From: Dave Hansen <dave@sr71.net>
To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com,
x86@kernel.org, a.p.zijlstra@chello.nl, paulus@samba.org,
acme@kernel.org, jkenisto@us.ibm.com, srikar@linux.vnet.ibm.com,
tglx@linutronix.de, ananth@in.ibm.com,
anil.s.keshavamurthy@intel.com, davem@davemloft.net
Subject: Re: [PATCH] x86: remove arbitrary instruction size limit in instruction decoder
Date: Mon, 17 Nov 2014 12:49:46 -0800 [thread overview]
Message-ID: <546A5F6A.7070704@sr71.net> (raw)
In-Reply-To: <5464C4FD.60705@hitachi.com>
On 11/13/2014 06:49 AM, Masami Hiramatsu wrote:
> (2014/11/13 7:53), Dave Hansen wrote:
>> The kprobes code probably needs to be looked at here a bit more
>> carefully. This patch still respects the MAX_INSN_SIZE limit
>> there but the kprobes code does look like it might be able to
>> be a bit more strict than it currently is.
>
> Would you mean kprobes can copy shorter? Maybe, but I think current
> one is enough because it is on a cold path.
> OK, at least this looks good to me.
As it stands now, if you happened to be decoding an instruction which is
short and it was *JUST* before a memory hole, I think it could oops the
kernel.
This doesn't look like it is very common (or maybe even possible) in
practice.
>> Note: the v10 version of the MPX patches I just posted depends
>> on this patch.
>
> BTW, current insn decoder doesn't support MPX... That should be
> updated (add bnd* to x86-insn-map.txt)
I think they're in there already:
> grep -i bnd arch/x86/lib/x86-opcode-map.txt
1a: BNDCL Ev,Gv | BNDCU Ev,Gv | BNDMOV Gv,Ev | BNDLDX Gv,Ev,Gv
1b: BNDCN Ev,Gv | BNDMOV Ev,Gv | BNDMK Gv,Ev | BNDSTX Ev,GV,Gv
Or were there others you were thinking of?
next prev parent reply other threads:[~2014-11-17 20:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-12 22:53 [PATCH] x86: remove arbitrary instruction size limit in instruction decoder Dave Hansen
2014-11-13 1:43 ` Peter Zijlstra
2014-11-13 14:49 ` Masami Hiramatsu
2014-11-17 20:49 ` Dave Hansen [this message]
2014-11-17 22:16 ` Masami Hiramatsu
2014-11-14 0:20 ` Jim Keniston
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