[RFC PATCH 15/17] dyndbg: ddebug_sanity()

From: Jim Cromie
Date: Mon Dec 05 2022 - 19:36:28 EST

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It appears that, at least for builtin drm,i915 loadable amdgpu, data
in the class_refs section is not properly linked, this works partway
towards isolating the problem.

The "NO CLI" name test is failing.
This version of the report fails with a non-canonical address:
// v2pr_info("NO CLI name on: %s\n", cli->map->mod_name);

[ 0.109299] dyndbg: add-module: main 6 sites 1.3
[ 0.109595] general protection fault, probably for non-canonical address 0x7265766972640000: 0000

fwiw:
$ perl -e ' $a = pack "H8", "7265766972640000"; print "a:<$a>\n"'
a:<revi>

These records are added to __dyndbg_class_refs section by
DYNDBG_CLASSMAP_USE

This patch adds ddebug_sanity(), and calls it 3 times to characterize
what goes wrong and when. It turns out that its contents are wrong
immediately, in 1st step of dynamic_debug_init().

[ 0.107327] dyndbg: classes
[ 0.107537] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 0.107592] dyndbg: class-refs
[ 0.107823] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e35e nm:0000000000000000 nm:(null)
[ 0.108554] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe86 nm:ffffffff834fc4c8 nm:
[ 0.108590] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785aa nm:ffffffff834fc4c8 nm:

Those maps are wrong:

class-refs should all ref the same map, ie class[0]: module:drm.
the nm:s should also show module names of 3 builtin clients of drm.
So things must end poorly.

modprobing the loadable module does better:

bash-5.2# modprobe amdgpu
[ 6645.212706] AMD-Vi: AMD IOMMUv2 functionality not available on this system - This is not a bug.
[ 6645.653124] dyndbg: add-module: amdgpu 4425 sites 0.1
[ 6645.653582] dyndbg: classes
[ 6645.653830] dyndbg: class-refs
[ 6645.654124] dyndbg: class-ref[0]: cli:ffffffffc0a31b90 map:ffffffff834fc4c8 nm:ffffffffc08bc176 nm:amdgpu
[ 6645.654936] dyndbg: classes
[ 6645.655188] dyndbg: class-refs
[ 6645.655450] dyndbg: class-ref[0]: cli:ffffffffc0a31b90 map:ffffffff834fc4c8 nm:ffffffffc08bc176 nm:amdgpu
[ 6645.656246] dyndbg: class_ref[0] amdgpu -> drm
[ 6645.656613] dyndbg: amdgpu needs drm, 0x0
[ 6645.656953] dyndbg: apply bitmap: 0x0 to: 0x0
[ 6645.657322] dyndbg: break on 0/1
[ 6645.657592] dyndbg: 4425 debug prints in module amdgpu

Here, the maps are correct; they ref the class[0] module:drm above.
That said, apply bitmap is wrong.

