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GNU C Library master sources branch master updated. glibc-2.21-474-gc71c89e
- From: nsz at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 17 Jun 2015 12:17:28 -0000
- Subject: GNU C Library master sources branch master updated. glibc-2.21-474-gc71c89e
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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=c71c89e5c72baf43fd44d08dda8ab846eec5b1d6
commit c71c89e5c72baf43fd44d08dda8ab846eec5b1d6
Author: Szabolcs Nagy <nsz@port70.net>
Date: Wed Jun 17 12:44:53 2015 +0100
[AArch64] Fix cfi_adjust_cfa_offset usage in dl-tlsdesc.S
Some of the cfi annotations used incorrect sign.
* sysdeps/aarch64/dl-tlsdesc.S (_dl_tlsdesc_return_lazy): Fix
cfi_adjust_cfa_offset argument.
(_dl_tlsdesc_undefweak, _dl_tlsdesc_dynamic): Likewise.
(_dl_tlsdesc_resolve_rela, _dl_tlsdesc_resolve_hold): Likewise.
diff --git a/ChangeLog b/ChangeLog
index 1d4a376..aedec5a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
2015-06-17 Szabolcs Nagy <szabolcs.nagy@arm.com>
+ * sysdeps/aarch64/dl-tlsdesc.S (_dl_tlsdesc_return_lazy): Fix
+ cfi_adjust_cfa_offset argument.
+ (_dl_tlsdesc_undefweak, _dl_tlsdesc_dynamic): Likewise.
+ (_dl_tlsdesc_resolve_rela, _dl_tlsdesc_resolve_hold): Likewise.
+
[BZ #18034]
* sysdeps/aarch64/dl-tlsdesc.h (_dl_tlsdesc_return_lazy): Declare.
* sysdeps/aarch64/dl-tlsdesc.S (_dl_tlsdesc_return_lazy): Define.
diff --git a/sysdeps/aarch64/dl-tlsdesc.S b/sysdeps/aarch64/dl-tlsdesc.S
index c7adf79..64719eb 100644
--- a/sysdeps/aarch64/dl-tlsdesc.S
+++ b/sysdeps/aarch64/dl-tlsdesc.S
@@ -118,7 +118,7 @@ _dl_tlsdesc_return_lazy:
.align 2
_dl_tlsdesc_undefweak:
str x1, [sp, #-16]!
- cfi_adjust_cfa_offset(16)
+ cfi_adjust_cfa_offset (16)
/* The ldar here happens after the load from [x0] at the call site
(that is generated by the compiler as part of the TLS access ABI),
so it reads the same value (this function is the final value of
@@ -130,7 +130,7 @@ _dl_tlsdesc_undefweak:
mrs x1, tpidr_el0
sub x0, x0, x1
ldr x1, [sp], #16
- cfi_adjust_cfa_offset(16)
+ cfi_adjust_cfa_offset (-16)
RET
cfi_endproc
.size _dl_tlsdesc_undefweak, .-_dl_tlsdesc_undefweak
@@ -208,7 +208,7 @@ _dl_tlsdesc_dynamic:
ldp x3, x4, [sp, #32+16*1]
ldp x29, x30, [sp], #(32+16*NSAVEXREGPAIRS)
- cfi_adjust_cfa_offset (32+16*NSAVEXREGPAIRS)
+ cfi_adjust_cfa_offset (-32-16*NSAVEXREGPAIRS)
# undef NSAVEXREGPAIRS
RET
2:
@@ -297,7 +297,7 @@ _dl_tlsdesc_resolve_rela:
ldp x15, x16, [sp, #32+16*6]
ldp x17, x18, [sp, #32+16*7]
ldp x29, x30, [sp], #(32+16*NSAVEXREGPAIRS)
- cfi_adjust_cfa_offset (-32+16*NSAVEXREGPAIRS)
+ cfi_adjust_cfa_offset (-32-16*NSAVEXREGPAIRS)
ldp x2, x3, [sp], #16
cfi_adjust_cfa_offset (-16)
RET
@@ -359,7 +359,7 @@ _dl_tlsdesc_resolve_hold:
ldp x15, x16, [sp, #32+16*7]
ldp x17, x18, [sp, #32+16*8]
ldp x29, x30, [sp], #(32+16*NSAVEXREGPAIRS)
- cfi_adjust_cfa_offset (-32+16*NSAVEXREGPAIRS)
+ cfi_adjust_cfa_offset (-32-16*NSAVEXREGPAIRS)
RET
cfi_endproc
.size _dl_tlsdesc_resolve_hold, .-_dl_tlsdesc_resolve_hold
