From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Nadav Amit <namit@vmware.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 13/15] x86/static_call: Add inline static call implementation for x86-64
Date: Mon, 10 Jun 2019 13:55:13 -0500 [thread overview]
Message-ID: <20190610185513.pbtc7udpkfd5jsuu@treble> (raw)
In-Reply-To: <40096B8A-C063-4219-89FC-A8E42981BF28@vmware.com>
On Mon, Jun 10, 2019 at 06:45:52PM +0000, Nadav Amit wrote:
> > On Jun 10, 2019, at 11:33 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > On Wed, Jun 05, 2019 at 03:08:06PM +0200, Peter Zijlstra wrote:
> >> --- a/arch/x86/include/asm/static_call.h
> >> +++ b/arch/x86/include/asm/static_call.h
> >> @@ -2,6 +2,20 @@
> >> #ifndef _ASM_STATIC_CALL_H
> >> #define _ASM_STATIC_CALL_H
> >>
> >> +#include <asm/asm-offsets.h>
> >> +
> >> +#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
> >> +
> >> +/*
> >> + * This trampoline is only used during boot / module init, so it's safe to use
> >> + * the indirect branch without a retpoline.
> >> + */
> >> +#define __ARCH_STATIC_CALL_TRAMP_JMP(key, func) \
> >> + ANNOTATE_RETPOLINE_SAFE \
> >> + "jmpq *" __stringify(key) "+" __stringify(SC_KEY_func) "(%rip) \n"
> >> +
> >> +#else /* !CONFIG_HAVE_STATIC_CALL_INLINE */
> >
> > I wonder if we can simplify this (and drop the indirect branch) by
> > getting rid of the above cruft, and instead just use the out-of-line
> > trampoline as the default for inline as well.
> >
> > Then the inline case could fall back to the out-of-line implementation
> > (by patching the trampoline's jmp dest) before static_call_initialized
> > is set.
>
> I must be missing some context - but what guarantees that this indirect
> branch would be exactly 5 bytes long? Isn’t there an assumption that this
> would be the case? Shouldn’t there be some handling of the padding?
We don't patch the indirect branch. It's just part of a temporary
trampoline which is called by the call site, and which does "jmp
key->func" during boot until static call initialization is done.
(Though I'm suggesting removing that.)
--
Josh
next prev parent reply other threads:[~2019-06-10 18:55 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
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 [this message]
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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