linux-kernel - Re: [PATCH v1 1/3] objtool/LoongArch: Fix fall through warning about efi_boot

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Message-ID: <75cae289-8717-85e7-1d86-a2736010d99c@loongson.cn>
Date: Fri, 5 Sep 2025 17:53:13 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
 Nathan Chancellor <nathan@...nel.org>, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/3] objtool/LoongArch: Fix fall through warning about
 efi_boot_kernel()

Hi Josh,

On 2025/9/5 下午12:33, Huacai Chen wrote:
> Hi, Josh,
> 
> On Fri, Sep 5, 2025 at 1:26 AM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>>
>> On Thu, Sep 04, 2025 at 10:17:11AM +0800, Huacai Chen wrote:

...

>> Is there some technical reason why vmlinux.o needs efistub linked in?
> I think so. For example, EFISTUB prefer to directly use screen_info
> that defined in vmlinux, see the comments in
> drivers/firmware/efi/libstub/screen_info.c:
> 
> /*
>   * There are two ways of populating the core kernel's struct
> screen_info via the stub:
>   * - using a configuration table, like below, which relies on the EFI init code
>   *   to locate the table and copy the contents;
>   * - by linking directly to the core kernel's copy of the global symbol.
>   *
>   * The latter is preferred because it makes the EFIFB earlycon available very
>   * early, but it only works if the EFI stub is part of the core kernel image
>   * itself. The zboot decompressor can only use the configuration table
>   * approach.
>   */

I wonder what is the final conclusion.

(1) For patch #1 and #2, keep the code as is and just update
the commit message.

(2) For patch #3, replace UNWIND_HINT_UNDEFINED with
UNWIND_HINT_END_OF_STACK and remove is_entry_func().

If there are any more comments, please let me know.

Thanks,
Tiezhu