[PATCH] jump_label: constify jump_label_text_reserved and friends

[PATCH] jump_label: constify jump_label_text_reserved and friends

[Sasha Levin]

jump_label_text_reserved() doesn't modify the memory it works on, it just
checks whether there are any jump labels there.

Constify the parameters of it to prevent warnings when working with it.

Reviewed-by: Jamie Iles <jamie.iles@oracle.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
---
 include/linux/jump_label.h |  4 ++--
 kernel/jump_label.c        | 10 ++++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 0976fc4..d917a2a 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -116,7 +116,7 @@ extern void arch_jump_label_transform(struct jump_entry *entry,
 				      enum jump_label_type type);
 extern void arch_jump_label_transform_static(struct jump_entry *entry,
 					     enum jump_label_type type);
-extern int jump_label_text_reserved(void *start, void *end);
+extern int jump_label_text_reserved(const void *start, const void *end);
 extern void static_key_slow_inc(struct static_key *key);
 extern void static_key_slow_dec(struct static_key *key);
 extern void static_key_slow_dec_deferred(struct static_key_deferred *key);
@@ -174,7 +174,7 @@ static inline void static_key_slow_dec_deferred(struct static_key_deferred *key)
 	static_key_slow_dec(&key->key);
 }
 
-static inline int jump_label_text_reserved(void *start, void *end)
+static inline int jump_label_text_reserved(const void *start, const void *end)
 {
 	return 0;
 }
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 60f48fa..6dc71c6 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -120,7 +120,8 @@ void jump_label_rate_limit(struct static_key_deferred *key,
 }
 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 
-static int addr_conflict(struct jump_entry *entry, void *start, void *end)
+static int addr_conflict(struct jump_entry *entry,
+				const void *start, const void *end)
 {
 	if (entry->code <= (unsigned long)end &&
 		entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
@@ -130,7 +131,8 @@ static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 }
 
 static int __jump_label_text_reserved(struct jump_entry *iter_start,
-		struct jump_entry *iter_stop, void *start, void *end)
+		struct jump_entry *iter_stop,
+		const void *start, const void *end)
 {
 	struct jump_entry *iter;
 
@@ -222,7 +224,7 @@ struct static_key_mod {
 	struct module *mod;
 };
 
-static int __jump_label_mod_text_reserved(void *start, void *end)
+static int __jump_label_mod_text_reserved(const void *start, const void *end)
 {
 	struct module *mod;
 
@@ -419,7 +421,7 @@ early_initcall(jump_label_init_module);
  *
  * returns 1 if there is an overlap, 0 otherwise
  */
-int jump_label_text_reserved(void *start, void *end)
+int jump_label_text_reserved(const void *start, const void *end)
 {
 	int ret = __jump_label_text_reserved(__start___jump_table,
 			__stop___jump_table, start, end);
-- 
1.8.0.2

Re: [PATCH] jump_label: constify jump_label_text_reserved and friends

[Jason Baron]

On Mon, Jan 07, 2013 at 08:58:09AM -0500, Sasha Levin wrote:
> jump_label_text_reserved() doesn't modify the memory it works on, it just
> checks whether there are any jump labels there.
> 
> Constify the parameters of it to prevent warnings when working with it.
> 

I don't see any 'const' data passed to jump_label_text_reserved()? Where is the
warning coming from? New users?

Also, does this mean 'ftrace_text_reserved()' and 'alternatives_text_reserved()'
need to be updated as well?

