Restore phandle references from __fixups__ node

The __fixups__ node contains information about labels. Parse its
properties to create phandle markers which improve the resulting dts
when decompiling a device tree blob.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Message-ID: <20250919092912.663304-14-u.kleine-koenig@baylibre.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

checks.c

@@ -340,6 +340,14 @@ static void check_node_name_format(struct check *c, struct dt_info *dti,
 }
 ERROR(node_name_format, check_node_name_format, NULL, &node_name_chars);
 
+static void check_node_name_not_empty(struct check *c, struct dt_info *dti,
+				      struct node *node)
+{
+	if (node->basenamelen == 0 && node->parent != NULL)
+		FAIL(c, dti, node, "Empty node name");
+}
+ERROR(node_name_not_empty, check_node_name_not_empty, NULL, &node_name_chars);
+
 static void check_node_name_vs_property_name(struct check *c,
 					     struct dt_info *dti,
 					     struct node *node)
@@ -1899,7 +1907,7 @@ WARNING(graph_endpoint, check_graph_endpoint, NULL, &graph_nodes);
 
 static struct check *check_table[] = {
 	&duplicate_node_names, &duplicate_property_names,
-	&node_name_chars, &node_name_format, &property_name_chars,
+	&node_name_chars, &node_name_format, &node_name_not_empty, &property_name_chars,
 	&name_is_string, &name_properties, &node_name_vs_property_name,
 
 	&duplicate_label,

dtc.c

@@ -338,9 +338,14 @@ int main(int argc, char *argv[])
 	if (auto_label_aliases)
 		generate_label_tree(dti, "aliases", false);
 
+	generate_labels_from_tree(dti, "__symbols__");
+
 	if (generate_symbols)
 		generate_label_tree(dti, "__symbols__", true);
 
+	fixup_phandles(dti, "__fixups__");
+	local_fixup_phandles(dti, "__local_fixups__");
+
 	if (generate_fixups) {
 		generate_fixups_tree(dti, "__fixups__");
 		generate_local_fixups_tree(dti, "__local_fixups__");

dtc.h

@@ -339,9 +339,12 @@ struct dt_info *build_dt_info(unsigned int dtsflags,
 			      struct reserve_info *reservelist,
 			      struct node *tree, uint32_t boot_cpuid_phys);
 void sort_tree(struct dt_info *dti);
+void generate_labels_from_tree(struct dt_info *dti, const char *name);
 void generate_label_tree(struct dt_info *dti, const char *name, bool allocph);
 void generate_fixups_tree(struct dt_info *dti, const char *name);
+void fixup_phandles(struct dt_info *dti, const char *name);
 void generate_local_fixups_tree(struct dt_info *dti, const char *name);
+void local_fixup_phandles(struct dt_info *dti, const char *name);
 
 /* Checks */
 
@@ -357,6 +360,9 @@ struct dt_info *dt_from_blob(const char *fname);
 
 /* Tree source */
 
+void property_add_marker(struct property *prop,
+			 enum markertype type, unsigned int offset, char *ref);
+void add_phandle_marker(struct dt_info *dti, struct property *prop, unsigned int offset);
 void dt_to_source(FILE *f, struct dt_info *dti);
 struct dt_info *dt_from_source(const char *f);
 

fdtdump.c

@@ -129,23 +129,25 @@ static void dump_blob(void *blob, bool debug)
 			continue;
 		}
 
-		if (tag != FDT_PROP) {
-			fprintf(stderr, "%*s ** Unknown tag 0x%08"PRIx32"\n", depth * shift, "", tag);
-			break;
+		if (tag == FDT_PROP) {
+			sz = fdt32_to_cpu(GET_CELL(p));
+			s = p_strings + fdt32_to_cpu(GET_CELL(p));
+			if (version < 16 && sz >= 8)
+				p = PALIGN(p, 8);
+			t = p;
+
+			p = PALIGN(p + sz, 4);
+
+			dumpf("%04"PRIxPTR": string: %s\n", (uintptr_t)s - blob_off, s);
+			dumpf("%04"PRIxPTR": value\n", (uintptr_t)t - blob_off);
+			printf("%*s%s", depth * shift, "", s);
+			utilfdt_print_data(t, sz);
+			printf(";\n");
+			continue;
 		}
-		sz = fdt32_to_cpu(GET_CELL(p));
-		s = p_strings + fdt32_to_cpu(GET_CELL(p));
-		if (version < 16 && sz >= 8)
-			p = PALIGN(p, 8);
-		t = p;
 
