Re: [RFC][PATCH 2/4] checkpoint/restart: x86 support

From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Oren Laadan <orenl@cs.columbia.edu>,
	Arnd Bergmann <arnd@arndb.de>,
	containers@lists.linux-foundation.org,
	Theodore Tso <tytso@mit.edu>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 2/4] checkpoint/restart: x86 support
Date: Sun, 10 Aug 2008 07:55:26 -0700	[thread overview]
Message-ID: <489F015E.9080704@goop.org> (raw)
In-Reply-To: <1218242286.19082.62.camel@nimitz>

Dave Hansen wrote:
> On Fri, 2008-08-08 at 19:04 -0400, Oren Laadan wrote:
>   
>>> struct pt_regs is part of the kernel ABI, it will not change.
>>>       
>> I'm in favor about keeping the format identical between the variations of
>> each architecture. Note, however, that "struct pt_regs" won't do because it
>> may change with these variations.
>>     
>
> "Part of the kernel ABI" makes it sound to me like it won't change.
> Who's right here? :)

Struct pt_regs is not ABI, and can (and has) changed on x86.   It's not 
suitable for a checkpoint structure because it only contains the 
registers that the kernel trashes, not all usermode registers (on i386, 
it leaves out %gs, for example).  asm-x86/ptrace-abi.h does define stuff 
that's fixed in stone; it expresses it in terms of a register array, 
with constants defining what element is which register.

    J