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=08325735c2efb0257b8c07ac0ff91e44c27ecbf8
commit 08325735c2efb0257b8c07ac0ff91e44c27ecbf8
Author: Szabolcs Nagy <nsz@port70.net>
Date: Wed Jun 17 12:37:49 2015 +0100
[BZ 18034][AArch64] Lazy TLSDESC relocation data race fix
Lazy TLSDESC initialization needs to be synchronized with concurrent TLS
accesses. The TLS descriptor contains a function pointer (entry) and an
argument that is accessed from the entry function. With lazy initialization
the first call to the entry function updates the entry and the argument to
their final value. A final entry function must make sure that it accesses an
initialized argument, this needs synchronization on systems with weak memory
ordering otherwise the writes of the first call can be observed out of order.
There are at least two issues with the current code:
tlsdesc.c (i386, x86_64, arm, aarch64) uses volatile memory accesses on the
write side (in the initial entry function) instead of C11 atomics.
And on systems with weak memory ordering (arm, aarch64) the read side
synchronization is missing from the final entry functions (dl-tlsdesc.S).
This patch only deals with aarch64.
* Write side:
Volatile accesses were replaced with C11 relaxed atomics, and a release
store was used for the initialization of entry so the read side can
synchronize with it.
* Read side:
TLS access generated by the compiler and an entry function code is roughly
ldr x1, [x0] // load the entry
blr x1 // call it
entryfunc:
ldr x0, [x0,#8] // load the arg
ret
Various alternatives were considered to force the ordering in the entry
function between the two loads:
(1) barrier
entryfunc:
dmb ishld
ldr x0, [x0,#8]
(2) address dependency (if the address of the second load depends on the
result of the first one the ordering is guaranteed):
entryfunc:
ldr x1,[x0]
and x1,x1,#8
orr x1,x1,#8
ldr x0,[x0,x1]
(3) load-acquire (ARMv8 instruction that is ordered before subsequent
loads and stores)
entryfunc:
ldar xzr,[x0]
ldr x0,[x0,#8]
Option (1) is the simplest but slowest (note: this runs at every TLS
access), options (2) and (3) do one extra load from [x0] (same address
loads are ordered so it happens-after the load on the call site),
option (2) clobbers x1 which is problematic because existing gcc does
not expect that, so approach (3) was chosen.
A new _dl_tlsdesc_return_lazy entry function was introduced for lazily
relocated static TLS, so non-lazy static TLS can avoid the synchronization
cost.
[BZ #18034]
* sysdeps/aarch64/dl-tlsdesc.h (_dl_tlsdesc_return_lazy): Declare.
* sysdeps/aarch64/dl-tlsdesc.S (_dl_tlsdesc_return_lazy): Define.
(_dl_tlsdesc_undefweak): Guarantee TLSDESC entry and argument load-load
ordering using ldar.
(_dl_tlsdesc_dynamic): Likewise.
(_dl_tlsdesc_return_lazy): Likewise.
* sysdeps/aarch64/tlsdesc.c (_dl_tlsdesc_resolve_rela_fixup): Use
relaxed atomics instead of volatile and synchronize with release store.
(_dl_tlsdesc_resolve_hold_fixup): Use relaxed atomics instead of
volatile.
