[PATCH 3/5] codetag: Introduce codetag_early_walk()

[Kees Cook <kees@kernel.org>]

In order to process builtin alloc_tags much earlier during boot (before
register_codetag() is processed), provide codetag_early_walk() that
perform a lockless walk with a specified callback function. This will be
used to allocate required caches that cannot be allocated on demand.

Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: linux-mm@kvack.org
---
 include/linux/codetag.h |  2 ++
 lib/codetag.c           | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/codetag.h b/include/linux/codetag.h
index c2a579ccd455..9eb1fcd90570 100644
--- a/include/linux/codetag.h
+++ b/include/linux/codetag.h
@@ -64,6 +64,8 @@ void codetag_lock_module_list(struct codetag_type *cttype, bool lock);
 bool codetag_trylock_module_list(struct codetag_type *cttype);
 struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype);
 struct codetag *codetag_next_ct(struct codetag_iterator *iter);
+void codetag_early_walk(const struct codetag_type_desc *desc,
+			void (*callback)(struct codetag *ct));
 
 void codetag_to_text(struct seq_buf *out, struct codetag *ct);
 
diff --git a/lib/codetag.c b/lib/codetag.c
index ef7634c7ee18..9d563c8c088a 100644
--- a/lib/codetag.c
+++ b/lib/codetag.c
@@ -154,6 +154,22 @@ static struct codetag_range get_section_range(struct module *mod,
 	};
 }
 
+void codetag_early_walk(const struct codetag_type_desc *desc,
+			void (*callback)(struct codetag *ct))
+{
+	struct codetag_range range;
+	struct codetag *ct;
+
+	range = get_section_range(NULL, desc->section);
+	if (!range.start || !range.stop ||
+	    range.start == range.stop ||
+	    range.start > range.stop)
+		return;
+
+	for (ct = range.start; ct < range.stop; ct = ((void *)ct + desc->tag_size))
+		callback(ct);
+}
+
 static int codetag_module_init(struct codetag_type *cttype, struct module *mod)
 {
 	struct codetag_range range;
-- 
2.34.1