From 063f9ba220f434c7f30dd65c4cff17c0c458a7cf Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Wed, 30 Jun 2021 10:24:09 -0300 Subject: 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 Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu. Reviewed-by: Florian Weimer --- elf/tst-audit19b.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 elf/tst-audit19b.c (limited to 'elf/tst-audit19b.c') diff --git a/elf/tst-audit19b.c b/elf/tst-audit19b.c new file mode 100644 index 0000000000..da015734f2 --- /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 + . */ + +#include +#include +#include +#include +#include +#include +#include + +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 -- cgit 1.4.1