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From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.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@ni.com, jeyu@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64
Date: Thu, 29 Nov 2018 12:20:00 -0500
Message-ID: <20181129122000.7fb4fb04@gandalf.local.home> (raw)
In-Reply-To: <20181129171539.GD9027@hirez.programming.kicks-ass.net>

On Thu, 29 Nov 2018 18:15:39 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> On Thu, Nov 29, 2018 at 08:59:31AM -0800, Andy Lutomirski wrote:
> 
> > If you make it conditional on CPL, do it for 32-bit as well, add
> > comments,   
> 
> > and convince yourself that there isn’t a better solution
> > (like pointing IP at a stub that retpolines to the target by reading
> > the function pointer, a la the unoptimizable version), then okay, I
> > guess, with only a small amount of grumbling.  
> 
> Right; so we _could_ grow the trampoline with a retpoline indirect call
> and ret. It just makes the trampoline a whole lot bigger, but it could
> work.

Can't we make use of the callee clobbered registers? I mean, we know
that call is being made when the int3 is triggered. Then we can save
the return address in one register, and the jump location in another,
and then just call a trampoline that does:

r8 = return address
r9 = function to call

	push r8
	jmp *r9

Then have the regs->ip point to that trampoline.

-- Steve

  reply index

Thread overview: 120+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-26 13:54 [PATCH v2 0/4] Static calls Josh Poimboeuf
2018-11-26 13:54 ` [PATCH v2 1/4] compiler.h: Make __ADDRESSABLE() symbol truly unique Josh Poimboeuf
2018-11-27  8:49   ` Ard Biesheuvel
2018-11-26 13:54 ` [PATCH v2 2/4] static_call: Add static call infrastructure Josh Poimboeuf
2018-11-26 13:54 ` [PATCH v2 3/4] x86/static_call: Add out-of-line static call implementation Josh Poimboeuf
2018-11-26 15:43   ` Peter Zijlstra
2018-11-26 16:19     ` Steven Rostedt
2018-11-26 13:55 ` [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64 Josh Poimboeuf
2018-11-26 16:02   ` Peter Zijlstra
2018-11-26 17:10     ` Josh Poimboeuf
2018-11-26 17:56       ` Josh Poimboeuf
2018-11-26 20:00         ` Peter Zijlstra
2018-11-26 20:08         ` Peter Zijlstra
2018-11-26 21:26           ` Josh Poimboeuf
2018-11-27  8:43             ` Peter Zijlstra
2018-11-27  8:50               ` Peter Zijlstra
2018-11-29  6:05               ` Andy Lutomirski
2018-11-29  9:42                 ` Peter Zijlstra
2018-11-29 13:11                   ` Josh Poimboeuf
2018-11-29 13:37                   ` Andy Lutomirski
2018-11-29 14:38                     ` Peter Zijlstra
2018-11-29 14:42                       ` Jiri Kosina
2018-11-29 16:33                       ` Josh Poimboeuf
2018-11-29 16:49                         ` Peter Zijlstra
2018-11-29 16:59                           ` Andy Lutomirski
2018-11-29 17:10                             ` Josh Poimboeuf
2018-11-29 22:01                               ` Peter Zijlstra
2018-11-29 22:14                                 ` Josh Poimboeuf
2018-11-29 22:22                                   ` Peter Zijlstra
2018-11-29 22:25                                     ` Andy Lutomirski
2018-11-29 22:30                                       ` Josh Poimboeuf
2018-11-29 17:15                             ` Peter Zijlstra
2018-11-29 17:20                               ` Steven Rostedt [this message]
2018-11-29 17:21                                 ` Steven Rostedt
2018-11-29 17:41                                   ` Andy Lutomirski
2018-11-29 17:45                                     ` Josh Poimboeuf
2018-11-29 17:52                                       ` Andy Lutomirski
2018-11-29 17:49                                     ` Steven Rostedt
2018-11-29 18:37                               ` Josh Poimboeuf
2018-11-29 16:50                         ` Linus Torvalds
2018-11-29 16:55                           ` Steven Rostedt
2018-11-29 17:02                           ` Andy Lutomirski
2018-11-29 17:07                             ` Peter Zijlstra
2018-11-29 17:31                               ` Andy Lutomirski
2018-11-29 17:35                                 ` Jiri Kosina
2018-11-29 17:13                             ` Steven Rostedt
2018-11-29 17:35                               ` Linus Torvalds
2018-11-29 17:44                                 ` Steven Rostedt
2018-11-29 17:50                                   ` Linus Torvalds
2018-11-29 17:54                                     ` Linus Torvalds
2018-11-29 17:58                                     ` Steven Rostedt
