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glibc/elf/dl-tls.c
James Y Knight 04938f76dd Fix memory leak in TLS allocation
2021-08-27 17:26:04 -07:00

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/* Thread-local storage handling in the ELF dynamic linker. Generic version.
Copyright (C) 2002-2018 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/>. */
#include <assert.h>
#include <atomic.h>
#include <errno.h>
#include <libintl.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/param.h>
#include <atomic.h>
#include <tls.h>
#include <dl-tls.h>
#include <ldsodefs.h>
static void _dl_print_dtv(const char *msg, dtv_t *dtv, int numentries);
/* Amount of excess space to allocate in the static TLS area
to allow dynamic loading of modules defining IE-model TLS data. */
#define TLS_STATIC_SURPLUS 64 + DL_NNS * 100
/* Out-of-memory handler. */
static void
__attribute__ ((__noreturn__))
oom (void)
{
_dl_fatal_printf ("cannot allocate memory for thread-local data: ABORT\n");
}
size_t
_dl_next_tls_modid (void)
{
size_t result;
if (__builtin_expect (GL(dl_tls_dtv_gaps), false))
{
size_t disp = 0;
struct dtv_slotinfo_list *runp = GL(dl_tls_dtv_slotinfo_list);
/* Note that this branch will never be executed during program
start since there are no gaps at that time. Therefore it
does not matter that the dl_tls_dtv_slotinfo is not allocated
yet when the function is called for the first times.
NB: the offset +1 is due to the fact that DTV[0] is used
for something else. */
result = GL(dl_tls_static_nelem) + 1;
if (result <= GL(dl_tls_max_dtv_idx))
do
{
while (result - disp < runp->len)
{
if (runp->slotinfo[result - disp].map == NULL)
break;
++result;
assert (result <= GL(dl_tls_max_dtv_idx) + 1);
}
if (result - disp < runp->len)
break;
disp += runp->len;
}
while ((runp = runp->next) != NULL);
if (result > GL(dl_tls_max_dtv_idx))
{
/* The new index must indeed be exactly one higher than the
previous high. */
assert (result == GL(dl_tls_max_dtv_idx) + 1);
/* There is no gap anymore. */
GL(dl_tls_dtv_gaps) = false;
goto nogaps;
}
}
else
{
/* No gaps, allocate a new entry. */
nogaps:
result = ++GL(dl_tls_max_dtv_idx);
}
return result;
}
size_t
_dl_count_modids (void)
{
/* It is rare that we have gaps; see elf/dl-open.c (_dl_open) where
we fail to load a module and unload it leaving a gap. If we don't
have gaps then the number of modids is the current maximum so
return that. */
if (__glibc_likely (!GL(dl_tls_dtv_gaps)))
return GL(dl_tls_max_dtv_idx);
/* We have gaps and are forced to count the non-NULL entries. */
size_t n = 0;
struct dtv_slotinfo_list *runp = GL(dl_tls_dtv_slotinfo_list);
while (runp != NULL)
{
for (size_t i = 0; i < runp->len; ++i)
if (runp->slotinfo[i].map != NULL)
++n;
runp = runp->next;
}
return n;
}
#ifdef SHARED
void
_dl_determine_tlsoffset (void)
{
size_t max_align = TLS_TCB_ALIGN;
size_t freetop = 0;
size_t freebottom = 0;
/* The first element of the dtv slot info list is allocated. */
assert (GL(dl_tls_dtv_slotinfo_list) != NULL);
/* There is at this point only one element in the
dl_tls_dtv_slotinfo_list list. */
assert (GL(dl_tls_dtv_slotinfo_list)->next == NULL);
struct dtv_slotinfo *slotinfo = GL(dl_tls_dtv_slotinfo_list)->slotinfo;
/* Determining the offset of the various parts of the static TLS
block has several dependencies. In addition we have to work
around bugs in some toolchains.
Each TLS block from the objects available at link time has a size
and an alignment requirement. The GNU ld computes the alignment
requirements for the data at the positions *in the file*, though.
I.e, it is not simply possible to allocate a block with the size
of the TLS program header entry. The data is layed out assuming
that the first byte of the TLS block fulfills
p_vaddr mod p_align == &TLS_BLOCK mod p_align
This means we have to add artificial padding at the beginning of
the TLS block. These bytes are never used for the TLS data in
this module but the first byte allocated must be aligned
according to mod p_align == 0 so that the first byte of the TLS
block is aligned according to p_vaddr mod p_align. This is ugly
and the linker can help by computing the offsets in the TLS block
assuming the first byte of the TLS block is aligned according to
p_align.
