@@ -20,6 +20,7 @@ struct _ddebug {
const char *function;
const char *filename;
const char *format;
+ int (*tracer)(const char *fmt, char *prefix, char *label, struct va_format *vaf);
unsigned int lineno:18;
/*
* The flags field controls the behaviour at the callsite.
@@ -27,7 +28,11 @@ struct _ddebug {
* writes commands to <debugfs>/dynamic_debug/control
*/
#define _DPRINTK_FLAGS_NONE 0
-#define _DPRINTK_FLAGS_PRINT (1<<0) /* printk() a message using the format */
+#define _DPRINTK_FLAGS_PRINT (1<<0) /* printk() a message */
+#define _DPRINTK_FLAGS_PRINT_TRACE (1<<5) /* call (*tracer) */
+
+#define _DPRINTK_ENABLED (_DPRINTK_FLAGS_PRINT | _DPRINTK_FLAGS_PRINT_TRACE)
+
#define _DPRINTK_FLAGS_INCL_MODNAME (1<<1)
#define _DPRINTK_FLAGS_INCL_FUNCNAME (1<<2)
#define _DPRINTK_FLAGS_INCL_LINENO (1<<3)
@@ -277,4 +282,9 @@ extern const struct kernel_param_ops param_ops_dyndbg;
#define _DD_cat_help_(pfx)
#endif
+int dynamic_debug_register_tracer(const char *query, const char *mod,
+ int (*tracer)(const char *fmt, char *prefix, char *label, struct va_format *vaf));
+int dynamic_debug_unregister_tracer(const char *query, const char *mod,
+ int (*cookie)(const char *fmt, char *prefix, char *label, struct va_format *vaf));
+
#endif
@@ -2486,6 +2486,17 @@ config TEST_STATIC_KEYS
If unsure, say N.
+config TEST_DYNAMIC_DEBUG
+ tristate "Test DYNAMIC_DEBUG"
+ depends on m
+ depends on DYNAMIC_DEBUG
+ help
+ This module registers a tracer callback to count enabled
+ pr_debugs in a 'do_debugging' function, then alters their
+ enablements, calls the function, and compares counts.
+
+ If unsure, say N.
+
config TEST_KMOD
tristate "kmod stress tester"
depends on m
@@ -82,6 +82,7 @@ obj-$(CONFIG_TEST_SORT) += test_sort.o
obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o
obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
+obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o
obj-$(CONFIG_TEST_PRINTF) += test_printf.o
obj-$(CONFIG_TEST_SCANF) += test_scanf.o
obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
@@ -85,6 +85,7 @@ static inline const char *trim_prefix(const char *path)
static struct { unsigned flag:8; char opt_char; } opt_array[] = {
{ _DPRINTK_FLAGS_PRINT, 'p' },
+ { _DPRINTK_FLAGS_PRINT_TRACE, 'T' },
{ _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
{ _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
@@ -146,7 +147,8 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
* logs the changes. Takes ddebug_lock.
