Add some routines for working with EFI DEVICE_PATH objects.

- efi_lookup_devpath() uses the DEVICE_PATH_PROTOCOL to obtain the
  DEVICE_PATH for a given EFI handle.
- efi_lookup_image_devpath() uses the LOADED_IMAGE_DEVICE_PATH_PROTOCOL
  to lookup the device path of the device used to load a loaded image.
- efi_devpath_name() uses the DEVICE_PATH_TO_TEXT_PROTOCOL to generate
  a string description of a device path.  The returned string is a CHAR16
  string that can be printed via the recently added '%S' format in
  libstand's printf().  Note that the returned string is returned in
  allocated storage that should be freed by calling
  efi_free_devpath_name().
- efi_devpath_last_node() walks a DEVICE_PATH returning a pointer to the
  final node in the path (not counting the terminating node).  That is,
  it returns a pointer to the last meaninful node in a DEVICE_PATH.
- efi_devpath_trim() generates a new DEVICE_PATH from an existing
  DEVICE_PATH.  The new DEVICE_PATH does not include the last
  non-terminating node in the original path.  If the original DEVICE_PATH
  only contains the terminating node, this function returns NULL.
  The caller is responsible for freeing the returned DEVICE_PATH via
  free().
- efi_devpath_handle() attempts to find a handle that corresponds to a
  given device path.  However, if nodes at the end of the device path do
  not have valid handles associated with them, this function will return
  a handle that matches a node earlier in the device path.  In particular,
  this function returns a handle for the node closest to the end of the
  device path which has a valid handle.

Sponsored by:	Cisco Systems

3 files changed, 177 insertions, 2 deletions

diff --git a/sys/boot/efi/include/efilib.h b/sys/boot/efi/include/efilib.h
index 6717cb1..64e8622 100644
--- a/sys/boot/efi/include/efilib.h
+++ b/sys/boot/efi/include/efilib.h
@@ -45,6 +45,14 @@ EFI_HANDLE efi_find_handle(struct devsw *, int);
 int efi_handle_lookup(EFI_HANDLE, struct devsw **, int *,  uint64_t *);
 int efi_handle_update_dev(EFI_HANDLE, struct devsw *, int, uint64_t);
 
+EFI_DEVICE_PATH *efi_lookup_image_devpath(EFI_HANDLE);
+EFI_DEVICE_PATH *efi_lookup_devpath(EFI_HANDLE);
+EFI_HANDLE efi_devpath_handle(EFI_DEVICE_PATH *);
+EFI_DEVICE_PATH *efi_devpath_last_node(EFI_DEVICE_PATH *);
+EFI_DEVICE_PATH *efi_devpath_trim(EFI_DEVICE_PATH *);
+CHAR16 *efi_devpath_name(EFI_DEVICE_PATH *);
+void efi_free_devpath_name(CHAR16 *);
+
 int efi_status_to_errno(EFI_STATUS);
 
 EFI_STATUS main(int argc, CHAR16 *argv[]);
diff --git a/sys/boot/efi/libefi/Makefile b/sys/boot/efi/libefi/Makefile
index 82119a5..c1ee1c6 100644
--- a/sys/boot/efi/libefi/Makefile
+++ b/sys/boot/efi/libefi/Makefile
@@ -4,8 +4,8 @@ LIB=	efi
 INTERNALLIB=
 WARNS?=	2
 
-SRCS=	delay.c efi_console.c efinet.c efipart.c env.c errno.c handles.c \
-	libefi.c time.c
+SRCS=	delay.c devpath.c efi_console.c efinet.c efipart.c env.c errno.c \
+	handles.c libefi.c time.c
 
