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Date: Wed, 19 Dec 2018 14:16:31 -0600
From: Tom Zanussi <zanussi@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: tglx@...utronix.de, mhiramat@...nel.org, namhyung@...nel.org,
vedang.patel@...el.com, bigeasy@...utronix.de,
joel@...lfernandes.org, mathieu.desnoyers@...icios.com,
julia@...com, linux-kernel@...r.kernel.org,
linux-rt-users@...r.kernel.org
Subject: Re: [PATCH 2/7] tracing: Change strlen to sizeof for hist trigger
static strings
On Wed, 2018-12-19 at 13:46 -0600, Tom Zanussi wrote:
> Hi Steve,
>
> On Wed, 2018-12-19 at 14:40 -0500, Steven Rostedt wrote:
> > On Tue, 18 Dec 2018 14:33:21 -0600
> > Tom Zanussi <zanussi@...nel.org> wrote:
> >
> > > From: Tom Zanussi <tom.zanussi@...ux.intel.com>
> > >
> > > There's no need to use strlen() for static strings when the
> > > length
> > > is
> > > already known, so update trace_events_hist.c with sizeof() for
> > > those
> > > cases.
> > >
> > > Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> > > ---
> > > kernel/trace/trace_events_hist.c | 38 +++++++++++++++++++-------
> > > --
> > > ----------
> > > 1 file changed, 19 insertions(+), 19 deletions(-)
> > >
> > > diff --git a/kernel/trace/trace_events_hist.c
> > > b/kernel/trace/trace_events_hist.c
> > > index d29bf8a8e1dd..25d06b3ae1f6 100644
> > > --- a/kernel/trace/trace_events_hist.c
> > > +++ b/kernel/trace/trace_events_hist.c
> > > @@ -507,7 +507,7 @@ static int synth_field_string_size(char
> > > *type)
> > > start = strstr(type, "char[");
> > > if (start == NULL)
> > > return -EINVAL;
> > > - start += strlen("char[");
> > > + start += sizeof("char[") - 1;
> > >
> > > end = strchr(type, ']');
> > > if (!end || end < start)
> > > @@ -1843,8 +1843,8 @@ static int parse_action(char *str, struct
> > > hist_trigger_attrs *attrs)
> > > if (attrs->n_actions >= HIST_ACTIONS_MAX)
> > > return ret;
> > >
> > > - if ((strncmp(str, "onmatch(", strlen("onmatch(")) == 0)
> > > ||
> > > - (strncmp(str, "onmax(", strlen("onmax(")) == 0)) {
> > > + if ((strncmp(str, "onmatch(", sizeof("onmatch(") - 1) ==
> > > 0) ||
> > > + (strncmp(str, "onmax(", sizeof("onmax(") - 1) == 0))
> > > {
> > > attrs->action_str[attrs->n_actions] =
> > > kstrdup(str,
> > > GFP_KERNEL);
> > > if (!attrs->action_str[attrs->n_actions]) {
> > > ret = -ENOMEM;
> > > @@ -1861,34 +1861,34 @@ static int parse_assignment(char *str,
> > > struct hist_trigger_attrs *attrs)
> > > {
> > > int ret = 0;
> > >
> > > - if ((strncmp(str, "key=", strlen("key=")) == 0) ||
> > > - (strncmp(str, "keys=", strlen("keys=")) == 0)) {
> > > + if ((strncmp(str, "key=", sizeof("key=") - 1) == 0) ||
> > > + (strncmp(str, "keys=", sizeof("keys=") - 1) == 0)) {
> > > attrs->keys_str = kstrdup(str, GFP_KERNEL);
> >
> > I'll apply this as is, but since there's a lot of these, I wonder
> > if
> > we
> > should make a marcro for this:
> >
> > #define strcmp_const(str, str_const) strncmp(str, str_const,
> > sizeof(str_const) - 1)
> >
> > ?
> >
> > This would help prevent bugs due to typos and bad cut and paste.
> >
>
> Yeah, I had considered it but wasn't sure it was worth it. Since
> you're suggesting it is, I can send another patch on top of these, or
> feel free if you want to too. ;-)
>
How's this?
[PATCH] tracing: Introduce and use strcmp_const() for hist triggers
Provide a new strcmp_const() macro and make use of it instead of the
longer and more error-prone strncmp(str, "str", sizeof("str") - 1).
