linux-kernel - Re: [PATCH 4/5] x86-64: Handle exception table entries during early boot

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Message-ID: <4F90445B.9050106@zytor.com>
Date:	Thu, 19 Apr 2012 09:59:07 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 4/5] x86-64: Handle exception table entries during early
 boot

On 04/19/2012 06:02 AM, Borislav Petkov wrote:>> +	# 56(%rsp) %rflags
>> +	# 48(%rsp) %cs
>> +	# 40(%rsp) %rip
>> +	# 32(%rsp) error code
> 
> Just a question about understanding this: I was strugging with the
> exact interrupt-handler stack layout, so how do you know the exact
> offsets of rflags, cs et all? I've been staring at our APM v2, p. 144
> (http://support.amd.com/us/Processor_TechDocs/24593_APM_v2.pdf) which
> shows the interrupt stack with error code but it has different offsets
> than those above:
> 
> [Return SS]	40(%rsp)
> [Return RSP]	32(%rsp)
> [rFLAGS]	24(%rsp)
> [CS]		16(%rsp)
> [RIP]		 8(%rsp)
> [ErrorCode]	 0(%rsp)
> 
> but I see below that we have room for %rax, %rcx and %rdx on the stack.
> 
> Are we doing something different in Linux, or what am I missing?

The offsets in my code refer to offsets after we push the vector number,
%rax, %rcx and %rdx onto the stack manually; that is 4*8 = 32 bytes,
hence the offset.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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