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Bug 20915: Do not initialize DTV of other threads.

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In _dl_nothread_init_static_tls() and init_one_static_tls() we must not
touch the DTV of other threads since we do not have ownership of them.
The DTV need not be initialized at this point anyway since only LD/GD
accesses will use them. If LD/GD accesses occur they will take care to
initialize their own thread's DTV.

Concurrency comments were removed from the patch since they need to be
reworked along with a full description of DTV ownership and when it is
or is not safe to modify these structures.

Alexandre Oliva's original patch and discussion:
https://sourceware.org/ml/libc-alpha/2016-09/msg00512.html
This commit is contained in:
Alexandre Oliva 2017-02-03 20:35:16 -05:00 committed by Carlos O'Donell
parent 33d7e138ca
commit d675eaf7d9
3 changed files with 9 additions and 11 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2017-02-03 Alexandre Oliva <aoliva@redhat.com>
Florian Weimer <fweimer@redhat.com>
Carlos O'Donell <carlos@redhat.com>
[BZ #20915]
* elf/dl-reloc.c (_dl_nothread_init_static_tls):
Do not initialize DTV.
* nptl/allocatestack.c (init_one_static_tls): Likewise.
2017-02-03 David S. Miller <davem@davemloft.net>
* sysdeps/sparc/sparc64/fpu/multiarch/s_fmax-vis3.S: Remove file.

6
elf/dl-reloc.c
View File

@ -137,12 +137,6 @@ _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);

5
nptl/allocatestack.c
View File

@ -1191,11 +1191,6 @@ 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
/* 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);