sysdeps/hppa/dl-fptr.c

   1 /* Manage function descriptors.  Generic version.
   2    Copyright (C) 1999-2012 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 <atomic.h>
  30
  31 #ifndef ELF_MACHINE_BOOT_FPTR_TABLE_LEN
  32 /* ELF_MACHINE_BOOT_FPTR_TABLE_LEN should be greater than the number of
  33    dynamic symbols in ld.so.  */
  34 # define ELF_MACHINE_BOOT_FPTR_TABLE_LEN 256
  35 #endif
  36
  37 #ifndef ELF_MACHINE_LOAD_ADDRESS
  38 # error "ELF_MACHINE_LOAD_ADDRESS is not defined."
  39 #endif
  40
  41 #ifndef COMPARE_AND_SWAP
  42 # define COMPARE_AND_SWAP(ptr, old, new) \
  43   (catomic_compare_and_exchange_bool_acq (ptr, new, old) == 0)
  44 #endif
  45
  46 ElfW(Addr) _dl_boot_fptr_table [ELF_MACHINE_BOOT_FPTR_TABLE_LEN];
  47
  48 static struct local
  49   {
  50     struct fdesc_table *root;
  51     struct fdesc *free_list;
  52     unsigned int npages;                /* # of pages to allocate */
  53     /* the next to members MUST be consecutive! */
  54     struct fdesc_table boot_table;
  55     struct fdesc boot_fdescs[1024];
  56   }
  57 local =
  58   {
  59 #ifdef SHARED
  60     /* Address of .boot_table is not known until runtime.  */
  61     .root = 0,
  62 #else
  63     .root = &local.boot_table,
  64 #endif
  65     .npages = 2,
  66     .boot_table =
  67       {
  68         .len = sizeof (local.boot_fdescs) / sizeof (local.boot_fdescs[0]),
  69         .first_unused = 0
  70       }
  71   };
  72
  73 /* Create a new fdesc table and return a pointer to the first fdesc
  74    entry.  The fdesc lock must have been acquired already.  */
  75
  76 static struct fdesc_table *
  77 new_fdesc_table (struct local *l, size_t *size)
  78 {
  79   size_t old_npages = l->npages;
  80   size_t new_npages = old_npages + old_npages;
  81   struct fdesc_table *new_table;
  82
  83   /* If someone has just created a new table, we return NULL to tell
  84      the caller to use the new table.  */
  85   if (! COMPARE_AND_SWAP (&l->npages, old_npages, new_npages))
  86     return (struct fdesc_table *) NULL;
  87
  88   *size = old_npages * GLRO(dl_pagesize);
  89   new_table = __mmap (NULL, *size,
  90                       PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
  91   if (new_table == MAP_FAILED)
  92     _dl_signal_error (errno, NULL, NULL,
  93                       N_("cannot map pages for fdesc table"));
  94
  95   new_table->len
  96     = (*size - sizeof (*new_table)) / sizeof (struct fdesc);
  97   new_table->first_unused = 1;
  98   return new_table;
  99 }
 100
 101 /* Must call _dl_fptr_init before using any other function.  */
 102 void
 103 _dl_fptr_init (void)
 104 {
 105   struct local *l;
 106
 107   ELF_MACHINE_LOAD_ADDRESS (l, local);
 108   l->root = &l->boot_table;
 109 }
 110
 111 static ElfW(Addr)
 112 make_fdesc (ElfW(Addr) ip, ElfW(Addr) gp)
 113 {
 114   struct fdesc *fdesc = NULL;
 115   struct fdesc_table *root;
 116   unsigned int old;
 117   struct local *l;
 118
 119   ELF_MACHINE_LOAD_ADDRESS (l, local);
 120
 121  retry:
 122   root = l->root;
 123   while (1)
 124     {
 125       old = root->first_unused;
 126       if (old >= root->len)
 127         break;
 128       else if (COMPARE_AND_SWAP (&root->first_unused, old, old + 1))
 129         {
 130           fdesc = &root->fdesc[old];
 131           goto install;
 132         }
 133     }
 134
 135   if (l->free_list)
 136     {
 137       /* Get it from free-list.  */
 138       do
 139         {
 140           fdesc = l->free_list;
 141           if (fdesc == NULL)
 142             goto retry;
 143         }
 144       while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list,
 145                                  (ElfW(Addr)) fdesc, fdesc->ip));
 146     }
 147   else
 148     {
 149       /* Create a new fdesc table.  */
 150       size_t size;
 151       struct fdesc_table *new_table = new_fdesc_table (l, &size);
 152
 153       if (new_table == NULL)
 154         goto retry;
 155
 156       new_table->next = root;
 157       if (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->root,
 158                               (ElfW(Addr)) root,
 159                               (ElfW(Addr)) new_table))
 160         {
 161           /* Someone has just installed a new table. Return NULL to
 162              tell the caller to use the new table.  */
 163           __munmap (new_table, size);
 164           goto retry;
 165         }
 166
 167       /* Note that the first entry was reserved while allocating the
 168          memory for the new page.  */
 169       fdesc = &new_table->fdesc[0];
 170     }
 171
 172  install:
 173   fdesc->ip = ip;
 174   fdesc->gp = gp;
 175
 176   return (ElfW(Addr)) fdesc;
 177 }
 178
 179
 180 static inline ElfW(Addr) * __attribute__ ((always_inline))
 181 make_fptr_table (struct link_map *map)
 182 {
 183   const ElfW(Sym) *symtab
 184     = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
 185   const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
 186   ElfW(Addr) *fptr_table;
 187   size_t size;
 188   size_t len;
 189
 190   /* XXX Apparently the only way to find out the size of the dynamic
 191      symbol section is to assume that the string table follows right
 192      afterwards...  */
 193   len = ((strtab - (char *) symtab)
 194          / map->l_info[DT_SYMENT]->d_un.d_val);
 195   size = ((len * sizeof (fptr_table[0]) + GLRO(dl_pagesize) - 1)
 196           & -GLRO(dl_pagesize));
 197   /* XXX We don't support here in the moment systems without MAP_ANON.
