Merge branch 'arm64-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next

Pull ARM64 EFI update from Peter Anvin:
 "By agreement with the ARM64 EFI maintainers, we have agreed to make
  -tip the upstream for all EFI patches.  That is why this patchset
  comes from me :)

  This patchset enables EFI stub support for ARM64, like we already have
  on x86"

* 'arm64-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  arm64: efi: only attempt efi map setup if booting via EFI
  efi/arm64: ignore dtb= when UEFI SecureBoot is enabled
  doc: arm64: add description of EFI stub support
  arm64: efi: add EFI stub
  doc: arm: add UEFI support documentation
  arm64: add EFI runtime services
  efi: Add shared FDT related functions for ARM/ARM64
  arm64: Add function to create identity mappings
  efi: add helper function to get UEFI params from FDT
  doc: efi-stub.txt updates for ARM
  lib: add fdt_empty_tree.c

4 files changed, 649 insertions, 0 deletions

diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 1e75f48b61f8..d420ae2d3413 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -47,6 +47,13 @@ config EFI_RUNTIME_MAP
 
           See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map.
 
+config EFI_PARAMS_FROM_FDT
+        bool
+        help
+          Select this config option from the architecture Kconfig if
+          the EFI runtime support gets system table address, memory
+          map address, and other parameters from the device tree.
+
 endmenu
 
 config UEFI_CPER
diff --git a/drivers/firmware/efi/arm-stub.c b/drivers/firmware/efi/arm-stub.c
new file mode 100644
index 000000000000..41114ce03b01
--- /dev/null
+++ b/drivers/firmware/efi/arm-stub.c
@@ -0,0 +1,278 @@
+/*
+ * EFI stub implementation that is shared by arm and arm64 architectures.
+ * This should be #included by the EFI stub implementation files.
+ *
+ * Copyright (C) 2013,2014 Linaro Limited
+ *     Roy Franz <roy.franz@linaro.org
+ * Copyright (C) 2013 Red Hat, Inc.
+ *     Mark Salter <msalter@redhat.com>
+ *
+ * This file is part of the Linux kernel, and is made available under the
+ * terms of the GNU General Public License version 2.
+ *
+ */
+
+static int __init efi_secureboot_enabled(efi_system_table_t *sys_table_arg)
+{
+        static efi_guid_t const var_guid __initconst = EFI_GLOBAL_VARIABLE_GUID;
+        static efi_char16_t const var_name[] __initconst = {
+                'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 };
+
+        efi_get_variable_t *f_getvar = sys_table_arg->runtime->get_variable;
+        unsigned long size = sizeof(u8);
+        efi_status_t status;
+        u8 val;
+
+        status = f_getvar((efi_char16_t *)var_name, (efi_guid_t *)&var_guid,
+                          NULL, &size, &val);
+
+        switch (status) {
+        case EFI_SUCCESS:
+                return val;
+        case EFI_NOT_FOUND:
+                return 0;
+        default:
+                return 1;
+        }
+}
+
+static efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg,
+                                    void *__image, void **__fh)
+{
+        efi_file_io_interface_t *io;
+        efi_loaded_image_t *image = __image;
+        efi_file_handle_t *fh;
+        efi_guid_t fs_proto = EFI_FILE_SYSTEM_GUID;
+        efi_status_t status;
+        void *handle = (void *)(unsigned long)image->device_handle;
+
+        status = sys_table_arg->boottime->handle_protocol(handle,
+                                 &fs_proto, (void **)&io);
+        if (status != EFI_SUCCESS) {
+                efi_printk(sys_table_arg, "Failed to handle fs_proto\n");
+                return status;
+        }
+
+        status = io->open_volume(io, &fh);
+        if (status != EFI_SUCCESS)
+                efi_printk(sys_table_arg, "Failed to open volume\n");
+
+        *__fh = fh;
+        return status;
+}
+static efi_status_t efi_file_close(void *handle)
+{
+        efi_file_handle_t *fh = handle;
+
+        return fh->close(handle);
+}
+
+static efi_status_t
+efi_file_read(void *handle, unsigned long *size, void *addr)
