commit 29496b3103ff13aa3c1d8b62552a98f39da0fe59 Author: Adhemerval Zanella 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 Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu. Reviewed-by: Florian Weimer (cherry picked from commit 063f9ba220f434c7f30dd65c4cff17c0c458a7cf) Resolved conflicts: NEWS elf/Makefile diff --git a/elf/Makefile b/elf/Makefile index 85165c0591412a45..eab9d46b6165e6be 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -365,6 +365,7 @@ tests += \ tst-audit16 \ tst-audit17 \ tst-audit18 \ + tst-audit19b \ tst-auditmany \ tst-auxobj \ tst-auxobj-dlopen \ @@ -454,6 +455,7 @@ tests-internal += \ neededtest2 \ neededtest3 \ neededtest4 \ + tst-audit19a \ tst-create_format1 \ tst-dl-hwcaps_split \ tst-dlmopen2 \ @@ -626,6 +628,7 @@ modules-names = \ tst-audit12mod3 \ tst-audit13mod1 \ tst-audit18mod \ + tst-audit19bmod \ tst-auditlogmod-1 \ tst-auditlogmod-2 \ tst-auditlogmod-3 \ @@ -644,6 +647,8 @@ modules-names = \ tst-auditmod11 \ tst-auditmod12 \ tst-auditmod18 \ + tst-auditmod19a \ + tst-auditmod19b \ tst-auxvalmod \ tst-big-note-lib \ tst-deep1mod1 \ @@ -2007,6 +2012,13 @@ $(objpfx)tst-audit18.out: $(objpfx)tst-auditmod18.so \ $(objpfx)tst-audit18mod.so tst-audit18-ARGS = -- $(host-test-program-cmd) +$(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 3447de7f3536cd70..5b69321bda1f2b27 100644 --- a/elf/dl-reloc.c +++ b/elf/dl-reloc.c @@ -205,12 +205,28 @@ _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) @@ -272,7 +288,7 @@ _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 e42f6e8b8dfca08e..77a5cccdcbcb9293 100644 --- a/elf/dl-runtime.c +++ b/elf/dl-runtime.c @@ -124,6 +124,37 @@ _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 b6bb46ca97b7972f..f632a767d7a269ef 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -1016,13 +1016,7 @@ 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 + . */ + +#include +#include +#include + +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 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 + . */ + +#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 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 + . */ + +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 + . */ + +#include + +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 + . */ + +#include +#include +#include + +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 4dcf01d8aea90bc2..b3f160c278222b3c 100644 --- a/include/link.h +++ b/include/link.h @@ -363,8 +363,10 @@ 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