The extra space which might be allocated before the first byte of
the TLS block need not go unused. The code below tries to use
that memory for the next TLS block. This can work if the total
memory requirement for the next TLS block is smaller than the
gap. */
#if TLS_TCB_AT_TP
/* We simply start with zero. */
size_t offset = 0;
for (size_t cnt = 0; slotinfo[cnt].map != NULL; ++cnt)
{
assert (cnt < GL(dl_tls_dtv_slotinfo_list)->len);
size_t firstbyte = (-slotinfo[cnt].map->l_tls_firstbyte_offset
& (slotinfo[cnt].map->l_tls_align - 1));
size_t off;
max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align);
if (freebottom - freetop >= slotinfo[cnt].map->l_tls_blocksize)
{
off = roundup (freetop + slotinfo[cnt].map->l_tls_blocksize
- firstbyte, slotinfo[cnt].map->l_tls_align)
+ firstbyte;
if (off <= freebottom)
{
freetop = off;
/* XXX For some architectures we perhaps should store the
negative offset. */
slotinfo[cnt].map->l_tls_offset = off;
continue;
}
}
off = roundup (offset + slotinfo[cnt].map->l_tls_blocksize - firstbyte,
slotinfo[cnt].map->l_tls_align) + firstbyte;
if (off > offset + slotinfo[cnt].map->l_tls_blocksize
+ (freebottom - freetop))
{
freetop = offset;
freebottom = off - slotinfo[cnt].map->l_tls_blocksize;
}
offset = off;
/* XXX For some architectures we perhaps should store the
negative offset. */
slotinfo[cnt].map->l_tls_offset = off;
}
GL(dl_tls_static_used) = offset;
GL(dl_tls_static_size) = (roundup (offset + TLS_STATIC_SURPLUS, max_align)
+ TLS_TCB_SIZE);
#elif TLS_DTV_AT_TP
/* The TLS blocks start right after the TCB. */
size_t offset = TLS_TCB_SIZE;
for (size_t cnt = 0; slotinfo[cnt].map != NULL; ++cnt)
{
assert (cnt < GL(dl_tls_dtv_slotinfo_list)->len);
size_t firstbyte = (-slotinfo[cnt].map->l_tls_firstbyte_offset
& (slotinfo[cnt].map->l_tls_align - 1));
size_t off;
max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align);
if (slotinfo[cnt].map->l_tls_blocksize <= freetop - freebottom)
{
off = roundup (freebottom, slotinfo[cnt].map->l_tls_align);
if (off - freebottom < firstbyte)
off += slotinfo[cnt].map->l_tls_align;
if (off + slotinfo[cnt].map->l_tls_blocksize - firstbyte <= freetop)
{
slotinfo[cnt].map->l_tls_offset = off - firstbyte;
freebottom = (off + slotinfo[cnt].map->l_tls_blocksize
- firstbyte);
continue;
}
}
off = roundup (offset, slotinfo[cnt].map->l_tls_align);
if (off - offset < firstbyte)
off += slotinfo[cnt].map->l_tls_align;
slotinfo[cnt].map->l_tls_offset = off - firstbyte;
if (off - firstbyte - offset > freetop - freebottom)
{
freebottom = offset;
freetop = off - firstbyte;
}
offset = off + slotinfo[cnt].map->l_tls_blocksize - firstbyte;
}
GL(dl_tls_static_used) = offset;
GL(dl_tls_static_size) = roundup (offset + TLS_STATIC_SURPLUS,
TLS_TCB_ALIGN);
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
/* The alignment requirement for the static TLS block. */
GL(dl_tls_static_align) = max_align;
}
#endif /* SHARED */
static void *
allocate_dtv (void *result)
{
dtv_t *dtv;
size_t dtv_length;
/* We allocate a few more elements in the dtv than are needed for the
initial set of modules. This should avoid in most cases expansions
of the dtv. */
dtv_length = GL(dl_tls_max_dtv_idx) + DTV_SURPLUS;
dtv = __signal_safe_calloc (dtv_length + 2, sizeof (dtv_t));
if (dtv != NULL)
{
/* This is the initial length of the dtv. */
dtv[0].counter = dtv_length;
/* The rest of the dtv (including the generation counter) is
Initialize with zero to indicate nothing there. */
/* Add the dtv to the thread data structures. */
INSTALL_DTV (result, dtv);
}
else
result = NULL;
return result;
}
/* Get size and alignment requirements of the static TLS block. */
void
_dl_get_tls_static_info (size_t *sizep, size_t *alignp)
{
*sizep = GL(dl_tls_static_size);
*alignp = GL(dl_tls_static_align);
}
/* Derive the location of the pointer to the start of the original
allocation (before alignment) from the pointer to the TCB. */
static inline void **
tcb_to_pointer_to_free_location (void *tcb)
{
#if TLS_TCB_AT_TP
/* The TCB follows the TLS blocks, and the pointer to the front
follows the TCB. */
void **original_pointer_location = tcb + TLS_TCB_SIZE;
#elif TLS_DTV_AT_TP
/* The TCB comes first, preceded by the pre-TCB, and the pointer is
before that. */
void **original_pointer_location = tcb - TLS_PRE_TCB_SIZE - sizeof (void *);
#endif
return original_pointer_location;
}
void *
_dl_allocate_tls_storage (void)
{
void *result;
size_t size = GL(dl_tls_static_size);
#if TLS_DTV_AT_TP
/* Memory layout is:
[ TLS_PRE_TCB_SIZE ] [ TLS_TCB_SIZE ] [ TLS blocks ]
^ This should be returned. */
size += TLS_PRE_TCB_SIZE;
#endif
/* Perform the allocation. Reserve space for the required alignment
and the pointer to the original allocation. */
size_t alignment = GL(dl_tls_static_align);
void *allocated = malloc (size + alignment + sizeof (void *));
if (__glibc_unlikely (allocated == NULL))
return NULL;
/* Perform alignment and allocate the DTV. */
#if TLS_TCB_AT_TP
/* The TCB follows the TLS blocks, which determine the alignment.
