Re: [PATCH 2/3] x86:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[Ard Biesheuvel]

On 30 May 2018 at 07:58, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
> * nixiaoming <nixiaoming@xxxxxxxxxx> wrote:
>
>> mark_rodata_ro is only called by the function mark_readonly
>> when CONFIG_STRICT_KERNEL_RWX=y
>>
>> if CONFIG_STRICT_KERNEL_RWX is not set
>> a compile warning may be triggered: unused function
>>
>> Signed-off-by: nixiaoming <nixiaoming@xxxxxxxxxx>
>> ---
>>  arch/x86/mm/init_32.c | 2 ++
>>  arch/x86/mm/init_64.c | 2 ++
>>  2 files changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
>> index c893c6a..121c567 100644
>> --- a/arch/x86/mm/init_32.c
>> +++ b/arch/x86/mm/init_32.c
>> @@ -920,6 +920,7 @@ static void mark_nxdata_nx(void)
>>       set_pages_nx(virt_to_page(start), size >> PAGE_SHIFT);
>>  }
>>
>> +#ifdef CONFIG_STRICT_KERNEL_RWX
>>  void mark_rodata_ro(void)
>>  {
>>       unsigned long start = PFN_ALIGN(_text);
>> @@ -957,3 +958,4 @@ void mark_rodata_ro(void)
>>       if (__supported_pte_mask & _PAGE_NX)
>>               debug_checkwx();
>>  }
>> +#endif /*end of CONFIG_STRICT_KERNEL_RWX*/
>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>> index 0a40060..1b7a1a7 100644
>> --- a/arch/x86/mm/init_64.c
>> +++ b/arch/x86/mm/init_64.c
>> @@ -1245,6 +1245,7 @@ void set_kernel_text_ro(void)
>>       set_memory_ro(start, (end - start) >> PAGE_SHIFT);
>>  }
>>
>> +#ifdef CONFIG_STRICT_KERNEL_RWX
>>  void mark_rodata_ro(void)
>>  {
>>       unsigned long start = PFN_ALIGN(_text);
>> @@ -1298,6 +1299,7 @@ void mark_rodata_ro(void)
>>        */
>>       pti_clone_kernel_text();
>>  }
>> +#endif
>
> NAK, this is very ugly and the changelog doesn't appear to be true: the build
> warning does not trigger in the default build, correct?
>

I don't see how the build warning could trigger at all, given that
mark_rodata_ro() has external linkage.