[PATCH v5 3/9] dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES and callbacks
Jim Cromie
jim.cromie at gmail.com
Fri Aug 13 15:17:11 UTC 2021
DEFINE_DYNAMIC_DEBUG_CATEGORIES(name, var, bitmap_desc, @bit_descs)
allows users to define a drm.debug style (bitmap) sysfs interface, and
to specify the desired mapping from bits[0-N] to the format-prefix'd
pr_debug()s to be controlled.
DEFINE_DYNAMIC_DEBUG_CATEGORIES(debug_gvt, __gvt_debug,
"i915/gvt bitmap desc",
/**
* search-prefixes, passed to dd-exec_queries
* defines bits 0-N in order.
* leading ^ is tacitly inserted (by callback currently)
* trailing space used here excludes subcats.
* helper macro needs more work
* macro to autogen ++$i, 0x%x$i ?
*/
_DD_cat_("gvt:cmd: "),
_DD_cat_("gvt:core: "),
_DD_cat_("gvt:dpy: "),
_DD_cat_("gvt:el: "),
_DD_cat_("gvt:irq: "),
_DD_cat_("gvt:mm: "),
_DD_cat_("gvt:mmio: "),
_DD_cat_("gvt:render: "),
_DD_cat_("gvt:sched: "));
dynamic_debug.c: add 3 new elements:
- int param_set_dyndbg()
- int param_get_dyndbg()
- struct kernel_param_ops param_ops_dyndbg
Following the model of kernel/params.c STANDARD_PARAM_DEFS, All 3 are
non-static and exported.
dynamic_debug.h:
Add DEFINE_DYNAMIC_DEBUG_CATEGORIES() described above, and a do-nothing stub.
Note that it also calls MODULE_PARM_DESC for the user, but expects the
user to catenate all the bit-descriptions together (as is done in
drm.debug), and in the following uses in amdgpu, i915.
This in the hope that someone can offer an auto-incrementing
label-generating macro, producing "\tbit-4 0x10\t" etc, and can show
how to apply it to __VA_ARGS__.
Also extern the struct kernel_param param_ops_dyndbg symbol, as is
done in moduleparams.h for all the STANDARD params.
USAGE NOTES:
Using dyndbg to query on "format ^$prefix" requires that the prefix be
present in the compiled-in format string; where run-time prefixing is
used, that format would be "%s...", which is not usefully selectable.
Adding structural query terms (func,file,lineno) could help (module is
already done), but DEFINE_DYNAMIC_DEBUG_CATEGORIES can't do that now,
adding it needs a better reason imo.
Dyndbg is completely agnostic wrt the categorization scheme used, to
play well with any prefix convention already in use. Ad-hoc
categories and sub-categories are implicitly allowed, author
discipline and review is expected.
Here are some examples:
"1","2","3" 2 doesnt imply 1.
otherwize, sorta like printk levels
"1:","2:","3:" are better, avoiding [1-9]\d+ ambiguity
"hi:","mid:","low:" are reasonable, and imply independence
"todo:","rfc:" might be handy
"A:".."Z:" uhm, yeah
Hierarchical classes/categories are natural:
"drm:<CAT>:" is used in later commit
"drm:<CAT>:<SUB>:" is a natural extension.
"drm:atomic:fail:" has been proposed, sounds directly useful
Some properties of a hierarchical category deserve explication:
Trailing spaces matter !
With 1..3-space ("drm: ", "drm:atomic: ", "drm:atomic:fail: "), the
":" doesnt terminate the search-space, the trailing space does.
So a "drm:" search specification will match all DRM categories &
subcategories, and will not be useful in an interface where all
categories are controlled together. That said, "drm:atomic:" &
"drm:atomic: " are different, and both are useful in cases.
Ad-Hoc sub-categories:
These have a caveat wrt wrapper macros adding prefixes like
"drm:atomic: "; the trailing space in the prefix means that
drm_dbg("fail: ...") renders as "drm:atomic: fail: ", which obviously
isn't ideal wrt clear and simple bitmaps.
