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Date:   Mon, 4 Nov 2019 13:51:56 +0000
From:   Mark Rutland <mark.rutland@arm.com>
To:     Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        catalin.marinas@arm.com, deller@gmx.de, duwe@suse.de,
        James.Bottomley@HansenPartnership.com, james.morse@arm.com,
        jeyu@kernel.org, jpoimboe@redhat.com, jthierry@redhat.com,
        linux-parisc@vger.kernel.org, mingo@redhat.com,
        peterz@infradead.org, rostedt@goodmis.org, svens@stackframe.org,
        takahiro.akashi@linaro.org, will@kernel.org,
        Torsten Duwe <duwe@lst.de>
Subject: Re: [PATCHv2 7/8] arm64: implement ftrace with regs
Message-ID: <20191104135155.GG45140@lakrids.cambridge.arm.com>
References: <20191029165832.33606-1-mark.rutland@arm.com>
 <20191029165832.33606-8-mark.rutland@arm.com>
 <8132dc13-9fbd-24e2-8a5e-28b005043c3e@arm.com>
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On Sat, Nov 02, 2019 at 05:51:46PM +0530, Amit Daniel Kachhap wrote:
> On 10/29/19 10:28 PM, Mark Rutland wrote:
> > +/*
> > + * Due to -fpatchable-function-entry=2, the compiler has placed two NOPs before
> > + * the regular function prologue. For an enabled callsite, ftrace_init_nop() and
> > + * ftrace_make_call() have patched those NOPs to:
> > + *
> > + * 	MOV	X9, LR
> > + * 	BL	<entry>
> > + *
> > + * ... where <entry> is either ftrace_caller or ftrace_regs_caller.
> > + *
> > + * Each instrumented function follows the AAPCS, so here x0-x8 and x19-x30 are
> > + * live, and x9-x18 are safe to clobber.
> > + *
> > + * We save the callsite's context into a pt_regs before invoking and ftrace

> s/invoking and ftrace callbacks/invoking the ftrace callbacks

Whoops, that was meant to be 'any'. I've fixed that up locally.

Thanks,
Mark.