2018-11-29 18:23                                       ` Linus Torvalds
2018-11-29 18:47                                         ` Steven Rostedt
2018-11-29 18:58                                           ` Linus Torvalds
2018-11-29 19:08                                             ` Linus Torvalds
2018-11-29 19:11                                               ` Linus Torvalds
2018-12-10 23:58                                                 ` Pavel Machek
2018-12-11  1:43                                                   ` Linus Torvalds
2018-11-29 19:12                                               ` Steven Rostedt
2018-11-29 19:27                                               ` Andy Lutomirski
2018-11-29 20:24                                                 ` Josh Poimboeuf
2018-11-29 22:17                                                   ` Josh Poimboeuf
2018-11-29 23:04                                                   ` Linus Torvalds
2018-11-30 16:27                                                     ` Josh Poimboeuf
2018-12-11  9:41                                                       ` David Laight
2018-12-11 17:19                                                         ` Josh Poimboeuf
2018-12-12 18:29                                                     ` Josh Poimboeuf
2018-11-30 16:42                                                   ` Andy Lutomirski
2018-11-30 18:39                                                     ` Josh Poimboeuf
2018-11-30 19:45                                                       ` Linus Torvalds
2018-11-30 20:18                                                         ` Andy Lutomirski
2018-11-30 20:28                                                           ` Steven Rostedt
2018-11-30 20:59                                                             ` Andy Lutomirski
2018-11-30 21:01                                                               ` Steven Rostedt
2018-11-30 21:13                                                               ` Jiri Kosina
2018-11-30 21:10                                                           ` Josh Poimboeuf
2018-11-29 19:16                                             ` Steven Rostedt
2018-11-29 19:22                                               ` Josh Poimboeuf
2018-11-29 19:27                                                 ` Steven Rostedt
2018-11-30 22:16                                                 ` Rasmus Villemoes
2018-11-30 22:24                                                   ` Josh Poimboeuf
2018-11-29 19:24                                               ` Linus Torvalds
2018-11-29 19:28                                                 ` Andy Lutomirski
2018-11-29 19:31                                                 ` Steven Rostedt
2018-11-29 20:12                                             ` Josh Poimboeuf
2018-11-29 18:00                                     ` Andy Lutomirski
2018-11-29 18:42                                       ` Linus Torvalds
2018-11-29 18:55                                       ` Steven Rostedt
2018-11-29 17:29                             ` Linus Torvalds
2018-11-29 17:35                               ` Andy Lutomirski
2018-11-26 18:28       ` Andy Lutomirski
2018-11-26 20:14         ` Josh Poimboeuf
2018-11-27  8:46           ` Peter Zijlstra
2018-11-26 16:08   ` Peter Zijlstra
2018-11-26 16:11     ` Ard Biesheuvel
2018-11-26 16:33       ` Andy Lutomirski
2018-11-26 16:39       ` Peter Zijlstra
2018-11-26 16:44         ` Josh Poimboeuf
2018-11-26 14:01 ` [PATCH v2 0/4] Static calls Josh Poimboeuf
2018-11-26 20:54 ` Steven Rostedt
2018-11-26 22:24   ` Josh Poimboeuf
2018-11-26 22:53     ` Steven Rostedt
2018-12-04 23:08 ` Steven Rostedt
2018-12-04 23:41   ` Andy Lutomirski
2018-12-05 15:04     ` Josh Poimboeuf
2018-12-05 23:36       ` Andy Lutomirski
2018-12-07 16:06 ` Edward Cree
2018-12-07 16:49   ` Edward Cree
2018-12-11 18:05   ` Josh Poimboeuf
2018-12-12  5:59     ` Nadav Amit
2018-12-12 17:11       ` Edward Cree
2018-12-12 17:47         ` [RFC/WIP PATCH 0/2] dynamic calls Edward Cree
2018-12-12 17:50           ` [RFC PATCH 1/2] static_call: fix out-of-line static call implementation Edward Cree
2018-12-12 17:52           ` [RFC PATCH 2/2] net: core: rather hacky PoC implementation of dynamic calls Edward Cree
2018-12-12 18:14         ` [PATCH v2 0/4] Static calls Nadav Amit
2018-12-12 18:33           ` Edward Cree
2018-12-12 21:15             ` Nadav Amit
2018-12-12 21:36               ` Edward Cree
2018-12-12 21:45                 ` Nadav Amit
2018-12-10 23:57 ` Pavel Machek

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