drivers/of/kexec.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2020 Arm Limited
   4  *
   5  * Based on arch/arm64/kernel/machine_kexec_file.c:
   6  *  Copyright (C) 2018 Linaro Limited
   7  *
   8  * And arch/powerpc/kexec/file_load.c:
   9  *  Copyright (C) 2016  IBM Corporation
  10  */
  11
  12 #include <linux/ima.h>
  13 #include <linux/kernel.h>
  14 #include <linux/kexec.h>
  15 #include <linux/memblock.h>
  16 #include <linux/libfdt.h>
  17 #include <linux/of.h>
  18 #include <linux/of_fdt.h>
  19 #include <linux/random.h>
  20 #include <linux/slab.h>
  21 #include <linux/types.h>
  22
  23 #define RNG_SEED_SIZE           128
  24
  25 /*
  26  * Additional space needed for the FDT buffer so that we can add initrd,
  27  * bootargs, kaslr-seed, rng-seed, useable-memory-range and elfcorehdr.
  28  */
  29 #define FDT_EXTRA_SPACE 0x1000
  30
  31 /**
  32  * fdt_find_and_del_mem_rsv - delete memory reservation with given address and size
  33  *
  34  * @fdt:        Flattened device tree for the current kernel.
  35  * @start:      Starting address of the reserved memory.
  36  * @size:       Size of the reserved memory.
  37  *
  38  * Return: 0 on success, or negative errno on error.
  39  */
  40 static int fdt_find_and_del_mem_rsv(void *fdt, unsigned long start, unsigned long size)
  41 {
  42         int i, ret, num_rsvs = fdt_num_mem_rsv(fdt);
  43
  44         for (i = 0; i < num_rsvs; i++) {
  45                 u64 rsv_start, rsv_size;
  46
  47                 ret = fdt_get_mem_rsv(fdt, i, &rsv_start, &rsv_size);
  48                 if (ret) {
  49                         pr_err("Malformed device tree.\n");
  50                         return -EINVAL;
  51                 }
  52
  53                 if (rsv_start == start && rsv_size == size) {
  54                         ret = fdt_del_mem_rsv(fdt, i);
  55                         if (ret) {
  56                                 pr_err("Error deleting device tree reservation.\n");
  57                                 return -EINVAL;
  58                         }
  59
  60                         return 0;
  61                 }
  62         }
  63
  64         return -ENOENT;
  65 }
  66
  67 /**
  68  * get_addr_size_cells - Get address and size of root node
  69  *
  70  * @addr_cells: Return address of the root node
  71  * @size_cells: Return size of the root node
  72  *
  73  * Return: 0 on success, or negative errno on error.
  74  */
  75 static int get_addr_size_cells(int *addr_cells, int *size_cells)
  76 {
  77         struct device_node *root;
  78
  79         root = of_find_node_by_path("/");
  80         if (!root)
  81                 return -EINVAL;
  82
  83         *addr_cells = of_n_addr_cells(root);
  84         *size_cells = of_n_size_cells(root);
  85
  86         of_node_put(root);
  87
  88         return 0;
  89 }
  90
  91 /**
  92  * do_get_kexec_buffer - Get address and size of device tree property
  93  *
  94  * @prop: Device tree property
  95  * @len: Size of @prop
  96  * @addr: Return address of the node
  97  * @size: Return size of the node
  98  *
  99  * Return: 0 on success, or negative errno on error.
 100  */
 101 static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
 102                                size_t *size)
 103 {
 104         int ret, addr_cells, size_cells;
 105
 106         ret = get_addr_size_cells(&addr_cells, &size_cells);
 107         if (ret)
 108                 return ret;
 109
 110         if (len < 4 * (addr_cells + size_cells))
 111                 return -ENOENT;
 112
 113         *addr = of_read_number(prop, addr_cells);
 114         *size = of_read_number(prop + 4 * addr_cells, size_cells);
 115
 116         return 0;
 117 }
 118
 119 #ifdef CONFIG_HAVE_IMA_KEXEC
 120 /**
 121  * ima_get_kexec_buffer - get IMA buffer from the previous kernel
 122  * @addr:       On successful return, set to point to the buffer contents.
 123  * @size:       On successful return, set to the buffer size.
 124  *
 125  * Return: 0 on success, negative errno on error.
