+2018-11-30 Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
+
+ [BZ #23690]
+ * elf/dl-runtime.c (_dl_profile_fixup): Guarantee memory
+ modification order when accessing reloc_result->addr.
+ * include/link.h (reloc_result): Add field init.
+ * nptl/Makefile (tests): Add tst-audit-threads.
+ (modules-names): Add tst-audit-threads-mod1 and
+ tst-audit-threads-mod2.
+ Add rules to build tst-audit-threads.
+ * nptl/tst-audit-threads-mod1.c: New file.
+ * nptl/tst-audit-threads-mod2.c: Likewise.
+ * nptl/tst-audit-threads.c: Likewise.
+ * nptl/tst-audit-threads.h: Likewise.
+
2018-11-30 Joseph Myers <joseph@codesourcery.com>
* scripts/gen-as-const.py: New file.
/* This is the address in the array where we store the result of previous
relocations. */
struct reloc_result *reloc_result = &l->l_reloc_result[reloc_index];
- DL_FIXUP_VALUE_TYPE *resultp = &reloc_result->addr;
- DL_FIXUP_VALUE_TYPE value = *resultp;
- if (DL_FIXUP_VALUE_CODE_ADDR (value) == 0)
+ /* CONCURRENCY NOTES:
+
+ Multiple threads may be calling the same PLT sequence and with
+ LD_AUDIT enabled they will be calling into _dl_profile_fixup to
+ update the reloc_result with the result of the lazy resolution.
+ The reloc_result guard variable is reloc_init, and we use
+ acquire/release loads and store to it to ensure that the results of
+ the structure are consistent with the loaded value of the guard.
+ This does not fix all of the data races that occur when two or more
+ threads read reloc_result->reloc_init with a value of zero and read
+ and write to that reloc_result concurrently. The expectation is
+ generally that while this is a data race it works because the
+ threads write the same values. Until the data races are fixed
+ there is a potential for problems to arise from these data races.
+ The reloc result updates should happen in parallel but there should
+ be an atomic RMW which does the final update to the real result
+ entry (see bug 23790).
+
+ The following code uses reloc_result->init set to 0 to indicate if it is
+ the first time this object is being relocated, otherwise 1 which
+ indicates the object has already been relocated.
+
+ Reading/Writing from/to reloc_result->reloc_init must not happen
+ before previous writes to reloc_result complete as they could
+ end-up with an incomplete struct. */
+ DL_FIXUP_VALUE_TYPE value;
+ unsigned int init = atomic_load_acquire (&reloc_result->init);
+
+ if (init == 0)
{
/* This is the first time we have to relocate this object. */
const ElfW(Sym) *const symtab
/* Store the result for later runs. */
if (__glibc_likely (! GLRO(dl_bind_not)))
- *resultp = value;
+ {
+ reloc_result->addr = value;
+ /* Guarantee all previous writes complete before
+ init is updated. See CONCURRENCY NOTES earlier */
+ atomic_store_release (&reloc_result->init, 1);
+ }
+ init = 1;
}
+ else
+ value = reloc_result->addr;
/* By default we do not call the pltexit function. */
long int framesize = -1;
+
#ifdef SHARED
/* Auditing checkpoint: report the PLT entering and allow the
auditors to change the value. */
- if (DL_FIXUP_VALUE_CODE_ADDR (value) != 0 && GLRO(dl_naudit) > 0
+ if (GLRO(dl_naudit) > 0
/* Don't do anything if no auditor wants to intercept this call. */
&& (reloc_result->enterexit & LA_SYMB_NOPLTENTER) == 0)
{
+ /* Sanity check: DL_FIXUP_VALUE_CODE_ADDR (value) should have been
+ initialized earlier in this function or in another thread. */
+ assert (DL_FIXUP_VALUE_CODE_ADDR (value) != 0);
ElfW(Sym) *defsym = ((ElfW(Sym) *) D_PTR (reloc_result->bound,
l_info[DT_SYMTAB])
+ reloc_result->boundndx);
unsigned int boundndx;
uint32_t enterexit;
unsigned int flags;
+ /* CONCURRENCY NOTE: This is used to guard the concurrent initialization
+ of the relocation result across multiple threads. See the more
+ detailed notes in elf/dl-runtime.c. */
+ unsigned int init;
} *l_reloc_result;
/* Pointer to the version information if available. */
tst-cleanupx0 tst-cleanupx1 tst-cleanupx2 tst-cleanupx3 tst-cleanupx4 \
tst-oncex3 tst-oncex4
ifeq ($(build-shared),yes)
-tests += tst-atfork2 tst-tls4 tst-_res1 tst-fini1 tst-compat-forwarder
+tests += tst-atfork2 tst-tls4 tst-_res1 tst-fini1 tst-compat-forwarder \
+ tst-audit-threads
tests-internal += tst-tls3 tst-tls3-malloc tst-tls5 tst-stackguard1
tests-nolibpthread += tst-fini1
ifeq ($(have-z-execstack),yes)
tst-tls5mod tst-tls5moda tst-tls5modb tst-tls5modc \
tst-tls5modd tst-tls5mode tst-tls5modf tst-stack4mod \
tst-_res1mod1 tst-_res1mod2 tst-execstack-mod tst-fini1mod \
- tst-join7mod tst-compat-forwarder-mod
+ tst-join7mod tst-compat-forwarder-mod tst-audit-threads-mod1 \
+ tst-audit-threads-mod2
extra-test-objs += $(addsuffix .os,$(strip $(modules-names))) \
tst-cleanup4aux.o tst-cleanupx4aux.o
test-extras += tst-cleanup4aux tst-cleanupx4aux
tst-mutex10-ENV = GLIBC_TUNABLES=glibc.elision.enable=1
+# Protect against a build using -Wl,-z,now.