Thanks,

-Jason


> Reviewed-by: Jamie Iles <jamie.iles@oracle.com>
> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
> ---
>  include/linux/jump_label.h |  4 ++--
>  kernel/jump_label.c        | 10 ++++++----
>  2 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
> index 0976fc4..d917a2a 100644
> --- a/include/linux/jump_label.h
> +++ b/include/linux/jump_label.h
> @@ -116,7 +116,7 @@ extern void arch_jump_label_transform(struct jump_entry *entry,
>  				      enum jump_label_type type);
>  extern void arch_jump_label_transform_static(struct jump_entry *entry,
>  					     enum jump_label_type type);
> -extern int jump_label_text_reserved(void *start, void *end);
> +extern int jump_label_text_reserved(const void *start, const void *end);
>  extern void static_key_slow_inc(struct static_key *key);
>  extern void static_key_slow_dec(struct static_key *key);
>  extern void static_key_slow_dec_deferred(struct static_key_deferred *key);
> @@ -174,7 +174,7 @@ static inline void static_key_slow_dec_deferred(struct static_key_deferred *key)
>  	static_key_slow_dec(&key->key);
>  }
>  
> -static inline int jump_label_text_reserved(void *start, void *end)
> +static inline int jump_label_text_reserved(const void *start, const void *end)
>  {
>  	return 0;
>  }
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index 60f48fa..6dc71c6 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -120,7 +120,8 @@ void jump_label_rate_limit(struct static_key_deferred *key,
>  }
>  EXPORT_SYMBOL_GPL(jump_label_rate_limit);
>  
> -static int addr_conflict(struct jump_entry *entry, void *start, void *end)
> +static int addr_conflict(struct jump_entry *entry,
> +				const void *start, const void *end)
>  {
>  	if (entry->code <= (unsigned long)end &&
>  		entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
> @@ -130,7 +131,8 @@ static int addr_conflict(struct jump_entry *entry, void *start, void *end)
>  }
>  
>  static int __jump_label_text_reserved(struct jump_entry *iter_start,
> -		struct jump_entry *iter_stop, void *start, void *end)
> +		struct jump_entry *iter_stop,
> +		const void *start, const void *end)
>  {
>  	struct jump_entry *iter;
>  
> @@ -222,7 +224,7 @@ struct static_key_mod {
>  	struct module *mod;
>  };
>  
> -static int __jump_label_mod_text_reserved(void *start, void *end)
> +static int __jump_label_mod_text_reserved(const void *start, const void *end)
>  {
>  	struct module *mod;
>  
> @@ -419,7 +421,7 @@ early_initcall(jump_label_init_module);
>   *
>   * returns 1 if there is an overlap, 0 otherwise
>   */
> -int jump_label_text_reserved(void *start, void *end)
> +int jump_label_text_reserved(const void *start, const void *end)
>  {
>  	int ret = __jump_label_text_reserved(__start___jump_table,
>  			__stop___jump_table, start, end);
> -- 
> 1.8.0.2
> 

Re: [PATCH] jump_label: constify jump_label_text_reserved and friends

[Sasha Levin]

On 01/07/2013 11:40 AM, Jason Baron wrote:
> On Mon, Jan 07, 2013 at 08:58:09AM -0500, Sasha Levin wrote:
>> jump_label_text_reserved() doesn't modify the memory it works on, it just
>> checks whether there are any jump labels there.
>>
>> Constify the parameters of it to prevent warnings when working with it.
>>
> 
> I don't see any 'const' data passed to jump_label_text_reserved()? Where is the
> warning coming from? New users?

Out of tree code.

Though once we constify jump_label_text_reserved() and some other similar helper
functions, we can constify more existing code in kprobes/jumplabels/etc as well.

Take check_kprobe_address_safe() for example, the 'struct kprobe *p' it accepts
should probably be const as well.

> Also, does this mean 'ftrace_text_reserved()' and 'alternatives_text_reserved()'
> need to be updated as well?

Jamie has raised this point in private as well. It would make sense to fix
them as well, I haven't done that here only because we haven't stumbled on this
issue with those functions.

I'd be happy to send a patch that fixes it for all of them.


