Re: [Xen-devel] Problems with livepatching

[Lars Kurth <lars.kurth.xen@xxxxxxxxx>]

> On 24 Nov 2016, at 01:08, Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx> wrote:
> 
> On Thu, Nov 24, 2016 at 12:13:43AM +0000, M A Young wrote:
>> On Wed, 23 Nov 2016, Andrew Cooper wrote:
>> 
>>> On 23/11/2016 23:06, M A Young wrote:
>>>> I have been experimenting with live patching with the recent batch of 
>>>> security updates on Fedora xen with very limited success. I had most 
>>>> attempts with a test build of xen-4.8.0-rc6, and of the updates I have 
>>>> tried only xsa192.patch uploads successfully. For example with 
>>>> xsa191.patch the upload fails with the output
>>>> Uploading /tmp/xen-debuginfo/out1/xsa191.livepatch (1561400 bytes)
>>>> Upload failed: /tmp/xen-debuginfo/out1/xsa191.livepatch, error: 2(No such 
>>>> file or directory)!
>>>> and in xl dmesg a long debugging output ends with the line
>>>> (XEN) livepatch_elf.c:295: livepatch: xsa191: Unknown symbol: .LC0
>>>> with a similar line (mostly with .LC0 but with .LC3 in one case) for the 
>>>> other failed attempts. Am I doing something wrong or is there a problem 
>>>> with live patching in this case?
>>> 
>>> This looks like a problem generating the livepatch itself, not the
>>> livepatching mechanism.
>>> 
>>> Make sure you are completely up to date with the livepatch tools
>>> userspace.  There was one bug in livepatch generation which was
>>> discovered due to XSA-191 and fixed (actually a preexisting bug even in
>>> Linux), but its symptoms were innocuous until you patched, at which vcpu
>>> context switch blew up.
>> 
>> Where is this latest version available from? I had checked the git repo on 
>> xenbits 
>> http://xenbits.xenproject.org/gitweb/?p=livepatch-build-tools.git;a=summary 
>> but the last commit was 4 months ago.
> 
> Here is the patch that Ross has been working on - it is being first reviewed
> for merge in the upstream version of kpatch. Hence hasn't been posted. But
> posting it here.

I think the link is missing.
Lars
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