arch/x86/entry/vdso/vdso2c.h

   1 /*
   2  * This file is included twice from vdso2c.c.  It generates code for 32-bit
   3  * and 64-bit vDSOs.  We need both for 64-bit builds, since 32-bit vDSOs
   4  * are built for 32-bit userspace.
   5  */
   6
   7 static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
   8                          void *stripped_addr, size_t stripped_len,
   9                          FILE *outfile, const char *name)
  10 {
  11         int found_load = 0;
  12         unsigned long load_size = -1;  /* Work around bogus warning */
  13         unsigned long mapping_size;
  14         ELF(Ehdr) *hdr = (ELF(Ehdr) *)raw_addr;
  15         int i;
  16         unsigned long j;
  17         ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr,
  18                 *alt_sec = NULL;
  19         ELF(Dyn) *dyn = 0, *dyn_end = 0;
  20         const char *secstrings;
  21         INT_BITS syms[NSYMS] = {};
  22
  23         ELF(Phdr) *pt = (ELF(Phdr) *)(raw_addr + GET_LE(&hdr->e_phoff));
  24
  25         if (hdr->e_type != ET_DYN)
  26                 fail("input is not a shared object\n");
  27
  28         /* Walk the segment table. */
  29         for (i = 0; i < GET_LE(&hdr->e_phnum); i++) {
  30                 if (GET_LE(&pt[i].p_type) == PT_LOAD) {
  31                         if (found_load)
  32                                 fail("multiple PT_LOAD segs\n");
  33
  34                         if (GET_LE(&pt[i].p_offset) != 0 ||
  35                             GET_LE(&pt[i].p_vaddr) != 0)
  36                                 fail("PT_LOAD in wrong place\n");
  37
  38                         if (GET_LE(&pt[i].p_memsz) != GET_LE(&pt[i].p_filesz))
  39                                 fail("cannot handle memsz != filesz\n");
  40
  41                         load_size = GET_LE(&pt[i].p_memsz);
  42                         found_load = 1;
  43                 } else if (GET_LE(&pt[i].p_type) == PT_DYNAMIC) {
  44                         dyn = raw_addr + GET_LE(&pt[i].p_offset);
  45                         dyn_end = raw_addr + GET_LE(&pt[i].p_offset) +
  46                                 GET_LE(&pt[i].p_memsz);
  47                 }
  48         }
  49         if (!found_load)
  50                 fail("no PT_LOAD seg\n");
  51
  52         if (stripped_len < load_size)
  53                 fail("stripped input is too short\n");
  54
  55         if (!dyn)
  56                 fail("input has no PT_DYNAMIC section -- your toolchain is buggy\n");
  57
  58         /* Walk the dynamic table */
  59         for (i = 0; dyn + i < dyn_end &&
  60                      GET_LE(&dyn[i].d_tag) != DT_NULL; i++) {
  61                 typeof(dyn[i].d_tag) tag = GET_LE(&dyn[i].d_tag);
  62                 if (tag == DT_REL || tag == DT_RELSZ || tag == DT_RELA ||
  63                     tag == DT_RELENT || tag == DT_TEXTREL)
  64                         fail("vdso image contains dynamic relocations\n");
  65         }
  66
  67         /* Walk the section table */
  68         secstrings_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
  69                 GET_LE(&hdr->e_shentsize)*GET_LE(&hdr->e_shstrndx);
  70         secstrings = raw_addr + GET_LE(&secstrings_hdr->sh_offset);
  71         for (i = 0; i < GET_LE(&hdr->e_shnum); i++) {
  72                 ELF(Shdr) *sh = raw_addr + GET_LE(&hdr->e_shoff) +
  73                         GET_LE(&hdr->e_shentsize) * i;
  74                 if (GET_LE(&sh->sh_type) == SHT_SYMTAB)
  75                         symtab_hdr = sh;
  76
  77                 if (!strcmp(secstrings + GET_LE(&sh->sh_name),
  78                             ".altinstructions"))
  79                         alt_sec = sh;
  80         }
  81
  82         if (!symtab_hdr)
  83                 fail("no symbol table\n");
  84
  85         strtab_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
  86                 GET_LE(&hdr->e_shentsize) * GET_LE(&symtab_hdr->sh_link);
  87
  88         /* Walk the symbol table */
  89         for (i = 0;
  90              i < GET_LE(&symtab_hdr->sh_size) / GET_LE(&symtab_hdr->sh_entsize);
  91              i++) {
  92                 int k;
  93                 ELF(Sym) *sym = raw_addr + GET_LE(&symtab_hdr->sh_offset) +
  94                         GET_LE(&symtab_hdr->sh_entsize) * i;
  95                 const char *name = raw_addr + GET_LE(&strtab_hdr->sh_offset) +
  96                         GET_LE(&sym->st_name);
  97
  98                 for (k = 0; k < NSYMS; k++) {
  99                         if (!strcmp(name, required_syms[k].name)) {
 100                                 if (syms[k]) {
 101                                         fail("duplicate symbol %s\n",
 102                                              required_syms[k].name);
 103                                 }
 104
 105                                 /*
 106                                  * Careful: we use negative addresses, but
 107                                  * st_value is unsigned, so we rely
 108                                  * on syms[k] being a signed type of the
 109                                  * correct width.
