Now everything is ready, set kasan=off can disable kasan for all
three modes.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 include/linux/kasan-enabled.h | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
index 32f2d19f599f..b5857e15ef14 100644
--- a/include/linux/kasan-enabled.h
+++ b/include/linux/kasan-enabled.h
@@ -8,30 +8,21 @@ extern bool kasan_arg_disabled;
 
 DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
 
-#ifdef CONFIG_KASAN_HW_TAGS
-
 static __always_inline bool kasan_enabled(void)
 {
 	return static_branch_likely(&kasan_flag_enabled);
 }
 
+#ifdef CONFIG_KASAN_HW_TAGS
 static inline bool kasan_hw_tags_enabled(void)
 {
 	return kasan_enabled();
 }
-
 #else /* CONFIG_KASAN_HW_TAGS */
-
-static inline bool kasan_enabled(void)
-{
-	return IS_ENABLED(CONFIG_KASAN);
-}
-
 static inline bool kasan_hw_tags_enabled(void)
 {
 	return false;
 }
-
 #endif /* CONFIG_KASAN_HW_TAGS */
 
 #endif /* LINUX_KASAN_ENABLED_H */
-- 
2.41.0

Hello Baoqua,

On Tue,  5 Aug 2025 14:23:33 +0800 Baoquan He <bhe@redhat.com> wrote:

> Now everything is ready, set kasan=off can disable kasan for all
> three modes.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  include/linux/kasan-enabled.h | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> index 32f2d19f599f..b5857e15ef14 100644
> --- a/include/linux/kasan-enabled.h
> +++ b/include/linux/kasan-enabled.h
> @@ -8,30 +8,21 @@ extern bool kasan_arg_disabled;
>  
>  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
>  
> -#ifdef CONFIG_KASAN_HW_TAGS
> -
>  static __always_inline bool kasan_enabled(void)
>  {
>  	return static_branch_likely(&kasan_flag_enabled);
>  }

I found mm-new build fails when CONFIG_KASAN is unset as below, and 'git
bisect' points this patch.

      LD      .tmp_vmlinux1
    ld: lib/stackdepot.o:(__jump_table+0x8): undefined reference to `kasan_flag_enabled'

Since kasna_flag_enabled is defined in mm/kasan/common.c, I confirmed diff like
below fixes this.  I think it may not be a correct fix though, since I didn't
read this patchset thoroughly.

diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
index b5857e15ef14..a53d112b1020 100644
--- a/include/linux/kasan-enabled.h
+++ b/include/linux/kasan-enabled.h
@@ -8,11 +8,22 @@ extern bool kasan_arg_disabled;
 
 DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
 
+#ifdef CONFIG_KASAN
+
 static __always_inline bool kasan_enabled(void)
 {
 	return static_branch_likely(&kasan_flag_enabled);
 }
 
+#else /* CONFIG_KASAN */
+
+static inline bool kasan_enabled(void)
+{
+	return false;
+}
+
+#endif
+
 #ifdef CONFIG_KASAN_HW_TAGS
 static inline bool kasan_hw_tags_enabled(void)
 {


[...]

Thanks,
SJ

On 08/05/25 at 10:22pm, SeongJae Park wrote:
> Hello Baoqua,
> 
> On Tue,  5 Aug 2025 14:23:33 +0800 Baoquan He <bhe@redhat.com> wrote:
> 
> > Now everything is ready, set kasan=off can disable kasan for all
> > three modes.
> > 
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> >  include/linux/kasan-enabled.h | 11 +----------
> >  1 file changed, 1 insertion(+), 10 deletions(-)
> > 
> > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> > index 32f2d19f599f..b5857e15ef14 100644
> > --- a/include/linux/kasan-enabled.h
> > +++ b/include/linux/kasan-enabled.h
> > @@ -8,30 +8,21 @@ extern bool kasan_arg_disabled;
> >  
> >  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> >  
> > -#ifdef CONFIG_KASAN_HW_TAGS
> > -
> >  static __always_inline bool kasan_enabled(void)
> >  {
> >  	return static_branch_likely(&kasan_flag_enabled);
> >  }
> 
> I found mm-new build fails when CONFIG_KASAN is unset as below, and 'git
> bisect' points this patch.
> 
>       LD      .tmp_vmlinux1
>     ld: lib/stackdepot.o:(__jump_table+0x8): undefined reference to `kasan_flag_enabled'
> 
> Since kasna_flag_enabled is defined in mm/kasan/common.c, I confirmed diff like
> below fixes this.  I think it may not be a correct fix though, since I didn't
> read this patchset thoroughly.

