[PATCH v7 1/8] dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES and callbacks
Jim Cromie
jim.cromie at gmail.com
Tue Aug 31 20:21:26 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 2 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, these are
non-static and exported.
get/set use an augmented kernel_param; the arg refs a new struct
dyndbg_bitmap_param containing:
- the map (array, indexed by bitpos) of format-prefix strings, which
define the set/category of prdbgs to be changed per each bit.
- pointer to the user's ulong holding the bits/state.
by sharing state, we coordinate with code that still uses it directly
This will allow drm-debug to be converted incrementally, while still
using __drm_debug & drm_debug_enabled() in other parts.
param_set_dyndbg() compares new vs old bits, and only updates prdbgs
on changes. This maximally preserves the underlying state, which may
have been customized via later `echo $cmd >control`. So if a user
really wants to know that all prdbgs are set precisely, they must
pre-clear then set.
TLDR: this also doesn't affect the decorator flags "mflt" set per prdbg.
dynamic_debug.h:
Add DEFINE_DYNAMIC_DEBUG_CATEGORIES() described above, and a stub
throwing a BUILD_BUG (RFC) when used without DYNAMIC_DEBUG support.
Add structs dyndbg_bitdesc, dyndbg_bitmap_param to support the macro.
Note that it also calls MODULE_PARM_DESC for the user, but expects the
user to catenate all the bit-descriptions together (as is done in
drm.debug), and in the following uses in amdgpu, i915.
The intent is to regenerate this output from per-bit help given in
VA_ARGS, including a bit_label(); but this can wait.
Also externs the struct kernel_param param_ops_dyndbg symbol, as is
done in moduleparams.h for all the STANDARD params.
USAGE NOTES:
Using dyndbg to query on "format ^$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.
Using DEFINE_DYNAMIC_DEBUG_CATEGORIES wo support gets a BUILD_BUG.
ISTM there is already action at a declarative distance, nobody needs
mystery as to why the /sysfs thingy didn't appear.
Dyndbg is completely agnostic wrt the categorization scheme used, in
order to play well with any prefix convention already in use in the
codebase. Ad-hoc categories and sub-categories are implicitly
allowed, author discipline and review is expected.
Here are some examples:
"1","2","3" 2 doesn't 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:","fixme:" might be handy
"A:".."Z:" uhm, yeah
Hierarchical classes/categories are natural:
"drm:<CAT>:" is used in a later commit
"drm:<CAT>:<SUB>:" is a natural extension.
"drm:atomic:fail:" has been proposed, sounds directly useful
NB: in a real sense we abandon enum strictures here, and lose some
compiler help, on spelling errs for example. Obviously "drm:" != "DRM:".
Some properties of a hierarchical category deserve explication:
Trailing spaces matter !
With 1..3-space ("drm: ", "drm:atomic: ", "drm:atomic:fail: "), the
":" doesn't terminate the search-space, the trailing space does. So a
"drm:" search spec will match all DRM categories & subcategories, and
will not be useful in an interface where all categories are already
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_atomic("fail: ...") pastes 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 newer FOO().
IE: drm_dbg_atomic_("fail: ..."); // trailing _ means ad-hoc subcat
Summarizing:
- "drm:kms: " & "drm:kms:" are different
- "drm:kms" also different - includes drm:kms2:
- "drm:kms:\t" also different - could be troublesome
- "drm:kms:*" doesn't 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 it's 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.
Signed-off-by: Jim Cromie <jim.cromie at gmail.com>
---
v5:
. rename to DEFINE_DYNAMIC_DEBUG_CATEGORIES from DEFINE_DYNDBG_BITMAP
. in set_dyndbg, 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>
v6:
. return rc, bitmap->, snprintf, ws - Andy Shevchenko
. s/chgct/matches/ - old varname is misleading
. move code off file bottom to a "better" place
. change ##fsname to ##var for less generic varname (ie: not "debug")
. add KP_MOD_NAME workaround for !CONFIG_MODULES
. move forward decl down to where its needed
v7:
. use kp->arg, dont need kp->data or previous patch-1 - jbaron
. use client's ulong for bits, share state
. throw BUILD_BUG if DEFINE_DYNAMIC_DEBUG_CATEGORIES used wo support
---
include/linux/dynamic_debug.h | 60 ++++++++++++++++++++++++++
lib/dynamic_debug.c | 79 ++++++++++++++++++++++++++++++++++-
2 files changed, 138 insertions(+), 1 deletion(-)
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index dce631e678dd..f51b738668a0 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -181,6 +181,10 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
KERN_DEBUG, prefix_str, prefix_type, \
rowsize, groupsize, buf, len, ascii)
+struct kernel_param;
+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 +231,62 @@ static inline int dynamic_debug_exec_queries(const char *query, const char *modn
return 0;
}
+struct kernel_param;
+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;
+};
+
+struct dyndbg_bitmap_param {
+ unsigned long *bits;
+ struct dyndbg_bitdesc map[];
+};
+
+#if defined(CONFIG_DYNAMIC_DEBUG) || \
+ (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
+/**
+ * DEFINE_DYNAMIC_DEBUG_CATEGORIES() - bitmap control of categorized prdbgs
+ * @fsname: parameter basename under /sys
+ * @var: C-identifier holding bitmap
+ * @_desc: string summarizing the controls provided
+ * @...: list of struct dyndbg_bitdesc initializations
+ *
+ * Intended for modules with substantial use of "categorized" prdbgs
+ * (those with some systematic prefix in the format string), this lets
+ * modules (using dyndbg) control those prdbg groups according to
+ * their prefixes, and map them to bits 0-N of a sysfs control point.
