[PATCH v12 21/40] dyndbg: hoist classmap-filter-by-modname up to ddebug_add_module

[Jim Cromie via B4 Relay <devnull+jim.cromie.gmail.com@kernel.org>]

From: Jim Cromie <jim.cromie@gmail.com>

The body of ddebug_attach_module_classes() is just a code-block that
finds the contiguous subrange of classmaps matching on modname, and
saves it into the ddebug_table's info record.

Implement this block in a macro to accommodate different component
vectors in the "box" (as named in the for_subvec macro).  We will
reuse this macro shortly.

And hoist its invocation out of ddebug_attach_module_classes() up into
ddebug_add_module().  This moves the filtering step up closer to
dynamic_debug_init(), which already segments the builtin pr_debug
descriptors on their mod_name boundaries.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
v8: set maps.len = nc unconditionally
v3: expand block-comment in ddebug_add_module

v2: move RvB after SoB

finish hoist - drop old fn - ddebug_attach_module_classes

the v1 rev left the old ddebug_attach_module_classes in place, but it
is completely redundant now, since it already lost the list-linking
job it was doing.

It was being cut out later in the patchset (in the unsent API
adaptation phase), but for cleaner review, lets excise it now.

OLD all-in-1-series (pre split into reviewable chunks)

v10?- reordered params to match kdoc

v12- refactor/rename: s/dd_mark_vector_subrange/dd_set_module_subrange/

1. Renamed the macro from dd_mark_vector_subrange to
   dd_set_module_subrange to better reflect its purpose of narrowing a
   vector to a module-specific subrange.

2. Simplified the arguments by removing the redundant _dst, as the _di
   pointer already provides access to the target _ddebug_info struct.

3. Refactored for Clarity: Instead of overwriting the struct's start
   pointer while the for_subvec loop is using it to iterate, I
   introduced a temporary __start variable. This avoids the "subtle"
   side effect and makes the logic easier to follow.

4. Updated Documentation: Improved the comment block to explicitly
   state that the macro scans for the first match and counts
   contiguous elements.

fiuxp
---
 lib/dynamic_debug.c | 79 +++++++++++++++++++++++++++++------------------------
 1 file changed, 43 insertions(+), 36 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 1627e40efc8f..18289ca7170b 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1174,33 +1174,34 @@ static const struct proc_ops proc_fops = {
 	.proc_write = ddebug_proc_write
 };
 
-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_subvec(i, cm, di, maps) {
-		if (!strcmp(cm->mod_name, dt->info.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->info.maps.start = cm;
-			}
-			nc++;
-		} else if (nc) {
-			/* end of matching classmaps */
-			break;
-		}
-	}
-	dt->info.maps.len = nc;
-	if (nc)
-		vpr_info("module:%s attached %d classes\n", dt->info.mod_name, nc);
-}
+/*
+ * dd_set_module_subrange - find matching subrange of classmaps
+ * @_i:   caller-provided index var
+ * @_sp:  cursor into @_vec
+ * @_di:  pointer to the struct _ddebug_info to be narrowed
+ * @_vec: name of the vector member (must have .start and .len)
+ *
+ * Narrow a _ddebug_info's vector (@_vec) of classmaps to the
+ * contiguous subrange of elements where ->mod_name matches
+ * @__di->mod_name.  This is primarily for builtins, loadable modules
+ * have only their classmaps, and dont need this sub-selection.
+ */
+#define dd_set_module_subrange(_i, _sp, _di, _vec) ({			\
+	struct _ddebug_info *__di = (_di);				\
+	typeof(__di->_vec.start) __start = NULL;			\
+	int __nc = 0;							\
+	for_subvec(_i, _sp, __di, _vec) {				\
+		if (!strcmp((_sp)->mod_name, __di->mod_name)) {		\
+			if (!__nc++)					\
+				__start = (_sp);			\
+		} else if (__nc) {					\
+			break; /* end of consecutive matches */		\
+		}							\
+	}								\
+	__di->_vec.len = __nc;						\
+	if (__nc)							\
+		__di->_vec.start = __start;				\
+})
 
 /*
  * Allocate a new ddebug_table for the given module
@@ -1209,6 +1210,8 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug
 static int ddebug_add_module(struct _ddebug_info *di)
 {
 	struct ddebug_table *dt;
+	struct ddebug_class_map *cm;
+	int i;
 
 	if (!di->descs.len)
 		return 0;
@@ -1221,17 +1224,21 @@ static int ddebug_add_module(struct _ddebug_info *di)
 		return -ENOMEM;
 	}
 	/*
-	 * For built-in modules, name (as supplied in di by its
-	 * callers) lives in .rodata and is immortal. For loaded
-	 * modules, name points at the name[] member of struct module,
-	 * which lives at least as long as this struct ddebug_table.
+	 * For built-in modules, di is a partial cursor into the
+	 * builtin dyndbg data; the descriptors are the subrange
+	 * matching the modname, but the classmaps are the full set.
+	 * We find and set the relevant subrange of classmaps here.
+	 *
+	 * The modname string is in .rodata, the descriptors and
+	 * classmaps are in writable .data. All are immortal.
+	 *
+	 * For loaded modules, mod_name points at the name[] member
+	 * of struct module, and the descriptors and classmaps point
+	 * at the module's ELF sections; all have lifetimes matching
+	 * the module's presence.
 	 */
 	dt->info = *di;
-
-	INIT_LIST_HEAD(&dt->link);
-
-	if (di->maps.len)
-		ddebug_attach_module_classes(dt, di);
+	dd_set_module_subrange(i, cm, &dt->info, maps);
 
 	mutex_lock(&ddebug_lock);
 	list_add_tail(&dt->link, &ddebug_tables);

-- 
2.56.0