2005-12-13 Ulrich Drepper <drepper@redhat.com>

1 files changed, 323 insertions, 0 deletions

diff --git a/elf/dl-fptr.c b/elf/dl-fptr.c
new file mode 100644
index 0000000..78beecf
--- /dev/null
+++ b/elf/dl-fptr.c
@@ -0,0 +1,323 @@
+/* Manage function descriptors.  Generic version.
+   Copyright (C) 1999,2000,2001,2002,2003,2004 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) \
+  (atomic_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;
+}