linux-kernel - Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

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: <3069bb9c-6245-4754-a187-ac8253103d32@oracle.com>
Date: Thu, 13 Feb 2025 15:22:47 -0800
From: Indu Bhagat <indu.bhagat@...cle.com>
To: Song Liu <song@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Weinan Liu <wnliu@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>, roman.gushchin@...ux.dev,
        Will Deacon <will@...nel.org>, Ian Rogers <irogers@...gle.com>,
        linux-toolchains@...r.kernel.org, linux-kernel@...r.kernel.org,
        live-patching@...r.kernel.org, joe.lawrence@...hat.com,
        linux-arm-kernel@...ts.infradead.org,
        Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

On 2/12/25 11:25 PM, Song Liu wrote:
> On Wed, Feb 12, 2025 at 6:45 PM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>>
>> On Wed, Feb 12, 2025 at 06:36:04PM -0800, Song Liu wrote:
>>>>> [   81.261748]  copy_process+0xfdc/0xfd58 [livepatch_special_static]
>>>>
>>>> Does that copy_process+0xfdc/0xfd58 resolve to this line in
>>>> copy_process()?
>>>>
>>>>                          refcount_inc(&current->signal->sigcnt);
>>>>
>>>> Maybe the klp rela reference to 'current' is bogus, or resolving to the
>>>> wrong address somehow?
>>>
>>> It resolves the following line.
>>>
>>> p->signal->tty = tty_kref_get(current->signal->tty);
>>>
>>> I am not quite sure how 'current' should be resolved.
>>
>> Hm, on arm64 it looks like the value of 'current' is stored in the
>> SP_EL0 register.  So I guess that shouldn't need any relocations.
>>
>>> The size of copy_process (0xfd58) is wrong. It is only about
>>> 5.5kB in size. Also, the copy_process function in the .ko file
>>> looks very broken. I will try a few more things.
> 
> When I try each step of kpatch-build, the copy_process function
> looks reasonable (according to gdb-disassemble) in fork.o and
> output.o. However, copy_process looks weird in livepatch-special-static.o,
> which is generated by ld:
> 
> ld -EL  -maarch64linux -z norelro -z noexecstack
> --no-warn-rwx-segments -T ././kpatch.lds  -r -o
> livepatch-special-static.o ./patch-hook.o ./output.o
> 
> I have attached these files to the email. I am not sure whether
> the email server will let them through.
> 
> Indu, does this look like an issue with ld?
> 

Sorry for the delay.

Looks like there has been progress since and issue may be elsewhere, but:

FWIW, I looked at the .sframe and .rela.sframe sections here, the data 
does look OK.  I noted that there is no .sframe for copy_process () in 
output.o... I will take a look into it.