root/drivers/firmware/efi/libstub/arm-stub.c

DEFINITIONS

1. efi_char16_printk
2. setup_graphics
3. install_memreserve_table
4. efi_entry
5. cmp_mem_desc
6. regions_are_adjacent
7. regions_have_compatible_memory_type_attrs
8. efi_get_virtmap

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * EFI stub implementation that is shared by arm and arm64 architectures.
   4  * This should be #included by the EFI stub implementation files.
   5  *
   6  * Copyright (C) 2013,2014 Linaro Limited
   7  *     Roy Franz <roy.franz@linaro.org
   8  * Copyright (C) 2013 Red Hat, Inc.
   9  *     Mark Salter <msalter@redhat.com>
  10  */
  11 
  12 #include <linux/efi.h>
  13 #include <linux/sort.h>
  14 #include <asm/efi.h>
  15 
  16 #include "efistub.h"
  17 
  18 /*
  19  * This is the base address at which to start allocating virtual memory ranges
  20  * for UEFI Runtime Services. This is in the low TTBR0 range so that we can use
  21  * any allocation we choose, and eliminate the risk of a conflict after kexec.
  22  * The value chosen is the largest non-zero power of 2 suitable for this purpose
  23  * both on 32-bit and 64-bit ARM CPUs, to maximize the likelihood that it can
  24  * be mapped efficiently.
  25  * Since 32-bit ARM could potentially execute with a 1G/3G user/kernel split,
  26  * map everything below 1 GB. (512 MB is a reasonable upper bound for the
  27  * entire footprint of the UEFI runtime services memory regions)
  28  */
  29 #define EFI_RT_VIRTUAL_BASE     SZ_512M
  30 #define EFI_RT_VIRTUAL_SIZE     SZ_512M
  31 
  32 #ifdef CONFIG_ARM64
  33 # define EFI_RT_VIRTUAL_LIMIT   DEFAULT_MAP_WINDOW_64
  34 #else
  35 # define EFI_RT_VIRTUAL_LIMIT   TASK_SIZE
  36 #endif
  37 
  38 static u64 virtmap_base = EFI_RT_VIRTUAL_BASE;
  39 
  40 void efi_char16_printk(efi_system_table_t *sys_table_arg,
  41                               efi_char16_t *str)
  42 {
  43         struct efi_simple_text_output_protocol *out;
  44 
  45         out = (struct efi_simple_text_output_protocol *)sys_table_arg->con_out;
  46         out->output_string(out, str);
  47 }
  48 
  49 static struct screen_info *setup_graphics(efi_system_table_t *sys_table_arg)
  50 {
  51         efi_guid_t gop_proto = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
  52         efi_status_t status;
  53         unsigned long size;
  54         void **gop_handle = NULL;
  55         struct screen_info *si = NULL;
  56 
  57         size = 0;
  58         status = efi_call_early(locate_handle, EFI_LOCATE_BY_PROTOCOL,
  59                                 &gop_proto, NULL, &size, gop_handle);
  60         if (status == EFI_BUFFER_TOO_SMALL) {
  61                 si = alloc_screen_info(sys_table_arg);
  62                 if (!si)
  63                         return NULL;
  64                 efi_setup_gop(sys_table_arg, si, &gop_proto, size);
  65         }
  66         return si;
  67 }
  68 
  69 void install_memreserve_table(efi_system_table_t *sys_table_arg)
  70 {
  71         struct linux_efi_memreserve *rsv;
  72         efi_guid_t memreserve_table_guid = LINUX_EFI_MEMRESERVE_TABLE_GUID;
  73         efi_status_t status;
  74 
  75         status = efi_call_early(allocate_pool, EFI_LOADER_DATA, sizeof(*rsv),
  76                                 (void **)&rsv);
  77         if (status != EFI_SUCCESS) {
  78                 pr_efi_err(sys_table_arg, "Failed to allocate memreserve entry!\n");
  79                 return;
  80         }
  81 
  82         rsv->next = 0;
  83         rsv->size = 0;
  84         atomic_set(&rsv->count, 0);
  85 
  86         status = efi_call_early(install_configuration_table,
  87                                 &memreserve_table_guid,
  88                                 rsv);
  89         if (status != EFI_SUCCESS)
  90                 pr_efi_err(sys_table_arg, "Failed to install memreserve config table!\n");
  91 }
  92 
  93 
  94 /*
  95  * This function handles the architcture specific differences between arm and
  96  * arm64 regarding where the kernel image must be loaded and any memory that
  97  * must be reserved. On failure it is required to free all
  98  * all allocations it has made.