Thanks a lot for the reporting and fix. The below code is great to fix
the error. I reproduced it and tested with below fix, it works.

Since there's other reviewing comments, I will merge this into v2 post.

> 
> diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> index b5857e15ef14..a53d112b1020 100644
> --- a/include/linux/kasan-enabled.h
> +++ b/include/linux/kasan-enabled.h
> @@ -8,11 +8,22 @@ extern bool kasan_arg_disabled;
>  
>  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
>  
> +#ifdef CONFIG_KASAN
> +
>  static __always_inline bool kasan_enabled(void)
>  {
>  	return static_branch_likely(&kasan_flag_enabled);
>  }
>  
> +#else /* CONFIG_KASAN */
> +
> +static inline bool kasan_enabled(void)
> +{
> +	return false;
> +}
> +
> +#endif
> +
>  #ifdef CONFIG_KASAN_HW_TAGS
>  static inline bool kasan_hw_tags_enabled(void)
>  {
> 
> 
> [...]
> 
> Thanks,
> SJ
>

On Tue, Aug 05, 2025 at 10:22:31PM -0700, SeongJae Park wrote:
> Hello Baoqua,
>
> On Tue,  5 Aug 2025 14:23:33 +0800 Baoquan He <bhe@redhat.com> wrote:
>
> > Now everything is ready, set kasan=off can disable kasan for all
> > three modes.
> >
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> >  include/linux/kasan-enabled.h | 11 +----------
> >  1 file changed, 1 insertion(+), 10 deletions(-)
> >
> > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> > index 32f2d19f599f..b5857e15ef14 100644
> > --- a/include/linux/kasan-enabled.h
> > +++ b/include/linux/kasan-enabled.h
> > @@ -8,30 +8,21 @@ extern bool kasan_arg_disabled;
> >
> >  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> >
> > -#ifdef CONFIG_KASAN_HW_TAGS
> > -
> >  static __always_inline bool kasan_enabled(void)
> >  {
> >  	return static_branch_likely(&kasan_flag_enabled);
> >  }
>
> I found mm-new build fails when CONFIG_KASAN is unset as below, and 'git
> bisect' points this patch.

Yup just hit this + bisected here.

>
>       LD      .tmp_vmlinux1
>     ld: lib/stackdepot.o:(__jump_table+0x8): undefined reference to `kasan_flag_enabled'
>
> Since kasna_flag_enabled is defined in mm/kasan/common.c, I confirmed diff like
> below fixes this.  I think it may not be a correct fix though, since I didn't
> read this patchset thoroughly.
>
> diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> index b5857e15ef14..a53d112b1020 100644
> --- a/include/linux/kasan-enabled.h
> +++ b/include/linux/kasan-enabled.h
> @@ -8,11 +8,22 @@ extern bool kasan_arg_disabled;
>
>  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
>
> +#ifdef CONFIG_KASAN
> +

Shouldn't we put this above the static key declaration?

Feels like the whole header should be included really.

>  static __always_inline bool kasan_enabled(void)
>  {
>  	return static_branch_likely(&kasan_flag_enabled);
>  }
>
> +#else /* CONFIG_KASAN */
> +
> +static inline bool kasan_enabled(void)
> +{
> +	return false;
> +}
> +
> +#endif
> +
>  #ifdef CONFIG_KASAN_HW_TAGS
>  static inline bool kasan_hw_tags_enabled(void)
>  {
>
>
> [...]
>
> Thanks,
> SJ
>

Cheers, Lorenzo

On 08/06/25 at 05:26pm, Lorenzo Stoakes wrote:
> On Tue, Aug 05, 2025 at 10:22:31PM -0700, SeongJae Park wrote:
> > Hello Baoqua,
> >
> > On Tue,  5 Aug 2025 14:23:33 +0800 Baoquan He <bhe@redhat.com> wrote:
> >
> > > Now everything is ready, set kasan=off can disable kasan for all
> > > three modes.
> > >
> > > Signed-off-by: Baoquan He <bhe@redhat.com>
> > > ---
> > >  include/linux/kasan-enabled.h | 11 +----------
> > >  1 file changed, 1 insertion(+), 10 deletions(-)
> > >
> > > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> > > index 32f2d19f599f..b5857e15ef14 100644
> > > --- a/include/linux/kasan-enabled.h
> > > +++ b/include/linux/kasan-enabled.h
> > > @@ -8,30 +8,21 @@ extern bool kasan_arg_disabled;
> > >
> > >  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> > >
> > > -#ifdef CONFIG_KASAN_HW_TAGS
> > > -
> > >  static __always_inline bool kasan_enabled(void)
> > >  {
> > >  	return static_branch_likely(&kasan_flag_enabled);
> > >  }
> >
> > I found mm-new build fails when CONFIG_KASAN is unset as below, and 'git
> > bisect' points this patch.
> 
> Yup just hit this + bisected here.

