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Subject: Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64
From:   Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <20181129122156.782e739e@gandalf.local.home>
Date:   Thu, 29 Nov 2018 09:41:33 -0800
Cc:     Peter Zijlstra <peterz@infradead.org>,
        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>
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References: <20181126200801.GW2113@hirez.programming.kicks-ass.net> <20181126212628.4apztfazichxnt7r@treble> <20181127084330.GX2113@hirez.programming.kicks-ass.net> <CALCETrXam8JBtXE3S97Vyb_=+pmjgr23SoZ-Dm5pmYtwZYA+7Q@mail.gmail.com> <20181129094210.GC2131@hirez.programming.kicks-ass.net> <ECF632D9-581B-40B7-9F0A-6B5607A4D0E3@amacapital.net> <20181129143853.GO2131@hirez.programming.kicks-ass.net> <20181129163342.tp5wlfcyiazwwyoh@treble> <20181129164914.GA9027@hirez.programming.kicks-ass.net> <0FDA053D-7ADC-4F42-AEA5-99DA155FCED0@amacapital.net> <20181129171539.GD9027@hirez.programming.kicks-ass.net> <20181129122000.7fb4fb04@gandalf.local.home> <20181129122156.782e739e@gandalf.local.home>
To:     Steven Rostedt <rostedt@goodmis.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Nov 29, 2018, at 9:21 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
>=20
> On Thu, 29 Nov 2018 12:20:00 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>=20
>=20
>> r8 =3D return address
>> r9 =3D function to call
>>=20
>=20
> Bad example, r8 and r9 are args, but r10 and r11 are available.
>=20
> -- Steve
>=20
>>    push r8
>>    jmp *r9
>>=20
>> Then have the regs->ip point to that trampoline.

Cute. That=E2=80=99ll need ORC annotations and some kind of retpoline to rep=
lace the indirect jump, though.

>>=20
>> -- Steve
>=20