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From: Jessica Yu <jeyu@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com,
	torvalds@linux-foundation.org, tglx@linutronix.de,
	mingo@kernel.org, namit@vmware.com, hpa@zytor.com,
	luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com
Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()
Date: Tue, 15 Oct 2019 15:07:40 +0200	[thread overview]
Message-ID: <20191015130739.GA23565@linux-8ccs> (raw)
In-Reply-To: <20191011125903.GN2359@hirez.programming.kicks-ass.net>

+++ Peter Zijlstra [11/10/19 14:59 +0200]:
>On Thu, Oct 10, 2019 at 07:28:19PM +0200, Peter Zijlstra wrote:
>
>> Really the best solution is to move all the poking into
>> ftrace_module_init(), before we mark it RO+X. That's what I'm going to
>> do for jump_label and static_call as well, I just need to add that extra
>> notifier callback.
>
>OK, so I started writing that patch... or rather, I wrote the patch and
>started on the Changelog when I ran into trouble describing why we need
>it.
>
>That is, I'm struggling to explain why we cannot flip
>prepare_coming_module() and complete_formation().
>
>Yes, it breaks ftrace, but I'm thinking that is all it breaks. So let me
>see if we can cure that.

I'm having trouble visualizing what changes you're planning on making.
I get that you want to squash ftrace_module_enable() into
ftrace_module_init(), before module_enable_ro(). I'm fine with that as
long as the races Steven described are addressed for affected arches.
And livepatch should be OK as long as klp_module_coming() is always
called *after* ftrace_module_enable(). But are you moving
klp_module_coming() before the module_enable_* calls as well?  And if
so, why?

>The fact that it is executable; also the fact that you do it right after
>we mark it ro. Flipping the memory protections back and forth is just
>really poor everything.
>
>Once this ftrace thing is sorted, we'll change x86 to _refuse_ to make
>executable (kernel) memory writable.

Not sure if relevant, but just thought I'd clarify: IIRC,
klp_module_coming() is not poking the coming module, but it calls
module_enable_ro() on itself (the livepatch module) so it can apply
relocations and such on the new code, which lives inside the livepatch
module, and it needs to possibly do this numerous times over the
lifetime of the patch module for any coming module it is responsible
for patching (i.e., call module_enable_ro() on the patch module, not
necessarily the coming module). So I am not be sure why
klp_module_coming() should be moved before complete_formation(). I
hope I'm remembering the details correctly, livepatch folks feel free
to chime in if I'm incorrect here.

  parent reply	other threads:[~2019-10-15 13:07 UTC|newest]

