linux-kernel - Re: [PATCH -next 1/3] arm64: efi-header: Mark efi header as data

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Message-ID: <71274d7a-8a79-3954-d462-5cc8b5a5e874@huawei.com>
Date:   Thu, 22 Sep 2022 22:25:31 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     Ard Biesheuvel <ardb@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <herbert@...dor.apana.org.au>, <davem@...emloft.net>,
        <catalin.marinas@....com>, <will@...nel.org>, <broonie@...nel.org>,
        <maz@...nel.org>, <mark.rutland@....com>,
        <anshuman.khandual@....com>
Subject: Re: [PATCH -next 1/3] arm64: efi-header: Mark efi header as data

Hi,

On 2022/9/22 21:13, Ard Biesheuvel wrote:
> On Thu, 22 Sept 2022 at 15:08, Chen Zhongjin <chenzhongjin@...wei.com> wrote:
>> This file only contains a set of constants forming the efi header.
>>
>> Make the constants part of data symbols by wrapping them with
>> SYM_DATA.
>>
>> Signed-off-by: Julien Thierry <jthierry@...hat.com>
>> Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
>> Reviewed-by: Mark Brown <broonie@...nel.org>
> Why is this necessary? These are not emitted into a .text section, and
> are not even covered by the kernel's mapping of memory. So the .L
> prefixed labels are deliberate: it prevents the symbols from polluting
> the symbol namespace with symbols pointing nowhere.
>
This is basically because when I'm developing objtool and these 
constants will disrupts

the instruction decoding so I just mark them as x86 did.


I tried to sent this patch set is because now the objtool patch set is 
growing huge so I

want to split some independent part. But now I found you are right that 
this are

meaningless. They are not even inside vmlinux. I'll discard them.


Sorry for bothering and thanks for your advise and patient!

Best,

Chen

>> ---
>>   arch/arm64/kernel/efi-header.S | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S
>> index 28d8a5dca5f1..3eacd27ab761 100644
>> --- a/arch/arm64/kernel/efi-header.S
>> +++ b/arch/arm64/kernel/efi-header.S
>> @@ -28,6 +28,7 @@
>>          .macro  __EFI_PE_HEADER
>>   #ifdef CONFIG_EFI
>>          .set    .Lpe_header_offset, . - .L_head
>> +SYM_DATA_START_LOCAL(arm64_efi_header)
>>          .long   PE_MAGIC
>>          .short  IMAGE_FILE_MACHINE_ARM64                // Machine
>>          .short  .Lsection_count                         // NumberOfSections
>> @@ -160,6 +161,7 @@
>>
>>          .balign SEGMENT_ALIGN
>>   .Lefi_header_end:
>> +SYM_DATA_END_LABEL(arm64_efi_header, SYM_L_LOCAL, efi_header_end)
>>   #else
>>          .set    .Lpe_header_offset, 0x0
>>   #endif
>> --
>> 2.17.1
>>