arch/riscv/kernel/elf_kexec.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Load ELF vmlinux file for the kexec_file_load syscall.
   4  *
   5  * Copyright (C) 2021 Huawei Technologies Co, Ltd.
   6  *
   7  * Author: Liao Chang (liaochang1@huawei.com)
   8  *
   9  * Based on kexec-tools' kexec-elf-riscv.c, heavily modified
  10  * for kernel.
  11  */
  12
  13 #define pr_fmt(fmt)     "kexec_image: " fmt
  14
  15 #include <linux/elf.h>
  16 #include <linux/kexec.h>
  17 #include <linux/slab.h>
  18 #include <linux/of.h>
  19 #include <linux/libfdt.h>
  20 #include <linux/types.h>
  21 #include <linux/memblock.h>
  22 #include <asm/setup.h>
  23
  24 int arch_kimage_file_post_load_cleanup(struct kimage *image)
  25 {
  26         kvfree(image->arch.fdt);
  27         image->arch.fdt = NULL;
  28
  29         vfree(image->elf_headers);
  30         image->elf_headers = NULL;
  31         image->elf_headers_sz = 0;
  32
  33         return kexec_image_post_load_cleanup_default(image);
  34 }
  35
  36 static int riscv_kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
  37                                 struct kexec_elf_info *elf_info, unsigned long old_pbase,
  38                                 unsigned long new_pbase)
  39 {
  40         int i;
  41         int ret = 0;
  42         size_t size;
  43         struct kexec_buf kbuf;
  44         const struct elf_phdr *phdr;
  45
  46         kbuf.image = image;
  47
  48         for (i = 0; i < ehdr->e_phnum; i++) {
  49                 phdr = &elf_info->proghdrs[i];
  50                 if (phdr->p_type != PT_LOAD)
  51                         continue;
  52
  53                 size = phdr->p_filesz;
  54                 if (size > phdr->p_memsz)
  55                         size = phdr->p_memsz;
  56
  57                 kbuf.buffer = (void *) elf_info->buffer + phdr->p_offset;
  58                 kbuf.bufsz = size;
  59                 kbuf.buf_align = phdr->p_align;
  60                 kbuf.mem = phdr->p_paddr - old_pbase + new_pbase;
  61                 kbuf.memsz = phdr->p_memsz;
  62                 kbuf.top_down = false;
  63                 ret = kexec_add_buffer(&kbuf);
  64                 if (ret)
  65                         break;
  66         }
  67
  68         return ret;
  69 }
  70
  71 /*
  72  * Go through the available phsyical memory regions and find one that hold
  73  * an image of the specified size.
  74  */
  75 static int elf_find_pbase(struct kimage *image, unsigned long kernel_len,
  76                           struct elfhdr *ehdr, struct kexec_elf_info *elf_info,
  77                           unsigned long *old_pbase, unsigned long *new_pbase)
  78 {
  79         int i;
  80         int ret;
  81         struct kexec_buf kbuf;
  82         const struct elf_phdr *phdr;
  83         unsigned long lowest_paddr = ULONG_MAX;
  84         unsigned long lowest_vaddr = ULONG_MAX;
  85
  86         for (i = 0; i < ehdr->e_phnum; i++) {
  87                 phdr = &elf_info->proghdrs[i];
  88                 if (phdr->p_type != PT_LOAD)
  89                         continue;
  90
  91                 if (lowest_paddr > phdr->p_paddr)
  92                         lowest_paddr = phdr->p_paddr;
  93
  94                 if (lowest_vaddr > phdr->p_vaddr)
  95                         lowest_vaddr = phdr->p_vaddr;
  96         }
  97
  98         kbuf.image = image;
  99         kbuf.buf_min = lowest_paddr;
 100         kbuf.buf_max = ULONG_MAX;
 101
 102         /*
 103          * Current riscv boot protocol requires 2MB alignment for
 104          * RV64 and 4MB alignment for RV32
 105          *
 106          */
 107         kbuf.buf_align = PMD_SIZE;
 108         kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 109         kbuf.memsz = ALIGN(kernel_len, PAGE_SIZE);
