sysdeps/hppa/dl-fptr.c

   1 /* Manage function descriptors.  Generic version.
   2    Copyright (C) 1999-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <libintl.h>
  21 #include <unistd.h>
  22 #include <string.h>
  23 #include <sys/param.h>
  24 #include <sys/mman.h>
  25 #include <link.h>
  26 #include <ldsodefs.h>
  27 #include <elf/dynamic-link.h>
  28 #include <dl-fptr.h>
  29 #include <dl-unmap-segments.h>
  30 #include <atomic.h>
  31 #include <libc-pointer-arith.h>
  32
  33 #ifndef ELF_MACHINE_BOOT_FPTR_TABLE_LEN
  34 /* ELF_MACHINE_BOOT_FPTR_TABLE_LEN should be greater than the number of
  35    dynamic symbols in ld.so.  */
  36 # define ELF_MACHINE_BOOT_FPTR_TABLE_LEN 256
  37 #endif
  38
  39 #ifndef ELF_MACHINE_LOAD_ADDRESS
  40 # error "ELF_MACHINE_LOAD_ADDRESS is not defined."
  41 #endif
  42
  43 #ifndef COMPARE_AND_SWAP
  44 # define COMPARE_AND_SWAP(ptr, old, new) \
  45   (catomic_compare_and_exchange_bool_acq (ptr, new, old) == 0)
  46 #endif
  47
  48 ElfW(Addr) _dl_boot_fptr_table [ELF_MACHINE_BOOT_FPTR_TABLE_LEN];
  49
  50 static struct local
  51   {
  52     struct fdesc_table *root;
  53     struct fdesc *free_list;
  54     unsigned int npages;                /* # of pages to allocate */
  55     /* the next to members MUST be consecutive! */
  56     struct fdesc_table boot_table;
  57     struct fdesc boot_fdescs[1024];
  58   }
  59 local =
  60   {
  61 #ifdef SHARED
  62     /* Address of .boot_table is not known until runtime.  */
  63     .root = 0,
  64 #else
  65     .root = &local.boot_table,
  66 #endif
  67     .npages = 2,
  68     .boot_table =
  69       {
  70         .len = sizeof (local.boot_fdescs) / sizeof (local.boot_fdescs[0]),
  71         .first_unused = 0
  72       }
  73   };
  74
  75 /* Create a new fdesc table and return a pointer to the first fdesc
  76    entry.  The fdesc lock must have been acquired already.  */
  77
  78 static struct fdesc_table *
  79 new_fdesc_table (struct local *l, size_t *size)
  80 {
  81   size_t old_npages = l->npages;
  82   size_t new_npages = old_npages + old_npages;
  83   struct fdesc_table *new_table;
  84
  85   /* If someone has just created a new table, we return NULL to tell
  86      the caller to use the new table.  */
  87   if (! COMPARE_AND_SWAP (&l->npages, old_npages, new_npages))
  88     return (struct fdesc_table *) NULL;
  89
  90   *size = old_npages * GLRO(dl_pagesize);
  91   new_table = __mmap (NULL, *size,
  92                       PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
  93   if (new_table == MAP_FAILED)
  94     _dl_signal_error (errno, NULL, NULL,
  95                       N_("cannot map pages for fdesc table"));
  96
  97   new_table->len
  98     = (*size - sizeof (*new_table)) / sizeof (struct fdesc);
  99   new_table->first_unused = 1;
 100   return new_table;
 101 }
 102
 103 /* Must call _dl_fptr_init before using any other function.  */
 104 void
 105 _dl_fptr_init (void)
 106 {
 107   struct local *l;
 108
 109   ELF_MACHINE_LOAD_ADDRESS (l, local);
 110   l->root = &l->boot_table;
 111 }
 112
 113 static ElfW(Addr)
 114 make_fdesc (ElfW(Addr) ip, ElfW(Addr) gp)
 115 {
 116   struct fdesc *fdesc = NULL;
 117   struct fdesc_table *root;
 118   unsigned int old;
 119   struct local *l;
 120
 121   ELF_MACHINE_LOAD_ADDRESS (l, local);
 122
 123  retry:
 124   root = l->root;
 125   while (1)
 126     {
 127       old = root->first_unused;
 128       if (old >= root->len)
 129         break;
 130       else if (COMPARE_AND_SWAP (&root->first_unused, old, old + 1))
 131         {
 132           fdesc = &root->fdesc[old];
 133           goto install;
 134         }
 135     }
 136
 137   if (l->free_list)
 138     {
 139       /* Get it from free-list.  */
 140       do
 141         {
 142           fdesc = l->free_list;
 143           if (fdesc == NULL)
 144             goto retry;
 145         }
 146       while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list,
 147                                  (ElfW(Addr)) fdesc, fdesc->ip));
 148     }
 149   else
 150     {
 151       /* Create a new fdesc table.  */
 152       size_t size;
 153       struct fdesc_table *new_table = new_fdesc_table (l, &size);
 154
 155       if (new_table == NULL)
 156         goto retry;
 157
 158       new_table->next = root;
 159       if (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->root,
