[PATCH v8 01/10] ARM: use _install_special_mapping for sigpage

[Nathan Lynch]

On 08/04/2014 08:12 AM, Nathan Lynch wrote:
> On 08/04/2014 07:46 AM, Will Deacon wrote:
>> On Sat, Aug 02, 2014 at 07:16:38PM +0100, Nathan Lynch wrote:
>>> _install_special_mapping allows the VMA to be identifed in
>>> /proc/pid/maps without the use of arch_vma_name, providing a
>>> slight net reduction in object size:
>>>
>>>   text    data     bss     dec     hex filename
>>>   2996      96     144    3236     ca4 arch/arm/kernel/process.o (before)
>>>   2956     104     144    3204     c84 arch/arm/kernel/process.o (after)
>>>
>>> Signed-off-by: Nathan Lynch <nathan_lynch at mentor.com>
>>> Reviewed-by: Kees Cook <keescook at chromium.org>
>>> ---
>>>  arch/arm/kernel/process.c | 24 ++++++++++++++++--------
>>>  1 file changed, 16 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
>>> index 81ef686a91ca..46fbbb3701a0 100644
>>> --- a/arch/arm/kernel/process.c
>>> +++ b/arch/arm/kernel/process.c
>>> @@ -472,19 +472,23 @@ int in_gate_area_no_mm(unsigned long addr)
>>>  
>>>  const char *arch_vma_name(struct vm_area_struct *vma)
>>>  {
>>> -	return is_gate_vma(vma) ? "[vectors]" :
>>> -		(vma->vm_mm && vma->vm_start == vma->vm_mm->context.sigpage) ?
>>> -		 "[sigpage]" : NULL;
>>> +	return is_gate_vma(vma) ? "[vectors]" : NULL;
>>>  }
>>
>> Why do you need this function? I just removed it for arm64 and I think x86
>> has done the same.
> 
> I think arch_vma_name is still needed for arm as long as the vectors
> page is not installed using _install_special_mapping.

Actually... if we give arm's gate_vma a vm_ops with a ->name() routine
that returns "[vectors]" we could get rid of arch_vma_name, I think.
This seems to be what x86_64 does.