Sorry for the trouble and thanks for reporting.

> 
> >
> >       LD      .tmp_vmlinux1
> >     ld: lib/stackdepot.o:(__jump_table+0x8): undefined reference to `kasan_flag_enabled'
> >
> > Since kasna_flag_enabled is defined in mm/kasan/common.c, I confirmed diff like
> > below fixes this.  I think it may not be a correct fix though, since I didn't
> > read this patchset thoroughly.
> >
> > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> > index b5857e15ef14..a53d112b1020 100644
> > --- a/include/linux/kasan-enabled.h
> > +++ b/include/linux/kasan-enabled.h
> > @@ -8,11 +8,22 @@ extern bool kasan_arg_disabled;
> >
> >  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> >
> > +#ifdef CONFIG_KASAN
> > +
> 
> Shouldn't we put this above the static key declaration?
> 
> Feels like the whole header should be included really.

You are right, kasan_flag_enabled should be included in CONFIG_KASAN
ifdeffery scope.

Since CONFIG_KASAN_HW_TAGS depends on CONFIG_KASAN, we may not need
include below CONFIG_KASAN_HW_TAGS ifdeffery into CONFIG_KASAN ifdeffery
scope. Not sure if this is incorrect.

Thanks a lot for checking this.
> 
> >  static __always_inline bool kasan_enabled(void)
> >  {
> >  	return static_branch_likely(&kasan_flag_enabled);
> >  }
> >
> > +#else /* CONFIG_KASAN */
> > +
> > +static inline bool kasan_enabled(void)
> > +{
> > +	return false;
> > +}
> > +
> > +#endif
> > +
> >  #ifdef CONFIG_KASAN_HW_TAGS
> >  static inline bool kasan_hw_tags_enabled(void)
> >  {
> >
> >
> > [...]
> >
> > Thanks,
> > SJ
> >
> 
> Cheers, Lorenzo
>

On Fri, Aug 08, 2025 at 09:08:35PM +0800, Baoquan He wrote:
> On 08/06/25 at 05:26pm, Lorenzo Stoakes wrote:
> > > I found mm-new build fails when CONFIG_KASAN is unset as below, and 'git
> > > bisect' points this patch.
> >
> > Yup just hit this + bisected here.
>
> Sorry for the trouble and thanks for reporting.

No worries!

>
> >
> > >
> > >       LD      .tmp_vmlinux1
> > >     ld: lib/stackdepot.o:(__jump_table+0x8): undefined reference to `kasan_flag_enabled'
> > >
> > > Since kasna_flag_enabled is defined in mm/kasan/common.c, I confirmed diff like
> > > below fixes this.  I think it may not be a correct fix though, since I didn't
> > > read this patchset thoroughly.
> > >
> > > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> > > index b5857e15ef14..a53d112b1020 100644
> > > --- a/include/linux/kasan-enabled.h
> > > +++ b/include/linux/kasan-enabled.h
> > > @@ -8,11 +8,22 @@ extern bool kasan_arg_disabled;
> > >
> > >  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> > >
> > > +#ifdef CONFIG_KASAN
> > > +
> >
> > Shouldn't we put this above the static key declaration?
> >
> > Feels like the whole header should be included really.
>
> You are right, kasan_flag_enabled should be included in CONFIG_KASAN
> ifdeffery scope.

Firstly I _LOVE_ the term 'ifdeffery scope'. Fantastic :)

>
> Since CONFIG_KASAN_HW_TAGS depends on CONFIG_KASAN, we may not need
> include below CONFIG_KASAN_HW_TAGS ifdeffery into CONFIG_KASAN ifdeffery
> scope. Not sure if this is incorrect.

Well I don't think CONFIG_KASAN_HW_TAGS is necessarily implied right? So these
should remain I think, just nested in CONFIG_KASAN, should be fine.

