[PATCH v3 11/19] dyndbg-API: specialize DYNDBG_CLASSMAP_(DEFINE|USE)

From: Jim Cromie
Date: Wed Jan 25 2023 - 15:38:57 EST

Now that the DECLARE_DYNDBG_CLASSMAP macro has been split into
DYNDBG_CLASSMAP_DEFINE and DYNDBG_CLASSMAP_USE, lets differentiate
them according to their separate jobs.

Dyndbg's existing __dyndbg_classes[] section does:

. catalogs the classmaps defined by the module (or builtin modules)
. authorizes dyndbg to >control those class'd prdbgs for the module.

This patch adds __dyndbg_class_refs[] section:

. catalogs refs/uses of the classmap definitions.
. authorizes dyndbg to >control those class'd prdbgs in ref'g module.
. maps the client module to classmap definitions
drm-drivers and helpers are clients.
this allows dyndbg to apply drm.debug to the client module, when added.

The distinction of the 2 roles yields these gains:

It follows the define-once-declare-elsewhere pattern that K&R gave us,
dumping the weird coordinated-changes-by-identical-classmaps API.

It allows separate handling of class-refs, to find the classed
kernel-params (if any) using this classmap, and propagate their
settings to the class'd prdbgs in the client module.

It fixes the chicken-egg problem that DRM_USE_DYNAMIC_DEBUG=y has; the
new type allows dyndbg to handle class-refs found while adding the
module.

The new DYNDBG_CLASSMAP_* macros add records to the sections:

DYNDBG_CLASSMAP_DEFINE:
invoked just once per sub-system.
for drm, its drm_print, where drm.debug is exposed.
defines the classmap, names "DRM_UT_*", maps to class_id's
authorizes dyndbg to exert >control
populates __dyndbg_classes[] "section", __used.
exports the classmap.

DYNDBG_CLASSMAP_USE:
invoked by modules using classmaps defined & exported elsewhere
populates __dyndbg_class_refs[] "section", __used.
maps client-module name to the extern'd classmap.
has client-name, so dyndbg can recognize loading client modules.

To support this, a few data changes:

. struct ddebug_class_user
contains: user-module-name, ref to classmap-defn
encodes drm-driver's use of a classmap, allowing lookup

struct ddebug_info gets 2 new fields to encapsulate the new section:
class_refs, num_class_refs.
set by dynamic_debug_init() for builtins.
or by kernel/module/main:load_info() for loadable modules.

vmlinux.lds.h: new BOUNDED_SECTION for class-refs, with linker symbols

dynamic_debug.c: changes to:
setup - in/under ddebug_add_module(), immediately following
prdbg enables - in/under ddebug_change(), further below

ddebug_attach_module_classes() - largely unchanged:
called from ddebug_add_module
finds classmaps whose .mod_name matches module being added.
attaches them to the module's ddebug_table.
minor tweaks for code regularity, debug output

ddebug_attach_client_module_classes() - new fn:
. like above, but works class-refs, not classes.
. called from ddebug_add_module, after list-add to ddebug-tables.
this lets ddebug_change find it to apply the settings
. scans class-refs, for the block "owned" by the module being added.
for builtins, its N consecutive of many. for loadables, N of N
. calls ddebug_apply_parents_params() for each.

ddebug_apply_parents_params(new fn)

scans module's/builtin kernel-params, calls ddebug_match_attach_kparam
for each to find the params/sysfs-nodes using a classmap.

ddebug_match_apply_kparam(new fn):

1st, it tests the kernel-param.ops is dyndbg's; this guarantees that
the attached arg is a struct ddebug_class_param, which has a ref to
the param's state, and to the classmap.

2nd, it requires that the classmap attached to the kparam is the one
were called for; modules can use many separate classmaps (as
test_dynamic_debug does).

Then apply the "parent" kparam's setting to the client.

The ddebug_change() support:

ddebug_find_valid_class(): This does the search over classmaps,
looking for the class FOO echo'd to >control. So now it searches over
__dyndbg_class_refs[] after __dyndbg_classes[].

ddebug_apply_class_bitmap(): now quieter when not changing things.

ddebug_class_name(): return class-names for defined AND used classes.