  99  */
 100 efi_status_t handle_kernel_image(efi_system_table_t *sys_table,
 101                                  unsigned long *image_addr,
 102                                  unsigned long *image_size,
 103                                  unsigned long *reserve_addr,
 104                                  unsigned long *reserve_size,
 105                                  unsigned long dram_base,
 106                                  efi_loaded_image_t *image);
 107 /*
 108  * EFI entry point for the arm/arm64 EFI stubs.  This is the entrypoint
 109  * that is described in the PE/COFF header.  Most of the code is the same
 110  * for both archictectures, with the arch-specific code provided in the
 111  * handle_kernel_image() function.
 112  */
 113 unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
 114                                unsigned long *image_addr)
 115 {
 116         efi_loaded_image_t *image;
 117         efi_status_t status;
 118         unsigned long image_size = 0;
 119         unsigned long dram_base;
 120         /* addr/point and size pairs for memory management*/
 121         unsigned long initrd_addr;
 122         u64 initrd_size = 0;
 123         unsigned long fdt_addr = 0;  /* Original DTB */
 124         unsigned long fdt_size = 0;
 125         char *cmdline_ptr = NULL;
 126         int cmdline_size = 0;
 127         unsigned long new_fdt_addr;
 128         efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID;
 129         unsigned long reserve_addr = 0;
 130         unsigned long reserve_size = 0;
 131         enum efi_secureboot_mode secure_boot;
 132         struct screen_info *si;
 133 
 134         /* Check if we were booted by the EFI firmware */
 135         if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
 136                 goto fail;
 137 
 138         status = check_platform_features(sys_table);
 139         if (status != EFI_SUCCESS)
 140                 goto fail;
 141 
 142         /*
 143          * Get a handle to the loaded image protocol.  This is used to get
 144          * information about the running image, such as size and the command
 145          * line.
 146          */
 147         status = sys_table->boottime->handle_protocol(handle,
 148                                         &loaded_image_proto, (void *)&image);
 149         if (status != EFI_SUCCESS) {
 150                 pr_efi_err(sys_table, "Failed to get loaded image protocol\n");
 151                 goto fail;
 152         }
 153 
 154         dram_base = get_dram_base(sys_table);
 155         if (dram_base == EFI_ERROR) {
 156                 pr_efi_err(sys_table, "Failed to find DRAM base\n");
 157                 goto fail;
 158         }
 159 
 160         /*
 161          * Get the command line from EFI, using the LOADED_IMAGE
 162          * protocol. We are going to copy the command line into the
 163          * device tree, so this can be allocated anywhere.
 164          */
 165         cmdline_ptr = efi_convert_cmdline(sys_table, image, &cmdline_size);
 166         if (!cmdline_ptr) {
 167                 pr_efi_err(sys_table, "getting command line via LOADED_IMAGE_PROTOCOL\n");
 168                 goto fail;
 169         }
 170 
 171         if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
 172             IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
 173             cmdline_size == 0)
 174                 efi_parse_options(CONFIG_CMDLINE);
 175 
 176         if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && cmdline_size > 0)
 177                 efi_parse_options(cmdline_ptr);
 178 
 179         pr_efi(sys_table, "Booting Linux Kernel...\n");
 180 
 181         si = setup_graphics(sys_table);
 182 
 183         status = handle_kernel_image(sys_table, image_addr, &image_size,
 184                                      &reserve_addr,
 185                                      &reserve_size,
 186                                      dram_base, image);
 187         if (status != EFI_SUCCESS) {
 188                 pr_efi_err(sys_table, "Failed to relocate kernel\n");
 189                 goto fail_free_cmdline;
 190         }
 191 
 192         /* Ask the firmware to clear memory on unclean shutdown */
 193         efi_enable_reset_attack_mitigation(sys_table);
 194 
 195         secure_boot = efi_get_secureboot(sys_table);
 196 
 197         /*
 198          * Unauthenticated device tree data is a security hazard, so ignore
 199          * 'dtb=' unless UEFI Secure Boot is disabled.  We assume that secure
 200          * boot is enabled if we can't determine its state.
