From patchwork Mon Nov 9 18:40:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 40972 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 489413896C12; Mon, 9 Nov 2020 18:40:52 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 489413896C12 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1604947252; bh=QNn2ckXMcas1R/BtK0lUqBYs925AetaG1eb13Vc7IIE=; h=To:Subject:In-Reply-To:References:Date:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=BUf0NYPNhvR4PSi9Pq4EFNKQ2VVavoQX671OTYBqiQubkQ8OTveeKoLXdk331i2a+ QkhfzBHUWthDH7U/WTyc1I3DBchuxncf3V3urXu9FARso1OeyonEuM2kmHLYwhDSFZ 7fpR8UUjLX9Z8wh8ri3sIx0Mb8tzk5gAjSDsFAZc= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id C92ED388CC0E for ; Mon, 9 Nov 2020 18:40:49 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org C92ED388CC0E Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-199-Jq-6_TCsPbaHJffVdS0eOQ-1; Mon, 09 Nov 2020 13:40:47 -0500 X-MC-Unique: Jq-6_TCsPbaHJffVdS0eOQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A30E4186DD2A for ; Mon, 9 Nov 2020 18:40:46 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-113-222.ams2.redhat.com [10.36.113.222]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ED0CD10001B3 for ; Mon, 9 Nov 2020 18:40:45 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH 04/11] elf: Add endianness markup to ld.so.cache In-Reply-To: References: Message-Id: Date: Mon, 09 Nov 2020 19:40:44 +0100 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.2 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Florian Weimer via Libc-alpha From: Florian Weimer Reply-To: Florian Weimer Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Use a reserved byte in the new format cache header to indicate whether the file is in little endian or big endian format. Eventually, this information could be used to provide a unified cache for qemu-user and similiar scenarios. Reviewed-by: Adhemerval Zanella --- elf/cache.c | 11 +++++++ elf/dl-cache.c | 20 +++++++++++- sysdeps/generic/dl-cache.h | 62 +++++++++++++++++++++++++++++++++++++- 3 files changed, 91 insertions(+), 2 deletions(-) diff --git a/elf/cache.c b/elf/cache.c index c241c17ef9..ffecbe6d82 100644 --- a/elf/cache.c +++ b/elf/cache.c @@ -152,6 +152,14 @@ print_entry (const char *lib, int flag, unsigned int osversion, printf (") => %s\n", key); } +/* Print an error and exit if the new-file cache is internally + inconsistent. */ +static void +check_new_cache (struct cache_file_new *cache) +{ + if (! cache_file_new_matches_endian (cache)) + error (EXIT_FAILURE, 0, _("Cache file has wrong endianness.\n")); +} /* Print the whole cache file, if a file contains the new cache format hidden in the old one, print the contents of the new format. */ @@ -193,6 +201,7 @@ print_cache (const char *cache_name) || memcmp (cache_new->version, CACHE_VERSION, sizeof CACHE_VERSION - 1)) error (EXIT_FAILURE, 0, _("File is not a cache file.\n")); + check_new_cache (cache_new); format = 1; /* This is where the strings start. */ cache_data = (const char *) cache_new; @@ -222,6 +231,7 @@ print_cache (const char *cache_name) && memcmp (cache_new->version, CACHE_VERSION, sizeof CACHE_VERSION - 1) == 0) { + check_new_cache (cache_new); cache_data = (const char *) cache_new; format = 1; } @@ -361,6 +371,7 @@ save_cache (const char *cache_name) file_entries_new->nlibs = cache_entry_count; file_entries_new->len_strings = total_strlen; + file_entries_new->flags = cache_file_new_flags_endian_current; } /* Pad for alignment of cache_file_new. */ diff --git a/elf/dl-cache.c b/elf/dl-cache.c index 45894ecd2f..02c46ffb0c 100644 --- a/elf/dl-cache.c +++ b/elf/dl-cache.c @@ -242,6 +242,11 @@ _dl_load_cache_lookup (const char *name) && ((cachesize - sizeof *cache_new) / sizeof (struct file_entry_new) >= ((struct cache_file_new *) file)->nlibs)) { + if (! cache_file_new_matches_endian (file)) + { + __munmap (file, cachesize); + file = (void *) -1; + } cache_new = file; cache = file; } @@ -263,7 +268,20 @@ _dl_load_cache_lookup (const char *name) if (cachesize < (offset + sizeof (struct cache_file_new)) || memcmp (cache_new->magic, CACHEMAGIC_VERSION_NEW, sizeof CACHEMAGIC_VERSION_NEW - 1) != 0) - cache_new = (void *) -1; + cache_new = (void *) -1; + else + { + if (! cache_file_new_matches_endian (cache_new)) + { + /* The old-format part of the cache is bogus as well + if the endianness does not match. (But it is + unclear how the new header can be located if the + endianess does not match.) */ + cache = (void *) -1; + cache_new = (void *) -1; + __munmap (file, cachesize); + } + } } else { diff --git a/sysdeps/generic/dl-cache.h b/sysdeps/generic/dl-cache.h index 4ddd96b005..46026e0988 100644 --- a/sysdeps/generic/dl-cache.h +++ b/sysdeps/generic/dl-cache.h @@ -16,6 +16,11 @@ License along with the GNU C Library; if not, see . */ +#ifndef _DL_CACHE_H +#define _DL_CACHE_H + +#include +#include #include #ifndef _DL_CACHE_DEFAULT_ID @@ -92,21 +97,76 @@ struct file_entry_new uint64_t hwcap; /* Hwcap entry. */ }; +/* See flags member of struct cache_file_new below. */ +enum + { + /* No endianness information available. An old ldconfig version + without endianness support wrote the file. */ + cache_file_new_flags_endian_unset = 0, + + /* Cache is invalid and should be ignored. */ + cache_file_new_flags_endian_invalid = 1, + + /* Cache format is little endian. */ + cache_file_new_flags_endian_little = 2, + + /* Cache format is big endian. */ + cache_file_new_flags_endian_big = 3, + + /* Bit mask to extract the cache_file_new_flags_endian_* + values. */ + cache_file_new_flags_endian_mask = 3, + + /* Expected value of the endian bits in the flags member for the + current architecture. */ + cache_file_new_flags_endian_current + = (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ + ? cache_file_new_flags_endian_little + : cache_file_new_flags_endian_big), + }; + struct cache_file_new { char magic[sizeof CACHEMAGIC_NEW - 1]; char version[sizeof CACHE_VERSION - 1]; uint32_t nlibs; /* Number of entries. */ uint32_t len_strings; /* Size of string table. */ - uint32_t unused[5]; /* Leave space for future extensions + + /* flags & cache_file_new_flags_endian_mask is one of the values + cache_file_new_flags_endian_unset, cache_file_new_flags_endian_invalid, + cache_file_new_flags_endian_little, cache_file_new_flags_endian_big. + + The remaining bits are unused and should be generated as zero and + ignored by readers. */ + uint8_t flags; + + uint8_t padding_unsed[3]; /* Not used, for future extensions. */ + + uint32_t unused[4]; /* Leave space for future extensions and align to 8 byte boundary. */ struct file_entry_new libs[0]; /* Entries describing libraries. */ /* After this the string table of size len_strings is found. */ }; +/* Returns false if *CACHE has the wrong endianness for this + architecture, and true if the endianness matches (or is + unknown). */ +static inline bool +cache_file_new_matches_endian (const struct cache_file_new *cache) +{ + /* A zero value for cache->flags means that no endianness + information is available. */ + return cache->flags == 0 + || ((cache->flags & cache_file_new_flags_endian_big) + == cache_file_new_flags_endian_current); +} + + /* Used to align cache_file_new. */ #define ALIGN_CACHE(addr) \ (((addr) + __alignof__ (struct cache_file_new) -1) \ & (~(__alignof__ (struct cache_file_new) - 1))) extern int _dl_cache_libcmp (const char *p1, const char *p2) attribute_hidden; + +#endif /* _DL_CACHE_H */