(TCB alignment requirements have been taken into account when
calculating GL(dl_tls_static_align).) */
void *aligned = (void *) roundup ((uintptr_t) allocated, alignment);
result = aligned + size - TLS_TCB_SIZE;
/* Clear the TCB data structure. We can't ask the caller (i.e.
libpthread) to do it, because we will initialize the DTV et al. */
memset (result, '\0', TLS_TCB_SIZE);
#elif TLS_DTV_AT_TP
/* Pre-TCB and TCB come before the TLS blocks. The layout computed
in _dl_determine_tlsoffset assumes that the TCB is aligned to the
TLS block alignment, and not just the TLS blocks after it. This
can leave an unused alignment gap between the TCB and the TLS
blocks. */
result = (void *) roundup
(sizeof (void *) + TLS_PRE_TCB_SIZE + (uintptr_t) allocated,
alignment);
/* Clear the TCB data structure and TLS_PRE_TCB_SIZE bytes before
it. We can't ask the caller (i.e. libpthread) to do it, because
we will initialize the DTV et al. */
memset (result - TLS_PRE_TCB_SIZE, '\0', TLS_PRE_TCB_SIZE + TLS_TCB_SIZE);
#endif
/* Record the value of the original pointer for later
deallocation. */
*tcb_to_pointer_to_free_location (result) = allocated;
result = allocate_dtv (result);
if (result == NULL)
free (allocated);
return result;
}
#ifndef SHARED
extern dtv_t _dl_static_dtv[];
# define _dl_initial_dtv (&_dl_static_dtv[1])
#endif
static dtv_t *
_dl_resize_dtv (dtv_t *dtv)
{
/* Resize the dtv. */
dtv_t *newp;
/* Load GL(dl_tls_max_dtv_idx) atomically since it may be written to by
other threads concurrently. */
size_t newsize
= atomic_load_acquire (&GL(dl_tls_max_dtv_idx)) + DTV_SURPLUS;
size_t oldsize = dtv[-1].counter;
if (dtv == GL(dl_initial_dtv))
{
/* This is the initial dtv that was either statically allocated in
__libc_setup_tls or allocated during rtld startup using the
dl-minimal.c malloc instead of the real malloc. We can't free
it, we have to abandon the old storage. */
newp = __signal_safe_malloc ((2 + newsize) * sizeof (dtv_t));
if (newp == NULL)
oom ();
memcpy (newp, &dtv[-1], (2 + oldsize) * sizeof (dtv_t));
}
else
{
newp = __signal_safe_realloc (&dtv[-1],
(2 + newsize) * sizeof (dtv_t));
if (newp == NULL)
oom ();
}
newp[0].counter = newsize;
/* Clear the newly allocated part. */
memset (newp + 2 + oldsize, '\0',
(newsize - oldsize) * sizeof (dtv_t));
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("Resized dtv 0x%0*Zx, size %lu, to dtv 0x%0*Zx, size %lu\n",
(int) sizeof (void *) * 2, (unsigned long int) dtv,
oldsize,
(int) sizeof (void *) * 2, (unsigned long int) &newp[1],
newsize);
/* Return the generation counter. */
return &newp[1];
}
void *
_dl_allocate_tls_init (void *result)
{
if (result == NULL)
/* The memory allocation failed. */
return NULL;
dtv_t *dtv = GET_DTV (result);
struct dtv_slotinfo_list *listp;
size_t total = 0;
size_t maxgen = 0;
/* Check if the current dtv is big enough. */
if (dtv[-1].counter < GL(dl_tls_max_dtv_idx))
{
/* Resize the dtv. */
dtv = _dl_resize_dtv (dtv);
/* Install this new dtv in the thread data structures. */
INSTALL_DTV (result, &dtv[-1]);
}
/* We have to prepare the dtv for all currently loaded modules using
TLS. For those which are dynamically loaded we add the values
indicating deferred allocation. */
listp = GL(dl_tls_dtv_slotinfo_list);
while (1)
{
size_t cnt;
for (cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
{
struct link_map *map;
void *dest;
/* Check for the total number of used slots. */
if (total + cnt > GL(dl_tls_max_dtv_idx))
break;
map = listp->slotinfo[cnt].map;
if (map == NULL)
/* Unused entry. */
continue;
/* Keep track of the maximum generation number. This might