*/
static int ddebug_change(const struct ddebug_query *query,
- struct flag_settings *modifiers)
+ struct flag_settings *modifiers,
+ int (*tracer)(const char *, char *, char *, struct va_format *))
{
int i;
struct ddebug_table *dt;
@@ -205,11 +207,42 @@ static int ddebug_change(const struct ddebug_query *query,
newflags = (dp->flags & modifiers->mask) | modifiers->flags;
if (newflags == dp->flags)
continue;
+
+ /* handle T flag */
+ if (newflags & _DPRINTK_FLAGS_PRINT_TRACE) {
+ if (!tracer)
+ v2pr_info("ok: tracer enable\n");
+ else {
+ /* register attempt */
+ if (!dp->tracer) {
+ v2pr_info("register tracer\n");
+ dp->tracer = tracer;
+
+ } else if (tracer == dp->tracer)
+ v2pr_info("ok: tracer over-set\n");
+ else
+ pr_warn("tracer register error\n");
+ }
+ } else if (dp->flags & _DPRINTK_FLAGS_PRINT_TRACE) {
+ if (!tracer)
+ v2pr_info("ok: disable\n");
+ else {
+ /* only unregister has a !!tracer */
+ if (!dp->tracer)
+ pr_warn("nok: tracer already unset\n");
+
+ else if (dp->tracer == tracer) {
+ v2pr_info("ok: cookie match, unregistering\n");
+ dp->tracer = NULL;
+ } else
+ pr_warn("nok: tracer cookie match fail\n");
+ }
+ }
#ifdef CONFIG_JUMP_LABEL
- if (dp->flags & _DPRINTK_FLAGS_PRINT) {
- if (!(modifiers->flags & _DPRINTK_FLAGS_PRINT))
+ if (dp->flags & _DPRINTK_ENABLED) {
+ if (!(modifiers->flags & _DPRINTK_ENABLED))
static_branch_disable(&dp->key.dd_key_true);
- } else if (modifiers->flags & _DPRINTK_FLAGS_PRINT)
+ } else if (modifiers->flags & _DPRINTK_ENABLED)
static_branch_enable(&dp->key.dd_key_true);
#endif
dp->flags = newflags;
@@ -482,7 +515,7 @@ static int ddebug_parse_flags(const char *str, struct flag_settings *modifiers)
return 0;
}
-static int ddebug_exec_query(char *query_string, const char *modname)
+static int ddebug_exec_query(char *query_string, const char *modname, void *tracer)
{
struct flag_settings modifiers = {};
struct ddebug_query query = {};
@@ -505,7 +538,7 @@ static int ddebug_exec_query(char *query_string, const char *modname)
return -EINVAL;
}
/* actually go and implement the change */
- nfound = ddebug_change(&query, &modifiers);
+ nfound = ddebug_change(&query, &modifiers, tracer);
vpr_info_dq(&query, nfound ? "applied" : "no-match");
return nfound;
@@ -516,7 +549,7 @@ static int ddebug_exec_query(char *query_string, const char *modname)
* last error or number of matching callsites. Module name is either
* in param (for boot arg) or perhaps in query string.
*/
-static int ddebug_exec_queries(char *query, const char *modname)
+static int __ddebug_exec_queries(char *query, const char *modname, void *tracer)
{
char *split;
int i, errs = 0, exitcode = 0, rc, nfound = 0;
@@ -532,7 +565,7 @@ static int ddebug_exec_queries(char *query, const char *modname)
vpr_info("query %d: \"%s\" %s\n", i, query, (modname) ? modname : "");
- rc = ddebug_exec_query(query, modname);
+ rc = ddebug_exec_query(query, modname, tracer);
if (rc < 0) {
errs++;
exitcode = rc;
@@ -549,6 +582,22 @@ static int ddebug_exec_queries(char *query, const char *modname)
return nfound;
}
+static int ddebug_exec_queries(const char *query_in, const char *modname, void *tracer)
+{
+ int rc;
+
+ if (!query_in) {
+ pr_err("non-null query/command string expected\n");
+ return -EINVAL;
+ }
+ query = kstrndup(query_in, PAGE_SIZE, GFP_KERNEL);
+ if (!query)
+ return -ENOMEM;
+
+ rc = __ddebug_exec_queries(query, modname, tracer);
+ kfree(query);
+ return rc;
+
/**
* dynamic_debug_exec_queries - select and change dynamic-debug prints
* @query: query-string described in admin-guide/dynamic-debug-howto
@@ -556,25 +605,12 @@ static int ddebug_exec_queries(char *query, const char *modname)
*
* This uses the >/proc/dynamic_debug/control reader, allowing module
* authors to modify their dynamic-debug callsites. The modname is
- * canonically struct module.mod_name, but can also be null or a
+ * canonically struct module.name, but can also be null or a
* module-wildcard, for example: "drm*".
