linux-kernel - Re: [BUG mips llvm] MIPS: malformed R_MIPS

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Date:   Tue, 12 Jan 2021 14:14:58 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Alexander Lobakin <alobakin@...me>
Cc:     Fangrui Song <maskray@...gle.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        linux-mips@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Ralf Baechle <ralf@...ux-mips.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [BUG mips llvm] MIPS: malformed R_MIPS_{HI16,LO16} with LLVM

On Mon, Jan 11, 2021 at 12:50 PM Alexander Lobakin <alobakin@...me> wrote:
>
> > The disassembly for me produces:
> >     399c: 3c 03 00 00   lui     $3, 0 <phy_device_free>
> >                         0000399c:  R_MIPS_HI16  .text
> > ...
> >     39a8: 24 63 3a 5c   addiu   $3, $3, 14940 <phy_probe>
> >                         000039a8:  R_MIPS_LO16  .text
>
> So, in your case the values of the instructions that relocs refer are:
>
> 0x3c030000 R_MIPS_HI16
> 0x24633a5c R_MIPS_LO16
>
> Mine were:
>
> 0x3c010000
> 0x24339444
>
> Your second one doesn't have bit 15 set, so I think this pair won't
> break the code.
> Try to hunt for R_MIPS_LO16 that have this bit set, i.e. they have
> '8', '9', 'a', 'b', 'c', 'd' or 'e' as their [15:12].

I don't think any of my R_MIPS_LO16 in that file have that bit set.
See attached.
-- 
Thanks,
~Nick Desaulniers

View attachment "drivers_net_phy_phy_device.objdump.txt" of type "text/plain" (6145 bytes)