arm64: add check_wx_pages debugfs for CHECK_WX
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Message ID 20200307093926.27145-1-tranmanphong@gmail.com
State New
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Series
  • arm64: add check_wx_pages debugfs for CHECK_WX
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Commit Message

Phong Tran March 7, 2020, 9:39 a.m. UTC
follow the suggestion from
https://github.com/KSPP/linux/issues/35

Signed-off-by: Phong Tran <tranmanphong@gmail.com>
---
 arch/arm64/Kconfig.debug        |  3 ++-
 arch/arm64/include/asm/ptdump.h |  2 ++
 arch/arm64/mm/dump.c            |  1 +
 arch/arm64/mm/ptdump_debugfs.c  | 18 ++++++++++++++++++
 4 files changed, 23 insertions(+), 1 deletion(-)

Comments

Steven Price March 9, 2020, 10:32 a.m. UTC | #1
On 07/03/2020 09:39, Phong Tran wrote:
> follow the suggestion from
> https://github.com/KSPP/linux/issues/35
> 
> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> ---
>  arch/arm64/Kconfig.debug        |  3 ++-
>  arch/arm64/include/asm/ptdump.h |  2 ++
>  arch/arm64/mm/dump.c            |  1 +
>  arch/arm64/mm/ptdump_debugfs.c  | 18 ++++++++++++++++++
>  4 files changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index 1c906d932d6b..be552fa351e2 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -48,7 +48,8 @@ config DEBUG_WX
>  	  of other unfixed kernel bugs easier.
>  
>  	  There is no runtime or memory usage effect of this option
> -	  once the kernel has booted up - it's a one time check.
> +	  once the kernel has booted up - it's a one time check and
> +	  can be checked by echo "1" to "check_wx_pages" debugfs in runtime.

I would suggest it may be better spelling this out a bit more, because
at the moment it's a little confusing when the config option is "Warn on
W+X mappings at boot", but your change makes it sound like it only
happens when you do the echo. Perhaps something like:

	  There is no runtime or memory usage effect of this option
	  once the kernel has booted up - it's a one time check at
	  boot, and can also be triggered at runtime by echo "1" to
	  "check_wx_pages".

>  
>  	  If in doubt, say "Y".
>  
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> index 38187f74e089..b80d6b4fc508 100644
> --- a/arch/arm64/include/asm/ptdump.h
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -24,9 +24,11 @@ struct ptdump_info {
>  void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
>  #ifdef CONFIG_PTDUMP_DEBUGFS
>  void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
> +int ptdump_check_wx_init(void);
>  #else
>  static inline void ptdump_debugfs_register(struct ptdump_info *info,
>  					   const char *name) { }
> +static inline int ptdump_check_wx_init(void) { return 0; }
>  #endif
>  void ptdump_check_wx(void);
>  #endif /* CONFIG_PTDUMP_CORE */

This is a confusing! Why have you made it dependent on
CONFIG_PTDUMP_DEBUGFS?

Well actually I can see why - it's because you've put the new functions
in ptdump_debugfs.c which is (currently) only built when
CONFIG_PTDUMP_DBEUGFS is enabled.

So you need to either:

 a) Ensure the new code is built when CONFIG_PTDUMP_DEBUGFS isn't enabled.

 b) Update the Kconfig help text to say that the debugfs file for
triggering a runtime W+X check is only available if
CONFIG_PTDUMP_DEBUGFS is also enabled.

Other than the confusion over config symbols this looks good.

Thanks,

Steve

> diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> index 860c00ec8bd3..60c99a047763 100644
> --- a/arch/arm64/mm/dump.c
> +++ b/arch/arm64/mm/dump.c
> @@ -378,6 +378,7 @@ static int ptdump_init(void)
>  #endif
>  	ptdump_initialize();
>  	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
> +	ptdump_check_wx_init();
>  	return 0;
>  }
>  device_initcall(ptdump_init);
> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> index 1f2eae3e988b..73cddc12c3c2 100644
> --- a/arch/arm64/mm/ptdump_debugfs.c
> +++ b/arch/arm64/mm/ptdump_debugfs.c
> @@ -16,3 +16,21 @@ void ptdump_debugfs_register(struct ptdump_info *info, const char *name)
>  {
>  	debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
>  }
> +
> +static int check_wx_debugfs_set(void *data, u64 val)
> +{
> +	if (val != 1ULL)
> +		return -EINVAL;
> +
> +	ptdump_check_wx();
> +
> +	return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> +
> +int ptdump_check_wx_init(void)
> +{
> +	return debugfs_create_file("check_wx_pages", 0200, NULL,
> +				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
> +}
>
Mark Rutland March 9, 2020, 12:17 p.m. UTC | #2
On Sat, Mar 07, 2020 at 04:39:26PM +0700, Phong Tran wrote:
> follow the suggestion from
> https://github.com/KSPP/linux/issues/35

That says:

| This should be implemented for all architectures

... so surely this should be in generic code, rahter than being
arm64-specific?

