[PATCH 2/2] efi_loader: use short-form DP for load options

[Heinrich Schuchardt]

The GUID of partitions is sufficient for identification and will stay
constant in the lifetime of a boot option. The preceding path of the
device-path may change due to changes in the enumeration of devices.
Therefore it is preferable to use the short-form of device-paths in load
options. Adjust the 'efidebug boot add' command accordingly.

Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
---
 cmd/efidebug.c                   | 15 +++++++++++----
 include/efi_loader.h             |  3 ++-
 lib/efi_loader/efi_device_path.c | 21 +++++++++++++--------
 3 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/cmd/efidebug.c b/cmd/efidebug.c
index 401d13cc4c..f62a4345fd 100644
--- a/cmd/efidebug.c
+++ b/cmd/efidebug.c
@@ -747,7 +747,7 @@ struct efi_device_path *create_initrd_dp(const char *dev, const char *part,
 					 const char *file)

 {
-	struct efi_device_path *tmp_dp = NULL, *tmp_fp = NULL;
+	struct efi_device_path *tmp_dp = NULL, *tmp_fp = NULL, *short_fp;
 	struct efi_device_path *initrd_dp = NULL;
 	efi_status_t ret;
 	const struct efi_initrd_dp id_dp = {
@@ -771,9 +771,12 @@ struct efi_device_path *create_initrd_dp(const char *dev, const char *part,
 		printf("Cannot create device path for \"%s %s\"\n", part, file);
 		goto out;
 	}
+	short_fp = efi_dp_shorten(tmp_fp);
+	if (!short_fp)
+		short_fp = tmp_fp;

 	initrd_dp = efi_dp_append((const struct efi_device_path *)&id_dp,
-				  tmp_fp);
+				  short_fp);

 out:
 	efi_free_pool(tmp_dp);
@@ -807,6 +810,7 @@ static int do_efi_boot_add(struct cmd_tbl *cmdtp, int flag,
 	size_t label_len, label_len16;
 	u16 *label;
 	struct efi_device_path *device_path = NULL, *file_path = NULL;
+	struct efi_device_path *fp_free = NULL;
 	struct efi_device_path *final_fp = NULL;
 	struct efi_device_path *initrd_dp = NULL;
 	struct efi_load_option lo;
@@ -849,13 +853,16 @@ static int do_efi_boot_add(struct cmd_tbl *cmdtp, int flag,

 			/* file path */
 			ret = efi_dp_from_name(argv[3], argv[4], argv[5],
-					       &device_path, &file_path);
+					       &device_path, &fp_free);
 			if (ret != EFI_SUCCESS) {
 				printf("Cannot create device path for \"%s %s\"\n",
 				       argv[3], argv[4]);
 				r = CMD_RET_FAILURE;
 				goto out;
 			}
+			file_path = efi_dp_shorten(fp_free);
+			if (!file_path)
+				file_path = fp_free;
 			fp_size += efi_dp_size(file_path) +
 				sizeof(struct efi_device_path);
 			argc -= 5;
@@ -927,7 +934,7 @@ out:
 	efi_free_pool(final_fp);
 	efi_free_pool(initrd_dp);
 	efi_free_pool(device_path);
-	efi_free_pool(file_path);
+	efi_free_pool(fp_free);
 	free(lo.label);

 	return r;
diff --git a/include/efi_loader.h b/include/efi_loader.h
index e390d323a9..c7d6b7c7f3 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -725,7 +725,8 @@ extern void *efi_bounce_buffer;
 #define EFI_LOADER_BOUNCE_BUFFER_SIZE (64 * 1024 * 1024)
 #endif

-
+/* shorten device path */
+struct efi_device_path *efi_dp_shorten(struct efi_device_path *dp);
 struct efi_device_path *efi_dp_next(const struct efi_device_path *dp);
 int efi_dp_match(const struct efi_device_path *a,
 		 const struct efi_device_path *b);
diff --git a/lib/efi_loader/efi_device_path.c b/lib/efi_loader/efi_device_path.c
index dc787b4d3d..ddd5f132ec 100644
--- a/lib/efi_loader/efi_device_path.c
+++ b/lib/efi_loader/efi_device_path.c
@@ -122,20 +122,25 @@ int efi_dp_match(const struct efi_device_path *a,
 	}
 }

-/*
+/**
+ * efi_dp_shorten() - shorten device-path
+ *
  * We can have device paths that start with a USB WWID or a USB Class node,
  * and a few other cases which don't encode the full device path with bus
  * hierarchy:
  *
- *   - MESSAGING:USB_WWID
- *   - MESSAGING:USB_CLASS
- *   - MEDIA:FILE_PATH
- *   - MEDIA:HARD_DRIVE
- *   - MESSAGING:URI
+ * * MESSAGING:USB_WWID
+ * * MESSAGING:USB_CLASS
+ * * MEDIA:FILE_PATH
+ * * MEDIA:HARD_DRIVE
+ * * MESSAGING:URI
  *
  * See UEFI spec (section 3.1.2, about short-form device-paths)
+ *
+ * @dp:		original devie-path
+ * @Return:	shortened device-path or NULL
  */
-static struct efi_device_path *shorten_path(struct efi_device_path *dp)
+struct efi_device_path *efi_dp_shorten(struct efi_device_path *dp)
 {
 	while (dp) {
 		/*
@@ -189,7 +194,7 @@ static struct efi_object *find_obj(struct efi_device_path *dp, bool short_path,
 				}
 			}

-			obj_dp = shorten_path(efi_dp_next(obj_dp));
+			obj_dp = efi_dp_shorten(efi_dp_next(obj_dp));
 		} while (short_path && obj_dp);
 	}

--
2.34.1