 201          */
 202         if (!IS_ENABLED(CONFIG_EFI_ARMSTUB_DTB_LOADER) ||
 203              secure_boot != efi_secureboot_mode_disabled) {
 204                 if (strstr(cmdline_ptr, "dtb="))
 205                         pr_efi(sys_table, "Ignoring DTB from command line.\n");
 206         } else {
 207                 status = handle_cmdline_files(sys_table, image, cmdline_ptr,
 208                                               "dtb=",
 209                                               ~0UL, &fdt_addr, &fdt_size);
 210 
 211                 if (status != EFI_SUCCESS) {
 212                         pr_efi_err(sys_table, "Failed to load device tree!\n");
 213                         goto fail_free_image;
 214                 }
 215         }
 216 
 217         if (fdt_addr) {
 218                 pr_efi(sys_table, "Using DTB from command line\n");
 219         } else {
 220                 /* Look for a device tree configuration table entry. */
 221                 fdt_addr = (uintptr_t)get_fdt(sys_table, &fdt_size);
 222                 if (fdt_addr)
 223                         pr_efi(sys_table, "Using DTB from configuration table\n");
 224         }
 225 
 226         if (!fdt_addr)
 227                 pr_efi(sys_table, "Generating empty DTB\n");
 228 
 229         status = handle_cmdline_files(sys_table, image, cmdline_ptr, "initrd=",
 230                                       efi_get_max_initrd_addr(dram_base,
 231                                                               *image_addr),
 232                                       (unsigned long *)&initrd_addr,
 233                                       (unsigned long *)&initrd_size);
 234         if (status != EFI_SUCCESS)
 235                 pr_efi_err(sys_table, "Failed initrd from command line!\n");
 236 
 237         efi_random_get_seed(sys_table);
 238 
 239         /* hibernation expects the runtime regions to stay in the same place */
 240         if (!IS_ENABLED(CONFIG_HIBERNATION) && !nokaslr()) {
 241                 /*
 242                  * Randomize the base of the UEFI runtime services region.
 243                  * Preserve the 2 MB alignment of the region by taking a
 244                  * shift of 21 bit positions into account when scaling
 245                  * the headroom value using a 32-bit random value.
 246                  */
 247                 static const u64 headroom = EFI_RT_VIRTUAL_LIMIT -
 248                                             EFI_RT_VIRTUAL_BASE -
 249                                             EFI_RT_VIRTUAL_SIZE;
 250                 u32 rnd;
 251 
 252                 status = efi_get_random_bytes(sys_table, sizeof(rnd),
 253                                               (u8 *)&rnd);
 254                 if (status == EFI_SUCCESS) {
 255                         virtmap_base = EFI_RT_VIRTUAL_BASE +
 256                                        (((headroom >> 21) * rnd) >> (32 - 21));
 257                 }
 258         }
 259 
 260         install_memreserve_table(sys_table);
 261 
 262         new_fdt_addr = fdt_addr;
 263         status = allocate_new_fdt_and_exit_boot(sys_table, handle,
 264                                 &new_fdt_addr, efi_get_max_fdt_addr(dram_base),
 265                                 initrd_addr, initrd_size, cmdline_ptr,
 266                                 fdt_addr, fdt_size);
 267 
 268         /*
 269          * If all went well, we need to return the FDT address to the
 270          * calling function so it can be passed to kernel as part of
 271          * the kernel boot protocol.
 272          */
 273         if (status == EFI_SUCCESS)
 274                 return new_fdt_addr;
 275 
 276         pr_efi_err(sys_table, "Failed to update FDT and exit boot services\n");
 277 
 278         efi_free(sys_table, initrd_size, initrd_addr);
 279         efi_free(sys_table, fdt_size, fdt_addr);
 280 
 281 fail_free_image:
 282         efi_free(sys_table, image_size, *image_addr);
 283         efi_free(sys_table, reserve_size, reserve_addr);
 284 fail_free_cmdline:
 285         free_screen_info(sys_table, si);
 286         efi_free(sys_table, cmdline_size, (unsigned long)cmdline_ptr);
 287 fail:
 288         return EFI_ERROR;
 289 }
 290 
 291 static int cmp_mem_desc(const void *l, const void *r)
 292 {
 293         const efi_memory_desc_t *left = l, *right = r;
 294 
 295         return (left->phys_addr > right->phys_addr) ? 1 : -1;
 296 }
 297 
 298 /*
 299  * Returns whether region @left ends exactly where region @right starts,
 300  * or false if either argument is NULL.
