[2/5] elf: Avoid unnecessary slowdown from profiling with audit (BZ#15533)

diff --git a/elf/Makefile b/elf/Makefile
index 5214196de6..a26f5ce320 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -219,7 +219,8 @@  tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-dlopen-self tst-auditmany tst-initfinilazyfail tst-dlopenfail \
 	 tst-dlopenfail-2 \
 	 tst-filterobj tst-filterobj-dlopen tst-auxobj tst-auxobj-dlopen \
-	 tst-audit14 tst-audit15 tst-audit16 tst-audit17 \
+	 tst-audit14 tst-audit15 tst-audit16 tst-audit17 tst-audit18a \
+	 tst-audit18b \
 	 tst-single_threaded tst-single_threaded-pthread \
 	 tst-tls-ie tst-tls-ie-dlmopen argv0test \
 	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
@@ -294,6 +295,7 @@  modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-unique1mod1 tst-unique1mod2 \
 		tst-unique2mod1 tst-unique2mod2 \
 		tst-auditmod9a tst-auditmod9b \
+		tst-auditmod18a tst-audit18bmod tst-auditmod18b \
 		$(if $(CXX),tst-unique3lib tst-unique3lib2 tst-unique4lib \
 		  tst-nodelete-uniquemod tst-nodelete-rtldmod \
 		  tst-nodelete-zmod \
@@ -1478,6 +1480,15 @@  $(objpfx)tst-auditmod17.so: $(objpfx)tst-auditmod17.os
 	mv -f $@.new $@
 tst-audit17-ENV = LD_AUDIT=$(objpfx)tst-auditmod17.so
 
+$(objpfx)tst-audit18a.out: $(objpfx)tst-auditmod18a.so
+tst-audit18a-ENV = LD_AUDIT=$(objpfx)tst-auditmod18a.so
+$(objpfx)tst-audit18b.out: $(objpfx)tst-auditmod18b.so \
+			   $(objpfx)tst-audit18bmod.so
+$(objpfx)tst-audit18b: $(objpfx)tst-audit18bmod.so
+LDFLAGS-tst-audit18bmod.so = -Wl,-z,now
+LDFLAGS-tst-audit18b = -Wl,-z,now
+tst-audit18b-ENV = LD_AUDIT=$(objpfx)tst-auditmod18b.so
+
 # 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 e13a672ade..998cfef099 100644
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -181,7 +181,18 @@  _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
 #ifdef SHARED
   /* 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->symbind != NULL
+	      || afct->ARCH_LA_PLTENTER != NULL
+	      || afct->ARCH_LA_PLTEXIT != NULL)
+	    consider_profiling = 1;
+	  afct = afct->next;
+	}
+    }
 #elif defined PROF
   /* Never use dynamic linker profiling for gprof profiling code.  */
 # define consider_profiling 0
diff --git a/elf/rtld.c b/elf/rtld.c
index fbbd60b446..bf9eb5a33e 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1014,13 +1014,7 @@  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-audit18a.c b/elf/tst-audit18a.c
new file mode 100644
index 0000000000..36b781f9be
--- /dev/null
+++ b/elf/tst-audit18a.c
@@ -0,0 +1,39 @@ 
+/* 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 <stdio.h>
+
+/* We interpose the profile resolver and if it is called it means profiling is
+   enabled.  */
+void
+_dl_runtime_profile (ElfW(Word) addr)
+{
+  volatile int *p = NULL;
+  *p = 0;
+}
+
+static int
+do_test (void)
+{
+  printf ("...");
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-audit18b.c b/elf/tst-audit18b.c
new file mode 100644
index 0000000000..21381fe950
--- /dev/null
+++ b/elf/tst-audit18b.c
@@ -0,0 +1,30 @@ 
+/* Check if DT_AUDIT a module built with bind-now does trigger la_symbind.
+   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/>.  */
+
+extern int foo (void);
+
+int
+do_test (void)
+{
+  foo ();
+  /* If audit la_symbind() callback is called it will exit the test with
+      EXIT_SUCCESS.  */
+  return 1;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-audit18bmod.c b/elf/tst-audit18bmod.c
new file mode 100644
index 0000000000..91f171b5bc
--- /dev/null
+++ b/elf/tst-audit18bmod.c
@@ -0,0 +1,22 @@ 
+/* Check if DT_AUDIT a module built with bind-now does trigger la_symbind.
+   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 foo (void)
+{
+  return 0;
+}
diff --git a/elf/tst-auditmod18a.c b/elf/tst-auditmod18a.c
new file mode 100644
index 0000000000..333db0077c
--- /dev/null
+++ b/elf/tst-auditmod18a.c
@@ -0,0 +1,25 @@ 
+/* Check if DT_ADIT 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/>.  */
+
+unsigned int
+la_version (unsigned int version)
+{
+  return version;
+}
+
diff --git a/elf/tst-auditmod18b.c b/elf/tst-auditmod18b.c
new file mode 100644
index 0000000000..40ebcd5be2
--- /dev/null
+++ b/elf/tst-auditmod18b.c
@@ -0,0 +1,48 @@ 
+/* Check if DT_AUDIT a module built with bind-now does trigger la_symbind.
+   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 <stdlib.h>
+#include <string.h>
+
+unsigned int
+la_version (unsigned int version)
+{
+  return version;
+}
+
+unsigned int
+la_objopen (struct link_map* map, Lmid_t lmid, uintptr_t* cookie)
+{
+  return LA_FLG_BINDFROM | LA_FLG_BINDTO;
+}
+
+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
+{
+  /* Filter out glibc own symbols libc.so is not built with -z,now.  */
+  if (strcmp (symname, "foo") == 0)
+    exit (EXIT_SUCCESS);
+  return sym->st_value;
+} 
diff --git a/include/link.h b/include/link.h
index 4af16cb596..ebd0f511e2 100644
--- a/include/link.h
+++ b/include/link.h
@@ -355,8 +355,10 @@  struct auditstate
 
 #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