linux-kernel - Re: [PATCH] x86/ftrace: avoid an unused-function warning

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Message-ID: <CAK8P3a3DEA0nUupyNVmxp3fQ90sFj_R=FR3gXsDg_cSwg-BRrw@mail.gmail.com>
Date:   Tue, 5 Mar 2019 08:52:25 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/ftrace: avoid an unused-function warning

On Mon, Mar 4, 2019 at 10:43 PM Steven Rostedt <rostedt@...dmis.org> wrote:
> On Mon,  4 Mar 2019 21:07:39 +0100 Arnd Bergmann <arnd@...db.de> wrote:
...
> Also, it's basically identical to ftrace_call_replace(). I'm going to
> combine the two and move the jmp replace and have it do this instead.

Sounds good.

> arch/x86/kernel/ftrace.c:669:23: error: 'ftrace_jmp_replace' defined but not used [-Werror=unused-function]
>
> The ftrace_jmp_replace() function now only has a single user and should be
> simply moved by that user. But looking at the code, it shows that
> ftrace_jmp_replace() is similar to ftrace_call_replace() except that instead
> of using the opcode of 0xe8 it uses 0xe9. It makes more sense to consolidate
> that function into one implementation that both ftrace_jmp_replace() and
> ftrace_call_replace() use by passing in the op code separate.
>
> The structure in ftrace_code_union is also modified to replace the "e8"
> field with the more appropriate name "op".
>
> Cc: stable@...r.kernel.org
> Reported-by: Arnd Bergmann <arnd@...db.de>
> Link: http://lkml.kernel.org/r/20190304200748.1418790-1-arnd@arndb.de
> Fixes: d2a68c4effd8 ("x86/ftrace: Do not call function graph from dynamic trampolines")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

Acked-by: Arnd Bergmann <arnd@...db.de>