linux-kernel - Re: [PATCH -tip v8 03/13] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline

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Message-ID: <YOK5jnkaqNCMQkJi@gmail.com>
Date:   Mon, 5 Jul 2021 09:49:34 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, X86 ML <x86@...nel.org>,
        Daniel Xu <dxu@...uu.xyz>, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, kuba@...nel.org, mingo@...hat.com,
        ast@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>, kernel-team@...com,
        yhs@...com, linux-ia64@...r.kernel.org,
        Abhishek Sagar <sagar.abhishek@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>
Subject: Re: [PATCH -tip v8 03/13] kprobes: treewide: Remove
 trampoline_address from kretprobe_trampoline_handler()


* Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Remove trampoline_address from kretprobe_trampoline_handler().
> Instead of passing the address, kretprobe_trampoline_handler()
> can use new kretprobe_trampoline_addr().
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Tested-by: Andrii Nakryik <andrii@...nel.org>

A better changelog:

   The __kretprobe_trampoline_handler() callback, called from low level 
   arch kprobes methods, has the 'trampoline_address' parameter, which is 
   entirely superfluous as it basically just replicates:

        dereference_kernel_function_descriptor(kretprobe_trampoline)

   In fact we had bugs in arch code where it wasn't replicated correctly.

   So remove this superfluous parameter and use kretprobe_trampoline_addr() 
   instead.

Thanks,

	Ingo