+LDFLAGS-tst-audit-threads-mod1.so = -Wl,-z,lazy
+LDFLAGS-tst-audit-threads-mod2.so = -Wl,-z,lazy
+LDFLAGS-tst-audit-threads = -Wl,-z,lazy
+$(objpfx)tst-audit-threads: $(objpfx)tst-audit-threads-mod2.so
+$(objpfx)tst-audit-threads.out: $(objpfx)tst-audit-threads-mod1.so
+tst-audit-threads-ENV = LD_AUDIT=$(objpfx)tst-audit-threads-mod1.so
+
# The tests here better do not run in parallel
ifneq ($(filter %tests,$(MAKECMDGOALS)),)
.NOTPARALLEL:
--- /dev/null
+/* Dummy audit library for test-audit-threads.
+
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <elf.h>
+#include <link.h>
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+
+/* We must use a dummy LD_AUDIT module to force the dynamic loader to
+ *not* update the real PLT, and instead use a cached value for the
+ lazy resolution result. It is the update of that cached value that
+ we are testing for correctness by doing this. */
+
+/* Library to be audited. */
+#define LIB "tst-audit-threads-mod2.so"
+/* CALLNUM is the number of retNum functions. */
+#define CALLNUM 7999
+
+#define CONCATX(a, b) __CONCAT (a, b)
+
+static int previous = 0;
+
+unsigned int
+la_version (unsigned int ver)
+{
+ return 1;
+}
+
+unsigned int
+la_objopen (struct link_map *map, Lmid_t lmid, uintptr_t *cookie)
+{
+ return LA_FLG_BINDTO | LA_FLG_BINDFROM;
+}
+
+uintptr_t
+CONCATX(la_symbind, __ELF_NATIVE_CLASS) (ElfW(Sym) *sym,
+ unsigned int ndx,
+ uintptr_t *refcook,
+ uintptr_t *defcook,
+ unsigned int *flags,
+ const char *symname)
+{
+ const char * retnum = "retNum";
+ char * num = strstr (symname, retnum);
+ int n;
+ /* Validate if the symbols are getting called in the correct order.
+ This code is here to verify binutils does not optimize out the PLT
+ entries that require the symbol binding. */
+ if (num != NULL)
+ {
+ n = atoi (num);
+ assert (n >= previous);
+ assert (n <= CALLNUM);
+ previous = n;
+ }
+ return sym->st_value;
+}
--- /dev/null
+/* Shared object with a huge number of functions for test-audit-threads.
+
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* Define all the retNumN functions in a library. */
+#define definenum
+#include "tst-audit-threads.h"
--- /dev/null
+/* Test multi-threading using LD_AUDIT.
+
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* This test uses a dummy LD_AUDIT library (test-audit-threads-mod1) and a
+ library with a huge number of functions in order to validate lazy symbol
+ binding with an audit library. We use one thread per CPU to test that
+ concurrent lazy resolution does not have any defects which would cause
+ the process to fail. We use an LD_AUDIT library to force the testing of
+ the relocation resolution caching code in the dynamic loader i.e.
