From: Masami Hiramatsu <mhiramat@kernel.org> To: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Ingo Molnar <mingo@kernel.org>, Juergen Gross <jgross@suse.com>, "Stefano Stabellini" <sstabellini@kernel.org>, Peter Zijlstra <peterz@infradead.org>, Randy Dunlap <rdunlap@infradead.org>, <x86@kernel.org>, <linux-kernel@vger.kernel.org>, Borislav Petkov <bp@alien8.de>, "Josh Poimboeuf" <jpoimboe@redhat.com>, <xen-devel@lists.xenproject.org>, "Boris Ostrovsky" <boris.ostrovsky@oracle.com> Subject: Re: [Xen-devel] [PATCH -tip 0/2] x86: Prohibit kprobes on XEN_EMULATE_PREFIX Date: Thu, 5 Sep 2019 20:32:24 +0900 [thread overview] Message-ID: <20190905203224.e41d7f3dfbf918c5031f9766@kernel.org> (raw) In-Reply-To: <1372ce73-e2d8-6144-57df-a98429587826@citrix.com> On Thu, 5 Sep 2019 08:54:17 +0100 Andrew Cooper <andrew.cooper3@citrix.com> wrote: > On 05/09/2019 02:49, Masami Hiramatsu wrote: > > 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? > > I don't know if you've spotted, but the prefix is a ud2a instruction > followed by 'xen' in ascii. > > The KVM version was added in c/s 6c86eedc206dd1f9d37a2796faa8e6f2278215d2 > Ah, OK. I see it. But it seems that another ud0/ud1 can be used by other (new) virtualization. So at this moment I will just add a sequence as a pattern of prefix. Not use a fixed ud2 + sig. Thank you, > > > >> 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. > > These are the only two I'm aware of. > > ~Andrew -- Masami Hiramatsu <mhiramat@kernel.org>
WARNING: multiple messages have this Message-ID (diff)
From: Masami Hiramatsu <mhiramat@kernel.org> To: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Juergen Gross <jgross@suse.com>, Stefano Stabellini <sstabellini@kernel.org>, Peter Zijlstra <peterz@infradead.org>, x86@kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>, Randy Dunlap <rdunlap@infradead.org>, Josh Poimboeuf <jpoimboe@redhat.com>, xen-devel@lists.xenproject.org, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Ingo Molnar <mingo@kernel.org> Subject: Re: [Xen-devel] [PATCH -tip 0/2] x86: Prohibit kprobes on XEN_EMULATE_PREFIX Date: Thu, 5 Sep 2019 20:32:24 +0900 [thread overview] Message-ID: <20190905203224.e41d7f3dfbf918c5031f9766@kernel.org> (raw) In-Reply-To: <1372ce73-e2d8-6144-57df-a98429587826@citrix.com> On Thu, 5 Sep 2019 08:54:17 +0100 Andrew Cooper <andrew.cooper3@citrix.com> wrote: > On 05/09/2019 02:49, Masami Hiramatsu wrote: > > 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? > > I don't know if you've spotted, but the prefix is a ud2a instruction > followed by 'xen' in ascii. > > The KVM version was added in c/s 6c86eedc206dd1f9d37a2796faa8e6f2278215d2 > Ah, OK. I see it. But it seems that another ud0/ud1 can be used by other (new) virtualization. So at this moment I will just add a sequence as a pattern of prefix. Not use a fixed ud2 + sig. Thank you, > > > >> 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. > > These are the only two I'm aware of. > > ~Andrew -- Masami Hiramatsu <mhiramat@kernel.org> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
next prev parent reply other threads:[~2019-09-05 11:32 UTC|newest] Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-09-04 11:45 [PATCH -tip 0/2] x86: Prohibit kprobes on XEN_EMULATE_PREFIX Masami Hiramatsu 2019-09-04 11:45 ` [Xen-devel] " Masami Hiramatsu 2019-09-04 11:45 ` [PATCH -tip 1/2] x86: xen: insn: Decode XEN_EMULATE_PREFIX correctly Masami Hiramatsu 2019-09-04 11:45 ` [Xen-devel] " Masami Hiramatsu 2019-09-04 11:46 ` [PATCH -tip 2/2] x86: kprobes: Prohibit probing on instruction which has Xen prefix Masami Hiramatsu 2019-09-04 11:46 ` [Xen-devel] " Masami Hiramatsu 2019-09-04 11:54 ` [Xen-devel] [PATCH -tip 0/2] x86: Prohibit kprobes on XEN_EMULATE_PREFIX Andrew Cooper 2019-09-04 11:54 ` Andrew Cooper 2019-09-05 1:49 ` Masami Hiramatsu 2019-09-05 1:49 ` Masami Hiramatsu 2019-09-05 7:54 ` Andrew Cooper 2019-09-05 7:54 ` Andrew Cooper 2019-09-05 8:26 ` Peter Zijlstra 2019-09-05 8:26 ` Peter Zijlstra 2019-09-05 8:53 ` Andrew Cooper 2019-09-05 8:53 ` Andrew Cooper 2019-09-05 9:26 ` Peter Zijlstra 2019-09-05 9:26 ` Peter Zijlstra 2019-09-05 9:38 ` Andrew Cooper 2019-09-05 9:38 ` Andrew Cooper 2019-09-05 12:49 ` [OT] " Masami Hiramatsu 2019-09-05 12:49 ` [Xen-devel] [OT] " Masami Hiramatsu 2019-09-05 11:32 ` Masami Hiramatsu [this message] 2019-09-05 11:32 ` [Xen-devel] " Masami Hiramatsu 2019-09-05 13:09 ` Masami Hiramatsu 2019-09-05 13:09 ` Masami Hiramatsu 2019-09-05 13:31 ` Andrew Cooper 2019-09-05 13:31 ` Andrew Cooper 2019-09-05 16:12 ` Masami Hiramatsu 2019-09-05 16:12 ` Masami Hiramatsu 2019-09-04 12:02 ` Peter Zijlstra 2019-09-04 12:02 ` [Xen-devel] " Peter Zijlstra
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