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 #include <asm/sysreg.h>
  16
  17 #include "efistub.h"
  18
  19 extern bool __nokaslr;
  20
  21 efi_status_t check_platform_features(efi_system_table_t *sys_table_arg)
  22 {
  23         u64 tg;
  24
  25         /* UEFI mandates support for 4 KB granularity, no need to check */
  26         if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
  27                 return EFI_SUCCESS;
  28
  29         tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
  30         if (tg != ID_AA64MMFR0_TGRAN_SUPPORTED) {
  31                 if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
  32                         pr_efi_err(sys_table_arg, "This 64 KB granular kernel is not supported by your CPU\n");
  33                 else
  34                         pr_efi_err(sys_table_arg, "This 16 KB granular kernel is not supported by your CPU\n");
  35                 return EFI_UNSUPPORTED;
  36         }
  37         return EFI_SUCCESS;
  38 }
  39
  40 efi_status_t handle_kernel_image(efi_system_table_t *sys_table_arg,
  41                                  unsigned long *image_addr,
  42                                  unsigned long *image_size,
  43                                  unsigned long *reserve_addr,
  44                                  unsigned long *reserve_size,
  45                                  unsigned long dram_base,
  46                                  efi_loaded_image_t *image)
  47 {
  48         efi_status_t status;
  49         unsigned long kernel_size, kernel_memsize = 0;
  50         void *old_image_addr = (void *)*image_addr;
  51         unsigned long preferred_offset;
  52         u64 phys_seed = 0;
  53
  54         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
  55                 if (!__nokaslr) {
  56                         status = efi_get_random_bytes(sys_table_arg,
  57                                                       sizeof(phys_seed),
  58                                                       (u8 *)&phys_seed);
  59                         if (status == EFI_NOT_FOUND) {
  60                                 pr_efi(sys_table_arg, "EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
  61                         } else if (status != EFI_SUCCESS) {
  62                                 pr_efi_err(sys_table_arg, "efi_get_random_bytes() failed\n");
  63                                 return status;
  64                         }
  65                 } else {
  66                         pr_efi(sys_table_arg, "KASLR disabled on kernel command line\n");
  67                 }
  68         }
  69
  70         /*
  71          * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
  72          * a 2 MB aligned base, which itself may be lower than dram_base, as
  73          * long as the resulting offset equals or exceeds it.
  74          */
  75         preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
  76         if (preferred_offset < dram_base)
  77                 preferred_offset += MIN_KIMG_ALIGN;
  78
  79         kernel_size = _edata - _text;
  80         kernel_memsize = kernel_size + (_end - _edata);
  81
  82         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
  83                 /*
  84                  * If CONFIG_DEBUG_ALIGN_RODATA is not set, produce a
  85                  * displacement in the interval [0, MIN_KIMG_ALIGN) that
  86                  * is a multiple of the minimal segment alignment (SZ_64K)
  87                  */
  88                 u32 mask = (MIN_KIMG_ALIGN - 1) & ~(SZ_64K - 1);
  89                 u32 offset = !IS_ENABLED(CONFIG_DEBUG_ALIGN_RODATA) ?
  90                              (phys_seed >> 32) & mask : TEXT_OFFSET;
  91
  92                 /*
  93                  * If KASLR is enabled, and we have some randomness available,
  94                  * locate the kernel at a randomized offset in physical memory.
  95                  */
  96                 *reserve_size = kernel_memsize + offset;
  97                 status = efi_random_alloc(sys_table_arg, *reserve_size,
  98                                           MIN_KIMG_ALIGN, reserve_addr,
  99                                           (u32)phys_seed);
 100
 101                 *image_addr = *reserve_addr + offset;
 102         } else {
 103                 /*
 104                  * Else, try a straight allocation at the preferred offset.
 105                  * This will work around the issue where, if dram_base == 0x0,
 106                  * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
 107                  * address of the allocation to be mistaken for a FAIL return
 108                  * value or a NULL pointer). It will also ensure that, on
 109                  * platforms where the [dram_base, dram_base + TEXT_OFFSET)
 110                  * interval is partially occupied by the firmware (like on APM
 111                  * Mustang), we can still place the kernel at the address
 112                  * 'dram_base + TEXT_OFFSET'.
 113                  */
 114                 if (*image_addr == preferred_offset)
 115                         return EFI_SUCCESS;
 116
 117                 *image_addr = *reserve_addr = preferred_offset;
 118                 *reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
 119
 120                 status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
 121                                         EFI_LOADER_DATA,
 122                                         *reserve_size / EFI_PAGE_SIZE,
 123                                         (efi_physical_addr_t *)reserve_addr);
 124         }
 125
 126         if (status != EFI_SUCCESS) {
 127                 *reserve_size = kernel_memsize + TEXT_OFFSET;
 128                 status = efi_low_alloc(sys_table_arg, *reserve_size,
 129                                        MIN_KIMG_ALIGN, reserve_addr);
 130
 131                 if (status != EFI_SUCCESS) {
 132                         pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
 133                         *reserve_size = 0;
 134                         return status;
 135                 }
 136                 *image_addr = *reserve_addr + TEXT_OFFSET;
 137         }
 138         memcpy((void *)*image_addr, old_image_addr, kernel_size);
 139
 140         return EFI_SUCCESS;
 141 }