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
--
v3 - s/BUG_ON/WARN_ON/ in __dyndbg_class_refs handling
simpler args in callchain
v2 - rebase past merge conflicts
---
include/asm-generic/vmlinux.lds.h | 1 +
include/linux/dynamic_debug.h | 39 ++++---
kernel/module/main.c | 3 +
lib/dynamic_debug.c | 170 ++++++++++++++++++++++++++----
4 files changed, 179 insertions(+), 34 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 659bf3b31c91..5beb0321613e 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -373,6 +373,7 @@
/* implement dynamic printk debug */ \
. = ALIGN(8); \
BOUNDED_SECTION_BY(__dyndbg_classes, ___dyndbg_classes) \
+ BOUNDED_SECTION_BY(__dyndbg_class_refs, ___dyndbg_class_refs) \
BOUNDED_SECTION_BY(__dyndbg, ___dyndbg) \
LIKELY_PROFILE() \
BRANCH_PROFILE() \
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 1cdfd62fd2e4..397ac8294230 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -81,8 +81,8 @@ enum ddebug_class_map_type {
};

struct ddebug_class_map {
- struct module *mod;
- const char *mod_name; /* needed for builtins */
+ const struct module *mod; /* NULL for builtins */
+ const char *mod_name;
const char **class_names;
const int length;
const int base; /* index of 1st .class_id, allows split/shared space */
@@ -99,8 +99,8 @@ struct ddebug_class_map {
* @classes: class-names used to control class'd prdbgs
*/
#define DYNDBG_CLASSMAP_DEFINE(_var, _maptype, _base, ...) \
- static const char *_var##_classnames[] = { __VA_ARGS__ }; \
- static struct ddebug_class_map __aligned(8) __used \
+ const char *_var##_classnames[] = { __VA_ARGS__ }; \
+ struct ddebug_class_map __aligned(8) __used \
__section("__dyndbg_classes") _var = { \
.mod = THIS_MODULE, \
.mod_name = KBUILD_MODNAME, \
@@ -108,24 +108,37 @@ struct ddebug_class_map {
.map_type = _maptype, \
.length = ARRAY_SIZE(_var##_classnames), \
.class_names = _var##_classnames, \
- }
+ }; \
+ EXPORT_SYMBOL(_var)

-/*
- * refer to the classmap instantiated once, by the macro above. This
- * distinguishes the multiple users of drm.debug from the single
- * definition, allowing them to specialize. ATM its a pass-thru, but
- * it should help regularize the admittedly wierd sharing by identical
- * definitions.
+struct ddebug_class_user {
+ char *user_mod_name;
+ struct ddebug_class_map *map;
+};
+/**
+ * DYNDBG_CLASSMAP_USE - Use a classmap DEFINEd in another module.
+ * This lets dyndbg initialize the dependent module's prdbgs from the
+ * other module's controlling sysfs node.
*/
-#define DYNDBG_CLASSMAP_USE(_var, _maptype, _base, ...) \
- DYNDBG_CLASSMAP_DEFINE(_var, _maptype, _base, __VA_ARGS__)
+#define DYNDBG_CLASSMAP_USE(_var, ...) \
+ DYNDBG_CLASSMAP_USE_(_var, __UNIQUE_ID(ddebug_class_user), \
+ __VA_ARGS__)
+#define DYNDBG_CLASSMAP_USE_(_var, _uname, ...) \
+ extern struct ddebug_class_map _var; \
+ static struct ddebug_class_user __used \
+ __section("__dyndbg_class_refs") _uname = { \
+ .user_mod_name = KBUILD_MODNAME, \
+ .map = &_var, \
+ }