A possible solution is to have a FOO_() version of every FOO() macro
which (anti-mnemonically) elides the trailing space, which is normally
inserted by a modified FOO(). Doing this would enforce a policy
decision that "debug categories will be space terminated", with an
pressure-relief valve.
Summarizing:
- "drm:kms: " & "drm:kms:" are different
- "drm:kms" also different - includes drm:kms2:
- "drm:kms:\t" also different
- "drm:kms:*" doesnt work, no wildcard on format atm.
Order matters in DEFINE_DYNAMIC_DEBUG_CATEGORIES(... @bit_descs)
@bit_descs (array) position determines the bit mapping to the prefix,
so to keep a stable map, new categories or 3rd level categories must
be added to the end.
Since bits are/will-stay applied 0-N, the later bits can countermand
the earlier ones, but its tricky - consider;
DD_CATs(... "drm:atomic:", ""drm:atomic:fail:" ) // misleading
The 1st search-term is misleading, because it includes (modifies)
subcategories, but then 2nd overrides it. So don't do that.
There is still plenty of bikeshedding to do.
---
v4+:
. rename to DEFINE_DYNAMIC_DEBUG_CATEGORIES from DEFINE_DYNDBG_BITMAP
. in query, replace hardcoded "i915" w kp->mod->name
. static inline the stubs
. const *str in structs, const array. -Emil
. dyndbg: add do-nothing DEFINE_DYNAMIC_DEBUG_CATEGORIES if !DD_CORE
. call MOD_PARM_DESC(name, "$desc") for users
. simplify callback, remove bit-change detection
. config errs reported by <lkp at intel.com>
ddh-helpers
Signed-off-by: Jim Cromie <jim.cromie at gmail.com>
---
include/linux/dynamic_debug.h | 50 ++++++++++++++++++++++++++++
lib/dynamic_debug.c | 62 ++++++++++++++++++++++++++++++++++-
2 files changed, 111 insertions(+), 1 deletion(-)
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index dce631e678dd..42cfb37d4870 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -52,6 +52,7 @@ struct _ddebug {
} __attribute__((aligned(8)));
+struct kernel_param;
#if defined(CONFIG_DYNAMIC_DEBUG_CORE)
@@ -181,6 +182,9 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
KERN_DEBUG, prefix_str, prefix_type, \
rowsize, groupsize, buf, len, ascii)
+int param_set_dyndbg(const char *instr, const struct kernel_param *kp);
+int param_get_dyndbg(char *buffer, const struct kernel_param *kp);
+
#else /* !CONFIG_DYNAMIC_DEBUG_CORE */
#include <linux/string.h>
@@ -227,6 +231,52 @@ static inline int dynamic_debug_exec_queries(const char *query, const char *modn
return 0;
}
+static inline int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
+{ return 0; }
+static inline int param_get_dyndbg(char *buffer, const struct kernel_param *kp)
+{ return 0; }
+
#endif /* !CONFIG_DYNAMIC_DEBUG_CORE */
+struct dyndbg_bitdesc {
+ /* bitpos is inferred from index in containing array */
+ const char *prefix;
+ const char *help;
+};
+
+#if defined(CONFIG_DYNAMIC_DEBUG) || \
+ (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
+/**
+ * DEFINE_DYNAMIC_DEBUG_CATEGORIES() - define debug categories, bitmap, sysfs-knob
+ * @fsname: parameter basename under /sys
+ * @var: C-identifier holding state
+ * @_desc: string summarizing the controls provided
+ * @...: list of struct dyndbg_bitdesc initializations
+ *
+ * Defines /sys/modules/$modname/parameters/@fsname, and @bit_descs,
+ * which maps bits 0-N to categories of pr_debugs to be controlled.
+ * This is effectively write only, because controlled callsites can be
+ * further modified via >control.