not be the generation counter. */
assert (listp->slotinfo[cnt].gen <= GL(dl_tls_generation));
maxgen = MAX (maxgen, listp->slotinfo[cnt].gen);
dtv[map->l_tls_modid].pointer.val = TLS_DTV_UNALLOCATED;
dtv[map->l_tls_modid].pointer.to_free = NULL;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("_dl_allocate_tls_init unallocates %sdtv 0x%0*Zx module %lu\n",
(dtv == THREAD_DTV () ? "own " : ""),
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
map->l_tls_modid);
if (map->l_tls_offset == NO_TLS_OFFSET
|| map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET)
continue;
assert (map->l_tls_modid == total + cnt);
assert (map->l_tls_blocksize >= map->l_tls_initimage_size);
#if TLS_TCB_AT_TP
assert ((size_t) map->l_tls_offset >= map->l_tls_blocksize);
dest = (char *) result - map->l_tls_offset;
#elif TLS_DTV_AT_TP
dest = (char *) result + map->l_tls_offset;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
/* Set up the DTV entry. The simplified __tls_get_addr that
some platforms use in static programs requires it. */
dtv[map->l_tls_modid].pointer.val = dest;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("_dl_allocate_tls_init sets %sdtv 0x%0*Zx module %lu to 0x%0*Zx\n",
(dtv == THREAD_DTV () ? "own " : ""),
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
map->l_tls_modid,
(int) sizeof (void *) * 2,
(unsigned long int) dest);
/* Copy the initialization image and clear the BSS part. */
memset (__mempcpy (dest, map->l_tls_initimage,
map->l_tls_initimage_size), '\0',
map->l_tls_blocksize - map->l_tls_initimage_size);
}
total += cnt;
if (total >= GL(dl_tls_max_dtv_idx))
break;
listp = listp->next;
assert (listp != NULL);
}
/* The DTV version is up-to-date now. */
dtv[0].counter = maxgen;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_print_dtv ("_dl_allocate_tls_init return ", dtv, 10);
return result;
}
rtld_hidden_def (_dl_allocate_tls_init)
void *
_dl_allocate_tls (void *mem)
{
return _dl_allocate_tls_init (mem == NULL
? _dl_allocate_tls_storage ()
: allocate_dtv (mem));
}
rtld_hidden_def (_dl_allocate_tls)
/* Clear the given dtv. (We have this here because __signal_safe_free is
not visible to nptl/allocatestack.c.) */
void
_dl_clear_dtv (dtv_t *dtv)
{
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
__signal_safe_free (dtv[1 + cnt].pointer.to_free);
memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t));
}
rtld_hidden_def (_dl_clear_dtv)
void
_dl_deallocate_tls (void *tcb, bool dealloc_tcb)
{
dtv_t *dtv = GET_DTV (tcb);
/* We need to free the memory allocated for non-static TLS. */
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
__signal_safe_free (dtv[1 + cnt].pointer.to_free);
/* The array starts with dtv[-1]. */
if (dtv != GL(dl_initial_dtv))
__signal_safe_free (dtv - 1);
if (dealloc_tcb)
free (*tcb_to_pointer_to_free_location (tcb));
}
rtld_hidden_def (_dl_deallocate_tls)
#ifdef SHARED
/* The __tls_get_addr function has two basic forms which differ in the
arguments. The IA-64 form takes two parameters, the module ID and
offset. The form used, among others, on IA-32 takes a reference to
a special structure which contain the same information. The second
form seems to be more often used (in the moment) so we default to
it. Users of the IA-64 form have to provide adequate definitions
of the following macros. */
# ifndef GET_ADDR_ARGS
# define GET_ADDR_ARGS tls_index *ti
# define GET_ADDR_PARAM ti
# endif
# ifndef GET_ADDR_MODULE
# define GET_ADDR_MODULE ti->ti_module
# endif
# ifndef GET_ADDR_OFFSET
# define GET_ADDR_OFFSET ti->ti_offset
# endif
/* Allocate one DTV entry. */
static struct dtv_pointer
