Re: [PATCH v2] xen/dt-overlay: support phandle-based targeting in overlay_get_nodes_info

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 2026-04-28 12:22, Orzel, Michal wrote:
> On 28-Apr-26 10:20, Nicola Vetrini wrote:
> > On 2026-04-28 10:02, Michal Orzel wrote:
> > > overlay_get_nodes_info() is called before fdt_overlay_apply() to
> > > extract
> > > target paths from the overlay. This fails for overlays using
> > > phandle-based
> > > targeting (target = <&label>) because DTC compiles these as 
> > > unresolved
> > > fixups (target = <0xffffffff>), causing fdt_overlay_target_offset() 
> > > to
> > > return -FDT_ERR_BADPHANDLE. Prior to this change users were forced to
> > > manually modify the dtbo (even for hwdom) to switch from target to
> > > target-phandle by manually inspecting also the host DTB.
> > >
> > > Introduce overlay_get_target_path() which directly handles the two
> > > targeting cases that occur before fixup resolution:
> > >  - target-path: the string property is returned directly.
> > >  - target = <&label>: the label is found in the overlay's __fixups__
> > >    node, then resolved to a path via the base DTB's __symbols__ node.
> > >
> > > Libfdt fdt_for_each_property_offset() violates MISRA R20.7. Despite
> > > libfdt being excluded from the analysis, this causes ECLAIR scan to
> > > report a regression because the violation introduced by a macro is
> > > reported at the call site. Deviate R20.7 for libfdt.h.
> > >
> > > Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
> > > Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > > Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
> > > ---
> > > In my pre-push testing I realized ECLAIR allcode reported a violation
> > > related to
> > > the use of fdt_for_each_property_offset. Libfdt is excluded from
> > > analysis but
> > > this does not apply to e.g. macros used in other places.
> > >
> > > Changes in v2:
> > >  - strip out from series that is ready to be committed
> > >  - deviate 20.7 for libfdt.h. Discussed with Nicole.
> > >
> > > https://gitlab.com/xen-project/people/morzel/xen/-/pipelines/2484326830
> > > ---
> > >  .../eclair_analysis/ECLAIR/deviations.ecl     |  1 +
> > >  xen/common/device-tree/dt-overlay.c           | 65 
> > > +++++++++++++++++--
> > >  2 files changed, 60 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl
> > > b/automation/eclair_analysis/ECLAIR/deviations.ecl
> > > index 30c323906924..5f0b73062474 100644
> > > --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> > > +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> > > @@ -631,6 +631,7 @@ not in scope for compliance are allowed, as that 
> > > is
> > > imported code."
> > >  -file_tag+={acpi_cpu_idle, "^xen/arch/x86/acpi/cpu_idle\\.c$"}
> > >  -config=MC3A2.R20.7,reports+={safe,
> > > "any_area(any_loc(file(gnu_efi_include)||any_exp(macro(^NextMemoryDescriptor$))))"}
> > >  -config=MC3A2.R20.7,reports+={safe,
> > > "any_area(any_loc(file(acpi_cpu_idle)))"}
> > > +-config=MC3A2.R20.7,reports+={safe,
> > > "any_area(any_loc(any_exp(file(^xen/include/xen/libfdt/libfdt.h$))))"}
> > >  -doc_end
> > Nit: I think using a file_tag as above is better, but in any case use
> > libfdt\\.h in the regex
> Ok. Provided I will do this on commit, may I convert this as your 
> Rb/Ab?
> ~Michal
Yes, sure

Reviewed-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>

--
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253