Added $(objpfx)tst-audit19a: $(libdl) to elf/Makefile since
we still need $(libdl) in RHEL8.
commit 063f9ba220f434c7f30dd65c4cff17c0c458a7cf
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Wed Jun 30 10:24:09 2021 -0300
elf: Avoid unnecessary slowdown from profiling with audit (BZ#15533)
The rtld-audit interfaces introduces a slowdown due to enabling
profiling instrumentation (as if LD_AUDIT implied LD_PROFILE).
However, instrumenting is only necessary if one of audit libraries
provides PLT callbacks (la_pltenter or la_pltexit symbols). Otherwise,
the slowdown can be avoided.
The following patch adjusts the logic that enables profiling to iterate
over all audit modules and check if any of those provides a PLT hook.
To keep la_symbind to work even without PLT callbacks, _dl_fixup now
calls the audit callback if the modules implements it.
Co-authored-by: Alexander Monakov <amonakov@ispras.ru>
Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Conflicts:
elf/Makefile
diff --git a/elf/Makefile b/elf/Makefile
index 08a32a712a34f2cc..0cc03ffe2984ee50 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -221,12 +221,14 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
tst-dlmopen-gethostbyname \
tst-audit17 \
tst-audit18 \
+ tst-audit19b \
# reldep9
tests-internal += loadtest unload unload2 circleload1 \
neededtest neededtest2 neededtest3 neededtest4 \
tst-tls3 tst-tls6 tst-tls7 tst-tls8 tst-dlmopen2 \
tst-ptrguard1 tst-stackguard1 tst-libc_dlvsym \
- tst-create_format1 tst-tls-surplus tst-dl-hwcaps_split
+ tst-create_format1 tst-tls-surplus tst-dl-hwcaps_split \
+ tst-audit19a
tests-container += tst-pldd tst-preload-pthread-libc
ifeq ($(build-hardcoded-path-in-tests),yes)
tests += tst-dlopen-aout
@@ -358,6 +360,9 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
tst-dlmopen-gethostbyname-mod \
tst-auditmod18 \
tst-audit18mod \
+ tst-auditmod19a \
+ tst-auditmod19b \
+ tst-audit19bmod \
# Most modules build with _ISOMAC defined, but those filtered out
# depend on internal headers.
@@ -1548,6 +1553,14 @@ $(objpfx)tst-audit18.out: $(objpfx)tst-auditmod18.so \
$(objpfx)tst-audit18mod.so
tst-audit18-ARGS = -- $(host-test-program-cmd)
+$(objpfx)tst-audit19a: $(libdl)
+$(objpfx)tst-audit19a.out: $(objpfx)tst-auditmod19a.so
+tst-audit19a-ENV = LD_AUDIT=$(objpfx)tst-auditmod19a.so
+
+$(objpfx)tst-audit19b.out: $(objpfx)tst-auditmod19b.so
+$(objpfx)tst-audit19b: $(objpfx)tst-audit19bmod.so
+tst-audit19b-ARGS = -- $(host-test-program-cmd)
+
# tst-sonamemove links against an older implementation of the library.
LDFLAGS-tst-sonamemove-linkmod1.so = \
-Wl,--version-script=tst-sonamemove-linkmod1.map \
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
index 19de5de067a5ef07..7a84b1fa8c3a7fdd 100644
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -178,12 +178,28 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
int skip_ifunc = reloc_mode & __RTLD_NOIFUNC;
#ifdef SHARED
+ bool consider_symbind = false;
/* If we are auditing, install the same handlers we need for profiling. */
if ((reloc_mode & __RTLD_AUDIT) == 0)
- consider_profiling |= GLRO(dl_audit) != NULL;
+ {
+ struct audit_ifaces *afct = GLRO(dl_audit);
+ for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
+ {
+ /* Profiling is needed only if PLT hooks are provided. */
+ if (afct->ARCH_LA_PLTENTER != NULL
+ || afct->ARCH_LA_PLTEXIT != NULL)
+ consider_profiling = 1;
+ if (afct->symbind != NULL)
+ consider_symbind = true;
+
+ afct = afct->next;
+ }
+ }
#elif defined PROF
/* Never use dynamic linker profiling for gprof profiling code. */
# define consider_profiling 0
+#else
+# define consider_symbind 0
#endif
if (l->l_relocated)
@@ -278,7 +294,7 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
ELF_DYNAMIC_RELOCATE (l, scope, lazy, consider_profiling, skip_ifunc);
#ifndef PROF
- if (__glibc_unlikely (consider_profiling)
+ if ((consider_profiling || consider_symbind)
&& l->l_info[DT_PLTRELSZ] != NULL)
{
/* Allocate the array which will contain the already found
diff --git a/elf/dl-runtime.c b/elf/dl-runtime.c
index ec0b2164825fa538..71ec65264ff780fb 100644
--- a/elf/dl-runtime.c
+++ b/elf/dl-runtime.c
@@ -123,6 +123,37 @@ _dl_fixup (
&& __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0))
value = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (value));
+#ifdef SHARED
+ /* Auditing checkpoint: we have a new binding. Provide the auditing
+ libraries the possibility to change the value and tell us whether further
+ auditing is wanted.
