commit 600d9e0c87940da9b0fdeff492bf888df852d40c Author: Florian Weimer Date: Fri Dec 4 09:13:43 2020 +0100 elf: Add glibc-hwcaps subdirectory support to ld.so cache processing This recognizes the DL_CACHE_HWCAP_EXTENSION flag in cache entries, and picks the supported cache entry with the highest priority. The elf/tst-glibc-hwcaps-prepend-cache test documents a non-desired aspect of the current cache implementation: If the cache selects a DSO that does not exist on disk, _dl_map_object falls back to open_path, which may or may not find an alternative implementation. This is an existing limitation that also applies to the legacy hwcaps processing for ld.so.cache. Reviewed-by: Adhemerval Zanella diff --git a/elf/Makefile b/elf/Makefile index a3e802a9a99b759c..f67b231c0f8e3aff 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -162,6 +162,12 @@ tst-tls1-static-non-pie-no-pie = yes tests-container = \ tst-ldconfig-bad-aux-cache +ifeq (no,$(build-hardcoded-path-in-tests)) +# This is an ld.so.cache test, and RPATH/RUNPATH in the executable +# interferes with its test objectives. +tests-container += tst-glibc-hwcaps-prepend-cache +endif + tests := tst-tls9 tst-leaks1 \ tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \ tst-auxv tst-stringtable @@ -1784,6 +1790,14 @@ $(objpfx)tst-glibc-hwcaps-prepend.out: \ $< > $@; \ $(evaluate-test) +# Like tst-glibc-hwcaps-prepend, but uses a container and loads the +# library via ld.so.cache. Test setup is contained in the test +# itself. +$(objpfx)tst-glibc-hwcaps-prepend-cache: $(libdl) +$(objpfx)tst-glibc-hwcaps-prepend-cache.out: \ + $(objpfx)tst-glibc-hwcaps-prepend-cache $(objpfx)libmarkermod1-1.so \ + $(objpfx)libmarkermod1-2.so $(objpfx)libmarkermod1-3.so + # tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to # suppress all auto-detected subdirectories. $(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so @@ -1795,3 +1809,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \ --glibc-hwcaps-mask does-not-exist \ $< > $@; \ $(evaluate-test) + +# Generic dependency for sysdeps implementation of +# tst-glibc-hwcaps-cache. +$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps diff --git a/elf/dl-cache.c b/elf/dl-cache.c index de063faa8b2c88ae..e75afdaee23226e6 100644 --- a/elf/dl-cache.c +++ b/elf/dl-cache.c @@ -35,6 +35,144 @@ static struct cache_file *cache; static struct cache_file_new *cache_new; static size_t cachesize; +#ifdef SHARED +/* This is used to cache the priorities of glibc-hwcaps + subdirectories. The elements of _dl_cache_priorities correspond to + the strings in the cache_extension_tag_glibc_hwcaps section. */ +static uint32_t *glibc_hwcaps_priorities; +static uint32_t glibc_hwcaps_priorities_length; +static uint32_t glibc_hwcaps_priorities_allocated; + +/* True if the full malloc was used to allocated the array. */ +static bool glibc_hwcaps_priorities_malloced; + +/* Deallocate the glibc_hwcaps_priorities array. */ +static void +glibc_hwcaps_priorities_free (void) +{ + /* When the minimal malloc is in use, free does not do anything, + so it does not make sense to call it. */ + if (glibc_hwcaps_priorities_malloced) + free (glibc_hwcaps_priorities); + glibc_hwcaps_priorities = NULL; + glibc_hwcaps_priorities_allocated = 0; +} + +/* Ordered comparison of a hwcaps string from the cache on the left + (identified by its string table index) and a _dl_hwcaps_priorities + element on the right. */ +static int +glibc_hwcaps_compare (uint32_t left_index, struct dl_hwcaps_priority *right) +{ + const char *left_name = (const char *) cache + left_index; + uint32_t left_name_length = strlen (left_name); + uint32_t to_compare; + if (left_name_length < right->name_length) + to_compare = left_name_length; + else + to_compare = right->name_length; + int cmp = memcmp (left_name, right->name, to_compare); + if (cmp != 0) + return