 301  */
 302 static bool regions_are_adjacent(efi_memory_desc_t *left,
 303                                  efi_memory_desc_t *right)
 304 {
 305         u64 left_end;
 306 
 307         if (left == NULL || right == NULL)
 308                 return false;
 309 
 310         left_end = left->phys_addr + left->num_pages * EFI_PAGE_SIZE;
 311 
 312         return left_end == right->phys_addr;
 313 }
 314 
 315 /*
 316  * Returns whether region @left and region @right have compatible memory type
 317  * mapping attributes, and are both EFI_MEMORY_RUNTIME regions.
 318  */
 319 static bool regions_have_compatible_memory_type_attrs(efi_memory_desc_t *left,
 320                                                       efi_memory_desc_t *right)
 321 {
 322         static const u64 mem_type_mask = EFI_MEMORY_WB | EFI_MEMORY_WT |
 323                                          EFI_MEMORY_WC | EFI_MEMORY_UC |
 324                                          EFI_MEMORY_RUNTIME;
 325 
 326         return ((left->attribute ^ right->attribute) & mem_type_mask) == 0;
 327 }
 328 
 329 /*
 330  * efi_get_virtmap() - create a virtual mapping for the EFI memory map
 331  *
 332  * This function populates the virt_addr fields of all memory region descriptors
 333  * in @memory_map whose EFI_MEMORY_RUNTIME attribute is set. Those descriptors
 334  * are also copied to @runtime_map, and their total count is returned in @count.
 335  */
 336 void efi_get_virtmap(efi_memory_desc_t *memory_map, unsigned long map_size,
 337                      unsigned long desc_size, efi_memory_desc_t *runtime_map,
 338                      int *count)
 339 {
 340         u64 efi_virt_base = virtmap_base;
 341         efi_memory_desc_t *in, *prev = NULL, *out = runtime_map;
 342         int l;
 343 
 344         /*
 345          * To work around potential issues with the Properties Table feature
 346          * introduced in UEFI 2.5, which may split PE/COFF executable images
 347          * in memory into several RuntimeServicesCode and RuntimeServicesData
 348          * regions, we need to preserve the relative offsets between adjacent
 349          * EFI_MEMORY_RUNTIME regions with the same memory type attributes.
 350          * The easiest way to find adjacent regions is to sort the memory map
 351          * before traversing it.
 352          */
 353         if (IS_ENABLED(CONFIG_ARM64))
 354                 sort(memory_map, map_size / desc_size, desc_size, cmp_mem_desc,
 355                      NULL);
 356 
 357         for (l = 0; l < map_size; l += desc_size, prev = in) {
 358                 u64 paddr, size;
 359 
 360                 in = (void *)memory_map + l;
 361                 if (!(in->attribute & EFI_MEMORY_RUNTIME))
 362                         continue;
 363 
 364                 paddr = in->phys_addr;
 365                 size = in->num_pages * EFI_PAGE_SIZE;
 366 
 367                 if (novamap()) {
 368                         in->virt_addr = in->phys_addr;
 369                         continue;
 370                 }
 371 
 372                 /*
 373                  * Make the mapping compatible with 64k pages: this allows
 374                  * a 4k page size kernel to kexec a 64k page size kernel and
 375                  * vice versa.
 376                  */
 377                 if ((IS_ENABLED(CONFIG_ARM64) &&
 378                      !regions_are_adjacent(prev, in)) ||
 379                     !regions_have_compatible_memory_type_attrs(prev, in)) {
 380 
 381                         paddr = round_down(in->phys_addr, SZ_64K);
 382                         size += in->phys_addr - paddr;
 383 
 384                         /*
 385                          * Avoid wasting memory on PTEs by choosing a virtual
 386                          * base that is compatible with section mappings if this
 387                          * region has the appropriate size and physical
 388                          * alignment. (Sections are 2 MB on 4k granule kernels)
 389                          */
 390                         if (IS_ALIGNED(in->phys_addr, SZ_2M) && size >= SZ_2M)
 391                                 efi_virt_base = round_up(efi_virt_base, SZ_2M);
 392                         else
 393                                 efi_virt_base = round_up(efi_virt_base, SZ_64K);
 394                 }
 395 
 396                 in->virt_addr = efi_virt_base + in->phys_addr - paddr;
 397                 efi_virt_base += size;
 398 
 399                 memcpy(out, in, desc_size);
 400                 out = (void *)out + desc_size;
 401                 ++*count;
 402         }
 403 }