arch/mips/vdso/genvdso.c

   1 /*
   2  * Copyright (C) 2015 Imagination Technologies
   3  * Author: Alex Smith <alex.smith@imgtec.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the
   7  * Free Software Foundation;  either version 2 of the  License, or (at your
   8  * option) any later version.
   9  */
  10
  11 /*
  12  * This tool is used to generate the real VDSO images from the raw image. It
  13  * first patches up the MIPS ABI flags and GNU attributes sections defined in
  14  * elf.S to have the correct name and type. It then generates a C source file
  15  * to be compiled into the kernel containing the VDSO image data and a
  16  * mips_vdso_image struct for it, including symbol offsets extracted from the
  17  * image.
  18  *
  19  * We need to be passed both a stripped and unstripped VDSO image. The stripped
  20  * image is compiled into the kernel, but we must also patch up the unstripped
  21  * image's ABI flags sections so that it can be installed and used for
  22  * debugging.
  23  */
  24
  25 #include <sys/mman.h>
  26 #include <sys/stat.h>
  27 #include <sys/types.h>
  28
  29 #include <byteswap.h>
  30 #include <elf.h>
  31 #include <errno.h>
  32 #include <fcntl.h>
  33 #include <inttypes.h>
  34 #include <stdarg.h>
  35 #include <stdbool.h>
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40
  41 /* Define these in case the system elf.h is not new enough to have them. */
  42 #ifndef SHT_GNU_ATTRIBUTES
  43 # define SHT_GNU_ATTRIBUTES     0x6ffffff5
  44 #endif
  45 #ifndef SHT_MIPS_ABIFLAGS
  46 # define SHT_MIPS_ABIFLAGS      0x7000002a
  47 #endif
  48
  49 enum {
  50         ABI_O32 = (1 << 0),
  51         ABI_N32 = (1 << 1),
  52         ABI_N64 = (1 << 2),
  53
  54         ABI_ALL = ABI_O32 | ABI_N32 | ABI_N64,
  55 };
  56
  57 /* Symbols the kernel requires offsets for. */
  58 static struct {
  59         const char *name;
  60         const char *offset_name;
  61         unsigned int abis;
  62 } vdso_symbols[] = {
  63         { "__vdso_sigreturn", "off_sigreturn", ABI_O32 },
  64         { "__vdso_rt_sigreturn", "off_rt_sigreturn", ABI_ALL },
  65         {}
  66 };
  67
  68 static const char *program_name;
  69 static const char *vdso_name;
  70 static unsigned char elf_class;
  71 static unsigned int elf_abi;
  72 static bool need_swap;
  73 static FILE *out_file;
  74
  75 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
  76 # define HOST_ORDER             ELFDATA2LSB
  77 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
  78 # define HOST_ORDER             ELFDATA2MSB
  79 #endif
  80
  81 #define BUILD_SWAP(bits)                                                \
  82         static uint##bits##_t swap_uint##bits(uint##bits##_t val)       \
  83         {                                                               \
  84                 return need_swap ? bswap_##bits(val) : val;             \
  85         }
  86
  87 BUILD_SWAP(16)
  88 BUILD_SWAP(32)
  89 BUILD_SWAP(64)
  90
  91 #define __FUNC(name, bits) name##bits
  92 #define _FUNC(name, bits) __FUNC(name, bits)
  93 #define FUNC(name) _FUNC(name, ELF_BITS)
  94
  95 #define __ELF(x, bits) Elf##bits##_##x
  96 #define _ELF(x, bits) __ELF(x, bits)
  97 #define ELF(x) _ELF(x, ELF_BITS)
  98
  99 /*
 100  * Include genvdso.h twice with ELF_BITS defined differently to get functions
 101  * for both ELF32 and ELF64.
 102  */
 103
 104 #define ELF_BITS 64
 105 #include "genvdso.h"
 106 #undef ELF_BITS
 107
 108 #define ELF_BITS 32
 109 #include "genvdso.h"
 110 #undef ELF_BITS
 111
 112 static void *map_vdso(const char *path, size_t *_size)
 113 {
 114         int fd;
 115         struct stat stat;
 116         void *addr;
 117         const Elf32_Ehdr *ehdr;
 118
 119         fd = open(path, O_RDWR);
 120         if (fd < 0) {
 121                 fprintf(stderr, "%s: Failed to open '%s': %s\n", program_name,
 122                         path, strerror(errno));
 123                 return NULL;
 124         }
 125
 126         if (fstat(fd, &stat) != 0) {
 127                 fprintf(stderr, "%s: Failed to stat '%s': %s\n", program_name,
 128                         path, strerror(errno));
 129                 return NULL;
 130         }
 131
 132         addr = mmap(NULL, stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd,
 133                     0);
 134         if (addr == MAP_FAILED) {
 135                 fprintf(stderr, "%s: Failed to map '%s': %s\n", program_name,
 136                         path, strerror(errno));
 137                 return NULL;
 138         }
 139
 140         /* ELF32/64 header formats are the same for the bits we're checking. */
 141         ehdr = addr;
 142
 143         if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0) {
 144                 fprintf(stderr, "%s: '%s' is not an ELF file\n", program_name,
 145                         path);
 146                 return NULL;
 147         }
 148
 149         elf_class = ehdr->e_ident[EI_CLASS];
 150         switch (elf_class) {
 151         case ELFCLASS32:
 152         case ELFCLASS64:
 153                 break;
 154         default:
 155                 fprintf(stderr, "%s: '%s' has invalid ELF class\n",
 156                         program_name, path);
 157                 return NULL;
 158         }
