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/* Delayed IFUNC processing.
Copyright (C) 2017 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, see
<http://www.gnu.org/licenses/>. */
#ifdef HAVE_IFUNC
# include <dl-ifunc.h>
# include <errno.h>
# include <ldsodefs.h>
# include <sys/mman.h>
# include <unistd.h>
/* Machine-specific definitions. */
# include <dl-ifunc-reloc.h>
/* This struct covers a whole page containing individual struct
dl_ifunc_relocation elements, which are allocated individually by
allocate_relocation below. */
struct dl_ifunc_relocation_array
{
struct dl_ifunc_relocation_array *next;
struct dl_ifunc_relocation data[];
};
/* Global list of allocated arrays of struct dl_ifunc_relocation
elements. */
static struct dl_ifunc_relocation_array *array_list;
/* Position of the next allocation in the current array used as the
source of struct dl_ifunc_relocation allocations. */
static struct dl_ifunc_relocation *next_alloc;
static unsigned int remaining_alloc;
/* Allocate a new struct dl_ifunc_relocation_array object. Return the
first data object therein. Update array_list, next_alloc,
remaining_alloc. This function assumes taht remaining_alloc is
zero. */
static struct dl_ifunc_relocation *
allocate_array (void)
{
size_t page_size = GLRO(dl_pagesize);
void *ptr = __mmap (NULL, page_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (ptr == MAP_FAILED)
_dl_signal_error (ENOMEM, NULL, NULL,
"cannot allocate IFUNC resolver information");
struct dl_ifunc_relocation_array *new_head = ptr;
new_head->next = array_list;
array_list = new_head;
next_alloc = &new_head->data[1];
/* The function returns the first element of the new array. */
remaining_alloc
= (page_size - offsetof (struct dl_ifunc_relocation_array, data))
/ sizeof (new_head->data[0]) - 1;
return &new_head->data[0];
}
/* Allocate whone struct dl_ifunc_relocation element from the active
array. Updated next_alloc, remaining_alloc, and potentially
array_list. */
static struct dl_ifunc_relocation *
allocate_ifunc (void)
{
if (remaining_alloc == 0)
return allocate_array ();
--remaining_alloc;
return next_alloc++;
}
/* Deallocate the list of array allocations starting at
array_list. */
static void
free_allocations (void)
{
size_t page_size = GLRO(dl_pagesize);
struct dl_ifunc_relocation_array *p = array_list;
while (p != NULL)
{
struct dl_ifunc_relocation_array *next = p->next;
munmap (p, page_size);
p = next;
}
/* Restart from scratch if _dl_ifunc_record_reloc is called
again. */
array_list = NULL;
next_alloc = NULL;
remaining_alloc = 0;
}
/* Process all delayed IFUNC resolutions for IFUNC_MAP alone. */
static void
apply_relocations (struct link_map *ifunc_map)
{
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
&& ifunc_map->l_name != NULL)
_dl_debug_printf ("applying delayed IFUNC relocations against %s\n",
ifunc_map->l_name);
struct dl_ifunc_relocation *p = ifunc_map->l_ifunc_relocations;
unsigned int count = 0;
while (p != NULL)
{
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
&& ifunc_map->l_name != NULL)
{
if (p->ifunc_sym == NULL)
_dl_debug_printf ("processing relative IFUNC relocation for %s\n",
ifunc_map->l_name);
else
{
const char *strtab = (const char *) D_PTR (ifunc_map, l_info[DT_STRTAB]);
_dl_debug_printf ("binding IFUNC symbol %s in %s against %s\n",
strtab + p->ifunc_sym->st_name,
p->reloc_map->l_name, ifunc_map->l_name);
}
}
_dl_ifunc_process_relocation (p, ifunc_map);
p = p->next;
++count;
}
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
&& ifunc_map->l_name != NULL)
_dl_debug_printf ("%u delayed IFUNC relocations performed against %s\n",
count, ifunc_map->l_name);
/* No deallocation takes place here. All allocated objects are
freed in bulk by a later call to free_allocations. */
ifunc_map->l_ifunc_relocations = NULL;
}
void internal_function
_dl_ifunc_record_reloc (struct link_map *reloc_map,
const ElfW(Rela) *reloc,
ElfW(Addr) *reloc_addr,
struct link_map *ifunc_map,
const ElfW(Sym) *ifunc_sym)
{
/* Add the delayed IFUNC relocation to the list for ifunc_map. */
struct dl_ifunc_relocation *ifunc = allocate_ifunc ();
*ifunc = (struct dl_ifunc_relocation)
{
.reloc_map = reloc_map,
.reloc = reloc,
.reloc_addr = reloc_addr,
.ifunc_sym = ifunc_sym,
.next = ifunc_map->l_ifunc_relocations,
};
ifunc_map->l_ifunc_relocations = ifunc;
}
void internal_function
_dl_ifunc_apply_relocations (struct link_map *new)
{
/* Traverse the search list in reverse order, in case an IFUNC
resolver calls into one its dependencies, and those dependency
needs IFUNC resolution as well. */
struct link_map **r_list = new->l_searchlist.r_list;
for (unsigned int i = new->l_searchlist.r_nlist; i-- > 0; )
{
struct link_map *l = r_list[i];
if (l->l_ifunc_relocations != NULL)
apply_relocations (l);
}
free_allocations ();
}
void internal_function
_dl_ifunc_clear_relocations (struct link_map *map)
{
Lmid_t nsid = map->l_ns;
struct link_namespaces *ns = &GL(dl_ns)[nsid];
for (struct link_map *l = ns->_ns_loaded; l != NULL; l = l->l_next)
l->l_ifunc_relocations = NULL;
free_allocations ();
}
#endif /* HAVE_IFUNC */
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