+{
+        efi_file_handle_t *fh = handle;
+
+        return fh->read(handle, size, addr);
+}
+
+
+static efi_status_t
+efi_file_size(efi_system_table_t *sys_table_arg, void *__fh,
+              efi_char16_t *filename_16, void **handle, u64 *file_sz)
+{
+        efi_file_handle_t *h, *fh = __fh;
+        efi_file_info_t *info;
+        efi_status_t status;
+        efi_guid_t info_guid = EFI_FILE_INFO_ID;
+        unsigned long info_sz;
+
+        status = fh->open(fh, &h, filename_16, EFI_FILE_MODE_READ, (u64)0);
+        if (status != EFI_SUCCESS) {
+                efi_printk(sys_table_arg, "Failed to open file: ");
+                efi_char16_printk(sys_table_arg, filename_16);
+                efi_printk(sys_table_arg, "\n");
+                return status;
+        }
+
+        *handle = h;
+
+        info_sz = 0;
+        status = h->get_info(h, &info_guid, &info_sz, NULL);
+        if (status != EFI_BUFFER_TOO_SMALL) {
+                efi_printk(sys_table_arg, "Failed to get file info size\n");
+                return status;
+        }
+
+grow:
+        status = sys_table_arg->boottime->allocate_pool(EFI_LOADER_DATA,
+                                 info_sz, (void **)&info);
+        if (status != EFI_SUCCESS) {
+                efi_printk(sys_table_arg, "Failed to alloc mem for file info\n");
+                return status;
+        }
+
+        status = h->get_info(h, &info_guid, &info_sz,
+                                                   info);
+        if (status == EFI_BUFFER_TOO_SMALL) {
+                sys_table_arg->boottime->free_pool(info);
+                goto grow;
+        }
+
+        *file_sz = info->file_size;
+        sys_table_arg->boottime->free_pool(info);
+
+        if (status != EFI_SUCCESS)
+                efi_printk(sys_table_arg, "Failed to get initrd info\n");
+
+        return status;
+}
+
+
+
+static void efi_char16_printk(efi_system_table_t *sys_table_arg,
+                              efi_char16_t *str)
+{
+        struct efi_simple_text_output_protocol *out;
+
+        out = (struct efi_simple_text_output_protocol *)sys_table_arg->con_out;
+        out->output_string(out, str);
+}
+
+
+/*
+ * This function handles the architcture specific differences between arm and
+ * arm64 regarding where the kernel image must be loaded and any memory that
+ * must be reserved. On failure it is required to free all
+ * all allocations it has made.
+ */
+static efi_status_t handle_kernel_image(efi_system_table_t *sys_table,
+                                        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 entry point for the arm/arm64 EFI stubs.  This is the entrypoint
+ * that is described in the PE/COFF header.  Most of the code is the same
+ * for both archictectures, with the arch-specific code provided in the
+ * handle_kernel_image() function.
+ */
+unsigned long __init efi_entry(void *handle, efi_system_table_t *sys_table,
+                               unsigned long *image_addr)
+{
+        efi_loaded_image_t *image;
+        efi_status_t status;
+        unsigned long image_size = 0;
+        unsigned long dram_base;
+        /* addr/point and size pairs for memory management*/
+        unsigned long initrd_addr;
+        u64 initrd_size = 0;
+        unsigned long fdt_addr = 0;  /* Original DTB */
+        u64 fdt_size = 0;  /* We don't get size from configuration table */
+        char *cmdline_ptr = NULL;
+        int cmdline_size = 0;
+        unsigned long new_fdt_addr;
+        efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID;
+        unsigned long reserve_addr = 0;
+        unsigned long reserve_size = 0;
+
+        /* Check if we were booted by the EFI firmware */
+        if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
+                goto fail;
+
+        pr_efi(sys_table, "Booting Linux Kernel...\n");
+
+        /*
+         * Get a handle to the loaded image protocol.  This is used to get
+         * information about the running image, such as size and the command
+         * line.