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>

---

[ 1.210094] dyndbg: add-module: drm 302 sites 1.3
[ 1.210496] dyndbg: classes
[ 1.210674] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.211290] dyndbg: class-refs
[ 1.211548] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.211674] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.212464] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.212675] dyndbg: classes start: class[0]: module:drm base:0 len:10 ty:0
[ 1.213257] dyndbg: builtin class: module:drm base:0 len:10 ty:0
[ 1.213675] dyndbg: controlling kp: drm.drm.debug
[ 1.214087] dyndbg: module:drm attached 1 classes
[ 1.214490] dyndbg: classes
[ 1.214674] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.215291] dyndbg: class-refs
[ 1.215552] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.215674] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.216430] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.216674] dyndbg: NO CLI ffffffff8293e376 7265766972640000
[ 1.217149] dyndbg: 302 debug prints in module drm
[ 1.217549] dyndbg: add-module: drm_kms_helper 95 sites 1.3
[ 1.217674] dyndbg: classes
[ 1.217913] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.218525] dyndbg: class-refs
[ 1.218674] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.219486] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.219674] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.220469] dyndbg: classes
[ 1.220674] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.221324] dyndbg: class-refs
[ 1.221606] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.221674] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.222472] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.222674] dyndbg: NO CLI ffffffff8293e376 7265766972640000
[ 1.223173] dyndbg: 95 debug prints in module drm_kms_helper
[ 1.223675] dyndbg: add-module: drm_display_helper 150 sites 1.3
[ 1.224223] dyndbg: classes
[ 1.224484] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.224676] dyndbg: class-refs
[ 1.224954] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.225674] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.226498] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.226674] dyndbg: classes
[ 1.226931] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.227577] dyndbg: class-refs
[ 1.227674] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.228501] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.228674] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.229443] dyndbg: NO CLI ffffffff8293e376 7265766972640000
[ 1.229674] dyndbg: 150 debug prints in module drm_display_helper
[ 1.230195] dyndbg: add-module: ttm 2 sites 1.3
[ 1.230581] dyndbg: classes
[ 1.230674] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.231291] dyndbg: class-refs
[ 1.231559] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.231674] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.232439] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.232674] dyndbg: classes
[ 1.232915] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.233535] dyndbg: class-refs
[ 1.233674] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.234470] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.234674] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.235427] dyndbg: NO CLI ffffffff8293e376 7265766972640000
[ 1.235674] dyndbg: 2 debug prints in module ttm
[ 1.236079] dyndbg: add-module: i915 1657 sites 1.3
[ 1.236490] dyndbg: classes
[ 1.236674] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.237283] dyndbg: class-refs
[ 1.237545] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.237674] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.238431] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.238674] dyndbg: classes
[ 1.238911] dyndbg: class[0]: module:drm base:0 len:10 ty:0 cm:ffffffff834fc4c8
[ 1.239519] dyndbg: class-refs
[ 1.239674] dyndbg: class-ref[0]: cli:ffffffff834fc508 map:ffffffff8293e376 nm:0000000000000000 nm:(null)
[ 1.240467] dyndbg: class-ref[1]: cli:ffffffff834fc518 map:ffffffff8293fe9e nm:ffffffff834fc4c8 nm:
[ 1.240674] dyndbg: class-ref[2]: cli:ffffffff834fc528 map:ffffffff829785c2 nm:ffffffff834fc4c8 nm:
[ 1.241478] dyndbg: NO CLI ffffffff8293e376 7265766972640000
[ 1.241674] dyndbg: 1657 debug prints in module i915
---
include/linux/dynamic_debug.h | 4 ++--
lib/dynamic_debug.c | 32 +++++++++++++++++++++++++++++++-
2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 6f53a687cb32..2a1199aadab6 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -115,8 +115,8 @@ struct ddebug_class_map {
EXPORT_SYMBOL(_var)

struct ddebug_class_user {
- char *user_mod_name;
- struct ddebug_class_map *map;
+ const char *user_mod_name;
+ const struct ddebug_class_map *map;
};
/**
* DYNDBG_CLASSMAP_USE - refer to a classmap, DEFINEd elsewhere.
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 02f36c553835..46684aa7284d 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1301,7 +1301,8 @@ static void ddebug_attach_client_module_classes(struct ddebug_table *dt, struct
continue;
}
if (!cli->user_mod_name) {
- v2pr_info("NO CLI name\n");
+ v2pr_info("NO CLI name %px %px\n", cli->map, cli->map->mod_name);
+ // v2pr_info("NO CLI name on: %s\n", cli->map->mod_name);
continue;
}

@@ -1325,6 +1326,29 @@ static void ddebug_attach_client_module_classes(struct ddebug_table *dt, struct
}
}

+static void ddebug_sanity(struct _ddebug_info *di)
+{
+ struct ddebug_class_map *cm;
+ struct ddebug_class_user *cli;
+ int i;
+
+ if (di->num_classes)
+ v2pr_info("classes\n");
+
+ for (i = 0, cm = di->classes; i < di->num_classes; i++, cm++) {
+ v2pr_info("class[%d]: module:%s base:%d len:%d ty:%d cm:%px\n",
+ i, cm->mod_name, cm->base, cm->length, cm->map_type, cm);
+ }
+ if (di->num_class_refs)
+ v2pr_info("class-refs\n");
+
+ for (i = 0, cli = di->class_refs; i < di->num_class_refs; i++, cli++) {
+ // cli->map->mod_name will segv
+ v2pr_info("class-ref[%d]: cli:%px map:%px nm:%px nm:%s\n", i, cli,
+ cli->map, cli->user_mod_name, cli->user_mod_name);
+ }
+}
+
/*
* Allocate a new ddebug_table for the given module
* and add it to the global list.
@@ -1357,6 +1381,8 @@ int ddebug_add_module(struct _ddebug_info *di, const char *modname)

INIT_LIST_HEAD(&dt->link);

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

@@ -1364,6 +1390,8 @@ int ddebug_add_module(struct _ddebug_info *di, const char *modname)
list_add_tail(&dt->link, &ddebug_tables);
mutex_unlock(&ddebug_lock);

+ ddebug_sanity(di);
+
if (di->num_class_refs)
ddebug_attach_client_module_classes(dt, di);

@@ -1493,6 +1521,8 @@ static int __init dynamic_debug_init(void)
.num_class_refs = __stop___dyndbg_class_refs - __start___dyndbg_class_refs,
};

+ ddebug_sanity(&di);
+
if (&__start___dyndbg == &__stop___dyndbg) {
if (IS_ENABLED(CONFIG_DYNAMIC_DEBUG)) {
pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
--
2.38.1

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