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Message-ID: <Yxhm9HuSKSjznSzP@hirez.programming.kicks-ass.net>
Date: Wed, 7 Sep 2022 11:40:04 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: David Laight <David.Laight@...lab.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...nel.org>,
Suleiman Souhlal <suleiman@...gle.com>,
bpf <bpf@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Borislav Petkov <bp@...e.de>,
Josh Poimboeuf <jpoimboe@...nel.org>,
"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH] objtool,x86: Teach decode about LOOP* instructions
On Wed, Sep 07, 2022 at 09:06:12AM +0000, David Laight wrote:
> From: Peter Zijlstra
> > Sent: 07 September 2022 10:01
> >
> > On Wed, Sep 07, 2022 at 09:06:45AM +0200, Peter Zijlstra wrote:
> > > On Wed, Sep 07, 2022 at 09:55:21AM +0900, Masami Hiramatsu (Google) wrote:
> > >
> > > > +/* Return the jump target address or 0 */
> > > > +static inline unsigned long insn_get_branch_addr(struct insn *insn)
> > > > +{
> > > > + switch (insn->opcode.bytes[0]) {
> > > > + case 0xe0: /* loopne */
> > > > + case 0xe1: /* loope */
> > > > + case 0xe2: /* loop */
> > >
> > > Oh cute, objtool doesn't know about those, let me go add them.
>
> Do they ever appear in the kernel?
No; that is, not on any of the random vmlinux.o images I checked this
morning.
Still, best to properly decode them anyway.
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