linux-kernel - Re: [PATCH] x86: use enum instead of literals for trap values

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Message-ID: <20120309190842.GC13745@aftab>
Date:	Fri, 9 Mar 2012 20:08:42 +0100
From:	Borislav Petkov <bp@...64.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Andy Lutomirski <luto@....edu>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Frysinger <vapier@...too.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86: use enum instead of literals for trap values

On Fri, Mar 09, 2012 at 10:54:19AM -0800, Kees Cook wrote:
> On Fri, Mar 9, 2012 at 10:28 AM, Borislav Petkov <bp@...64.org> wrote:
> > On Fri, Mar 09, 2012 at 10:21:52AM -0800, Kees Cook wrote:
> >> > I have to admit personally to prefer something like X86_XCP_XX where XX
> >> > is the two-letter code that the Intel documentation uses for that trap,
> >> > i.e. #GP, #BR, #MC and so on.
> >>
> >> We need a single person to decide on this bike shed color. :) If the
> >> list of enum names can be agreed on, I'll be happy to do the
> >> search/replace for it.
> >
> > Well,
> >
> > here are my 2¢: I agree with hpa because
> >
> > a) it maps the CPU vendor documentation
> > b) it is nicely short
> 
> How about:
> 
> X86_XCP_DE = 0,         /* 0, Divide-by-zero */
> X86_XCP_DB,             /* 1, Debug */
> X86_XCP_NMI,            /* 2, Non-maskable Interrupt */
> X86_XCP_BP,             /* 3, Breakpoint */
> X86_XCP_OF,             /* 4, Overflow */
> X86_XCP_BR,             /* 5, Bound Range Exceeded */
> X86_XCP_UD,             /* 6, Invalid Opcode */
> X86_XCP_NM,             /* 7, Device Not Available */
> X86_XCP_DF,             /* 8, Double Fault */
> X86_XCP_OLD_MF,         /* 9, Coprocessor Segment Overrun */
> X86_XCP_TS,             /* 10, Invalid TSS */
> X86_XCP_NP,             /* 11, Segment Not Present */
> X86_XCP_SS,             /* 12, Stack-Segment Fault */
> X86_XCP_GP,             /* 13, General Protection Fault  */
> X86_XCP_PF,             /* 14, Page Fault */
> X86_XCP_RES,            /* 15, Reserved */

So is this reserved or are we using it for Spurious IRQs? If we use it,
then 'RES' is a bad name. Maybe we define our own like

X86_VEC_SP

and then do

X86_VEC_IR for IRET

in the manner we assumed for the rest?

> X86_XCP_MF,             /* 16, x87 Floating-Point Exception */
> X86_XCP_AC,             /* 17, Alignment Check */
> X86_XCP_MC,             /* 18, Machine Check */
> X86_XCP_XM,             /* 19, SIMD Floating-Point Exception */

Shouln't this be #XF actually? At least it is so in the AMD docs.

> X86_XCP_IRET = 32,      /* 32, IRET Exception */
> 
> There is a name collision for "MF", there's no mnemonic for NMI,

Well, in the AMD docs we actually do have the '#NMI' mnemonic in use.

> IRET, or the reserved "spurious" interrupt.
>
> Can use "VEC" instead "XCP", as Steven suggests.

Yeah, because those actually are fixed interrupt vectors, as they're
called in the AMD docs. Makes sense.

Thanks.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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