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_dl_fini: Rewrite to use VLA instead of extend_alloca

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In this case, extend_alloca is used to work around the lack of
deallocation on scope exit.  A VLA is automatically deallocated in this
way, so it is the more fitting approach.

To implement this, it is necessary to eliminate the goto.  In addition,
this change eliminates the trivially-true assert; the assert is always
skipped if nloaded > 0.

	* elf/dl-fini.c (_dl_fini): Rewrite to use variable-length array
	instead of extend_alloca.  Change control flow to avoid a goto.
	Remove assert which is trivially always true.
This commit is contained in:
Florian Weimer 2015-10-29 09:26:03 +01:00
parent 2145f97cee
commit 58acfe6fa7
2 changed files with 93 additions and 102 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2015-10-29 Florian Weimer <fweimer@redhat.com>
* elf/dl-fini.c (_dl_fini): Rewrite to use variable-length array
instead of extend_alloca. Change control flow to avoid a goto.
Remove assert which is trivially always true.
2015-10-28 Joseph Myers <joseph@codesourcery.com>
[BZ #16068]

59
elf/dl-fini.c
View File

@ -16,7 +16,6 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <alloca.h>
#include <assert.h>
#include <string.h>
#include <ldsodefs.h>
@ -140,8 +139,6 @@ _dl_fini (void)
using `dlopen' there are possibly several other modules with its
dependencies to be taken into account. Therefore we have to start
determining the order of the modules once again from the beginning. */
struct link_map **maps = NULL;
size_t maps_size = 0;
/* We run the destructors of the main namespaces last. As for the
other namespaces, we pick run the destructors in them in reverse
@ -155,7 +152,6 @@ _dl_fini (void)
/* Protect against concurrent loads and unloads. */
__rtld_lock_lock_recursive (GL(dl_load_lock));
unsigned int nmaps = 0;
unsigned int nloaded = GL(dl_ns)[ns]._ns_nloaded;
/* No need to do anything for empty namespaces or those used for
auditing DSOs. */
@ -164,26 +160,12 @@ _dl_fini (void)
|| GL(dl_ns)[ns]._ns_loaded->l_auditing != do_audit
#endif
)
goto out;
/* XXX Could it be (in static binaries) that there is no object
loaded? */
assert (ns != LM_ID_BASE || nloaded > 0);
/* Now we can allocate an array to hold all the pointers and copy
the pointers in. */
if (maps_size < nloaded * sizeof (struct link_map *))
{
if (maps_size == 0)
{
maps_size = nloaded * sizeof (struct link_map *);
maps = (struct link_map **) alloca (maps_size);
}
__rtld_lock_unlock_recursive (GL(dl_load_lock));
else
maps = (struct link_map **)
extend_alloca (maps, maps_size,
nloaded * sizeof (struct link_map *));
}
{
/* Now we can allocate an array to hold all the pointers and
copy the pointers in. */
struct link_map *maps[nloaded];
unsigned int i;
struct link_map *l;
@ -198,31 +180,32 @@ _dl_fini (void)
l->l_idx = i;
++i;
/* Bump l_direct_opencount of all objects so that they are
not dlclose()ed from underneath us. */
/* Bump l_direct_opencount of all objects so that they
are not dlclose()ed from underneath us. */
++l->l_direct_opencount;
}
assert (ns != LM_ID_BASE || i == nloaded);
assert (ns == LM_ID_BASE || i == nloaded || i == nloaded - 1);
nmaps = i;
unsigned int nmaps = i;
/* Now we have to do the sorting. */
_dl_sort_fini (maps, nmaps, NULL, ns);
/* We do not rely on the linked list of loaded object anymore from
this point on. We have our own list here (maps). The various
members of this list cannot vanish since the open count is too
high and will be decremented in this loop. So we release the
lock so that some code which might be called from a destructor
can directly or indirectly access the lock. */
out:
/* We do not rely on the linked list of loaded object anymore
from this point on. We have our own list here (maps). The
various members of this list cannot vanish since the open
count is too high and will be decremented in this loop. So
we release the lock so that some code which might be called
from a destructor can directly or indirectly access the
lock. */
__rtld_lock_unlock_recursive (GL(dl_load_lock));
/* 'maps' now contains the objects in the right order. Now call the
destructors. We have to process this array from the front. */
/* 'maps' now contains the objects in the right order. Now
call the destructors. We have to process this array from
the front. */
for (i = 0; i < nmaps; ++i)
{
l = maps[i];
struct link_map *l = maps[i];
if (l->l_init_called)
{
@ -254,7 +237,8 @@ _dl_fini (void)
/* Next try the old-style destructor. */
if (l->l_info[DT_FINI] != NULL)
DL_CALL_DT_FINI(l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr);
DL_CALL_DT_FINI
(l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr);
}
#ifdef SHARED
@ -278,6 +262,7 @@ _dl_fini (void)
--l->l_direct_opencount;
}
}
}
#ifdef SHARED
if (! do_audit && GLRO(dl_naudit) > 0)