 110         kbuf.top_down = false;
 111         ret = arch_kexec_locate_mem_hole(&kbuf);
 112         if (!ret) {
 113                 *old_pbase = lowest_paddr;
 114                 *new_pbase = kbuf.mem;
 115                 image->start = ehdr->e_entry - lowest_vaddr + kbuf.mem;
 116         }
 117         return ret;
 118 }
 119
 120 static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
 121 {
 122         unsigned int *nr_ranges = arg;
 123
 124         (*nr_ranges)++;
 125         return 0;
 126 }
 127
 128 static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 129 {
 130         struct crash_mem *cmem = arg;
 131
 132         cmem->ranges[cmem->nr_ranges].start = res->start;
 133         cmem->ranges[cmem->nr_ranges].end = res->end;
 134         cmem->nr_ranges++;
 135
 136         return 0;
 137 }
 138
 139 static int prepare_elf_headers(void **addr, unsigned long *sz)
 140 {
 141         struct crash_mem *cmem;
 142         unsigned int nr_ranges;
 143         int ret;
 144
 145         nr_ranges = 1; /* For exclusion of crashkernel region */
 146         walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
 147
 148         cmem = kmalloc(struct_size(cmem, ranges, nr_ranges), GFP_KERNEL);
 149         if (!cmem)
 150                 return -ENOMEM;
 151
 152         cmem->max_nr_ranges = nr_ranges;
 153         cmem->nr_ranges = 0;
 154         ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
 155         if (ret)
 156                 goto out;
 157
 158         /* Exclude crashkernel region */
 159         ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
 160         if (!ret)
 161                 ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
 162
 163 out:
 164         kfree(cmem);
 165         return ret;
 166 }
 167
 168 static char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
 169                                  unsigned long cmdline_len)
 170 {
 171         int elfcorehdr_strlen;
 172         char *cmdline_ptr;
 173
 174         cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
 175         if (!cmdline_ptr)
 176                 return NULL;
 177
 178         elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
 179                 image->elf_load_addr);
 180
 181         if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
 182                 pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
 183                 kfree(cmdline_ptr);
 184                 return NULL;
 185         }
 186
 187         memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
 188         /* Ensure it's nul terminated */
 189         cmdline_ptr[COMMAND_LINE_SIZE - 1] = '\0';
 190         return cmdline_ptr;
 191 }
 192
 193 static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
 194                             unsigned long kernel_len, char *initrd,
 195                             unsigned long initrd_len, char *cmdline,
 196                             unsigned long cmdline_len)
 197 {
 198         int ret;
 199         unsigned long old_kernel_pbase = ULONG_MAX;
 200         unsigned long new_kernel_pbase = 0UL;
 201         unsigned long initrd_pbase = 0UL;
 202         unsigned long headers_sz;
 203         unsigned long kernel_start;
 204         void *fdt, *headers;
 205         struct elfhdr ehdr;
 206         struct kexec_buf kbuf;
 207         struct kexec_elf_info elf_info;
 208         char *modified_cmdline = NULL;
 209
 210         ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info);
 211         if (ret)
 212                 return ERR_PTR(ret);
 213
 214         ret = elf_find_pbase(image, kernel_len, &ehdr, &elf_info,
 215                              &old_kernel_pbase, &new_kernel_pbase);
 216         if (ret)