/* encapsulate linker provided built-in (or module) dyndbg data */
struct _ddebug_info {
struct _ddebug *descs;
struct ddebug_class_map *classes;
+ struct ddebug_class_user *class_refs;
unsigned int num_descs;
unsigned int num_classes;
+ unsigned int num_class_refs;
};

struct ddebug_class_param {
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 48568a0f5651..cfccbd06ae2d 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2113,6 +2113,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
sizeof(*info->dyndbg.descs), &info->dyndbg.num_descs);
info->dyndbg.classes = section_objs(info, "__dyndbg_classes",
sizeof(*info->dyndbg.classes), &info->dyndbg.num_classes);
+ info->dyndbg.class_refs = section_objs(info, "__dyndbg_class_refs",
+ sizeof(*info->dyndbg.class_refs),
+ &info->dyndbg.num_class_refs);

return 0;
}
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index b51f4bde6198..57efd435dda7 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -43,13 +43,16 @@ extern struct _ddebug __start___dyndbg[];
extern struct _ddebug __stop___dyndbg[];
extern struct ddebug_class_map __start___dyndbg_classes[];
extern struct ddebug_class_map __stop___dyndbg_classes[];
+extern struct ddebug_class_user __start___dyndbg_class_refs[];
+extern struct ddebug_class_user __stop___dyndbg_class_refs[];

struct ddebug_table {
struct list_head link;
const char *mod_name;
struct _ddebug *ddebugs;
struct ddebug_class_map *classes;
- unsigned int num_ddebugs, num_classes;
+ struct ddebug_class_user *class_refs;
+ unsigned int num_ddebugs, num_classes, num_class_refs;
};

struct ddebug_query {
@@ -147,21 +150,36 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
query->first_lineno, query->last_lineno, query->class_string);
}

+#define vpr_dt_info(dt, _msg, ...) \
+ v2pr_info(_msg " module:%s nd:%d nc:%d nu:%d\n", ##__VA_ARGS__, \
+ dt->mod_name, dt->num_ddebugs, dt->num_classes, dt->num_class_refs)
+
#define __outvar /* filled by callee */
static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table const *dt,
const char *class_string,
__outvar int *class_id)
{
struct ddebug_class_map *map;
+ struct ddebug_class_user *cli;
int i, idx;

- for (map = dt->classes, i = 0; i < dt->num_classes; i++, map++) {
+ for (i = 0, map = dt->classes; i < dt->num_classes; i++, map++) {
idx = match_string(map->class_names, map->length, class_string);
if (idx >= 0) {
*class_id = idx + map->base;
+ vpr_dt_info(dt, "good-class: %s.%s ", map->mod_name, class_string);
return map;
}
}
+ for (i = 0, cli = dt->class_refs; i < dt->num_class_refs; i++, cli++) {
+ idx = match_string(cli->map->class_names, cli->map->length, class_string);
+ if (idx >= 0) {
+ *class_id = idx + cli->map->base;
+ vpr_dt_info(dt, "class-ref: %s.%s ",
+ cli->user_mod_name, class_string);
+ return cli->map;
+ }
+ }
*class_id = -ENOENT;
return NULL;
}
@@ -590,9 +608,10 @@ static int ddebug_exec_queries(char *query, const char *modname)
return nfound;
}

-/* apply a new bitmap to the sys-knob's current bit-state */
+/* apply a new class-param setting */
static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
- const unsigned long *new_bits, const unsigned long *old_bits,
+ const unsigned long *new_bits,
+ const unsigned long *old_bits,
const char *query_modname)
{
#define QUERY_SIZE 128
@@ -601,8 +620,9 @@ static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
int matches = 0;
int bi, ct;

- v2pr_info("apply bitmap: 0x%lx to: 0x%lx for %s\n", *new_bits, *old_bits,
- query_modname ?: "");
+ if (*new_bits != *old_bits)
+ v2pr_info("apply bitmap: 0x%lx to: 0x%lx for %s\n", *new_bits,
+ *old_bits, query_modname ?: "'*'");