Thanks,
Sasha

> Thanks,
> 
> -Jason
> 
> 
>> Reviewed-by: Jamie Iles <jamie.iles@oracle.com>
>> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
>> ---
>>  include/linux/jump_label.h |  4 ++--
>>  kernel/jump_label.c        | 10 ++++++----
>>  2 files changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
>> index 0976fc4..d917a2a 100644
>> --- a/include/linux/jump_label.h
>> +++ b/include/linux/jump_label.h
>> @@ -116,7 +116,7 @@ extern void arch_jump_label_transform(struct jump_entry *entry,
>>  				      enum jump_label_type type);
>>  extern void arch_jump_label_transform_static(struct jump_entry *entry,
>>  					     enum jump_label_type type);
>> -extern int jump_label_text_reserved(void *start, void *end);
>> +extern int jump_label_text_reserved(const void *start, const void *end);
>>  extern void static_key_slow_inc(struct static_key *key);
>>  extern void static_key_slow_dec(struct static_key *key);
>>  extern void static_key_slow_dec_deferred(struct static_key_deferred *key);
>> @@ -174,7 +174,7 @@ static inline void static_key_slow_dec_deferred(struct static_key_deferred *key)
>>  	static_key_slow_dec(&key->key);
>>  }
>>  
>> -static inline int jump_label_text_reserved(void *start, void *end)
>> +static inline int jump_label_text_reserved(const void *start, const void *end)
>>  {
>>  	return 0;
>>  }
>> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
>> index 60f48fa..6dc71c6 100644
>> --- a/kernel/jump_label.c
>> +++ b/kernel/jump_label.c
>> @@ -120,7 +120,8 @@ void jump_label_rate_limit(struct static_key_deferred *key,
>>  }
>>  EXPORT_SYMBOL_GPL(jump_label_rate_limit);
>>  
>> -static int addr_conflict(struct jump_entry *entry, void *start, void *end)
>> +static int addr_conflict(struct jump_entry *entry,
>> +				const void *start, const void *end)
>>  {
>>  	if (entry->code <= (unsigned long)end &&
>>  		entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
>> @@ -130,7 +131,8 @@ static int addr_conflict(struct jump_entry *entry, void *start, void *end)
>>  }
>>  
>>  static int __jump_label_text_reserved(struct jump_entry *iter_start,
>> -		struct jump_entry *iter_stop, void *start, void *end)
>> +		struct jump_entry *iter_stop,
>> +		const void *start, const void *end)
>>  {
>>  	struct jump_entry *iter;
>>  
>> @@ -222,7 +224,7 @@ struct static_key_mod {
>>  	struct module *mod;
>>  };
>>  
>> -static int __jump_label_mod_text_reserved(void *start, void *end)
>> +static int __jump_label_mod_text_reserved(const void *start, const void *end)
>>  {
>>  	struct module *mod;
>>  
>> @@ -419,7 +421,7 @@ early_initcall(jump_label_init_module);
>>   *
>>   * returns 1 if there is an overlap, 0 otherwise
>>   */
>> -int jump_label_text_reserved(void *start, void *end)
>> +int jump_label_text_reserved(const void *start, const void *end)
>>  {
>>  	int ret = __jump_label_text_reserved(__start___jump_table,
>>  			__stop___jump_table, start, end);
>> -- 
>> 1.8.0.2
>>

Re: [PATCH] jump_label: constify jump_label_text_reserved and friends

[Steven Rostedt]

On Mon, 2013-01-07 at 11:40 -0500, Jason Baron wrote:
> On Mon, Jan 07, 2013 at 08:58:09AM -0500, Sasha Levin wrote:
> > jump_label_text_reserved() doesn't modify the memory it works on, it just
> > checks whether there are any jump labels there.
> > 
> > Constify the parameters of it to prevent warnings when working with it.
> > 
> 
> I don't see any 'const' data passed to jump_label_text_reserved()? Where is the
> warning coming from? New users?

If the data is never going to be modified, then it's a good idea to add
const regardless of users. It's good documentation.


> 
> Also, does this mean 'ftrace_text_reserved()' and 'alternatives_text_reserved()'
> need to be updated as well?

Yes, change these too.

Thanks!

-- Steve