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From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	rostedt@goodmis.org, mhiramat@kernel.org, bristot@redhat.com,
	jbaron@akamai.com, torvalds@linux-foundation.org,
	tglx@linutronix.de, namit@vmware.com, hpa@zytor.com,
	luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com,
	jeyu@kernel.org
Subject: Re: [PATCH v4 03/16] x86/alternatives,jump_label: Provide better text_poke() batching interface
Date: Mon, 21 Oct 2019 11:21:58 +0200	[thread overview]
Message-ID: <20191021092158.GA1800@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20191021084802.GA825@gmail.com>

On Mon, Oct 21, 2019 at 10:48:02AM +0200, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > --- a/arch/x86/kernel/jump_label.c
> > +++ b/arch/x86/kernel/jump_label.c
> > @@ -35,18 +35,19 @@ static void bug_at(unsigned char *ip, in
> >  	BUG();
> >  }
> >  
> > -static void __jump_label_set_jump_code(struct jump_entry *entry,
> > -				       enum jump_label_type type,
> > -				       union jump_code_union *code,
> > -				       int init)
> > +static const void *
> > +__jump_label_set_jump_code(struct jump_entry *entry, enum jump_label_type type, int init)
> >  {
> > +	static union jump_code_union code; /* relies on text_mutex */
> >  	const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
> >  	const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
> >  	const void *expect;
> >  	int line;
> >  
> > -	code->jump = 0xe9;
> > -	code->offset = jump_entry_target(entry) -
> > +	lockdep_assert_held(&text_mutex);
> > +
> > +	code.jump = JMP32_INSN_OPCODE;
> > +	code.offset = jump_entry_target(entry) -
> >  		       (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
> >  
> >  	if (init) {
> > @@ -54,23 +55,23 @@ static void __jump_label_set_jump_code(s
> >  	} else if (type == JUMP_LABEL_JMP) {
> >  		expect = ideal_nop; line = __LINE__;
> >  	} else {
> > -		expect = code->code; line = __LINE__;
> > +		expect = code.code; line = __LINE__;
> 
> Side note: the whole 'line' logic looked weird to me and it obsfuscates 
> the logic a bit, and I had to look it up to see what it's about: 
> improving the debug output of text-patching crashes.
> 
> How about something like the below on top of your queue? We have %phD 
> that can nicely print instructions in hex.

I have a patch like that somewhere; see here:

  https://lkml.kernel.org/r/20191007090012.00469193.6@infradead.org

But yes, the __LINE__ thing is mostly about identifying which case it is
and I suppose we can infer that when we have the expected text printed
too.

  reply	other threads:[~2019-10-21  9:22 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18  7:35 [PATCH v4 00/16] Rewrite x86/ftrace to use text_poke (and more) Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 01/16] x86/alternatives: Teach text_poke_bp() to emulate instructions Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 02/16] x86/alternatives: Update int3_emulate_push() comment Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 03/16] x86/alternatives,jump_label: Provide better text_poke() batching interface Peter Zijlstra
2019-10-21  8:48   ` Ingo Molnar
2019-10-21  9:21     ` Peter Zijlstra [this message]
2019-10-18  7:35 ` [PATCH v4 04/16] x86/alternatives: Add and use text_gen_insn() helper Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 05/16] x86/ftrace: Use text_poke() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 06/16] x86/mm: Remove set_kernel_text_r[ow]() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 07/16] x86/alternative: Add text_opcode_size() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 08/16] x86/ftrace: Use text_gen_insn() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 09/16] x86/alternative: Remove text_poke_loc::len Peter Zijlstra
2019-10-21  8:58   ` Ingo Molnar
2019-10-21  9:02     ` Ingo Molnar
2019-10-18  7:35 ` [PATCH v4 10/16] x86/alternative: Shrink text_poke_loc Peter Zijlstra
2019-10-21  9:01   ` Ingo Molnar
2019-10-21  9:25     ` Peter Zijlstra
2019-10-21  9:33       ` Ingo Molnar
2019-10-18  7:35 ` [PATCH v4 11/16] x86/kprobes: Convert to text-patching.h Peter Zijlstra
2019-10-21 14:57   ` Masami Hiramatsu
2019-10-18  7:35 ` [PATCH v4 12/16] x86/kprobes: Fix ordering Peter Zijlstra
2019-10-22  1:35   ` Masami Hiramatsu
2019-10-22 10:31     ` Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 13/16] arm/ftrace: Use __patch_text_real() Peter Zijlstra
2019-10-28 16:25   ` Will Deacon
2019-10-28 16:34     ` Peter Zijlstra
2019-10-28 16:35       ` Peter Zijlstra
2019-10-28 16:47       ` Will Deacon
2019-10-28 16:55         ` Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 14/16] module: Remove set_all_modules_text_*() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 15/16] module: Move where we mark modules RO,X Peter Zijlstra
2019-10-21 13:53   ` Josh Poimboeuf
2019-10-21 14:14     ` Peter Zijlstra
2019-10-21 15:34       ` Peter Zijlstra
2019-10-21 15:44         ` Peter Zijlstra
2019-10-21 16:11         ` Peter Zijlstra
2019-10-22 11:31           ` Heiko Carstens
2019-10-22 12:31             ` Peter Zijlstra
2019-10-23 11:48       ` Peter Zijlstra
2019-10-23 15:16         ` Peter Zijlstra
2019-10-23 17:15           ` Josh Poimboeuf
2019-10-24 10:59             ` Peter Zijlstra
2019-10-24 18:31               ` Josh Poimboeuf
2019-10-24 20:33                 ` Peter Zijlstra
2019-10-23 17:00         ` Josh Poimboeuf
2019-10-24 13:16           ` Peter Zijlstra
2019-10-25  6:44             ` Petr Mladek
2019-10-25  8:43               ` Peter Zijlstra
2019-10-25 10:06                 ` Peter Zijlstra
2019-10-25 13:50                   ` Josh Poimboeuf
2019-10-26  1:17                   ` Josh Poimboeuf
2019-10-28 10:07                     ` Peter Zijlstra
2019-10-28 10:43                     ` Peter Zijlstra
2019-10-25  9:16               ` Peter Zijlstra
2019-10-22  2:21   ` Steven Rostedt
2019-10-22 20:24     ` Peter Zijlstra
2019-10-22 20:40       ` Steven Rostedt
2019-10-23  9:07         ` Peter Zijlstra
2019-10-23 18:52       ` Steven Rostedt
2019-10-24 10:16         ` Peter Zijlstra
2019-10-24 10:18           ` Peter Zijlstra
2019-10-24 15:00           ` Steven Rostedt
2019-10-24 16:43             ` Peter Zijlstra
2019-10-24 18:17               ` Steven Rostedt
2019-10-24 20:24                 ` Peter Zijlstra
2019-10-24 20:28                   ` Steven Rostedt
2019-10-18  7:35 ` [PATCH v4 16/16] ftrace: Merge ftrace_module_{init,enable}() Peter Zijlstra
2019-10-18  8:20   ` Peter Zijlstra
2019-10-21  9:09 ` [PATCH v4 00/16] Rewrite x86/ftrace to use text_poke (and more) Ingo Molnar
2019-10-21 13:38   ` Steven Rostedt

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