From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
Linux Next Mailing List <linux-next@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: linux-next: Tree for Aug 27 (objtool)
Date: Wed, 28 Aug 2019 11:34:33 -0500 [thread overview]
Message-ID: <20190828163433.4ltoxmtuujkqspar@treble> (raw)
In-Reply-To: <20190828161331.kvikro257blxtzu5@treble>
On Wed, Aug 28, 2019 at 11:13:31AM -0500, Josh Poimboeuf wrote:
> Turns out this patch does break something:
>
> arch/x86/xen/enlighten_pv.o: warning: objtool: xen_cpuid()+0x25: can't find jump dest instruction at .text+0x9c
>
> I'll need to figure out a better way to whitelist that
> XEN_EMULATE_PREFIX fake instruction thing. I'll probably just teach
> the objtool decoder about it.
Hi Masami,
Is it possible for the kernel x86 decoder to recognize the
XEN_EMULATE_PREFIX prefix?
asm(XEN_EMULATE_PREFIX "cpuid"
: "=a" (*ax),
"=b" (*bx),
"=c" (*cx),
"=d" (*dx)
: "0" (*ax), "2" (*cx));
is disassembled to:
33: 0f 0b ud2
35: 78 65 js 9c <xen_store_tr+0xc>
37: 6e outsb %ds:(%rsi),(%dx)
38: 0f a2 cpuid
which confuses objtool. Presumably that would confuse other users of
the decoder as well.
That's a highly unlikely sequence of instructions, maybe the kernel
decoder should recognize it as a single instruction.
--
Josh
next prev parent reply other threads:[~2019-08-28 16:34 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 9:05 linux-next: Tree for Aug 27 Stephen Rothwell
2019-08-27 15:18 ` linux-next: Tree for Aug 27 (amdgpu) Randy Dunlap
2019-08-27 15:41 ` Alex Deucher
2019-08-27 15:24 ` linux-next: Tree for Aug 27 (mshyperv.c) Randy Dunlap
2019-08-27 15:29 ` linux-next: Tree for Aug 27 (kunit) Randy Dunlap
2019-08-27 16:09 ` Brendan Higgins
2019-08-27 16:12 ` shuah
2019-08-27 15:37 ` linux-next: Tree for Aug 27 (mm/zsmalloc.c) Randy Dunlap
2019-08-28 5:30 ` Sergey Senozhatsky
2019-08-27 15:40 ` linux-next: Tree for Aug 27 (objtool) Randy Dunlap
2019-08-27 15:59 ` Josh Poimboeuf
2019-08-27 19:05 ` Randy Dunlap
2019-08-28 15:51 ` Josh Poimboeuf
2019-08-28 16:05 ` Randy Dunlap
2019-08-28 16:13 ` Josh Poimboeuf
2019-08-28 16:34 ` Josh Poimboeuf [this message]
2019-08-29 1:53 ` Masami Hiramatsu
2019-08-29 17:59 ` Josh Poimboeuf
2019-08-30 6:23 ` Masami Hiramatsu
2019-08-30 15:14 ` Masami Hiramatsu
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