arch/mips/vdso/genvdso.h

   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 static inline bool FUNC(patch_vdso)(const char *path, void *vdso)
  12 {
  13         const ELF(Ehdr) *ehdr = vdso;
  14         void *shdrs;
  15         ELF(Shdr) *shdr;
  16         char *shstrtab, *name;
  17         uint16_t sh_count, sh_entsize, i;
  18         unsigned int local_gotno, symtabno, gotsym;
  19         ELF(Dyn) *dyn = NULL;
  20
  21         shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff);
  22         sh_count = swap_uint16(ehdr->e_shnum);
  23         sh_entsize = swap_uint16(ehdr->e_shentsize);
  24
  25         shdr = shdrs + (sh_entsize * swap_uint16(ehdr->e_shstrndx));
  26         shstrtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
  27
  28         for (i = 0; i < sh_count; i++) {
  29                 shdr = shdrs + (i * sh_entsize);
  30                 name = shstrtab + swap_uint32(shdr->sh_name);
  31
  32                 /*
  33                  * Ensure there are no relocation sections - ld.so does not
  34                  * relocate the VDSO so if there are relocations things will
  35                  * break.
  36                  */
  37                 switch (swap_uint32(shdr->sh_type)) {
  38                 case SHT_REL:
  39                 case SHT_RELA:
  40                         fprintf(stderr,
  41                                 "%s: '%s' contains relocation sections\n",
  42                                 program_name, path);
  43                         return false;
  44                 case SHT_DYNAMIC:
  45                         dyn = vdso + FUNC(swap_uint)(shdr->sh_offset);
  46                         break;
  47                 }
  48
  49                 /* Check for existing sections. */
  50                 if (strcmp(name, ".MIPS.abiflags") == 0) {
  51                         fprintf(stderr,
  52                                 "%s: '%s' already contains a '.MIPS.abiflags' section\n",
  53                                 program_name, path);
  54                         return false;
  55                 }
  56
  57                 if (strcmp(name, ".mips_abiflags") == 0) {
  58                         strcpy(name, ".MIPS.abiflags");
  59                         shdr->sh_type = swap_uint32(SHT_MIPS_ABIFLAGS);
  60                         shdr->sh_entsize = shdr->sh_size;
  61                 }
  62         }
  63
  64         /*
  65          * Ensure the GOT has no entries other than the standard 2, for the same
  66          * reason we check that there's no relocation sections above.
  67          * The standard two entries are:
  68          * - Lazy resolver
  69          * - Module pointer
  70          */
  71         if (dyn) {
  72                 local_gotno = symtabno = gotsym = 0;
  73
  74                 while (FUNC(swap_uint)(dyn->d_tag) != DT_NULL) {
  75                         switch (FUNC(swap_uint)(dyn->d_tag)) {
  76                         /*
  77                          * This member holds the number of local GOT entries.
  78                          */
  79                         case DT_MIPS_LOCAL_GOTNO:
  80                                 local_gotno = FUNC(swap_uint)(dyn->d_un.d_val);
  81                                 break;
  82                         /*
  83                          * This member holds the number of entries in the
  84                          * .dynsym section.
  85                          */
  86                         case DT_MIPS_SYMTABNO:
  87                                 symtabno = FUNC(swap_uint)(dyn->d_un.d_val);
  88                                 break;
  89                         /*
  90                          * This member holds the index of the first dynamic
  91                          * symbol table entry that corresponds to an entry in
  92                          * the GOT.
  93                          */
  94                         case DT_MIPS_GOTSYM:
  95                                 gotsym = FUNC(swap_uint)(dyn->d_un.d_val);
  96                                 break;
  97                         }
  98
  99                         dyn++;
 100                 }
 101
 102                 if (local_gotno > 2 || symtabno - gotsym) {
 103                         fprintf(stderr,
 104                                 "%s: '%s' contains unexpected GOT entries\n",
 105                                 program_name, path);
 106                         return false;
 107                 }
 108         }
 109
 110         return true;
 111 }
 112
 113 static inline bool FUNC(get_symbols)(const char *path, void *vdso)
 114 {
 115         const ELF(Ehdr) *ehdr = vdso;
 116         void *shdrs, *symtab;
 117         ELF(Shdr) *shdr;
 118         const ELF(Sym) *sym;
 119         char *strtab, *name;
 120         uint16_t sh_count, sh_entsize, st_count, st_entsize, i, j;
 121         uint64_t offset;
 122         uint32_t flags;
 123
 124         shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff);
 125         sh_count = swap_uint16(ehdr->e_shnum);
 126         sh_entsize = swap_uint16(ehdr->e_shentsize);
 127
 128         for (i = 0; i < sh_count; i++) {
 129                 shdr = shdrs + (i * sh_entsize);
 130
 131                 if (swap_uint32(shdr->sh_type) == SHT_SYMTAB)
 132                         break;
 133         }
 134
 135         if (i == sh_count) {
 136                 fprintf(stderr, "%s: '%s' has no symbol table\n", program_name,
 137                         path);
 138                 return false;
 139         }
 140
 141         /* Get flags */
 142         flags = swap_uint32(ehdr->e_flags);
 143         if (elf_class == ELFCLASS64)
 144                 elf_abi = ABI_N64;
 145         else if (flags & EF_MIPS_ABI2)
 146                 elf_abi = ABI_N32;
 147         else
 148                 elf_abi = ABI_O32;
 149
 150         /* Get symbol table. */
 151         symtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
 152         st_entsize = FUNC(swap_uint)(shdr->sh_entsize);
 153         st_count = FUNC(swap_uint)(shdr->sh_size) / st_entsize;
 154
 155         /* Get string table. */
 156         shdr = shdrs + (swap_uint32(shdr->sh_link) * sh_entsize);
 157         strtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
 158
 159         /* Write offsets for symbols needed by the kernel. */
 160         for (i = 0; vdso_symbols[i].name; i++) {
 161                 if (!(vdso_symbols[i].abis & elf_abi))
 162                         continue;
 163
 164                 for (j = 0; j < st_count; j++) {
 165                         sym = symtab + (j * st_entsize);
 166                         name = strtab + swap_uint32(sym->st_name);
 167
 168                         if (!strcmp(name, vdso_symbols[i].name)) {
 169                                 offset = FUNC(swap_uint)(sym->st_value);
 170
 171                                 fprintf(out_file,
 172                                         "\t.%s = 0x%" PRIx64 ",\n",
 173                                         vdso_symbols[i].offset_name, offset);
 174                                 break;
 175                         }
 176                 }
 177
 178                 if (j == st_count) {
 179                         fprintf(stderr,
 180                                 "%s: '%s' is missing required symbol '%s'\n",
 181                                 program_name, path, vdso_symbols[i].name);
 182                         return false;
 183                 }
 184         }
 185
 186         return true;
 187 }