Logo Search packages:      
Sourcecode: glibc version File versions

dl-fptr.c

/* Manage function descriptors.  Generic version.
   Copyright (C) 1999-2004, 2006 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <libintl.h>
#include <unistd.h>
#include <string.h>
#include <sys/param.h>
#include <sys/mman.h>
#include <link.h>
#include <ldsodefs.h>
#include <elf/dynamic-link.h>
#include <dl-fptr.h>
#include <atomic.h>

#ifndef ELF_MACHINE_BOOT_FPTR_TABLE_LEN
/* ELF_MACHINE_BOOT_FPTR_TABLE_LEN should be greater than the number of
   dynamic symbols in ld.so.  */
# define ELF_MACHINE_BOOT_FPTR_TABLE_LEN 256
#endif

#ifndef ELF_MACHINE_LOAD_ADDRESS
# error "ELF_MACHINE_LOAD_ADDRESS is not defined."
#endif

#ifndef COMPARE_AND_SWAP
# define COMPARE_AND_SWAP(ptr, old, new) \
  (catomic_compare_and_exchange_bool_acq (ptr, new, old) == 0)
#endif

ElfW(Addr) _dl_boot_fptr_table [ELF_MACHINE_BOOT_FPTR_TABLE_LEN];

static struct local
  {
    struct fdesc_table *root;
    struct fdesc *free_list;
    unsigned int npages;            /* # of pages to allocate */
    /* the next to members MUST be consecutive! */
    struct fdesc_table boot_table;
    struct fdesc boot_fdescs[1024];
  }
local =
  {
    .root = &local.boot_table,
    .npages = 2,
    .boot_table =
      {
      .len = sizeof (local.boot_fdescs) / sizeof (local.boot_fdescs[0]),
      .first_unused = 0
      }
  };

/* Create a new fdesc table and return a pointer to the first fdesc
   entry.  The fdesc lock must have been acquired already.  */

static struct fdesc_table *
new_fdesc_table (struct local *l, size_t *size)
{
  size_t old_npages = l->npages;
  size_t new_npages = old_npages + old_npages;
  struct fdesc_table *new_table;

  /* If someone has just created a new table, we return NULL to tell
     the caller to use the new table.  */
  if (! COMPARE_AND_SWAP (&l->npages, old_npages, new_npages))
    return (struct fdesc_table *) NULL;

  *size = old_npages * GLRO(dl_pagesize);
  new_table = __mmap (NULL, *size,
                  PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
  if (new_table == MAP_FAILED)
    _dl_signal_error (errno, NULL, NULL,
                  N_("cannot map pages for fdesc table"));

  new_table->len
    = (*size - sizeof (*new_table)) / sizeof (struct fdesc);
  new_table->first_unused = 1;
  return new_table;
}


static ElfW(Addr)
make_fdesc (ElfW(Addr) ip, ElfW(Addr) gp)
{
  struct fdesc *fdesc = NULL;
  struct fdesc_table *root;
  unsigned int old;
  struct local *l;

  ELF_MACHINE_LOAD_ADDRESS (l, local);

 retry:
  root = l->root;
  while (1)
    {
      old = root->first_unused;
      if (old >= root->len)
      break;
      else if (COMPARE_AND_SWAP (&root->first_unused, old, old + 1))
      {
        fdesc = &root->fdesc[old];
        goto install;
      }
    }

  if (l->free_list)
    {
      /* Get it from free-list.  */
      do
      {
        fdesc = l->free_list;
        if (fdesc == NULL)
          goto retry;
      }
      while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list,
                         (ElfW(Addr)) fdesc, fdesc->ip));
    }
  else
    {
      /* Create a new fdesc table.  */
      size_t size;
      struct fdesc_table *new_table = new_fdesc_table (l, &size);

      if (new_table == NULL)
      goto retry;

      new_table->next = root;
      if (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->root,
                        (ElfW(Addr)) root,
                        (ElfW(Addr)) new_table))
      {
        /* Someone has just installed a new table. Return NULL to
           tell the caller to use the new table.  */
        __munmap (new_table, size);
        goto retry;
      }

      /* Note that the first entry was reserved while allocating the
       memory for the new page.  */
      fdesc = &new_table->fdesc[0];
    }

 install:
  fdesc->ip = ip;
  fdesc->gp = gp;

  return (ElfW(Addr)) fdesc;
}


static inline ElfW(Addr) * __attribute__ ((always_inline))
make_fptr_table (struct link_map *map)
{
  const ElfW(Sym) *symtab
    = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
  const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
  ElfW(Addr) *fptr_table;
  size_t size;
  size_t len;

