crypto: Enable context analysis

Enable context analysis for crypto subsystem.

This demonstrates a larger conversion to use Clang's context
analysis. The benefit is additional static checking of locking rules,
along with better documentation.

Note the use of the __acquire_ret macro how to define an API where a
function returns a pointer to an object (struct scomp_scratch) with a
lock held. Additionally, the analysis only resolves aliases where the
analysis unambiguously sees that a variable was not reassigned after
initialization, requiring minor code changes.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251219154418.3592607-36-elver@google.com

1 files changed, 3 insertions, 0 deletions

diff --git a/crypto/proc.c b/crypto/proc.c
index 82f15b967e85..5fb9fe86d023 100644
--- a/crypto/proc.c
+++ b/crypto/proc.c
@@ -19,17 +19,20 @@
 #include "internal.h"
 
 static void *c_start(struct seq_file *m, loff_t *pos)
+	__acquires_shared(&crypto_alg_sem)
 {
 	down_read(&crypto_alg_sem);
 	return seq_list_start(&crypto_alg_list, *pos);
 }
 
 static void *c_next(struct seq_file *m, void *p, loff_t *pos)
+	__must_hold_shared(&crypto_alg_sem)
 {
 	return seq_list_next(p, &crypto_alg_list, pos);
 }
 
 static void c_stop(struct seq_file *m, void *p)
+	__releases_shared(&crypto_alg_sem)
 {
 	up_read(&crypto_alg_sem);
 }