arm64/efi: move arm64 specific stub C code to libstub

Now that we added special handling to the C files in libstub, move
the one remaining arm64 specific EFI stub C file to libstub as
well, so that it gets the same treatment. This should prevent future
changes from resulting in binaries that may execute incorrectly in
UEFI context.

With efi-entry.S the only remaining EFI stub source file under
arch/arm64, we can also simplify the Makefile logic somewhat.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

2 files changed, 71 insertions, 0 deletions

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index bca9a76cbd33..92ae557abbbc 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -34,6 +34,9 @@ $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
 lib-$(CONFIG_EFI_ARMSTUB)       += arm-stub.o fdt.o string.o \
                                    $(patsubst %.c,lib-%.o,$(arm-deps))
 
+lib-$(CONFIG_ARM64)             += arm64-stub.o
+CFLAGS_arm64-stub.o             := -DTEXT_OFFSET=$(TEXT_OFFSET)
+
 #
 # arm64 puts the stub in the kernel proper, which will unnecessarily retain all
 # code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
new file mode 100644
index 000000000000..816120ece6bc
--- /dev/null
+++ b/drivers/firmware/efi/libstub/arm64-stub.c
@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2013, 2014 Linaro Ltd;  <roy.franz@linaro.org>
+ *
+ * This file implements the EFI boot stub for the arm64 kernel.
+ * Adapted from ARM version by Mark Salter <msalter@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/efi.h>
+#include <asm/efi.h>
+#include <asm/sections.h>
+
+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,
+                                        unsigned long *reserve_size,
+                                        unsigned long dram_base,
+                                        efi_loaded_image_t *image)
+{
+        efi_status_t status;
+        unsigned long kernel_size, kernel_memsize = 0;
+        unsigned long nr_pages;
+        void *old_image_addr = (void *)*image_addr;
+
+        /* Relocate the image, if required. */
+        kernel_size = _edata - _text;
+        if (*image_addr != (dram_base + TEXT_OFFSET)) {
+                kernel_memsize = kernel_size + (_end - _edata);
+
+                /*
+                 * 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 = dram_base + TEXT_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) {
+                        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 *)*image_addr, old_image_addr, kernel_size);
+                *reserve_size = kernel_memsize;
+        }
+
+
+        return EFI_SUCCESS;
+}