 217                 goto out;
 218         kernel_start = image->start;
 219         pr_notice("The entry point of kernel at 0x%lx\n", image->start);
 220
 221         /* Add the kernel binary to the image */
 222         ret = riscv_kexec_elf_load(image, &ehdr, &elf_info,
 223                                    old_kernel_pbase, new_kernel_pbase);
 224         if (ret)
 225                 goto out;
 226
 227         kbuf.image = image;
 228         kbuf.buf_min = new_kernel_pbase + kernel_len;
 229         kbuf.buf_max = ULONG_MAX;
 230
 231         /* Add elfcorehdr */
 232         if (image->type == KEXEC_TYPE_CRASH) {
 233                 ret = prepare_elf_headers(&headers, &headers_sz);
 234                 if (ret) {
 235                         pr_err("Preparing elf core header failed\n");
 236                         goto out;
 237                 }
 238
 239                 kbuf.buffer = headers;
 240                 kbuf.bufsz = headers_sz;
 241                 kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 242                 kbuf.memsz = headers_sz;
 243                 kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
 244                 kbuf.top_down = true;
 245
 246                 ret = kexec_add_buffer(&kbuf);
 247                 if (ret) {
 248                         vfree(headers);
 249                         goto out;
 250                 }
 251                 image->elf_headers = headers;
 252                 image->elf_load_addr = kbuf.mem;
 253                 image->elf_headers_sz = headers_sz;
 254
 255                 pr_debug("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
 256                          image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
 257
 258                 /* Setup cmdline for kdump kernel case */
 259                 modified_cmdline = setup_kdump_cmdline(image, cmdline,
 260                                                        cmdline_len);
 261                 if (!modified_cmdline) {
 262                         pr_err("Setting up cmdline for kdump kernel failed\n");
 263                         ret = -EINVAL;
 264                         goto out;
 265                 }
 266                 cmdline = modified_cmdline;
 267         }
 268
 269 #ifdef CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY
 270         /* Add purgatory to the image */
 271         kbuf.top_down = true;
 272         kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 273         ret = kexec_load_purgatory(image, &kbuf);
 274         if (ret) {
 275                 pr_err("Error loading purgatory ret=%d\n", ret);
 276                 goto out;
 277         }
 278         ret = kexec_purgatory_get_set_symbol(image, "riscv_kernel_entry",
 279                                              &kernel_start,
 280                                              sizeof(kernel_start), 0);
 281         if (ret)
 282                 pr_err("Error update purgatory ret=%d\n", ret);
 283 #endif /* CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY */
 284
 285         /* Add the initrd to the image */
 286         if (initrd != NULL) {
 287                 kbuf.buffer = initrd;
 288                 kbuf.bufsz = kbuf.memsz = initrd_len;
 289                 kbuf.buf_align = PAGE_SIZE;
 290                 kbuf.top_down = true;
 291                 kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 292                 ret = kexec_add_buffer(&kbuf);
 293                 if (ret)
 294                         goto out;
 295                 initrd_pbase = kbuf.mem;
 296                 pr_notice("Loaded initrd at 0x%lx\n", initrd_pbase);
 297         }
 298
 299         /* Add the DTB to the image */
 300         fdt = of_kexec_alloc_and_setup_fdt(image, initrd_pbase,
