[Xen-devel] [PATCH v3 15/24] xen/dts: Provide an helper to get a DT node from a path provided by a guest

[Julien Grall <julien.grall@xxxxxxxxxx>]

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

---
    Changes in v3:
        - Use the new prototype of safe_copy_string_from_guest

    Changes in v2:
        - guest_copy_string_from_guest has been renamed into
        safe_copy_string_from_guest
---
 xen/common/device_tree.c      | 19 +++++++++++++++++++
 xen/include/xen/device_tree.h | 17 +++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index af73b3b..4c9daea 100644
--- 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 +279,23 @@ 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,
+                                       DEVICE_TREE_MAX_PATHLEN);
+    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 19d0e45..9b0ed00 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -22,6 +22,9 @@
 
 #define DEVICE_TREE_MAX_DEPTH 16
 
+/* This limit is used by the hypercalls to restrict the size of the path */
+#define DEVICE_TREE_MAX_PATHLEN 1024
+
 /*
  * Struct used for matching a device
  */
@@ -456,6 +459,20 @@ 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
-- 
2.1.4


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