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Date: Wed, 22 Mar 2017 13:49:17 -0700
From: "H. Peter Anvin" <>
To: Thomas Garnier <>
Cc: Andy Lutomirski <>, Ingo Molnar <>,
        Martin Schwidefsky <>,
        Heiko Carstens <>,
        David Howells <>, Arnd Bergmann <>,
        Al Viro <>, Dave Hansen <>,
        René Nyffenegger <>,
        Andrew Morton <>,
        Kees Cook
        "Paul E . McKenney" <>,
        Andy Lutomirski <>,
        Ard Biesheuvel
        Nicolas Pitre <>,
        Petr Mladek <>,
        Sebastian Andrzej Siewior <>,
        Sergey Senozhatsky <>,
        Helge Deller <>, Rik van Riel <>,
        John Stultz <>,
        Thomas Gleixner <>, Oleg Nesterov <>,
        Stephen Smalley <>,
        Pavel Tikhomirov <>,
        Frederic Weisbecker <>,
        Stanislav Kinsburskiy <>,
        Ingo Molnar <>, Paolo Bonzini <>,
        Dmitry Safonov <>,
        Borislav Petkov <>, Josh Poimboeuf <>,
        Brian Gerst <>, Jan Beulich <>,
        Christian Borntraeger <>,
        Fenghua Yu <>, He Chen <>,
        Russell King <>,
        Vladimir Murzin <>,
        Will Deacon
        Catalin Marinas <>,
        Mark Rutland <>, James Morse <>,
        "David A . Long" <>,
        Pratyush Anand <>, Laura Abbott <>,
        Andre Przywara <>,
        Chris Metcalf <>,
        linux-s390 <>,
        Linux API <>,
        the arch/x86 maintainers <>,
        Kernel Hardening <>
Subject: Re: [PATCH v3 2/4] x86/syscalls: Specific usage of

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
>> 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.


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