+         */
+        status = sys_table->boottime->handle_protocol(handle,
+                                        &loaded_image_proto, (void *)&image);
+        if (status != EFI_SUCCESS) {
+                pr_efi_err(sys_table, "Failed to get loaded image protocol\n");
+                goto fail;
+        }
+
+        dram_base = get_dram_base(sys_table);
+        if (dram_base == EFI_ERROR) {
+                pr_efi_err(sys_table, "Failed to find DRAM base\n");
+                goto fail;
+        }
+        status = handle_kernel_image(sys_table, image_addr, &image_size,
+                                     &reserve_addr,
+                                     &reserve_size,
+                                     dram_base, image);
+        if (status != EFI_SUCCESS) {
+                pr_efi_err(sys_table, "Failed to relocate kernel\n");
+                goto fail;
+        }
+
+        /*
+         * Get the command line from EFI, using the LOADED_IMAGE
+         * protocol. We are going to copy the command line into the
+         * device tree, so this can be allocated anywhere.
+         */
+        cmdline_ptr = efi_convert_cmdline(sys_table, image, &cmdline_size);
+        if (!cmdline_ptr) {
+                pr_efi_err(sys_table, "getting command line via LOADED_IMAGE_PROTOCOL\n");
+                goto fail_free_image;
+        }
+
+        /*
+         * Unauthenticated device tree data is a security hazard, so
+         * ignore 'dtb=' unless UEFI Secure Boot is disabled.
+         */
+        if (efi_secureboot_enabled(sys_table)) {
+                pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
+        } else {
+                status = handle_cmdline_files(sys_table, image, cmdline_ptr,
+                                              "dtb=",
+                                              ~0UL, (unsigned long *)&fdt_addr,
+                                              (unsigned long *)&fdt_size);
+
+                if (status != EFI_SUCCESS) {
+                        pr_efi_err(sys_table, "Failed to load device tree!\n");
+                        goto fail_free_cmdline;
+                }
+        }
+        if (!fdt_addr)
+                /* Look for a device tree configuration table entry. */
+                fdt_addr = (uintptr_t)get_fdt(sys_table);
+
+        status = handle_cmdline_files(sys_table, image, cmdline_ptr,
+                                      "initrd=", dram_base + SZ_512M,
+                                      (unsigned long *)&initrd_addr,
+                                      (unsigned long *)&initrd_size);
+        if (status != EFI_SUCCESS)
+                pr_efi_err(sys_table, "Failed initrd from command line!\n");
+
+        new_fdt_addr = fdt_addr;
+        status = allocate_new_fdt_and_exit_boot(sys_table, handle,
+                                &new_fdt_addr, dram_base + MAX_FDT_OFFSET,
+                                initrd_addr, initrd_size, cmdline_ptr,
+                                fdt_addr, fdt_size);
+
+        /*
+         * If all went well, we need to return the FDT address to the
+         * calling function so it can be passed to kernel as part of
+         * the kernel boot protocol.
+         */
+        if (status == EFI_SUCCESS)
+                return new_fdt_addr;
+
+        pr_efi_err(sys_table, "Failed to update FDT and exit boot services\n");
+
+        efi_free(sys_table, initrd_size, initrd_addr);
+        efi_free(sys_table, fdt_size, fdt_addr);
+
+fail_free_cmdline:
+        efi_free(sys_table, cmdline_size, (unsigned long)cmdline_ptr);
+
+fail_free_image:
+        efi_free(sys_table, image_size, *image_addr);
+        efi_free(sys_table, reserve_size, reserve_addr);
+fail:
+        return EFI_ERROR;
+}
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index af20f1712337..cd36deb619fa 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -20,6 +20,8 @@
 #include <linux/init.h>
 #include <linux/device.h>
 #include <linux/efi.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
 #include <linux/io.h>
 
 struct efi __read_mostly efi = {
@@ -318,3 +320,80 @@ int __init efi_config_init(efi_config_table_type_t *arch_tables)
 
         return 0;
 }
+
+#ifdef CONFIG_EFI_PARAMS_FROM_FDT
+
+#define UEFI_PARAM(name, prop, field)                      \
+        {                                                  \
+                { name },                                  \
+                { prop },                                  \
+                offsetof(struct efi_fdt_params, field),    \
+                FIELD_SIZEOF(struct efi_fdt_params, field) \
+        }
+
+static __initdata struct {
+        const char name[32];
+        const char propname[32];
