linux-kernel - Re: [PATCH 1/2 v3] x86: introduce int3-based instruction patching

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Message-ID: <20130711210452.GE8900@pd.tnic>
Date:	Thu, 11 Jul 2013 23:04:52 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jason Baron <jbaron@...mai.com>, Joe Perches <joe@...ches.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2 v3] x86: introduce int3-based instruction patching

On Thu, Jul 11, 2013 at 01:53:16PM -0700, H. Peter Anvin wrote:
> Has anyone talked to AMD or VIA about this at all?

I guess I can try to take care of the AMD part. Just to confirm, is this
the exact sequence we're interested in:

1. Setup int3 handler for fixup.

2. Put a breakpoint (int3) on the first byte of modifying region, and
synchronize code on all CPUs.

3. Modify other bytes of modifying region.

4. Modify the first byte of modifying region, and synchronize code on
all CPUs.

5. Clear int3 handler.

If a suitable int3 handler is left permanently in place then the
synchronization in step 4 is unnecessary.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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