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

[Nicola Vetrini <nicola.vetrini@bugseng.com>]

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@arm.com>
> Acked-by: Stefano Stabellini <sstabellini@kernel.org>
> Signed-off-by: Michal Orzel <michal.orzel@amd.com>
> ---
> 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

>  -doc_begin="To avoid compromising readability, the macros 
> alternative_(v)?call[0-9] are allowed


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