Re: [Xen-devel] [PATCH v3 4/4] xen: use SYMBOL everywhere

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 12 Nov 2018, Julien Grall wrote:
> Hi Stefano,
> 
> On 11/8/18 10:27 PM, Stefano Stabellini wrote:
> > On Thu, 8 Nov 2018, Jan Beulich wrote:
> > > > > > On 06.11.18 at 23:05, <sstabellini@xxxxxxxxxx> wrote:
> > > > Use SYMBOL everywhere _stext, _etext, etc. are used. Technically, it
> > > > is required when comparing and subtracting pointers [1], but use it
> > > > everywhere to avoid confusion.
> > > 
> > > I think using it when not needed is causing more confusion. Also
> > > why would you then not use it on all other data symbols? The
> > > patch will end up quite a bit more reasonable in size once you drop
> > > the unnecessary changes.
> > 
> > OK, I am happy to do that. It will probably be better that way.
> > 
> > 
> > > > ---
> > > >   xen/arch/arm/alternative.c          |  7 ++--
> > > >   xen/arch/arm/arm32/livepatch.c      |  2 +-
> > > >   xen/arch/arm/arm64/livepatch.c      |  2 +-
> > > >   xen/arch/arm/domain_build.c         |  2 +-
> > > >   xen/arch/arm/livepatch.c            |  6 +--
> > > >   xen/arch/arm/mm.c                   | 17 ++++----
> > > >   xen/arch/arm/setup.c                |  8 ++--
> > > >   xen/arch/x86/setup.c                | 79
> > > > +++++++++++++++++++------------------
> > > >   xen/arch/x86/tboot.c                | 12 +++---
> > > >   xen/arch/x86/x86_64/machine_kexec.c |  4 +-
> > > >   xen/drivers/vpci/vpci.c             |  7 +++-
> > > >   xen/include/asm-arm/grant_table.h   |  3 +-
> > > >   xen/include/asm-arm/mm.h            |  4 +-
> > > >   xen/include/asm-x86/mm.h            |  4 +-
> > > >   xen/include/xen/kernel.h            | 24 +++++------
> > > >   15 files changed, 97 insertions(+), 84 deletions(-)
> > > 
> > > Just like for v2: Did you really check you caught them all? The vPCI
> > > ones I had pointed at back then were only an example. Another
> > > example now is xen/common/kernel.c:_cmdline_parse().
> > 
> > It is difficult to catch them all. Any suggestion on how to make sure
> > there are no leftover (other than waiting for the next QAVerify scan)?
> 
> The webpage [1] seems to suggest coverity would be able to catch the undefined
> behavior fixed in that patch.
> 
> I am not sure what version of coverity is used to analyze Xen, but it probably
> worth to have a try.
> 
> Cheers,
> 
> [1]
> https://wiki.sei.cmu.edu/confluence/display/c/ARR36-C.+Do+not+subtract+or+compare+two+pointers+that+do+not+refer+to+the+same+array

To do this, I would need to be able to create a special branch with my
fixes for Coverity to use. However, I don't have "write access" to any
Xen Project Coverity instances at the moment.

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