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glibc/sysdeps/generic/dl-fptr.c

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/* Manage function descriptors. Generic version.
Copyright (C) 1999,2000,2001,2002,2003 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), (old), (new))
#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 * GL(dl_pagesize);
new_table = __mmap (NULL, *size,
PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
if (new_table == MAP_FAILED)
INTUSE(_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) *
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]) + GL(dl_pagesize) - 1)
& -GL(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)
INTUSE(_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)
INTUSE(_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;
}
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