+ * The @bits... identifies the prefixes to be used by dyndbg to
+ * select and alter those categorized prdbgs, order defines bitpos.
+ */
+#define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, _var, _desc, ...) \
+ MODULE_PARM_DESC(fsname, _desc); \
+ static struct dyndbg_bitmap_param ddcats_##_var = \
+ { .bits = &_var, .map = { __VA_ARGS__, { .prefix = NULL }}}; \
+ module_param_cb(fsname, ¶m_ops_dyndbg, &ddcats_##_var, 0644)
+
+#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;
+
+#elif (defined(CONFIG_DYNAMIC_DEBUG_CORE) && !defined(DYNAMIC_DEBUG_MODULE))
+
+#define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, var, bitmap_desc, ...) \
+ BUILD_BUG_ON_MSG(1, "you need -DDYNAMIC_DEBUG_MODULE in compile")
+
+#else
+#define DEFINE_DYNAMIC_DEBUG_CATEGORIES(fsname, var, bitmap_desc, ...) \
+ BUILD_BUG_ON_MSG(1, "DYNAMIC_DEBUG support required to use this macro: " #var)
+#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..9f9e70023aa4 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\" mod:%s\n", i, query, modname ?: "*");
rc = ddebug_exec_query(query, modname);
if (rc < 0) {
@@ -577,6 +577,83 @@ int dynamic_debug_exec_queries(const char *query, const char *modname)
}
EXPORT_SYMBOL_GPL(dynamic_debug_exec_queries);
+#ifdef CONFIG_MODULES
+#define KP_MOD_NAME kp->mod->name
+#else
+#define KP_MOD_NAME NULL /* wildcard */
+#endif
+#define FMT_QUERY_SIZE 128 /* typically need <40 */
+/**
+ * param_set_dyndbg - bits => categories >control setter
+ * @instr: string echo>d to sysfs
+ * @kp: kp->arg has state: bits, map
+ *
+ * Enable/disable prdbgs by their "category", as defined in args to
+ * DEFINE_DYNAMIC_DEBUG_CATEGORIES
+ * Returns: 0 or <0 if error.
+ */
+int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
+{
+ unsigned long inbits;
+ int rc, i, matches = 0, totct = 0;
+ char query[FMT_QUERY_SIZE];
+ const struct dyndbg_bitmap_param *p = kp->arg;
+ const struct dyndbg_bitdesc *map = p->map;
+
+ if (!map) {
+ pr_err("set_dyndbg: no bits=>queries map\n");
+ return -EINVAL;
+ }
+ rc = kstrtoul(instr, 0, &inbits);
+ if (rc) {
+ pr_err("set_dyndbg: failed\n");
+ return rc;
+ }
+ vpr_info("set_dyndbg: new 0x%lx old 0x%lx\n", inbits, *p->bits);
+
+ for (i = 0; map->prefix && i < BITS_PER_LONG; map++, i++) {
+
+ if (test_bit(i, &inbits) == test_bit(i, p->bits))
+ continue;
+ snprintf(query, FMT_QUERY_SIZE, "format '^%s' %cp", map->prefix,
+ test_bit(i, &inbits) ? '+' : '-');
+
+ matches = ddebug_exec_queries(query, KP_MOD_NAME);
+
+ v2pr_info("bit-%d: %d matches on format '^%s'\n", i,
+ matches, map->prefix);
+ totct += matches;
+ }
+ *p->bits = inbits;
+ vpr_info("total matches: %d\n", totct);
+ return 0;
+}
+EXPORT_SYMBOL(param_set_dyndbg);
+
+/**
+ * param_get_dyndbg - bitmap reader
+ * @buffer: receives string rep of bitmap
+ * @kp: kp->arg has state: bits, map
+ *
+ * Reads last written bits, underlying prdbg state may have changed since.
+ * Returns: #chars written
+ */
+int param_get_dyndbg(char *buffer, const struct kernel_param *kp)
+{
+ const struct dyndbg_bitmap_param *p = kp->arg;
+ unsigned long val = *p->bits;
+
+ return scnprintf(buffer, PAGE_SIZE, "0x%lx\n", val);
+}
+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);
+
#define PREFIX_SIZE 64
static int remaining(int wrote)
--
2.31.1
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