efi_loader: Use system fdt as fallback

When the user did not pass any device tree or the boot script
didn't find any, let's use the system device tree as last resort
to get something the payload (Linux) may understand.

This means that on systems that use the same device tree for U-Boot
and Linux we can just share it and there's no need to manually provide
a device tree in the target image.

While at it, also copy and pad the device tree by 64kb to give us
space for modifications.

Signed-off-by: Alexander Graf <agraf@suse.de>
Tested-by: Andreas Färber <afaerber@suse.de>

cmd/bootefi.c

@@ -12,6 +12,10 @@
 #include <errno.h>
 #include <libfdt.h>
 #include <libfdt_env.h>
+#include <malloc.h>
+#include <asm/global_data.h>
+
+DECLARE_GLOBAL_DATA_PTR;
 
 /*
  * When booting using the "bootefi" command, we don't know which
@@ -97,6 +101,21 @@ static struct efi_object bootefi_device_obj = {
 	},
 };
 
+static void *copy_fdt(void *fdt)
+{
+	u64 fdt_size = fdt_totalsize(fdt);
+	void *new_fdt;
+
+	/* Give us 64kb breathing room */
+	fdt_size += 64 * 1024;
+
+	new_fdt = malloc(fdt_size);
+	memcpy(new_fdt, fdt, fdt_totalsize(fdt));
+	fdt_set_totalsize(new_fdt, fdt_size);
+
+	return new_fdt;
+}
+
 /*
  * Load an EFI payload into a newly allocated piece of memory, register all
  * EFI objects it would want to access and jump to it.
@@ -106,6 +125,7 @@ static unsigned long do_bootefi_exec(void *efi)
 	ulong (*entry)(void *image_handle, struct efi_system_table *st);
 	ulong fdt_pages, fdt_size, fdt_start, fdt_end;
 	bootm_headers_t img = { 0 };
+	void *fdt = working_fdt;
 
 	/*
 	 * gd lives in a fixed register which may get clobbered while we execute
@@ -115,28 +135,33 @@ static unsigned long do_bootefi_exec(void *efi)
 
 	/* Update system table to point to our currently loaded FDT */
 
-	if (working_fdt) {
+	/* Fall back to included fdt if none was manually loaded */
+	if (!fdt && gd->fdt_blob)
+		fdt = (void *)gd->fdt_blob;
+
+	if (fdt) {
 		/* Prepare fdt for payload */
-		if (image_setup_libfdt(&img, working_fdt, 0, NULL)) {
+		fdt = copy_fdt(fdt);
+
+		if (image_setup_libfdt(&img, fdt, 0, NULL)) {
 			printf("ERROR: Failed to process device tree\n");
 			return -EINVAL;
 		}
 
 		/* Link to it in the efi tables */
 		systab.tables[0].guid = EFI_FDT_GUID;
-		systab.tables[0].table = working_fdt;
+		systab.tables[0].table = fdt;
 		systab.nr_tables = 1;
 
 		/* And reserve the space in the memory map */
-		fdt_start = ((ulong)working_fdt) & ~EFI_PAGE_MASK;
-		fdt_end = ((ulong)working_fdt) + fdt_totalsize(working_fdt);
+		fdt_start = ((ulong)fdt) & ~EFI_PAGE_MASK;
+		fdt_end = ((ulong)fdt) + fdt_totalsize(fdt);
 		fdt_size = (fdt_end - fdt_start) + EFI_PAGE_MASK;
 		fdt_pages = fdt_size >> EFI_PAGE_SHIFT;
 		/* Give a bootloader the chance to modify the device tree */
 		fdt_pages += 2;
 		efi_add_memory_map(fdt_start, fdt_pages,
 				   EFI_BOOT_SERVICES_DATA, true);
-
 	} else {
 		printf("WARNING: No device tree loaded, expect boot to fail\n");
 		systab.nr_tables = 0;