linux-kernel - Re: [PATCH RFC v2 07/21] kasan, arm64: move initialization message

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Date:   Wed, 28 Oct 2020 11:55:57 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Serban Constantinescu <serbanc@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 07/21] kasan, arm64: move initialization message

On Thu, Oct 22, 2020 at 3:19 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> Tag-based KASAN modes are fully initialized with kasan_init_tags(),
> while the generic mode only requireds kasan_init(). Move the
> initialization message for tag-based modes into kasan_init_tags().
>
> Also fix pr_fmt() usage for KASAN code: generic mode doesn't need it,

Why doesn't it need it? What's the difference with tag modes?

> tag-based modes should use "kasan:" instead of KBUILD_MODNAME.

With generic KASAN I currently see:

[    0.571473][    T0] kasan: KernelAddressSanitizer initialized

So KBUILD_MODNAME somehow works. Is there some difference between files?

> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Link: https://linux-review.googlesource.com/id/Idfd1e50625ffdf42dfc3dbf7455b11bd200a0a49
> ---
>  arch/arm64/mm/kasan_init.c | 3 +++
>  mm/kasan/generic.c         | 2 --
>  mm/kasan/hw_tags.c         | 4 ++++
>  mm/kasan/sw_tags.c         | 4 +++-
>  4 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index b6b9d55bb72e..8f17fa834b62 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -290,5 +290,8 @@ void __init kasan_init(void)
>  {
>         kasan_init_shadow();
>         kasan_init_depth();
> +#if defined(CONFIG_KASAN_GENERIC)
> +       /* CONFIG_KASAN_SW/HW_TAGS also requires kasan_init_tags(). */

A bit cleaner way may be to introduce kasan_init_early() and
kasan_init_late(). Late() will do tag init and always print the
message.

>         pr_info("KernelAddressSanitizer initialized\n");
> +#endif
>  }
> diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
> index de6b3f03a023..d259e4c3aefd 100644
> --- a/mm/kasan/generic.c
> +++ b/mm/kasan/generic.c
> @@ -9,8 +9,6 @@
>   *        Andrey Konovalov <andreyknvl@...il.com>
>   */
>
> -#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> -
>  #include <linux/export.h>
>  #include <linux/interrupt.h>
>  #include <linux/init.h>
> diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
> index 0128062320d5..b372421258c8 100644
> --- a/mm/kasan/hw_tags.c
> +++ b/mm/kasan/hw_tags.c
> @@ -6,6 +6,8 @@
>   * Author: Andrey Konovalov <andreyknvl@...gle.com>
>   */
>
> +#define pr_fmt(fmt) "kasan: " fmt
> +
>  #include <linux/kasan.h>
>  #include <linux/kernel.h>
>  #include <linux/memory.h>
> @@ -18,6 +20,8 @@
>  void __init kasan_init_tags(void)
>  {
>         init_tags(KASAN_TAG_MAX);
> +
> +       pr_info("KernelAddressSanitizer initialized\n");
>  }
>
>  void *kasan_reset_tag(const void *addr)
> diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c
> index bf1422282bb5..099af6dc8f7e 100644
> --- a/mm/kasan/sw_tags.c
> +++ b/mm/kasan/sw_tags.c
> @@ -6,7 +6,7 @@
>   * Author: Andrey Konovalov <andreyknvl@...gle.com>
>   */
>
> -#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +#define pr_fmt(fmt) "kasan: " fmt
>
>  #include <linux/export.h>
>  #include <linux/interrupt.h>
> @@ -41,6 +41,8 @@ void __init kasan_init_tags(void)
>
>         for_each_possible_cpu(cpu)
>                 per_cpu(prng_state, cpu) = (u32)get_cycles();
> +
> +       pr_info("KernelAddressSanitizer initialized\n");
>  }
>
>  /*
> --
> 2.29.0.rc1.297.gfa9743e501-goog
>