Re: [PATCH V4 2/9] jump_label: Add the jump_label_can_update_check() helper

[Daniel Bristot de Oliveira]

On 2/7/19 3:08 PM, Borislav Petkov wrote:
> On Thu, Feb 07, 2019 at 02:21:09PM +0100, Daniel Bristot de Oliveira wrote:
>> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
>> index 288d630da22d..1e6f4d27e28d 100644
>> --- a/kernel/jump_label.c
>> +++ b/kernel/jump_label.c
>> @@ -374,22 +374,29 @@ static enum jump_label_type jump_label_type(struct 
>> jump_entry *entry)
>>      return enabled ^ branch;
>>  }
>>  
>> +static bool jump_label_can_update(struct jump_entry *entry, bool init)
>> +{
>> +    /*
>> +     * Cannot update code that was in an init text area.
>> +     */
>> +    if (!init || jump_entry_is_init(entry))
> 
> Shouldn't this be &&
> 
> ?

Oops! should be &&! sorry.

>> +            return false;
>> +
>> +    if (WARN_ONCE(!kernel_text_address(jump_entry_code(entry)),
>> +                     "can't patch jump_label at %pS", (void 
>> *)jump_entry_code(entry)))
>> +            return false;
> 
> Yeah, I think that this way of writing it is less readable than:
> 
>       if (!kernel_text_address(jump_entry_code(entry))) {
>               WARN_ONCE(1, "can't patch jump_label at %pS", (void 
> *)jump_entry_code(entry));
>               return false;
>       }

It is taking 95 characters. In this case, wouldn't be better to break?

        if (!kernel_text_address(jump_entry_code(entry))) {
                WARN_ONCE(1, "can't patch jump_label at %pS",
                          (void *)jump_entry_code(entry));
                return false;
        }

I agree your suggestion is better... just confirming that 95 is not too long...

> 
>> +            if (jump_label_can_update(entry, init)) {
>> +                    arch_jump_label_transform(entry, 
>> jump_label_type(entry));
> 
> Yap.
> 
> Thx.
> 

Thanks!

-- Daniel