+ *
+ * Also calls MODULE_PARM_DESC(fsname, _desc), with the intent to
+ * generate the bit_legend and apply it to the given bit_descs
+ */
+#define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, var, _desc, ...) \
+ MODULE_PARM_DESC(fsname, _desc); \
+ static struct dyndbg_bitdesc const dyndbg_cats_##fsname[] = \
+ { __VA_ARGS__, { NULL, NULL } }; \
+ module_param_cbd(fsname, ¶m_ops_dyndbg, &var, 0644, \
+ &dyndbg_cats_##fsname);
+
+#define _DD_cat_(pfx) { .prefix = pfx, .help = "help for " pfx }
+#define _DD_cat_help_(pfx) "\t " pfx "\t- help for " pfx "\n"
+
+extern const struct kernel_param_ops param_ops_dyndbg;
+#else
+#define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, var, bitmap_desc, ...) \
+ MODULE_PARM_DESC(fsname, "auto: " bitmap_desc);
+#define _DD_cat_(pfx)
+#define _DD_cat_help_(pfx)
+#endif
+
#endif
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index cb5abb42c16a..6bc645a663e7 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -529,7 +529,7 @@ static int ddebug_exec_queries(char *query, const char *modname)
if (!query || !*query || *query == '#')
continue;
- vpr_info("query %d: \"%s\"\n", i, query);
+ vpr_info("query %d: \"%s\" %s\n", i, query, (modname) ? modname : "");
rc = ddebug_exec_query(query, modname);
if (rc < 0) {
@@ -1154,3 +1154,63 @@ early_initcall(dynamic_debug_init);
/* Debugfs setup must be done later */
fs_initcall(dynamic_debug_init_control);
+
+#include <linux/moduleparam.h>
+
+#define OUR_QUERY_SIZE 128 /* typically need <40 */
+
+/**
+ * param_set_dyndbg() - drm.debug style bitmap to format-prefix categories
+ * @instr: string echo>d to sysfs
+ * @kp: struct kernel_param* ->data has bitmap
+ * Exported to support DEFINE_DYNAMIC_DEBUG_CATEGORIES
+ */
+int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
+{
+ unsigned long inbits;
+ int rc, i, chgct = 0, totct = 0;
+ char query[OUR_QUERY_SIZE];
+ struct dyndbg_bitdesc *bitmap = (struct dyndbg_bitdesc *) kp->data;
+
+ rc = kstrtoul(instr, 0, &inbits);
+ if (rc) {
+ pr_err("set_dyndbg: failed\n");
+ return -EINVAL;
+ }
+ vpr_info("set_dyndbg: input 0x%lx\n", inbits);
+
+ for (i = 0; !!bitmap[i].prefix; i++) {
+
+ sprintf(query, "format '^%s' %cp", bitmap[i].prefix,
+ test_bit(i, &inbits) ? '+' : '-');
+
+ chgct = dynamic_debug_exec_queries(query, kp->mod->name);
+
+ v2pr_info("bit-%d: %d changes by '%s'\n", i, chgct, query);
+ totct += chgct;
+ }
+ vpr_info("total changes: %d\n", totct);
+ return 0;
+}
+EXPORT_SYMBOL(param_set_dyndbg);
+
+/**
+ * param_get_dyndbg() - drm.debug style bitmap to format-prefix categories
+ * @buffer: string returned to user via sysfs
+ * @kp: struct kernel_param*
+ * Exported to support DEFINE_DYNAMIC_DEBUG_CATEGORIES interfaces, not
+ * useful; pr_debugs may be altered after setting via >control
+ */
+int param_get_dyndbg(char *buffer, const struct kernel_param *kp)
+{
+ return scnprintf(buffer, PAGE_SIZE, "%u\n",
+ *((unsigned int *)kp->arg));
+}
+EXPORT_SYMBOL(param_get_dyndbg);
+
+const struct kernel_param_ops param_ops_dyndbg = {
+ .set = param_set_dyndbg,
+ .get = param_get_dyndbg,
+};
+/* support DEFINE_DYNAMIC_DEBUG_CATEGORIES users */
+EXPORT_SYMBOL(param_ops_dyndbg);
--
2.31.1
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