linux-kernel - Re: [PATCH v4 01/10] objtool: Handle various symbol types of rodata

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <fd86460f-f595-e7c3-0962-aab3124b0375@loongson.cn>
Date: Thu, 28 Nov 2024 10:26:54 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Huacai Chen <chenhuacai@...nel.org>, Peter Zijlstra
 <peterz@...radead.org>, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 01/10] objtool: Handle various symbol types of rodata

On 11/28/2024 02:53 AM, Josh Poimboeuf wrote:
> On Wed, Nov 27, 2024 at 02:39:13PM +0800, Tiezhu Yang wrote:
>> On 11/27/2024 08:52 AM, Josh Poimboeuf wrote:
>>> On Tue, Nov 26, 2024 at 06:41:29PM +0800, Tiezhu Yang wrote:
>>>> On 11/26/2024 02:44 PM, Josh Poimboeuf wrote:
>>>>> On Fri, Nov 22, 2024 at 12:49:56PM +0800, Tiezhu Yang wrote:
>>>>>> @@ -2094,12 +2095,19 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
>>>>>
>>>>> 'prev_offset' needs to be updated as well.
>>>>
>>>> I am not sure I understand your comment correctly, I can not see
>>>> what should to do about 'prev_offset'.
>>>
>>> Further down the function there is
>>>
>>>   prev_offset = reloc_offset(reloc);
>>>
>>> which needs to be changed to
>>>
>>>   prev_offset = offset;
>>>
>>> as part of the patch.
>>
>> If I understand correctly, reloc_offset(reloc) is different with
>> reloc->sym->offset + reloc_addend(reloc), tested on x86 and readelf
>> shows that their values are different, reloc_offset(reloc) is the
>> first column of .rela.rodata, reloc->sym->offset is the second to
>> last column of .rela.rodata, reloc_addend(reloc) is the last column
>> of .rela.rodata.
>>
>> If do the above change as you suggested, there will be some objtool
>> warnings on x86. I think it should be:
>>
>>   prev_offset = reloc_offset(reloc);
>>
>> rather than:
>>
>>   prev_offset = offset;
>>
>> That is to say, no need to change "prev_offset".
>> Could you please check it again, please let me know if I am wrong.
>
> Sorry, I was confused by the fact there are two different meanings for
> "offset": one for where the relocation is written, and one for the
> symbol it refers to.
>
> How about instead of 'offset', call it 'sym_offset'?

OK, looks better, will modify it in the next version.