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

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Date:   Mon, 22 Aug 2022 22:43:09 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     Linus Walleij <linus.walleij@...aro.org>
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 2022/8/22 19:20, Linus Walleij wrote:
> 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?

Done for it.

Thanks for review!


Best,

Chen

> Yours,
> Linus Walleij