  /* XXX Apparently the only way to find out the size of the dynamic
     symbol section is to assume that the string table follows right
     afterwards...  */
  len = ((strtab - (char *) symtab)
       / map->l_info[DT_SYMENT]->d_un.d_val);
  size = ((len * sizeof (fptr_table[0]) + GLRO(dl_pagesize) - 1)
        & -GLRO(dl_pagesize));
  /* XXX We don't support here in the moment systems without MAP_ANON.
     There probably are none for IA-64.  In case this is proven wrong
     we will have to open /dev/null here and use the file descriptor
     instead of the hard-coded -1.  */
  fptr_table = __mmap (NULL, size,
                   PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE,
                   -1, 0);
  if (fptr_table == MAP_FAILED)
    _dl_signal_error (errno, NULL, NULL,
                  N_("cannot map pages for fptr table"));

  if (COMPARE_AND_SWAP ((ElfW(Addr) *) &map->l_mach.fptr_table,
                  (ElfW(Addr)) NULL, (ElfW(Addr)) fptr_table))
    map->l_mach.fptr_table_len = len;
  else
    __munmap (fptr_table, len * sizeof (fptr_table[0]));

  return map->l_mach.fptr_table;
}


ElfW(Addr)
_dl_make_fptr (struct link_map *map, const ElfW(Sym) *sym,
             ElfW(Addr) ip)
{
  ElfW(Addr) *ftab = map->l_mach.fptr_table;
  const ElfW(Sym) *symtab;
  Elf_Symndx symidx;
  struct local *l;

  if (__builtin_expect (ftab == NULL, 0))
    ftab = make_fptr_table (map);

  symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
  symidx = sym - symtab;

  if (symidx >= map->l_mach.fptr_table_len)
    _dl_signal_error (0, NULL, NULL,
                  N_("internal error: symidx out of range of fptr table"));

  while (ftab[symidx] == 0)
    {
      /* GOT has already been relocated in elf_get_dynamic_info -
       don't try to relocate it again.  */
      ElfW(Addr) fdesc
      = make_fdesc (ip, map->l_info[DT_PLTGOT]->d_un.d_ptr);

      if (__builtin_expect (COMPARE_AND_SWAP (&ftab[symidx], (ElfW(Addr)) NULL,
                                    fdesc), 1))
      {
        /* Noone has updated the entry and the new function
           descriptor has been installed.  */
#if 0
        const char *strtab
          = (const void *) D_PTR (map, l_info[DT_STRTAB]);

        ELF_MACHINE_LOAD_ADDRESS (l, local);
        if (l->root != &l->boot_table
            || l->boot_table.first_unused > 20)
          _dl_debug_printf ("created fdesc symbol `%s' at %lx\n",
                        strtab + sym->st_name, ftab[symidx]);
#endif
        break;
      }
      else
      {
        /* We created a duplicated function descriptor. We put it on
           free-list.  */
        struct fdesc *f = (struct fdesc *) fdesc;

        ELF_MACHINE_LOAD_ADDRESS (l, local);

        do
          f->ip = (ElfW(Addr)) l->free_list;
        while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list,
                             f->ip, fdesc));
      }
    }

  return ftab[symidx];
}


void
_dl_unmap (struct link_map *map)
{
  ElfW(Addr) *ftab = map->l_mach.fptr_table;
  struct fdesc *head = NULL, *tail = NULL;
  size_t i;

  __munmap ((void *) map->l_map_start,
          map->l_map_end - map->l_map_start);

  if (ftab == NULL)
    return;

  /* String together the fdesc structures that are being freed.  */
  for (i = 0; i < map->l_mach.fptr_table_len; ++i)
    {
      if (ftab[i])
      {
        *(struct fdesc **) ftab[i] = head;
        head = (struct fdesc *) ftab[i];
        if (tail == NULL)
          tail = head;
      }
    }

  /* Prepend the new list to the free_list: */
  if (tail)
    do
      tail->ip = (ElfW(Addr)) local.free_list;
    while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &local.free_list,
                         tail->ip, (ElfW(Addr)) head));

  __munmap (ftab, (map->l_mach.fptr_table_len
               * sizeof (map->l_mach.fptr_table[0])));

  map->l_mach.fptr_table = NULL;
}


ElfW(Addr)
_dl_lookup_address (const void *address)
{
  ElfW(Addr) addr = (ElfW(Addr)) address;
  struct fdesc_table *t;
  unsigned long int i;

  for (t = local.root; t != NULL; t = t->next)
    {
      i = (struct fdesc *) addr - &t->fdesc[0];
      if (i < t->first_unused && addr == (ElfW(Addr)) &t->fdesc[i])
      {
        addr = t->fdesc[i].ip;
        break;
      }
    }

  return addr;
}

Generated by  Doxygen 1.6.0   Back to index