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Re: [PATCH 1/2] livepatch: do not ignore sections with 0 size
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- Date: Thu, 17 Mar 2022 14:00:19 +0000
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- Thread-topic: [PATCH 1/2] livepatch: do not ignore sections with 0 size
On 17/03/2022 11:08, Roger Pau Monne wrote:
> A side effect of ignoring such sections is that symbols belonging to
> them won't be resolved, and that could make relocations belonging to
> other sections that reference those symbols fail.
>
> For example it's likely to have an empty .altinstr_replacement with
> symbols pointing to it, and marking the section as ignored will
> prevent the symbols from being resolved, which in turn will cause any
> relocations against them to fail.
I agree this is a bug in livepatch handling, but it's also an error in
the generated livepatch. We should not have relocations to an empty
altinstr_replacement section in the first place.
This will probably be from the lfences, where the replacement in a nop
and takes no space. I think I know how to fix this case.
~Andrew
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