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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Mark Rutland' <mark.rutland@arm.com>,
        Ard Biesheuvel <ardb@kernel.org>
CC:     Peter Zijlstra <peterz@infradead.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        James Morse <james.morse@arm.com>,
        Quentin Perret <qperret@google.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Subject: RE: [PATCH 2/4] arm64: implement support for static call trampolines
Thread-Topic: [PATCH 2/4] arm64: implement support for static call trampolines
Thread-Index: AQHXylVlgIVfu8vswkCI9TVLTUwuCavlHODQ
Date:   Tue, 26 Oct 2021 11:06:11 +0000
Message-ID: <7d807624275a4938871f8e433e510e3c@AcuMS.aculab.com>
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From: Mark Rutland
> Sent: 26 October 2021 11:37
...
> My preference overall is to keep the trampoline self-contained, and I'd
> prefer to keep the RET inline in the trampoline rather than trying to
> factor it out so that all the control-flow is clearly in one place.
> 
> So I'd prefer that we have the sequence as-is:
> 
> | 0:	.quad 0x0
> | 	bti	c
> | 	< insn >
> | 	ldr	x16, 0b
> | 	cbz	x16, 1f
> | 	br	x16
> | 1:	ret

What is wrong with:
0:	.quad 1f
	bti	c
	< insn >
	ldr	x16, 0b
	br	x16
1:	bti	c
	ret

Self-contained and reasonably easy to read.

	David

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