*/
int dynamic_debug_exec_queries(const char *query, const char *modname)
{
- int rc;
- char *qry; /* writable copy of query */
-
- if (!query) {
- pr_err("non-null query/command string expected\n");
- return -EINVAL;
- }
- qry = kstrndup(query, PAGE_SIZE, GFP_KERNEL);
- if (!qry)
- return -ENOMEM;
-
- rc = ddebug_exec_queries(qry, modname);
- kfree(qry);
- return rc;
+ return ddebug_exec_queries(qry, modname, NULL);
}
EXPORT_SYMBOL_GPL(dynamic_debug_exec_queries);
@@ -603,7 +639,7 @@ int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
}
rc = kstrtoul(instr, 0, &inbits);
if (rc) {
- pr_err("set_dyndbg: failed\n");
+ pr_err("set_dyndbg: bad input: %s\n", instr);
return rc;
}
vpr_info("set_dyndbg: input 0x%lx\n", inbits);
@@ -612,7 +648,7 @@ int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
snprintf(query, FMT_QUERY_SIZE, "format '^%s' %cp", bitmap->prefix,
test_bit(i, &inbits) ? '+' : '-');
- matches = ddebug_exec_queries(query, KP_MOD_NAME);
+ matches = __ddebug_exec_queries(query, KP_MOD_NAME, NULL);
v2pr_info("bit-%d: %d matches on '%s'\n", i, matches, query);
totct += matches;
@@ -703,8 +739,20 @@ void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
vaf.fmt = fmt;
vaf.va = &args;
- printk(KERN_DEBUG "%s%pV", dynamic_emit_prefix(descriptor, buf), &vaf);
+ if (descriptor->flags & _DPRINTK_ENABLED)
+ dynamic_emit_prefix(descriptor, buf);
+
+ if (descriptor->flags & _DPRINTK_FLAGS_PRINT)
+ printk(KERN_DEBUG "%s%pV", buf, &vaf);
+
+ if (descriptor->flags & _DPRINTK_FLAGS_PRINT_TRACE) {
+ if (descriptor->tracer) {
+ (*descriptor->tracer)("%s:%ps %pV", buf,
+ __builtin_return_address(0), &vaf);
+ }
+ /* else shouldn't matter, but maybe for consistency */
+ }
va_end(args);
}
EXPORT_SYMBOL(__dynamic_pr_debug);
@@ -849,7 +897,7 @@ static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
return PTR_ERR(tmpbuf);
vpr_info("read %d bytes from userspace\n", (int)len);
- ret = ddebug_exec_queries(tmpbuf, NULL);
+ ret = __ddebug_exec_queries(tmpbuf, NULL, NULL);
kfree(tmpbuf);
if (ret < 0)
return ret;
@@ -1055,7 +1103,7 @@ static int ddebug_dyndbg_param_cb(char *param, char *val,
if (strcmp(param, "dyndbg"))
return on_err; /* determined by caller */
- ddebug_exec_queries((val ? val : "+p"), modname);
+ __ddebug_exec_queries((val ? val : "+p"), modname, NULL);
return 0; /* query failure shouldn't stop module load */
}
@@ -1190,7 +1238,7 @@ static int __init dynamic_debug_init(void)
/* apply ddebug_query boot param, dont unload tables on err */
if (ddebug_setup_string[0] != '\0') {
pr_warn("ddebug_query param name is deprecated, change it to dyndbg\n");
- ret = ddebug_exec_queries(ddebug_setup_string, NULL);
+ ret = __ddebug_exec_queries(ddebug_setup_string, NULL, NULL);
if (ret < 0)
pr_warn("Invalid ddebug boot param %s\n",
ddebug_setup_string);
@@ -1220,3 +1268,42 @@ early_initcall(dynamic_debug_init);
/* Debugfs setup must be done later */
fs_initcall(dynamic_debug_init_control);
+
+/**
+ * dynamic_debug_register_tracer() - register a "printer" function
+ * @query: query-command string to select callsites getting the function
+ * @modname: added into query-command, may include wildcards
+ * @tracer: &vprintf-ish accepting 3 char* ptrs & a vaf
+ *
+ * Attach a tracer callback callsites selected by the query. If
+ * another tracer is already attached, warn and skip, applying the
+ * rest of the query. This protects existing setups, while allowing
+ * maximal coexistence of (mostly) non-competing listeners. RFC.
