe_point(&pev->point);
> > +	if (!buf)
> > +		return -ENOMEM;
> > +	strbuf_addstr(result, buf);
> > +	free(buf);
> >  
> > -	strbuf_addf(result, "  %-20s (on %s", buf, place);
> >  	if (module)
> >  		strbuf_addf(result, " in %s", module);
> >  
> >  	if (pev->nargs > 0) {
> >  		strbuf_add(result, " with", 5);
> >  		for (i = 0; i < pev->nargs; i++) {
> > -			ret = synthesize_perf_probe_arg(&pev->args[i],
> > -							buf, 128);
> > -			if (ret < 0)
> > -				goto out;
> > +			buf = synthesize_perf_probe_arg(&pev->args[i]);
> > +			if (!buf)
> > +				return -ENOMEM;
> >  			strbuf_addf(result, " %s", buf);
> > +			free(buf);
> >  		}
> >  	}
> >  	strbuf_addch(result, ')');
> > -out:
> > -	free(place);
> > -	return ret;
> > +
> > +	return 0;
> >  }
> >  
> >  /* Show an event */
> > diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
> > index e54e7b0..e220962 100644
> > --- a/tools/perf/util/probe-event.h
> > +++ b/tools/perf/util/probe-event.h
> > @@ -120,7 +120,7 @@ int parse_probe_trace_command(const char *cmd, struct probe_trace_event *tev);
> >  /* Events to command string */
> >  char *synthesize_perf_probe_command(struct perf_probe_event *pev);
> >  char *synthesize_probe_trace_command(struct probe_trace_event *tev);
> > -int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf, size_t len);
> > +char *synthesize_perf_probe_arg(struct perf_probe_arg *pa);
> >  
> >  /* Check the perf_probe_event needs debuginfo */
> >  bool perf_probe_event_need_dwarf(struct perf_probe_event *pev);
> > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > index b3bd0fb..9f68875 100644
> > --- a/tools/perf/util/probe-finder.c
> > +++ b/tools/perf/util/probe-finder.c
> > @@ -553,7 +553,7 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
> >  static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
> >  {
> >  	Dwarf_Die vr_die;
> > -	char buf[32], *ptr;
> > +	char *buf, *ptr;
> >  	int ret = 0;
> >  
> >  	/* Copy raw parameters */
> > @@ -563,13 +563,13 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
> >  	if (pf->pvar->name)
> >  		pf->tvar->name = strdup(pf->pvar->name);
> >  	else {
> > -		ret = synthesize_perf_probe_arg(pf->pvar, buf, 32);
> > -		if (ret < 0)
> > -			return ret;
> > +		buf = synthesize_perf_probe_arg(pf->pvar);
> > +		if (!buf)
> > +			return -ENOMEM;
> >  		ptr = strchr(buf, ':');	/* Change type separator to _ */
> >  		if (ptr)
> >  			*ptr = '_';
> > -		pf->tvar->name = strdup(buf);
> > +		pf->tvar->name = buf;
> >  	}
> >  	if (pf->tvar->name == NULL)
> >  		return -ENOMEM;
> > @@ -1334,8 +1334,8 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
> >  			if (ret2 == 0) {
> >  				strlist__add(vl->vars,
> >  					strbuf_detach(&buf, NULL));
> > -			}
> > -			strbuf_release(&buf);
> > +			} else
> > +				strbuf_release(&buf);
> >  		}
> >  	}
> >  


-- 
Masami Hiramatsu <mhiramat@...nel.org>

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