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Date: Wed, 20 Mar 2024 19:42:44 +0000
From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Jiangfeng Xiao <xiaojiangfeng@huawei.com>
Cc: linus.walleij@linaro.org, arnd@arndb.de, keescook@chromium.org,
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	dave.hansen@linux.intel.com, douzhaolei@huawei.com,
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	David.Laight@aculab.com
Subject: Re: [PATCH v3] ARM: unwind: improve unwinders for noreturn case
Message-ID: <Zfs8NNlAwF3+LYZ/@shell.armlinux.org.uk>
References: <1709516385-7778-1-git-send-email-xiaojiangfeng@huawei.com>
 <1710949294-29287-1-git-send-email-xiaojiangfeng@huawei.com>
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Sender: Russell King (Oracle) <linux@armlinux.org.uk>

On Wed, Mar 20, 2024 at 11:41:34PM +0800, Jiangfeng Xiao wrote:
> This is an off-by-one bug which is common in unwinders,
> due to the fact that the address on the stack points
> to the return address rather than the call address.
> 
> So, for example, when the last instruction of a function
> is a function call (e.g., to a noreturn function), it can
> cause the unwinder to incorrectly try to unwind from
> the function after the callee.
> 
> foo:
> ...
>     bl      bar
> ... end of function and thus next function ...
> 
> which results in LR pointing into the next function.
> 
> Fixed this by subtracting 1 from frmae->pc in the call frame
> like ORC on x86 does.
> 
> Refer to the unwind_next_frame function in the unwind_orc.c

This came in while I was still replying to your previous reply, so
I'm going to ignore this. Please allow at least 24 hours between
postings, and please allow discussion to finish before posting a
new version - give your reviewers adequate time to compose a reply
bearing in mind that timezones might get in the way, but also making
supper (as is the case in this instance) may cause several hour delay
in reply.

Thanks.

-- 
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