linux-kernel - Re: CONFIG_HAVE_ARCH

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Message-Id: <20080915203835.E2438242E5@pipsqueak.localdomain>
Date:	Mon, 15 Sep 2008 13:38:35 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Paul Mundt <lethal@...ux-sh.org>
Cc:	linux-arch@...r.kernel.org, utrace-devel@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: CONFIG_HAVE_ARCH_TRACEHOOK and you

> user_stack_pointer() is apparently a requirement, too. 

Ah, yes!  I'd forgotten about user_stack_pointer() and instruction_pointer().
Those never got properly documented either.

> Although given that you already have a task_struct pointer the only place
> you currently use it (lib/syscall.c), it makes more sense to use
> KSTK_ESP/KSTK_EIP which is provided by almost everyone already.

Almost?  It must be everyone, right?  
It's used unconditionally in fs/proc/array.c (the only use).

I hadn't noticed these before.  They aren't commented anywhere.
I've got to say, too, these are truly dismal names!

Also, I've just noticed that x86-64's user_stack_pointer() is wrong for the
case when a fast-path 64-bit syscall is in progress.  To get it right, it
needs a bit from the struct thread_info, so a call that takes task_struct
instead of (or in addition to) pt_regs is certainly right.

These are defined in asm/processor.h, as macros.  It would be better if
they could be inlines, but they really can't because asm/processor.h is
before struct task_struct is defined, etc.  I wonder if we could move these
to another header where they can be clean inlines.  I'd sure like to change
those names while we're at it.

Thoughts?

Thanks,
Roland
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