From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2178) id F086A3945049; Wed, 14 Oct 2020 15:12:32 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org F086A3945049 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Florian Weimer To: glibc-cvs@sourceware.org Subject: [glibc/fw/glibc-hwcaps] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing X-Act-Checkin: glibc X-Git-Author: Florian Weimer X-Git-Refname: refs/heads/fw/glibc-hwcaps X-Git-Oldrev: be11be5a516f20f353798683f23f23535c2fcb19 X-Git-Newrev: 587fc3e8e3ef420e6d2303f937d25aed327c2bce Message-Id: <20201014151232.F086A3945049@sourceware.org> Date: Wed, 14 Oct 2020 15:12:32 +0000 (GMT) X-BeenThere: glibc-cvs@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Glibc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 Oct 2020 15:12:33 -0000 https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=587fc3e8e3ef420e6d2303f937d25aed327c2bce commit 587fc3e8e3ef420e6d2303f937d25aed327c2bce Author: Florian Weimer Date: Mon Oct 12 16:53:20 2020 +0200 elf: Add glibc-hwcaps subdirectory support to ld.so cache processing This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up the supported cache entry with the highest priority. Diff: --- elf/dl-cache.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++- elf/dl-hwcaps.c | 78 ++++++++++++++++++++++++ elf/dl-hwcaps.h | 19 ++++++ 3 files changed, 276 insertions(+), 3 deletions(-) diff --git a/elf/dl-cache.c b/elf/dl-cache.c index 02c46ffb0c..13efc6f95f 100644 --- a/elf/dl-cache.c +++ b/elf/dl-cache.c @@ -35,6 +35,132 @@ 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; +} + +/* 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 __attribute__ ((noinline, noclone)) +glibc_hwcaps_priority (uint32_t index) +{ + /* Using a zero-length array as an indicator that nothing has been + loaded is not a problem: It does not lead to repeated + initialization attempts because caches without an extension + section are processed without calling this function (unless the + file is corrupted). */ + if (glibc_hwcaps_priorities_length == 0) + { + struct cache_extension_all_loaded ext; + if (!cache_extension_load (cache_new, cache, cachesize, &ext)) + return 0; + + uint32_t length + = (ext.sections[cache_extension_tag_glibc_hwcaps].size + / sizeof (uint32_t)); + if (length > glibc_hwcaps_priorities_allocated) + { + glibc_hwcaps_priorities_free (); + + glibc_hwcaps_priorities = malloc (length * sizeof (uint32_t)); + if (glibc_hwcaps_priorities == NULL) + /* Disable hwcaps on memory allocation error. */ + return 0; + + 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) + { + uint32_t string_table_index = *left; + if (string_table_index < cachesize) + { + const char *left_name + = (const char *) cache + string_table_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) + { + if (left_name_length < right->name_length) + cmp = -1; + else if (left_name_length > right->name_length) + cmp = 1; + } + 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; + } + + 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 +200,9 @@ 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 +258,11 @@ 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 +270,18 @@ 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 +291,41 @@ 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 +518,9 @@ _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 f611f3a1a6..51cc787b54 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, + int32_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 8a42926ac2..8a4b6fd9eb 100644 --- a/elf/dl-hwcaps.h +++ b/elf/dl-hwcaps.h @@ -131,4 +131,23 @@ _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 proprities 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 */