[kvm-unit-tests PATCH v3 08/18] arm64: efi: Improve device tree discovery

[Andrew Jones <andrew.jones@linux.dev>]

Check the device tree GUID when the environment variable is missing,
which allows directly loading the unit test with QEMU's '-kernel'
command line parameter, which is much faster than putting the test
in the EFI file system and then running it from the UEFI shell.

Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Signed-off-by: Andrew Jones <andrew.jones@linux.dev>
---
 lib/efi.c       | 19 ++++++++++++-------
 lib/linux/efi.h |  2 ++
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/lib/efi.c b/lib/efi.c
index d94f0fa16fc0..4d1126b4a64e 100644
--- a/lib/efi.c
+++ b/lib/efi.c
@@ -6,13 +6,13 @@
  *
  * SPDX-License-Identifier: LGPL-2.0-or-later
  */
-
-#include "efi.h"
+#include <libcflat.h>
 #include <argv.h>
-#include <stdlib.h>
 #include <ctype.h>
-#include <libcflat.h>
+#include <stdlib.h>
 #include <asm/setup.h>
+#include "efi.h"
+#include "libfdt/libfdt.h"
 
 /* From lib/argv.c */
 extern int __argc, __envc;
@@ -288,13 +288,18 @@ static void *efi_get_fdt(efi_handle_t handle, struct efi_loaded_image_64 *image)
 	efi_char16_t var[] = ENV_VARNAME_DTBFILE;
 	efi_char16_t *val;
 	void *fdt = NULL;
-	int fdtsize;
+	int fdtsize = 0;
 
 	val = efi_get_var(handle, image, var);
-	if (val)
+	if (val) {
 		efi_load_image(handle, image, &fdt, &fdtsize, val);
+		if (fdtsize == 0)
+			return NULL;
+	} else if (efi_get_system_config_table(DEVICE_TREE_GUID, &fdt) != EFI_SUCCESS) {
+		return NULL;
+	}
 
-	return fdt;
+	return fdt_check_header(fdt) == 0 ? fdt : NULL;
 }
 
 efi_status_t efi_main(efi_handle_t handle, efi_system_table_t *sys_tab)
diff --git a/lib/linux/efi.h b/lib/linux/efi.h
index 410f0b1a0da1..92d798f79767 100644
--- a/lib/linux/efi.h
+++ b/lib/linux/efi.h
@@ -66,6 +66,8 @@ typedef guid_t efi_guid_t;
 #define ACPI_TABLE_GUID EFI_GUID(0xeb9d2d30, 0x2d88, 0x11d3, 0x9a, 0x16, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)
 #define ACPI_20_TABLE_GUID EFI_GUID(0x8868e871, 0xe4f1, 0x11d3,  0xbc, 0x22, 0x00, 0x80, 0xc7, 0x3c, 0x88, 0x81)
 
+#define DEVICE_TREE_GUID EFI_GUID(0xb1b621d5, 0xf19c, 0x41a5,  0x83, 0x0b, 0xd9, 0x15, 0x2c, 0x69, 0xaa, 0xe0)
+
 #define LOADED_IMAGE_PROTOCOL_GUID EFI_GUID(0x5b1b31a1, 0x9562, 0x11d2,  0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b)
 
 typedef struct {
-- 
2.44.0