cmp; + if (left_name_length < right->name_length) + return -1; + else if (left_name_length > right->name_length) + return 1; + else + return 0; +} + +/* Initialize the glibc_hwcaps_priorities array and its length, + glibc_hwcaps_priorities_length. */ +static void +glibc_hwcaps_priorities_init (void) +{ + struct cache_extension_all_loaded ext; + if (!cache_extension_load (cache_new, cache, cachesize, &ext)) + return; + + uint32_t length = (ext.sections[cache_extension_tag_glibc_hwcaps].size + / sizeof (uint32_t)); + if (length > glibc_hwcaps_priorities_allocated) + { + glibc_hwcaps_priorities_free (); + + uint32_t *new_allocation = malloc (length * sizeof (uint32_t)); + if (new_allocation == NULL) + /* This effectively disables hwcaps on memory allocation + errors. */ + return; + + glibc_hwcaps_priorities = new_allocation; + glibc_hwcaps_priorities_allocated = length; + glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete (); + } + + /* Compute the priorities for the subdirectories by merging the + array in the cache with the dl_hwcaps_priorities array. */ + const uint32_t *left = ext.sections[cache_extension_tag_glibc_hwcaps].base; + const uint32_t *left_end = left + length; + struct dl_hwcaps_priority *right = _dl_hwcaps_priorities; + struct dl_hwcaps_priority *right_end = right + _dl_hwcaps_priorities_length; + uint32_t *result = glibc_hwcaps_priorities; + + while (left < left_end && right < right_end) + { + if (*left < cachesize) + { + int cmp = glibc_hwcaps_compare (*left, right); + if (cmp == 0) + { + *result = right->priority; + ++result; + ++left; + ++right; + } + else if (cmp < 0) + { + *result = 0; + ++result; + ++left; + } + else + ++right; + } + else + { + *result = 0; + ++result; + } + } + while (left < left_end) + { + *result = 0; + ++result; + ++left; + } + + glibc_hwcaps_priorities_length = length; +} + +/* Return the priority of the cache_extension_tag_glibc_hwcaps section + entry at INDEX. Zero means do not use. Otherwise, lower values + indicate greater preference. */ +static uint32_t +glibc_hwcaps_priority (uint32_t index) +{ + /* This does not need to repeated initialization attempts because + this function is only called if there is glibc-hwcaps data in the + cache, so the first call initializes the glibc_hwcaps_priorities + array. */ + if (glibc_hwcaps_priorities_length == 0) + glibc_hwcaps_priorities_init (); + + if (index < glibc_hwcaps_priorities_length) + return glibc_hwcaps_priorities[index]; + else + return 0; +} +#endif /* SHARED */ + /* True if PTR is a valid string table index. */ static inline bool _dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size) @@ -74,6 +212,9 @@ search_cache (const char *string_table, uint32_t string_table_size, int left = 0; int right = nlibs - 1; const char *best = NULL; +#ifdef SHARED + uint32_t best_priority = 0; +#endif while (left <= right) { @@ -129,6 +270,11 @@ search_cache (const char *string_table, uint32_t string_table_size, { if (best == NULL || flags == GLRO (dl_correct_cache_id)) { + /* Named/extension hwcaps get slightly different + treatment: We keep searching for a better + match. */ + bool named_hwcap = false; + if (entry_size >= sizeof (struct file_entry_new)) { /* The entry is large enough to include @@ -136,7 +282,18 @@ search_cache (const char *string_table, uint32_t string_table_size, struct file_entry_new *libnew = (struct file_entry_new *) lib; - if (libnew->hwcap & hwcap_exclude) +#ifdef SHARED + named_hwcap = dl_cache_hwcap_extension (libnew); +#endif + + /* The entries with named/extension hwcaps + have been exhausted. Return the best + match encountered so far if there is + one. */ + if (!named_hwcap && best != NULL) + break; + + if ((libnew->hwcap & hwcap_exclude) && !named_hwcap) continue; if (GLRO (dl_osversion) && libnew->osversion > GLRO (dl_osversion)) @@ -146,14 +303,41 @@ search_cache (const char *string_table, uint32_t string_table_size, && ((libnew->hwcap & _DL_HWCAP_PLATFORM) != platform)) continue; + +#ifdef SHARED + /* For named hwcaps, determine the priority + and see if beats what has been found so + far. */ + if (named_hwcap) + { + uint32_t entry_priority + = glibc_hwcaps_priority (libnew->hwcap); + if (entry_priority == 0) + /* Not usable at all. Skip. */ + continue; + else if (best == NULL + || entry_priority < best_priority) + /* This entry is of higher priority + than the previous one, or it is the + first entry. */ + best_priority = entry_priority; + else + /* An entry has already been found, + but it is a better match. */ + continue; + } +#endif /* SHARED */ } best = string_table + lib->value; - if (flags == GLRO (dl_correct_cache_id)) + if (flags == GLRO (dl_correct_cache_id) + && !named_hwcap) /* We've found an exact match for the shared object and no general `ELF' release. Stop - searching. */ + searching, but not if a named (extension) + hwcap is used. In this case, an entry with + a higher priority may come up later. */ break; } } @@ -346,5 +530,9 @@ _dl_unload_cache (void) __munmap (cache, cachesize); cache = NULL; } +#ifdef SHARED + /* This marks the glibc_hwcaps_priorities array as out-of-date. */ + glibc_hwcaps_priorities_length = 0; +#endif } #endif diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c index e57d0d2d41741021..098173a84c43c1fd 100644 --- a/elf/dl-hwcaps.c +++ b/elf/dl-hwcaps.c @@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps, } } +struct dl_hwcaps_priority *_dl_hwcaps_priorities; +uint32_t _dl_hwcaps_priorities_length; + +/* Allocate _dl_hwcaps_priorities and fill it with data. */ +static void +compute_priorities (size_t total_count, const char *prepend, + uint32_t bitmask, const char *mask) +{ + _dl_hwcaps_priorities = malloc (total_count + * sizeof (*_dl_hwcaps_priorities)); + if (_dl_hwcaps_priorities == NULL) + _dl_signal_error (ENOMEM, NULL, NULL, + N_("cannot create HWCAP priorities")); + _dl_hwcaps_priorities_length = total_count; + + /* First the prepended subdirectories. */ + size_t i = 0; + { + struct dl_hwcaps_split sp; + _dl_hwcaps_split_init (&sp, prepend); + while (_dl_hwcaps_split (&sp)) + { + _dl_hwcaps_priorities[i].name = sp.segment; + _dl_hwcaps_priorities[i].name_length = sp.length; + _dl_hwcaps_priorities[i].priority = i + 1; + ++i; + } + } + + /* Then the built-in subdirectories that are actually active. */ + { + struct dl_hwcaps_split_masked sp; + _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask); + while (_dl_hwcaps_split_masked (&sp)) + { + _dl_hwcaps_priorities[i].name = sp.split.segment; + _dl_hwcaps_priorities[i].name_length = sp.split.length; + _dl_hwcaps_priorities[i].priority = i + 1; + ++i; + } + } + assert (i == total_count); +} + +/* Sort the _dl_hwcaps_priorities array by name. */ +static void +sort_priorities_by_name (void) +{ + /* Insertion sort. There is no need to link qsort into the dynamic + loader for such a short array. */ + for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i) + for (size_t j = i; j > 0; --j) + { + struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1; + struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j; + + /* Bail out if current is greater or equal to the previous + value. */ + uint32_t to_compare; + if (current->name_length < previous->name_length) + to_compare = current->name_length; + else + to_compare = previous->name_length; + int cmp = memcmp (current->name, previous->name, to_compare); + if (cmp >= 0 + || (cmp == 0 && current->name_length >= previous->name_length)) + break; + + /* Swap *previous and *current. */ + struct dl_hwcaps_priority tmp = *previous; + *previous = *current; + *current = tmp; + } +} + /* Return an array of useful/necessary hardware capability names. */ const struct