Thanks,
Mark.

> 
> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> ---
>  arch/arm64/Kconfig.debug        |  3 ++-
>  arch/arm64/include/asm/ptdump.h |  2 ++
>  arch/arm64/mm/dump.c            |  1 +
>  arch/arm64/mm/ptdump_debugfs.c  | 18 ++++++++++++++++++
>  4 files changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index 1c906d932d6b..be552fa351e2 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -48,7 +48,8 @@ config DEBUG_WX
>  	  of other unfixed kernel bugs easier.
>  
>  	  There is no runtime or memory usage effect of this option
> -	  once the kernel has booted up - it's a one time check.
> +	  once the kernel has booted up - it's a one time check and
> +	  can be checked by echo "1" to "check_wx_pages" debugfs in runtime.
>  
>  	  If in doubt, say "Y".
>  
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> index 38187f74e089..b80d6b4fc508 100644
> --- a/arch/arm64/include/asm/ptdump.h
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -24,9 +24,11 @@ struct ptdump_info {
>  void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
>  #ifdef CONFIG_PTDUMP_DEBUGFS
>  void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
> +int ptdump_check_wx_init(void);
>  #else
>  static inline void ptdump_debugfs_register(struct ptdump_info *info,
>  					   const char *name) { }
> +static inline int ptdump_check_wx_init(void) { return 0; }
>  #endif
>  void ptdump_check_wx(void);
>  #endif /* CONFIG_PTDUMP_CORE */
> diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> index 860c00ec8bd3..60c99a047763 100644
> --- a/arch/arm64/mm/dump.c
> +++ b/arch/arm64/mm/dump.c
> @@ -378,6 +378,7 @@ static int ptdump_init(void)
>  #endif
>  	ptdump_initialize();
>  	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
> +	ptdump_check_wx_init();
>  	return 0;
>  }
>  device_initcall(ptdump_init);
> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> index 1f2eae3e988b..73cddc12c3c2 100644
> --- a/arch/arm64/mm/ptdump_debugfs.c
> +++ b/arch/arm64/mm/ptdump_debugfs.c
> @@ -16,3 +16,21 @@ void ptdump_debugfs_register(struct ptdump_info *info, const char *name)
>  {
>  	debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
>  }
> +
> +static int check_wx_debugfs_set(void *data, u64 val)
> +{
> +	if (val != 1ULL)
> +		return -EINVAL;
> +
> +	ptdump_check_wx();
> +
> +	return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> +
> +int ptdump_check_wx_init(void)
> +{
> +	return debugfs_create_file("check_wx_pages", 0200, NULL,
> +				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
> +}
> -- 
> 2.20.1
>
Greg KH March 9, 2020, 12:21 p.m. UTC | #3
On Mon, Mar 09, 2020 at 12:17:14PM +0000, Mark Rutland wrote:
> On Sat, Mar 07, 2020 at 04:39:26PM +0700, Phong Tran wrote:
> > follow the suggestion from
> > https://github.com/KSPP/linux/issues/35
> 
> That says:
> 
