linux-kernel - Re: arch/loongarch/kernel/alternative.o: warning: objtool: apply_alternatives+0xa0: unreachable instruction

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Message-ID: <a1871e00-936c-8487-a22a-efe3cc4c53a4@loongson.cn>
Date: Mon, 22 Jul 2024 16:57:35 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: kernel test robot <lkp@...el.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
 Huacai Chen <chenhuacai@...nel.org>, Jinyang He <hejinyang@...ngson.cn>,
 Youling Tang <tangyouling@...inos.cn>
Subject: Re: arch/loongarch/kernel/alternative.o: warning: objtool:
 apply_alternatives+0xa0: unreachable instruction

On 07/22/2024 12:38 PM, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   7846b618e0a4c3e08888099d1d4512722b39ca99
> commit: cb8a2ef0848ca80d67d6d56e2df757cfdf6b3355 LoongArch: Add ORC stack unwinder support
> date:   4 months ago
> config: loongarch-randconfig-001-20240722 (https://download.01.org/0day-ci/archive/20240722/202407221208.6SSBeN9H-lkp@intel.com/config)
> compiler: loongarch64-linux-gcc (GCC) 14.1.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240722/202407221208.6SSBeN9H-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202407221208.6SSBeN9H-lkp@intel.com/


A quick test shows that the objtool warnings are related with compiler
optimization level, it uses -Os (CONFIG_CC_OPTIMIZE_FOR_SIZE=y) rather
than the default -O2 (CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set)
in the randconfig. I will keep digging.

Thanks,
Tiezhu