* elf/tlsdeschtab.h (_dl_tlsdesc_resolve_early_return_p): Likewise.
diff --git a/ChangeLog b/ChangeLog
index 5e93d9e..1d4a376 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2015-06-17 Szabolcs Nagy <szabolcs.nagy@arm.com>
+
+ [BZ #18034]
+ * sysdeps/aarch64/dl-tlsdesc.h (_dl_tlsdesc_return_lazy): Declare.
+ * sysdeps/aarch64/dl-tlsdesc.S (_dl_tlsdesc_return_lazy): Define.
+ (_dl_tlsdesc_undefweak): Guarantee TLSDESC entry and argument load-load
+ ordering using ldar.
+ (_dl_tlsdesc_dynamic): Likewise.
+ (_dl_tlsdesc_return_lazy): Likewise.
+ * sysdeps/aarch64/tlsdesc.c (_dl_tlsdesc_resolve_rela_fixup): Use
+ relaxed atomics instead of volatile and synchronize with release store.
+ (_dl_tlsdesc_resolve_hold_fixup): Use relaxed atomics instead of
+ volatile.
+ * elf/tlsdeschtab.h (_dl_tlsdesc_resolve_early_return_p): Likewise.
+
2015-06-15 Andrew Senkevich <andrew.senkevich@intel.com>
* sysdeps/unix/sysv/linux/x86_64/libmvec.abilist: New symbols added.
diff --git a/NEWS b/NEWS
index 33cba7b..b215276 100644
--- a/NEWS
+++ b/NEWS
@@ -15,13 +15,13 @@ Version 2.22
17581, 17588, 17596, 17620, 17621, 17628, 17631, 17692, 17711, 17715,
17776, 17779, 17792, 17836, 17912, 17916, 17930, 17932, 17944, 17949,
17964, 17965, 17967, 17969, 17978, 17987, 17991, 17996, 17998, 17999,
- 18007, 18019, 18020, 18029, 18030, 18032, 18036, 18038, 18039, 18042,
- 18043, 18046, 18047, 18049, 18068, 18080, 18093, 18100, 18104, 18110,
- 18111, 18116, 18125, 18128, 18138, 18185, 18196, 18197, 18206, 18210,
- 18211, 18217, 18220, 18221, 18234, 18244, 18247, 18287, 18319, 18324,
- 18333, 18346, 18397, 18409, 18410, 18412, 18418, 18422, 18434, 18444,
- 18468, 18469, 18470, 18479, 18483, 18495, 18496, 18497, 18498, 18507,
- 18512, 18519, 18520, 18522, 18527, 18528, 18529, 18530.
+ 18007, 18019, 18020, 18029, 18030, 18032, 18034, 18036, 18038, 18039,
+ 18042, 18043, 18046, 18047, 18049, 18068, 18080, 18093, 18100, 18104,
+ 18110, 18111, 18116, 18125, 18128, 18138, 18185, 18196, 18197, 18206,
+ 18210, 18211, 18217, 18220, 18221, 18234, 18244, 18247, 18287, 18319,
+ 18324, 18333, 18346, 18397, 18409, 18410, 18412, 18418, 18422, 18434,
+ 18444, 18468, 18469, 18470, 18479, 18483, 18495, 18496, 18497, 18498,
+ 18507, 18512, 18519, 18520, 18522, 18527, 18528, 18529, 18530.
* Cache information can be queried via sysconf() function on s390 e.g. with
_SC_LEVEL1_ICACHE_SIZE as argument.