 126  */
 127 int __init ima_get_kexec_buffer(void **addr, size_t *size)
 128 {
 129         int ret, len;
 130         unsigned long tmp_addr;
 131         unsigned long start_pfn, end_pfn;
 132         size_t tmp_size;
 133         const void *prop;
 134
 135         prop = of_get_property(of_chosen, "linux,ima-kexec-buffer", &len);
 136         if (!prop)
 137                 return -ENOENT;
 138
 139         ret = do_get_kexec_buffer(prop, len, &tmp_addr, &tmp_size);
 140         if (ret)
 141                 return ret;
 142
 143         /* Do some sanity on the returned size for the ima-kexec buffer */
 144         if (!tmp_size)
 145                 return -ENOENT;
 146
 147         /*
 148          * Calculate the PFNs for the buffer and ensure
 149          * they are with in addressable memory.
 150          */
 151         start_pfn = PHYS_PFN(tmp_addr);
 152         end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
 153         if (!page_is_ram(start_pfn) || !page_is_ram(end_pfn)) {
 154                 pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
 155                         tmp_addr, tmp_size);
 156                 return -EINVAL;
 157         }
 158
 159         *addr = __va(tmp_addr);
 160         *size = tmp_size;
 161
 162         return 0;
 163 }
 164
 165 /**
 166  * ima_free_kexec_buffer - free memory used by the IMA buffer
 167  */
 168 int __init ima_free_kexec_buffer(void)
 169 {
 170         int ret;
 171         unsigned long addr;
 172         size_t size;
 173         struct property *prop;
 174
 175         prop = of_find_property(of_chosen, "linux,ima-kexec-buffer", NULL);
 176         if (!prop)
 177                 return -ENOENT;
 178
 179         ret = do_get_kexec_buffer(prop->value, prop->length, &addr, &size);
 180         if (ret)
 181                 return ret;
 182
 183         ret = of_remove_property(of_chosen, prop);
 184         if (ret)
 185                 return ret;
 186
 187         return memblock_phys_free(addr, size);
 188 }
 189 #endif
 190
 191 /**
 192  * remove_ima_buffer - remove the IMA buffer property and reservation from @fdt
 193  *
 194  * @fdt: Flattened Device Tree to update
 195  * @chosen_node: Offset to the chosen node in the device tree
 196  *
 197  * The IMA measurement buffer is of no use to a subsequent kernel, so we always
 198  * remove it from the device tree.
 199  */
 200 static void remove_ima_buffer(void *fdt, int chosen_node)
 201 {
 202         int ret, len;
 203         unsigned long addr;
 204         size_t size;
 205         const void *prop;
 206
 207         if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
 208                 return;
 209
 210         prop = fdt_getprop(fdt, chosen_node, "linux,ima-kexec-buffer", &len);
 211         if (!prop)
 212                 return;
 213
 214         ret = do_get_kexec_buffer(prop, len, &addr, &size);
 215         fdt_delprop(fdt, chosen_node, "linux,ima-kexec-buffer");
 216         if (ret)
 217                 return;
 218
 219         ret = fdt_find_and_del_mem_rsv(fdt, addr, size);
 220         if (!ret)
 221                 pr_debug("Removed old IMA buffer reservation.\n");
 222 }
 223
 224 #ifdef CONFIG_IMA_KEXEC
 225 /**
 226  * setup_ima_buffer - add IMA buffer information to the fdt
 227  * @image:              kexec image being loaded.
 228  * @fdt:                Flattened device tree for the next kernel.
 229  * @chosen_node:        Offset to the chosen node.
 230  *
 231  * Return: 0 on success, or negative errno on error.
 232  */
 233 static int setup_ima_buffer(const struct kimage *image, void *fdt,
 234                             int chosen_node)
 235 {
 236         int ret;
 237
 238         if (!image->ima_buffer_size)
 239                 return 0;
 240
 241         ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
 242                                        "linux,ima-kexec-buffer",
 243                                        image->ima_buffer_addr,
 244                                        image->ima_buffer_size);
 245         if (ret < 0)
 246                 return -EINVAL;
 247
 248         ret = fdt_add_mem_rsv(fdt, image->ima_buffer_addr,
 249                               image->ima_buffer_size);
 250         if (ret)
 251                 return -EINVAL;
 252
 253         pr_debug("IMA buffer at 0x%llx, size = 0x%zx\n",
 254                  image->ima_buffer_addr, image->ima_buffer_size);
 255
 256         return 0;
 257 }
 258 #else /* CONFIG_IMA_KEXEC */
 259 static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
 260                                    int chosen_node)
 261 {
 262         return 0;
 263 }
 264 #endif /* CONFIG_IMA_KEXEC */
 265
 266 /*
 267  * of_kexec_alloc_and_setup_fdt - Alloc and setup a new Flattened Device Tree
 268  *
 269  * @image:              kexec image being loaded.