+        int offset;
+        int size;
+} dt_params[] = {
+        UEFI_PARAM("System Table", "linux,uefi-system-table", system_table),
+        UEFI_PARAM("MemMap Address", "linux,uefi-mmap-start", mmap),
+        UEFI_PARAM("MemMap Size", "linux,uefi-mmap-size", mmap_size),
+        UEFI_PARAM("MemMap Desc. Size", "linux,uefi-mmap-desc-size", desc_size),
+        UEFI_PARAM("MemMap Desc. Version", "linux,uefi-mmap-desc-ver", desc_ver)
+};
+
+struct param_info {
+        int verbose;
+        void *params;
+};
+
+static int __init fdt_find_uefi_params(unsigned long node, const char *uname,
+                                       int depth, void *data)
+{
+        struct param_info *info = data;
+        void *prop, *dest;
+        unsigned long len;
+        u64 val;
+        int i;
+
+        if (depth != 1 ||
+            (strcmp(uname, "chosen") != 0 && strcmp(uname, "chosen@0") != 0))
+                return 0;
+
+        pr_info("Getting parameters from FDT:\n");
+
+        for (i = 0; i < ARRAY_SIZE(dt_params); i++) {
+                prop = of_get_flat_dt_prop(node, dt_params[i].propname, &len);
+                if (!prop) {
+                        pr_err("Can't find %s in device tree!\n",
+                               dt_params[i].name);
+                        return 0;
+                }
+                dest = info->params + dt_params[i].offset;
+
+                val = of_read_number(prop, len / sizeof(u32));
+
+                if (dt_params[i].size == sizeof(u32))
+                        *(u32 *)dest = val;
+                else
+                        *(u64 *)dest = val;
+
+                if (info->verbose)
+                        pr_info("  %s: 0x%0*llx\n", dt_params[i].name,
+                                dt_params[i].size * 2, val);
+        }
+        return 1;
+}
+
+int __init efi_get_fdt_params(struct efi_fdt_params *params, int verbose)
+{
+        struct param_info info;
+
+        info.verbose = verbose;
+        info.params = params;
+
+        return of_scan_flat_dt(fdt_find_uefi_params, &info);
+}
+#endif /* CONFIG_EFI_PARAMS_FROM_FDT */
diff --git a/drivers/firmware/efi/fdt.c b/drivers/firmware/efi/fdt.c
new file mode 100644
index 000000000000..5c6a8e8a9580
--- /dev/null
+++ b/drivers/firmware/efi/fdt.c
@@ -0,0 +1,285 @@
+/*
+ * FDT related Helper functions used by the EFI stub on multiple
+ * architectures. This should be #included by the EFI stub
+ * implementation files.
+ *
+ * Copyright 2013 Linaro Limited; author Roy Franz
+ *
+ * This file is part of the Linux kernel, and is made available
+ * under the terms of the GNU General Public License version 2.
+ *
+ */
+
+static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
+                               unsigned long orig_fdt_size,
+                               void *fdt, int new_fdt_size, char *cmdline_ptr,
+                               u64 initrd_addr, u64 initrd_size,
+                               efi_memory_desc_t *memory_map,
+                               unsigned long map_size, unsigned long desc_size,
+                               u32 desc_ver)
+{
+        int node, prev;
+        int status;
+        u32 fdt_val32;
+        u64 fdt_val64;
+
+        /*
+         * Copy definition of linux_banner here.  Since this code is
+         * built as part of the decompressor for ARM v7, pulling
+         * in version.c where linux_banner is defined for the
+         * kernel brings other kernel dependencies with it.
+         */
+        const char linux_banner[] =
+            "Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"
+            LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n";
+
+        /* Do some checks on provided FDT, if it exists*/
+        if (orig_fdt) {
+                if (fdt_check_header(orig_fdt)) {
+                        pr_efi_err(sys_table, "Device Tree header not valid!\n");
+                        return EFI_LOAD_ERROR;
+                }
+                /*
+                 * We don't get the size of the FDT if we get if from a
+                 * configuration table.
+                 */
+                if (orig_fdt_size && fdt_totalsize(orig_fdt) > orig_fdt_size) {
+                        pr_efi_err(sys_table, "Truncated device tree! foo!\n");
+                        return EFI_LOAD_ERROR;
+                }
+        }
+
+        if (orig_fdt)
+                status = fdt_open_into(orig_fdt, fdt, new_fdt_size);
+        else
+                status = fdt_create_empty_tree(fdt, new_fdt_size);
+
+        if (status != 0)
+                goto fdt_set_fail;
+
+        /*
+         * Delete any memory nodes present. We must delete nodes which
+         * early_init_dt_scan_memory may try to use.
