Re: [GIT PULL] x86 LTO changes for v3.15

[Linus Torvalds]

On Mon, Mar 31, 2014 at 4:03 PM, Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:
>
> However with LTO pretty much all asmlinkages have to become
> visible, as they are used by assembler code and we need to
> tell that to the compiler, otherwise it'll optimize it away.
>
> So I abused asmlinkage for this.

I see why you did it, but I suspect it's not really necessary.

As far as I can tell, *most* of our current asmlinkage use is for the
system call declarations (both compat and regular), and the actual
*definition* of those system calls should pretty much universally use
the SYSCALL_DEFINEx() and COMPAT_SYSCALL_DEFINEx() macros.

So what I would propose is:

 - don't do the __visible as part of asmlinkage, because it really is
conceptually wrong

 - add the visible to the SYSCALL_DEFINEx() macros

and after that I strongly suspect that there will be only a handful of
cases left that are called from assembly language and that aren't
system calls. Things like "printk()" and friends that are really
special. They'd need a few manual "__visible" annotations.

> If you prefer to do it explicitely  I can send
> patches (it would be a very mechanic, long and boring
> tree sweep ...).

See above: I can pretty much guarantee that you should *not* need do
any crazy automated sweeps.  Because you shouldn't need "__visible" at
the declarations in the header files, only at the definition of the
function, right? So SYSCALL_DEFINEx() really should catch all the
normal cases.

                       Linus
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