From: Nadav Amit <namit@vmware.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
the arch/x86 maintainers <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Andy Lutomirski <luto@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Jason Baron <jbaron@akamai.com>, Jiri Kosina <jkosina@suse.cz>,
David Laight <David.Laight@ACULAB.COM>,
Borislav Petkov <bp@alien8.de>, Julia Cartwright <julia@ni.com>,
Jessica Yu <jeyu@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Edward Cree <ecree@solarflare.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: Re: [PATCH 11/15] static_call: Add inline static call infrastructure
Date: Mon, 10 Jun 2019 18:33:26 +0000 [thread overview]
Message-ID: <757720BF-5DC6-44E7-A549-E542096BC077@vmware.com> (raw)
In-Reply-To: <20190610171929.3xemvsykvkswcvya@treble>
> On Jun 10, 2019, at 10:19 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> On Fri, Jun 07, 2019 at 10:37:56AM +0200, Peter Zijlstra wrote:
>>>> +}
>>>> +
>>>> +static int static_call_module_notify(struct notifier_block *nb,
>>>> + unsigned long val, void *data)
>>>> +{
>>>> + struct module *mod = data;
>>>> + int ret = 0;
>>>> +
>>>> + cpus_read_lock();
>>>> + static_call_lock();
>>>> +
>>>> + switch (val) {
>>>> + case MODULE_STATE_COMING:
>>>> + module_disable_ro(mod);
>>>> + ret = static_call_add_module(mod);
>>>> + module_enable_ro(mod, false);
>>>
>>> Doesn’t it cause some pages to be W+X ?
>
> How so?
>
>>> Can it be avoided?
>>
>> I don't know why it does this, jump_labels doesn't seem to need this,
>> and I'm not seeing what static_call needs differently.
>
> I forgot why I did this, but it's probably for the case where there's a
> static call site in module init code. It deserves a comment.
>
> Theoretically, jump labels need this to.
>
> BTW, there's a change coming that will require the text_mutex before
> calling module_{disable,enable}_ro().
I think that eventually, the most secure flow is for the module executable
to be write-protected immediately after the module signature is checked and
then use text_poke() to change the code without removing the
write-protection in such manner.
Ideally, these pieces of code (module signature check and static-key/call
mechanisms) would somehow be isolated.
I wonder whether static-calls in init-code cannot just be avoided. They
would most likely introduce more overhead in patching than they would save
in execution time.
next prev parent reply other threads:[~2019-06-10 18:33 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-05 13:07 [PATCH 00/15] x86 cleanups and static_call() Peter Zijlstra
2019-06-05 13:07 ` [PATCH 01/15] x86/entry/32: Clean up return from interrupt preemption path Peter Zijlstra
2019-06-07 14:21 ` Josh Poimboeuf
2019-06-05 13:07 ` [PATCH 02/15] x86: Move ENCODE_FRAME_POINTER to asm/frame.h Peter Zijlstra
2019-06-07 14:24 ` Josh Poimboeuf
2019-06-05 13:07 ` [PATCH 03/15] x86/kprobes: Fix frame pointer annotations Peter Zijlstra
2019-06-07 13:02 ` Masami Hiramatsu
2019-06-07 13:36 ` Josh Poimboeuf
2019-06-07 15:21 ` Masami Hiramatsu
2019-06-11 8:12 ` Peter Zijlstra
2019-06-05 13:07 ` [PATCH 04/15] x86/ftrace: Add pt_regs frame annotations Peter Zijlstra
2019-06-07 14:45 ` Josh Poimboeuf