 301                                            initrd_len, cmdline, 0);
 302         if (!fdt) {
 303                 pr_err("Error setting up the new device tree.\n");
 304                 ret = -EINVAL;
 305                 goto out;
 306         }
 307
 308         fdt_pack(fdt);
 309         kbuf.buffer = fdt;
 310         kbuf.bufsz = kbuf.memsz = fdt_totalsize(fdt);
 311         kbuf.buf_align = PAGE_SIZE;
 312         kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 313         kbuf.top_down = true;
 314         ret = kexec_add_buffer(&kbuf);
 315         if (ret) {
 316                 pr_err("Error add DTB kbuf ret=%d\n", ret);
 317                 goto out_free_fdt;
 318         }
 319         /* Cache the fdt buffer address for memory cleanup */
 320         image->arch.fdt = fdt;
 321         pr_notice("Loaded device tree at 0x%lx\n", kbuf.mem);
 322         goto out;
 323
 324 out_free_fdt:
 325         kvfree(fdt);
 326 out:
 327         kfree(modified_cmdline);
 328         kexec_free_elf_info(&elf_info);
 329         return ret ? ERR_PTR(ret) : NULL;
 330 }
 331
 332 #define RV_X(x, s, n)  (((x) >> (s)) & ((1 << (n)) - 1))
 333 #define RISCV_IMM_BITS 12
 334 #define RISCV_IMM_REACH (1LL << RISCV_IMM_BITS)
 335 #define RISCV_CONST_HIGH_PART(x) \
 336         (((x) + (RISCV_IMM_REACH >> 1)) & ~(RISCV_IMM_REACH - 1))
 337 #define RISCV_CONST_LOW_PART(x) ((x) - RISCV_CONST_HIGH_PART(x))
 338
 339 #define ENCODE_ITYPE_IMM(x) \
 340         (RV_X(x, 0, 12) << 20)
 341 #define ENCODE_BTYPE_IMM(x) \
 342         ((RV_X(x, 1, 4) << 8) | (RV_X(x, 5, 6) << 25) | \
 343         (RV_X(x, 11, 1) << 7) | (RV_X(x, 12, 1) << 31))
 344 #define ENCODE_UTYPE_IMM(x) \
 345         (RV_X(x, 12, 20) << 12)
 346 #define ENCODE_JTYPE_IMM(x) \
 347         ((RV_X(x, 1, 10) << 21) | (RV_X(x, 11, 1) << 20) | \
 348         (RV_X(x, 12, 8) << 12) | (RV_X(x, 20, 1) << 31))
 349 #define ENCODE_CBTYPE_IMM(x) \
 350         ((RV_X(x, 1, 2) << 3) | (RV_X(x, 3, 2) << 10) | (RV_X(x, 5, 1) << 2) | \
 351         (RV_X(x, 6, 2) << 5) | (RV_X(x, 8, 1) << 12))
 352 #define ENCODE_CJTYPE_IMM(x) \
 353         ((RV_X(x, 1, 3) << 3) | (RV_X(x, 4, 1) << 11) | (RV_X(x, 5, 1) << 2) | \
 354         (RV_X(x, 6, 1) << 7) | (RV_X(x, 7, 1) << 6) | (RV_X(x, 8, 2) << 9) | \
 355         (RV_X(x, 10, 1) << 8) | (RV_X(x, 11, 1) << 12))
 356 #define ENCODE_UJTYPE_IMM(x) \
 357         (ENCODE_UTYPE_IMM(RISCV_CONST_HIGH_PART(x)) | \
 358         (ENCODE_ITYPE_IMM(RISCV_CONST_LOW_PART(x)) << 32))
 359 #define ENCODE_UITYPE_IMM(x) \
 360         (ENCODE_UTYPE_IMM(x) | (ENCODE_ITYPE_IMM(x) << 32))
 361
 362 #define CLEAN_IMM(type, x) \
 363         ((~ENCODE_##type##_IMM((uint64_t)(-1))) & (x))
 364
 365 int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
 366                                      Elf_Shdr *section,
 367                                      const Elf_Shdr *relsec,
 368                                      const Elf_Shdr *symtab)
 369 {
 370         const char *strtab, *name, *shstrtab;
 371         const Elf_Shdr *sechdrs;
 372         Elf64_Rela *relas;
 373         int i, r_type;
 374
 375         /* String & section header string table */
 376         sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff;
 377         strtab = (char *)pi->ehdr + sechdrs[symtab->sh_link].sh_offset;
 378         shstrtab = (char *)pi->ehdr + sechdrs[pi->ehdr->e_shstrndx].sh_offset;
 379
 380         relas = (void *)pi->ehdr + relsec->sh_offset;
 381
 382         for (i = 0; i < relsec->sh_size / sizeof(*relas); i++) {
 383                 const Elf_Sym *sym;     /* symbol to relocate */
 384                 unsigned long addr;     /* final location after relocation */
 385                 unsigned long val;      /* relocated symbol value */
