Messages in this thread | | | Date | Thu, 5 Sep 2019 10:49:37 +0900 | From | Masami Hiramatsu <> | Subject | Re: [Xen-devel] [PATCH -tip 0/2] x86: Prohibit kprobes on XEN_EMULATE_PREFIX |
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On Wed, 4 Sep 2019 12:54:55 +0100 Andrew Cooper <andrew.cooper3@citrix.com> wrote:
> On 04/09/2019 12:45, Masami Hiramatsu wrote: > > Hi, > > > > These patches allow x86 instruction decoder to decode > > xen-cpuid which has XEN_EMULATE_PREFIX, and prohibit > > kprobes to probe on it. > > > > Josh reported that the objtool can not decode such special > > prefixed instructions, and I found that we also have to > > prohibit kprobes to probe on such instruction. > > > > This series can be applied on -tip master branch which > > has merged Josh's objtool/perf sharing common x86 insn > > decoder series. > > The paravirtualised xen-cpuid is were you'll see it most in a regular > kernel, but be aware that it is also used for testing purposes in other > circumstances, and there is an equivalent KVM prefix which is used for > KVM testing.
Good catch! I didn't notice that. Is that really same sequance or KVM uses another sequence of instructions for KVM prefix?
> > It might be better to generalise the decode support to "virtualisation > escape prefix" or something slightly more generic.
Agreed, it is easy to expand it, we can switch the prefix template. Could you tell me where I should look? I will add it.
Thank you,
> > ~Andrew
-- Masami Hiramatsu <mhiramat@kernel.org>
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