linux-kernel - Purgatory compile flag changes apparently causing Kexec relocation overflows

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Message-ID: <20190828194226.GA29967@swahl-linux>
Date:   Wed, 28 Aug 2019 14:42:26 -0500
From:   Steve Wahl <steve.wahl@....com>
To:     linux-kernel@...r.kernel.org
Cc:     ndesaulniers@...gle.com, tglx@...utronix.de, steve.wahl@....com,
        russ.anderson@....com, dimitri.sivanich@....com,
        mike.travis@....com
Subject: Purgatory compile flag changes apparently causing Kexec relocation
 overflows

Please CC me on responses to this.

I normally would do more diligence on this, but the timing is such
that I think it's better to get this out sooner.

With the tip of the tree from https://github.com/torvalds/linux.git (a
few days old, most recent commit fetched is
bb7ba8069de933d69cb45dd0a5806b61033796a3), I'm seeing "kexec: Overflow
in relocation type 11 value 0x11fffd000" when I try to load a crash
kernel with kdump. This seems to be caused by commit
059f801a937d164e03b33c1848bb3dca67c0b04, which changed the compiler
flags used to compile purgatory.ro, apparently creating 32 bit
relocations for things that aren't necessarily reachable with a 32 bit
reference.  My guess is this only occurs when the crash kernel is
located outside 32-bit addressable physical space.

I have so far verified that the problem occurs with that commit, and
does not occur with the previous commit.  For this commit, Thomas
Gleixner mentioned a few of the changed flags should have been looked
at twice.  I have not gone so far as to figure out which flags cause
the problem.

The hardware in use is a HPE Superdome Flex with 48 * 32GiB dimms
(total 1536 GiB).

One example of the exact error messages seen:

019-08-28T13:42:39.308110-05:00 uv4test14 kernel: [   45.137743] kexec: Overflow in relocation type 11 value 0x17f7affd000
2019-08-28T13:42:39.308123-05:00 uv4test14 kernel: [   45.137749] kexec-bzImage64: Loading purgatory failed

--> Steve Wahl
--
Steve Wahl,  Hewlett Packard Enterprise