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

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2013, 2014 Linaro Ltd;  <roy.franz@linaro.org>
   4  *
   5  * This file implements the EFI boot stub for the arm64 kernel.
   6  * Adapted from ARM version by Mark Salter <msalter@redhat.com>
   7  */
   8
   9
  10 #include <linux/efi.h>
  11 #include <asm/efi.h>
  12 #include <asm/memory.h>
  13 #include <asm/sections.h>
  14 #include <asm/sysreg.h>
  15
  16 #include "efistub.h"
  17
  18 efi_status_t check_platform_features(void)
  19 {
  20         u64 tg;
  21
  22         /* UEFI mandates support for 4 KB granularity, no need to check */
  23         if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
  24                 return EFI_SUCCESS;
  25
  26         tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
  27         if (tg != ID_AA64MMFR0_TGRAN_SUPPORTED) {
  28                 if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
  29                         pr_efi_err("This 64 KB granular kernel is not supported by your CPU\n");
  30                 else
  31                         pr_efi_err("This 16 KB granular kernel is not supported by your CPU\n");
  32                 return EFI_UNSUPPORTED;
  33         }
  34         return EFI_SUCCESS;
  35 }
  36
  37 efi_status_t handle_kernel_image(unsigned long *image_addr,
  38                                  unsigned long *image_size,
  39                                  unsigned long *reserve_addr,
  40                                  unsigned long *reserve_size,
  41                                  unsigned long dram_base,
  42                                  efi_loaded_image_t *image)
  43 {
  44         efi_status_t status;
  45         unsigned long kernel_size, kernel_memsize = 0;
  46         unsigned long preferred_offset;
  47         u64 phys_seed = 0;
  48
  49         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
  50                 if (!nokaslr()) {
  51                         status = efi_get_random_bytes(sizeof(phys_seed),
  52                                                       (u8 *)&phys_seed);
  53                         if (status == EFI_NOT_FOUND) {
  54                                 pr_efi("EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
  55                         } else if (status != EFI_SUCCESS) {
  56                                 pr_efi_err("efi_get_random_bytes() failed\n");
  57                                 return status;
  58                         }
  59                 } else {
  60                         pr_efi("KASLR disabled on kernel command line\n");
  61                 }
  62         }
  63
  64         /*
  65          * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
  66          * a 2 MB aligned base, which itself may be lower than dram_base, as
  67          * long as the resulting offset equals or exceeds it.
  68          */
  69         preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
  70         if (preferred_offset < dram_base)
  71                 preferred_offset += MIN_KIMG_ALIGN;
  72
  73         kernel_size = _edata - _text;
  74         kernel_memsize = kernel_size + (_end - _edata);
  75
  76         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
  77                 /*
  78                  * Produce a displacement in the interval [0, MIN_KIMG_ALIGN)
  79                  * that doesn't violate this kernel's de-facto alignment
  80                  * constraints.
  81                  */
  82                 u32 mask = (MIN_KIMG_ALIGN - 1) & ~(EFI_KIMG_ALIGN - 1);
  83                 u32 offset = (phys_seed >> 32) & mask;
  84
  85                 /*
  86                  * With CONFIG_RANDOMIZE_TEXT_OFFSET=y, TEXT_OFFSET may not
  87                  * be a multiple of EFI_KIMG_ALIGN, and we must ensure that
  88                  * we preserve the misalignment of 'offset' relative to
  89                  * EFI_KIMG_ALIGN so that statically allocated objects whose
  90                  * alignment exceeds PAGE_SIZE appear correctly aligned in
  91                  * memory.
  92                  */
  93                 offset |= TEXT_OFFSET % EFI_KIMG_ALIGN;
  94
  95                 /*
  96                  * If KASLR is enabled, and we have some randomness available,
  97                  * locate the kernel at a randomized offset in physical memory.
  98                  */
  99                 *reserve_size = kernel_memsize + offset;
 100                 status = efi_random_alloc(*reserve_size,
 101                                           MIN_KIMG_ALIGN, reserve_addr,
 102                                           (u32)phys_seed);
 103
 104                 *image_addr = *reserve_addr + offset;
 105         } else {
 106                 /*
 107                  * Else, try a straight allocation at the preferred offset.
 108                  * This will work around the issue where, if dram_base == 0x0,
 109                  * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
 110                  * address of the allocation to be mistaken for a FAIL return
 111                  * value or a NULL pointer). It will also ensure that, on
 112                  * platforms where the [dram_base, dram_base + TEXT_OFFSET)
 113                  * interval is partially occupied by the firmware (like on APM
 114                  * Mustang), we can still place the kernel at the address
 115                  * 'dram_base + TEXT_OFFSET'.
 116                  */
 117                 *image_addr = (unsigned long)_text;
 118                 if (*image_addr == preferred_offset)
 119                         return EFI_SUCCESS;
 120
 121                 *image_addr = *reserve_addr = preferred_offset;
 122                 *reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
 123
 124                 status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
 125                                      EFI_LOADER_DATA,
 126                                      *reserve_size / EFI_PAGE_SIZE,
 127                                      (efi_physical_addr_t *)reserve_addr);
 128         }
 129
 130         if (status != EFI_SUCCESS) {
 131                 *reserve_size = kernel_memsize + TEXT_OFFSET;
 132                 status = efi_low_alloc(*reserve_size,
 133                                        MIN_KIMG_ALIGN, reserve_addr);
 134
 135                 if (status != EFI_SUCCESS) {
 136                         pr_efi_err("Failed to relocate kernel\n");
 137                         *reserve_size = 0;
 138                         return status;
 139                 }
 140                 *image_addr = *reserve_addr + TEXT_OFFSET;
 141         }
 142
 143         if (image->image_base != _text)
 144                 pr_efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
 145
 146         memcpy((void *)*image_addr, _text, kernel_size);
 147
 148         return EFI_SUCCESS;
 149 }