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From: Florian Weimer <fw@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] elf: Fix glibc-hwcaps priorities with cache flags mismatches [BZ #27046] Date: Fri, 25 Jun 2021 06:28:23 +0000 (GMT) [thread overview] Message-ID: <20210625062823.0199039BB01B@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=66db95b6e8264c5a6307f6a9e5285fec76907254 commit 66db95b6e8264c5a6307f6a9e5285fec76907254 Author: Florian Weimer <fweimer@redhat.com> Date: Fri Jun 25 08:02:30 2021 +0200 elf: Fix glibc-hwcaps priorities with cache flags mismatches [BZ #27046] If lib->flags (in the cache) did not match GLRO (dl_correct_cache_id), searching for further glibc-hwcaps entries did not happen, and it was possible that the best glibc-hwcaps was not found. By accident, this causes a test failure for elf/tst-glibc-hwcaps-prepend-cache on armv7l. This commit changes the cache lookup logic to continue searching if (a) no match has been found, (b) a named glibc-hwcaps match has been found(), or (c) non-glibc-hwcaps match has been found and the entry flags and cache default flags do not match. _DL_CACHE_DEFAULT_ID is used instead of GLRO (dl_correct_cache_id) because the latter is only written once on i386 if loading of libc.so.5 libraries is selected, so GLRO (dl_correct_cache_id) should probably removed in a future change. Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Diff: --- elf/dl-cache.c | 124 ++++++++++++++++++++++++++++----------------------------- 1 file changed, 60 insertions(+), 64 deletions(-) diff --git a/elf/dl-cache.c b/elf/dl-cache.c index 32f3bef5ea..2b8da8650d 100644 --- a/elf/dl-cache.c +++ b/elf/dl-cache.c @@ -269,81 +269,77 @@ search_cache (const char *string_table, uint32_t string_table_size, if (_dl_cache_check_flags (flags) && _dl_cache_verify_ptr (lib->value, 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; + /* 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 - HWCAP data. Check it. */ - struct file_entry_new *libnew - = (struct file_entry_new *) lib; + if (entry_size >= sizeof (struct file_entry_new)) + { + /* The entry is large enough to include + HWCAP data. Check it. */ + struct file_entry_new *libnew + = (struct file_entry_new *) lib; #ifdef SHARED - named_hwcap = dl_cache_hwcap_extension (libnew); - if (named_hwcap - && !dl_cache_hwcap_isa_level_compatible (libnew)) - continue; + named_hwcap = dl_cache_hwcap_extension (libnew); + if (named_hwcap + && !dl_cache_hwcap_isa_level_compatible (libnew)) + continue; #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; + /* The entries with named/extension hwcaps have + been exhausted (they are listed before all + other entries). 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)) - continue; - if (_DL_PLATFORMS_COUNT - && (libnew->hwcap & _DL_HWCAP_PLATFORM) != 0 - && ((libnew->hwcap & _DL_HWCAP_PLATFORM) - != platform)) - continue; + if ((libnew->hwcap & hwcap_exclude) && !named_hwcap) + continue; + if (GLRO (dl_osversion) + && libnew->osversion > GLRO (dl_osversion)) + continue; + if (_DL_PLATFORMS_COUNT + && (libnew->hwcap & _DL_HWCAP_PLATFORM) != 0 + && ((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 */ + /* 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; + best = string_table + lib->value; - 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, but not if a named (extension) - hwcap is used. In this case, an entry with - a higher priority may come up later. */ - break; - } + if (!named_hwcap && flags == _DL_CACHE_DEFAULT_ID) + /* With named hwcaps, we need to keep searching to + see if we find a better match. A better match + is also possible if the flags of the current + entry do not match the expected cache flags. + But if the flags match, no better entry will be + found. */ + break; } } while (++middle <= right);
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