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
  13 /*
  14  * To prevent the compiler from emitting GOT-indirected (and thus absolute)
  15  * references to the section markers, override their visibility as 'hidden'
  16  */
  17 #pragma GCC visibility push(hidden)
  18 #include <asm/sections.h>
  19 #pragma GCC visibility pop
  20
  21 #include <linux/efi.h>
  22 #include <asm/efi.h>
  23 #include <asm/memory.h>
  24 #include <asm/sysreg.h>
  25
  26 #include "efistub.h"
  27
  28 efi_status_t check_platform_features(efi_system_table_t *sys_table_arg)
  29 {
  30         u64 tg;
  31
  32         /* UEFI mandates support for 4 KB granularity, no need to check */
  33         if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
  34                 return EFI_SUCCESS;
  35
  36         tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
  37         if (tg != ID_AA64MMFR0_TGRAN_SUPPORTED) {
  38                 if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
  39                         pr_efi_err(sys_table_arg, "This 64 KB granular kernel is not supported by your CPU\n");
  40                 else
  41                         pr_efi_err(sys_table_arg, "This 16 KB granular kernel is not supported by your CPU\n");
  42                 return EFI_UNSUPPORTED;
  43         }
  44         return EFI_SUCCESS;
  45 }
  46
  47 efi_status_t handle_kernel_image(efi_system_table_t *sys_table_arg,
  48                                  unsigned long *image_addr,
  49                                  unsigned long *image_size,
  50                                  unsigned long *reserve_addr,
  51                                  unsigned long *reserve_size,
  52                                  unsigned long dram_base,
  53                                  efi_loaded_image_t *image)
  54 {
  55         efi_status_t status;
  56         unsigned long kernel_size, kernel_memsize = 0;
  57         void *old_image_addr = (void *)*image_addr;
  58         unsigned long preferred_offset;
  59         u64 phys_seed = 0;
  60
  61         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
  62                 if (!nokaslr()) {
  63                         status = efi_get_random_bytes(sys_table_arg,
  64                                                       sizeof(phys_seed),
  65                                                       (u8 *)&phys_seed);
  66                         if (status == EFI_NOT_FOUND) {
  67                                 pr_efi(sys_table_arg, "EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
  68                         } else if (status != EFI_SUCCESS) {
  69                                 pr_efi_err(sys_table_arg, "efi_get_random_bytes() failed\n");
  70                                 return status;
  71                         }
  72                 } else {
  73                         pr_efi(sys_table_arg, "KASLR disabled on kernel command line\n");
  74                 }
  75         }
  76
  77         /*
  78          * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
  79          * a 2 MB aligned base, which itself may be lower than dram_base, as
  80          * long as the resulting offset equals or exceeds it.
  81          */
  82         preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
  83         if (preferred_offset < dram_base)
  84                 preferred_offset += MIN_KIMG_ALIGN;
  85
  86         kernel_size = _edata - _text;
  87         kernel_memsize = kernel_size + (_end - _edata);
  88
  89         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
  90                 /*
  91                  * If CONFIG_DEBUG_ALIGN_RODATA is not set, produce a
  92                  * displacement in the interval [0, MIN_KIMG_ALIGN) that
  93                  * doesn't violate this kernel's de-facto alignment
  94                  * constraints.
  95                  */
  96                 u32 mask = (MIN_KIMG_ALIGN - 1) & ~(EFI_KIMG_ALIGN - 1);
  97                 u32 offset = !IS_ENABLED(CONFIG_DEBUG_ALIGN_RODATA) ?
  98                              (phys_seed >> 32) & mask : TEXT_OFFSET;
  99
 100                 /*
 101                  * With CONFIG_RANDOMIZE_TEXT_OFFSET=y, TEXT_OFFSET may not
 102                  * be a multiple of EFI_KIMG_ALIGN, and we must ensure that
 103                  * we preserve the misalignment of 'offset' relative to
 104                  * EFI_KIMG_ALIGN so that statically allocated objects whose
 105                  * alignment exceeds PAGE_SIZE appear correctly aligned in
 106                  * memory.
 107                  */
 108                 offset |= TEXT_OFFSET % EFI_KIMG_ALIGN;
 109
 110                 /*
 111                  * If KASLR is enabled, and we have some randomness available,
 112                  * locate the kernel at a randomized offset in physical memory.
 113                  */
 114                 *reserve_size = kernel_memsize + offset;
 115                 status = efi_random_alloc(sys_table_arg, *reserve_size,
 116                                           MIN_KIMG_ALIGN, reserve_addr,
 117                                           (u32)phys_seed);
 118
 119                 *image_addr = *reserve_addr + offset;
 120         } else {
 121                 /*
 122                  * Else, try a straight allocation at the preferred offset.
 123                  * This will work around the issue where, if dram_base == 0x0,
 124                  * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
 125                  * address of the allocation to be mistaken for a FAIL return
 126                  * value or a NULL pointer). It will also ensure that, on
 127                  * platforms where the [dram_base, dram_base + TEXT_OFFSET)
 128                  * interval is partially occupied by the firmware (like on APM
 129                  * Mustang), we can still place the kernel at the address
 130                  * 'dram_base + TEXT_OFFSET'.
 131                  */
 132                 if (*image_addr == preferred_offset)
 133                         return EFI_SUCCESS;
 134
 135                 *image_addr = *reserve_addr = preferred_offset;
 136                 *reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
 137
 138                 status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
 139                                         EFI_LOADER_DATA,
 140                                         *reserve_size / EFI_PAGE_SIZE,
 141                                         (efi_physical_addr_t *)reserve_addr);
 142         }
 143
 144         if (status != EFI_SUCCESS) {
 145                 *reserve_size = kernel_memsize + TEXT_OFFSET;
 146                 status = efi_low_alloc(sys_table_arg, *reserve_size,
 147                                        MIN_KIMG_ALIGN, reserve_addr);
 148
 149                 if (status != EFI_SUCCESS) {
 150                         pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
 151                         *reserve_size = 0;
 152                         return status;
 153                 }
 154                 *image_addr = *reserve_addr + TEXT_OFFSET;
 155         }
 156         memcpy((void *)*image_addr, old_image_addr, kernel_size);
 157
 158         return EFI_SUCCESS;
 159 }