xen/dts: Provide an helper to get a DT node from a path provided by a guest

The maximum size of the copied string has been chosen based on the value
use by XSM in similar case.

Furthermore, Linux seems to allow path up to 4096 characters. Though
this could vary from one OS to another.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 02cae911c7aa5e3a2f92763a0521270ece4716fd..31f169b55c1b1349978c87b4188476b63c30db73 100644 (file)
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -13,6 +13,7 @@
 #include <xen/config.h>
 #include <xen/types.h>
 #include <xen/init.h>
+#include <xen/guest_access.h>
 #include <xen/device_tree.h>
 #include <xen/kernel.h>
 #include <xen/lib.h>
@@ -23,6 +24,7 @@
 #include <xen/cpumask.h>
 #include <xen/ctype.h>
 #include <asm/setup.h>
+#include <xen/err.h>
 
 const void *device_tree_flattened;
 dt_irq_xlate_func dt_irq_xlate;
@@ -277,6 +279,22 @@ struct dt_device_node *dt_find_node_by_path(const char *path)
     return np;
 }
 
+int dt_find_node_by_gpath(XEN_GUEST_HANDLE(char) u_path, uint32_t u_plen,
+                          struct dt_device_node **node)
+{
+    char *path;
+
+    path = safe_copy_string_from_guest(u_path, u_plen, PAGE_SIZE);
+    if ( IS_ERR(path) )
+        return PTR_ERR(path);
+
+    *node = dt_find_node_by_path(path);
+
+    xfree(path);
+
+    return (*node == NULL) ? -ESRCH : 0;
+}
+
 struct dt_device_node *dt_find_node_by_alias(const char *alias)
 {
     const struct dt_alias_prop *app;

diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 57eb3eea53a9399d5b5ca05d60f5dcdce6eb4af3..e187780ea88b79547b08c59e1adad7981a86cafd 100644 (file)
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -456,6 +456,20 @@ struct dt_device_node *dt_find_node_by_alias(const char *alias);
  */
 struct dt_device_node *dt_find_node_by_path(const char *path);
 
+
+/**
+ * dt_find_node_by_gpath - Same as dt_find_node_by_path but retrieve the
+ * path from the guest
+ *
+ * @u_path: Xen Guest handle to the buffer containing the path
+ * @u_plen: Length of the buffer
+ * @node: TODO
+ *
+ * Return 0 if succeed otherwise -errno
+ */
+int dt_find_node_by_gpath(XEN_GUEST_HANDLE(char) u_path, uint32_t u_plen,
+                          struct dt_device_node **node);
+
 /**
  * dt_get_parent - Get a node's parent if any
  * @node: Node to get parent