 159
 160         switch (ehdr->e_ident[EI_DATA]) {
 161         case ELFDATA2LSB:
 162         case ELFDATA2MSB:
 163                 need_swap = ehdr->e_ident[EI_DATA] != HOST_ORDER;
 164                 break;
 165         default:
 166                 fprintf(stderr, "%s: '%s' has invalid ELF data order\n",
 167                         program_name, path);
 168                 return NULL;
 169         }
 170
 171         if (swap_uint16(ehdr->e_machine) != EM_MIPS) {
 172                 fprintf(stderr,
 173                         "%s: '%s' has invalid ELF machine (expected EM_MIPS)\n",
 174                         program_name, path);
 175                 return NULL;
 176         } else if (swap_uint16(ehdr->e_type) != ET_DYN) {
 177                 fprintf(stderr,
 178                         "%s: '%s' has invalid ELF type (expected ET_DYN)\n",
 179                         program_name, path);
 180                 return NULL;
 181         }
 182
 183         *_size = stat.st_size;
 184         return addr;
 185 }
 186
 187 static bool patch_vdso(const char *path, void *vdso)
 188 {
 189         if (elf_class == ELFCLASS64)
 190                 return patch_vdso64(path, vdso);
 191         else
 192                 return patch_vdso32(path, vdso);
 193 }
 194
 195 static bool get_symbols(const char *path, void *vdso)
 196 {
 197         if (elf_class == ELFCLASS64)
 198                 return get_symbols64(path, vdso);
 199         else
 200                 return get_symbols32(path, vdso);
 201 }
 202
 203 int main(int argc, char **argv)
 204 {
 205         const char *dbg_vdso_path, *vdso_path, *out_path;
 206         void *dbg_vdso, *vdso;
 207         size_t dbg_vdso_size, vdso_size, i;
 208
 209         program_name = argv[0];
 210
 211         if (argc < 4 || argc > 5) {
 212                 fprintf(stderr,
 213                         "Usage: %s <debug VDSO> <stripped VDSO> <output file> [<name>]\n",
 214                         program_name);
 215                 return EXIT_FAILURE;
 216         }
 217
 218         dbg_vdso_path = argv[1];
 219         vdso_path = argv[2];
 220         out_path = argv[3];
 221         vdso_name = (argc > 4) ? argv[4] : "";
 222
 223         dbg_vdso = map_vdso(dbg_vdso_path, &dbg_vdso_size);
 224         if (!dbg_vdso)
 225                 return EXIT_FAILURE;
 226
 227         vdso = map_vdso(vdso_path, &vdso_size);
 228         if (!vdso)
 229                 return EXIT_FAILURE;
 230
 231         /* Patch both the VDSOs' ABI flags sections. */
 232         if (!patch_vdso(dbg_vdso_path, dbg_vdso))
 233                 return EXIT_FAILURE;
 234         if (!patch_vdso(vdso_path, vdso))
 235                 return EXIT_FAILURE;
 236
 237         if (msync(dbg_vdso, dbg_vdso_size, MS_SYNC) != 0) {
 238                 fprintf(stderr, "%s: Failed to sync '%s': %s\n", program_name,
 239                         dbg_vdso_path, strerror(errno));
 240                 return EXIT_FAILURE;
 241         } else if (msync(vdso, vdso_size, MS_SYNC) != 0) {
 242                 fprintf(stderr, "%s: Failed to sync '%s': %s\n", program_name,
 243                         vdso_path, strerror(errno));
 244                 return EXIT_FAILURE;
 245         }
 246
 247         out_file = fopen(out_path, "w");
 248         if (!out_file) {
 249                 fprintf(stderr, "%s: Failed to open '%s': %s\n", program_name,
 250                         out_path, strerror(errno));
 251                 return EXIT_FAILURE;
 252         }
 253
 254         fprintf(out_file, "/* Automatically generated - do not edit */\n");
 255         fprintf(out_file, "#include <linux/linkage.h>\n");
 256         fprintf(out_file, "#include <linux/mm.h>\n");
 257         fprintf(out_file, "#include <asm/vdso.h>\n");
 258
 259         /* Write out the stripped VDSO data. */
 260         fprintf(out_file,
 261                 "static unsigned char vdso_data[PAGE_ALIGN(%zu)] __page_aligned_data = {\n\t",
 262                 vdso_size);
 263         for (i = 0; i < vdso_size; i++) {
 264                 if (!(i % 10))
 265                         fprintf(out_file, "\n\t");
 266                 fprintf(out_file, "0x%02x, ", ((unsigned char *)vdso)[i]);
 267         }
 268         fprintf(out_file, "\n};\n");
 269
 270         /* Preallocate a page array. */
 271         fprintf(out_file,
 272                 "static struct page *vdso_pages[PAGE_ALIGN(%zu) / PAGE_SIZE];\n",
 273                 vdso_size);
 274
 275         fprintf(out_file, "struct mips_vdso_image vdso_image%s%s = {\n",
 276                 (vdso_name[0]) ? "_" : "", vdso_name);
 277         fprintf(out_file, "\t.data = vdso_data,\n");
 278         fprintf(out_file, "\t.size = PAGE_ALIGN(%zu),\n", vdso_size);
 279         fprintf(out_file, "\t.mapping = {\n");
 280         fprintf(out_file, "\t\t.name = \"[vdso]\",\n");
 281         fprintf(out_file, "\t\t.pages = vdso_pages,\n");
 282         fprintf(out_file, "\t},\n");
 283
 284         /* Calculate and write symbol offsets to <output file> */
 285         if (!get_symbols(dbg_vdso_path, dbg_vdso)) {
 286                 unlink(out_path);
 287                 return EXIT_FAILURE;
 288         }
 289
 290         fprintf(out_file, "};\n");
 291
 292         return EXIT_SUCCESS;
 293 }