Re: [Xen-devel] [PATCH v5 15/28] xsplice: Add .xsplice.hooks functions and test-case

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 04/08/2016 06:39 PM, Jan Beulich wrote:
> > > > On 08.04.16 at 17:57, <ross.lagerwall@xxxxxxxxxx> wrote:
> > On 04/07/2016 02:15 AM, Jan Beulich wrote:
> > > > > > Martin Pohlack <mpohlack@xxxxxxxxxx> 04/06/16 8:42 AM >>>
> > > > On 06.04.2016 04:42, Konrad Rzeszutek Wilk wrote:
> > > > > The normal use-case is to modify structures values where we have to
> > > > > be delicate about it and can't just replace the value. As in we
> > > > > may have to recompute the value.
> > > > Agree on the default use (e.g., for XSA 91).
> > > XSA-91 was an ARM one, i.e. would still only be a theoretical example for
> > > the purpose of the discussion here.
> > I've marked the following XSAs as potentially requiring hook functions
> > or shadow variables:
> >
> > XSA-36
> > XSA-45
> > XSA-60
> > XSA-64
> > XSA-80
> > XSA-82
> > XSA-97
> > XSA-107
> > XSA-114
> > XSA-150
> Such a raw list doesn't tell me anything, I'm afraid. Can you please
> explain for at least one of them why they do need hooks (and not
> just potentially)?
Some examples:
XSA-80: In addition to patching the code, a hook function is needed to 
set iommu_dont_flush_iotlb back to 0.
XSA-82: The original patch applies to an __init function. Instead, use a 
hook function to update the MSR.
Of course, it requires someone with decent knowledge of the code area & 
source patch to determine exactly what needs to be done. But any patch 
which touches initialization code (__init or otherwise) or changes the 
layout or content of data (structs or static/global data) will either 
need the source patch to be rewritten and/or the use of hook 
functions/shadow variables. The XSAs I've listed above fall into this 
category.
--
Ross Lagerwall

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