Re: [Xen-devel] [livepatch-build-tools part3 1/3] create-diff-object: Do not create empty .livepatch.funcs section

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 4/25/19 5:51 AM, Konrad Rzeszutek Wilk wrote:
> On Tue, Apr 16, 2019 at 12:22:39PM +0000, Pawel Wieczorkiewicz wrote:
> > When there is no changed function in the generated payload, do not
> > create an empty .livepatch.funcs section. Hypervisor code considers
> > such payloads as broken and rejects to load them.
> >
> > Such payloads without any changed functions may appear when only
> > hooks are specified.
> Ross, I am going to push this in next week unless you have other thoughts?
Reviewed-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

This code change looks OK to me. However:

1) I think that the hypervisor should treat an empty .livepatch.funcs 
section the same as it treats a non-present .livepatch.funcs section 
(i.e. it allows it) which would make this change unnecessary.
2) Unless I'm being stupid, I don't see how this change would work 
anyway. Surely this code at the start of prepare_payload() would fail if 
the section were missing?
    sec = livepatch_elf_sec_by_name(elf, ELF_LIVEPATCH_FUNC);
    ASSERT(sec);
    if ( !section_ok(elf, sec, sizeof(*payload->funcs)) )
        return -EINVAL;

Regards,
--
Ross Lagerwall

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