linux-kernel - Re: [PATCH v4 8/8] LoongArch: Add ORC stack unwinder support

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Date:   Mon, 23 Oct 2023 17:21:38 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Xi Ruoyao <xry111@...111.site>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Huacai Chen <chenhuacai@...nel.org>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v4 8/8] LoongArch: Add ORC stack unwinder support

On 10/23/2023 04:43 PM, Xi Ruoyao wrote:
> On Mon, 2023-10-23 at 16:11 +0800, Tiezhu Yang wrote:
>> +ifdef CONFIG_OBJTOOL
>> +KBUILD_CFLAGS			+= -fno-optimize-sibling-calls -fno-jump-tables -falign-functions=4
>> +endif
>
> Why do we need to regress the code generation so much for objtool?

Add the above options is to avoid generating some intractable
instructions for objtool by now, I hope all of the extra options
can be removed if possible.

For example, without -fno-jump-tables, there exist many objtool
warnings like this:

"sibling call from callable instruction with modified stack frame"

If the enhanced special function about jump table is implemented
in objtool, -fno-jump-tables will be removed in the future.

Thanks,
Tiezhu