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Date:   Wed, 25 May 2022 09:43:07 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Masami Hiramatsu <mhiramat@kernel.org>,
        Wang ShaoBo <bobo.shaobowang@huawei.com>,
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        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        catalin.marinas@arm.com, will@kernel.org, zengshun.wu@outlook.com,
        Jiri Olsa <jolsa@kernel.org>
Subject: Re: [RFC PATCH -next v2 3/4] arm64/ftrace: support dynamically
 allocated trampolines
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On Wed, 25 May 2022 13:17:30 +0100
Mark Rutland <mark.rutland@arm.com> wrote:

> For arm64 I'd like to make this static, and have ftrace *always* capture a
> minimal set of ftrace_regs, which would be:
> 
>   X0 to X8 inclusive
>   SP
>   PC
>   LR
>   FP
> 
> Since X0 to X8 + SP is all that we need for arguments and return values (per
> the calling convention we use), and PC+LR+FP gives us everything we need for
> unwinding and live patching.
> 
> I *might* want to add x18 to that when SCS is enabled, but I'm not immediately
> sure.

Does arm64 have HAVE_DYNAMIC_FTRACE_WITH_ARGS enabled? If so, then having
the normal ftrace call back save the above so that all functions have it
available would be useful.

-- Steve