 270  * @initrd_load_addr:   Address where the next initrd will be loaded.
 271  * @initrd_len:         Size of the next initrd, or 0 if there will be none.
 272  * @cmdline:            Command line for the next kernel, or NULL if there will
 273  *                      be none.
 274  * @extra_fdt_size:     Additional size for the new FDT buffer.
 275  *
 276  * Return: fdt on success, or NULL errno on error.
 277  */
 278 void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
 279                                    unsigned long initrd_load_addr,
 280                                    unsigned long initrd_len,
 281                                    const char *cmdline, size_t extra_fdt_size)
 282 {
 283         void *fdt;
 284         int ret, chosen_node, len;
 285         const void *prop;
 286         size_t fdt_size;
 287
 288         fdt_size = fdt_totalsize(initial_boot_params) +
 289                    (cmdline ? strlen(cmdline) : 0) +
 290                    FDT_EXTRA_SPACE +
 291                    extra_fdt_size;
 292         fdt = kvmalloc(fdt_size, GFP_KERNEL);
 293         if (!fdt)
 294                 return NULL;
 295
 296         ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
 297         if (ret < 0) {
 298                 pr_err("Error %d setting up the new device tree.\n", ret);
 299                 goto out;
 300         }
 301
 302         /* Remove memory reservation for the current device tree. */
 303         ret = fdt_find_and_del_mem_rsv(fdt, __pa(initial_boot_params),
 304                                        fdt_totalsize(initial_boot_params));
 305         if (ret == -EINVAL) {
 306                 pr_err("Error removing memory reservation.\n");
 307                 goto out;
 308         }
 309
 310         chosen_node = fdt_path_offset(fdt, "/chosen");
 311         if (chosen_node == -FDT_ERR_NOTFOUND)
 312                 chosen_node = fdt_add_subnode(fdt, fdt_path_offset(fdt, "/"),
 313                                               "chosen");
 314         if (chosen_node < 0) {
 315                 ret = chosen_node;
 316                 goto out;
 317         }
 318
 319         ret = fdt_delprop(fdt, chosen_node, "linux,elfcorehdr");
 320         if (ret && ret != -FDT_ERR_NOTFOUND)
 321                 goto out;
 322         ret = fdt_delprop(fdt, chosen_node, "linux,usable-memory-range");
 323         if (ret && ret != -FDT_ERR_NOTFOUND)
 324                 goto out;
 325
 326         /* Did we boot using an initrd? */
 327         prop = fdt_getprop(fdt, chosen_node, "linux,initrd-start", &len);
 328         if (prop) {
 329                 u64 tmp_start, tmp_end, tmp_size;
 330
 331                 tmp_start = of_read_number(prop, len / 4);
 332
 333                 prop = fdt_getprop(fdt, chosen_node, "linux,initrd-end", &len);
 334                 if (!prop) {
 335                         ret = -EINVAL;
 336                         goto out;
 337                 }
 338
 339                 tmp_end = of_read_number(prop, len / 4);
 340
 341                 /*
 342                  * kexec reserves exact initrd size, while firmware may
 343                  * reserve a multiple of PAGE_SIZE, so check for both.