>
> Thanks a lot for checking this.

No problem! Just ran in to it while doing other stuff in mm-new :)

Cheers, Lorenzo

On 08/08/25 at 02:24pm, Lorenzo Stoakes wrote:
> On Fri, Aug 08, 2025 at 09:08:35PM +0800, Baoquan He wrote:
> > On 08/06/25 at 05:26pm, Lorenzo Stoakes wrote:
......
> > > > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> > > > index b5857e15ef14..a53d112b1020 100644
> > > > --- a/include/linux/kasan-enabled.h
> > > > +++ b/include/linux/kasan-enabled.h
> > > > @@ -8,11 +8,22 @@ extern bool kasan_arg_disabled;
> > > >
> > > >  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> > > >
> > > > +#ifdef CONFIG_KASAN
> > > > +
> > >
> > > Shouldn't we put this above the static key declaration?
> > >
> > > Feels like the whole header should be included really.
> >
> > You are right, kasan_flag_enabled should be included in CONFIG_KASAN
> > ifdeffery scope.
> 
> Firstly I _LOVE_ the term 'ifdeffery scope'. Fantastic :)

Learned from upstream people with expertise on both english and kernel, :-)

> 
> >
> > Since CONFIG_KASAN_HW_TAGS depends on CONFIG_KASAN, we may not need
> > include below CONFIG_KASAN_HW_TAGS ifdeffery into CONFIG_KASAN ifdeffery
> > scope. Not sure if this is incorrect.
> 
> Well I don't think CONFIG_KASAN_HW_TAGS is necessarily implied right? So these
> should remain I think, just nested in CONFIG_KASAN, should be fine.

After investigation, I keep the CONFIG_KASAN_HW_TAGS ifdeffery scope out
of CONFIG_KASAN scope. Otherwise, I need define the dummy
kasan_hw_tags_enabled() function twice. I am personally not fan of the
style. While if that is preferred in kernel, I can change it.

#ifdef CONFIG_KASAN

#ifdef CONFIG_KASAN_HW_TAGS
......
#ifdef CONFIG_KASAN_HW_TAGS
static inline bool kasan_hw_tags_enabled(void)
{
        return kasan_enabled();
}
#else /* CONFIG_KASAN_HW_TAGS */
static inline bool kasan_hw_tags_enabled(void)
{
        return false;
}
#endif /* CONFIG_KASAN_HW_TAGS */
.....
#else /* CONFIG_KASAN */
static inline bool kasan_hw_tags_enabled(void)
{
        return false;
}
#endif

On Tue, Aug 12, 2025 at 09:27:02PM +0800, Baoquan He wrote:
> > Firstly I _LOVE_ the term 'ifdeffery scope'. Fantastic :)
>
> Learned from upstream people with expertise on both english and kernel, :-)

:)

> After investigation, I keep the CONFIG_KASAN_HW_TAGS ifdeffery scope out
> of CONFIG_KASAN scope. Otherwise, I need define the dummy
> kasan_hw_tags_enabled() function twice. I am personally not fan of the
> style. While if that is preferred in kernel, I can change it.
>
> #ifdef CONFIG_KASAN
>
> #ifdef CONFIG_KASAN_HW_TAGS
> ......
> #ifdef CONFIG_KASAN_HW_TAGS
> static inline bool kasan_hw_tags_enabled(void)
> {
>         return kasan_enabled();
> }
> #else /* CONFIG_KASAN_HW_TAGS */
> static inline bool kasan_hw_tags_enabled(void)
> {
>         return false;
> }
> #endif /* CONFIG_KASAN_HW_TAGS */
> .....
> #else /* CONFIG_KASAN */
> static inline bool kasan_hw_tags_enabled(void)
> {
>         return false;
> }
> #endif
>

This is fine, as CONFIG_KASAN_HW_TAGS implies CONFIG_KASAN anyway.

On Tue, Aug 5, 2025 at 11:34 AM Baoquan He <bhe@redhat.com> wrote:
>
> Now everything is ready, set kasan=off can disable kasan for all
> three modes.
>

Hello,

I've been working on this already and a different approach
with the Kconfig ARCH_DEFER_KASAN has been proposed.

Please see v4 thread.
https://lore.kernel.org/all/20250805142622.560992-1-snovitoll@gmail.com/

It also covers the printing in a single KASAN codebase, instead of
printing "KASAN intiilaized" in arch/* code.
Also covers the enabling KASAN via kasan_enable() for all 3 modes.