+ The l_reloc_result is only allocated if there is an audit module which
+ provides a la_symbind. */
+ if (l->l_reloc_result != NULL)
+ {
+ /* 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 (pltgot, reloc_arg, sizeof (PLTREL))];
+ unsigned int init = atomic_load_acquire (&reloc_result->init);
+ if (init == 0)
+ {
+ _dl_audit_symbind (l, reloc_result, sym, &value, result);
+
+ /* Store the result for later runs. */
+ if (__glibc_likely (! GLRO(dl_bind_not)))
+ {
+ reloc_result->addr = value;
+ /* Guarantee all previous writes complete before init is
+ updated. See CONCURRENCY NOTES below. */
+ atomic_store_release (&reloc_result->init, 1);
+ }
+ }
+ else
+ value = reloc_result->addr;
+ }
+#endif
+
/* Finally, fix up the plt itself. */
if (__glibc_unlikely (GLRO(dl_bind_not)))
return value;
diff --git a/elf/rtld.c b/elf/rtld.c
index 767acd122262b824..2994578ba3a5f911 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1027,13 +1027,7 @@ ERROR: audit interface '%s' requires version %d (maximum supported version %d);
"la_objsearch\0"
"la_objopen\0"
"la_preinit\0"
-#if __ELF_NATIVE_CLASS == 32
- "la_symbind32\0"
-#elif __ELF_NATIVE_CLASS == 64
- "la_symbind64\0"
-#else
-# error "__ELF_NATIVE_CLASS must be defined"
-#endif
+ LA_SYMBIND "\0"
#define STRING(s) __STRING (s)
"la_" STRING (ARCH_LA_PLTENTER) "\0"
"la_" STRING (ARCH_LA_PLTEXIT) "\0"
diff --git a/elf/tst-audit19a.c b/elf/tst-audit19a.c
new file mode 100644
index 0000000000000000..035cde9351c2711b
--- /dev/null
+++ b/elf/tst-audit19a.c
@@ -0,0 +1,38 @@
+/* Check if DT_AUDIT a module without la_plt{enter,exit} symbols does not incur
+ in profiling (BZ#15533).
+ Copyright (C) 2021 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
+ <https://www.gnu.org/licenses/>. */
+
+#include <link.h>
+#include <support/xdlfcn.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+ void *h = xdlopen ("tst-auditmod19a.so", RTLD_NOW);
+
+ struct link_map *lmap;
+ TEST_VERIFY_EXIT (dlinfo (h, RTLD_DI_LINKMAP, &lmap) == 0);
+
+ /* The internal array is only allocated if profiling is enabled. */
+ TEST_VERIFY (lmap->l_reloc_result == NULL);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-audit19b.c b/elf/tst-audit19b.c
new file mode 100644
index 0000000000000000..da015734f24e0d79
--- /dev/null
+++ b/elf/tst-audit19b.c
@@ -0,0 +1,94 @@
+/* Check if DT_AUDIT a module with la_plt{enter,exit} call la_symbind
+ for lazy resolution.