> | This should be implemented for all architectures
> 
> ... so surely this should be in generic code, rahter than being
> arm64-specific?
> 
> Thanks,
> Mark.
> 
> > 
> > Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> > ---
> >  arch/arm64/Kconfig.debug        |  3 ++-
> >  arch/arm64/include/asm/ptdump.h |  2 ++
> >  arch/arm64/mm/dump.c            |  1 +
> >  arch/arm64/mm/ptdump_debugfs.c  | 18 ++++++++++++++++++
> >  4 files changed, 23 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> > index 1c906d932d6b..be552fa351e2 100644
> > --- a/arch/arm64/Kconfig.debug
> > +++ b/arch/arm64/Kconfig.debug
> > @@ -48,7 +48,8 @@ config DEBUG_WX
> >  	  of other unfixed kernel bugs easier.
> >  
> >  	  There is no runtime or memory usage effect of this option
> > -	  once the kernel has booted up - it's a one time check.
> > +	  once the kernel has booted up - it's a one time check and
> > +	  can be checked by echo "1" to "check_wx_pages" debugfs in runtime.
> >  
> >  	  If in doubt, say "Y".
> >  
> > diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> > index 38187f74e089..b80d6b4fc508 100644
> > --- a/arch/arm64/include/asm/ptdump.h
> > +++ b/arch/arm64/include/asm/ptdump.h
> > @@ -24,9 +24,11 @@ struct ptdump_info {
> >  void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
> >  #ifdef CONFIG_PTDUMP_DEBUGFS
> >  void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
> > +int ptdump_check_wx_init(void);
> >  #else
> >  static inline void ptdump_debugfs_register(struct ptdump_info *info,
> >  					   const char *name) { }
> > +static inline int ptdump_check_wx_init(void) { return 0; }
> >  #endif
> >  void ptdump_check_wx(void);
> >  #endif /* CONFIG_PTDUMP_CORE */
> > diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> > index 860c00ec8bd3..60c99a047763 100644
> > --- a/arch/arm64/mm/dump.c
> > +++ b/arch/arm64/mm/dump.c
> > @@ -378,6 +378,7 @@ static int ptdump_init(void)
> >  #endif
> >  	ptdump_initialize();
> >  	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
> > +	ptdump_check_wx_init();
> >  	return 0;
> >  }
> >  device_initcall(ptdump_init);
> > diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> > index 1f2eae3e988b..73cddc12c3c2 100644
> > --- a/arch/arm64/mm/ptdump_debugfs.c
> > +++ b/arch/arm64/mm/ptdump_debugfs.c
> > @@ -16,3 +16,21 @@ void ptdump_debugfs_register(struct ptdump_info *info, const char *name)
> >  {
> >  	debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
> >  }
> > +
> > +static int check_wx_debugfs_set(void *data, u64 val)
> > +{
> > +	if (val != 1ULL)
> > +		return -EINVAL;
> > +
> > +	ptdump_check_wx();
> > +
> > +	return 0;
> > +}
> > +
> > +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> > +
> > +int ptdump_check_wx_init(void)
> > +{
> > +	return debugfs_create_file("check_wx_pages", 0200, NULL,
> > +				   NULL, &check_wx_fops) ? 0 : -ENOMEM;

