[PATCH v4 5/6] of/overlay: rewrite /aliases path values to live-tree paths

[Abdurrahman Hussain]

/aliases entries added by an overlay reference labeled nodes inside
the overlay via '&label' in the .dtso. dtc renders those references
as string paths at compile time, but the paths encode the overlay's
internal fragment layout (e.g. "/fragment@1/__overlay__/fpga@0/i2c@40000")
rather than the location where the node will live after apply.

Currently only /__symbols__ has its property values rewritten from
overlay-internal paths to live-tree paths by dup_and_fixup_symbol_prop().
/aliases values fall through the plain __of_prop_dup() path and are
copied byte-for-byte, so of_find_node_by_path() on such a value returns
NULL, of_alias_get_id() reports -ENODEV — and the reconfig notifier
added earlier in this series sees uninterpretable paths and can't
populate aliases_lookup for overlay-declared aliases.

The values in /aliases follow the same textual convention as
/__symbols__, so we can reuse the existing rewriter. Detect the
/aliases target node (of_node_is_aliases(), the same predicate the
reconfig notifier uses) and offer every non-pseudo property to
dup_and_fixup_symbol_prop(); the previous patch made its return value
carry the distinction this needs. A value that resolves inside one of
the overlay's fragments is stored rewritten. -ENODEV means the value
is not a path into this overlay — legacy string aliases like "ttyS0",
or absolute live-tree paths — and is copied verbatim, as before this
series. -EINVAL means the value is not a valid non-empty C string; it
is also copied verbatim, but with a warning: consumers
(of_alias_create() and the alias path lookup) validate before
dereferencing, so a malformed alias is inert rather than a reason to
reject an otherwise-valid overlay that applied cleanly before this
series. Only -ENOMEM fails the apply.

Matching on where the value resolves rather than on a "/fragment@"
name prefix matters: init_overlay_changeset() accepts fragments with
any node name, and dtc emits the actual fragment name into the alias
value, so a prefix test would silently leave a hand-named fragment's
alias unrewritten (and misroute a live-tree path that happens to
start with "/fragment@").

Pseudo-properties (name, phandle, linux,phandle) are exempt from the
/aliases handling: the is_pseudo_property() skip at the top of
add_changeset_property() only covers targets already in the live
tree, so a phandle of a newly created /aliases node would otherwise
reach the rewriter — and a phandle value is a raw cell, not a C
string. Such properties take the plain __of_prop_dup() path as
before this patch; of_alias_create() skips them at notifier time.

Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@xxxxxxxxxx>
---
 drivers/of/overlay.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index ad4e50482515..2a37b5260ba7 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -356,6 +356,19 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
 		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
 		if (IS_ERR(new_prop))
 			return PTR_ERR(new_prop);
+	} else if (!is_pseudo_property(overlay_prop->name) &&
+		   of_node_is_aliases(target->np)) {
+		/* rewrite overlay-internal alias values to live-tree paths */
+		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
+		if (new_prop == ERR_PTR(-ENOMEM))
+			return -ENOMEM;
+		if (IS_ERR(new_prop)) {
+			if (new_prop == ERR_PTR(-EINVAL))
+				pr_warn("%pOF/%s is not a valid string; alias will be inert\n",
+					target->np, overlay_prop->name);
+			/* not overlay-internal: copy verbatim, consumers validate */
+			new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
+		}
 	} else {
 		new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
 	}

-- 
2.54.0