-		p = PALIGN(p + sz, 4);
-
-		dumpf("%04"PRIxPTR": string: %s\n", (uintptr_t)s - blob_off, s);
-		dumpf("%04"PRIxPTR": value\n", (uintptr_t)t - blob_off);
-		printf("%*s%s", depth * shift, "", s);
-		utilfdt_print_data(t, sz);
-		printf(";\n");
+		fprintf(stderr, "%*s ** Unknown tag 0x%08"PRIx32"\n", depth * shift, "", tag);
+		break;
 	}
 }
 

fdtput.c

@@ -254,19 +254,21 @@ static int create_paths(char **blob, const char *in_path)
 static int create_node(char **blob, const char *node_name)
 {
 	int node = 0;
-	char *p;
+	const char *p;
+	char *path = NULL;
 
 	p = strrchr(node_name, '/');
 	if (!p) {
 		report_error(node_name, -1, -FDT_ERR_BADPATH);
 		return -1;
 	}
-	*p = '\0';
 
 	*blob = realloc_node(*blob, p + 1);
 
 	if (p > node_name) {
-		node = fdt_path_offset(*blob, node_name);
+		path = xstrndup(node_name, (size_t)(p - node_name));
+		node = fdt_path_offset(*blob, path);
+		free(path);
 		if (node < 0) {
 			report_error(node_name, -1, node);
 			return -1;

flattree.c

@@ -807,6 +807,7 @@ struct dt_info *dt_from_blob(const char *fname)
 	struct node *tree;
 	uint32_t val;
 	int flags = 0;
+	unsigned int dtsflags = DTSF_V1;
 
 	f = srcfile_relative_open(fname, NULL);
 
@@ -919,5 +920,8 @@ struct dt_info *dt_from_blob(const char *fname)
 
 	fclose(f);
 
-	return build_dt_info(DTSF_V1, reservelist, tree, boot_cpuid_phys);
+	if (get_subnode(tree, "__fixups__") || get_subnode(tree, "__local_fixups__"))
+		dtsflags |= DTSF_PLUGIN;
+
+	return build_dt_info(dtsflags, reservelist, tree, boot_cpuid_phys);
 }

libfdt/fdt_overlay.c

@@ -407,7 +407,8 @@ static int overlay_fixup_phandle(void *fdt, void *fdto, int symbols_off,
 		const char *fixup_str = value;
 		uint32_t path_len, name_len;
 		uint32_t fixup_len;
-		char *sep, *endptr;
+		const char *sep;
+		char *endptr;
 		int poffset, ret;
 
 		fixup_end = memchr(value, '\0', len);

livetree.c

@@ -1112,6 +1112,27 @@ static int generate_local_fixups_tree_internal(struct dt_info *dti,
 	return ret;
 }
 
+void generate_labels_from_tree(struct dt_info *dti, const char *name)
+{
+	struct node *an;
+	struct property *p;
+
+	an = get_subnode(dti->dt, name);
+	if (!an)
+		return;
+
+	for_each_property(an, p) {
+		struct node *labeled_node;
+
+		labeled_node = get_node_by_path(dti->dt, p->val.val);
+		if (labeled_node)
+			add_label(&labeled_node->labels, p->name);
+		else if (quiet < 1)
+			fprintf(stderr, "Warning: Path %s referenced in property %s/%s missing",
+				p->val.val, name, p->name);
+	}
+}
+
 void generate_label_tree(struct dt_info *dti, const char *name, bool allocph)
 {
 	if (!any_label_tree(dti, dti->dt))
@@ -1130,6 +1151,102 @@ void generate_fixups_tree(struct dt_info *dti, const char *name)
 			name);
 }
 
