dm: core: Allow copying ofnode property data when writing

At present ofnode_write_prop() is inconsistent between livetree and
flattree, in that livetree requires the caller to ensure the property
value is stable (e.g. in rodata or allocated) but flattree does not, since
it makes a copy.

This makes the API call a bit painful to use, since the caller must do
different things depending on OF_LIVE.

Add a new 'copy' argument which tells the function to make a copy if
needed. Add some tests to cover this behaviour.

Signed-off-by: Simon Glass <sjg@chromium.org>

doc/develop/driver-model/livetree.rst

@@ -325,3 +325,5 @@ Live tree support was introduced in U-Boot 2017.07. Some possible enhancements
 are:
 
 - support for livetree in SPL and before relocation (if desired)
+- freeing leaked memory caused by writing new nodes / property values to the
+  livetree (ofnode_write_prop())

drivers/core/ofnode.c

@@ -1388,15 +1388,27 @@ ofnode ofnode_by_prop_value(ofnode from, const char *propname,
 }
 
 int ofnode_write_prop(ofnode node, const char *propname, const void *value,
-		      int len)
+		      int len, bool copy)
 {
-	if (of_live_active())
-		return of_write_prop(ofnode_to_np(node), propname, len, value);
-	else
+	if (of_live_active()) {
+		void *newval;
+		int ret;
+
+		if (copy) {
+			newval = malloc(len);
+			if (!newval)
+				return log_ret(-ENOMEM);
+			memcpy(newval, value, len);
+			value = newval;
+		}
+		ret = of_write_prop(ofnode_to_np(node), propname, len, value);
+		if (ret && copy)
+			free(newval);
+		return ret;
+	} else {
 		return fdt_setprop(ofnode_to_fdt(node), ofnode_to_offset(node),
 				   propname, value, len);
-
-	return 0;
+	}
 }
 
 int ofnode_write_string(ofnode node, const char *propname, const char *value)
@@ -1405,7 +1417,8 @@ int ofnode_write_string(ofnode node, const char *propname, const char *value)
 
 	debug("%s: %s = %s", __func__, propname, value);
 
-	return ofnode_write_prop(node, propname, value, strlen(value) + 1);
+	return ofnode_write_prop(node, propname, value, strlen(value) + 1,
+				 false);
 }
 
 int ofnode_write_u32(ofnode node, const char *propname, u32 value)
@@ -1420,7 +1433,7 @@ int ofnode_write_u32(ofnode node, const char *propname, u32 value)
 		return -ENOMEM;
 	*val = cpu_to_fdt32(value);
 
-	return ofnode_write_prop(node, propname, val, sizeof(value));
+	return ofnode_write_prop(node, propname, val, sizeof(value), false);
 }
 
 int ofnode_set_enabled(ofnode node, bool value)

include/dm/ofnode.h

@@ -1350,19 +1350,23 @@ int ofnode_device_is_compatible(ofnode node, const char *compat);
 /**
  * ofnode_write_prop() - Set a property of a ofnode
  *
- * Note that the value passed to the function is *not* allocated by the
- * function itself, but must be allocated by the caller if necessary. However
- * it does allocate memory for the property struct and name.
+ * Note that if @copy is false, the value passed to the function is *not*
+ * allocated by the function itself, but must be allocated by the caller if
+ * necessary. However it does allocate memory for the property struct and name.
  *
  * @node:	The node for whose property should be set
  * @propname:	The name of the property to set
  * @value:	The new value of the property (must be valid prior to calling
  *		the function)
  * @len:	The length of the new value of the property
+ * @copy: true to allocate memory for the value. This only has any effect with
+ *	live tree, since flat tree handles this automatically. It allows a
+ *	node's value to be written to the tree, without requiring that the
+ *	caller allocate it
  * Return: 0 if successful, -ve on error
  */
 int ofnode_write_prop(ofnode node, const char *propname, const void *value,
-		      int len);
+		      int len, bool copy);
 
 /**
  * ofnode_write_string() - Set a string property of a ofnode

test/dm/ofnode.c

@@ -822,7 +822,8 @@ static int dm_test_ofnode_livetree_writing(struct unit_test_state *uts)
 	ut_asserteq_64(FDT_ADDR_T_NONE, dev_read_addr(dev));
 	/* reg = 0x42, size = 0x100 */
 	ut_assertok(ofnode_write_prop(node, "reg",
-				      "\x00\x00\x00\x42\x00\x00\x01\x00", 8));
+				      "\x00\x00\x00\x42\x00\x00\x01\x00", 8,
+				      false));
 	ut_asserteq(0x42, dev_read_addr(dev));
 
 	/* Test disabling devices */
@@ -838,6 +839,65 @@ static int dm_test_ofnode_livetree_writing(struct unit_test_state *uts)
 DM_TEST(dm_test_ofnode_livetree_writing,
 	UT_TESTF_SCAN_PDATA | UT_TESTF_SCAN_FDT);
 
+static int check_write_prop(struct unit_test_state *uts, ofnode node)
+{
+	char prop[] = "middle-name";
+	char name[10];
+	int len;
+
+	strcpy(name, "cecil");
+	len = strlen(name) + 1;
+	ut_assertok(ofnode_write_prop(node, prop, name, len, false));
+	ut_asserteq_str(name, ofnode_read_string(node, prop));
+
+	/* change the underlying value, this should mess up the live tree */
+	strcpy(name, "tony");
+	if (of_live_active()) {
+		ut_asserteq_str(name, ofnode_read_string(node, prop));
+	} else {
+		ut_asserteq_str("cecil", ofnode_read_string(node, prop));
+	}
+
+	/* try again, this time copying the property */
+	strcpy(name, "mary");
+	ut_assertok(ofnode_write_prop(node, prop, name, len, true));
+	ut_asserteq_str(name, ofnode_read_string(node, prop));
+	strcpy(name, "leah");
+
+	/* both flattree and livetree behave the same */
+	ut_asserteq_str("mary", ofnode_read_string(node, prop));
+
+	return 0;
+}
+
+/* writing the tree with and without copying the property */
+static int dm_test_ofnode_write_copy(struct unit_test_state *uts)
+{
+	ofnode node;
+
+	node = ofnode_path("/a-test");
+	ut_assertok(check_write_prop(uts, node));
+
+	return 0;
+}
+DM_TEST(dm_test_ofnode_write_copy, UT_TESTF_SCAN_FDT);
+
+static int dm_test_ofnode_write_copy_ot(struct unit_test_state *uts)
+{
+	oftree otree = get_other_oftree(uts);
+	ofnode node, check_node;
+
+	node = oftree_path(otree, "/node");
+	ut_assertok(check_write_prop(uts, node));
+
+	/* make sure the control FDT is not touched */
+	check_node = ofnode_path("/node");
+	ut_assertnull(ofnode_read_string(check_node, "middle-name"));
+
+	return 0;
+}
+DM_TEST(dm_test_ofnode_write_copy_ot, UT_TESTF_OTHER_FDT);
+
 static int dm_test_ofnode_u32(struct unit_test_state *uts)
 {
 	ofnode node;