Re: [PATCH 3/8] arm64: kprobes: Record frame pointer with kretprobe instance

[Will Deacon]

On Fri, Oct 08, 2021 at 09:28:39PM +0900, Masami Hiramatsu wrote:
> Record the frame pointer instead of stack address with kretprobe
> instance as the identifier on the instance list.
> Since arm64 always enable CONFIG_FRAME_POINTER, we can use the
> actual frame pointer (x29).
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> ---
>  arch/arm64/kernel/probes/kprobes.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
> index e7ad6da980e8..d9dfa82c1f18 100644
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -401,14 +401,14 @@ int __init arch_populate_kprobe_blacklist(void)
>  
>  void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
>  {
> -	return (void *)kretprobe_trampoline_handler(regs, (void *)kernel_stack_pointer(regs));
> +	return (void *)kretprobe_trampoline_handler(regs, (void *)regs->regs[29]);
>  }
>  
>  void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
>  				      struct pt_regs *regs)
>  {
>  	ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
> -	ri->fp = (void *)kernel_stack_pointer(regs);
> +	ri->fp = (void *)regs->regs[29];
>  
>  	/* replace return addr (x30) with trampoline */
>  	regs->regs[30] = (long)&__kretprobe_trampoline;

Acked-by: Will Deacon <will@xxxxxxxxxx>

Will