drivers/firmware/efi/libstub/arm64-stub.c

   1 /*
   2  * Copyright (C) 2013, 2014 Linaro Ltd;  <roy.franz@linaro.org>
   3  *
   4  * This file implements the EFI boot stub for the arm64 kernel.
   5  * Adapted from ARM version by Mark Salter <msalter@redhat.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  */
  12 #include <linux/efi.h>
  13 #include <asm/efi.h>
  14 #include <asm/sections.h>
  15
  16 #include "efistub.h"
  17
  18 extern bool __nokaslr;
  19
  20 efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg,
  21                                         unsigned long *image_addr,
  22                                         unsigned long *image_size,
  23                                         unsigned long *reserve_addr,
  24                                         unsigned long *reserve_size,
  25                                         unsigned long dram_base,
  26                                         efi_loaded_image_t *image)
  27 {
  28         efi_status_t status;
  29         unsigned long kernel_size, kernel_memsize = 0;
  30         void *old_image_addr = (void *)*image_addr;
  31         unsigned long preferred_offset;
  32         u64 phys_seed = 0;
  33
  34         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
  35                 if (!__nokaslr) {
  36                         status = efi_get_random_bytes(sys_table_arg,
  37                                                       sizeof(phys_seed),
  38                                                       (u8 *)&phys_seed);
  39                         if (status == EFI_NOT_FOUND) {
  40                                 pr_efi(sys_table_arg, "EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
  41                         } else if (status != EFI_SUCCESS) {
  42                                 pr_efi_err(sys_table_arg, "efi_get_random_bytes() failed\n");
  43                                 return status;
  44                         }
  45                 } else {
  46                         pr_efi(sys_table_arg, "KASLR disabled on kernel command line\n");
  47                 }
  48         }
  49
  50         /*
  51          * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
  52          * a 2 MB aligned base, which itself may be lower than dram_base, as
  53          * long as the resulting offset equals or exceeds it.
  54          */
  55         preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
  56         if (preferred_offset < dram_base)
  57                 preferred_offset += MIN_KIMG_ALIGN;
  58
  59         kernel_size = _edata - _text;
  60         kernel_memsize = kernel_size + (_end - _edata);
  61
  62         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
  63                 /*
  64                  * If KASLR is enabled, and we have some randomness available,
  65                  * locate the kernel at a randomized offset in physical memory.
  66                  */
  67                 *reserve_size = kernel_memsize + TEXT_OFFSET;
  68                 status = efi_random_alloc(sys_table_arg, *reserve_size,
  69                                           MIN_KIMG_ALIGN, reserve_addr,
  70                                           phys_seed);
  71
  72                 *image_addr = *reserve_addr + TEXT_OFFSET;
  73         } else {
  74                 /*
  75                  * Else, try a straight allocation at the preferred offset.
  76                  * This will work around the issue where, if dram_base == 0x0,
  77                  * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
  78                  * address of the allocation to be mistaken for a FAIL return
  79                  * value or a NULL pointer). It will also ensure that, on
  80                  * platforms where the [dram_base, dram_base + TEXT_OFFSET)
  81                  * interval is partially occupied by the firmware (like on APM
  82                  * Mustang), we can still place the kernel at the address
  83                  * 'dram_base + TEXT_OFFSET'.
  84                  */
  85                 if (*image_addr == preferred_offset)
  86                         return EFI_SUCCESS;
  87
  88                 *image_addr = *reserve_addr = preferred_offset;
  89                 *reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
  90
  91                 status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
  92                                         EFI_LOADER_DATA,
  93                                         *reserve_size / EFI_PAGE_SIZE,
  94                                         (efi_physical_addr_t *)reserve_addr);
  95         }
  96
  97         if (status != EFI_SUCCESS) {
  98                 *reserve_size = kernel_memsize + TEXT_OFFSET;
  99                 status = efi_low_alloc(sys_table_arg, *reserve_size,
 100                                        MIN_KIMG_ALIGN, reserve_addr);
 101
 102                 if (status != EFI_SUCCESS) {
 103                         pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
 104                         *reserve_size = 0;
 105                         return status;
 106                 }
 107                 *image_addr = *reserve_addr + TEXT_OFFSET;
 108         }
 109         memcpy((void *)*image_addr, old_image_addr, kernel_size);
 110
 111         return EFI_SUCCESS;
 112 }