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

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Date:   Mon, 5 Jul 2021 19:03:28 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ingo Molnar <mingo@...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()

Hi Ingo,

On Mon, 5 Jul 2021 09:03:19 +0200
Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > --- a/include/linux/kprobes.h
> > +++ b/include/linux/kprobes.h
> > @@ -197,15 +197,23 @@ extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
> >  				   struct pt_regs *regs);
> >  extern int arch_trampoline_kprobe(struct kprobe *p);
> >  
> > +void kretprobe_trampoline(void);
> > +/*
> > + * Since some architecture uses structured function pointer,
> > + * use dereference_function_descriptor() to get real function address.
> > + */
> > +static nokprobe_inline void *kretprobe_trampoline_addr(void)
> > +{
> > +	return dereference_kernel_function_descriptor(kretprobe_trampoline);
> > +}
> 
> Could we please also make 'kretprobe_trampoline' harder to use 
> accidentally, such by naming it appropriately?
> 
> __kretprobe_trampoline would be a good first step I guess.

Good idea! Let me update it.

Thank you,



-- 
Masami Hiramatsu <mhiramat@...nel.org>