From: David Laight <David.Laight@ACULAB.COM>
To: 'Peter Zijlstra' <peterz@infradead.org>,
"Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
Suleiman Souhlal <suleiman@google.com>, bpf <bpf@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Borislav Petkov" <bp@suse.de>,
Josh Poimboeuf <jpoimboe@kernel.org>,
"x86@kernel.org" <x86@kernel.org>
Subject: RE: [PATCH] objtool,x86: Teach decode about LOOP* instructions
Date: Wed, 7 Sep 2022 09:06:12 +0000 [thread overview]
Message-ID: <7ef4b0d724894ff394f9d8921f8c4332@AcuMS.aculab.com> (raw)
In-Reply-To: <Yxhd4EMKyoFoH9y4@hirez.programming.kicks-ass.net>
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?
They are so slow on Intel cpu that finding one ought to
deemed a bug!
Have you got jcxz (0xe3) in there?
They are fast on both Intel and AMD cpus - so are usable.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-09-07 9:06 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-07 0:55 [PATCH 0/2] x86/kprobes: Fixes for CONFIG_RETHUNK Masami Hiramatsu (Google)
2022-09-07 0:55 ` [PATCH 1/2] x86/kprobes: Fix kprobes instruction boudary check with CONFIG_RETHUNK Masami Hiramatsu (Google)
2022-09-07 7:06 ` Peter Zijlstra
2022-09-07 9:01 ` [PATCH] objtool,x86: Teach decode about LOOP* instructions Peter Zijlstra
2022-09-07 9:06 ` David Laight [this message]
2022-09-07 9:40 ` Peter Zijlstra
2022-09-07 11:13 ` David Laight
2022-09-07 9:12 ` [PATCH 1/2] x86/kprobes: Fix kprobes instruction boudary check with CONFIG_RETHUNK Masami Hiramatsu
2022-09-07 9:38 ` Peter Zijlstra
2022-09-07 9:53 ` Masami Hiramatsu
2022-09-07 8:02 ` Peter Zijlstra
2022-09-07 8:11 ` Peter Zijlstra
2022-09-07 9:49 ` Masami Hiramatsu
2022-09-07 10:19 ` Peter Zijlstra
2022-09-07 11:44 ` Peter Zijlstra
2022-09-07 13:05 ` Peter Zijlstra
2022-09-07 14:14 ` Masami Hiramatsu
2022-09-07 14:27 ` Peter Zijlstra
2022-09-07 15:22 ` Masami Hiramatsu
2022-09-07 12:56 ` Peter Zijlstra
2022-09-07 13:49 ` Masami Hiramatsu
2022-09-07 14:28 ` Peter Zijlstra
2022-09-07 12:59 ` Peter Zijlstra
2022-09-07 13:53 ` Masami Hiramatsu
2022-09-07 0:55 ` [PATCH 2/2] x86/kprobes: Fix optprobe optimization " Masami Hiramatsu (Google)
2022-09-07 6:52 ` [PATCH 0/2] x86/kprobes: Fixes for CONFIG_RETHUNK Peter Zijlstra
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