Thread overview: 128+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-07  9:02 [RESEND] everything text-poke: ftrace, modules, static_call and jump_label Peter Zijlstra
2019-10-07  8:17 ` [PATCH v3 0/6] Rewrite x86/ftrace to use text_poke() Peter Zijlstra
2019-10-07  8:17   ` [PATCH v3 1/6] x86/alternatives: Teach text_poke_bp() to emulate instructions Peter Zijlstra
2019-10-08 14:29     ` Borislav Petkov
2019-10-08 14:40       ` Steven Rostedt
2019-10-08 14:50         ` Borislav Petkov
2019-10-08 14:48       ` Peter Zijlstra
2019-10-08 14:54         ` Borislav Petkov
2019-10-08 15:04           ` Steven Rostedt
2019-10-08 15:24             ` Borislav Petkov
2019-10-09 12:03     ` Daniel Bristot de Oliveira
2019-10-07  8:17   ` [PATCH v3 2/6] x86/alternatives: Update int3_emulate_push() comment Peter Zijlstra
2019-10-07  8:17   ` [PATCH v3 3/6] x86/alternatives,jump_label: Provide better text_poke() batching interface Peter Zijlstra
2019-10-09 12:04     ` Daniel Bristot de Oliveira
2019-10-07  8:17   ` [PATCH v3 4/6] x86/alternatives: Add and use text_gen_insn() helper Peter Zijlstra
2019-10-08  6:23     ` Masami Hiramatsu
2019-10-08  8:15       ` Peter Zijlstra
2019-10-07  8:17   ` [PATCH v3 5/6] x86/ftrace: Use text_poke() Peter Zijlstra
2019-10-08 14:43     ` Steven Rostedt
2019-10-08 17:11       ` Peter Zijlstra
2019-10-08 17:27         ` Steven Rostedt
2019-10-10  2:41       ` Steven Rostedt
2019-10-10  9:20         ` Peter Zijlstra
2019-10-10 13:19           ` Steven Rostedt
2019-10-10 14:05             ` Peter Zijlstra
2019-10-10 15:54               ` Steven Rostedt
2019-10-10 17:28                 ` Peter Zijlstra
2019-10-10 17:48                   ` Steven Rostedt
2019-10-11 10:45                     ` Peter Zijlstra
2019-10-11 10:47                       ` Peter Zijlstra
2019-10-11 10:50                         ` Peter Zijlstra
2019-10-11 12:59                   ` Peter Zijlstra
2019-10-11 13:33                     ` Steven Rostedt
2019-10-11 13:45                       ` Peter Zijlstra
2019-10-15 13:07                     ` Jessica Yu [this message]
2019-10-15 13:56                       ` Peter Zijlstra
2019-10-15 14:11                         ` Peter Zijlstra
2019-10-15 14:13                         ` Miroslav Benes
2019-10-15 15:06                           ` Joe Lawrence
2019-10-15 15:31                             ` Jessica Yu
2019-10-15 22:17                               ` Joe Lawrence
2019-10-15 22:27                                 ` Steven Rostedt
2019-10-16  7:42                                   ` Peter Zijlstra
2019-10-16 10:15                                     ` Miroslav Benes
2019-10-21 15:05                                     ` Josh Poimboeuf
2020-01-20 16:50                                       ` Josh Poimboeuf
2020-01-21  8:35                                         ` Miroslav Benes
2020-01-21 16:10                                           ` Josh Poimboeuf
2020-01-22 10:09                                             ` Miroslav Benes
2020-01-22 21:42                                               ` Josh Poimboeuf
2020-01-28  9:28                                                 ` Miroslav Benes
2020-01-28 15:00                                                   ` Josh Poimboeuf
2020-01-28 15:40                                                     ` Petr Mladek
2020-01-28 17:02                                                       ` Josh Poimboeuf
2020-01-29  0:46                                                         ` Jiri Kosina
2020-01-29  2:17                                                           ` Josh Poimboeuf
2020-01-29  3:14                                                             ` Jiri Kosina
2020-01-29 12:28                                                         ` Miroslav Benes
2020-01-29 15:59                                                           ` Josh Poimboeuf
2020-01-30  9:53                                                             ` Petr Mladek
2020-01-30 14:17                                                               ` Josh Poimboeuf
2020-01-31  7:17                                                                 ` Petr Mladek
2020-01-22 12:15                                             ` Miroslav Benes
2020-01-22 15:05                                               ` Miroslav Benes
2020-01-22 22:03                                                 ` Josh Poimboeuf
2020-01-23 10:19                                                   ` Martin Jambor
2019-10-16  7:49                                   ` Peter Zijlstra
2019-10-16 10:20                                     ` Miroslav Benes
2019-10-16 13:29                                       ` Miroslav Benes
2019-10-18 13:03                                         ` Jessica Yu