allocate_dtv_entry (size_t alignment, size_t size)
{
if (powerof2 (alignment) && alignment <= _Alignof (max_align_t))
{
/* The alignment is supported by malloc. */
void *ptr = malloc (size);
return (struct dtv_pointer) { ptr, ptr };
}
/* Emulate memalign to by manually aligning a pointer returned by
malloc. First compute the size with an overflow check. */
size_t alloc_size = size + alignment;
if (alloc_size < size)
return (struct dtv_pointer) {};
/* Perform the allocation. This is the pointer we need to free
later. */
void *start = malloc (alloc_size);
if (start == NULL)
return (struct dtv_pointer) {};
/* Find the aligned position within the larger allocation. */
void *aligned = (void *) roundup ((uintptr_t) start, alignment);
return (struct dtv_pointer) { .val = aligned, .to_free = start };
}
static struct dtv_pointer
allocate_and_init (struct link_map *map)
{
struct dtv_pointer result = allocate_dtv_entry
(map->l_tls_align, map->l_tls_blocksize);
if (result.val == NULL)
oom ();
/* Initialize the memory. */
memset (__mempcpy (result.val, map->l_tls_initimage,
map->l_tls_initimage_size),
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
return result;
}
static void
signal_safe_allocate_and_init (dtv_t *dtv, struct link_map *map)
{
void *newp;
newp = __signal_safe_memalign (map->l_tls_align, map->l_tls_blocksize);
if (newp == NULL)
oom ();
/* Initialize the memory. Since this is our thread's space, we are
under a signal mask, and no one has touched this section before,
we can safely just overwrite whatever's there. */
memset (__mempcpy (newp, map->l_tls_initimage,
map->l_tls_initimage_size),
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
dtv->pointer.val = newp;
dtv->pointer.to_free = newp;
}
struct link_map *
_dl_update_slotinfo (unsigned long int req_modid)
{
struct link_map *the_map = NULL;
dtv_t *dtv = THREAD_DTV ();
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
// (should mention module name?)
_dl_debug_printf ("Updating slot info for own dtv 0x%0*Zx module %lu\n",
(int) sizeof (void *) * 2, (unsigned long int) dtv,
req_modid);
/* The global dl_tls_dtv_slotinfo array contains for each module
index the generation counter current when the entry was created.
This array never shrinks so that all module indices which were
valid at some time can be used to access it. Before the first
use of a new module index in this function the array was extended
appropriately. Access also does not have to be guarded against
modifications of the array. It is assumed that pointer-size
values can be read atomically even in SMP environments. It is
possible that other threads at the same time dynamically load
code and therefore add to the slotinfo list. This is a problem
since we must not pick up any information about incomplete work.
The solution to this is to ignore all dtv slots which were
created after the one we are currently interested. We know that
dynamic loading for this module is completed and this is the last
load operation we know finished. */
unsigned long int idx = req_modid;
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
while (idx >= listp->len)
{
idx -= listp->len;
listp = listp->next;
}
if (dtv[0].counter < listp->slotinfo[idx].gen)
{
/* The generation counter for the slot is higher than what the
current dtv implements. We have to update the whole dtv but
only those entries with a generation counter <= the one for
the entry we need. */
size_t new_gen = listp->slotinfo[idx].gen;
size_t total = 0;
sigset_t old;
if (GLRO(dl_async_signal_safe)) {
_dl_mask_all_signals (&old);
/* We use the signal mask as a lock against reentrancy here.
