From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
arjan@linux.intel.com, bp@alien8.de,
richard.weinberger@gmail.com
Subject: Re: [PATCH] x86: Implement __WARN using UD0
Date: Thu, 23 Feb 2017 08:12:32 -0600 [thread overview]
Message-ID: <20170223141232.nr6fahyhcljravbn@treble> (raw)
In-Reply-To: <20170223132813.GB6515@twins.programming.kicks-ass.net>
On Thu, Feb 23, 2017 at 02:28:13PM +0100, Peter Zijlstra wrote:
> +/*
> + * Only UD2 is defined in the Intel SDM and AMD64 docs,
> + * but the interweb provided UD0 and UD1:
> + *
> + * https://groups.google.com/forum/#!topic/alt.os.assembly/_rS4L0fnqGE
FYI, the latest Intel SDM does have UD0 and UD1.
I guess AMD64 and hypervisors don't need to know about it, since if they
don't, it will still trigger the same invalid opcode exception anyway?
Any idea what the functional difference is between UD0 and UD2?
> + * Since some emulators terminate on UD2, we cannot use it for WARN.
That's too bad, which emulators are those?
> + * Since various instruction decoders disagree on the length of UD1,
> + * we cannot use it either. So use UD0 for WARN.
It shows up as "(bad)" in objtool and gdb, though it still gets the
length right:
8b9: 0f ff (bad)
It would be nice if the tools knew about it...
--
Josh
next prev parent reply other threads:[~2017-02-23 14:12 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-23 13:28 Peter Zijlstra
2017-02-23 14:09 ` Peter Zijlstra
2017-02-23 14:59 ` Peter Zijlstra
2017-02-23 15:09 ` hpa
2017-02-23 15:23 ` Peter Zijlstra
2017-02-23 15:32 ` hpa
2017-02-23 16:03 ` Borislav Petkov
2017-02-23 14:12 ` Josh Poimboeuf [this message]
2017-02-23 14:17 ` Borislav Petkov
2017-02-23 14:36 ` Peter Zijlstra
2017-02-23 14:14 ` Arjan van de Ven
2017-02-23 14:57 ` Peter Zijlstra
2017-02-24 7:43 ` Ingo Molnar
2017-02-24 8:31 ` Peter Zijlstra
2017-02-24 9:06 ` hpa
2017-02-24 9:11 ` hpa
2017-02-24 9:15 ` Ingo Molnar
2017-02-24 9:46 ` Borislav Petkov
2017-02-24 9:52 ` H. Peter Anvin
[not found] ` <21ac6e53-2fcd-52e9-e72d-9faf7da14d1e@zytor.com>
2017-02-24 10:41 ` Peter Zijlstra
2017-02-25 10:38 ` Borislav Petkov
2017-02-25 17:55 ` hpa
2017-02-25 19:38 ` Borislav Petkov
2017-02-25 20:04 ` hpa
2017-02-25 20:29 ` Borislav Petkov
2017-02-24 11:16 ` [PATCH -v2] " Peter Zijlstra
2017-02-25 8:19 ` [RFC][PATCH] bug: Add _ONCE logic to report_bug() Peter Zijlstra
2017-02-25 9:18 ` Ingo Molnar
2017-02-25 9:44 ` Peter Zijlstra
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