linux-kernel - Re: [PATCH 7/7] mm/kasan: define __asan_before_dynamic_init, __asan_after_dynamic

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Message-ID: <CANpmjNOZyFeX2OfPsZkB3DfcFrdSWO9m+yGwB_rN3Mc+JySqnQ@mail.gmail.com>
Date: Tue, 22 Apr 2025 08:46:59 +0200
From: Marco Elver <elver@...gle.com>
To: Alexander Potapenko <glider@...gle.com>
Cc: quic_jiangenj@...cinc.com, linux-kernel@...r.kernel.org, 
	kasan-dev@...glegroups.com, Aleksandr Nogikh <nogikh@...gle.com>, 
	Andrey Konovalov <andreyknvl@...il.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Ingo Molnar <mingo@...hat.com>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 7/7] mm/kasan: define __asan_before_dynamic_init, __asan_after_dynamic_init

On Wed, 16 Apr 2025 at 10:55, Alexander Potapenko <glider@...gle.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@...gle.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
>