+ Copyright (C) 2021 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
+ <https://www.gnu.org/licenses/>. */
+
+#include <getopt.h>
+#include <support/capture_subprocess.h>
+#include <support/check.h>
+#include <support/xstdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+static int restart;
+#define CMDLINE_OPTIONS \
+ { "restart", no_argument, &restart, 1 },
+
+int tst_audit18bmod1_func (void);
+
+static int
+handle_restart (void)
+{
+ TEST_COMPARE (tst_audit18bmod1_func (), 10);
+ return 0;
+}
+
+static inline bool
+startswith (const char *str, const char *pre)
+{
+ size_t lenpre = strlen (pre);
+ size_t lenstr = strlen (str);
+ return lenstr < lenpre ? false : memcmp (pre, str, lenpre) == 0;
+}
+
+static int
+do_test (int argc, char *argv[])
+{
+ /* We must have either:
+ - One our fource parameters left if called initially:
+ + path to ld.so optional
+ + "--library-path" optional
+ + the library path optional
+ + the application name */
+
+ if (restart)
+ return handle_restart ();
+
+ char *spargv[9];
+ int i = 0;
+ for (; i < argc - 1; i++)
+ spargv[i] = argv[i + 1];
+ spargv[i++] = (char *) "--direct";
+ spargv[i++] = (char *) "--restart";
+ spargv[i] = NULL;
+
+ setenv ("LD_AUDIT", "tst-auditmod18b.so", 0);
+ struct support_capture_subprocess result
+ = support_capture_subprogram (spargv[0], spargv);
+ support_capture_subprocess_check (&result, "tst-audit18b", 0, sc_allow_stderr);
+
+ bool find_symbind = false;
+
+ FILE *out = fmemopen (result.err.buffer, result.err.length, "r");
+ TEST_VERIFY (out != NULL);
+ char *buffer = NULL;
+ size_t buffer_length = 0;
+ while (xgetline (&buffer, &buffer_length, out))
+ if (startswith (buffer, "la_symbind: tst_audit18bmod1_func") == 0)
+ find_symbind = true;
+
+ TEST_COMPARE (find_symbind, true);
+
+ free (buffer);
+ xfclose (out);
+
+ return 0;
+}
+
+#define TEST_FUNCTION_ARGV do_test
+#include <support/test-driver.c>
diff --git a/elf/tst-audit19bmod.c b/elf/tst-audit19bmod.c
new file mode 100644
index 0000000000000000..9ffdcd8f3ffbc38e
--- /dev/null
+++ b/elf/tst-audit19bmod.c
@@ -0,0 +1,23 @@
+/* Extra module for tst-audit18b.
+ Copyright (C) 2021 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
+ <https://www.gnu.org/licenses/>. */
+
+int
+tst_audit18bmod1_func (void)
+{
+ return 10;
+}
diff --git a/elf/tst-auditmod19a.c b/elf/tst-auditmod19a.c
new file mode 100644
index 0000000000000000..f58204099457743d
--- /dev/null
+++ b/elf/tst-auditmod19a.c
@@ -0,0 +1,25 @@
+/* Audit module for tst-audit18a.
+ Copyright (C) 2021 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
+ <https://www.gnu.org/licenses/>. */
+
+#include <link.h>
+
+unsigned int
+la_version (unsigned int version)
+{
+ return LAV_CURRENT;
+}
diff --git a/elf/tst-auditmod19b.c b/elf/tst-auditmod19b.c
new file mode 100644
index 0000000000000000..e2248b2a75946746
--- /dev/null
+++ b/elf/tst-auditmod19b.c
@@ -0,0 +1,46 @@
+/* Audit module for tst-audit18b.
+ Copyright (C) 2021 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
+ <https://www.gnu.org/licenses/>. */
+
+#include <link.h>
+#include <string.h>
+#include <stdio.h>
+
+unsigned int
+la_version (unsigned int version)
+{
+ return LAV_CURRENT;
+}
+
+unsigned int
+la_objopen (struct link_map *map, Lmid_t lmid, uintptr_t *cookie)
+{
+ return LA_FLG_BINDTO | LA_FLG_BINDFROM;
+}
+
+uintptr_t
+#if __ELF_NATIVE_CLASS == 32
+la_symbind32 (Elf32_Sym *sym, unsigned int ndx, uintptr_t *refcook,
+ uintptr_t *defcook, unsigned int *flags, const char *symname)
+#else
+la_symbind64 (Elf64_Sym *sym, unsigned int ndx, uintptr_t *refcook,
+ uintptr_t *defcook, unsigned int *flags, const char *symname)
+#endif
+{
+ fprintf (stderr, "la_symbind: %s\n", symname);
+ return sym->st_value;
+}
diff --git a/include/link.h b/include/link.h
index cdd011f59445e490..dd491989beb41353 100644
--- a/include/link.h
+++ b/include/link.h
@@ -353,8 +353,10 @@ struct link_map
#if __ELF_NATIVE_CLASS == 32
# define symbind symbind32
+# define LA_SYMBIND "la_symbind32"
#elif __ELF_NATIVE_CLASS == 64
# define symbind symbind64
+# define LA_SYMBIND "la_symbind64"
#else
# error "__ELF_NATIVE_CLASS must be defined"
#endif