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  * To prevent the compiler from emitting GOT-indirected (and thus absolute)
  11  * references to the section markers, override their visibility as 'hidden'
  12  */
  13 #pragma GCC visibility push(hidden)
  14 #include <asm/sections.h>
  15 #pragma GCC visibility pop
  16
  17 #include <linux/efi.h>
  18 #include <asm/efi.h>
  19 #include <asm/memory.h>
  20 #include <asm/sysreg.h>
  21
  22 #include "efistub.h"
  23
  24 efi_status_t check_platform_features(void)
  25 {
  26         u64 tg;
  27
  28         /* UEFI mandates support for 4 KB granularity, no need to check */
  29         if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
  30                 return EFI_SUCCESS;
  31
  32         tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
  33         if (tg != ID_AA64MMFR0_TGRAN_SUPPORTED) {
  34                 if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
  35                         pr_efi_err("This 64 KB granular kernel is not supported by your CPU\n");
  36                 else
  37                         pr_efi_err("This 16 KB granular kernel is not supported by your CPU\n");
  38                 return EFI_UNSUPPORTED;
  39         }
  40         return EFI_SUCCESS;
  41 }
  42
  43 efi_status_t handle_kernel_image(unsigned long *image_addr,
  44                                  unsigned long *image_size,
  45                                  unsigned long *reserve_addr,
  46                                  unsigned long *reserve_size,
  47                                  unsigned long dram_base,
  48                                  efi_loaded_image_t *image)
  49 {
  50         efi_status_t status;
  51         unsigned long kernel_size, kernel_memsize = 0;
  52         void *old_image_addr = (void *)*image_addr;
  53         unsigned long preferred_offset;
  54         u64 phys_seed = 0;
  55
  56         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
  57                 if (!nokaslr()) {
  58                         status = efi_get_random_bytes(sizeof(phys_seed),
  59                                                       (u8 *)&phys_seed);
  60                         if (status == EFI_NOT_FOUND) {
  61                                 pr_efi("EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
  62                         } else if (status != EFI_SUCCESS) {
  63                                 pr_efi_err("efi_get_random_bytes() failed\n");
  64                                 return status;
  65                         }
  66                 } else {
  67                         pr_efi("KASLR disabled on kernel command line\n");
  68                 }
  69         }
  70
  71         /*
  72          * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
  73          * a 2 MB aligned base, which itself may be lower than dram_base, as
  74          * long as the resulting offset equals or exceeds it.
  75          */
  76         preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
  77         if (preferred_offset < dram_base)
  78                 preferred_offset += MIN_KIMG_ALIGN;
  79
  80         kernel_size = _edata - _text;
  81         kernel_memsize = kernel_size + (_end - _edata);
  82
  83         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
  84                 /*
  85                  * If CONFIG_DEBUG_ALIGN_RODATA is not set, produce a
  86                  * displacement in the interval [0, MIN_KIMG_ALIGN) that
  87                  * doesn't violate this kernel's de-facto alignment
  88                  * constraints.
  89                  */
  90                 u32 mask = (MIN_KIMG_ALIGN - 1) & ~(EFI_KIMG_ALIGN - 1);
  91                 u32 offset = !IS_ENABLED(CONFIG_DEBUG_ALIGN_RODATA) ?
  92                              (phys_seed >> 32) & mask : TEXT_OFFSET;
  93
  94                 /*
  95                  * With CONFIG_RANDOMIZE_TEXT_OFFSET=y, TEXT_OFFSET may not
  96                  * be a multiple of EFI_KIMG_ALIGN, and we must ensure that
  97                  * we preserve the misalignment of 'offset' relative to
  98                  * EFI_KIMG_ALIGN so that statically allocated objects whose
  99                  * alignment exceeds PAGE_SIZE appear correctly aligned in
 100                  * memory.
 101                  */
 102                 offset |= TEXT_OFFSET % EFI_KIMG_ALIGN;
 103
 104                 /*
 105                  * If KASLR is enabled, and we have some randomness available,
 106                  * locate the kernel at a randomized offset in physical memory.
 107                  */
 108                 *reserve_size = kernel_memsize + offset;
 109                 status = efi_random_alloc(*reserve_size,
 110                                           MIN_KIMG_ALIGN, reserve_addr,
 111                                           (u32)phys_seed);
 112
 113                 *image_addr = *reserve_addr + offset;
 114         } else {
 115                 /*
 116                  * Else, try a straight allocation at the preferred offset.
 117                  * This will work around the issue where, if dram_base == 0x0,
 118                  * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
 119                  * address of the allocation to be mistaken for a FAIL return
 120                  * value or a NULL pointer). It will also ensure that, on
 121                  * platforms where the [dram_base, dram_base + TEXT_OFFSET)
 122                  * interval is partially occupied by the firmware (like on APM
 123                  * Mustang), we can still place the kernel at the address
 124                  * 'dram_base + TEXT_OFFSET'.
 125                  */
 126                 if (*image_addr == preferred_offset)
 127                         return EFI_SUCCESS;
 128
 129                 *image_addr = *reserve_addr = preferred_offset;
 130                 *reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
 131
 132                 status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
 133                                      EFI_LOADER_DATA,
 134                                      *reserve_size / EFI_PAGE_SIZE,
 135                                      (efi_physical_addr_t *)reserve_addr);
 136         }
 137
 138         if (status != EFI_SUCCESS) {
 139                 *reserve_size = kernel_memsize + TEXT_OFFSET;
 140                 status = efi_low_alloc(*reserve_size,
 141                                        MIN_KIMG_ALIGN, reserve_addr);
 142
 143                 if (status != EFI_SUCCESS) {
 144                         pr_efi_err("Failed to relocate kernel\n");
 145                         *reserve_size = 0;
 146                         return status;
 147                 }
 148                 *image_addr = *reserve_addr + TEXT_OFFSET;
 149         }
 150         memcpy((void *)*image_addr, old_image_addr, kernel_size);
 151
 152         return EFI_SUCCESS;
 153 }