On Mon, Jun 30, 2025 at 02:31:00PM +0200, Alexander Gordeev wrote:

On Thu, Jun 26, 2025 at 08:31:37PM +0500, Sabyrzhan Tasbolatov wrote:

Hi Sabyrzhan,

quoted

diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index d54e89f8c3e..32c432df24a 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c

@@ -36,6 +36,17 @@
 #include "kasan.h"
 #include "../slab.h"
 
+/*
+ * Initialize Generic KASAN and enable runtime checks.
+ * This should be called from arch kasan_init() once shadow memory is ready.
+ */
+void __init kasan_init_generic(void)
+{
+	static_branch_enable(&kasan_flag_enabled);

s390 crashes at this line, when the whole series is applied.

FWIW, it looks like kasan is called while its state is not yet finalized.
E.g. whether calling __asan_report_store4_noabort() before kasan_init_generic()
is expected?

It crashes because with this conversion a call to static_branch_enable() is
introduced. This one get's called way before jump_label_init() init has been
called. Therefore the STATIC_KEY_CHECK_USE() in static_key_enable_cpuslocked()
triggers.

This again tries to emit a warning. Due to lack of console support that early
the kernel crashes.

One possible solution would be to move the kasan init function to
arch/s390/kernel/setup.c, after jump_label_init() has been called.
If we want this, is a different question.

It seems to work, so I see no reason for not doing that.

Vasily, since you did nearly all of the KASAN work for s390, do you have any
opinion about this?