[PATCH v2] kasan: add kasan mode messages when kasan init

[PATCH v2] kasan: add kasan mode messages when kasan init

[Kuan-Ying Lee]

There are multiple kasan modes. It makes sense that we add some messages
to know which kasan mode is when booting up. see [1].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=212195 [1]
Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
---
change since v2:
 - Rebase to linux-next
 - HW-tags based mode need to consider asymm mode
 - Thanks for Marco's suggestion

 arch/arm64/mm/kasan_init.c |  2 +-
 mm/kasan/hw_tags.c         |  4 +++-
 mm/kasan/kasan.h           | 10 ++++++++++
 mm/kasan/sw_tags.c         |  2 +-
 4 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 5b996ca4d996..6f5a6fe8edd7 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -309,7 +309,7 @@ void __init kasan_init(void)
 	kasan_init_depth();
 #if defined(CONFIG_KASAN_GENERIC)
 	/* CONFIG_KASAN_SW_TAGS also requires kasan_init_sw_tags(). */
-	pr_info("KernelAddressSanitizer initialized\n");
+	pr_info("KernelAddressSanitizer initialized (generic)\n");
 #endif
 }
 
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index dc892119e88f..1d5c89c7cdfe 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -177,7 +177,9 @@ void __init kasan_init_hw_tags(void)
 		break;
 	}
 
-	pr_info("KernelAddressSanitizer initialized\n");
+	pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, stacktrace=%s)\n",
+		kasan_mode_info(),
+		kasan_stack_collection_enabled() ? "on" : "off");
 }
 
 void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags)
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index aebd8df86a1f..387ed7b6de37 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -36,6 +36,16 @@ static inline bool kasan_sync_fault_possible(void)
 {
 	return kasan_mode == KASAN_MODE_SYNC || kasan_mode == KASAN_MODE_ASYMM;
 }
+
+static inline const char *kasan_mode_info(void)
+{
+	if (kasan_mode == KASAN_MODE_ASYNC)
+		return "async";
+	else if (kasan_mode == KASAN_MODE_ASYMM)
+		return "asymm";
+	else
+		return "sync";
+}
 #else
 
 static inline bool kasan_stack_collection_enabled(void)
diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c
index bd3f540feb47..77f13f391b57 100644
--- a/mm/kasan/sw_tags.c
+++ b/mm/kasan/sw_tags.c
@@ -42,7 +42,7 @@ void __init kasan_init_sw_tags(void)
 	for_each_possible_cpu(cpu)
 		per_cpu(prng_state, cpu) = (u32)get_cycles();
 
-	pr_info("KernelAddressSanitizer initialized\n");
+	pr_info("KernelAddressSanitizer initialized (sw-tags)\n");
 }
 
 /*
-- 
2.18.0

Re: [PATCH v2] kasan: add kasan mode messages when kasan init

[Marco Elver]

On Wed, 20 Oct 2021 at 08:13, Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:
>
> There are multiple kasan modes. It makes sense that we add some messages
> to know which kasan mode is when booting up. see [1].
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=212195 [1]
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
> ---
> change since v2:
>  - Rebase to linux-next
>  - HW-tags based mode need to consider asymm mode
>  - Thanks for Marco's suggestion
>
>  arch/arm64/mm/kasan_init.c |  2 +-
>  mm/kasan/hw_tags.c         |  4 +++-
>  mm/kasan/kasan.h           | 10 ++++++++++
>  mm/kasan/sw_tags.c         |  2 +-
>  4 files changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 5b996ca4d996..6f5a6fe8edd7 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -309,7 +309,7 @@ void __init kasan_init(void)
>         kasan_init_depth();
>  #if defined(CONFIG_KASAN_GENERIC)
>         /* CONFIG_KASAN_SW_TAGS also requires kasan_init_sw_tags(). */
> -       pr_info("KernelAddressSanitizer initialized\n");
> +       pr_info("KernelAddressSanitizer initialized (generic)\n");
>  #endif
>  }
>
> diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
> index dc892119e88f..1d5c89c7cdfe 100644
> --- a/mm/kasan/hw_tags.c
> +++ b/mm/kasan/hw_tags.c
> @@ -177,7 +177,9 @@ void __init kasan_init_hw_tags(void)
>                 break;
>         }
>
> -       pr_info("KernelAddressSanitizer initialized\n");
> +       pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, stacktrace=%s)\n",
> +               kasan_mode_info(),
> +               kasan_stack_collection_enabled() ? "on" : "off");
>  }
>
>  void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags)
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index aebd8df86a1f..387ed7b6de37 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -36,6 +36,16 @@ static inline bool kasan_sync_fault_possible(void)
>  {
>         return kasan_mode == KASAN_MODE_SYNC || kasan_mode == KASAN_MODE_ASYMM;
>  }
> +
> +static inline const char *kasan_mode_info(void)
> +{
> +       if (kasan_mode == KASAN_MODE_ASYNC)
> +               return "async";
> +       else if (kasan_mode == KASAN_MODE_ASYMM)
> +               return "asymm";
> +       else
> +               return "sync";
> +}

This creates an inconsistency, because for
kasan_stack_collection_enabled(), kasan_async_fault_possible(), and
kasan_sync_fault_possible() there are !KASAN_HW_TAGS stubs.