 386                 unsigned long sec_base; /* relocated symbol value */
 387                 void *loc;              /* tmp location to modify */
 388
 389                 sym = (void *)pi->ehdr + symtab->sh_offset;
 390                 sym += ELF64_R_SYM(relas[i].r_info);
 391
 392                 if (sym->st_name)
 393                         name = strtab + sym->st_name;
 394                 else
 395                         name = shstrtab + sechdrs[sym->st_shndx].sh_name;
 396
 397                 loc = pi->purgatory_buf;
 398                 loc += section->sh_offset;
 399                 loc += relas[i].r_offset;
 400
 401                 if (sym->st_shndx == SHN_ABS)
 402                         sec_base = 0;
 403                 else if (sym->st_shndx >= pi->ehdr->e_shnum) {
 404                         pr_err("Invalid section %d for symbol %s\n",
 405                                sym->st_shndx, name);
 406                         return -ENOEXEC;
 407                 } else
 408                         sec_base = pi->sechdrs[sym->st_shndx].sh_addr;
 409
 410                 val = sym->st_value;
 411                 val += sec_base;
 412                 val += relas[i].r_addend;
 413
 414                 addr = section->sh_addr + relas[i].r_offset;
 415
 416                 r_type = ELF64_R_TYPE(relas[i].r_info);
 417
 418                 switch (r_type) {
 419                 case R_RISCV_BRANCH:
 420                         *(u32 *)loc = CLEAN_IMM(BTYPE, *(u32 *)loc) |
 421                                  ENCODE_BTYPE_IMM(val - addr);
 422                         break;
 423                 case R_RISCV_JAL:
 424                         *(u32 *)loc = CLEAN_IMM(JTYPE, *(u32 *)loc) |
 425                                  ENCODE_JTYPE_IMM(val - addr);
 426                         break;
 427                 /*
 428                  * With no R_RISCV_PCREL_LO12_S, R_RISCV_PCREL_LO12_I
 429                  * sym is expected to be next to R_RISCV_PCREL_HI20
 430                  * in purgatory relsec. Handle it like R_RISCV_CALL
 431                  * sym, instead of searching the whole relsec.
 432                  */
 433                 case R_RISCV_PCREL_HI20:
 434                 case R_RISCV_CALL_PLT:
 435                 case R_RISCV_CALL:
 436                         *(u64 *)loc = CLEAN_IMM(UITYPE, *(u64 *)loc) |
 437                                  ENCODE_UJTYPE_IMM(val - addr);
 438                         break;
 439                 case R_RISCV_RVC_BRANCH:
 440                         *(u32 *)loc = CLEAN_IMM(CBTYPE, *(u32 *)loc) |
 441                                  ENCODE_CBTYPE_IMM(val - addr);
 442                         break;
 443                 case R_RISCV_RVC_JUMP:
 444                         *(u32 *)loc = CLEAN_IMM(CJTYPE, *(u32 *)loc) |
 445                                  ENCODE_CJTYPE_IMM(val - addr);
 446                         break;
 447                 case R_RISCV_ADD32:
 448                         *(u32 *)loc += val;
 449                         break;
 450                 case R_RISCV_SUB32:
 451                         *(u32 *)loc -= val;
 452                         break;
 453                 /* It has been applied by R_RISCV_PCREL_HI20 sym */
 454                 case R_RISCV_PCREL_LO12_I:
 455                 case R_RISCV_ALIGN:
 456                 case R_RISCV_RELAX:
 457                         break;
 458                 default:
 459                         pr_err("Unknown rela relocation: %d\n", r_type);
 460                         return -ENOEXEC;
 461                 }
 462         }
 463         return 0;
 464 }
 465
 466 const struct kexec_file_ops elf_kexec_ops = {
 467         .probe = kexec_elf_probe,
 468         .load  = elf_kexec_load,
 469 };