linux-kernel - Re: [RESEND PATCH] ARM: Recover kretprobes return address for EABI stack unwinder

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Date:   Mon, 22 Aug 2022 13:20:32 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Chen Zhongjin <chenzhongjin@...wei.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux@...linux.org.uk, arnd@...db.de,
        ardb@...nel.org, rmk+kernel@...linux.org.uk, rostedt@...dmis.org,
        nick.hawkins@....com, john@...ozen.org, mhiramat@...nel.org
Subject: Re: [RESEND PATCH] ARM: Recover kretprobes return address for EABI
 stack unwinder

On Mon, Aug 15, 2022 at 1:06 PM Chen Zhongjin <chenzhongjin@...wei.com> wrote:

> 'fed240d9c974 ("ARM: Recover kretprobe modified return address in stacktrace")'
> has implemented kretprobes return address recovery for FP
> unwinder, this patch makes it works for EABI unwinder.
>
> It saves __kretprobe_trampoline address in LR on stack to identify
> and recover the correct return address in EABI unwinder.
>
> Since EABI doesn't use r11 as frame pointer, we need to use SP to
> identify different kretprobes addresses. Here the value of SP has fixed
> distance to conventional FP position so it's fine to use it.
>
> Passed kunit kprobes_test on QEMU.
>
> Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>

This looks correct to me FWIW I understand the assembly
but I'm vaguely unfamiliar with the kprobe API, but anyway:
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Would you please drop it into Russell's patch tracker?

Yours,
Linus Walleij