Current classmap code protects class'd pr_debugs from unintended
changes by "legacy" unclassed queries:
# this doesn't disable all of DRM_UT_* categories
echo "-p" > /proc/dynamic_debug/control
# name the class to change it - protective but tedious
echo "class DRM_UT_CORE +p" > /proc/dynamic_debug/control
# or do it the subsystem way
echo 1 > /sys/module/drm/parameters/debug
This "name the class to change it" behavior gave a modicum of
protection to classmap users (ie DRM) so their debug settings aren't
trivially and unintentionally altered underneath them.
But this made the class keyword special in some sense; the other
keywords skip only on explicit mismatch, otherwize the code falls thru
to adjust the pr-debug site.
So Jason Baron didn't like this special case when I 1st proposed it;
I argued 2 points:
- "protection gives stable-debug, improving utility"
- __drm_debug is authoritative w/o dyndbg under it.
I thought I'd convinced him back then, (and the patchset got merged),
but he noted it again when he reviewed this series. So this commit
names the "special case": ddebug_client_module_protects_classes(), and
reverts it to Jason's preference.
If a class mismatch is seen, code distinguishes whether the class was
explicitly given (and always skips/continue), or the DFLT was assumed
because no class was given. Here we test
ddebug_client_module_protects_classes(), skip if so.
Later, if any user/module wants to protect its classes, we could add a
flag to ddebug_table, a means to set it from CLASSMAP_DEFINE, and
check it when applying a classless query/cmd.
CC: jba...@akamai.com
Signed-off-by: Jim Cromie <jim.cro...@gmail.com>
---
lib/dynamic_debug.c | 34 +++++++++++++++++++++++++---------
1 file changed, 25 insertions(+), 9 deletions(-)
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index c44502787c2b..13de0dd3a4ad 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -193,6 +193,17 @@ static int ddebug_find_valid_class(struct ddebug_table
const *dt, const char *cl
return -ENOENT;
}
+/*
+ * classmaps-v1 protected classes from changes by legacy commands
+ * (those selecting _DPRINTK_CLASS_DFLT by omission), v2 undoes that
+ * special treatment. State so explicitly. Later we could give
+ * modules the choice to protect their classes or to keep v2 behavior.
+ */
+static inline bool ddebug_client_module_protects_classes(const struct
ddebug_table *dt)
+{
+ return false;
+}
+
/*
* Search the tables for _ddebug's which match the given `query' and
* apply the `flags' and `mask' to them. Returns number of matching
@@ -206,7 +217,7 @@ static int ddebug_change(const struct ddebug_query *query,
struct flag_settings
unsigned int newflags;
unsigned int nfound = 0;
struct flagsbuf fbuf, nbuf;
- int valid_class;
+ int slctd_class;
/* search for matching ddebugs */
mutex_lock(&ddebug_lock);
@@ -218,21 +229,26 @@ static int ddebug_change(const struct ddebug_query
*query, struct flag_settings
continue;
if (query->class_string) {
- valid_class = ddebug_find_valid_class(dt,
query->class_string);
- if (valid_class < 0)
+ slctd_class = ddebug_find_valid_class(dt,
query->class_string);
+ if (slctd_class < 0)
+ /* skip/reject classes unknown by module */
continue;
} else {
- /* constrain query, do not touch class'd callsites */
- valid_class = _DPRINTK_CLASS_DFLT;
+ slctd_class = _DPRINTK_CLASS_DFLT;
}
for (i = 0; i < dt->info.descs.len; i++) {
struct _ddebug *dp = &dt->info.descs.start[i];
- /* match site against query-class */
- if (dp->class_id != valid_class)
- continue;
-
+ if (dp->class_id != slctd_class) {
+ if (query->class_string)
+ /* site.class != given class */
+ continue;
+ /* legacy query, class'd site */
+ else if
(ddebug_client_module_protects_classes(dt))
+ continue;
+ /* allow change on class'd pr_debug */
+ }
/* match against the source filename */
if (query->filename &&
!match_wildcard(query->filename, dp->filename) &&
--
2.49.0