+ *
+ * Returns: <0 error
+ * >=0 matches on query, not changes by query
+ */
+int dynamic_debug_register_tracer(const char *query, const char *modname,
+ int (*tracer)(const char *fmt, char *prefix, char *label, struct va_format *vaf))
+{
+ return ddebug_exec_queries(query, modname, tracer);
+}
+EXPORT_SYMBOL(dynamic_debug_register_tracer);
+
+/**
+ * dynamic_debug_unregister_tracer - unregister your "printer" function
+ * @query: query-command string to select callsites to reset
+ * @modname: name of module, or search string (ex: "drm*"), or null
+ * @tracer: reserved to validate unregisters against pirates
+ *
+ * Detach the tracer callback from callsites selected by the query, if
+ * it matches the callsite's tracer. This protects existing setups,
+ * while allowing maximal coexistence of (mostly) non-competing
+ * listeners. RFC.
+ */
+int dynamic_debug_unregister_tracer(const char *query, const char *modname,
+ int (*tracer)(const char *fmt, char *prefix, char *label, struct va_format *vaf))
+{
+ return ddebug_exec_queries(query, modname, tracer);
+}
+EXPORT_SYMBOL(dynamic_debug_unregister_tracer);
new file mode 100644
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Kernel module for testing dynamic_debug
+ *
+ * Author:
+ * Jim Cromie <jim.cromie@gmail.com>
+ */
+
+/*
+ * test-setup:
+ * - use register_tracer to attach a test harness
+ * - a custom trace_printer which counts invocations of enabled pr_debugs
+ * - a DUT (device under test), calling categorized pr_debugs
+ * test-run:
+ * - manipulate the pr_debugs' enablements -> match_ct
+ * - call event generator with loop-ct
+ * its pr_debug()s are Traced: trace_ct++
+ * - count and compare: mainly trace_ct, but also match_ct
+ */
+
+#include <linux/module.h>
+
+static int trace_ct; /* the state var */
+static int test_ct;
+static int errors;
+
+static int verbose;
+module_param_named(verbose, verbose, int, 0444);
+MODULE_PARM_DESC(verbose, "notice on tracer");
+
+static int __test_resv;
+module_param_named(test_reserve, __test_resv, int, 0444);
+MODULE_PARM_DESC(test_reserve, "test 'reservation' against 'poaching'\n");
+
+static int __broken_tracer;
+module_param_named(broken_tracer, __broken_tracer, int, 0444);
+MODULE_PARM_DESC(broken_tracer,
+ "use broken tracer, recursing with pr_debug\n"
+ "\tonly works at modprobe time\n");
+
+static int good_tracer(const char *decorator, char *prefix, char *label, struct va_format *vaf)
+{
+ trace_ct++;
+ if (verbose)
+ pr_notice("my_tracer: %pV", vaf);
+ return 0;
+}
+
+static int bad_tracer(const char *decorator, char *prefix, char *label, struct va_format *vaf)
+{
+ /* dont try pr_debug, it recurses back here */
+ pr_debug("oops! recursion, crash?\n");
+ return 0;
+}
+
+static int (*my_tracer)
+ (const char *decorator, char *prefix, char *label, struct va_format *vaf);
+
+static void pick_tracer(void)
+{
+ if (__broken_tracer)
+ my_tracer = bad_tracer;
+ else
+ my_tracer = good_tracer;
+}
+
+/* call pr_debug (4 * reps) + 2 times, for tracer side-effects */
+static void DUT(int reps)
+{
+ int i;
+
+ pr_debug("Entry:\n");
+ pr_info(" DUT %d time(s)\n", reps);
+ for (i = 0; i < reps; i++) {
+ pr_debug("hi: %d\n", i);
+ pr_debug("mid: %d\n", i);
+ pr_debug("low: %d\n", i);
+ pr_debug("low:lower: %d subcategory test\n", i);
+ }
+ pr_debug("Exit:\n");
+}
+
+struct test_spec {
+ int matches; /* expected rc from applying qry */