Do not check the return value of this function, especially as it is
returning a pointer, not an int!

Just call the function and move on, you should not do anything different
if it returns an error or not.

thanks,

greg k-h
Kees Cook March 9, 2020, 4:15 p.m. UTC | #4
On Mon, Mar 09, 2020 at 12:17:14PM +0000, Mark Rutland wrote:
> On Sat, Mar 07, 2020 at 04:39:26PM +0700, Phong Tran wrote:
> > follow the suggestion from
> > https://github.com/KSPP/linux/issues/35
> 
> That says:
> 
> | This should be implemented for all architectures
> 
> ... so surely this should be in generic code, rahter than being
> arm64-specific?

Not all architectures have implemented CONFIG_DEBUG_WX...

-Kees

> 
> Thanks,
> Mark.
> 
> > 
> > Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> > ---
> >  arch/arm64/Kconfig.debug        |  3 ++-
> >  arch/arm64/include/asm/ptdump.h |  2 ++
> >  arch/arm64/mm/dump.c            |  1 +
> >  arch/arm64/mm/ptdump_debugfs.c  | 18 ++++++++++++++++++
> >  4 files changed, 23 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> > index 1c906d932d6b..be552fa351e2 100644
> > --- a/arch/arm64/Kconfig.debug
> > +++ b/arch/arm64/Kconfig.debug
> > @@ -48,7 +48,8 @@ config DEBUG_WX
> >  	  of other unfixed kernel bugs easier.
> >  
> >  	  There is no runtime or memory usage effect of this option
> > -	  once the kernel has booted up - it's a one time check.
> > +	  once the kernel has booted up - it's a one time check and
> > +	  can be checked by echo "1" to "check_wx_pages" debugfs in runtime.
> >  
> >  	  If in doubt, say "Y".
> >  
> > diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> > index 38187f74e089..b80d6b4fc508 100644
> > --- a/arch/arm64/include/asm/ptdump.h
> > +++ b/arch/arm64/include/asm/ptdump.h
> > @@ -24,9 +24,11 @@ struct ptdump_info {
> >  void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
> >  #ifdef CONFIG_PTDUMP_DEBUGFS
> >  void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
> > +int ptdump_check_wx_init(void);
> >  #else
> >  static inline void ptdump_debugfs_register(struct ptdump_info *info,
> >  					   const char *name) { }
> > +static inline int ptdump_check_wx_init(void) { return 0; }
> >  #endif
> >  void ptdump_check_wx(void);
> >  #endif /* CONFIG_PTDUMP_CORE */
> > diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> > index 860c00ec8bd3..60c99a047763 100644
> > --- a/arch/arm64/mm/dump.c
> > +++ b/arch/arm64/mm/dump.c
> > @@ -378,6 +378,7 @@ static int ptdump_init(void)
> >  #endif
> >  	ptdump_initialize();
> >  	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
> > +	ptdump_check_wx_init();
> >  	return 0;
> >  }
> >  device_initcall(ptdump_init);
> > diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> > index 1f2eae3e988b..73cddc12c3c2 100644
> > --- a/arch/arm64/mm/ptdump_debugfs.c
> > +++ b/arch/arm64/mm/ptdump_debugfs.c
> > @@ -16,3 +16,21 @@ void ptdump_debugfs_register(struct ptdump_info *info, const char *name)
> >  {
> >  	debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
> >  }
> > +
> > +static int check_wx_debugfs_set(void *data, u64 val)
> > +{
> > +	if (val != 1ULL)
> > +		return -EINVAL;
> > +
> > +	ptdump_check_wx();
> > +
> > +	return 0;
> > +}
> > +
> > +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> > +
> > +int ptdump_check_wx_init(void)
> > +{
> > +	return debugfs_create_file("check_wx_pages", 0200, NULL,
> > +				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
> > +}
> > -- 
> > 2.20.1
> >
Mark Rutland March 9, 2020, 4:51 p.m. UTC | #5
On Mon, Mar 09, 2020 at 09:15:10AM -0700, Kees Cook wrote:
> On Mon, Mar 09, 2020 at 12:17:14PM +0000, Mark Rutland wrote:
> > On Sat, Mar 07, 2020 at 04:39:26PM +0700, Phong Tran wrote:
> > > follow the suggestion from
> > > https://github.com/KSPP/linux/issues/35
> > 
> > That says:
> > 
> > | This should be implemented for all architectures
> > 
> > ... so surely this should be in generic code, rahter than being
> > arm64-specific?
> 
> Not all architectures have implemented CONFIG_DEBUG_WX...

Sure; I assumed the generic code could be gated with:

#ifdef CONFIG_DEBUG_WX
	debug_checkwx()
#endif

... or something to that effect, so that the common code could handle
all the sysfs bits and ensure that part was consistent.

