[RFC PATCH v2 05/74] libfdt: Prepare for metadata tag support

[Herve Codina <herve.codina@bootlin.com>]

Metadata tags are tags carrying extra information, either global to
the DTB, specific to a node, or specific to a property.

In several places (e.g. node/property iterators), these tags just need
to be skipped. Introduce fdt_next_tag_filter() which wraps
fdt_next_tag() and uses a user-supplied filter function to decide
whether a tag should be hidden from the caller. Filtered-out tags are
returned as FDT_NOP.

Introduce fdt_tag_filter_skip_metadata() a filter function whose purpose
is to filter metadata tags; actual metadata tag filtering will be added
when metadata tags are defined.

Metadata tags must also be handled when a DTB is modified. They have to
be removed or skipped depending on the modification.

Here also, introduce fdt_tag_is_property_metadata() to provide a central
check for whether a tag is a property metadata tag; actual metadata
check will be added when metadata tags are defined.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 libfdt/fdt.c             | 34 +++++++++++++--
 libfdt/fdt_ro.c          |  3 +-
 libfdt/fdt_rw.c          | 90 +++++++++++++++++++++++++++++++++-------
 libfdt/fdt_wip.c         | 23 +++++++++-
 libfdt/libfdt_internal.h | 10 +++++
 5 files changed, 140 insertions(+), 20 deletions(-)

diff --git a/libfdt/fdt.c b/libfdt/fdt.c
index 7941632f..8c026f26 100644
--- a/libfdt/fdt.c
+++ b/libfdt/fdt.c
@@ -323,6 +323,33 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
 	return fdt_next_tag_(fdt, startoffset, nextoffset, NULL);
 }
 
+uint32_t fdt_next_tag_filter(const void *fdt, int offset, int *nextoffset,
+			     bool (*tag_filter)(void *priv, uint32_t tag),
+			     void *priv)
+{
+	int startoffset = offset;
+	uint32_t tag;
+
+	tag = fdt_next_tag_(fdt, startoffset, nextoffset, NULL);
+	if (tag == FDT_END)
+		return tag;
+
+	if (tag_filter(priv, tag))
+		return FDT_NOP;
+
+	return tag;
+}
+
+bool fdt_tag_filter_skip_metadata(void *data, uint32_t tag)
+{
+	return false;
+}
+
+bool fdt_tag_is_property_metadata(uint32_t tag)
+{
+	return false;
+}
+
 int fdt_check_node_offset_(const void *fdt, int offset)
 {
 	if (!can_assume(VALID_INPUT)
@@ -355,7 +382,8 @@ int fdt_root_offset(const void *fdt)
 
 	do {
 		offset = nextoffset;
-		tag = fdt_next_tag(fdt, offset, &nextoffset);
+		tag = fdt_next_tag_filter(fdt, offset, &nextoffset,
+					  fdt_tag_filter_skip_metadata, NULL);
 		switch (tag) {
 		case FDT_END_NODE:
 		case FDT_PROP:
@@ -393,8 +421,8 @@ int fdt_next_node(const void *fdt, int offset, int *depth)
 
 	do {
 		offset = nextoffset;
-		tag = fdt_next_tag(fdt, offset, &nextoffset);
-
+		tag = fdt_next_tag_filter(fdt, offset, &nextoffset,
+					  fdt_tag_filter_skip_metadata, NULL);
 		switch (tag) {
 		case FDT_PROP:
 		case FDT_NOP:
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index 50c0a8bc..ea6a540d 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -206,7 +206,8 @@ static int nextprop_(const void *fdt, int offset)
 	int nextoffset;
 
 	do {
-		tag = fdt_next_tag(fdt, offset, &nextoffset);
+		tag = fdt_next_tag_filter(fdt, offset, &nextoffset,
+					  fdt_tag_filter_skip_metadata, NULL);
 
 		switch (tag) {
 		case FDT_END:
diff --git a/libfdt/fdt_rw.c b/libfdt/fdt_rw.c
index 1c6ce0a3..30f3da40 100644
--- a/libfdt/fdt_rw.c
+++ b/libfdt/fdt_rw.c
@@ -259,6 +259,42 @@ int fdt_prop_remove_unknown_tags(void *fdt, bool force_inplace,
 	return 0;
 }
 