 198      There probably are none for IA-64.  In case this is proven wrong
 199      we will have to open /dev/null here and use the file descriptor
 200      instead of the hard-coded -1.  */
 201   fptr_table = __mmap (NULL, size,
 202                        PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE,
 203                        -1, 0);
 204   if (fptr_table == MAP_FAILED)
 205     _dl_signal_error (errno, NULL, NULL,
 206                       N_("cannot map pages for fptr table"));
 207
 208   if (COMPARE_AND_SWAP ((ElfW(Addr) *) &map->l_mach.fptr_table,
 209                         (ElfW(Addr)) NULL, (ElfW(Addr)) fptr_table))
 210     map->l_mach.fptr_table_len = len;
 211   else
 212     __munmap (fptr_table, len * sizeof (fptr_table[0]));
 213
 214   return map->l_mach.fptr_table;
 215 }
 216
 217
 218 ElfW(Addr)
 219 _dl_make_fptr (struct link_map *map, const ElfW(Sym) *sym,
 220                ElfW(Addr) ip)
 221 {
 222   ElfW(Addr) *ftab = map->l_mach.fptr_table;
 223   const ElfW(Sym) *symtab;
 224   Elf_Symndx symidx;
 225   struct local *l;
 226
 227   if (__builtin_expect (ftab == NULL, 0))
 228     ftab = make_fptr_table (map);
 229
 230   symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
 231   symidx = sym - symtab;
 232
 233   if (symidx >= map->l_mach.fptr_table_len)
 234     _dl_signal_error (0, NULL, NULL,
 235                       N_("internal error: symidx out of range of fptr table"));
 236
 237   while (ftab[symidx] == 0)
 238     {
 239       /* GOT has already been relocated in elf_get_dynamic_info -
 240          don't try to relocate it again.  */
 241       ElfW(Addr) fdesc
 242         = make_fdesc (ip, map->l_info[DT_PLTGOT]->d_un.d_ptr);
 243
 244       if (__builtin_expect (COMPARE_AND_SWAP (&ftab[symidx], (ElfW(Addr)) NULL,
 245                                               fdesc), 1))
 246         {
 247           /* Noone has updated the entry and the new function
 248              descriptor has been installed.  */
 249 #if 0
 250           const char *strtab
 251             = (const void *) D_PTR (map, l_info[DT_STRTAB]);
 252
 253           ELF_MACHINE_LOAD_ADDRESS (l, local);
 254           if (l->root != &l->boot_table
 255               || l->boot_table.first_unused > 20)
 256             _dl_debug_printf ("created fdesc symbol `%s' at %lx\n",
 257                               strtab + sym->st_name, ftab[symidx]);
 258 #endif
 259           break;
 260         }
 261       else
 262         {
 263           /* We created a duplicated function descriptor. We put it on
 264              free-list.  */
 265           struct fdesc *f = (struct fdesc *) fdesc;
 266
 267           ELF_MACHINE_LOAD_ADDRESS (l, local);
 268
 269           do
 270             f->ip = (ElfW(Addr)) l->free_list;
 271           while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list,
 272                                      f->ip, fdesc));
 273         }
 274     }
 275
 276   return ftab[symidx];
 277 }
 278
 279
 280 void
 281 _dl_unmap (struct link_map *map)
 282 {
 283   ElfW(Addr) *ftab = map->l_mach.fptr_table;
 284   struct fdesc *head = NULL, *tail = NULL;
 285   size_t i;
 286
 287   __munmap ((void *) map->l_map_start,
 288             map->l_map_end - map->l_map_start);
 289
 290   if (ftab == NULL)
 291     return;
 292
 293   /* String together the fdesc structures that are being freed.  */
 294   for (i = 0; i < map->l_mach.fptr_table_len; ++i)
 295     {
 296       if (ftab[i])
 297         {
 298           *(struct fdesc **) ftab[i] = head;
 299           head = (struct fdesc *) ftab[i];
 300           if (tail == NULL)
 301             tail = head;
 302         }
 303     }
 304
 305   /* Prepend the new list to the free_list: */
 306   if (tail)
 307     do
 308       tail->ip = (ElfW(Addr)) local.free_list;
 309     while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &local.free_list,
 310                                tail->ip, (ElfW(Addr)) head));
 311
 312   __munmap (ftab, (map->l_mach.fptr_table_len
 313                    * sizeof (map->l_mach.fptr_table[0])));
 314
 315   map->l_mach.fptr_table = NULL;
 316 }
 317
 318
 319 ElfW(Addr)
 320 _dl_lookup_address (const void *address)
 321 {
 322   ElfW(Addr) addr = (ElfW(Addr)) address;
 323   struct fdesc_table *t;
 324   unsigned long int i;
 325
 326   for (t = local.root; t != NULL; t = t->next)
 327     {
 328       i = (struct fdesc *) addr - &t->fdesc[0];
 329       if (i < t->first_unused && addr == (ElfW(Addr)) &t->fdesc[i])
 330         {
 331           addr = t->fdesc[i].ip;
 332           break;
 333         }
 334     }
 335
 336   return addr;
 337 }