Idea-and-macro-by: Steve Rostedt <rostedt@...dmis.org>
Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
---
kernel/trace/trace_events_hist.c | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index c5448c103770..aaf0d2ac4aab 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -22,6 +22,9 @@
#define STR_VAR_LEN_MAX 32 /* must be multiple of sizeof(u64) */
+#define strcmp_const(str, str_const) \
+ strncmp(str, str_const, sizeof(str_const) - 1)
+
struct hist_field;
typedef u64 (*hist_field_fn_t) (struct hist_field *field,
@@ -1881,8 +1884,8 @@ static int parse_action(char *str, struct hist_trigger_attrs *attrs)
if (attrs->n_actions >= HIST_ACTIONS_MAX)
return ret;
- if ((strncmp(str, "onmatch(", sizeof("onmatch(") - 1) == 0) ||
- (strncmp(str, "onmax(", sizeof("onmax(") - 1) == 0)) {
+ if ((strcmp_const(str, "onmatch(") == 0) ||
+ (strcmp_const(str, "onmax(") == 0)) {
attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
if (!attrs->action_str[attrs->n_actions]) {
ret = -ENOMEM;
@@ -1899,34 +1902,34 @@ static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
{
int ret = 0;
- if ((strncmp(str, "key=", sizeof("key=") - 1) == 0) ||
- (strncmp(str, "keys=", sizeof("keys=") - 1) == 0)) {
+ if ((strcmp_const(str, "key=") == 0) ||
+ (strcmp_const(str, "keys=") == 0)) {
attrs->keys_str = kstrdup(str, GFP_KERNEL);
if (!attrs->keys_str) {
ret = -ENOMEM;
goto out;
}
- } else if ((strncmp(str, "val=", sizeof("val=") - 1) == 0) ||
- (strncmp(str, "vals=", sizeof("vals=") - 1) == 0) ||
- (strncmp(str, "values=", sizeof("values=") - 1) == 0)) {
+ } else if ((strcmp_const(str, "val=") == 0) ||
+ (strcmp_const(str, "vals=") == 0) ||
+ (strcmp_const(str, "values=") == 0)) {
attrs->vals_str = kstrdup(str, GFP_KERNEL);
if (!attrs->vals_str) {
ret = -ENOMEM;
goto out;
}
- } else if (strncmp(str, "sort=", sizeof("sort=") - 1) == 0) {
+ } else if (strcmp_const(str, "sort=") == 0) {
attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
if (!attrs->sort_key_str) {
ret = -ENOMEM;
goto out;
}
- } else if (strncmp(str, "name=", sizeof("name=") - 1) == 0) {
+ } else if (strcmp_const(str, "name=") == 0) {
attrs->name = kstrdup(str, GFP_KERNEL);
if (!attrs->name) {
ret = -ENOMEM;
goto out;
}
- } else if (strncmp(str, "clock=", sizeof("clock=") - 1) == 0) {
+ } else if (strcmp_const(str, "clock=") == 0) {
strsep(&str, "=");
if (!str) {
ret = -EINVAL;
@@ -1939,7 +1942,7 @@ static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
ret = -ENOMEM;
goto out;
}
- } else if (strncmp(str, "size=", sizeof("size=") - 1) == 0) {
+ } else if (strcmp_const(str, "size=") == 0) {
int map_bits = parse_map_size(str);
if (map_bits < 0) {
@@ -3558,7 +3561,7 @@ static struct action_data *onmax_parse(char *str)
if (!onmax_fn_name || !str)
goto free;
- if (strncmp(onmax_fn_name, "save", sizeof("save") - 1) == 0) {
+ if (strcmp_const(onmax_fn_name, "save") == 0) {
char *params = strsep(&str, ")");
if (!params) {
@@ -4346,7 +4349,7 @@ static int parse_actions(struct hist_trigger_data *hist_data)
for (i = 0; i < hist_data->attrs->n_actions; i++) {
str = hist_data->attrs->action_str[i];
- if (strncmp(str, "onmatch(", sizeof("onmatch(") - 1) == 0) {
+ if (strcmp_const(str, "onmatch(") == 0) {
char *action_str = str + sizeof("onmatch(") - 1;
data = onmatch_parse(tr, action_str);
@@ -4355,7 +4358,7 @@ static int parse_actions(struct hist_trigger_data *hist_data)
break;
}
data->fn = action_trace;
- } else if (strncmp(str, "onmax(", sizeof("onmax(") - 1) == 0) {
+ } else if (strcmp_const(str, "onmax(") == 0) {
char *action_str = str + sizeof("onmax(") - 1;
data = onmax_parse(action_str);
--
2.14.1
> Tom
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