diff --git a/elf/tlsdeschtab.h b/elf/tlsdeschtab.h
index d13b4e5..fb0eb88 100644
--- a/elf/tlsdeschtab.h
+++ b/elf/tlsdeschtab.h
@@ -20,6 +20,8 @@
#ifndef TLSDESCHTAB_H
# define TLSDESCHTAB_H 1
+#include <atomic.h>
+
# ifdef SHARED
# include <inline-hashtab.h>
@@ -138,17 +140,17 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
static int
_dl_tlsdesc_resolve_early_return_p (struct tlsdesc volatile *td, void *caller)
{
- if (caller != td->entry)
+ if (caller != atomic_load_relaxed (&td->entry))
return 1;
__rtld_lock_lock_recursive (GL(dl_load_lock));
- if (caller != td->entry)
+ if (caller != atomic_load_relaxed (&td->entry))
{
__rtld_lock_unlock_recursive (GL(dl_load_lock));
return 1;
}
- td->entry = _dl_tlsdesc_resolve_hold;
+ atomic_store_relaxed (&td->entry, _dl_tlsdesc_resolve_hold);
return 0;
}
diff --git a/sysdeps/aarch64/dl-tlsdesc.S b/sysdeps/aarch64/dl-tlsdesc.S
index be9b9b3..c7adf79 100644
--- a/sysdeps/aarch64/dl-tlsdesc.S
+++ b/sysdeps/aarch64/dl-tlsdesc.S
@@ -79,6 +79,29 @@ _dl_tlsdesc_return:
cfi_endproc
.size _dl_tlsdesc_return, .-_dl_tlsdesc_return
+ /* Same as _dl_tlsdesc_return but with synchronization for
+ lazy relocation.
+ Prototype:
+ _dl_tlsdesc_return_lazy (tlsdesc *) ;
+ */
+ .hidden _dl_tlsdesc_return_lazy
+ .global _dl_tlsdesc_return_lazy
+ .type _dl_tlsdesc_return_lazy,%function
+ cfi_startproc
+ .align 2
+_dl_tlsdesc_return_lazy:
+ /* The ldar here happens after the load from [x0] at the call site
+ (that is generated by the compiler as part of the TLS access ABI),
+ so it reads the same value (this function is the final value of
+ td->entry) and thus it synchronizes with the release store to
+ td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load
+ from [x0,#8] here happens after the initialization of td->arg. */
+ ldar xzr, [x0]
+ ldr x0, [x0, #8]
+ RET
+ cfi_endproc
+ .size _dl_tlsdesc_return_lazy, .-_dl_tlsdesc_return_lazy
+
/* Handler for undefined weak TLS symbols.
Prototype:
_dl_tlsdesc_undefweak (tlsdesc *);
@@ -96,6 +119,13 @@ _dl_tlsdesc_return:
_dl_tlsdesc_undefweak:
str x1, [sp, #-16]!
cfi_adjust_cfa_offset(16)
+ /* The ldar here happens after the load from [x0] at the call site
+ (that is generated by the compiler as part of the TLS access ABI),
+ so it reads the same value (this function is the final value of
+ td->entry) and thus it synchronizes with the release store to
+ td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load
+ from [x0,#8] here happens after the initialization of td->arg. */
+ ldar xzr, [x0]
ldr x0, [x0, #8]
mrs x1, tpidr_el0
sub x0, x0, x1
@@ -152,6 +182,13 @@ _dl_tlsdesc_dynamic:
stp x3, x4, [sp, #32+16*1]
mrs x4, tpidr_el0
+ /* The ldar here happens after the load from [x0] at the call site
+ (that is generated by the compiler as part of the TLS access ABI),
+ so it reads the same value (this function is the final value of
+ td->entry) and thus it synchronizes with the release store to
+ td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load
+ from [x0,#8] here happens after the initialization of td->arg. */
+ ldar xzr, [x0]
ldr x1, [x0,#8]
ldr x0, [x4]
ldr x3, [x1,#16]
diff --git a/sysdeps/aarch64/dl-tlsdesc.h b/sysdeps/aarch64/dl-tlsdesc.h
index 7a1285e..e6c0078 100644
--- a/sysdeps/aarch64/dl-tlsdesc.h
+++ b/sysdeps/aarch64/dl-tlsdesc.h
@@ -46,6 +46,9 @@ extern ptrdiff_t attribute_hidden
_dl_tlsdesc_return (struct tlsdesc *);
extern ptrdiff_t attribute_hidden
+_dl_tlsdesc_return_lazy (struct tlsdesc *);