+ int loops; /* passed to DUT */
+ int hits; /* should match trace_ct after gen */
+ const char *mod; /* Anyof: wildcarded-string, null, &mod.name */
+ const char *qry; /* echo $qry > control */
+ const char *story; /* test purpose explanation progress */
+};
+
+static void expect_count(struct test_spec *t)
+{
+ test_ct++;
+ if (trace_ct != t->hits) {
+ pr_err("fail#%d: got %d != %d by \"%s\"\tfor \"%s\"\n",
+ test_ct, trace_ct, t->hits, t->qry, t->story);
+ errors++;
+ } else
+ pr_info("pass#%d, hits %d, on \"%s\"\n", test_ct, t->hits, t->story);
+
+ trace_ct = 0;
+}
+
+static void expect_matches(int got, struct test_spec *t)
+{
+ if (got != t->matches) {
+ pr_warn(" nok: got %d != %d on \"%s\"\n", got, t->matches, t->qry);
+ errors++;
+ } else
+ pr_info(" ok: %d matches by \"%s\"\t for \"%s\"\n", got, t->qry, t->story);
+}
+
+static void do_test_spec(struct test_spec *t)
+{
+ int match_count;
+
+ match_count = dynamic_debug_exec_queries(t->qry, t->mod);
+ if (match_count < 0) {
+ pr_err("exec-queries fail rc:%d\n", match_count);
+ return;
+ }
+ expect_matches(match_count, t);
+ DUT(t->loops);
+ expect_count(t);
+}
+
+static const char modnm[] = "test_dynamic_debug";
+
+static void do_register_test(struct test_spec *t, int deep)
+{
+ int match_count;
+
+ pr_debug("enter: %s\n", t->story);
+ if (deep)
+ pr_debug("register good tracer\n");
+
+ match_count = dynamic_debug_register_tracer(t->qry, t->mod, good_tracer);
+ if (match_count < 0) {
+ pr_err("exec-queries fail rc:%d\n", match_count);
+ return;
+ }
+ expect_matches(match_count, t);
+ DUT(t->loops);
+ expect_count(t);
+
+ if (!deep)
+ return;
+
+ pr_debug("unregister bad tracer\n");
+ match_count = dynamic_debug_unregister_tracer(t->qry, t->mod, bad_tracer);
+ if (match_count < 0) {
+ pr_err("exec-queries fail rc:%d\n", match_count);
+ return;
+ }
+ expect_matches(match_count, t);
+ DUT(t->loops);
+ expect_count(t);
+
+ pr_debug("unregister good tracer\n");
+ match_count = dynamic_debug_unregister_tracer(t->qry, t->mod, good_tracer);
+ if (match_count < 0) {
+ pr_err("exec-queries fail rc:%d\n", match_count);
+ return;
+ }
+ expect_matches(match_count, t);
+ DUT(t->loops);
+ expect_count(t);
+}
+
+struct test_spec registry_tests[] = {
+
+ /* matches, loops, hits, modname, query, story */
+ { 6, 1, 0, modnm, "func DUT +_", "probe: DUT 1" },
+ { 6, 1, 2+4, modnm, "func DUT +T", "enable (T)" },
+ { 6, 2, 10, modnm, "func DUT -_", "probe: DUT 2" },
+ { 6, 3, 14, modnm, "func DUT +T", "over-enable, ok" },
+ { 6, 2, 10, modnm, "func DUT -_", "probe: DUT 3" },
+ { 6, 3, 0, modnm, "func DUT -T", "disable" },
+
+ /* 5 other callsites here */
+ { 11, 1, 0, modnm, "+_", "probe: whole module" },
+ { 11, 5, 22, modnm, "+T", "enable (T) whole module" },
+ { 11, 1, 7, modnm, "+T", "re-enable whole module" },
+ { 11, 3, 1, modnm, "-T", "disable whole module" },
+
+ { 3, 2, 0, modnm, "func test_* +_", "probe: count test_*" },
+ { 3, 2, 0, modnm, "func test_* +_", "probe: count test_*" },
+
+ /* terminate registry tests in a known T state */
+ { 6, 3, 14, modnm, "func DUT +T", "enable just function" },
+};
+
+/* these tests rely on register stuff having been done ?? */
+struct test_spec exec_tests[] = {
+ /*
+ * preferred use of exec_queries(qry, modnm) is with true
+ * modnm, since that removes 'module $modnm' from the query
+ * string. (supports modprobe $modname dyndbg=+p).
