linux-kernel - Re: [PATCH] ARM: kprobes: Make __kretprobe

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Date:   Fri, 25 Mar 2022 00:18:31 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>, kbuild-all@...ts.01.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm
 function

Hi Ard,

On Thu, 24 Mar 2022 14:34:46 +0100
Ard Biesheuvel <ardb@...nel.org> wrote:

> --- a/arch/arm/probes/kprobes/core.c
> +++ b/arch/arm/probes/kprobes/core.c
> @@ -377,7 +377,7 @@ void __naked __kprobes __kretprobe_trampoline(void)
>  {
>         __asm__ __volatile__ (
>  #ifdef CONFIG_FRAME_POINTER
> -               "ldr    lr, =__kretprobe_trampoline     \n\t"
> +               "ldr    lr, .L__kretprobe_trampoline    \n\t"
>         /* __kretprobe_trampoline makes a framepointer on pt_regs. */
>  #ifdef CONFIG_CC_IS_CLANG
>                 "stmdb  sp, {sp, lr, pc}        \n\t"
> @@ -407,6 +407,11 @@ void __naked __kprobes __kretprobe_trampoline(void)
>                 "bx     lr                      \n\t"
>  #else
>                 "mov    pc, lr                  \n\t"
> +#endif
> +#ifdef CONFIG_FRAME_POINTER
> +               ".align 2                       \n\t"
> +       ".L__kretprobe_trampoline:              \n\t"
> +               ".long  __kretprobe_trampoline  \n\t"
>  #endif
>                 : : : "memory");
>  }

Yes, I confirmed this works too :-)

Can you send the patch with my Tested-by ?

Thank you!

> 
> 
> On Thu, 24 Mar 2022 at 14:23, Masami Hiramatsu <mhiramat@...nel.org> wrote:
> >
> > On Thu, 24 Mar 2022 15:21:08 +0900
> > Masami Hiramatsu <mhiramat@...nel.org> wrote:
> >
> > > Hi,
> > >
> > > I found a better solution for this issue from Ard :-)
> > >
> > > https://lore.kernel.org/all/20220203082204.1176734-6-ardb@kernel.org/T/#u
> > >
> > > I should use mov_l instead of ldr for loading the symbol address.
> >
> > Hm, these macros are only for the pure assembly file (.S), so we have to
> > split this in a asm file to use that.
> >
> 
> 
> What about the below?


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