+void fixup_phandles(struct dt_info *dti, const char *name)
+{
+	struct node *an;
+	struct property *fp;
+
+	an = get_subnode(dti->dt, name);
+	if (!an)
+		return;
+
+	for_each_property(an, fp) {
+		char *fnext = fp->val.val;
+		char *fv;
+		unsigned int fl;
+
+		while ((fl = fp->val.len - (fnext - fp->val.val))) {
+			char *propname, *soffset;
+			struct node *n;
+			struct property *p;
+			long offset;
+
+			fv = fnext;
+			fnext = memchr(fv, 0, fl);
+
+			if (!fnext) {
+				if (quiet < 1)
+					fprintf(stderr, "Warning: Malformed fixup entry for label %s\n",
+						fp->name);
+				break;
+			}
+			fnext += 1;
+
+			propname = memchr(fv, ':', fnext - 1 - fv);
+			if (!propname) {
+				if (quiet < 1)
+					fprintf(stderr, "Warning: Malformed fixup entry for label %s\n",
+						fp->name);
+				continue;
+			}
+			propname++;
+
+			soffset = memchr(propname, ':', fnext - 1 - propname);
+			if (!soffset) {
+				if (quiet < 1)
+					fprintf(stderr, "Warning: Malformed fixup entry for label %s\n",
+						fp->name);
+				continue;
+			}
+			soffset++;
+
+			/*
+			 * temporarily modify the property to not have to create
+			 * a copy for the node path.
+			 */
+			*(propname - 1) = '\0';
+
+			n = get_node_by_path(dti->dt, fv);
+			if (!n && quiet < 1)
+				fprintf(stderr, "Warning: Label %s references non-existing node %s\n",
+					fp->name, fv);
+
+			*(propname - 1) = ':';
+
+			if (!n)
+				continue;
+
+			/*
+			 * temporarily modify the property to not have to create
+			 * a copy for the property name.
+			 */
+			*(soffset - 1) = '\0';
+
+			p = get_property(n, propname);
+
+			if (!p && quiet < 1)
+				fprintf(stderr, "Warning: Label %s references non-existing property %s in node %s\n",
+					fp->name, n->fullpath, propname);
+
+			*(soffset - 1) = ':';
+
+			if (!p)
+				continue;
+
+			offset = strtol(soffset, NULL, 0);
+			if (offset < 0 || offset + 4 > p->val.len) {
+				if (quiet < 1)
+					fprintf(stderr,
+						"Warning: Label %s contains invalid offset for property %s in node %s\n",
+						fp->name, p->name, n->fullpath);
+				continue;
+			}
+
+			property_add_marker(p, REF_PHANDLE, offset, fp->name);
+		}
+	}
+}
+
 void generate_local_fixups_tree(struct dt_info *dti, const char *name)
 {
 	if (!any_local_fixup_tree(dti, dti->dt))
@@ -1139,3 +1256,60 @@ void generate_local_fixups_tree(struct dt_info *dti, const char *name)
 			"Warning: Preexisting data in %s malformed, some content could not be added.\n",
 			name);
 }
+
+static void local_fixup_phandles_node(struct dt_info *dti, struct node *lf, struct node *n)
+{
+	struct property *lfp;
+	struct node *lfsubnode;
+
+	for_each_property(lf, lfp) {
+		struct property *p = get_property(n, lfp->name);
+		fdt32_t *offsets = (fdt32_t *)lfp->val.val;
+		size_t i;
+
+		if (!p) {
+			if (quiet < 1)
+				fprintf(stderr, "Warning: Property %s in %s referenced in __local_fixups__ missing\n",
+					lfp->name, n->fullpath);
+			continue;
+		}
+
+		/*
+		 * Each property in the __local_fixups__ tree is a concatenation
+		 * of offsets, so it must be a multiple of sizeof(fdt32_t).
+		 */
+		if (lfp->val.len % sizeof(fdt32_t)) {
+			if (quiet < 1)
+				fprintf(stderr, "Warning: property %s in /__local_fixups__%s malformed\n",
+					lfp->name, n->fullpath);
+			continue;
+		}
+
+		for (i = 0; i < lfp->val.len / sizeof(fdt32_t); i++)
+			add_phandle_marker(dti, p, dtb_ld32(offsets + i));
+	}
+
+	for_each_child(lf, lfsubnode) {
+		struct node *subnode = get_subnode(n, lfsubnode->name);
+
+		if (!subnode) {
+			if (quiet < 1)
+				fprintf(stderr, "Warning: node %s/%s referenced in __local_fixups__ missing\n",
+					lfsubnode->name, n->fullpath);
+			continue;
+		}
+
+		local_fixup_phandles_node(dti, lfsubnode, subnode);
+	}
+}
+
+void local_fixup_phandles(struct dt_info *dti, const char *name)
+{
+	struct node *an;
+
+	an = get_subnode(dti->dt, name);
+	if (!an)
+		return;
+
+	local_fixup_phandles_node(dti, an, dti->dt);
+}

meson.build

@@ -18,6 +18,7 @@ add_project_arguments(
     '-Wshadow',
     '-Wsuggest-attribute=format',
     '-Wwrite-strings',
+    '-Wdiscarded-qualifiers',
   ]),
   language: 'c'
 )

treesource.c

@@ -173,23 +173,59 @@ static struct marker **add_marker(struct marker **mi,
 	return &nm->next;
 }
 
-static void add_string_markers(struct property *prop)
+void property_add_marker(struct property *prop,
+			 enum markertype type, unsigned int offset, char *ref)
 {
-	int l, len = prop->val.len;
-	const char *p = prop->val.val;
+	add_marker(&prop->val.markers, type, offset, ref);
+}
+
+static void add_string_markers(struct property *prop, unsigned int offset, int len)
+{
+	int l;
+	const char *p = prop->val.val + offset;
 	struct marker **mi = &prop->val.markers;
 
 	for (l = strlen(p) + 1; l < len; l += strlen(p + l) + 1)
-		mi = add_marker(mi, TYPE_STRING, l, NULL);
+		mi = add_marker(mi, TYPE_STRING, offset + l, NULL);
 }
 