+ *
+ * But start the old way. with Ts enabled.
+ */
+ { 6, 1, 6, NULL, "module test_dynamic_debug func DUT +p",
+ "Hello! using original module-in-query style" },
+
+ { 11, 1, 6, modnm, "+p", "enable (p) whole module, run DUT 1x" },
+ { 11, 1, 0, modnm, "-p", "disable (p) whole module, run DUT(1x)" },
+
+ { 6, 4, 18, modnm, "func DUT +T", "enable (T) DUT(4)" },
+
+ { 1, 4, 14, modnm, "format '^hi:' -T", "disable 1 callsite" },
+ { 1, 4, 10, modnm, "format '^mid:' -T", "disable 1 callsite" },
+ { 1, 4, 10, modnm, "format '^mid:' -T", "re-disable" },
+ { 1, 5, 12, modnm, "format '^mid:' -T", "re-disable with more loops" },
+ { 2, 4, 2, modnm, "format '^low:' -T", "disable with subclass" },
+ { 1, 4, 2, modnm, "format '^low: ' -T", "re-disable, exclude subclass" },
+ { 1, 4, 6, modnm, "format '^low: ' +T", "enable, exclude subclass" },
+ { 1, 4, 10, modnm, "format '^low:lower:' +T", "enable the subclass" },
+ { 1, 6, 14, modnm, "format '^low:lower:' +T", "re-enable the subclass" },
+};
+
+struct test_spec ratelimit_tests[] = {
+ { 6, 3000, 0, modnm, "func DUT +Tr" }
+};
+
+static void do_test_vec(struct test_spec *t, int len)
+{
+ int i;
+
+ for (i = 0; i < len; i++, t++)
+ do_test_spec(t);
+}
+
+static void test_all(void)
+{
+ int i;
+
+ pr_debug("Entry:\n");
+ pick_tracer();
+
+ for (i = 0; i < ARRAY_SIZE(registry_tests); i++)
+ ; //do_register_test(®istry_tests[i], __test_resv);
+
+ for (i = 0; i < ARRAY_SIZE(registry_tests); i++)
+ do_register_test(®istry_tests[i], 0);
+
+ do_test_vec(exec_tests, ARRAY_SIZE(exec_tests));
+ do_test_vec(ratelimit_tests, ARRAY_SIZE(ratelimit_tests));
+}
+
+static void report(char *who)
+{
+ if (errors)
+ pr_err("%s: failed %d of %d tests\n", who, errors, test_ct);
+ else
+ pr_notice("%s: passed %d tests\n", who, test_ct);
+}
+
+static int __init test_dynamic_debug_init(void)
+{
+ pr_debug("Init:\n");
+
+ test_all();
+ report("complete");
+
+ return 0;
+}
+
+static void __exit test_dynamic_debug_exit(void)
+{
+ report("exit");
+ pr_debug("Exit:");
+}
+
+module_init(test_dynamic_debug_init);
+module_exit(test_dynamic_debug_exit);
+
+MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
+MODULE_LICENSE("GPL");
Sean Paul seanpaul@chromium.org proposed, in https://patchwork.freedesktop.org/series/78133/ drm/trace: Mirror DRM debug logs to tracefs That patchset's objective is to be able to independently steer some of the debug stream to an alternate tracing destination, by splitting drm_debug_enabled() into syslog & trace flavors, and enabling them separately with a drm.debug_trace knob. 2 advantages are identified: - syslog is heavyweight, alternate stream is lighter - steering selected categories separately means less traffic Dynamic-Debug can do this better: 1- all work is behind jump-label's NOOP, Zero overhead when off. 2- perfect site selectivity, no unwanted traffic. drm's debug categories are a general classification system, not one tailored to pick out the exact pool of pr_debugs to watch/trace. With drm.debug built on dyndbg, the given "drm:<cat>:" system can be used to select a base trace-set, which can then be adjusted +/-, and/or augmented with unrelated pr_debugs that just happen to be useful. And this tweaking can be done at the command-line, and reduced to a script. Then the string-prefix "drm:<cat>:" system can be extended to suit. The basic elements: - add a new struct _ddebug member: (*tracer)(char *format, ...) - add a new T flag to enable tracer - adjust the static-key-enable/disable condition for (p|T) - if (p) before printk, since T enables too. - if (T) call tracer if its true = int dynamic_debug_register_tracer(query, modname, tracer); = int dynamic_debug_unregister_tracer(query, modname, cookie); This new interface lets clients set/unset a tracer function on each callsite matching the query, for