Re: [PATCH 4/5] tracing: Add synthetic event error logging

[Tom Zanussi]

Hi Masami,

On Sat, 2020-10-10 at 23:57 +0900, Masami Hiramatsu wrote:
> On Fri,  9 Oct 2020 10:17:10 -0500
> Tom Zanussi <zanussi@xxxxxxxxxx> wrote:
> 
> > Add support for synthetic event error logging, which entails adding
> > a
> > logging function for it, a way to save the synthetic event command,
> > and a set of specific synthetic event parse error strings and
> > handling.
> 
> Thanks for fixing this. But it seems that the INVALID_TYPE error
> position is not correct.
> 
> /sys/kernel/debug/tracing # echo "myevent chr arg" >>
> synthetic_events 
> sh: write error: Invalid argument
> /sys/kernel/debug/tracing # cat error_log 
> [ 1354.611660] synthetic_events: error: Invalid type
>   Command: myevent chr arg 
>                        ^
> 
> If the type is invalid, it should point "chr" instead of "arg".
> If you add a syntax error testcase as same as kprobe_events, you can
> check the error position too.
> 

Right, it's using name where it should be using type.  Will fix in the
next version.

Thanks,

Tom

> Thank you,
> 
> > 
> > Signed-off-by: Tom Zanussi <zanussi@xxxxxxxxxx>
> > ---
> >  kernel/trace/trace_events_synth.c | 114
> > +++++++++++++++++++++++++++++-
> >  1 file changed, 112 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_synth.c
> > b/kernel/trace/trace_events_synth.c
> > index 8c9d6e464da0..ce4cae5cfd47 100644
> > --- a/kernel/trace/trace_events_synth.c
> > +++ b/kernel/trace/trace_events_synth.c
> > @@ -20,6 +20,53 @@
> >  
> >  #include "trace_synth.h"
> >  
> > +#undef ERRORS
> > +#define ERRORS	\
> > +	C(BAD_NAME,		"Illegal name"),		\
> > +	C(CMD_INCOMPLETE,	"Incomplete command"),		\
> > +	C(EVENT_EXISTS,		"Event already exists"),	\
> > +	C(TOO_MANY_FIELDS,	"Too many fields"),		\
> > +	C(INCOMPLETE_TYPE,	"Incomplete type"),		\
> > +	C(INVALID_TYPE,		"Invalid type"),		\
> > +	C(INVALID_FIELD,	"Invalid field"),		\
> > +	C(CMD_TOO_LONG,		"Command too long"),
> > +
> > +#undef C
> > +#define C(a, b)		SYNTH_ERR_##a
> > +
> > +enum { ERRORS };
> > +
> > +#undef C
> > +#define C(a, b)		b
> > +
> > +static const char *err_text[] = { ERRORS };
> > +
> > +static char last_cmd[MAX_FILTER_STR_VAL];
> > +
> > +static int errpos(const char *str)
> > +{
> > +	return err_pos(last_cmd, str);
> > +}
> > +
> > +static void last_cmd_set(char *str)
> > +{
> > +	if (!str)
> > +		return;
> > +
> > +	strncat(last_cmd, str, MAX_FILTER_STR_VAL - 1);
> > +}
> > +
> > +static void synth_err(u8 err_type, u8 err_pos)
> > +{
> > +	tracing_log_err(NULL, "synthetic_events", last_cmd, err_text,
> > +			err_type, err_pos);
> > +}
> > +
> > +static void synth_err_clear(void)
> > +{
> > +	last_cmd[0] = '\0';
> > +}
> > +
> >  static int create_synth_event(int argc, const char **argv);
> >  static int synth_event_show(struct seq_file *m, struct dyn_event
> > *ev);
> >  static int synth_event_release(struct dyn_event *ev);
> > @@ -545,8 +592,10 @@ static struct synth_field
> > *parse_synth_field(int argc, const char **argv,
> >  		field_type++;
> >  
> >  	if (!strcmp(field_type, "unsigned")) {
> > -		if (argc < 3)
> > +		if (argc < 3) {
> > +			synth_err(SYNTH_ERR_INCOMPLETE_TYPE,
> > errpos(field_type));
> >  			return ERR_PTR(-EINVAL);
> > +		}
> >  		prefix = "unsigned ";
> >  		field_type = argv[1];
> >  		field_name = argv[2];
> > @@ -573,6 +622,7 @@ static struct synth_field
> > *parse_synth_field(int argc, const char **argv,
> >  		goto free;
> >  	}
> >  	if (!is_good_name(field->name)) {
> > +		synth_err(SYNTH_ERR_BAD_NAME, errpos(field_name));