+ _dl_runtime_profile and _dl_profile_fixup. */
+
+#include <support/xthread.h>
+#include <strings.h>
+#include <stdlib.h>
+#include <sys/sysinfo.h>
+
+static int do_test (void);
+
+/* This test usually takes less than 3s to run. However, there are cases that
+ take up to 30s. */
+#define TIMEOUT 60
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
+
+/* Declare the functions we are going to call. */
+#define externnum
+#include "tst-audit-threads.h"
+#undef externnum
+
+int num_threads;
+pthread_barrier_t barrier;
+
+void
+sync_all (int num)
+{
+ pthread_barrier_wait (&barrier);
+}
+
+void
+call_all_ret_nums (void)
+{
+ /* Call each function one at a time from all threads. */
+#define callnum
+#include "tst-audit-threads.h"
+#undef callnum
+}
+
+void *
+thread_main (void *unused)
+{
+ call_all_ret_nums ();
+ return NULL;
+}
+
+#define STR2(X) #X
+#define STR(X) STR2(X)
+
+static int
+do_test (void)
+{
+ int i;
+ pthread_t *threads;
+
+ num_threads = get_nprocs ();
+ if (num_threads <= 1)
+ num_threads = 2;
+
+ /* Used to synchronize all the threads after calling each retNumN. */
+ xpthread_barrier_init (&barrier, NULL, num_threads);
+
+ threads = (pthread_t *) xcalloc (num_threads, sizeof(pthread_t));
+ for (i = 0; i < num_threads; i++)
+ threads[i] = xpthread_create(NULL, thread_main, NULL);
+
+ for (i = 0; i < num_threads; i++)
+ xpthread_join(threads[i]);
+
+ free (threads);
+
+ return 0;
+}
--- /dev/null
+/* Helper header for test-audit-threads.
+
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* We use this helper to create a large number of functions, all of
+ which will be resolved lazily and thus have their PLT updated.
+ This is done to provide enough functions that we can statistically
+ observe a thread vs. PLT resolution failure if one exists. */
+
+#define CONCAT(a, b) a ## b
+#define NUM(x, y) CONCAT (x, y)
+
+#define FUNC10(x) \
+ FUNC (NUM (x, 0)); \
+ FUNC (NUM (x, 1)); \
+ FUNC (NUM (x, 2)); \
+ FUNC (NUM (x, 3)); \
+ FUNC (NUM (x, 4)); \
+ FUNC (NUM (x, 5)); \
+ FUNC (NUM (x, 6)); \
+ FUNC (NUM (x, 7)); \
+ FUNC (NUM (x, 8)); \
+ FUNC (NUM (x, 9))
+
+#define FUNC100(x) \
+ FUNC10 (NUM (x, 0)); \
+ FUNC10 (NUM (x, 1)); \
+ FUNC10 (NUM (x, 2)); \
+ FUNC10 (NUM (x, 3)); \
+ FUNC10 (NUM (x, 4)); \
+ FUNC10 (NUM (x, 5)); \
+ FUNC10 (NUM (x, 6)); \
+ FUNC10 (NUM (x, 7)); \
+ FUNC10 (NUM (x, 8)); \
+ FUNC10 (NUM (x, 9))
+
+#define FUNC1000(x) \
+ FUNC100 (NUM (x, 0)); \
+ FUNC100 (NUM (x, 1)); \
+ FUNC100 (NUM (x, 2)); \
+ FUNC100 (NUM (x, 3)); \
+ FUNC100 (NUM (x, 4)); \
+ FUNC100 (NUM (x, 5)); \
+ FUNC100 (NUM (x, 6)); \
+ FUNC100 (NUM (x, 7)); \
+ FUNC100 (NUM (x, 8)); \
+ FUNC100 (NUM (x, 9))
+
+#define FUNC7000() \
+ FUNC1000 (1); \
+ FUNC1000 (2); \
+ FUNC1000 (3); \
+ FUNC1000 (4); \
+ FUNC1000 (5); \
+ FUNC1000 (6); \
+ FUNC1000 (7);
+
+#ifdef FUNC
+# undef FUNC
+#endif
+
+#ifdef externnum
+# define FUNC(x) extern int CONCAT (retNum, x) (void)
+#endif
+
+#ifdef definenum
+# define FUNC(x) int CONCAT (retNum, x) (void) { return x; }
+#endif
+
+#ifdef callnum
+# define FUNC(x) CONCAT (retNum, x) (); sync_all (x)
+#endif
+
+/* A value of 7000 functions is chosen as an arbitrarily large
+ number of functions that will allow us enough attempts to
+ verify lazy resolution operation. */
+FUNC7000 ();