+int fdt_prop_remove_metadata_tags(void *fdt, bool force_inplace,
+				  int prop_offset)
+{
+	int nextoffset, offset;
+	uint32_t tag;
+
+	/*
+	 * Only inplace using nopify is supported even if we could use an other
+	 * method involving splices if force_inplace is set to false.
+	 */
+
+	tag = fdt_next_tag(fdt, prop_offset, &nextoffset);
+	if (tag == FDT_END)
+		return nextoffset;
+
+	/*
+	 * Look at all tags related to the current property. I.e. tags after the
+	 * current property and before either the next property, a sub-node  or
+	 * the end of current node
+	 */
+	do {
+		offset = nextoffset;
+		tag = fdt_next_tag(fdt, offset, &nextoffset);
+		if (tag == FDT_END)
+			return nextoffset;
+
+		/* Remove metadata tags related to the property */
+		if (fdt_tag_is_property_metadata(tag))
+			fdt_nopify_area(fdt, offset, nextoffset);
+
+	} while ((tag != FDT_PROP) && (tag != FDT_BEGIN_NODE) &&
+		 (tag != FDT_END_NODE));
+
+	return 0;
+}
+
 static int fdt_resize_property_(void *fdt, int nodeoffset,
 				const char *name, int namelen,
 				int len, struct fdt_property **prop)
@@ -273,10 +309,18 @@ static int fdt_resize_property_(void *fdt, int nodeoffset,
 		return oldlen;
 
 	/*
-	 * The property is resized. Remove possible unknown tags related to the
-	 * property downgrading the dtb version.
+	 * The property is resized and data are going to be modified. Remove
+	 * property metadata tags
 	 */
 	prop_offset = fdt_ptr_offset_(fdt, *prop);
+	err = fdt_prop_remove_metadata_tags(fdt, false, prop_offset);
+	if (err)
+		return err;
+
+	/*
+	 * Remove also possible unknown tags related to the property downgrading
+	 * the dtb version.
+	 */
 	err = fdt_prop_remove_unknown_tags(fdt, false, prop_offset, true);
 	if (err)
 		return err;
@@ -289,7 +333,7 @@ static int fdt_resize_property_(void *fdt, int nodeoffset,
 	return 0;
 }
 
-static int fdt_node_skip_unknown_tags(void *fdt, int next)
+static int fdt_node_skip_unknown_and_metadata_tags(void *fdt, int next)
 {
 	int nextoffset = next;
 	int offset;
@@ -299,6 +343,7 @@ static int fdt_node_skip_unknown_tags(void *fdt, int next)
 	 * Skip all tags related to the current node. I.e. tags after the
 	 * current node and before either the next property, a sub-node or the
 	 * end of current node.
+	 * FDT_NOP, unknown tags and potential node metadata tags are skipped.
 	 */
 	do {
 		offset = nextoffset;
@@ -332,10 +377,10 @@ static int fdt_add_property_(void *fdt, int nodeoffset, const char *name,
 
 	/*
 	 * nextoffset it at the first tag after the node.
-	 * Skip possible unknown tags related to the node in order to add the
-	 * property after those tags.
+	 * Skip possible unknown tags and metadata tags related to the node in
+	 * order to add the property after those tags.
 	 */
-	nextoffset = fdt_node_skip_unknown_tags(fdt, nextoffset);
+	nextoffset = fdt_node_skip_unknown_and_metadata_tags(fdt, nextoffset);
 	if (nextoffset < 0)
 		return nextoffset;
 
@@ -453,6 +498,12 @@ int fdt_appendprop(void *fdt, int nodeoffset, const char *name,
 		if (err)
 			return err;
 
+		/*
+		 * We append data to the property. If known metadata tags are
+		 * present, they are related to existing data and not impacted
+		 * by data added. No need to remove them.
+		 */
+
 		newlen = len + oldlen;
 		err = fdt_splice_struct_(fdt, prop->data,
 					 FDT_TAGALIGN(oldlen),
@@ -484,11 +535,16 @@ int fdt_delprop(void *fdt, int nodeoffset, const char *name)
 	if (!prop)
 		return len;
 
+	/* The property is going to be removed. Remove its metadata tags */
+	prop_offset = fdt_ptr_offset_(fdt, prop);
+	err = fdt_prop_remove_metadata_tags(fdt, false, prop_offset);
+	if (err)
+		return err;
+
 	/*
-	 * The property is going to be removed. Remove also possible unknown
-	 * tags related to this property. Keep the dtb version unchanged.
+	 * Remove also possible unknown tags related to this property.
+	 * Keep the dtb version unchanged.
 	 */
-	prop_offset = fdt_ptr_offset_(fdt, prop);
 	err = fdt_prop_remove_unknown_tags(fdt, false, prop_offset, false);
 	if (err)
 		return err;
@@ -522,10 +578,15 @@ int fdt_add_subnode_namelen(void *fdt, int parentoffset,
 		return offset;
 
