arch/x86/entry/vdso/vdso2c.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * This file is included twice from vdso2c.c.  It generates code for 32-bit
   4  * and 64-bit vDSOs.  We need both for 64-bit builds, since 32-bit vDSOs
   5  * are built for 32-bit userspace.
   6  */
   7
   8 static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
   9                          void *stripped_addr, size_t stripped_len,
  10                          FILE *outfile, const char *name)
  11 {
  12         int found_load = 0;
  13         unsigned long load_size = -1;  /* Work around bogus warning */
  14         unsigned long mapping_size;
  15         ELF(Ehdr) *hdr = (ELF(Ehdr) *)raw_addr;
  16         int i;
  17         unsigned long j;
  18         ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr,
  19                 *alt_sec = NULL;
  20         ELF(Dyn) *dyn = 0, *dyn_end = 0;
  21         const char *secstrings;
  22         INT_BITS syms[NSYMS] = {};
  23
  24         ELF(Phdr) *pt = (ELF(Phdr) *)(raw_addr + GET_LE(&hdr->e_phoff));
  25
  26         if (GET_LE(&hdr->e_type) != ET_DYN)
  27                 fail("input is not a shared object\n");
  28
  29         /* Walk the segment table. */
  30         for (i = 0; i < GET_LE(&hdr->e_phnum); i++) {
  31                 if (GET_LE(&pt[i].p_type) == PT_LOAD) {
  32                         if (found_load)
  33                                 fail("multiple PT_LOAD segs\n");
  34
  35                         if (GET_LE(&pt[i].p_offset) != 0 ||
  36                             GET_LE(&pt[i].p_vaddr) != 0)
  37                                 fail("PT_LOAD in wrong place\n");
  38
  39                         if (GET_LE(&pt[i].p_memsz) != GET_LE(&pt[i].p_filesz))
  40                                 fail("cannot handle memsz != filesz\n");
  41
  42                         load_size = GET_LE(&pt[i].p_memsz);
  43                         found_load = 1;
  44                 } else if (GET_LE(&pt[i].p_type) == PT_DYNAMIC) {
  45                         dyn = raw_addr + GET_LE(&pt[i].p_offset);
  46                         dyn_end = raw_addr + GET_LE(&pt[i].p_offset) +
  47                                 GET_LE(&pt[i].p_memsz);
  48                 }
  49         }
  50         if (!found_load)
  51                 fail("no PT_LOAD seg\n");
  52
  53         if (stripped_len < load_size)
  54                 fail("stripped input is too short\n");
  55
  56         if (!dyn)
  57                 fail("input has no PT_DYNAMIC section -- your toolchain is buggy\n");
  58
  59         /* Walk the dynamic table */
  60         for (i = 0; dyn + i < dyn_end &&
  61                      GET_LE(&dyn[i].d_tag) != DT_NULL; i++) {
  62                 typeof(dyn[i].d_tag) tag = GET_LE(&dyn[i].d_tag);
  63                 if (tag == DT_REL || tag == DT_RELSZ || tag == DT_RELA ||
  64                     tag == DT_RELENT || tag == DT_TEXTREL)
  65                         fail("vdso image contains dynamic relocations\n");
  66         }
  67
  68         /* Walk the section table */
  69         secstrings_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
  70                 GET_LE(&hdr->e_shentsize)*GET_LE(&hdr->e_shstrndx);
  71         secstrings = raw_addr + GET_LE(&secstrings_hdr->sh_offset);
  72         for (i = 0; i < GET_LE(&hdr->e_shnum); i++) {
  73                 ELF(Shdr) *sh = raw_addr + GET_LE(&hdr->e_shoff) +
  74                         GET_LE(&hdr->e_shentsize) * i;
  75                 if (GET_LE(&sh->sh_type) == SHT_SYMTAB)
  76                         symtab_hdr = sh;
  77
  78                 if (!strcmp(secstrings + GET_LE(&sh->sh_name),
  79                             ".altinstructions"))
  80                         alt_sec = sh;
  81         }
  82
  83         if (!symtab_hdr)
  84                 fail("no symbol table\n");
  85
  86         strtab_hdr = raw_addr + GET_LE(&hdr->e_shoff) +
  87                 GET_LE(&hdr->e_shentsize) * GET_LE(&symtab_hdr->sh_link);
  88
  89         /* Walk the symbol table */
  90         for (i = 0;
  91              i < GET_LE(&symtab_hdr->sh_size) / GET_LE(&symtab_hdr->sh_entsize);
  92              i++) {
  93                 int k;
  94                 ELF(Sym) *sym = raw_addr + GET_LE(&symtab_hdr->sh_offset) +
  95                         GET_LE(&symtab_hdr->sh_entsize) * i;
  96                 const char *name = raw_addr + GET_LE(&strtab_hdr->sh_offset) +
  97                         GET_LE(&sym->st_name);
  98
  99                 for (k = 0; k < NSYMS; k++) {
 100                         if (!strcmp(name, required_syms[k].name)) {
 101                                 if (syms[k]) {
 102                                         fail("duplicate symbol %s\n",
 103                                              required_syms[k].name);
 104                                 }
 105
 106                                 /*
 107                                  * Careful: we use negative addresses, but
 108                                  * st_value is unsigned, so we rely
 109                                  * on syms[k] being a signed type of the
 110                                  * correct width.
