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Date:   Thu, 13 Apr 2023 01:24:41 +0800
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Subject: Re: [PATCH 2/2] x86: make __get_wchan() use arch_stack_walk()
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To:     Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@kernel.org>
Cc:     keescook@chromium.org, dave.hansen@linux.intel.com, bp@alien8.de,
        mingo@redhat.com, tglx@linutronix.de, rostedt@goodmis.org,
        x86@kernel.org, linux-kernel@vger.kernel.org
References: <20230330081552.54178-1-zhengqi.arch@bytedance.com>
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 <20230412131533.GH628377@hirez.programming.kicks-ass.net>
 <20230412132327.GA629496@hirez.programming.kicks-ass.net>
From:   Qi Zheng <zhengqi.arch@bytedance.com>
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On 2023/4/12 21:23, Peter Zijlstra wrote:
> On Wed, Apr 12, 2023 at 03:15:33PM +0200, Peter Zijlstra wrote:
>> On Fri, Apr 07, 2023 at 10:08:22PM -0700, Josh Poimboeuf wrote:
>>> On Thu, Mar 30, 2023 at 04:15:52PM +0800, Qi Zheng wrote:
>>>> Make __get_wchan() use arch_stack_walk() directly to
>>>> avoid open-coding of unwind logic.
>>>>
>>>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>>>
>>> Can we just have a shared version of __get_wchan() for all
>>> CONFIG_ARCH_STACKWALK arches?
>>
>> Didn't I do that a while back ? I can't seem to actually find the
>> patch-set though :/
> 
> Could be this series:
> 
>    https://lkml.kernel.org/r/20211022150933.883959987@infradead.org

Oh, I vaguely remember the beginning because I was trying to fix
get_wchan() not supporting ORC unwinder on x86 [1], and then you sent a
patch set, and the patch [2] in this patch set tried to implement the
shared version of __get_wchan().

[1]. https://lore.kernel.org/all/20211008111626.271115116@infradead.org/
[2]. https://lore.kernel.org/all/20211008111626.392918519@infradead.org/

> 
> And this here:
> 
>    https://lore.kernel.org/lkml/CAHk-=wjHbKfck1Ws4Y0pUZ7bxdjU9eh2WK0EFsv65utfeVkT9Q@mail.gmail.com/
> 
> might be why I dropped it.. I can't remember.

Didn't realize I had replied to this email before.

But I also don't see why you dropped it. Looks like you have fixed the
UAF problem.

So do we still need to implement a shared version of __get_wchan()?
If we still need it, do I need to send it again? Or just pick your
previous patch directly? Both are fine to me. :)

Thanks,
Qi