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Patch 2/4 of the effort to make TLS access async-signal-safe.

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Add a signal-safe malloc replacement.

2013-12-18  Andrew Hunter  <ahh@google.com>

	* sysdeps/generic/ldsodefs.h (__signal_safe_memalign): New prototype.
	(__signal_safe_malloc, __signal_safe_free): Likewise.
	(__signal_safe_realloc, __signal_safe_calloc): Likewise.
	* elf/dl-misc.c (__signal_safe_allocator_header): New struct.
	(__signal_safe_memalign, __signal_safe_malloc): New function.
	(__signal_safe_free, __signal_safe_realloc): Likewise.
	(__signal_safe_calloc): Likewise.
	* elf/dl-tls.c (allocate_dtv, _dl_clear_dtv): Call signal-safe
	functions.
	(_dl_deallocate_tls, _dl_update_slotinfo): Likewise.
This commit is contained in:
Paul Pluzhnikov
2013-12-18 16:46:18 -08:00
parent 35e8f7ab94
commit 1f33d36a8a
4 changed files with 169 additions and 16 deletions
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34
elf/dl-tls.c
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@ -293,7 +293,7 @@ allocate_dtv (void *result)
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 = calloc (dtv_length + 2, sizeof (dtv_t));
dtv = __signal_safe_calloc (dtv_length + 2, sizeof (dtv_t));
if (dtv != NULL)
{
/* This is the initial length of the dtv. */
@ -470,7 +470,7 @@ _dl_clear_dtv (dtv_t *dtv)
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
if (! dtv[1 + cnt].pointer.is_static
&& dtv[1 + cnt].pointer.val != TLS_DTV_UNALLOCATED)
free (dtv[1 + cnt].pointer.val);
__signal_safe_free (dtv[1 + cnt].pointer.val);
memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t));
}
@ -491,11 +491,11 @@ _dl_deallocate_tls (void *tcb, bool dealloc_tcb)
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
if (! dtv[1 + cnt].pointer.is_static
&& dtv[1 + cnt].pointer.val != TLS_DTV_UNALLOCATED)
free (dtv[1 + cnt].pointer.val);
__signal_safe_free (dtv[1 + cnt].pointer.val);
/* The array starts with dtv[-1]. */
if (dtv != GL(dl_initial_dtv))
free (dtv - 1);
__signal_safe_free (dtv - 1);
if (dealloc_tcb)
{
@ -537,8 +537,7 @@ static void *
allocate_and_init (struct link_map *map)
{
void *newp;
newp = __libc_memalign (map->l_tls_align, map->l_tls_blocksize);
newp = __signal_safe_memalign (map->l_tls_align, map->l_tls_blocksize);
if (newp == NULL)
oom ();
@ -608,25 +607,27 @@ _dl_update_slotinfo (unsigned long int req_modid)
if (gen <= dtv[0].counter)
continue;
size_t modid = total + cnt;
/* If there is no map this means the entry is empty. */
struct link_map *map = listp->slotinfo[cnt].map;
if (map == NULL)
{
/* If this modid was used at some point the memory
might still be allocated. */
if (! dtv[total + cnt].pointer.is_static
&& dtv[total + cnt].pointer.val != TLS_DTV_UNALLOCATED)
if (dtv[-1].counter >= modid
&& !dtv[modid].pointer.is_static
&& dtv[modid].pointer.val != TLS_DTV_UNALLOCATED)
{
free (dtv[total + cnt].pointer.val);
dtv[total + cnt].pointer.val = TLS_DTV_UNALLOCATED;
__signal_safe_free (dtv[modid].pointer.val);
dtv[modid].pointer.val = TLS_DTV_UNALLOCATED;
}
continue;
}
assert (modid == map->l_tls_modid);
/* 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)
{
/* Reallocate the dtv. */
@ -640,17 +641,18 @@ _dl_update_slotinfo (unsigned long int req_modid)
{
/* This is the initial dtv that was allocated
during rtld startup using the dl-minimal.c
malloc instead of the real malloc. We can't
malloc instead of the real allocator. We can't
free it, we have to abandon the old storage. */
newp = malloc ((2 + newsize) * sizeof (dtv_t));
newp = __signal_safe_malloc (
(2 + newsize) * sizeof (dtv_t));
if (newp == NULL)
oom ();
memcpy (newp, &dtv[-1], (2 + oldsize) * sizeof (dtv_t));
}
else
{
newp = realloc (&dtv[-1],
newp = __signal_safe_realloc (&dtv[-1],
(2 + newsize) * sizeof (dtv_t));
if (newp == NULL)
oom ();
@ -680,7 +682,7 @@ _dl_update_slotinfo (unsigned long int req_modid)
deallocate even if it is this dtv entry we are
supposed to load. The reason is that we call
memalign and not malloc. */
free (dtv[modid].pointer.val);
__signal_safe_free (dtv[modid].pointer.val);
/* This module is loaded dynamically- We defer memory
allocation. */