Calls to __asan_before_dynamic_init() and __asan_after_dynamic_init()
are inserted by Clang when building with coverage guards.
These functions can be used to detect initialization order fiasco bugs
in the userspace, but it is fine for them to be no-ops in the kernel.

Signed-off-by: Alexander Potapenko <glider@google.com>
---
 mm/kasan/generic.c | 18 ++++++++++++++++++
 mm/kasan/kasan.h   |  2 ++
 2 files changed, 20 insertions(+)

diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index d54e89f8c3e76..91067bb63666e 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -238,6 +238,24 @@ void __asan_unregister_globals(void *ptr, ssize_t size)
 }
 EXPORT_SYMBOL(__asan_unregister_globals);
 
+#if defined(CONFIG_KCOV_ENABLE_GUARDS)
+/*
+ * __asan_before_dynamic_init() and __asan_after_dynamic_init() are inserted
+ * when the user requests building with coverage guards. In the userspace, these
+ * two functions can be used to detect initialization order fiasco bugs, but in
+ * the kernel they can be no-ops.
+ */
+void __asan_before_dynamic_init(const char *module_name)
+{
+}
+EXPORT_SYMBOL(__asan_before_dynamic_init);
+
+void __asan_after_dynamic_init(void)
+{
+}
+EXPORT_SYMBOL(__asan_after_dynamic_init);
+#endif
+
 #define DEFINE_ASAN_LOAD_STORE(size)					\
 	void __asan_load##size(void *addr)				\
 	{								\
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 129178be5e649..c817c46b4fcd2 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -582,6 +582,8 @@ void kasan_restore_multi_shot(bool enabled);
 
 void __asan_register_globals(void *globals, ssize_t size);
 void __asan_unregister_globals(void *globals, ssize_t size);
+void __asan_before_dynamic_init(const char *module_name);
+void __asan_after_dynamic_init(void);
 void __asan_handle_no_return(void);
 void __asan_alloca_poison(void *, ssize_t size);
 void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom);
-- 
2.49.0.604.gff1f9ca942-goog

On Wed, 16 Apr 2025 at 10:55, Alexander Potapenko <glider@google.com> wrote:
>
> Calls to __asan_before_dynamic_init() and __asan_after_dynamic_init()
> are inserted by Clang when building with coverage guards.
> These functions can be used to detect initialization order fiasco bugs
> in the userspace, but it is fine for them to be no-ops in the kernel.
>
> Signed-off-by: Alexander Potapenko <glider@google.com>

This patch should be before the one adding coverage guard
instrumentation, otherwise KASAN builds will be broken intermittently,
which would break bisection.

> ---
>  mm/kasan/generic.c | 18 ++++++++++++++++++
>  mm/kasan/kasan.h   |  2 ++
>  2 files changed, 20 insertions(+)
>
> diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
> index d54e89f8c3e76..91067bb63666e 100644
> --- a/mm/kasan/generic.c
> +++ b/mm/kasan/generic.c
> @@ -238,6 +238,24 @@ void __asan_unregister_globals(void *ptr, ssize_t size)
>  }
>  EXPORT_SYMBOL(__asan_unregister_globals);
>
> +#if defined(CONFIG_KCOV_ENABLE_GUARDS)
> +/*
> + * __asan_before_dynamic_init() and __asan_after_dynamic_init() are inserted
> + * when the user requests building with coverage guards. In the userspace, these
> + * two functions can be used to detect initialization order fiasco bugs, but in
> + * the kernel they can be no-ops.
> + */
> +void __asan_before_dynamic_init(const char *module_name)
> +{
> +}
> +EXPORT_SYMBOL(__asan_before_dynamic_init);
> +
> +void __asan_after_dynamic_init(void)
> +{
> +}
> +EXPORT_SYMBOL(__asan_after_dynamic_init);
> +#endif
> +
>  #define DEFINE_ASAN_LOAD_STORE(size)                                   \
>         void __asan_load##size(void *addr)                              \
>         {                                                               \
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 129178be5e649..c817c46b4fcd2 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -582,6 +582,8 @@ void kasan_restore_multi_shot(bool enabled);
>
>  void __asan_register_globals(void *globals, ssize_t size);
>  void __asan_unregister_globals(void *globals, ssize_t size);
> +void __asan_before_dynamic_init(const char *module_name);
> +void __asan_after_dynamic_init(void);
>  void __asan_handle_no_return(void);
>  void __asan_alloca_poison(void *, ssize_t size);
>  void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom);
> --
> 2.49.0.604.gff1f9ca942-goog
>

On Tue, Apr 22, 2025 at 8:47 AM Marco Elver <elver@google.com> wrote:
>
> On Wed, 16 Apr 2025 at 10:55, Alexander Potapenko <glider@google.com> wrote:
> >
> > Calls to __asan_before_dynamic_init() and __asan_after_dynamic_init()
> > are inserted by Clang when building with coverage guards.
> > These functions can be used to detect initialization order fiasco bugs
> > in the userspace, but it is fine for them to be no-ops in the kernel.
> >
> > Signed-off-by: Alexander Potapenko <glider@google.com>
>
> This patch should be before the one adding coverage guard
> instrumentation, otherwise KASAN builds will be broken intermittently,
> which would break bisection.

Right, I'm gonna move it in v2. Thanks!