2019-10-18 13:40                                           ` Petr Mladek
2019-10-21 14:14                                             ` Jessica Yu
2019-10-21 15:31                                             ` Josh Poimboeuf
2019-10-22  8:27                                           ` Miroslav Benes
2019-10-22 14:31                                             ` Josh Poimboeuf
2019-10-23  9:04                                               ` Miroslav Benes
2019-10-16  6:51                             ` Miroslav Benes
2019-10-16  9:23                               ` Peter Zijlstra
2019-10-16  9:36                                 ` Jessica Yu
2019-10-16  9:51                                   ` Peter Zijlstra
2019-10-16 12:39                               ` Peter Zijlstra
2019-10-22  8:45                                 ` Miroslav Benes
2019-10-15 14:42                         ` Peter Zijlstra
2019-10-15 18:31                           ` Peter Zijlstra
2019-10-15 15:51                         ` Jessica Yu
2019-10-15 13:28                     ` Steven Rostedt
2019-10-15 13:42                       ` Peter Zijlstra
2019-10-15 16:09                       ` Jessica Yu
2019-10-07  8:17   ` [PATCH v3 6/6] x86/mm: Remove set_kernel_text_r[ow]() Peter Zijlstra
2019-10-08 15:07   ` [PATCH v3 0/6] Rewrite x86/ftrace to use text_poke() Steven Rostedt
2019-10-07  8:25 ` [PATCH v2 0/4] Propagate module notifier errors Peter Zijlstra
2019-10-07  8:25   ` [PATCH v2 1/4] notifier: Fix broken error handling pattern Peter Zijlstra
2019-10-10 22:01     ` Rafael J. Wysocki
2019-10-07  8:25   ` [PATCH v2 2/4] module: Fix up module_notifier return values Peter Zijlstra
2019-10-23 19:25     ` Steven Rostedt
2019-10-07  8:25   ` [PATCH v2 3/4] module: Properly propagate MODULE_STATE_COMING failure Peter Zijlstra
2019-10-08 13:08     ` Miroslav Benes
2019-10-07  8:25   ` [PATCH v2 4/4] jump_label,module: Fix module lifetime for __jump_label_mod_text_reserved Peter Zijlstra
2019-10-23 19:29     ` Steven Rostedt
2019-10-07  8:27 ` [PATCH v2 00/13] Add static_call() Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 01/13] compiler.h: Make __ADDRESSABLE() symbol truly unique Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 02/13] static_call: Add basic static call infrastructure Peter Zijlstra
2019-10-07 11:33     ` Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 03/13] static_call: Add inline " Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 04/13] static_call: Avoid kprobes on inline static_call()s Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 05/13] x86/static_call: Add out-of-line static call implementation Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 06/13] x86/static_call: Add inline static call implementation for x86-64 Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 07/13] static_call: Simple self-test Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 08/13] tracepoints: Use static_call Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 09/13] x86/alternatives: Teach text_poke_bp() to emulate RET Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 10/13] static_call: Add static_cond_call() Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 11/13] static_call: Handle tail-calls Peter Zijlstra
2019-10-07  8:27   ` [PATCH v2 12/13] static_call: Allow early init Peter Zijlstra
2019-10-07  8:27   ` [RFC][PATCH v2 13/13] x86/perf, static_call: Optimize x86_pmu methods Peter Zijlstra
2019-10-07 11:33   ` [PATCH v2 00/13] Add static_call() Peter Zijlstra
2019-10-07  8:44 ` [RFC][PATCH 0/9] Variable size jump_label support Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 1/9] jump_label, x86: Strip ASM " Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 2/9] jump_label, x86: Factor out the __jump_table generation Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 3/9] jump_label, x86: Remove init NOP optimization Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 4/9] jump_label, x86: Improve error when we fail expected text Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 5/9] jump_label, x86: Introduce jump_entry_size() Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 6/9] jump_label, x86: Add variable length patching support Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 7/9] jump_label,objtool: Validate variable size jump labels Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 8/9] jump_label,objtool: Generate possible statistics Peter Zijlstra
2019-10-07  8:44   ` [RFC][PATCH 9/9] jump_label, x86: Enable JMP8/NOP2 support Peter Zijlstra
2019-10-07 12:07   ` [RFC][PATCH 0/9] Variable size jump_label support Peter Zijlstra
2019-10-07 12:55     ` Ingo Molnar
2019-10-07 15:08       ` Steven Rostedt

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