linux-kernel - Re: [PATCH v9 20/22] tracing: Remove restriction on string position in hist trigger keys

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Tue, 21 Jul 2015 09:15:36 -0500
From:	Tom Zanussi <tom.zanussi@...ux.intel.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	rostedt@...dmis.org, daniel.wagner@...-carit.de,
	masami.hiramatsu.pt@...achi.com, josh@...htriplett.org,
	andi@...stfloor.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 20/22] tracing: Remove restriction on string position
 in hist trigger keys

On Sun, 2015-07-19 at 22:31 +0900, Namhyung Kim wrote:
> On Thu, Jul 16, 2015 at 12:22:53PM -0500, Tom Zanussi wrote:
> > If we assume the maximum size for a string field, we don't have to
> > worry about its position.  Since we only allow two keys in a compound
> > key and having more than one string key in a given compound key
> > doesn't make much sense anyway, trading a bit of extra space instead
> > of introducing an arbitrary restriction makes more sense.
> > 
> > We also need to use the event field size for static strings when
> > copying the contents, otherwise we get random garbage in the key.
> > 
> > Finally, rearrange the code without changing any functionality by
> > moving the compound key updating code into a separate function.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> 
> Looks good to me.  Just a nitpick below..
> 
> 
> > ---
> >  kernel/trace/trace_events_hist.c | 65 +++++++++++++++++++++++-----------------
> >  1 file changed, 37 insertions(+), 28 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index 67fffee..4ba7645 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> > @@ -508,8 +508,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
> >  			goto out;
> >  		}
> >  
> > -		if (is_string_field(field)) /* should be last key field */
> > -			key_size = HIST_KEY_SIZE_MAX - key_offset;
> > +		if (is_string_field(field))
> > +			key_size = MAX_FILTER_STR_VAL;
> >  		else
> >  			key_size = field->size;
> >  	}
> > @@ -781,9 +781,36 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
> >  	}
> >  }
> >  
> > +static inline void add_to_key(char *compound_key, void *key,
> > +			      struct hist_field *key_field, void *rec)
> > +{
> > +	size_t size = key_field->size;
> > +
> > +	if (key_field->flags & HIST_FIELD_STRING) {
> > +		struct ftrace_event_field *field;
> > +
> > +		/* ensure NULL-termination */
> > +		size--;
> 
> This is unnecessary since the size value will be updated below anyway.
> I think it's enough just to move the comment to ...
> 
> 
> > +
> > +		field = key_field->field;
> > +		if (field->filter_type == FILTER_DYN_STRING)
> > +			size = *(u32 *)(rec + field->offset) >> 16;
> > +		else if (field->filter_type == FILTER_PTR_STRING)
> > +			size = strlen(key);
> > +		else if (field->filter_type == FILTER_STATIC_STRING)
> > +			size = field->size;
> > +
> 
> ... here. :)
> 

Yep, makes sense, will do.

Tom

> > +		if (size > key_field->size - 1)
> > +			size = key_field->size - 1;
> > +	}
> > +
> > +	memcpy(compound_key + key_field->offset, key, size);
> > +}
> > +
> >  static void event_hist_trigger(struct event_trigger_data *data, void *rec)
> >  {
> >  	struct hist_trigger_data *hist_data = data->private_data;
> > +	bool use_compound_key = (hist_data->n_keys > 1);
> >  	unsigned long entries[HIST_STACKTRACE_DEPTH];
> >  	char compound_key[HIST_KEY_SIZE_MAX];
> >  	struct stack_trace stacktrace;
> > @@ -798,8 +825,7 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec)
> >  		return;
> >  	}
> >  
> > -	if (hist_data->n_keys > 1)
> > -		memset(compound_key, 0, hist_data->key_size);
> > +	memset(compound_key, 0, hist_data->key_size);
> >  
> >  	for (i = hist_data->n_vals; i < hist_data->n_fields; i++) {
> >  		key_field = hist_data->fields[i];
> > @@ -816,35 +842,18 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec)
> >  			key = entries;
> >  		} else {
> >  			field_contents = key_field->fn(key_field, rec);
> > -			if (key_field->flags & HIST_FIELD_STRING)
> > +			if (key_field->flags & HIST_FIELD_STRING) {
> >  				key = (void *)field_contents;
> > -			else
> > +				use_compound_key = true;
> > +			} else
> >  				key = (void *)&field_contents;
> > -
> > -			if (hist_data->n_keys > 1) {
> > -				/* ensure NULL-termination */
> > -				size_t size = key_field->size - 1;
> > -
> > -				if (key_field->flags & HIST_FIELD_STRING) {
> > -					struct ftrace_event_field *field;
> > -
> > -					field = key_field->field;
> > -					if (field->filter_type == FILTER_DYN_STRING)
> > -						size = *(u32 *)(rec + field->offset) >> 16;
> > -					else if (field->filter_type == FILTER_PTR_STRING)
> > -						size = strlen(key);
> > -
> > -					if (size > key_field->size - 1)
> > -						size = key_field->size - 1;
> > -				}
> > -
> > -				memcpy(compound_key + key_field->offset, key,
> > -				       size);
> > -			}
> >  		}
> > +
> > +		if (use_compound_key)
> > +			add_to_key(compound_key, key, key_field, rec);
> >  	}
> >  
> > -	if (hist_data->n_keys > 1)
> > +	if (use_compound_key)
> >  		key = compound_key;
> >  
> >  	elt = tracing_map_insert(hist_data->map, key);
> > -- 
> > 1.9.3
> > 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/