1 files changed, 43 insertions, 10 deletions

diff --git a/arch/arm64/kernel/efi-stub.c b/arch/arm64/kernel/efi-stub.c
index f5374065a..78dfbd34b 100644
--- a/arch/arm64/kernel/efi-stub.c
+++ b/arch/arm64/kernel/efi-stub.c
@@ -13,7 +13,7 @@
 #include <asm/efi.h>
 #include <asm/sections.h>
 
-efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table,
+efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg,
 					unsigned long *image_addr,
 					unsigned long *image_size,
 					unsigned long *reserve_addr,
@@ -23,21 +23,54 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table,
 {
 	efi_status_t status;
 	unsigned long kernel_size, kernel_memsize = 0;
+	unsigned long nr_pages;
+	void *old_image_addr = (void *)*image_addr;
+	unsigned long preferred_offset;
+
+	/*
+	 * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
+	 * a 2 MB aligned base, which itself may be lower than dram_base, as
+	 * long as the resulting offset equals or exceeds it.
+	 */
+	preferred_offset = round_down(dram_base, SZ_2M) + TEXT_OFFSET;
+	if (preferred_offset < dram_base)
+		preferred_offset += SZ_2M;
 
 	/* Relocate the image, if required. */
 	kernel_size = _edata - _text;
-	if (*image_addr != (dram_base + TEXT_OFFSET)) {
+	if (*image_addr != preferred_offset) {
 		kernel_memsize = kernel_size + (_end - _edata);
-		status = efi_low_alloc(sys_table, kernel_memsize + TEXT_OFFSET,
-				       SZ_2M, reserve_addr);
+
+		/*
+		 * First, try a straight allocation at the preferred offset.
+		 * This will work around the issue where, if dram_base == 0x0,
+		 * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
+		 * address of the allocation to be mistaken for a FAIL return
+		 * value or a NULL pointer). It will also ensure that, on
+		 * platforms where the [dram_base, dram_base + TEXT_OFFSET)
+		 * interval is partially occupied by the firmware (like on APM
+		 * Mustang), we can still place the kernel at the address
+		 * 'dram_base + TEXT_OFFSET'.
+		 */
+		*image_addr = *reserve_addr = preferred_offset;
+		nr_pages = round_up(kernel_memsize, EFI_ALLOC_ALIGN) /
+			   EFI_PAGE_SIZE;
+		status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
+					EFI_LOADER_DATA, nr_pages,
+					(efi_physical_addr_t *)reserve_addr);
 		if (status != EFI_SUCCESS) {
-			pr_efi_err(sys_table, "Failed to relocate kernel\n");
-			return status;
+			kernel_memsize += TEXT_OFFSET;
+			status = efi_low_alloc(sys_table_arg, kernel_memsize,
+					       SZ_2M, reserve_addr);
+
+			if (status != EFI_SUCCESS) {
+				pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
+				return status;
+			}
+			*image_addr = *reserve_addr + TEXT_OFFSET;
 		}
-		memcpy((void *)*reserve_addr + TEXT_OFFSET, (void *)*image_addr,
-		       kernel_size);
-		*image_addr = *reserve_addr + TEXT_OFFSET;
-		*reserve_size = kernel_memsize + TEXT_OFFSET;
+		memcpy((void *)*image_addr, old_image_addr, kernel_size);
+		*reserve_size = kernel_memsize;
 	}