From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.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>
Subject: Re: [RFC PATCH 1/3] static_call: Add static call infrastructure
Date: Sat, 10 Nov 2018 12:56:33 +0100 [thread overview]
Message-ID: <CAKv+Gu8Aip+KWTyC-i0wPC7YTrd2QXDjUFPpRtbzBfc6HVCktw@mail.gmail.com> (raw)
In-Reply-To: <20181109203459.wbftlkxcvfnwo2bm@treble>
On 9 November 2018 at 21:34, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> On Fri, Nov 09, 2018 at 02:57:46PM -0500, Steven Rostedt wrote:
>> On Fri, 9 Nov 2018 13:35:05 -0600
>> Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>>
..
>> > > So what's the reason for skipping init calls?
>> >
>> > This is the runtime changing code (static_call_update). Presumably the
>> > init sections no longer exist and we shouldn't write to any (former)
>> > call sites there.
>> >
>> > That's probably a dangerous assumption though... If
>> > static_call_update() were called early, some init code might not get
>> > patched and then call into the wrong function.
>> >
>> > I'm thinking we should just disallow static call sites in init sections.
>> > I can't think of a good reason why they would be needed in init code.
>> > We can WARN when detecting them during boot / module init.
>> >
>>
>> What I would do is to allow init (like ftrace now does). I have
>> ftrace_free_init_mem() that removes all the mcount references for init
>> calls from its list. You could add a static_call_free_init() to
>> kernel_init() in init/main.c too.
>
> That makes sense for ftrace, but I don't see much point in allowing it
> for static calls. Maybe we could just add support for it later if it
> turns out to be useful.
>
I don't see how you can prevent that. Some arch may use a static call
in its version of some library code which could be used anywhere,
including in .init code.
next prev parent reply other threads:[~2018-11-10 11:56 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-08 21:15 [PATCH RFC 0/3] Static calls Josh Poimboeuf
2018-11-08 21:15 ` [RFC PATCH 1/3] static_call: Add static call infrastructure Josh Poimboeuf
2018-11-09 9:51 ` Ard Biesheuvel
2018-11-09 14:55 ` Josh Poimboeuf
2018-11-09 13:39 ` Ard Biesheuvel
2018-11-09 15:10 ` Josh Poimboeuf
2018-11-09 15:14 ` Ard Biesheuvel
2018-11-09 17:25 ` Ard Biesheuvel
2018-11-09 17:31 ` Josh Poimboeuf
2018-11-09 17:33 ` Ard Biesheuvel
2018-11-09 17:46 ` Josh Poimboeuf
2018-11-09 17:52 ` Ard Biesheuvel
2018-11-09 17:53 ` Ard Biesheuvel
2018-11-09 19:03 ` Josh Poimboeuf
2018-11-09 19:12 ` Ard Biesheuvel
2018-11-09 17:33 ` Josh Poimboeuf
2018-11-09 18:33 ` Steven Rostedt
2018-11-09 19:35 ` Josh Poimboeuf
2018-11-09 19:57 ` Steven Rostedt
2018-11-09 20:34 ` Josh Poimboeuf
2018-11-10 5:10 ` Steven Rostedt
2018-11-10 11:58 ` Ard Biesheuvel
2018-11-10 13:09 ` Steven Rostedt
2018-11-12 3:07 ` Josh Poimboeuf
2018-11-12 4:39 ` Ard Biesheuvel
2018-11-12 4:56 ` Josh Poimboeuf
2018-11-12 5:02 ` Ard Biesheuvel
2018-11-10 11:56 ` Ard Biesheuvel [this message]
2018-11-08 21:15 ` [RFC PATCH 2/3] x86/static_call: Add x86 unoptimized static call implementation Josh Poimboeuf
2018-11-08 21:15 ` [RFC PATCH 3/3] x86/static_call: Add optimized static call implementation for 64-bit Josh Poimboeuf
2018-11-08 21:24 ` [PATCH RFC 0/3] Static calls Josh Poimboeuf
2018-11-09 7:28 ` Ingo Molnar
2018-11-09 7:50 ` Ingo Molnar
2018-11-09 13:50 ` Ard Biesheuvel
2018-11-09 15:20 ` Josh Poimboeuf
2018-11-10 23:20 ` Peter Zijlstra
2018-11-11 13:42 ` Ard Biesheuvel
2018-11-11 14:25 ` Peter Zijlstra
2018-11-09 14:45 ` Josh Poimboeuf
2018-11-12 5:02 ` Ingo Molnar
2018-11-12 5:30 ` Josh Poimboeuf
2018-11-12 9:39 ` Ard Biesheuvel
2018-11-12 22:52 ` Josh Poimboeuf
2018-11-12 17:03 ` Steven Rostedt
2018-11-12 22:56 ` Josh Poimboeuf
2018-11-12 5:34 ` Andy Lutomirski
2018-11-09 15:16 ` Andy Lutomirski
2018-11-09 15:21 ` Josh Poimboeuf
2018-11-09 16:41 ` Josh Poimboeuf
2018-11-09 18:42 ` Steven Rostedt
2018-11-09 19:05 ` Andy Lutomirski
2018-11-09 19:37 ` Steven Rostedt
2018-11-09 19:44 ` Josh Poimboeuf
2018-11-09 19:59 ` Steven Rostedt
2018-11-09 20:36 ` Josh Poimboeuf
2018-11-10 15:13 ` Masami Hiramatsu
2018-11-09 20:53 ` Rasmus Villemoes
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