 	/*
-	 * Try to place the new node after the parent's properties and unknown
-	 * tags related to those properties.
-	 * Unknown tags are reported as FDT_NOP tags by fdt_next_tag.
-	 * Skipping FDT_NOP tags will correctly skip unknown tags.
+	 * Try to place the new node after:
+	 *  - the parent's properties
+	 *  - the metadata tags related to those properties
+	 *  - unknown tags related to those properties.
+	 * Unknown tags are reported as FDT_NOP tags by fdt_next_tag_filter.
+	 * metadata tags are also reported as FDT_NOP by fdt_next_tag_filter
+	 * thanks to the filter function used.
+	 * Skipping FDT_NOP tags will correctly skip unknown tags and metadata
+	 * tags.
 	 */
 	tag = fdt_next_tag(fdt, parentoffset, &nextoffset);
 	/* the fdt_subnode_offset_namelen() should ensure this never hits */
@@ -533,7 +594,8 @@ int fdt_add_subnode_namelen(void *fdt, int parentoffset,
 		return -FDT_ERR_INTERNAL;
 	do {
 		offset = nextoffset;
-		tag = fdt_next_tag(fdt, offset, &nextoffset);
+		tag = fdt_next_tag_filter(fdt, offset, &nextoffset,
+					  fdt_tag_filter_skip_metadata, NULL);
 	} while ((tag == FDT_PROP) || (tag == FDT_NOP));
 
 	nh = fdt_offset_ptr_w_(fdt, offset);
diff --git a/libfdt/fdt_wip.c b/libfdt/fdt_wip.c
index 7ca3ffbc..b2f9f8d1 100644
--- a/libfdt/fdt_wip.c
+++ b/libfdt/fdt_wip.c
@@ -31,6 +31,17 @@ int fdt_setprop_inplace_namelen_partial(void *fdt, int nodeoffset,
 	if ((unsigned)proplen < (len + idx))
 		return -FDT_ERR_NOSPACE;
 
+	if (idx < (unsigned)proplen) {
+		/*
+		 * The property existing data are going to be modified.
+		 * The property metadata tags are related to the property
+		 * data. Remove them.
+		 */
+		err = fdt_prop_remove_metadata_tags(fdt, true, prop_offset);
+		if (err)
+			return err;
+	}
+
 	/*
 	 * Remove unknown tags related to the property downgrading the dtb
 	 * version.
@@ -81,10 +92,18 @@ int fdt_nop_property(void *fdt, int nodeoffset, const char *name)
 		return len;
 
 	/*
-	 * The property is going to be removed (nopified). Remove unknown tags
-	 * related to this property. Keep the dtb version unchanged.
+	 * The property is going to be removed (nopified). Remove its metadata
+	 * tags
 	 */
 	prop_offset = fdt_ptr_offset_(fdt, prop);
+	err = fdt_prop_remove_metadata_tags(fdt, true, prop_offset);
+	if (err)
+		return err;
+
+	/*
+	 * Remove also possible unknown tags related to this property.
+	 * Keep the dtb version unchanged.
+	 */
 	err = fdt_prop_remove_unknown_tags(fdt, true, prop_offset, false);
 	if (err)
 		return err;
diff --git a/libfdt/libfdt_internal.h b/libfdt/libfdt_internal.h
index d4154119..47dfc0d4 100644
--- a/libfdt/libfdt_internal.h
+++ b/libfdt/libfdt_internal.h
@@ -23,6 +23,14 @@ int32_t fdt_ro_probe_(const void *fdt);
 uint32_t fdt_next_tag_(const void *fdt, int startoffset, int *nextoffset,
 		       bool *is_unknown);
 
+uint32_t fdt_next_tag_filter(const void *fdt, int offset, int *nextoffset,
+			     bool (*tag_filter)(void *priv, uint32_t tag),
+			     void *priv);
+
+bool fdt_tag_filter_skip_metadata(void *data, uint32_t tag);
+
+bool fdt_tag_is_property_metadata(uint32_t tag);
+
 int fdt_get_structured_tag_data(uint32_t tag, const void *fdt, int offset,
 				uint32_t *data_len);
 
@@ -31,6 +39,8 @@ int fdt_check_prop_offset_(const void *fdt, int offset);
 
 int fdt_prop_remove_unknown_tags(void *fdt, bool force_inplace,
 				 int prop_offset, bool downgrade_version);
+int fdt_prop_remove_metadata_tags(void *fdt, bool force_inplace,
+				  int prop_offset);
 
 int fdt_getprop_offset_namelen(const void *fdt, int nodeoffset,
 			       const char *name, int namelen);
-- 
2.55.0