[Xen-devel] livepatch-build: What does getting no output from "readelf -wi xen-syms" usually mean?

[Andy Smith <andy@xxxxxxxxxxxxxx>]

Hi,

I've been looking into live patching for the first time.

Starting with a 4.12.1 build:

$ cd ~/dev
$ ls -l
total 8
drwxr-xr-x 3 andy andy 4096 Oct 25 16:11 xen
drwxr-xr-x 6 andy andy 4096 Dec  2 01:16 livepatch-build-tools

(there is already a 4.12.1 hypervisor built in /xen and is what's
running on this host with build_id
b18af774b56b0c98cfa6940a725ba2ba26066929)

$ cp -a xen xen-lptest
$ cd livepatch-build-tools
$ ./livepatch-build -j 1 -s /home/andy/dev/xen-lptest/xen-4.12.1 -c 
/home/andy/dev/xen-lptest/xen-4.12.1/xen/.config -p ./lptest.patch -o lptest -d 
--depends b18af774b56b0c98cfa6940a725ba2ba26066929
Building LivePatch patch: lptest

Xen directory: /home/andy/dev/xen-lptest/xen-4.12.1
Patch file: /home/andy/dev/livepatch-build-tools/lptest.patch
.config file: /home/andy/dev/xen-lptest/xen-4.12.1/xen/.config
Output directory: /home/andy/dev/livepatch-build-tools/xsa310
================================================

Perform full initial build with 1 CPU(s)...
Reading special section data
ERROR: can't find special struct size.

So it seems it completed the initial build without error but looking
at the livepatch-build script it runs readelf like this:

$ readelf -wi lptest/xen-syms
$

For me this produces no output. I've probably done something simple
wrong. Does that indicate some simple mistake in my process?

The patch was just a trivial addition of some logging as a test, but
I don't think it got as far as applying that.

$ readelf --version
GNU readelf (GNU Binutils for Debian) 2.31.1
Copyright (C) 2018 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) any later version.
This program has absolutely no warranty.
$ gcc --version
gcc (Debian 8.3.0-6) 8.3.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Thanks,
Andy

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