r_strlenpair * _dl_important_hwcaps (const char *glibc_hwcaps_prepend, @@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend, update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL); update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs, hwcaps_subdirs_active, glibc_hwcaps_mask); + compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend, + hwcaps_subdirs_active, glibc_hwcaps_mask); + sort_priorities_by_name (); /* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix and a "/" suffix once stored in the result. */ diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h index 3fcfbceb1a8fc1c8..769ecab3f886c6c4 100644 --- a/elf/dl-hwcaps.h +++ b/elf/dl-hwcaps.h @@ -132,4 +132,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active) return mask ^ ((1U << inactive) - 1); } +/* Pre-computed glibc-hwcaps subdirectory priorities. Used in + dl-cache.c to quickly find the proprieties for the stored HWCAP + names. */ +struct dl_hwcaps_priority +{ + /* The name consists of name_length bytes at name (not necessarily + null-terminated). */ + const char *name; + uint32_t name_length; + + /* Priority of this name. A positive number. */ + uint32_t priority; +}; + +/* Pre-computed hwcaps priorities. Set up by + _dl_important_hwcaps. */ +extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden; +extern uint32_t _dl_hwcaps_priorities_length attribute_hidden; + #endif /* _DL_HWCAPS_H */ diff --git a/elf/tst-glibc-hwcaps-cache.c b/elf/tst-glibc-hwcaps-cache.c new file mode 100644 index 0000000000000000..4bad56afc03451fc --- /dev/null +++ b/elf/tst-glibc-hwcaps-cache.c @@ -0,0 +1,45 @@ +/* Wrapper to invoke tst-glibc-hwcaps in a container, to test ld.so.cache. + Copyright (C) 2020 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 + . */ + +/* This program is just a wrapper that runs ldconfig followed by + tst-glibc-hwcaps. The actual test is provided via an + implementation in a sysdeps subdirectory. */ + +#include +#include +#include +#include + +int +main (int argc, char **argv) +{ + /* Run ldconfig to populate the cache. */ + { + char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir); + if (system (command) != 0) + return 1; + free (command); + } + + /* Reuse tst-glibc-hwcaps. Since this code is running in a + container, we can launch it directly. */ + char *path = xasprintf ("%s/elf/tst-glibc-hwcaps", support_objdir_root); + execv (path, argv); + printf ("error: execv of %s failed: %m\n", path); + return 1; +} diff --git a/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf new file mode 100644 index 0000000000000000..e1e74dbda2bf3dfa --- /dev/null +++ b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf @@ -0,0 +1,2 @@ +# This file was created to suppress a warning from ldconfig: +# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory diff --git a/elf/tst-glibc-hwcaps-cache.root/postclean.req b/elf/tst-glibc-hwcaps-cache.root/postclean.req new file mode 100644 index 0000000000000000..e69de29bb2d1d643 diff --git a/elf/tst-glibc-hwcaps-cache.script b/elf/tst-glibc-hwcaps-cache.script new file mode 100644 index 0000000000000000..6356d152089cdd9a --- /dev/null +++ b/elf/tst-glibc-hwcaps-cache.script @@ -0,0 +1,6 @@ +# test-container does not support scripts in sysdeps directories, so +# collect everything in one file. + +cp $B/elf/libmarkermod2-1.so $L/libmarkermod2.so +cp $B/elf/libmarkermod3-1.so $L/libmarkermod3.so +cp $B/elf/libmarkermod4-1.so $L/libmarkermod4.so diff --git a/elf/tst-glibc-hwcaps-prepend-cache.c b/elf/tst-glibc-hwcaps-prepend-cache.c new file mode 100644 index 0000000000000000..40509cebe2b5ba27 --- /dev/null +++ b/elf/tst-glibc-hwcaps-prepend-cache.c @@ -0,0 +1,149 @@ +/* Test that --glibc-hwcaps-prepend works, using dlopen and /etc/ld.so.cache. + Copyright (C) 2020 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 +#include +#include + +/* Invoke /sbin/ldconfig with some error checking. */ +static void +run_ldconfig (void) +{ + char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir); + TEST_COMPARE (system (command), 0); + free (command); +} + +/* The library under test. */ +#define SONAME "libmarkermod1.so" + +static int +do_test (void) +{ + if (dlopen (SONAME, RTLD_NOW) != NULL) + FAIL_EXIT1 (SONAME " is already on the search path"); + + /* Install the default implementation of libmarkermod1.so. */ + xmkdirp ("/etc", 0777); + support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n"); + xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777); + xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777); + { + char *src = xasprintf ("%s/elf/libmarkermod1-1.so", support_objdir_root); + support_copy_file (src, "/glibc-test/lib/" SONAME); + free (src); + } + run_ldconfig (); + { + /* The default implementation can now be loaded. */ + void *handle = xdlopen (SONAME, RTLD_NOW); + int (*marker1) (void) = xdlsym (handle, "marker1"); + TEST_COMPARE (marker1 (), 1); + xdlclose (handle); + } + + /* Add the first override to the directory that is searched last. */ + { + char *src = xasprintf ("%s/elf/libmarkermod1-2.so", support_objdir_root); + support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend2/" + SONAME); + free (src); + } + { + /* This is still the first implementation. The cache has not been + updated. */ + void *handle = xdlopen (SONAME, RTLD_NOW); + int (*marker1) (void) = xdlsym (handle, "marker1"); + TEST_COMPARE (marker1 (), 1); + xdlclose (handle); + } + run_ldconfig (); + { + /* After running ldconfig, it is the second implementation. */ + void *handle = xdlopen (SONAME, RTLD_NOW); + int (*marker1) (void) = xdlsym (handle, "marker1"); + TEST_COMPARE (marker1 (), 2); + xdlclose (handle); + } + + /* Add the second override to the directory that is searched first. */ + { + char *src = xasprintf ("%s/elf/libmarkermod1-3.so", support_objdir_root); + support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend3/" + SONAME); + free (src); + } + { + /* This is still the second implementation. */ + void *handle = xdlopen (SONAME, RTLD_NOW); + int (*marker1) (void) = xdlsym (handle, "marker1"); + TEST_COMPARE (marker1 (), 2); + xdlclose (handle); + } + run_ldconfig (); + { + /* After running ldconfig, it is the third implementation. */ + void *handle = xdlopen (SONAME, RTLD_NOW); + int (*marker1) (void) = xdlsym (handle, "marker1"); + TEST_COMPARE (marker1 (), 3); + xdlclose (handle); + } + + /* Remove the second override again, without running ldconfig. + Ideally, this would revert to implementation 2. However, in the + current implementation, the cache returns exactly one file name + which does not exist after unlinking, so the dlopen fails. */ + xunlink ("/glibc-test/lib/glibc-hwcaps/prepend3/" SONAME); + TEST_VERIFY (dlopen (SONAME, RTLD_NOW) == NULL); + run_ldconfig (); + { + /* After running ldconfig, the second implementation is available + once more. */ + void *handle = xdlopen (SONAME, RTLD_NOW); + int (*marker1) (void) = xdlsym (handle, "marker1"); + TEST_COMPARE (marker1 (), 2); + xdlclose (handle); + } + + return 0; +} + +static void +prepare (int argc, char **argv) +{ + const char *no_restart = "no-restart"; + if (argc == 2 && strcmp (argv[1], no_restart) == 0) + return; + /* Re-execute the test with an explicit loader invocation. */ + execl (support_objdir_elf_ldso, + support_objdir_elf_ldso, + "--glibc-hwcaps-prepend", "prepend3:prepend2", + argv[0], no_restart, + NULL); + printf ("error: execv of %s failed: %m\n", argv[0]); + _exit (1); +} + +#define PREPARE prepare +#include diff --git a/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req b/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req new file mode 100644 index 0000000000000000..e69de29bb2d1d643