 160                               (ElfW(Addr)) root,
 161                               (ElfW(Addr)) new_table))
 162         {
 163           /* Someone has just installed a new table. Return NULL to
 164              tell the caller to use the new table.  */
 165           __munmap (new_table, size);
 166           goto retry;
 167         }
 168
 169       /* Note that the first entry was reserved while allocating the
 170          memory for the new page.  */
 171       fdesc = &new_table->fdesc[0];
 172     }
 173
 174  install:
 175   fdesc->gp = gp;
 176   fdesc->ip = ip;
 177
 178   return (ElfW(Addr)) fdesc;
 179 }
 180
 181
 182 static inline ElfW(Addr) * __attribute__ ((always_inline))
 183 make_fptr_table (struct link_map *map)
 184 {
 185   const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
 186   const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
 187   ElfW(Addr) *fptr_table;
 188   size_t size;
 189   size_t len;
 190   const ElfW(Sym) *symtabend;
 191
 192   /* Determine the end of the dynamic symbol table using the hash.  */
 193   if (map->l_info[DT_HASH] != NULL)
 194     symtabend = (symtab + ((Elf_Symndx *) D_PTR (map, l_info[DT_HASH]))[1]);
 195   else
 196   /* There is no direct way to determine the number of symbols in the
 197      dynamic symbol table and no hash table is present.  The ELF
 198      binary is ill-formed but what shall we do?  Use the beginning of
 199      the string table which generally follows the symbol table.  */
 200     symtabend = (const ElfW(Sym) *) strtab;
 201
 202   len = (((char *) symtabend - (char *) symtab)
 203          / map->l_info[DT_SYMENT]->d_un.d_val);
 204   size = ALIGN_UP (len * sizeof (fptr_table[0]), GLRO(dl_pagesize));
 205
 206   /* We don't support systems without MAP_ANON.  We avoid using malloc
 207      because this might get called before malloc is setup.  */
 208   fptr_table = __mmap (NULL, size,
 209                        PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE,
 210                        -1, 0);
 211   if (fptr_table == MAP_FAILED)
 212     _dl_signal_error (errno, NULL, NULL,
 213                       N_("cannot map pages for fptr table"));
 214
 215   if (COMPARE_AND_SWAP ((ElfW(Addr) *) &map->l_mach.fptr_table,
 216                         (ElfW(Addr)) NULL, (ElfW(Addr)) fptr_table))
 217     map->l_mach.fptr_table_len = len;
 218   else
 219     __munmap (fptr_table, len * sizeof (fptr_table[0]));
 220
 221   return map->l_mach.fptr_table;
 222 }
 223
 224
 225 ElfW(Addr)
 226 _dl_make_fptr (struct link_map *map, const ElfW(Sym) *sym,
 227                ElfW(Addr) ip)
 228 {
 229   ElfW(Addr) *ftab = map->l_mach.fptr_table;
 230   const ElfW(Sym) *symtab;
 231   Elf_Symndx symidx;
 232   struct local *l;
 233
 234   if (__builtin_expect (ftab == NULL, 0))
 235     ftab = make_fptr_table (map);
 236
 237   symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
 238   symidx = sym - symtab;
 239
 240   if (symidx >= map->l_mach.fptr_table_len)
 241     _dl_signal_error (0, NULL, NULL,
 242                       N_("internal error: symidx out of range of fptr table"));
 243
 244   while (ftab[symidx] == 0)
 245     {
 246       /* GOT has already been relocated in elf_get_dynamic_info -
 247          don't try to relocate it again.  */
 248       ElfW(Addr) fdesc
 249         = make_fdesc (ip, map->l_info[DT_PLTGOT]->d_un.d_ptr);
 250
 251       if (__builtin_expect (COMPARE_AND_SWAP (&ftab[symidx], (ElfW(Addr)) NULL,
 252                                               fdesc), 1))
 253         {
 254           /* Noone has updated the entry and the new function
 255              descriptor has been installed.  */
 256 #if 0
 257           const char *strtab
 258             = (const void *) D_PTR (map, l_info[DT_STRTAB]);
 259
 260           ELF_MACHINE_LOAD_ADDRESS (l, local);
 261           if (l->root != &l->boot_table
 262               || l->boot_table.first_unused > 20)
 263             _dl_debug_printf ("created fdesc symbol `%s' at %lx\n",
 264                               strtab + sym->st_name, ftab[symidx]);
 265 #endif
 266           break;
 267         }
 268       else
 269         {
 270           /* We created a duplicated function descriptor. We put it on
 271              free-list.  */
 272           struct fdesc *f = (struct fdesc *) fdesc;
 273