2019-06-05 13:07 ` [PATCH 05/15] x86_32: Provide consistent pt_regs Peter Zijlstra
2019-06-07 13:13 ` Masami Hiramatsu
2019-06-07 19:32 ` Josh Poimboeuf
2019-06-11 8:14 ` Peter Zijlstra
2019-06-05 13:07 ` [PATCH 06/15] x86_32: Allow int3_emulate_push() Peter Zijlstra
2019-06-05 13:08 ` [PATCH 07/15] x86: Add int3_emulate_call() selftest Peter Zijlstra
2019-06-10 16:52 ` Josh Poimboeuf
2019-06-10 16:57 ` Andy Lutomirski
2019-06-11 8:17 ` Peter Zijlstra
2019-06-05 13:08 ` [PATCH 08/15] x86/alternatives: Teach text_poke_bp() to emulate instructions Peter Zijlstra
2019-06-07 5:41 ` Nadav Amit
2019-06-07 8:20 ` Peter Zijlstra
2019-06-07 14:27 ` Masami Hiramatsu
2019-06-07 15:47 ` Masami Hiramatsu
2019-06-07 17:34 ` Peter Zijlstra
2019-06-07 17:48 ` Linus Torvalds
2019-06-11 10:44 ` Peter Zijlstra
2019-06-07 18:10 ` Andy Lutomirski
2019-06-07 20:22 ` hpa
2019-06-11 8:03 ` Peter Zijlstra
2019-06-11 12:08 ` Peter Zijlstra
2019-06-11 12:34 ` Peter Zijlstra
2019-06-11 12:42 ` Peter Zijlstra
2019-06-11 15:22 ` Steven Rostedt
2019-06-11 15:52 ` Steven Rostedt
2019-06-11 15:55 ` Peter Zijlstra
2019-06-12 19:44 ` Nadav Amit
2019-06-17 14:42 ` Peter Zijlstra
2019-06-17 17:06 ` Nadav Amit
2019-06-17 17:25 ` Andy Lutomirski
2019-06-17 19:26 ` Peter Zijlstra
2019-06-11 15:54 ` Andy Lutomirski
2019-06-11 16:11 ` Steven Rostedt
2019-06-17 14:31 ` Peter Zijlstra
2019-06-12 17:09 ` Peter Zijlstra
2019-06-10 16:57 ` Josh Poimboeuf
2019-06-11 15:14 ` Steven Rostedt
2019-06-11 15:52 ` Peter Zijlstra
2019-06-11 16:21 ` Peter Zijlstra
2019-06-12 14:44 ` Peter Zijlstra
2019-06-05 13:08 ` [PATCH 09/15] compiler.h: Make __ADDRESSABLE() symbol truly unique Peter Zijlstra
2019-06-05 13:08 ` [PATCH 10/15] static_call: Add basic static call infrastructure Peter Zijlstra
2019-06-06 22:44 ` Nadav Amit
2019-06-07 8:28 ` Peter Zijlstra
2019-06-07 8:49 ` Ard Biesheuvel
2019-06-07 16:33 ` Andy Lutomirski
2019-06-07 16:58 ` Nadav Amit
2019-10-02 13:54 ` Peter Zijlstra
2019-10-02 20:48 ` Josh Poimboeuf
2019-06-05 13:08 ` [PATCH 11/15] static_call: Add inline " Peter Zijlstra
2019-06-06 22:24 ` Nadav Amit
2019-06-07 8:37 ` Peter Zijlstra
2019-06-07 16:35 ` Nadav Amit
2019-06-07 17:41 ` Peter Zijlstra
2019-06-10 17:19 ` Josh Poimboeuf
2019-06-10 18:33 ` Nadav Amit [this message]
2019-06-10 18:42 ` Josh Poimboeuf
2019-10-01 12:00 ` Peter Zijlstra
2019-06-05 13:08 ` [PATCH 12/15] x86/static_call: Add out-of-line static call implementation Peter Zijlstra
2019-06-07 6:13 ` Nadav Amit
2019-06-07 7:51 ` Steven Rostedt
2019-06-07 8:38 ` Peter Zijlstra
2019-06-07 8:52 ` Peter Zijlstra
2019-06-05 13:08 ` [PATCH 13/15] x86/static_call: Add inline static call implementation for x86-64 Peter Zijlstra
2019-06-07 5:50 ` Nadav Amit
2019-06-10 18:33 ` Josh Poimboeuf
2019-06-10 18:45 ` Nadav Amit
2019-06-10 18:55 ` Josh Poimboeuf
2019-06-10 19:20 ` Nadav Amit
2019-10-01 14:43 ` Peter Zijlstra
2019-06-05 13:08 ` [PATCH 14/15] static_call: Simple self-test module Peter Zijlstra
2019-06-10 17:24 ` Josh Poimboeuf
2019-06-11 8:29 ` Peter Zijlstra
2019-06-11 13:02 ` Josh Poimboeuf
2019-06-05 13:08 ` [PATCH 15/15] tracepoints: Use static_call Peter Zijlstra
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