# Re: \[PATCH v3 2/4\] x86/syscalls: Specific usage of verify\_pre\_usermode\_state

- From: H. Peter Anvin \<hpa@zytor.com\>
- Date: 2017-03-22 20:49:17 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2017/03/13329536
- Thread: https://ratatoskr.run/linux-api/2017/03/13329513/t.md

```text
On 03/22/17 13:41, Thomas Garnier wrote:
>>> with the change below for additional feedback.
>>
>> Can you specify what that means?
> 
> If I set inline by default, the compiler chose not to inline it on
> x86. If I force inline the size impact was actually bigger (without
> the architecture specific code).
> 

That's utterly bizarre.  Something strange is going on there.  I suspect
the right thing to do is to out-of-line the error case only, but even
that seems strange.  It should be something like four instructions inline.

>>
>> On x86, where there is only one caller of this, it really seems like it
>> ought to reduce the overhead to almost zero (since it most likely is
>> hidden in the pipeline.)
>>
>> I would like to suggest defining it inline if
>> CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE is set; I really don't
>> care about an architecture which doesn't have it.
> 
> But if there is only one caller, does the compiler is not suppose to
> inline the function based on options?

If it is marked static in the same file, yes, but you have it in a
different file from what I can tell.

> The assembly will call it too, so I would need an inline and a
> non-inline based on the caller.

Where?  I don't see that anywhere, at least for x86.

	-hpa
```