 274           ELF_MACHINE_LOAD_ADDRESS (l, local);
 275
 276           do
 277             f->ip = (ElfW(Addr)) l->free_list;
 278           while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list,
 279                                      f->ip, fdesc));
 280         }
 281     }
 282
 283   return ftab[symidx];
 284 }
 285
 286
 287 void
 288 _dl_unmap (struct link_map *map)
 289 {
 290   ElfW(Addr) *ftab = map->l_mach.fptr_table;
 291   struct fdesc *head = NULL, *tail = NULL;
 292   size_t i;
 293
 294   _dl_unmap_segments (map);
 295
 296   if (ftab == NULL)
 297     return;
 298
 299   /* String together the fdesc structures that are being freed.  */
 300   for (i = 0; i < map->l_mach.fptr_table_len; ++i)
 301     {
 302       if (ftab[i])
 303         {
 304           *(struct fdesc **) ftab[i] = head;
 305           head = (struct fdesc *) ftab[i];
 306           if (tail == NULL)
 307             tail = head;
 308         }
 309     }
 310
 311   /* Prepend the new list to the free_list: */
 312   if (tail)
 313     do
 314       tail->ip = (ElfW(Addr)) local.free_list;
 315     while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &local.free_list,
 316                                tail->ip, (ElfW(Addr)) head));
 317
 318   __munmap (ftab, (map->l_mach.fptr_table_len
 319                    * sizeof (map->l_mach.fptr_table[0])));
 320
 321   map->l_mach.fptr_table = NULL;
 322 }
 323
 324 extern ElfW(Addr) _dl_fixup (struct link_map *, ElfW(Word)) attribute_hidden;
 325
 326 static inline Elf32_Addr
 327 elf_machine_resolve (void)
 328 {
 329   Elf32_Addr addr;
 330
 331   asm ("b,l     1f,%0\n"
 332 "       addil   L'_dl_runtime_resolve - ($PIC_pcrel$0 - 1),%0\n"
 333 "1:     ldo     R'_dl_runtime_resolve - ($PIC_pcrel$0 - 5)(%%r1),%0\n"
 334        : "=r" (addr) : : "r1");
 335
 336   return addr;
 337 }
 338
 339 static inline int
 340 _dl_read_access_allowed (unsigned int *addr)
 341 {
 342   int result;
 343
 344   asm ("proberi (%1),3,%0" : "=r" (result) : "r" (addr) : );
 345
 346   return result;
 347 }
 348
 349 ElfW(Addr)
 350 _dl_lookup_address (const void *address)
 351 {
 352   ElfW(Addr) addr = (ElfW(Addr)) address;
 353   ElfW(Word) reloc_arg;
 354   volatile unsigned int *desc;
 355   unsigned int *gptr;
 356
 357   /* Return ADDR if the least-significant two bits of ADDR are not consistent
 358      with ADDR being a linker defined function pointer.  The normal value for
 359      a code address in a backtrace is 3.  */
 360   if (((unsigned int) addr & 3) != 2)
 361     return addr;
 362
 363   /* Handle special case where ADDR points to page 0.  */
 364   if ((unsigned int) addr < 4096)
 365     return addr;
 366
 367   /* Clear least-significant two bits from descriptor address.  */
 368   desc = (unsigned int *) ((unsigned int) addr & ~3);
 369   if (!_dl_read_access_allowed (desc))
 370     return addr;
 371
 372   /* First load the relocation offset.  */
 373   reloc_arg = (ElfW(Word)) desc[1];
 374   atomic_full_barrier();
 375
 376   /* Then load first word of candidate descriptor.  It should be a pointer
 377      with word alignment and point to memory that can be read.  */
 378   gptr = (unsigned int *) desc[0];
 379   if (((unsigned int) gptr & 3) != 0
 380       || !_dl_read_access_allowed (gptr))
 381     return addr;
 382
 383   /* See if descriptor requires resolution.  The following trampoline is
 384      used in each global offset table for function resolution:
 385
 386                 ldw 0(r20),r21
 387                 bv r0(r21)
 388                 ldw 4(r20),r21
 389      tramp:     b,l .-12,r20
 390                 depwi 0,31,2,r20
 391                 .word _dl_runtime_resolve
 392                 .word "_dl_runtime_resolve ltp"
 393      got:       .word _DYNAMIC
 394                 .word "struct link map address" */
 395   if (gptr[0] == 0xea9f1fdd                     /* b,l .-12,r20     */
 396       && gptr[1] == 0xd6801c1e                  /* depwi 0,31,2,r20 */
 397       && (ElfW(Addr)) gptr[2] == elf_machine_resolve ())
 398     {
 399       struct link_map *l = (struct link_map *) gptr[5];
 400
 401       /* If gp has been resolved, we need to hunt for relocation offset.  */
 402       if (!(reloc_arg & PA_GP_RELOC))
 403         reloc_arg = _dl_fix_reloc_arg (addr, l);
 404
 405       _dl_fixup (l, reloc_arg);
 406     }
 407
 408   return (ElfW(Addr)) desc[0];
 409 }