[PATCH v2 10/59] dyndbg: replace classmap list with a vector
Louis Chauvet
louis.chauvet at bootlin.com
Mon Mar 24 15:08:13 UTC 2025
Le 20/03/2025 à 19:51, Jim Cromie a écrit :
> Classmaps are stored in an elf section/array, but currently are
> individually list-linked onto dyndbg's per-module ddebug_table for
> operation. This is unnecessary.
>
> Just like dyndbg's descriptors, classes are packed in compile order;
> so even with many builtin modules employing multiple classmaps, each
> modules' maps are packed contiguously, and can be treated as a
> array-start-address & array-length.
>
> So this drops the whole list building operation done in
> ddebug_attach_module_classes(), and removes the list-head members.
> The "select-by-modname" condition is reused to find the start,end of
> the subrange.
>
> NOTE: This "filter-by-modname" on classmaps should really be done in
> ddebug_add_module(1); ie at least one step closer to ddebug_init(2),
> which already splits up pr-debug descriptors into subranges by
> modname, then calls (1) on each. (2) knows nothing of classmaps
> currently, and doesn't need to. For now, just add comment.
>
> Signed-off-by: Jim Cromie <jim.cromie at gmail.com>
> ---
> include/linux/dynamic_debug.h | 1 -
> lib/dynamic_debug.c | 61 ++++++++++++++++++-----------------
> 2 files changed, 32 insertions(+), 30 deletions(-)
>
> diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> index ac199293d203..e458d4b838ac 100644
> --- a/include/linux/dynamic_debug.h
> +++ b/include/linux/dynamic_debug.h
> @@ -83,7 +83,6 @@ enum class_map_type {
> };
>
> struct ddebug_class_map {
> - struct list_head link;
> struct module *mod;
> const char *mod_name; /* needed for builtins */
> const char **class_names;
> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index dd7320b9616d..d5572712ce55 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
> @@ -45,10 +45,11 @@ extern struct ddebug_class_map __start___dyndbg_classes[];
> extern struct ddebug_class_map __stop___dyndbg_classes[];
>
> struct ddebug_table {
> - struct list_head link, maps;
> + struct list_head link;
> const char *mod_name;
> - unsigned int num_ddebugs;
> struct _ddebug *ddebugs;
> + struct ddebug_class_map *classes;
> + unsigned int num_ddebugs, num_classes;
> };
>
> struct ddebug_query {
> @@ -147,13 +148,15 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
> query->first_lineno, query->last_lineno, query->class_string);
> }
>
> +#define __outvar /* filled by callee */
> static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table const *dt,
> - const char *class_string, int *class_id)
> + const char *class_string,
> + __outvar int *class_id)
Thanks for your explanation of __outvar! It makes sense. I never seen
this pattern anywhere in the kernel, maybe a simple doc comment is
enough to carry the information:
/**
* ddebug_find_valid_class - Find a valid class for a
* given string
* @dt: debug table to inspect
* @class_string: string to match on
* @class_id: output pointer for the class_id value
*
* Returns: Pointer to the ddebug_class_map instance, if found.
* @class_id will be set to the id of this class. If no class
* matching @class_string is found, returns NULL and class_id is
* set to -ENOENT.
*/
Or at maybe change the documentation of __outvar to be a bit more
explicit about how it works (I had difficulties to understand because a
lot of "magic macro" exist in the kernel and sometimes carry information
to the compiler, but this one is always empty):
/**
* __outvar - Denotes that an argument is used as an output
* value
* This macro does nothing apart clarify for the reader that
* the parameter will be filled by the callee
*/
With any of the modifications (feel free to reword them as you want):
Reviewed-by: Louis Chauvet <louis.chauvet at bootlin.com>
> {
> struct ddebug_class_map *map;
> - int idx;
> + int i, idx;
>
> - list_for_each_entry(map, &dt->maps, link) {
> + for (map = dt->classes, i = 0; i < dt->num_classes; i++, map++) {
> idx = match_string(map->class_names, map->length, class_string);
> if (idx >= 0) {
> *class_id = idx + map->base;
> @@ -164,7 +167,6 @@ static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table cons
> 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
> @@ -1122,9 +1124,10 @@ static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
>
> static const char *ddebug_class_name(struct ddebug_iter *iter, struct _ddebug *dp)
> {
> - struct ddebug_class_map *map;
> + struct ddebug_class_map *map = iter->table->classes;
> + int i, nc = iter->table->num_classes;
>
> - list_for_each_entry(map, &iter->table->maps, link)
> + for (i = 0; i < nc; i++, map++)
> if (class_in_range(dp->class_id, map))
> return map->class_names[dp->class_id - map->base];
>
> @@ -1208,30 +1211,31 @@ static const struct proc_ops proc_fops = {
> .proc_write = ddebug_proc_write
> };
>
> -static void ddebug_attach_module_classes(struct ddebug_table *dt,
> - struct ddebug_class_map *classes,
> - int num_classes)
> +static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug_info *di)
> {
> struct ddebug_class_map *cm;
> - int i, j, ct = 0;
> + int i, nc = 0;
>
> - for (cm = classes, i = 0; i < num_classes; i++, cm++) {
> + /*
> + * Find this module's classmaps in a subrange/wholerange of
> + * the builtin/modular classmap vector/section. Save the start
> + * and length of the subrange at its edges.
> + */
> + for (cm = di->classes, i = 0; i < di->num_classes; i++, cm++) {
>
> if (!strcmp(cm->mod_name, dt->mod_name)) {
> -
> - v2pr_info("class[%d]: module:%s base:%d len:%d ty:%d\n", i,
> - cm->mod_name, cm->base, cm->length, cm->map_type);
> -
> - for (j = 0; j < cm->length; j++)
> - v3pr_info(" %d: %d %s\n", j + cm->base, j,
> - cm->class_names[j]);
> -
> - list_add(&cm->link, &dt->maps);
> - ct++;
> + if (!nc) {
> + v2pr_info("start subrange, class[%d]: module:%s base:%d len:%d ty:%d\n",
> + i, cm->mod_name, cm->base, cm->length, cm->map_type);
> + dt->classes = cm;
> + }
> + nc++;
> }
> }
> - if (ct)
> - vpr_info("module:%s attached %d classes\n", dt->mod_name, ct);
> + if (nc) {
> + dt->num_classes = nc;
> + vpr_info("module:%s attached %d classes\n", dt->mod_name, nc);
> + }
> }
>
> /*
> @@ -1263,10 +1267,9 @@ static int ddebug_add_module(struct _ddebug_info *di, const char *modname)
> dt->num_ddebugs = di->num_descs;
>
> INIT_LIST_HEAD(&dt->link);
> - INIT_LIST_HEAD(&dt->maps);
>
> if (di->classes && di->num_classes)
> - ddebug_attach_module_classes(dt, di->classes, di->num_classes);
> + ddebug_attach_module_classes(dt, di);
>
> mutex_lock(&ddebug_lock);
> list_add_tail(&dt->link, &ddebug_tables);
> @@ -1379,8 +1382,8 @@ static void ddebug_remove_all_tables(void)
> mutex_lock(&ddebug_lock);
> while (!list_empty(&ddebug_tables)) {
> struct ddebug_table *dt = list_entry(ddebug_tables.next,
> - struct ddebug_table,
> - link);
> + struct ddebug_table,
> + link);
> ddebug_table_free(dt);
> }
> mutex_unlock(&ddebug_lock);
--
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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