 .if ${MACHINE_CPUARCH} == "aarch64"
 CFLAGS+=	-msoft-float -mgeneral-regs-only
diff --git a/sys/boot/efi/libefi/devpath.c b/sys/boot/efi/libefi/devpath.c
new file mode 100644
index 0000000..105c861
--- /dev/null
+++ b/sys/boot/efi/libefi/devpath.c
@@ -0,0 +1,167 @@
+/*-
+ * Copyright (c) 2016 John Baldwin <jhb@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <efi.h>
+#include <efilib.h>
+
+/* XXX: This belongs in an efifoo.h header. */
+#define	EFI_LOADED_IMAGE_DEVICE_PATH_PROTOCOL_GUID			\
+    { 0xbc62157e, 0x3e33, 0x4fec, { 0x99, 0x20, 0x2d, 0x3b, 0x36, 0xd7, 0x50, 0xdf } }
+
+#define	EFI_DEVICE_PATH_TO_TEXT_PROTOCOL_GUID				\
+    { 0x8b843e20, 0x8132, 0x4852, { 0x90, 0xcc, 0x55, 0x1a, 0x4e, 0x4a, 0x7f, 0x1c } }
+
+INTERFACE_DECL(_EFI_DEVICE_PATH_PROTOCOL);
+
+typedef
+CHAR16*
+(EFIAPI *EFI_DEVICE_PATH_TO_TEXT_NODE) (
+    IN struct _EFI_DEVICE_PATH *This,
+    IN BOOLEAN                 DisplayOnly,
+    IN BOOLEAN                 AllowShortCuts
+    );
+
+typedef
+CHAR16*
+(EFIAPI *EFI_DEVICE_PATH_TO_TEXT_PATH) (
+    IN struct _EFI_DEVICE_PATH *This,
+    IN BOOLEAN                 DisplayOnly,
+    IN BOOLEAN                 AllowShortCuts
+    );
+
+typedef struct _EFI_DEVICE_PATH_TO_TEXT_PROTOCOL {
+	EFI_DEVICE_PATH_TO_TEXT_NODE ConvertDeviceNodeToText;
+	EFI_DEVICE_PATH_TO_TEXT_PATH ConvertDevicePathToText;
+} EFI_DEVICE_PATH_TO_TEXT_PROTOCOL;
+
+static EFI_GUID ImageDevicePathGUID =
+    EFI_LOADED_IMAGE_DEVICE_PATH_PROTOCOL_GUID;
+static EFI_GUID DevicePathGUID = DEVICE_PATH_PROTOCOL;
+static EFI_GUID DevicePathToTextGUID = EFI_DEVICE_PATH_TO_TEXT_PROTOCOL_GUID;
+static EFI_DEVICE_PATH_TO_TEXT_PROTOCOL *textProtocol;
+
+EFI_DEVICE_PATH *
+efi_lookup_image_devpath(EFI_HANDLE handle)
+{
+	EFI_DEVICE_PATH *devpath;
+	EFI_STATUS status;
+
+	status = BS->HandleProtocol(handle, &ImageDevicePathGUID,
+	    (VOID **)&devpath);
+	if (EFI_ERROR(status))
+		devpath = NULL;
+	return (devpath);
+}
+
+EFI_DEVICE_PATH *
+efi_lookup_devpath(EFI_HANDLE handle)
+{
+	EFI_DEVICE_PATH *devpath;
+	EFI_STATUS status;
+
+	status = BS->HandleProtocol(handle, &DevicePathGUID, (VOID **)&devpath);
+	if (EFI_ERROR(status))
+		devpath = NULL;
+	return (devpath);
+}
+
+CHAR16 *
+efi_devpath_name(EFI_DEVICE_PATH *devpath)
+{
+	static int once = 1;
+	EFI_STATUS status;
+
+	if (devpath == NULL)
+		return (NULL);
+	if (once) {
+		status = BS->LocateProtocol(&DevicePathToTextGUID, NULL,
+		    (VOID **)&textProtocol);
+		if (EFI_ERROR(status))
+			textProtocol = NULL;
+		once = 0;
+	}
+	if (textProtocol == NULL)
+		return (NULL);
+
+	return (textProtocol->ConvertDevicePathToText(devpath, TRUE, TRUE));
+}
+
+void
+efi_free_devpath_name(CHAR16 *text)
+{
+
+	BS->FreePool(text);
+}
+
+EFI_DEVICE_PATH *
+efi_devpath_last_node(EFI_DEVICE_PATH *devpath)
+{
+
+	if (IsDevicePathEnd(devpath))
+		return (NULL);
+	while (!IsDevicePathEnd(NextDevicePathNode(devpath)))
+		devpath = NextDevicePathNode(devpath);
+	return (devpath);
+}
+
+EFI_DEVICE_PATH *
+efi_devpath_trim(EFI_DEVICE_PATH *devpath)
+{
+	EFI_DEVICE_PATH *node, *copy;
+	size_t prefix, len;
+
+	node = efi_devpath_last_node(devpath);
+	prefix = (UINT8 *)node - (UINT8 *)devpath;
+	if (prefix == 0)
+		return (NULL);
+	len = prefix + DevicePathNodeLength(NextDevicePathNode(node));
+	copy = malloc(len);
+	memcpy(copy, devpath, prefix);
+	node = (EFI_DEVICE_PATH *)((UINT8 *)copy + prefix);
+	SetDevicePathEndNode(node);
+	return (copy);
+}
+
+EFI_HANDLE
+efi_devpath_handle(EFI_DEVICE_PATH *devpath)
+{
+	EFI_STATUS status;
+	EFI_HANDLE h;
+
+	/*
+	 * There isn't a standard way to locate a handle for a given
+	 * device path.  However, querying the EFI_DEVICE_PATH protocol
+	 * for a given device path should give us a handle for the
+	 * closest node in the path to the end that is valid.
+	 */
+	status = BS->LocateDevicePath(&DevicePathGUID, &devpath, &h);
+	if (EFI_ERROR(status))
+		return (NULL);
+	return (h);
+}