Check that a signal taken before the lock didn't already
update us. */
dtv = THREAD_DTV ();
if (dtv[0].counter >= listp->slotinfo[idx].gen)
{
_dl_unmask_signals (&old);
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("Slot info update for own dtv 0x%0*Zx module %lu done, exiting early\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
req_modid);
return the_map;
}
}
/* We have to look through the entire dtv slotinfo list. */
listp = GL(dl_tls_dtv_slotinfo_list);
do
{
for (size_t cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
{
size_t gen = listp->slotinfo[cnt].gen;
if (gen > new_gen)
/* This is a slot for a generation younger than the
one we are handling now. It might be incompletely
set up so ignore it. */
continue;
/* If the entry is older than the current dtv layout we
know we don't have to handle it. */
if (gen <= dtv[0].counter)
continue;
/* If there is no map this means the entry is empty. */
struct link_map *map = listp->slotinfo[cnt].map;
if (map == NULL)
{
if (dtv[-1].counter >= total + cnt)
{
/* If this modid was used at some point the memory
might still be allocated. */
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("Slot info update for own dtv 0x%0*Zx module %lu unallocating 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
total + cnt,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[total + cnt].pointer.val);
__signal_safe_free (dtv[total + cnt].pointer.to_free);
dtv[total + cnt].pointer.val = TLS_DTV_UNALLOCATED;
dtv[total + cnt].pointer.to_free = NULL;
}
continue;
}
/* Check whether the current dtv array is large enough. */
size_t modid = map->l_tls_modid;
assert (total + cnt == modid);
if (dtv[-1].counter < modid)
{
/* Resize the dtv. */
dtv = _dl_resize_dtv (dtv);
assert (modid <= dtv[-1].counter);
/* Install this new dtv in the thread data
structures. */
INSTALL_NEW_DTV (dtv);
}
/* If there is currently memory allocate for this
dtv entry free it. */
/* XXX Ideally we will at some point create a memory
pool. */
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("Slot info update for own dtv 0x%0*Zx module %lu unallocating 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
modid,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[modid].pointer.val);
__signal_safe_free (dtv[modid].pointer.to_free);
dtv[modid].pointer.val = TLS_DTV_UNALLOCATED;
dtv[modid].pointer.to_free = NULL;
if (modid == req_modid)
the_map = map;
}
total += listp->len;
}
while ((listp = listp->next) != NULL);
/* This will be the new maximum generation counter. */
dtv[0].counter = new_gen;
if (GLRO(dl_async_signal_safe))
_dl_unmask_signals (&old);
}
return the_map;
}
static void *
__attribute_noinline__
tls_get_addr_tail (GET_ADDR_ARGS, dtv_t *dtv, struct link_map *the_map)
{
/* The allocation was deferred. Do it now. */
if (the_map == NULL)
{
/* Find the link map for this module. */
size_t idx = GET_ADDR_MODULE;
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
while (idx >= listp->len)
{
idx -= listp->len;
listp = listp->next;
}
the_map = listp->slotinfo[idx].map;
}
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
{
char *map_name = (the_map->l_name ? the_map->l_name : "no name");
_dl_debug_printf ("tls_get_addr_tail entry, own dtv 0x%0*Zx module %lu (%s) pointer.val = 0x%0*Zx\n",
(int) sizeof (void *) * 2, (unsigned long int) dtv,
GET_ADDR_MODULE, map_name,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[GET_ADDR_MODULE].pointer.val);
}
if (!GLRO(dl_async_signal_safe)) {
/* Make sure that, if a dlopen running in parallel forces the
variable into static storage, we'll wait until the address in the
static TLS block is set up, and use that. If we're undecided
yet, make sure we make the decision holding the lock as well. */
if (__glibc_unlikely (the_map->l_tls_offset
!= FORCED_DYNAMIC_TLS_OFFSET))
{
__rtld_lock_lock_recursive (GL(dl_load_lock));
if (__glibc_likely (the_map->l_tls_offset == NO_TLS_OFFSET))
{
the_map->l_tls_offset = FORCED_DYNAMIC_TLS_OFFSET;
__rtld_lock_unlock_recursive (GL(dl_load_lock));
}
else if (__glibc_likely (the_map->l_tls_offset
!= FORCED_DYNAMIC_TLS_OFFSET))
{
#if TLS_TCB_AT_TP
void *p = (char *) THREAD_SELF - the_map->l_tls_offset;
#elif TLS_DTV_AT_TP
void *p = (char *) THREAD_SELF + the_map->l_tls_offset + TLS_PRE_TCB_SIZE;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
__rtld_lock_unlock_recursive (GL(dl_load_lock));
dtv[GET_ADDR_MODULE].pointer.to_free = NULL;
dtv[GET_ADDR_MODULE].pointer.val = p;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail sets own dtv 0x%0*Zx module %lu pointer.val to 0x%0*Zx, returns\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2,
(unsigned long int) p);
return (char *) p + GET_ADDR_OFFSET;
}
else
__rtld_lock_unlock_recursive (GL(dl_load_lock));
}
struct dtv_pointer result = allocate_and_init (the_map);
dtv[GET_ADDR_MODULE].pointer = result;
assert (result.to_free != NULL);
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail sets own dtv 0x%0*Zx module %lu pointer.val to 0x%0*Zx, returns\n",
(int) sizeof (void *) * 2, (unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2, (unsigned long int) result.val);
return (char *) result.val + GET_ADDR_OFFSET;
} else {
sigset_t old;
_dl_mask_all_signals (&old);
/* As with update_slotinfo, we use the sigmask as a check against