 110                                  */
 111                                 syms[k] = GET_LE(&sym->st_value);
 112                         }
 113                 }
 114         }
 115
 116         /* Validate mapping addresses. */
 117         for (i = 0; i < sizeof(special_pages) / sizeof(special_pages[0]); i++) {
 118                 INT_BITS symval = syms[special_pages[i]];
 119
 120                 if (!symval)
 121                         continue;  /* The mapping isn't used; ignore it. */
 122
 123                 if (symval % 4096)
 124                         fail("%s must be a multiple of 4096\n",
 125                              required_syms[i].name);
 126                 if (symval + 4096 < syms[sym_vvar_start])
 127                         fail("%s underruns vvar_start\n",
 128                              required_syms[i].name);
 129                 if (symval + 4096 > 0)
 130                         fail("%s is on the wrong side of the vdso text\n",
 131                              required_syms[i].name);
 132         }
 133         if (syms[sym_vvar_start] % 4096)
 134                 fail("vvar_begin must be a multiple of 4096\n");
 135
 136         if (!name) {
 137                 fwrite(stripped_addr, stripped_len, 1, outfile);
 138                 return;
 139         }
 140
 141         mapping_size = (stripped_len + 4095) / 4096 * 4096;
 142
 143         fprintf(outfile, "/* AUTOMATICALLY GENERATED -- DO NOT EDIT */\n\n");
 144         fprintf(outfile, "#include <linux/linkage.h>\n");
 145         fprintf(outfile, "#include <asm/page_types.h>\n");
 146         fprintf(outfile, "#include <asm/vdso.h>\n");
 147         fprintf(outfile, "\n");
 148         fprintf(outfile,
 149                 "static unsigned char raw_data[%lu] __ro_after_init __aligned(PAGE_SIZE) = {",
 150                 mapping_size);
 151         for (j = 0; j < stripped_len; j++) {
 152                 if (j % 10 == 0)
 153                         fprintf(outfile, "\n\t");
 154                 fprintf(outfile, "0x%02X, ",
 155                         (int)((unsigned char *)stripped_addr)[j]);
 156         }
 157         fprintf(outfile, "\n};\n\n");
 158
 159         fprintf(outfile, "const struct vdso_image %s = {\n", name);
 160         fprintf(outfile, "\t.data = raw_data,\n");
 161         fprintf(outfile, "\t.size = %lu,\n", mapping_size);
 162         if (alt_sec) {
 163                 fprintf(outfile, "\t.alt = %lu,\n",
 164                         (unsigned long)GET_LE(&alt_sec->sh_offset));
 165                 fprintf(outfile, "\t.alt_len = %lu,\n",
 166                         (unsigned long)GET_LE(&alt_sec->sh_size));
 167         }
 168         for (i = 0; i < NSYMS; i++) {
 169                 if (required_syms[i].export && syms[i])
 170                         fprintf(outfile, "\t.sym_%s = %" PRIi64 ",\n",
 171                                 required_syms[i].name, (int64_t)syms[i]);
 172         }
 173         fprintf(outfile, "};\n");
 174 }