efi_loader: Put fdt into convenient location

The uEFI spec doesn't dictate where the device tree should live at, but
legacy 32bit ARM grub2 has some assumptions that it may stay at its place
when it's already loaded by the firmware.

So let's put it somewhere where Linux that comes after would happily find
it - around the recommended 128MB line.

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

cmd/bootefi.c

@@ -12,7 +12,7 @@
 #include <errno.h>
 #include <libfdt.h>
 #include <libfdt_env.h>
-#include <malloc.h>
+#include <memalign.h>
 #include <asm/global_data.h>
 
 DECLARE_GLOBAL_DATA_PTR;
@@ -104,12 +104,34 @@ static struct efi_object bootefi_device_obj = {
 static void *copy_fdt(void *fdt)
 {
 	u64 fdt_size = fdt_totalsize(fdt);
+	unsigned long fdt_ram_start = -1L, fdt_pages;
+	u64 new_fdt_addr;
 	void *new_fdt;
+	int i;
 
-	/* Give us 64kb breathing room */
-	fdt_size += 64 * 1024;
+        for (i = 0; i < CONFIG_NR_DRAM_BANKS; i++) {
+                u64 ram_start = gd->bd->bi_dram[i].start;
+                u64 ram_size = gd->bd->bi_dram[i].size;
 
-	new_fdt = malloc(fdt_size);
+		if (!ram_size)
+			continue;
+
+		if (ram_start < fdt_ram_start)
+			fdt_ram_start = ram_start;
+	}
+
+	/* Give us at least 4kb breathing room */
+	fdt_size = ALIGN(fdt_size + 4096, 4096);
+	fdt_pages = fdt_size >> EFI_PAGE_SHIFT;
+
+	/* Safe fdt location is at 128MB */
+	new_fdt_addr = fdt_ram_start + (128 * 1024 * 1024) + fdt_size;
+	if (efi_allocate_pages(1, EFI_BOOT_SERVICES_DATA, fdt_pages,
+			       &new_fdt_addr) != EFI_SUCCESS) {
+		/* If we can't put it there, put it somewhere */
+		new_fdt_addr = (ulong)memalign(4096, fdt_size);
+	}
+	new_fdt = (void*)(ulong)new_fdt_addr;
 	memcpy(new_fdt, fdt, fdt_totalsize(fdt));
 	fdt_set_totalsize(new_fdt, fdt_size);