[PATCH v4] efi_loader: Trigger capsule updates with automatically generated boot options

[Ilias Apalodimas]

The EFI spec in §8.5.5 says
"The directory \EFI\UpdateCapsule is checked for capsules only within
 the EFI system partition on the device specified in the active boot
 option determine by reference to BootNext variable or BootOrder variable
 processing."

Automatically generated boot options don't point to the ESP, they point to
the disk itself and find_handle() won't match when searching for an ESP
during a capsule update.
This happens because find_handle() only matches device paths that are
shorter or equal to the device path passed as an argument.
Since the EFI spec allows it we want to allow capsule updates, when the
boot option points to a disk, but that disk contains an ESP with a
\EFI\UpdateCapsule directory.

So, let's change device_is_present_and_system_part() and check if the
supplied device path contains an ESP. If it does return the handle of
the device. Otherwise, iterate over child devices and return the handle
of the first child that contains an ESP.

The returned handle can then be reused later. Rather than calling
efi_fs_from_path(), we can simply look up the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
on the discovered handle, avoiding the need to re-parse device paths.

Reported-by: Balaji Selvanathan <balaji.selvanathan at oss.qualcomm.com>
Reported-by: John Toomey <john.toomey at amd.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---

Changes from v3:
- Update comments to better match the function functionality

Changes from v2:
- Changing efi_dp_find_obj() wasn't too intuitive, since we only matched
  the longest device path we found from a prefix and made the code complex.
- Change the implementation and iterate over the device children to locate an
  ESP, if the supplied DP is not one.

 lib/efi_loader/efi_capsule.c | 68 ++++++++++++++++++++++++------------
 1 file changed, 46 insertions(+), 22 deletions(-)

diff --git a/lib/efi_loader/efi_capsule.c b/lib/efi_loader/efi_capsule.c
index eafc647f558f..89e63ed8dd5c 100644
--- a/lib/efi_loader/efi_capsule.c
+++ b/lib/efi_loader/efi_capsule.c
@@ -8,6 +8,7 @@
 
 #define LOG_CATEGORY LOGC_EFI
 
+#include <dm/device.h>
 #include <efi_device_path.h>
 #include <efi_loader.h>
 #include <efi_variable.h>
@@ -878,30 +879,47 @@ static efi_status_t get_dp_device(u16 *boot_var,
 }
 
 /**
- * device_is_present_and_system_part - check if a device exists
+ * get_esp_handle - Check if any direct child of the dp handle is an ESP
  *
  * Check if a device pointed to by the device path, @dp, exists and is
- * located in UEFI system partition.
+ * either an ESP or a disk containing an ESP.
  *
  * @dp		device path
- * Return:	true - yes, false - no
+ * Return:	ESP handle or NULL
  */
-static bool device_is_present_and_system_part(struct efi_device_path *dp)
+efi_handle_t get_esp_handle(struct efi_device_path *dp)
 {
-	efi_handle_t handle;
+	efi_handle_t handle, dev_handle;
+	struct udevice *child_dev;
 	struct efi_device_path *rem;
+	efi_status_t ret;
 
 	/* Check device exists */
-	handle = efi_dp_find_obj(dp, NULL, NULL);
-	if (!handle)
-		return false;
+	dev_handle = efi_dp_find_obj(dp, NULL, NULL);
+	if (!dev_handle)
+		return NULL;
 
-	/* Check device is on system partition */
+	/* Check if the device path points to an EFI system partition */
 	handle = efi_dp_find_obj(dp, &efi_system_partition_guid, &rem);
-	if (!handle)
-		return false;
+	if (handle)
+		return handle;
+
+	list_for_each_entry(child_dev, &dev_handle->dev->child_head, sibling_node) {
+		if (device_get_uclass_id(child_dev) != UCLASS_PARTITION)
+			continue;
+		if (dev_tag_get_ptr(child_dev, DM_TAG_EFI, (void **)&handle))
+			continue;
+
+		ret = EFI_CALL(systab.boottime->open_protocol(
+			       handle, &efi_system_partition_guid, NULL, NULL,
+			       NULL, EFI_OPEN_PROTOCOL_TEST_PROTOCOL));
+		if (ret != EFI_SUCCESS)
+			continue;
 
-	return true;
+		return handle;
+	}
+
+	return NULL;
 }
 
 /**
@@ -920,6 +938,8 @@ static efi_status_t find_boot_device(void)
 	int i, num;
 	struct efi_simple_file_system_protocol *volume;
 	struct efi_device_path *boot_dev = NULL;
+	struct efi_handler *handler;
+	efi_handle_t esp = NULL;
 	efi_status_t ret;
 
 	/* find active boot device in BootNext */
@@ -940,7 +960,8 @@ static efi_status_t find_boot_device(void)
 
 		ret = get_dp_device(boot_var16, &boot_dev);
 		if (ret == EFI_SUCCESS) {
-			if (device_is_present_and_system_part(boot_dev)) {
+			esp = get_esp_handle(boot_dev);
+			if (esp) {
 				goto found;
 			} else {
 				efi_free_pool(boot_dev);
@@ -967,26 +988,29 @@ skip:
 		if (ret != EFI_SUCCESS)
 			continue;
 
-		if (device_is_present_and_system_part(boot_dev))
+		esp = get_esp_handle(boot_dev);
+		if (esp)
 			break;
 
 		efi_free_pool(boot_dev);
 		boot_dev = NULL;
 	}
+
 found:
-	if (boot_dev) {
+	ret = EFI_NOT_FOUND;
+	if (esp) {
 		log_debug("Boot device %pD\n", boot_dev);
 
-		volume = efi_fs_from_path(boot_dev);
-		if (!volume)
-			ret = EFI_DEVICE_ERROR;
-		else
+		efi_free_pool(boot_dev);
+		ret = efi_search_protocol(esp, &efi_simple_file_system_protocol_guid,
+					  &handler);
+		if (ret == EFI_SUCCESS) {
+			volume = handler->protocol_interface;
 			ret = EFI_CALL(volume->open_volume(volume,
 							   &bootdev_root));
-		efi_free_pool(boot_dev);
-	} else {
-		ret = EFI_NOT_FOUND;
+		}
 	}
+
 out:
 	free(boot_order);
 
-- 
2.43.0