linux-kernel - Re: [PATCH v2 00/44] Meta Linux Kernel Port

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Message-ID: <20121205183923.GY4939@ZenIV.linux.org.uk>
Date:	Wed, 5 Dec 2012 18:39:23 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	James Hogan <james.hogan@...tec.com>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 00/44] Meta Linux Kernel Port

On Wed, Dec 05, 2012 at 05:11:32PM +0000, Al Viro wrote:
> On Wed, Dec 05, 2012 at 04:08:18PM +0000, James Hogan wrote:
> 
> > other work not included:
> > * switch to generic kernel_{thread,execve} (will be posted separately to
> >   aid review)
> 
> > other changes:
> ...
> > * switch to generic sys_execve
> 
> ... which should've broken your kernel_execve().

BTW, one general note: lose the magical 7th argument.  In the few syscalls
that do need pt_regs, you can bloody well use current_pt_regs() instead;
it's what, (register & constant) + constant?  Passing it as explicit
argument is saving at most two arithmetical insns on those syscalls.
Moreover, for fork/clone/vfork we really don't need it until copy_thread();
one of the changes in -next kills passing pt_regs * to do_fork() and through
all that call chain (furthermore, if you make that
	childregs->ctx.AX[0].U0 = ALIGN(usp, 8);
in copy_thread() conditional on usp != 0, you can go with generic
variants from kernel/fork.c; again, see linux-next for examples of that).
What's left?  sigreturn and sigaltstack?

Seriously, drop that struct pt_regs *; it makes things uglier, (slightly)
hurts the syscall overhead and doesn't help the few syscalls that even
look at that argument.
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