+
+extern ptrdiff_t attribute_hidden
_dl_tlsdesc_undefweak (struct tlsdesc *);
extern ptrdiff_t attribute_hidden
diff --git a/sysdeps/aarch64/tlsdesc.c b/sysdeps/aarch64/tlsdesc.c
index 4821f8c..9f3ff9b 100644
--- a/sysdeps/aarch64/tlsdesc.c
+++ b/sysdeps/aarch64/tlsdesc.c
@@ -25,6 +25,7 @@
#include <dl-tlsdesc.h>
#include <dl-unmap-segments.h>
#include <tlsdeschtab.h>
+#include <atomic.h>
/* The following functions take an entry_check_offset argument. It's
computed by the caller as an offset between its entry point and the
@@ -39,11 +40,15 @@
void
attribute_hidden
-_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,
- struct link_map *l)
+_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc *td, struct link_map *l)
{
- const ElfW(Rela) *reloc = td->arg;
+ const ElfW(Rela) *reloc = atomic_load_relaxed (&td->arg);
+ /* After GL(dl_load_lock) is grabbed only one caller can see td->entry in
+ initial state in _dl_tlsdesc_resolve_early_return_p, other concurrent
+ callers will return and retry calling td->entry. The updated td->entry
+ synchronizes with the single writer so all read accesses here can use
+ relaxed order. */
if (_dl_tlsdesc_resolve_early_return_p
(td, (void*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_PLT)]) + l->l_addr)))
return;
@@ -86,8 +91,10 @@ _dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,
if (!sym)
{
- td->arg = (void*) reloc->r_addend;
- td->entry = _dl_tlsdesc_undefweak;
+ atomic_store_relaxed (&td->arg, (void *) reloc->r_addend);
+ /* This release store synchronizes with the ldar acquire load
+ instruction in _dl_tlsdesc_undefweak. */
+ atomic_store_release (&td->entry, _dl_tlsdesc_undefweak);
}
else
{
@@ -96,16 +103,22 @@ _dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,
# else
if (!TRY_STATIC_TLS (l, result))
{
- td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value
+ void *p = _dl_make_tlsdesc_dynamic (result, sym->st_value
+ reloc->r_addend);
- td->entry = _dl_tlsdesc_dynamic;
+ atomic_store_relaxed (&td->arg, p);
+ /* This release store synchronizes with the ldar acquire load
+ instruction in _dl_tlsdesc_dynamic. */
+ atomic_store_release (&td->entry, _dl_tlsdesc_dynamic);
}
else
# endif
{
- td->arg = (void*) (sym->st_value + result->l_tls_offset
+ void *p = (void*) (sym->st_value + result->l_tls_offset
+ reloc->r_addend);
- td->entry = _dl_tlsdesc_return;
+ atomic_store_relaxed (&td->arg, p);
+ /* This release store synchronizes with the ldar acquire load
+ instruction in _dl_tlsdesc_return_lazy. */
+ atomic_store_release (&td->entry, _dl_tlsdesc_return_lazy);
}
}
@@ -120,11 +133,10 @@ _dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,
void
attribute_hidden
-_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc volatile *td,
- void *caller)
+_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc *td, void *caller)
{
/* Maybe we're lucky and can return early. */
- if (caller != td->entry)
+ if (caller != atomic_load_relaxed (&td->entry))
return;
/* Locking here will stop execution until the running resolver runs
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 20 +++++++++++++++++
NEWS | 14 ++++++------
elf/tlsdeschtab.h | 8 ++++--
sysdeps/aarch64/dl-tlsdesc.S | 47 +++++++++++++++++++++++++++++++++++++----
sysdeps/aarch64/dl-tlsdesc.h | 3 ++
sysdeps/aarch64/tlsdesc.c | 36 +++++++++++++++++++++----------
6 files changed, 101 insertions(+), 27 deletions(-)
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