linux-kernel - Re: [PATCH] x86: livepatch: Treat R_X86_64_PLT32 as R_X86_64

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Date:   Mon, 18 Feb 2019 13:29:11 +0800
From:   "chengjian (D)" <cj.chengjian@...wei.com>
To:     Jiri Kosina <jikos@...nel.org>,
        "chenzefeng (A)" <chenzefeng2@...wei.com>
CC:     "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "sjenning@...hat.com" <sjenning@...hat.com>,
        "vojtech@...e.com" <vojtech@...e.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Xiexiuqi (Xie XiuQi)" <xiexiuqi@...wei.com>
Subject: Re: [PATCH] x86: livepatch: Treat R_X86_64_PLT32 as R_X86_64_PC32

Hi，Jiri


This patch should be merged into 4.4 stable,

which still use klp_write_module_reloc.


https://elixir.bootlin.com/linux/v4.4.174/source/arch/x86/kernel/livepatch.c


ZeFeng may have sent a stable(4.4-y) patch to the wrong mail-list(mainline).


Thanks.

On 2019/2/15 15:28, Jiri Kosina wrote:
> On Fri, 15 Feb 2019, chenzefeng (A) wrote:
>
>> On x86-64, for 32-bit PC-relacive branches, we can generate PLT32
>> relocation, instead of PC32 relocation. and R_X86_64_PLT32 can be
>> treated the same as R_X86_64_PC32 since linux kernel doesn't use PLT.
>>
>> In linux 4.4 commit b21ebf2fb4cd ("x86: Treat R_X86_64_PLT32 as
>> R_X86_64_PC32") been fixed for the module loading, but not fixed for
>> livepatch relocation, which will fail to load livepatch with the error
>> message as follow: relocation failed for symbol <symbol name> at <symbol
>> address>
>>
>> Signed-off-by: chenzefeng <chenzefeng2@...wei.com>
> What kernel version is this patch based on? We've got rid of x86-specific
> module loading stub and offloaded all the relocation handling to generic
> kmod loader long time ago.
>