+         */
+        prev = 0;
+        for (;;) {
+                const char *type, *name;
+                int len;
+
+                node = fdt_next_node(fdt, prev, NULL);
+                if (node < 0)
+                        break;
+
+                type = fdt_getprop(fdt, node, "device_type", &len);
+                if (type && strncmp(type, "memory", len) == 0) {
+                        fdt_del_node(fdt, node);
+                        continue;
+                }
+
+                prev = node;
+        }
+
+        node = fdt_subnode_offset(fdt, 0, "chosen");
+        if (node < 0) {
+                node = fdt_add_subnode(fdt, 0, "chosen");
+                if (node < 0) {
+                        status = node; /* node is error code when negative */
+                        goto fdt_set_fail;
+                }
+        }
+
+        if ((cmdline_ptr != NULL) && (strlen(cmdline_ptr) > 0)) {
+                status = fdt_setprop(fdt, node, "bootargs", cmdline_ptr,
+                                     strlen(cmdline_ptr) + 1);
+                if (status)
+                        goto fdt_set_fail;
+        }
+
+        /* Set initrd address/end in device tree, if present */
+        if (initrd_size != 0) {
+                u64 initrd_image_end;
+                u64 initrd_image_start = cpu_to_fdt64(initrd_addr);
+
+                status = fdt_setprop(fdt, node, "linux,initrd-start",
+                                     &initrd_image_start, sizeof(u64));
+                if (status)
+                        goto fdt_set_fail;
+                initrd_image_end = cpu_to_fdt64(initrd_addr + initrd_size);
+                status = fdt_setprop(fdt, node, "linux,initrd-end",
+                                     &initrd_image_end, sizeof(u64));
+                if (status)
+                        goto fdt_set_fail;
+        }
+
+        /* Add FDT entries for EFI runtime services in chosen node. */
+        node = fdt_subnode_offset(fdt, 0, "chosen");
+        fdt_val64 = cpu_to_fdt64((u64)(unsigned long)sys_table);
+        status = fdt_setprop(fdt, node, "linux,uefi-system-table",
+                             &fdt_val64, sizeof(fdt_val64));
+        if (status)
+                goto fdt_set_fail;
+
+        fdt_val64 = cpu_to_fdt64((u64)(unsigned long)memory_map);
+        status = fdt_setprop(fdt, node, "linux,uefi-mmap-start",
+                             &fdt_val64,  sizeof(fdt_val64));
+        if (status)
+                goto fdt_set_fail;
+
+        fdt_val32 = cpu_to_fdt32(map_size);
+        status = fdt_setprop(fdt, node, "linux,uefi-mmap-size",
+                             &fdt_val32,  sizeof(fdt_val32));
+        if (status)
+                goto fdt_set_fail;
+
+        fdt_val32 = cpu_to_fdt32(desc_size);
+        status = fdt_setprop(fdt, node, "linux,uefi-mmap-desc-size",
+                             &fdt_val32, sizeof(fdt_val32));
+        if (status)
+                goto fdt_set_fail;
+
+        fdt_val32 = cpu_to_fdt32(desc_ver);
+        status = fdt_setprop(fdt, node, "linux,uefi-mmap-desc-ver",
+                             &fdt_val32, sizeof(fdt_val32));
+        if (status)
+                goto fdt_set_fail;
+
+        /*
+         * Add kernel version banner so stub/kernel match can be
+         * verified.
+         */
+        status = fdt_setprop_string(fdt, node, "linux,uefi-stub-kern-ver",
+                             linux_banner);
+        if (status)
+                goto fdt_set_fail;
+
+        return EFI_SUCCESS;
+
+fdt_set_fail:
+        if (status == -FDT_ERR_NOSPACE)
+                return EFI_BUFFER_TOO_SMALL;
+
+        return EFI_LOAD_ERROR;
+}
+
+#ifndef EFI_FDT_ALIGN
+#define EFI_FDT_ALIGN EFI_PAGE_SIZE
+#endif
+
+/*
+ * Allocate memory for a new FDT, then add EFI, commandline, and
+ * initrd related fields to the FDT.  This routine increases the
+ * FDT allocation size until the allocated memory is large
+ * enough.  EFI allocations are in EFI_PAGE_SIZE granules,
+ * which are fixed at 4K bytes, so in most cases the first
+ * allocation should succeed.