for (bi = 0; bi < map->length; bi++) {
if (test_bit(bi, new_bits) == test_bit(bi, old_bits))
@@ -617,8 +637,9 @@ static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
v2pr_info("bit_%d: %d matches on class: %s -> 0x%lx\n", bi,
ct, map->class_names[bi], *new_bits);
}
- v2pr_info("applied bitmap: 0x%lx to: 0x%lx for %s\n", *new_bits, *old_bits,
- query_modname ?: "");
+ if (*new_bits != *old_bits)
+ v2pr_info("applied bitmap: 0x%lx to: 0x%lx for %s\n", *new_bits,
+ *old_bits, query_modname ?: "'*'");

return matches;
}
@@ -707,6 +728,7 @@ static int param_set_dyndbg_module_classes(const char *instr,
const struct ddebug_class_map *map = dcp->map;
unsigned long inrep, new_bits, old_bits;
int rc, totct = 0;
+ char *nl;

switch (map->map_type) {

@@ -720,7 +742,10 @@ static int param_set_dyndbg_module_classes(const char *instr,
/* numeric input, accept and fall-thru */
rc = kstrtoul(instr, 0, &inrep);
if (rc) {
- pr_err("expecting numeric input: %s > %s\n", instr, KP_NAME(kp));
+ nl = strchr(instr, '\n');
+ if (nl)
+ *nl = '\0';
+ pr_err("expecting numeric input, not: %s > %s\n", instr, KP_NAME(kp));
return -EINVAL;
}
break;
@@ -1113,12 +1138,17 @@ static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
static const char *ddebug_class_name(struct ddebug_table *dt, struct _ddebug *dp)
{
struct ddebug_class_map *map = dt->classes;
+ struct ddebug_class_user *cli = dt->class_refs;
int i;

for (i = 0; i < dt->num_classes; i++, map++)
if (class_in_range(dp->class_id, map))
return map->class_names[dp->class_id - map->base];

+ for (i = 0; i < dt->num_class_refs; i++, cli++)
+ if (class_in_range(dp->class_id, cli->map))
+ return cli->map->class_names[dp->class_id - cli->map->base];
+
return NULL;
}

@@ -1199,33 +1229,125 @@ static const struct proc_ops proc_fops = {
.proc_write = ddebug_proc_write
};

+
+/*
+ * Find this module's classmaps in a sub/whole-range of the builtin/
+ * modular classmap vector/section. Save the start and length of the
+ * subrange at its edges.
+ */
static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug_info *di)
{
struct ddebug_class_map *cm;
int i, nc = 0;

- /*
- * 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++) {
+ for (i = 0, cm = di->classes; i < di->num_classes; i++, cm++) {

if (!strcmp(cm->mod_name, dt->mod_name)) {
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;
+ v2pr_info("classes[0..]: module:%s base:%d len:%d ty:%d\n",
+ cm->mod_name, cm->base, cm->length, cm->map_type);
}
nc++;
}
}
- if (nc) {
- dt->num_classes = nc;
+ dt->num_classes = nc;
+ if (nc)
vpr_info("module:%s attached %d classes\n", dt->mod_name, nc);
+}
+
+#define vpr_cm_info(cm, _msg, ...) \
+ v2pr_info(_msg " module:%s base:%d len:%d type:%d\n", ##__VA_ARGS__, \
+ cm->mod_name, cm->base, cm->length, cm->map_type)
+
+static void ddebug_match_apply_kparam(const struct kernel_param *kp, struct ddebug_class_user *cli)
+{
+ struct ddebug_class_param *dcp;
+ unsigned long new_bits, old_bits = 0;
+ int totct = 0;
+
+ if (kp->ops != &param_ops_dyndbg_classes)
+ return;
+
+ dcp = (struct ddebug_class_param *)kp->arg;
+
+ if (cli->map == dcp->map) {
+ v2pr_info("found kp:%s =0x%lx", kp->name, *dcp->bits);
+ vpr_cm_info(cli->map, "mapped to:");
+ /*
+ * using apply-bitmap is too low.
+ * param_set_dyndbg_classes uses map_type to sort
+ * levels-to-bits.
+ * param_set_dyndbg_classes is too high, it takes
+ * string inputs.
+ * de-union-ing levels/bits might solve it (partly),
+ * at least simplifying the translation, and possibly
+ * the apply-bitmap fn/iface
+ */
+ new_bits = *dcp->bits;
+ totct += ddebug_apply_class_bitmap(dcp, &new_bits, &old_bits,
+ cli->user_mod_name);
+ }
+}
+
+static void ddebug_apply_parents_params(struct ddebug_class_user *cli)
+{
+ const struct ddebug_class_map *cm = cli->map;
+ const struct kernel_param *kp;
+#if IS_ENABLED(CONFIG_MODULES)
+ int i;
+
+ if (cm->mod) {
+ vpr_cm_info(cm, "loaded class:");
+ for (i = 0, kp = cm->mod->kp; i < cm->mod->num_kp; i++, kp++)
+ ddebug_match_apply_kparam(kp, cli);
+ }
+#endif
+ if (!cm->mod) {
+ vpr_cm_info(cm, "builtin class:");
+ for (kp = __start___param; kp < __stop___param; kp++)
+ ddebug_match_apply_kparam(kp, cli);
}
}