Thanksm
Mark.
> 
> -Kees
> 
> > 
> > Thanks,
> > Mark.
> > 
> > > 
> > > Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> > > ---
> > >  arch/arm64/Kconfig.debug        |  3 ++-
> > >  arch/arm64/include/asm/ptdump.h |  2 ++
> > >  arch/arm64/mm/dump.c            |  1 +
> > >  arch/arm64/mm/ptdump_debugfs.c  | 18 ++++++++++++++++++
> > >  4 files changed, 23 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> > > index 1c906d932d6b..be552fa351e2 100644
> > > --- a/arch/arm64/Kconfig.debug
> > > +++ b/arch/arm64/Kconfig.debug
> > > @@ -48,7 +48,8 @@ config DEBUG_WX
> > >  	  of other unfixed kernel bugs easier.
> > >  
> > >  	  There is no runtime or memory usage effect of this option
> > > -	  once the kernel has booted up - it's a one time check.
> > > +	  once the kernel has booted up - it's a one time check and
> > > +	  can be checked by echo "1" to "check_wx_pages" debugfs in runtime.
> > >  
> > >  	  If in doubt, say "Y".
> > >  
> > > diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> > > index 38187f74e089..b80d6b4fc508 100644
> > > --- a/arch/arm64/include/asm/ptdump.h
> > > +++ b/arch/arm64/include/asm/ptdump.h
> > > @@ -24,9 +24,11 @@ struct ptdump_info {
> > >  void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
> > >  #ifdef CONFIG_PTDUMP_DEBUGFS
> > >  void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
> > > +int ptdump_check_wx_init(void);
> > >  #else
> > >  static inline void ptdump_debugfs_register(struct ptdump_info *info,
> > >  					   const char *name) { }
> > > +static inline int ptdump_check_wx_init(void) { return 0; }
> > >  #endif
> > >  void ptdump_check_wx(void);
> > >  #endif /* CONFIG_PTDUMP_CORE */
> > > diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> > > index 860c00ec8bd3..60c99a047763 100644
> > > --- a/arch/arm64/mm/dump.c
> > > +++ b/arch/arm64/mm/dump.c
> > > @@ -378,6 +378,7 @@ static int ptdump_init(void)
> > >  #endif
> > >  	ptdump_initialize();
> > >  	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
> > > +	ptdump_check_wx_init();
> > >  	return 0;
> > >  }
> > >  device_initcall(ptdump_init);
> > > diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> > > index 1f2eae3e988b..73cddc12c3c2 100644
> > > --- a/arch/arm64/mm/ptdump_debugfs.c
> > > +++ b/arch/arm64/mm/ptdump_debugfs.c
> > > @@ -16,3 +16,21 @@ void ptdump_debugfs_register(struct ptdump_info *info, const char *name)
> > >  {
> > >  	debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
> > >  }
> > > +
> > > +static int check_wx_debugfs_set(void *data, u64 val)
> > > +{
> > > +	if (val != 1ULL)
> > > +		return -EINVAL;
> > > +
> > > +	ptdump_check_wx();
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> > > +
> > > +int ptdump_check_wx_init(void)
> > > +{
> > > +	return debugfs_create_file("check_wx_pages", 0200, NULL,
> > > +				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
> > > +}
> > > -- 
> > > 2.20.1
> > > 
> 
> -- 
> Kees Cook
Will Deacon April 20, 2020, 8:42 p.m. UTC | #6
On Sat, Mar 07, 2020 at 04:39:26PM +0700, Phong Tran wrote:
> follow the suggestion from
> https://github.com/KSPP/linux/issues/35
> 
> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> ---
>  arch/arm64/Kconfig.debug        |  3 ++-
>  arch/arm64/include/asm/ptdump.h |  2 ++
>  arch/arm64/mm/dump.c            |  1 +
>  arch/arm64/mm/ptdump_debugfs.c  | 18 ++++++++++++++++++
>  4 files changed, 23 insertions(+), 1 deletion(-)

Any plans to spin an updated version of this? The review feedback all seemed
reasonable to me.

Thanks,

Will

Patch
diff mbox series

diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index 1c906d932d6b..be552fa351e2 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -48,7 +48,8 @@  config DEBUG_WX
 	  of other unfixed kernel bugs easier.
 
 	  There is no runtime or memory usage effect of this option
-	  once the kernel has booted up - it's a one time check.
+	  once the kernel has booted up - it's a one time check and
+	  can be checked by echo "1" to "check_wx_pages" debugfs in runtime.
 
 	  If in doubt, say "Y".
 
diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
index 38187f74e089..b80d6b4fc508 100644
--- a/arch/arm64/include/asm/ptdump.h
+++ b/arch/arm64/include/asm/ptdump.h
@@ -24,9 +24,11 @@  struct ptdump_info {
 void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
 #ifdef CONFIG_PTDUMP_DEBUGFS
 void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
+int ptdump_check_wx_init(void);
 #else
 static inline void ptdump_debugfs_register(struct ptdump_info *info,
 					   const char *name) { }
+static inline int ptdump_check_wx_init(void) { return 0; }
 #endif
 void ptdump_check_wx(void);
 #endif /* CONFIG_PTDUMP_CORE */
diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index 860c00ec8bd3..60c99a047763 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -378,6 +378,7 @@  static int ptdump_init(void)
 #endif
 	ptdump_initialize();
 	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
+	ptdump_check_wx_init();
 	return 0;
 }
 device_initcall(ptdump_init);
diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
index 1f2eae3e988b..73cddc12c3c2 100644
--- a/arch/arm64/mm/ptdump_debugfs.c
+++ b/arch/arm64/mm/ptdump_debugfs.c
@@ -16,3 +16,21 @@  void ptdump_debugfs_register(struct ptdump_info *info, const char *name)
 {
 	debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
 }
+
+static int check_wx_debugfs_set(void *data, u64 val)
+{
+	if (val != 1ULL)
+		return -EINVAL;
+
+	ptdump_check_wx();
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
+
+int ptdump_check_wx_init(void)
+{
+	return debugfs_create_file("check_wx_pages", 0200, NULL,
+				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
+}