linux-kernel - Re: [RFC PATCH 2/2] objtool/LoongArch: Fix unreachable instruction warnings about head.S

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Message-ID: <b7551efd-cb5b-7503-c455-b8f22fac81bd@loongson.cn>
Date: Tue, 26 Aug 2025 20:30:23 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Nathan Chancellor
 <nathan@...nel.org>, loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] objtool/LoongArch: Fix unreachable instruction
 warnings about head.S

On 2025/8/26 下午4:26, Huacai Chen wrote:
> On Tue, Aug 26, 2025 at 2:46 PM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>>
>> When compiling with LLVM and CONFIG_LTO_CLANG is set, there exist the
>> following objtool warnings after silencing all of the other warnings:

...

>>   arch/loongarch/kernel/head.S | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
>> index e3865e92a917..566a1dbf5fa0 100644
>> --- a/arch/loongarch/kernel/head.S
>> +++ b/arch/loongarch/kernel/head.S
>> @@ -20,6 +20,7 @@
>>          __HEAD
>>
>>   _head:
>> +       UNWIND_HINT_UNDEFINED
>>          .word   IMAGE_DOS_SIGNATURE     /* "MZ", MS-DOS header */
>>          .org    0x8
>>          .dword  _kernel_entry           /* Kernel entry point (physical address) */
>> @@ -30,6 +31,7 @@ _head:
>>          .long   pe_header - _head       /* Offset to the PE header */
>>
>>   pe_header:
>> +       UNWIND_HINT_UNDEFINED
>>          __EFI_PE_HEADER
> The efi header is completely not code, the annotations are very strange.

Yes, I think so too, but the aim is only to not checking for objtool,
it seems no other better way.

Thanks,
Tiezhu