Re: [PATCH RFC] x86: Fix XEN_DOMCTL_gdbsx_guestmemio crash

[Juergen Gross <jgross@xxxxxxxx>]

On 20.04.22 17:56, Andrew Cooper wrote:
> When CONFIG_GDBSX is compiled out, iommu_do_domctl() falls over a NULL
> pointer.  It isn't really correct for processing of XEN_DOMCTL_gdbsx_* to fall
> into the default case when compiled out.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
> CC: Julien Grall <julien@xxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
> CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
>
> RFC, because this has implications across the codebase.  The tl;dr is that
> case FOO:'s shouldn't be compiled out; we still know what the subops are, even
> when the functionality is compiled out.
>
> There are several ways to express this.  Alternatives would be:
>
>      case XEN_DOMCTL_gdbsx_guestmemio:
>          if ( !IS_ENABLED(CONFIG_GDBSX) )
>          {
>              rc = -EOPNOTSUPP;
>              break;
>          }
>          ...;
>
> but given my debugger series creating gdbsx.c, I was also considering:
>
>      case XEN_DOMCTL_gdbsx_guestmemio:
>      case XEN_DOMCTL_gdbsx_pausevcpu:
>      case XEN_DOMCTL_gdbsx_unpausevcpu:
>      case XEN_DOMCTL_gdbsx_domstatus:
>          rc = gdbsx_do_domctl(d, iop);
>          break;
I'd go this route.


Juergen

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