[PR19826] fix non-LE TLS in static programs

An earlier fix for TLS dropped early initialization of DTV entries for
modules using static TLS, leaving it for __tls_get_addr to set them
up.  That worked on platforms that require the GD access model to be
relaxed to LE in the main executable, but it caused a regression on
platforms that allow GD in the main executable, particularly in
statically-linked programs: they use a custom __tls_get_addr that does
not update the DTV, which fails when the DTV early initialization is
not performed.

In static programs, __libc_setup_tls performs the DTV initialization
for the main thread, but the DTV of other threads is set up in
_dl_allocate_tls_init, so that's the fix that matters.

Restoring the initialization in the remaining functions modified by
this patch was just for uniformity.  It's not clear that it is ever
needed: even on platforms that allow GD in the main executable, the
dynamically-linked version of __tls_get_addr would set up the DTV
entries, even for static TLS modules, while updating the DTV counter.

for  ChangeLog

	[BZ #19826]
	* elf/dl-tls.c (_dl_allocate_tls_init): Restore DTV early
	initialization of static TLS entries.
	* elf/dl-reloc.c (_dl_nothread_init_static_tls): Likewise.
	* nptl/allocatestack.c (init_one_static_tls): Likewise.

diff --git a/ChangeLog b/ChangeLog
index abd6995..0fe5350 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2016-09-21  Alexandre Oliva <aoliva@redhat.com>
+
+       [BZ #19826]
+       * elf/dl-tls.c (_dl_allocate_tls_init): Restore DTV early
+       initialization of static TLS entries.
+       * elf/dl-reloc.c (_dl_nothread_init_static_tls): Likewise.
+       * nptl/allocatestack.c (init_one_static_tls): Likewise.
+
 2016-09-22  Samuel Thibault  <samuel.thibault@ens-lyon.org>
 
        * hurd/hurdmalloc.c (malloc_fork_prepare): Rename to

diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
index 42bddc1..dcab666 100644 (file)
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -137,6 +137,12 @@ _dl_nothread_init_static_tls (struct link_map *map)
 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 #endif
 
+  /* Fill in the DTV slot so that a later LD/GD access will find it.  */
+  dtv_t *dtv = THREAD_DTV ();
+  assert (map->l_tls_modid <= dtv[-1].counter);
+  dtv[map->l_tls_modid].pointer.to_free = NULL;
+  dtv[map->l_tls_modid].pointer.val = dest;
+
   /* Initialize the memory.  */
   memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
          '\0', map->l_tls_blocksize - map->l_tls_initimage_size);

diff --git a/elf/dl-tls.c b/elf/dl-tls.c
index 17567ad..60f4c1d 100644 (file)
--- a/elf/dl-tls.c
+++ b/elf/dl-tls.c
@@ -538,6 +538,10 @@ _dl_allocate_tls_init (void *result)
 # 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;
+
          /* Copy the initialization image and clear the BSS part.  */
          memset (__mempcpy (dest, map->l_tls_initimage,
                             map->l_tls_initimage_size), '\0',

diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 60b34dc..3016a2e 100644 (file)
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -1207,9 +1207,12 @@ init_one_static_tls (struct pthread *curp, struct link_map *map)
 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 # endif
 
-  /* We cannot delay the initialization of the Static TLS area, since
-     it can be accessed with LE or IE, but since the DTV is only used
-     by GD and LD, we can delay its update to avoid a race.  */
+  /* Fill in the DTV slot so that a later LD/GD access will find it.  */
+  dtv_t *dtv = GET_DTV (TLS_TPADJ (curp));
+  dtv[map->l_tls_modid].pointer.to_free = NULL;
+  dtv[map->l_tls_modid].pointer.val = dest;
+
+  /* Initialize the memory.  */
   memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
          '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
 }