+ * EFI boot services are exited at the end of this function.
+ * There must be no allocations between the get_memory_map()
+ * call and the exit_boot_services() call, so the exiting of
+ * boot services is very tightly tied to the creation of the FDT
+ * with the final memory map in it.
+ */
+
+efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
+                                            void *handle,
+                                            unsigned long *new_fdt_addr,
+                                            unsigned long max_addr,
+                                            u64 initrd_addr, u64 initrd_size,
+                                            char *cmdline_ptr,
+                                            unsigned long fdt_addr,
+                                            unsigned long fdt_size)
+{
+        unsigned long map_size, desc_size;
+        u32 desc_ver;
+        unsigned long mmap_key;
+        efi_memory_desc_t *memory_map;
+        unsigned long new_fdt_size;
+        efi_status_t status;
+
+        /*
+         * Estimate size of new FDT, and allocate memory for it. We
+         * will allocate a bigger buffer if this ends up being too
+         * small, so a rough guess is OK here.
+         */
+        new_fdt_size = fdt_size + EFI_PAGE_SIZE;
+        while (1) {
+                status = efi_high_alloc(sys_table, new_fdt_size, EFI_FDT_ALIGN,
+                                        new_fdt_addr, max_addr);
+                if (status != EFI_SUCCESS) {
+                        pr_efi_err(sys_table, "Unable to allocate memory for new device tree.\n");
+                        goto fail;
+                }
+
+                /*
+                 * Now that we have done our final memory allocation (and free)
+                 * we can get the memory map key  needed for
+                 * exit_boot_services().
+                 */
+                status = efi_get_memory_map(sys_table, &memory_map, &map_size,
+                                            &desc_size, &desc_ver, &mmap_key);
+                if (status != EFI_SUCCESS)
+                        goto fail_free_new_fdt;
+
+                status = update_fdt(sys_table,
+                                    (void *)fdt_addr, fdt_size,
+                                    (void *)*new_fdt_addr, new_fdt_size,
+                                    cmdline_ptr, initrd_addr, initrd_size,
+                                    memory_map, map_size, desc_size, desc_ver);
+
+                /* Succeeding the first time is the expected case. */
+                if (status == EFI_SUCCESS)
+                        break;
+
+                if (status == EFI_BUFFER_TOO_SMALL) {
+                        /*
+                         * We need to allocate more space for the new
+                         * device tree, so free existing buffer that is
+                         * too small.  Also free memory map, as we will need
+                         * to get new one that reflects the free/alloc we do
+                         * on the device tree buffer.
+                         */
+                        efi_free(sys_table, new_fdt_size, *new_fdt_addr);
+                        sys_table->boottime->free_pool(memory_map);
+                        new_fdt_size += EFI_PAGE_SIZE;
+                } else {
+                        pr_efi_err(sys_table, "Unable to constuct new device tree.\n");
+                        goto fail_free_mmap;
+                }
+        }
+
+        /* Now we are ready to exit_boot_services.*/
+        status = sys_table->boottime->exit_boot_services(handle, mmap_key);
+
+
+        if (status == EFI_SUCCESS)
+                return status;
+
+        pr_efi_err(sys_table, "Exit boot services failed.\n");
+
+fail_free_mmap:
+        sys_table->boottime->free_pool(memory_map);
+
+fail_free_new_fdt:
+        efi_free(sys_table, new_fdt_size, *new_fdt_addr);
+
+fail:
+        return EFI_LOAD_ERROR;
+}
+
+static void *get_fdt(efi_system_table_t *sys_table)
+{
+        efi_guid_t fdt_guid = DEVICE_TREE_GUID;
+        efi_config_table_t *tables;
+        void *fdt;
+        int i;
+
+        tables = (efi_config_table_t *) sys_table->tables;
+        fdt = NULL;
+
+        for (i = 0; i < sys_table->nr_tables; i++)
+                if (efi_guidcmp(tables[i].guid, fdt_guid) == 0) {
+                        fdt = (void *) tables[i].table;
+                        break;
+         }
+
+        return fdt;
+}