[PATCH 21/63] dyndbg: allow ddebug_add_module to fail

[Jim Cromie <jim.cromie@xxxxxxxxx>]

To prep for failing modprobe on classid conflicts, upgrade the
call-chain around ddebug_add_module(), in 2 ways:

1. in ddebug_add_module() add local reserved_ids to accumulate
reservations, pass it by ref to ddebug_attach_{,user_}module_classes()
so they can examine the reservations as they work.

2. return int from both ddebug_attach_{,user_}module_classes(), up to
ddebug_add_module(), then to ddebug_module_notify().

No conflicts are currently detected or returned.

TBD: This is updated further by hoisting the reservation-check, which
obsoletes part of 2, creating churn, maybe squash it away.

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 lib/dynamic_debug.c | 40 +++++++++++++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 16c9b752822b..0ef243e30663 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1216,8 +1216,9 @@ static void ddebug_apply_params(const struct ddebug_class_map *cm, const char *m
  * 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,
-					 const struct _ddebug_info *di)
+static int ddebug_attach_module_classes(struct ddebug_table *dt,
+					const struct _ddebug_info *di,
+					u64 *reserved_ids)
 {
 	struct ddebug_class_map *cm;
 	int i, nc = 0;
@@ -1230,13 +1231,14 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt,
 		}
 	}
 	if (!nc)
-		return;
+		return 0;
 
 	vpr_info("module:%s attached %d classes\n", dt->mod_name, nc);
 	dt->info.maps.len = nc;
 
 	for_subvec(i, cm, &dt->info, maps)
 		ddebug_apply_params(cm, cm->mod_name);
+	return 0;
 }
 
 /*
@@ -1244,8 +1246,9 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt,
  * 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_user_module_classes(struct ddebug_table *dt,
-					      const struct _ddebug_info *di)
+static int ddebug_attach_user_module_classes(struct ddebug_table *dt,
+					      const struct _ddebug_info *di,
+					      u64 *reserved_ids)
 {
 	struct ddebug_class_user *cli;
 	int i, nc = 0;
@@ -1266,7 +1269,7 @@ static void ddebug_attach_user_module_classes(struct ddebug_table *dt,
 		}
 	}
 	if (!nc)
-		return;
+		return 0;
 
 	dt->info.users.len = nc;
 
@@ -1275,6 +1278,7 @@ static void ddebug_attach_user_module_classes(struct ddebug_table *dt,
 		ddebug_apply_params(cli->map, cli->mod_name);
 
 	vpr_dt_info(dt, "attach-client-module: ");
+	return 0;
 }
 
 /*
@@ -1284,6 +1288,8 @@ static void ddebug_attach_user_module_classes(struct ddebug_table *dt,
 static int ddebug_add_module(struct _ddebug_info *di, const char *modname)
 {
 	struct ddebug_table *dt;
+	u64 reserved_ids = 0;
+	int rc;
 
 	if (!di->descs.len)
 		return 0;
@@ -1306,16 +1312,23 @@ static int ddebug_add_module(struct _ddebug_info *di, const char *modname)
 
 	INIT_LIST_HEAD(&dt->link);
 
-	if (di->maps.len)
-		ddebug_attach_module_classes(dt, di);
-
+	if (di->maps.len) {
+		rc = ddebug_attach_module_classes(dt, di, &reserved_ids);
+		if (rc) {
+			kfree(dt);
+			return rc;
+		}
+	}
 	mutex_lock(&ddebug_lock);
 	list_add_tail(&dt->link, &ddebug_tables);
 	mutex_unlock(&ddebug_lock);
 
-	if (di->users.len)
-		ddebug_attach_user_module_classes(dt, di);
 
+	if (di->users.len) {
+		rc = ddebug_attach_user_module_classes(dt, di, &reserved_ids);
+		if (rc)
+			return rc;
+	}
 	vpr_info("%3u debug prints in module %s\n", di->descs.len, modname);
 	return 0;
 }
@@ -1400,6 +1413,11 @@ static int ddebug_module_notify(struct notifier_block *self, unsigned long val,
 	switch (val) {
 	case MODULE_STATE_COMING:
 		ret = ddebug_add_module(&mod->dyndbg_info, mod->name);
+		if (ret == -EINVAL) {
+			pr_err("conflicting dyndbg-classmap reservations\n");
+			ddebug_remove_module(mod->name);
+			break;
+		}
 		if (ret)
 			WARN(1, "Failed to allocate memory: dyndbg may not work properly.\n");
 		break;
-- 
2.48.1