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From caba0117dc30f2357eac6d04f3510095dcbaa7f4 Mon Sep 17 00:00:00 2001
From: Paul Barker <pbarker@konsulko.com>
Date: Fri, 18 Dec 2020 23:00:07 +0000
Subject: [PATCH] fdtoverlay: Prevent overlays from modifying phandle
properties
To: David Gibson <david@gibson.dropbear.id.au>,
Jon Loeliger <jdl@jdl.com>,
devicetree-compiler@vger.kernel.org
Cc: Rob Herring <robh@kernel.org>,
Pantelis Antoniou <pantelis.antoniou@konsulko.com>,
Scott Murray <scott.murray@konsulko.com>,
Jan Simon Moeller <jsmoeller@linuxfoundation.org>
When applying an overlay fragment, we should take care not to overwrite
an existing phandle property of the target node as this could break
references to the target node elsewhere in the base dtb.
In addition to potentially breaking references within the resulting fdt,
if the overlay is built with symbols enabled (`-@` option to dtc) then
fdtoverlay will be unable to merge the overlay with a base dtb file.
A new test case is added to check how fdtoverlay handles this case.
Attempting to apply this test overlay without the fix in this patch
results in the following output:
input = tests/overlay_base_ref.test.dtb
output = tests/overlay_overlay_ref.fdtoverlay.dtb
overlay[0] = tests/overlay_overlay_ref.test.dtb
Failed to apply 'tests/overlay_overlay_ref.test.dtb': FDT_ERR_NOTFOUND
In this test case the __overlay__ node in question does not explicitly
contain a phandle property in the dts file, the phandle is added during
compilation as it is referenced by another node within the overlay dts.
This failure occurs due to a sequence of events in the functions called
by fdt_overlay_apply():
1) In overlay_fixup_phandles(), the target of the overlay fragment is
looked up and the target property is set to the phandle of the target
node.
2) In overlay_merge(), the target node is looked up by phandle via
overlay_get_target(). As the __overlay__ node in this test case
itself has a phandle property, the phandle of the target node is
modified.
3) In overlay_symbol_update(), the target node is again looked up by
phandle via overlay_get_target(). But this time the target node
cannot be found as its phandle property was modified.
The fix for this issue is to skip modification of the phandle property
of the target node in step (2) of the above sequence. If the target node
doesn't already contain a phandle property, we can add one without risk.
Upstream-Status: Submitted
https://www.spinics.net/lists/devicetree-compiler/msg03537.html
Signed-off-by: Paul Barker <pbarker@konsulko.com>
---
libfdt/fdt_overlay.c | 2 ++
tests/overlay_base_ref.dts | 19 +++++++++++++++++++
tests/overlay_overlay_ref.dts | 24 ++++++++++++++++++++++++
tests/run_tests.sh | 5 +++++
4 files changed, 50 insertions(+)
create mode 100644 tests/overlay_base_ref.dts
create mode 100644 tests/overlay_overlay_ref.dts
diff --git a/libfdt/fdt_overlay.c b/libfdt/fdt_overlay.c
index d217e79..b3c217a 100644
--- a/libfdt/fdt_overlay.c
+++ b/libfdt/fdt_overlay.c
@@ -573,6 +573,8 @@ static int overlay_apply_node(void *fdt, int target,
if (prop_len < 0)
return prop_len;
+ if (!strcmp(name, "phandle") && fdt_getprop(fdt, target, name, NULL))
+ continue;
ret = fdt_setprop(fdt, target, name, prop, prop_len);
if (ret)
return ret;
diff --git a/tests/overlay_base_ref.dts b/tests/overlay_base_ref.dts
new file mode 100644
index 0000000..1fc02a2
--- /dev/null
+++ b/tests/overlay_base_ref.dts
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2016 NextThing Co
+ * Copyright (c) 2016 Free Electrons
+ * Copyright (c) 2016 Konsulko Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+/dts-v1/;
+
+/ {
+ test: test-node {
+ test-int-property = <42>;
+ };
+
+ test-refs {
+ refs = <&test>;
+ };
+};
diff --git a/tests/overlay_overlay_ref.dts b/tests/overlay_overlay_ref.dts
new file mode 100644
index 0000000..a45c95d
--- /dev/null
+++ b/tests/overlay_overlay_ref.dts
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2016 NextThing Co
+ * Copyright (c) 2016 Free Electrons
+ * Copyright (c) 2016 Konsulko Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+/dts-v1/;
+/plugin/;
+
+/ {
+ fragment@0 {
+ target = <&test>;
+
+ frag0: __overlay__ {
+ test-int-property = <43>;
+ };
+ };
+
+ test-ref {
+ ref = <&frag0>;
+ };
+};
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index 294585b..a65b166 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -329,6 +329,11 @@ dtc_overlay_tests () {
run_test check_path overlay_base_with_aliases.dtb not-exists "/__symbols__"
run_test check_path overlay_base_with_aliases.dtb not-exists "/__fixups__"
run_test check_path overlay_base_with_aliases.dtb not-exists "/__local_fixups__"
+
+ # Test taking a reference to an overlay fragment
+ run_dtc_test -@ -I dts -O dtb -o overlay_base_ref.test.dtb "$SRCDIR/overlay_base_ref.dts"
+ run_dtc_test -@ -I dts -O dtb -o overlay_overlay_ref.test.dtb "$SRCDIR/overlay_overlay_ref.dts"
+ run_wrap_test $FDTOVERLAY -i overlay_base_ref.test.dtb overlay_overlay_ref.test.dtb -o overlay_overlay_ref.fdtoverlay.dtb
}
tree1_tests () {
--
2.26.2
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