> >  		ret = -EINVAL;
> >  		goto free;
> >  	}
> > @@ -601,6 +651,7 @@ static struct synth_field
> > *parse_synth_field(int argc, const char **argv,
> >  
> >  	size = synth_field_size(field->type);
> >  	if (size < 0) {
> > +		synth_err(SYNTH_ERR_INVALID_TYPE, errpos(field->name));
> >  		ret = -EINVAL;
> >  		goto free;
> >  	} else if (size == 0) {
> > @@ -621,6 +672,7 @@ static struct synth_field
> > *parse_synth_field(int argc, const char **argv,
> >  			field->is_dynamic = true;
> >  			size = sizeof(u64);
> >  		} else {
> > +			synth_err(SYNTH_ERR_INVALID_TYPE, errpos(field-
> > >name));
> >  			ret = -EINVAL;
> >  			goto free;
> >  		}
> > @@ -1098,12 +1150,64 @@ int synth_event_gen_cmd_array_start(struct
> > dynevent_cmd *cmd, const char *name,
> >  }
> >  EXPORT_SYMBOL_GPL(synth_event_gen_cmd_array_start);
> >  
> > +static int cmdstr_append(char *buf, const char *str, int
> > *remaining)
> > +{
> > +	int len = strlen(str);
> > +
> > +	if (len + 1 >= *remaining) {
> > +		synth_err(SYNTH_ERR_CMD_TOO_LONG, 0);
> > +		return -EINVAL;
> > +	}
> > +
> > +	strcat(buf, str);
> > +	strcat(buf, " ");
> > +	*remaining -= len + 1;
> > +
> > +	return 0;
> > +}
> > +
> > +static int save_cmdstr(int argc, const char *name, const char
> > **argv)
> > +{
> > +	int i, ret, remaining = MAX_DYNEVENT_CMD_LEN;
> > +	char *buf;
> > +
> > +	synth_err_clear();
> > +
> > +	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
> > +	if (!buf)
> > +		return -ENOMEM;
> > +
> > +	ret = cmdstr_append(buf, name, &remaining);
> > +	if (ret) {
> > +		kfree(buf);
> > +		return ret;
> > +	}
> > +
> > +	for (i = 0; i < argc; i++) {
> > +		ret = cmdstr_append(buf, argv[i], &remaining);
> > +		if (ret) {
> > +			kfree(buf);
> > +			return ret;
> > +		}
> > +	}
> > +
> > +	last_cmd_set(buf);
> > +
> > +	kfree(buf);
> > +
> > +	return ret;
> > +}
> > +
> >  static int __create_synth_event(int argc, const char *name, const
> > char **argv)
> >  {
> >  	struct synth_field *field, *fields[SYNTH_FIELDS_MAX];
> >  	struct synth_event *event = NULL;
> >  	int i, consumed = 0, n_fields = 0, ret = 0;
> >  
> > +	ret = save_cmdstr(argc, name, argv);
> > +	if (ret)
> > +		return ret;
> > +
> >  	/*
> >  	 * Argument syntax:
> >  	 *  - Add synthetic event: <event_name> field[;field] ...
> > @@ -1111,18 +1215,22 @@ static int __create_synth_event(int argc,
> > const char *name, const char **argv)
> >  	 *      where 'field' = type field_name
> >  	 */
> >  
> > -	if (name[0] == '\0' || argc < 1)
> > +	if (name[0] == '\0' || argc < 1) {
> > +		synth_err(SYNTH_ERR_CMD_INCOMPLETE, 0);
> >  		return -EINVAL;
> > +	}
> >  
> >  	mutex_lock(&event_mutex);
> >  
> >  	if (!is_good_name(name)) {
> > +		synth_err(SYNTH_ERR_BAD_NAME, errpos(name));
> >  		ret = -EINVAL;
> >  		goto out;
> >  	}
> >  
> >  	event = find_synth_event(name);
> >  	if (event) {
> > +		synth_err(SYNTH_ERR_EVENT_EXISTS, errpos(name));
> >  		ret = -EEXIST;
> >  		goto out;
> >  	}
> > @@ -1131,6 +1239,7 @@ static int __create_synth_event(int argc,
> > const char *name, const char **argv)
> >  		if (strcmp(argv[i], ";") == 0)
> >  			continue;
> >  		if (n_fields == SYNTH_FIELDS_MAX) {
> > +			synth_err(SYNTH_ERR_TOO_MANY_FIELDS, 0);
> >  			ret = -EINVAL;
> >  			goto err;
> >  		}
> > @@ -1145,6 +1254,7 @@ static int __create_synth_event(int argc,
> > const char *name, const char **argv)
> >  	}
> >  
> >  	if (i < argc && strcmp(argv[i], ";") != 0) {
> > +		synth_err(SYNTH_ERR_INVALID_FIELD, errpos(argv[i]));
> >  		ret = -EINVAL;
> >  		goto err;
> >  	}
> > -- 
> > 2.17.1
> > 
> 
>