[v6,3/5] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime
diff mbox series

Message ID 20191224055545.178462-4-ruscur@russell.cc
State New
Headers show
Series
  • Implement STRICT_MODULE_RWX for powerpc
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Commit Message

Russell Currey Dec. 24, 2019, 5:55 a.m. UTC
Very rudimentary, just

	echo 1 > [debugfs]/check_wx_pages

and check the kernel log.  Useful for testing strict module RWX.

Updated the Kconfig entry to reflect this.

Also fixed a typo.

Signed-off-by: Russell Currey <ruscur@russell.cc>
---
 arch/powerpc/Kconfig.debug      |  6 ++++--
 arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++-
 2 files changed, 24 insertions(+), 3 deletions(-)

Comments

Christophe Leroy Dec. 31, 2019, 5:14 p.m. UTC | #1
Russell Currey <ruscur@russell.cc> a écrit :

> Very rudimentary, just
>
> 	echo 1 > [debugfs]/check_wx_pages
>
> and check the kernel log.  Useful for testing strict module RWX.

For testing strict module RWX you could instead implement  
module_arch_freeing_init() and call  ptdump_check_wx() from there.

Christophe

>
> Updated the Kconfig entry to reflect this.
>
> Also fixed a typo.
>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> ---
>  arch/powerpc/Kconfig.debug      |  6 ++++--
>  arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++-
>  2 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
> index 4e1d39847462..7c14c9728bc0 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -370,7 +370,7 @@ config PPC_PTDUMP
>  	  If you are unsure, say N.
>
>  config PPC_DEBUG_WX
> -	bool "Warn on W+X mappings at boot"
> +	bool "Warn on W+X mappings at boot & enable manual checks at runtime"
>  	depends on PPC_PTDUMP
>  	help
>  	  Generate a warning if any W+X mappings are found at boot.
> @@ -384,7 +384,9 @@ config PPC_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 only automatically checks once.
> +
> +	  Enables the "check_wx_pages" debugfs entry for checking at runtime.
>
>  	  If in doubt, say "Y".
>
> diff --git a/arch/powerpc/mm/ptdump/ptdump.c  
> b/arch/powerpc/mm/ptdump/ptdump.c
> index 2f9ddc29c535..b6cba29ae4a0 100644
> --- a/arch/powerpc/mm/ptdump/ptdump.c
> +++ b/arch/powerpc/mm/ptdump/ptdump.c
> @@ -4,7 +4,7 @@
>   *
>   * This traverses the kernel pagetables and dumps the
>   * information about the used sections of memory to
> - * /sys/kernel/debug/kernel_pagetables.
> + * /sys/kernel/debug/kernel_page_tables.
>   *
>   * Derived from the arm64 implementation:
>   * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
> @@ -409,6 +409,25 @@ void ptdump_check_wx(void)
>  	else
>  		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
>  }
> +
> +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");
> +
> +static int ptdump_check_wx_init(void)
> +{
> +	return debugfs_create_file("check_wx_pages", 0200, NULL,
> +				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
> +}
> +device_initcall(ptdump_check_wx_init);
>  #endif
>
>  static int ptdump_init(void)
> --
> 2.24.1
Michael Ellerman Jan. 7, 2020, 10:48 a.m. UTC | #2
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> Russell Currey <ruscur@russell.cc> a écrit :
>
>> Very rudimentary, just
>>
>> 	echo 1 > [debugfs]/check_wx_pages
>>
>> and check the kernel log.  Useful for testing strict module RWX.
>
> For testing strict module RWX you could instead implement  
> module_arch_freeing_init() and call  ptdump_check_wx() from there.

That could get expensive on large systems, not sure if we want it
enabled by default?

cheers


>> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
>> index 4e1d39847462..7c14c9728bc0 100644
>> --- a/arch/powerpc/Kconfig.debug
>> +++ b/arch/powerpc/Kconfig.debug
>> @@ -370,7 +370,7 @@ config PPC_PTDUMP
>>  	  If you are unsure, say N.
>>
>>  config PPC_DEBUG_WX
>> -	bool "Warn on W+X mappings at boot"
>> +	bool "Warn on W+X mappings at boot & enable manual checks at runtime"
>>  	depends on PPC_PTDUMP
>>  	help
>>  	  Generate a warning if any W+X mappings are found at boot.
>> @@ -384,7 +384,9 @@ config PPC_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 only automatically checks once.
>> +
>> +	  Enables the "check_wx_pages" debugfs entry for checking at runtime.
>>
>>  	  If in doubt, say "Y".
>>
>> diff --git a/arch/powerpc/mm/ptdump/ptdump.c  
>> b/arch/powerpc/mm/ptdump/ptdump.c
>> index 2f9ddc29c535..b6cba29ae4a0 100644
>> --- a/arch/powerpc/mm/ptdump/ptdump.c
>> +++ b/arch/powerpc/mm/ptdump/ptdump.c
>> @@ -4,7 +4,7 @@
>>   *
>>   * This traverses the kernel pagetables and dumps the
>>   * information about the used sections of memory to
>> - * /sys/kernel/debug/kernel_pagetables.
>> + * /sys/kernel/debug/kernel_page_tables.
>>   *
>>   * Derived from the arm64 implementation:
>>   * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
>> @@ -409,6 +409,25 @@ void ptdump_check_wx(void)
>>  	else
>>  		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
>>  }
>> +
>> +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");
>> +
>> +static int ptdump_check_wx_init(void)
>> +{
>> +	return debugfs_create_file("check_wx_pages", 0200, NULL,
>> +				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
>> +}
>> +device_initcall(ptdump_check_wx_init);
>>  #endif
>>
>>  static int ptdump_init(void)
>> --
>> 2.24.1

Patch
diff mbox series

diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 4e1d39847462..7c14c9728bc0 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -370,7 +370,7 @@  config PPC_PTDUMP
 	  If you are unsure, say N.
 
 config PPC_DEBUG_WX
-	bool "Warn on W+X mappings at boot"
+	bool "Warn on W+X mappings at boot & enable manual checks at runtime"
 	depends on PPC_PTDUMP
 	help
 	  Generate a warning if any W+X mappings are found at boot.
@@ -384,7 +384,9 @@  config PPC_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 only automatically checks once.
+
+	  Enables the "check_wx_pages" debugfs entry for checking at runtime.
 
 	  If in doubt, say "Y".
 
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index 2f9ddc29c535..b6cba29ae4a0 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -4,7 +4,7 @@ 
  *
  * This traverses the kernel pagetables and dumps the
  * information about the used sections of memory to
- * /sys/kernel/debug/kernel_pagetables.
+ * /sys/kernel/debug/kernel_page_tables.
  *
  * Derived from the arm64 implementation:
  * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
@@ -409,6 +409,25 @@  void ptdump_check_wx(void)
 	else
 		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
 }
+
+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");
+
+static int ptdump_check_wx_init(void)
+{
+	return debugfs_create_file("check_wx_pages", 0200, NULL,
+				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
+}
+device_initcall(ptdump_check_wx_init);
 #endif
 
 static int ptdump_init(void)