A stub for kasan_mode_info() if !KASAN_HW_TAGS appears useless though,
and I wouldn't know what its return value should be.

Do you expect this helper to be used outside hw_tags.c? If not,
perhaps just move it into hw_tags.c.

Thanks,
-- Marco

Re: [PATCH v2] kasan: add kasan mode messages when kasan init

[Kuan-Ying Lee]

On Wed, 2021-10-20 at 15:23 +0800, Marco Elver wrote:
> On Wed, 20 Oct 2021 at 08:13, Kuan-Ying Lee <
> Kuan-Ying.Lee@mediatek.com> wrote:
> > 
> > There are multiple kasan modes. It makes sense that we add some
> > messages
> > to know which kasan mode is when booting up. see [1].
> > 
> > Link: 
> > https://urldefense.com/v3/__https://bugzilla.kernel.org/show_bug.cgi?id=212195__;!!CTRNKA9wMg0ARbw!yylpqk8mnd0N8w6pn4Mn4sIeu-GGlKXcA4I4yXlmstFsuqmpkhaM2V_uu2c6oPMFpZRqoQ$
> > $  [1]
> > Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
> > ---
> > change since v2:
> >  - Rebase to linux-next
> >  - HW-tags based mode need to consider asymm mode
> >  - Thanks for Marco's suggestion
> > 
> >  arch/arm64/mm/kasan_init.c |  2 +-
> >  mm/kasan/hw_tags.c         |  4 +++-
> >  mm/kasan/kasan.h           | 10 ++++++++++
> >  mm/kasan/sw_tags.c         |  2 +-
> >  4 files changed, 15 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm64/mm/kasan_init.c
> > b/arch/arm64/mm/kasan_init.c
> > index 5b996ca4d996..6f5a6fe8edd7 100644
> > --- a/arch/arm64/mm/kasan_init.c
> > +++ b/arch/arm64/mm/kasan_init.c
> > @@ -309,7 +309,7 @@ void __init kasan_init(void)
> >         kasan_init_depth();
> >  #if defined(CONFIG_KASAN_GENERIC)
> >         /* CONFIG_KASAN_SW_TAGS also requires kasan_init_sw_tags().
> > */
> > -       pr_info("KernelAddressSanitizer initialized\n");
> > +       pr_info("KernelAddressSanitizer initialized (generic)\n");
> >  #endif
> >  }
> > 
> > diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
> > index dc892119e88f..1d5c89c7cdfe 100644
> > --- a/mm/kasan/hw_tags.c
> > +++ b/mm/kasan/hw_tags.c
> > @@ -177,7 +177,9 @@ void __init kasan_init_hw_tags(void)
> >                 break;
> >         }
> > 
> > -       pr_info("KernelAddressSanitizer initialized\n");
> > +       pr_info("KernelAddressSanitizer initialized (hw-tags,
> > mode=%s, stacktrace=%s)\n",
> > +               kasan_mode_info(),
> > +               kasan_stack_collection_enabled() ? "on" : "off");
> >  }
> > 
> >  void kasan_alloc_pages(struct page *page, unsigned int order,
> > gfp_t flags)
> > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> > index aebd8df86a1f..387ed7b6de37 100644
> > --- a/mm/kasan/kasan.h
> > +++ b/mm/kasan/kasan.h
> > @@ -36,6 +36,16 @@ static inline bool
> > kasan_sync_fault_possible(void)
> >  {
> >         return kasan_mode == KASAN_MODE_SYNC || kasan_mode ==
> > KASAN_MODE_ASYMM;
> >  }
> > +
> > +static inline const char *kasan_mode_info(void)
> > +{
> > +       if (kasan_mode == KASAN_MODE_ASYNC)
> > +               return "async";
> > +       else if (kasan_mode == KASAN_MODE_ASYMM)
> > +               return "asymm";
> > +       else
> > +               return "sync";
> > +}
> 
> This creates an inconsistency, because for
> kasan_stack_collection_enabled(), kasan_async_fault_possible(), and
> kasan_sync_fault_possible() there are !KASAN_HW_TAGS stubs.
> 
> A stub for kasan_mode_info() if !KASAN_HW_TAGS appears useless
> though,
> and I wouldn't know what its return value should be.
> 
> Do you expect this helper to be used outside hw_tags.c? If not,
> perhaps just move it into hw_tags.c.

The helper will be used only in hw_tags.c.
I will move it into hw_tags.c in v3.

Thanks.

> 
> Thanks,
> -- Marco