Re: [Intel-gfx] [PATCH v6 17/57] dyndbg: validate class FOO by checking with module

Jason Baron
2022-09-12T13:39:00Z

On 9/4/22 17:40, Jim Cromie wrote:
> Add module-to-class validation:
>
> #> echo class DRM_UT_KMS +p > /proc/dynamic_debug/control
>
> If a query has "class FOO", then ddebug_find_valid_class(), called
> from ddebug_change(), requires that FOO is known to module X,
> otherwize the query is skipped entirely for X. This protects each
> module's class-space, other than the default:31.
>
> The authors' choice of FOO is highly selective, giving isolation
> and/or coordinated sharing of FOOs. For example, only DRM modules
> should know and respond to DRM_UT_KMS.
>
> So this, combined with module's opt-in declaration of known classes,
> effectively privatizes the .class_id space for each module (or
> coordinated set of modules).
>
> Notes:
>
> For all "class FOO" queries, ddebug_find_valid_class() is called, it
> returns the map matching the query, and sets valid_class via an
> *outvar).
>
> If no "class FOO" is supplied, valid_class = _CLASS_DFLT. This
> insures that legacy queries do not trample on new class'd callsites,
> as they get added.

Hi Jim,

I'm wondering about the case where we have a callsite which is marked
as 'class foo', but the query string is done by say module and file, so:

# echo "module bar file foo.c +p" > /proc/dynamic_debug_control

With the proposed code, I think this ends up not enabling anything right?
Because valid class is set to _DPRINTK_CLASS_DFLT and then:
'dp->class_id != valid_class' is true?

This seems confusing to me as a user as this doesn't work like the
other queries....so maybe we should only do the
'dp->class_id != valid_class' check *if* query->class_string is set,
see below.

>
> Also add a new column to control-file output, displaying non-default
> class-name (when found) or the "unknown _id:", if it has not been
> (correctly) declared with one of the declarator macros.
>
> Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
> ---
> lib/dynamic_debug.c | 76 ++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 68 insertions(+), 8 deletions(-)
>
> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index b71efd0b491d..db96ded78c3f 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
> @@ -56,6 +56,7 @@ struct ddebug_query {
> const char *module;
> const char *function;
> const char *format;
> + const char *class_string;
> unsigned int first_lineno, last_lineno;
> };
>
> @@ -136,15 +137,33 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
> fmtlen--;
> }
>
> - v3pr_info("%s: func=\"%s\" file=\"%s\" module=\"%s\" format=\"%.*s\" lineno=%u-%u\n",
> - msg,
> - query->function ?: "",
> - query->filename ?: "",
> - query->module ?: "",
> - fmtlen, query->format ?: "",
> - query->first_lineno, query->last_lineno);
> + v3pr_info("%s: func=\"%s\" file=\"%s\" module=\"%s\" format=\"%.*s\" lineno=%u-%u class=%s\n",
> + msg,
> + query->function ?: "",
> + query->filename ?: "",
> + query->module ?: "",
> + fmtlen, query->format ?: "",
> + query->first_lineno, query->last_lineno, query->class_string);
> }
>
> +static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table const *dt,
> + const char *class_string, int *class_id)
> +{
> + struct ddebug_class_map *map;
> + int idx;
> +
> + list_for_each_entry(map, &dt->maps, link) {
> + idx = match_string(map->class_names, map->length, class_string);
> + if (idx >= 0) {
> + *class_id = idx + map->base;
> + return map;
> + }
> + }
> + *class_id = -ENOENT;
> + return NULL;
> +}
> +
> +#define __outvar /* filled by callee */
> /*
> * Search the tables for _ddebug's which match the given `query' and
> * apply the `flags' and `mask' to them. Returns number of matching
> @@ -159,6 +178,8 @@ static int ddebug_change(const struct ddebug_query *query,
> unsigned int newflags;
> unsigned int nfound = 0;
> struct flagsbuf fbuf, nbuf;
> + struct ddebug_class_map *map = NULL;
> + int __outvar valid_class;
>
> /* search for matching ddebugs */
> mutex_lock(&ddebug_lock);
> @@ -169,9 +190,22 @@ static int ddebug_change(const struct ddebug_query *query,
> !match_wildcard(query->module, dt->mod_name))
> continue;
>
> + if (query->class_string) {
> + map = ddebug_find_valid_class(dt, query->class_string, &valid_class);
> + if (!map)
> + continue;

So remove the else here.

> + } else {
> + /* constrain query, do not touch class'd callsites */
> + valid_class = _DPRINTK_CLASS_DFLT;
> + }
> +
> for (i = 0; i < dt->num_ddebugs; i++) {
> struct _ddebug *dp = &dt->ddebugs[i];
>
> + /* match site against query-class */
> + if (dp->class_id != valid_class)

And then make this: if (query->class_string && (dp->class_id != valid_class))

thoughts?

> + continue;
> +> /* match against the source filename */
> if (query->filename &&
> !match_wildcard(query->filename, dp->filename) &&
> @@ -420,6 +454,8 @@ static int ddebug_parse_query(char *words[], int nwords,
> } else if (!strcmp(keyword, "line")) {
> if (parse_linerange(query, arg))
> return -EINVAL;
> + } else if (!strcmp(keyword, "class")) {
> + rc = check_set(&query->class_string, arg, "class");
> } else {
> pr_err("unknown keyword \"%s\"\n", keyword);
> return -EINVAL;
> @@ -854,6 +890,20 @@ static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
> return dp;
> }
>
> +#define class_in_range(class_id, map) \
> + (class_id >= map->base && class_id < map->base + map->length)
> +
> +static const char *ddebug_class_name(struct ddebug_iter *iter, struct _ddebug *dp)
> +{
> + struct ddebug_class_map *map;
> +
> + list_for_each_entry(map, &iter->table->maps, link)
> + if (class_in_range(dp->class_id, map))
> + return map->class_names[dp->class_id - map->base];
> +
> + return NULL;
> +}
> +
> /*
> * Seq_ops show method. Called several times within a read()
> * call from userspace, with ddebug_lock held. Formats the
> @@ -865,6 +915,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
> struct ddebug_iter *iter = m->private;
> struct _ddebug *dp = p;
> struct flagsbuf flags;
> + char const *class;
>
> if (p == SEQ_START_TOKEN) {
> seq_puts(m,
> @@ -877,7 +928,16 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
> iter->table->mod_name, dp->function,
> ddebug_describe_flags(dp->flags, &flags));
> seq_escape_str(m, dp->format, ESCAPE_SPACE, "\t\r\n\"");
> - seq_puts(m, "\"\n");
> + seq_puts(m, "\"");
> +
> + if (dp->class_id != _DPRINTK_CLASS_DFLT) {
> + class = ddebug_class_name(iter, dp);
> + if (class)
> + seq_printf(m, " class:%s", class);
> + else
> + seq_printf(m, " class unknown, _id:%d", dp->class_id);
> + }
> + seq_puts(m, "\n");
>
> return 0;
> }