reentrancy. */
if (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED)
{
_dl_unmask_signals (&old);
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail keeps own dtv pointer.val, returns\n");
return (char *) dtv[GET_ADDR_MODULE].pointer.val + GET_ADDR_OFFSET;
}
/* Synchronize against a parallel dlopen() forcing this variable
into static storage. If that happens, we have to be more careful
about initializing the area, as that dlopen() will be iterating
the threads to do so itself. */
ptrdiff_t offset = the_map->l_tls_offset;
if (offset == NO_TLS_OFFSET)
{
/* l_tls_offset starts out at NO_TLS_OFFSET, and all attempts to
change it go from NO_TLS_OFFSET to some other value. We use
compare_and_exchange to ensure only one attempt succeeds. We
don't actually need any memory ordering here, but _acq is the
weakest available. */
(void) atomic_compare_and_exchange_bool_acq (&the_map->l_tls_offset,
FORCED_DYNAMIC_TLS_OFFSET,
NO_TLS_OFFSET);
offset = the_map->l_tls_offset;
assert (offset != NO_TLS_OFFSET);
}
if (offset == FORCED_DYNAMIC_TLS_OFFSET)
{
signal_safe_allocate_and_init (&dtv[GET_ADDR_MODULE], the_map);
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail allocates own dtv 0x%0*Zx module %lu pointer.val = 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[GET_ADDR_MODULE].pointer.val);
}
/* It can happen that slot info updates will un-allocate a pointer (possibly
due to a bug elsewhere), which leaves us waiting indefinitely for the
dlopen that will never happen. Emulate the async-signal-unsafe case above
and use a static TLS address. */
else if (dtv[GET_ADDR_MODULE].pointer.val == TLS_DTV_UNALLOCATED)
{
#if TLS_TCB_AT_TP
void *p = (char *) THREAD_SELF - the_map->l_tls_offset;
#elif TLS_DTV_AT_TP
void *p = (char *) THREAD_SELF + the_map->l_tls_offset + TLS_PRE_TCB_SIZE;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
dtv[GET_ADDR_MODULE].pointer.to_free = NULL;
dtv[GET_ADDR_MODULE].pointer.val = p;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail sets unallocated own dtv 0x%0*Zx module %lu pointer.val = 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[GET_ADDR_MODULE].pointer.val);
}
else
{
void ** volatile pp = &dtv[GET_ADDR_MODULE].pointer.val;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail waiting for own dtv 0x%0*Zx module %lu to be allocated\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE);
while (atomic_forced_read (*pp) == TLS_DTV_UNALLOCATED)
{
/* for lack of a better (safe) thing to do, just spin.
Someone else (not us; it's done under a signal mask) set
this map to a static TLS offset, and they'll iterate all
threads to initialize it. They'll eventually write
to pointer.val, at which point we know they've fully
completed initialization. */
atomic_spin_nop ();
}
/* Make sure we've picked up their initialization of the actual
block; this pairs against the write barrier in
init_one_static_tls, guaranteeing that we see their write of
the tls_initimage into the static region. */
atomic_read_barrier ();
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail sees own dtv 0x%0*Zx module %lu has pointer.val = 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[GET_ADDR_MODULE].pointer.val);
}
assert (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED);
_dl_unmask_signals (&old);
return (char *) dtv[GET_ADDR_MODULE].pointer.val + GET_ADDR_OFFSET;
}
}
static struct link_map *
__attribute_noinline__
update_get_addr (GET_ADDR_ARGS)
{
struct link_map *the_map = _dl_update_slotinfo (GET_ADDR_MODULE);
dtv_t *dtv = THREAD_DTV ();
void *p = dtv[GET_ADDR_MODULE].pointer.val;
if (__glibc_unlikely (p == TLS_DTV_UNALLOCATED))
return tls_get_addr_tail (GET_ADDR_PARAM, dtv, the_map);
return (void *) p + GET_ADDR_OFFSET;
}
/* For all machines that have a non-macro version of __tls_get_addr, we
want to use rtld_hidden_proto/rtld_hidden_def in order to call the
internal alias for __tls_get_addr from ld.so. This avoids a PLT entry
in ld.so for __tls_get_addr. */
#ifndef __tls_get_addr
extern void * __tls_get_addr (GET_ADDR_ARGS);
rtld_hidden_proto (__tls_get_addr)
rtld_hidden_def (__tls_get_addr)
#endif
/* The generic dynamic and local dynamic model cannot be used in
statically linked applications. */
void *
__tls_get_addr (GET_ADDR_ARGS)
{
dtv_t *dtv = THREAD_DTV ();
if (__glibc_unlikely (dtv[0].counter != GL(dl_tls_generation)))
return update_get_addr (GET_ADDR_PARAM);
void *p = dtv[GET_ADDR_MODULE].pointer.val;
if (__glibc_unlikely (p == TLS_DTV_UNALLOCATED))
return tls_get_addr_tail (GET_ADDR_PARAM, dtv, NULL);
return (char *) p + GET_ADDR_OFFSET;
}
#endif
/* Look up the module's TLS block as for __tls_get_addr,
but never touch anything. Return null if it's not allocated yet. */
void *
_dl_tls_get_addr_soft (struct link_map *l)
{
if (__glibc_unlikely (l->l_tls_modid == 0))
/* This module has no TLS segment. */
return NULL;
dtv_t *dtv = THREAD_DTV ();
if (__glibc_unlikely (dtv[0].counter != GL(dl_tls_generation)))
{
/* This thread's DTV is not completely current,
but it might already cover this module. */
if (l->l_tls_modid >= dtv[-1].counter)
/* Nope. */
return NULL;
size_t idx = l->l_tls_modid;
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
while (idx >= listp->len)
{
idx -= listp->len;
listp = listp->next;
}
/* We've reached the slot for this module.