example: "drm:atomic:fail:". Clients must unregister the same callsites they register, allowing protection of each client's dyndbg-state setup against overwrites by others, while allowing maximal sharing of 1 slot/callsite. The internal call-chain gets some rework: it gets new void* tracer param, which dynamic_debug_exec_queries() hides from public. And convert ddebug_exec_queries() to wrap __ddebug_exec_queries(), and move the query copy code to it. public: passing down: dynamic_debug_(un)register_tracer tracer dynamic_debug_exec_queries tracer=NULL calling: ddebug_exec_queries copies ro-query, tracer __ddebug_exec_queries modifies query, tracer ddebug_exec_query modifies query, tracer Then adjust most ddebug_exec_queries users to __ddebug_exec_queries Intended Behavior: (things are in flux, RFC) - register sets empty slot, doesn't overwrite the query selects callsites, and sets +T (grammar requires +-action) - register allows same-tracer over-set wo warn 2nd register can then enable superset, subset, disjoint set - unregister clears slot if it matches cookie/tracer query selects set, -T (as tested) tolerates over-clears - dd-exec-queries(+/-T) can modify the enablements not sure its needed, but it falls out.. The code is currently in-line in ddebug_change(), to be moved to separate fn, rc determines flow, may also veto/alter changes by altering flag-settings - tbd. TBD: Im not sure what happens when exec-queries(+T) hits a site wo a tracer (silence I think. maybe not ideal). SELFTEST: test_dynamic_debug.ko: Uses the tracer facility to implement a selftest: - DUT(x) calls a set of categorized pr_debugs x times - A custom tracer counts the number of calls (of T-enabled pr_debugs), - test registers the tracer on the function, then iteratively: manipulates dyndbg states via query-cmds calls DUT(x) counts enabled callsite executions reports mismatches - modprobe test_dynamic_debug broken_tracer=1 attaches a broken tracer: recursive on pr_debug Bad Things Happen. has thrown me interesting panics. This needs more work. RFC. waste of time due to use_bad_tracer properties ? NOTES: Next step: replace tracer member with a hashtable lookup, done only when T. Registration then becomes populating the hashtable; mod->name would make a good key, which would limit tracer mapping granularity to 1 registrant per module, but not enablement, which is still the per-callsite bit. ERRORS (or WARNINGS): It should be an error to +T a callsite which has no aux_print set (ie already registered with a query that selected that callsite). This tacitly enforces registration. Then +T,-T can toggle those aux_print callsites (or subsets of them) to tailor the debug-stream for the purpose. Controlling flow is the best work limiter. Signed-off-by: Jim Cromie <jim.cromie@gmail.com> --- v5: (this patch sent after (on top of) v4) . fix "too many arguments to function", and name the args: int (*aux_print)(const char *fmt, char *prefix, char *label, void *); prefix : is a slot for dynamic_emit_prefix, or for custom buffer insert label : for builtin-caller used by drm-trace-print void* : vaf, add type constraint later. . fix printk (to syslog) needs if (+p), since +T also enables . add prototypes for un/register_aux_print . change iface names: s/aux_print/tracer/ . also s/trace_print/tracer/ . struct va_format *vaf - tighten further ? v6: (this version) . add test module . add mod arg to *register, following exec_queries pattern . move code off file bottom to "better" spot . move kdoc to c from h __dxq --- include/linux/dynamic_debug.h | 12 +- lib/Kconfig.debug | 11 ++ lib/Makefile | 1 + lib/dynamic_debug.c | 145 ++++++++++++++---- lib/test_dynamic_debug.c | 279 ++++++++++++++++++++++++++++++++++ 5 files changed, 418 insertions(+), 30 deletions(-) create mode 100644 lib/test_dynamic_debug.c