 111                                  */
 112                                 syms[k] = GET_LE(&sym->st_value);
 113                         }
 114                 }
 115         }
 116
 117         /* Validate mapping addresses. */
 118         for (i = 0; i < sizeof(special_pages) / sizeof(special_pages[0]); i++) {
 119                 INT_BITS symval = syms[special_pages[i]];
 120
 121                 if (!symval)
 122                         continue;  /* The mapping isn't used; ignore it. */
 123
 124                 if (symval % 4096)
 125                         fail("%s must be a multiple of 4096\n",
 126                              required_syms[i].name);
 127                 if (symval + 4096 < syms[sym_vvar_start])
 128                         fail("%s underruns vvar_start\n",
 129                              required_syms[i].name);
 130                 if (symval + 4096 > 0)
 131                         fail("%s is on the wrong side of the vdso text\n",
 132                              required_syms[i].name);
 133         }
 134         if (syms[sym_vvar_start] % 4096)
 135                 fail("vvar_begin must be a multiple of 4096\n");
 136
 137         if (!name) {
 138                 fwrite(stripped_addr, stripped_len, 1, outfile);
 139                 return;
 140         }
 141
 142         mapping_size = (stripped_len + 4095) / 4096 * 4096;
 143
 144         fprintf(outfile, "/* AUTOMATICALLY GENERATED -- DO NOT EDIT */\n\n");
 145         fprintf(outfile, "#include <linux/linkage.h>\n");
 146         fprintf(outfile, "#include <asm/page_types.h>\n");
 147         fprintf(outfile, "#include <asm/vdso.h>\n");
 148         fprintf(outfile, "\n");
 149         fprintf(outfile,
 150                 "static unsigned char raw_data[%lu] __ro_after_init __aligned(PAGE_SIZE) = {",
 151                 mapping_size);
 152         for (j = 0; j < stripped_len; j++) {
 153                 if (j % 10 == 0)
 154                         fprintf(outfile, "\n\t");
 155                 fprintf(outfile, "0x%02X, ",
 156                         (int)((unsigned char *)stripped_addr)[j]);
 157         }
 158         fprintf(outfile, "\n};\n\n");
 159
 160         fprintf(outfile, "const struct vdso_image %s = {\n", name);
 161         fprintf(outfile, "\t.data = raw_data,\n");
 162         fprintf(outfile, "\t.size = %lu,\n", mapping_size);
 163         if (alt_sec) {
 164                 fprintf(outfile, "\t.alt = %lu,\n",
 165                         (unsigned long)GET_LE(&alt_sec->sh_offset));
 166                 fprintf(outfile, "\t.alt_len = %lu,\n",
 167                         (unsigned long)GET_LE(&alt_sec->sh_size));
 168         }
 169         for (i = 0; i < NSYMS; i++) {
 170                 if (required_syms[i].export && syms[i])
 171                         fprintf(outfile, "\t.sym_%s = %" PRIi64 ",\n",
 172                                 required_syms[i].name, (int64_t)syms[i]);
 173         }
 174         fprintf(outfile, "};\n");
 175 }