+/*
+ * propagates class-params thru their classmaps to class-users. this
+ * means a query against the dt/module, which means it must be on the
+ * list to be seen by ddebug_change.
+ */
+static void ddebug_attach_client_module_classes(struct ddebug_table *dt, const struct _ddebug_info *di)
+{
+ struct ddebug_class_user *cli;
+ int i, nc = 0;
+
+ /*
+ * For builtins: scan the array, find start/length of this
+ * module's refs, save to dt. For loadables, this is the
+ * whole array.
+ */
+ for (i = 0, cli = di->class_refs; i < di->num_class_refs; i++, cli++) {
+
+ if (WARN_ON(!cli || !cli->map || !cli->user_mod_name))
+ continue;
+
+ if (!strcmp(cli->user_mod_name, dt->mod_name)) {
+
+ v2pr_info("class_ref[%d] %s -> %s\n", i,
+ cli->user_mod_name, cli->map->mod_name);
+
+ if (!nc++)
+ dt->class_refs = cli;
+ }
+ }
+ dt->num_class_refs = nc;
+
+ /* now iterate dt */
+ for (i = 0, cli = dt->class_refs; i < dt->num_class_refs; i++, cli++)
+ ddebug_apply_parents_params(cli);
+
+ vpr_dt_info(dt, "attach-client-module: ");
+}
+
/*
* Allocate a new ddebug_table for the given module
* and add it to the global list.
@@ -1235,7 +1357,8 @@ static int __ddebug_add_module(struct _ddebug_info *di, unsigned int base,
{
struct ddebug_table *dt;

- v3pr_info("add-module: %s.%d sites\n", modname, di->num_descs);
+ v3pr_info("add-module: %s %d sites %d.%d\n", modname, di->num_descs,
+ di->num_classes, di->num_class_refs);
if (!di->num_descs) {
v3pr_info(" skip %s\n", modname);
return 0;
@@ -1258,13 +1381,16 @@ static int __ddebug_add_module(struct _ddebug_info *di, unsigned int base,

INIT_LIST_HEAD(&dt->link);

- if (di->classes && di->num_classes)
+ if (di->num_classes)
ddebug_attach_module_classes(dt, di);

mutex_lock(&ddebug_lock);
list_add_tail(&dt->link, &ddebug_tables);
mutex_unlock(&ddebug_lock);

+ if (di->num_class_refs)
+ ddebug_attach_client_module_classes(dt, di);
+
vpr_info("%3u debug prints in module %s\n", di->num_descs, modname);
return 0;
}
@@ -1390,8 +1516,10 @@ static int __init dynamic_debug_init(void)
struct _ddebug_info di = {
.descs = __start___dyndbg,
.classes = __start___dyndbg_classes,
+ .class_refs = __start___dyndbg_class_refs,
.num_descs = __stop___dyndbg - __start___dyndbg,
.num_classes = __stop___dyndbg_classes - __start___dyndbg_classes,
+ .num_class_refs = __stop___dyndbg_class_refs - __start___dyndbg_class_refs,
};

if (&__start___dyndbg == &__stop___dyndbg) {
--
2.39.1