 344                  */
 345                 tmp_size = tmp_end - tmp_start;
 346                 ret = fdt_find_and_del_mem_rsv(fdt, tmp_start, tmp_size);
 347                 if (ret == -ENOENT)
 348                         ret = fdt_find_and_del_mem_rsv(fdt, tmp_start,
 349                                                        round_up(tmp_size, PAGE_SIZE));
 350                 if (ret == -EINVAL)
 351                         goto out;
 352         }
 353
 354         /* add initrd-* */
 355         if (initrd_load_addr) {
 356                 ret = fdt_setprop_u64(fdt, chosen_node, "linux,initrd-start",
 357                                       initrd_load_addr);
 358                 if (ret)
 359                         goto out;
 360
 361                 ret = fdt_setprop_u64(fdt, chosen_node, "linux,initrd-end",
 362                                       initrd_load_addr + initrd_len);
 363                 if (ret)
 364                         goto out;
 365
 366                 ret = fdt_add_mem_rsv(fdt, initrd_load_addr, initrd_len);
 367                 if (ret)
 368                         goto out;
 369
 370         } else {
 371                 ret = fdt_delprop(fdt, chosen_node, "linux,initrd-start");
 372                 if (ret && (ret != -FDT_ERR_NOTFOUND))
 373                         goto out;
 374
 375                 ret = fdt_delprop(fdt, chosen_node, "linux,initrd-end");
 376                 if (ret && (ret != -FDT_ERR_NOTFOUND))
 377                         goto out;
 378         }
 379
 380         if (image->type == KEXEC_TYPE_CRASH) {
 381                 /* add linux,elfcorehdr */
 382                 ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
 383                                 "linux,elfcorehdr", image->elf_load_addr,
 384                                 image->elf_headers_sz);
 385                 if (ret)
 386                         goto out;
 387
 388                 /*
 389                  * Avoid elfcorehdr from being stomped on in kdump kernel by
 390                  * setting up memory reserve map.
 391                  */
 392                 ret = fdt_add_mem_rsv(fdt, image->elf_load_addr,
 393                                       image->elf_headers_sz);
 394                 if (ret)
 395                         goto out;
 396
 397                 /* add linux,usable-memory-range */
 398                 ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
 399                                 "linux,usable-memory-range", crashk_res.start,
 400                                 crashk_res.end - crashk_res.start + 1);
 401                 if (ret)
 402                         goto out;
 403
 404                 if (crashk_low_res.end) {
 405                         ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
 406                                         "linux,usable-memory-range",
 407                                         crashk_low_res.start,
 408                                         crashk_low_res.end - crashk_low_res.start + 1);
 409                         if (ret)
 410                                 goto out;
 411                 }
 412         }
 413
 414         /* add bootargs */
 415         if (cmdline) {
 416                 ret = fdt_setprop_string(fdt, chosen_node, "bootargs", cmdline);
 417                 if (ret)
 418                         goto out;
 419         } else {
 420                 ret = fdt_delprop(fdt, chosen_node, "bootargs");
 421                 if (ret && (ret != -FDT_ERR_NOTFOUND))
 422                         goto out;
 423         }
 424
 425         /* add kaslr-seed */
 426         ret = fdt_delprop(fdt, chosen_node, "kaslr-seed");
 427         if (ret == -FDT_ERR_NOTFOUND)
 428                 ret = 0;
 429         else if (ret)
 430                 goto out;
 431
 432         if (rng_is_initialized()) {
 433                 u64 seed = get_random_u64();
 434
 435                 ret = fdt_setprop_u64(fdt, chosen_node, "kaslr-seed", seed);
 436                 if (ret)
 437                         goto out;
 438         } else {
 439                 pr_notice("RNG is not initialised: omitting \"%s\" property\n",
 440                           "kaslr-seed");
 441         }
 442
 443         /* add rng-seed */
 444         if (rng_is_initialized()) {
 445                 void *rng_seed;
 446
 447                 ret = fdt_setprop_placeholder(fdt, chosen_node, "rng-seed",
 448                                 RNG_SEED_SIZE, &rng_seed);
 449                 if (ret)
 450                         goto out;
 451                 get_random_bytes(rng_seed, RNG_SEED_SIZE);
 452         } else {
 453                 pr_notice("RNG is not initialised: omitting \"%s\" property\n",
 454                           "rng-seed");
 455         }
 456
 457         ret = fdt_setprop(fdt, chosen_node, "linux,booted-from-kexec", NULL, 0);
 458         if (ret)
 459                 goto out;
 460
 461         remove_ima_buffer(fdt, chosen_node);
 462         ret = setup_ima_buffer(image, fdt, fdt_path_offset(fdt, "/chosen"));
 463
 464 out:
 465         if (ret) {
 466                 kvfree(fdt);
 467                 fdt = NULL;
 468         }
 469
 470         return fdt;
 471 }