linux-kernel - Re: [PATCH v1] LoongArch: Remove unnecessary checks in bt

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Message-ID: <ba1494da-a407-3acb-a5d1-8fbd9498b6c6@loongson.cn>
Date: Wed, 10 Dec 2025 10:25:54 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>, Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] LoongArch: Remove unnecessary checks in bt_address()



On 2025/12/10 上午9:28, Tiezhu Yang wrote:
> On 2025/12/9 下午4:30, Huacai Chen wrote:
>> Hi, Tiezhu,
>>
>> On Tue, Dec 9, 2025 at 2:18 PM Tiezhu Yang <yangtiezhu@...ngson.cn> 
>> wrote:
>>>
> ...
>>>          extern unsigned long eentry;
>>>
>>> -       if (__kernel_text_address(ra))
>>> -               return ra;
>>> -
>>> -       if (__module_text_address(ra))
>>> -               return ra;
>> I think the correct way is to remove the __module_text_address()
>> condition but keep the __kernel_text_address() condition. Then return
>> 0 at the end of this function, and remove the __kernel_text_address()
>> condition out of this function.
> 
> It can not remove the check of __kernel_text_address() after calling
> bt_address() because it needs to validate the calculated address for
> exception, then no need to keep the __kernel_text_address() condition
> in bt_address() because it will check the PC outside bt_address().
         state->pc = bt_address(pc);
         if (!state->pc) {
                 pr_err("cannot find unwind pc at %p\n", (void *)pc);
                 goto err;
         }

         if (!__kernel_text_address(state->pc))
                 goto err;
I guess that you both comes from different views :) one treats these 
piece of code into one, one only views function bt_address().

Especially with if (!state->pc), how could this happen?

Regards
Bibo Mao

> 
> Thanks,
> Tiezhu
>