-static enum markertype guess_value_type(struct property *prop)
+void add_phandle_marker(struct dt_info *dti, struct property *prop, unsigned int offset)
 {
-	int len = prop->val.len;
-	const char *p = prop->val.val;
-	struct marker *m = prop->val.markers;
+	cell_t phandle;
+	struct node *refn;
+	char *ref;
+
+	if (prop->val.len < offset + 4) {
+		if (quiet < 1)
+			fprintf(stderr,
+				"Warning: property %s too short to contain a phandle at offset %u\n",
+				prop->name, offset);
+		return;
+	}
+
+	phandle = dtb_ld32(prop->val.val + offset);
+	refn = get_node_by_phandle(dti->dt, phandle);
+
+	if (!refn) {
+		if (quiet < 1)
+			fprintf(stderr,
+				"Warning: node referenced by phandle 0x%x in property %s not found\n",
+				phandle, prop->name);
+		return;
+	}
+
+	if (refn->labels)
+		ref = refn->labels->label;
+	else
+		ref = refn->fullpath;
+
+	add_marker(&prop->val.markers, REF_PHANDLE, offset, ref);
+}
+
+static enum markertype guess_value_type(struct property *prop, unsigned int offset, int len)
+{
+	const char *p = prop->val.val + offset;
 	int nnotstring = 0, nnul = 0;
-	int nnotstringlbl = 0, nnotcelllbl = 0;
 	int i;
 
 	for (i = 0; i < len; i++) {
@@ -199,30 +235,49 @@ static enum markertype guess_value_type(struct property *prop)
 			nnul++;
 	}
 
-	for_each_marker_of_type(m, LABEL) {
-		if ((m->offset > 0) && (prop->val.val[m->offset - 1] != '\0'))
-			nnotstringlbl++;
-		if ((m->offset % sizeof(cell_t)) != 0)
-			nnotcelllbl++;
-	}
-
-	if ((p[len-1] == '\0') && (nnotstring == 0) && (nnul <= (len-nnul))
-	    && (nnotstringlbl == 0)) {
+	if ((p[len-1] == '\0') && (nnotstring == 0) && (nnul <= len - nnul)) {
 		if (nnul > 1)
-			add_string_markers(prop);
+			add_string_markers(prop, offset, len);
 		return TYPE_STRING;
-	} else if (((len % sizeof(cell_t)) == 0) && (nnotcelllbl == 0)) {
+	} else if ((len % sizeof(cell_t)) == 0) {
 		return TYPE_UINT32;
 	}
 
 	return TYPE_UINT8;
 }
 
+static void guess_type_markers(struct property *prop)
+{
+	struct marker **m = &prop->val.markers;
+	unsigned int offset = 0;
+
+	for (m = &prop->val.markers; *m; m = &((*m)->next)) {
+		if (is_type_marker((*m)->type))
+			/* assume the whole property is already marked */
+			return;
+
+		if ((*m)->offset > offset) {
+			m = add_marker(m, guess_value_type(prop, offset, (*m)->offset - offset),
+				       offset, NULL);
+
+			offset = (*m)->offset;
+		}
+
+		if ((*m)->type == REF_PHANDLE) {
+			m = add_marker(m, TYPE_UINT32, offset, NULL);
+			offset += 4;
+		}
+	}
+
+	if (offset < prop->val.len)
+		add_marker(m, guess_value_type(prop, offset, prop->val.len - offset),
+			   offset, NULL);
+}
+
 static void write_propval(FILE *f, struct property *prop)
 {
 	size_t len = prop->val.len;
-	struct marker *m = prop->val.markers;
-	struct marker dummy_marker;
+	struct marker *m;
 	enum markertype emit_type = TYPE_NONE;
 	char *srcstr;
 
@@ -241,14 +296,8 @@ static void write_propval(FILE *f, struct property *prop)
 
 	fprintf(f, " =");
 
-	if (!next_type_marker(m)) {
-		/* data type information missing, need to guess */
-		dummy_marker.type = guess_value_type(prop);
-		dummy_marker.next = prop->val.markers;
-		dummy_marker.offset = 0;
-		dummy_marker.ref = NULL;
-		m = &dummy_marker;
-	}
+	guess_type_markers(prop);
+	m = prop->val.markers;
 
 	for_each_marker(m) {
 		size_t chunk_len = (m->next ? m->next->offset : len) - m->offset;
@@ -369,7 +418,10 @@ void dt_to_source(FILE *f, struct dt_info *dti)
 {
 	struct reserve_info *re;
 
-	fprintf(f, "/dts-v1/;\n\n");
+	fprintf(f, "/dts-v1/;\n");
+	if (dti->dtsflags & DTSF_PLUGIN)
+		fprintf(f, "/plugin/;\n");
+	fprintf(f, "\n");
 
 	for (re = dti->reservelist; re; re = re->next) {
 		struct label *l;