It's up to KASAN maintainers to choose either version.
I just need the confirmation now if I should proceed with v5,
or your version if it covers all arch and cases should be picked up.

Thanks

> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  include/linux/kasan-enabled.h | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
>
> diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> index 32f2d19f599f..b5857e15ef14 100644
> --- a/include/linux/kasan-enabled.h
> +++ b/include/linux/kasan-enabled.h
> @@ -8,30 +8,21 @@ extern bool kasan_arg_disabled;
>
>  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
>
> -#ifdef CONFIG_KASAN_HW_TAGS
> -
>  static __always_inline bool kasan_enabled(void)
>  {
>         return static_branch_likely(&kasan_flag_enabled);
>  }
>
> +#ifdef CONFIG_KASAN_HW_TAGS
>  static inline bool kasan_hw_tags_enabled(void)
>  {
>         return kasan_enabled();
>  }
> -
>  #else /* CONFIG_KASAN_HW_TAGS */
> -
> -static inline bool kasan_enabled(void)
> -{
> -       return IS_ENABLED(CONFIG_KASAN);
> -}
> -
>  static inline bool kasan_hw_tags_enabled(void)
>  {
>         return false;
>  }
> -
>  #endif /* CONFIG_KASAN_HW_TAGS */
>
>  #endif /* LINUX_KASAN_ENABLED_H */
> --
> 2.41.0
>
>

On 08/06/25 at 11:24pm, Sabyrzhan Tasbolatov wrote:
> On Tue, Aug 5, 2025 at 11:34 AM Baoquan He <bhe@redhat.com> wrote:
> >
> > Now everything is ready, set kasan=off can disable kasan for all
> > three modes.
> >
> 
> Hello,
> 
> I've been working on this already and a different approach
> with the Kconfig ARCH_DEFER_KASAN has been proposed.

Thanks for telling, I don't always watch MM mailing list, so missed your
earlier posting. 

I went through your v5 series, we are doing different work. I am adding
kasan=on|off to generic/sw_tags, and have added kasan_enabled() to needed
places. In fact, based on this patchset, we can remove
kasan_arch_is_ready() more easily since in all places kasan_enabled() has
been added there. Before seeing your patches, this is what I planned to
do to remove kasan_arch_is_ready(). I will see what can be done better.
Maybe I can carry your patch in v2. I will try tomorrow.

> 
> Please see v4 thread.
> https://lore.kernel.org/all/20250805142622.560992-1-snovitoll@gmail.com/
> 
> It also covers the printing in a single KASAN codebase, instead of
> printing "KASAN intiilaized" in arch/* code.
> Also covers the enabling KASAN via kasan_enable() for all 3 modes.
> 
> It's up to KASAN maintainers to choose either version.
> I just need the confirmation now if I should proceed with v5,
> or your version if it covers all arch and cases should be picked up.
> 
> Thanks
> 
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> >  include/linux/kasan-enabled.h | 11 +----------
> >  1 file changed, 1 insertion(+), 10 deletions(-)
> >
> > diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> > index 32f2d19f599f..b5857e15ef14 100644
> > --- a/include/linux/kasan-enabled.h
> > +++ b/include/linux/kasan-enabled.h
> > @@ -8,30 +8,21 @@ extern bool kasan_arg_disabled;
> >
> >  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
> >
> > -#ifdef CONFIG_KASAN_HW_TAGS
> > -
> >  static __always_inline bool kasan_enabled(void)
> >  {
> >         return static_branch_likely(&kasan_flag_enabled);
> >  }
> >
> > +#ifdef CONFIG_KASAN_HW_TAGS
> >  static inline bool kasan_hw_tags_enabled(void)
> >  {
> >         return kasan_enabled();
> >  }
> > -
> >  #else /* CONFIG_KASAN_HW_TAGS */
> > -
> > -static inline bool kasan_enabled(void)
> > -{
> > -       return IS_ENABLED(CONFIG_KASAN);
> > -}
> > -
> >  static inline bool kasan_hw_tags_enabled(void)
> >  {
> >         return false;
> >  }
> > -
> >  #endif /* CONFIG_KASAN_HW_TAGS */
> >
> >  #endif /* LINUX_KASAN_ENABLED_H */
> > --
> > 2.41.0
> >
> >
>