If its generation counter is higher than the DTV's,
this thread does not know about this module yet. */
if (dtv[0].counter < listp->slotinfo[idx].gen)
return NULL;
}
void *data = dtv[l->l_tls_modid].pointer.val;
if (__glibc_unlikely (data == TLS_DTV_UNALLOCATED))
/* The DTV is current, but this thread has not yet needed
to allocate this module's segment. */
data = NULL;
return data;
}
void
_dl_add_to_slotinfo (struct link_map *l)
{
/* Now that we know the object is loaded successfully add
modules containing TLS data to the dtv info table. We
might have to increase its size. */
struct dtv_slotinfo_list *listp;
struct dtv_slotinfo_list *prevp;
size_t idx = l->l_tls_modid;
/* Find the place in the dtv slotinfo list. */
listp = GL(dl_tls_dtv_slotinfo_list);
prevp = NULL; /* Needed to shut up gcc. */
do
{
/* Does it fit in the array of this list element? */
if (idx < listp->len)
break;
idx -= listp->len;
prevp = listp;
listp = listp->next;
}
while (listp != NULL);
if (listp == NULL)
{
/* When we come here it means we have to add a new element
to the slotinfo list. And the new module must be in
the first slot. */
assert (idx == 0);
listp = prevp->next = (struct dtv_slotinfo_list *)
malloc (sizeof (struct dtv_slotinfo_list)
+ TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
if (listp == NULL)
{
/* We ran out of memory. We will simply fail this
call but don't undo anything we did so far. The
application will crash or be terminated anyway very
soon. */
/* We have to do this since some entries in the dtv
slotinfo array might already point to this
generation. */
++GL(dl_tls_generation);
_dl_signal_error (ENOMEM, "dlopen", NULL, N_("\
cannot create TLS data structures"));
}
listp->len = TLS_SLOTINFO_SURPLUS;
listp->next = NULL;
memset (listp->slotinfo, '\0',
TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
}
/* Add the information into the slotinfo data structure. */
listp->slotinfo[idx].map = l;
listp->slotinfo[idx].gen = GL(dl_tls_generation) + 1;
}
/* Return a thread id of the current thread if we are debugging tls and the
value is meaningful. */
pid_t
_dl_tls_tid (void)
{
if (!__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
return 0;
#ifdef SHARED
if (GL(dl_initial_dtv) == NULL)
return 0;
#endif
struct pthread *thr = THREAD_SELF;
return thr->tid;
}
/* Print all or part of a dtv. Note that the output may be large; for instance
nptl/tst-stack4 has dtv's with hundreds of entries. */
static void
_dl_print_dtv (const char *msg, dtv_t *dtv, int numentries)
{
size_t cnt, last_used, num_to_print, i;
cnt = dtv[-1].counter;
last_used = 0;
for (i = 1; i <= cnt; ++i)
{
if (dtv[i].pointer.val || dtv[i].pointer.to_free)
last_used = i;
}
num_to_print = last_used;
if (numentries >= 0 && numentries < num_to_print)
num_to_print = numentries;
_dl_debug_printf ("%sdtv 0x%0*Zx has %lu used of %lu entries, generation %lu\n",
msg,
(int) sizeof (void *) * 2, (unsigned long int) dtv,
last_used, cnt, dtv[0].counter);
for (i = 1; i <= num_to_print; ++i)
{
if (dtv[i].pointer.to_free == dtv[i].pointer.val)
_dl_debug_printf ("%*lu: pointer.val = 0x%0*Zx to_free = same\n",
4, i,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[i].pointer.val);
else if (dtv[i].pointer.to_free)
_dl_debug_printf ("%*lu: pointer.val = 0x%0*Zx to_free = 0x%0*Zx\n",
4, i,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[i].pointer.val,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[i].pointer.to_free);
else
_dl_debug_printf ("%*lu: pointer.val = 0x%0*Zx\n",
4, i,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[i].pointer.val);
}
if (num_to_print < last_used)
_dl_debug_printf (" [...]\n");
}
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