From patchwork Tue May 19 17:12:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 39324 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 EB52B3939C0F; Tue, 19 May 2020 17:12:41 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org EB52B3939C0F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1589908362; bh=+1E17osy8vWA576KNWtMETLWBCTF8Q8YwqHah/2X5AU=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:From; b=DK6HJ5AO9ouBmy3S0DnKabFPp9cwVipRfJUCH2PDhxex4dChuY696vHs8e9BCS5VN ZCYPELhSibnmbcs69LhsX+so55nEnLIWcYcToxKVBaTkppUYA8dyF43B69fVuxPLFz p6PE0IcK0afLQPVyRUDMOgbTgRXw8PIbjMbatTts= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by sourceware.org (Postfix) with ESMTP id 45DB53897830 for ; Tue, 19 May 2020 17:12:39 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 45DB53897830 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-504-ueM3Tb6uO8WnZt4rjuDMDw-1; Tue, 19 May 2020 13:12:36 -0400 X-MC-Unique: ueM3Tb6uO8WnZt4rjuDMDw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0D75964AD5 for ; Tue, 19 May 2020 17:12:36 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-113-18.ams2.redhat.com [10.36.113.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5DB4660BE1 for ; Tue, 19 May 2020 17:12:35 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH] elf: Remove extra hwcap mechanism from ldconfig Date: Tue, 19 May 2020 19:12:33 +0200 Message-ID: <87sgfvetmm.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-14.1 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, 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" Historically, this mechanism was used to process "nosegneg" subdirectories, and it is still used to include the "tls" subdirectories. With nosegneg support gone from ld.so, this is part no longer useful. The entire mechanism is not well-designed because it causes the meaning of hwcap bits in ld.so.cache to depend on the kernel version that was used to generate the cache, which makes it difficult to use this mechanism for anything else in the future. Tested on x86_64-linux-gnu and i686-linux-gnu. Manually verified that the generated (new-format) /etc/ld.so.cache file does not change with this patch on a reference system, with and without a shared object in a /usr/lib64/tls subdirectory. Reviewed-by: Adhemerval Zanella --- elf/ldconfig.c | 87 +++++++++++----------------------------------------------- 1 file changed, 16 insertions(+), 71 deletions(-) diff --git a/elf/ldconfig.c b/elf/ldconfig.c index 3b860ad732..0c090dca15 100644 --- a/elf/ldconfig.c +++ b/elf/ldconfig.c @@ -44,11 +44,15 @@ #include -#ifdef _DL_FIRST_PLATFORM -# define _DL_FIRST_EXTRA (_DL_FIRST_PLATFORM + _DL_PLATFORMS_COUNT) -#else -# define _DL_FIRST_EXTRA _DL_HWCAP_COUNT -#endif +/* This subpath in search path entries is always supported and + included in the cache for backwards compatibility. */ +#define TLS_SUBPATH "tls" + +/* The MSB of the hwcap field is set for objects in TLS_SUBPATH + directories. There is always TLS support in glibc, so the dynamic + loader does not check the bit directly. But more hwcap bits make a + an object more preferred, so the bit still has meaning. */ +#define TLS_HWCAP_BIT 63 #ifndef LD_SO_CONF # define LD_SO_CONF SYSCONFDIR "/ld.so.conf" @@ -127,9 +131,6 @@ static const char *config_file; /* Mask to use for important hardware capabilities. */ static unsigned long int hwcap_mask = HWCAP_IMPORTANT; -/* Configuration-defined capabilities defined in kernel vDSOs. */ -static const char *hwcap_extra[64 - _DL_FIRST_EXTRA]; - /* Name and version of program. */ static void print_version (FILE *stream, struct argp_state *state); void (*argp_program_version_hook) (FILE *, struct argp_state *) @@ -186,12 +187,9 @@ is_hwcap_platform (const char *name) if (hwcap_idx != -1) return 1; - /* Is this one of the extra pseudo-hwcaps that we map beyond - _DL_FIRST_EXTRA like "tls", or "nosegneg?" */ - for (hwcap_idx = _DL_FIRST_EXTRA; hwcap_idx < 64; ++hwcap_idx) - if (hwcap_extra[hwcap_idx - _DL_FIRST_EXTRA] != NULL - && !strcmp (name, hwcap_extra[hwcap_idx - _DL_FIRST_EXTRA])) - return 1; + /* Backwards-compatibility for the "tls" subdirectory. */ + if (strcmp (name, TLS_SUBPATH) == 0) + return 1; return 0; } @@ -226,11 +224,9 @@ path_hwcap (const char *path) h = _dl_string_platform (ptr + 1); if (h == (uint64_t) -1) { - for (h = _DL_FIRST_EXTRA; h < 64; ++h) - if (hwcap_extra[h - _DL_FIRST_EXTRA] != NULL - && !strcmp (ptr + 1, hwcap_extra[h - _DL_FIRST_EXTRA])) - break; - if (h == 64) + if (strcmp (ptr + 1, TLS_SUBPATH) == 0) + h = TLS_HWCAP_BIT; + else break; } } @@ -1146,52 +1142,7 @@ Warning: ignoring configuration file that cannot be opened: %s"), parse_conf_include (filename, lineno, do_chroot, dir); } else if (!strncasecmp (cp, "hwcap", 5) && isblank (cp[5])) - { - cp += 6; - char *p, *name = NULL; - unsigned long int n = strtoul (cp, &cp, 0); - if (cp != NULL && isblank (*cp)) - while ((p = strsep (&cp, " \t")) != NULL) - if (p[0] != '\0') - { - if (name == NULL) - name = p; - else - { - name = NULL; - break; - } - } - if (name == NULL) - { - error (EXIT_FAILURE, 0, _("%s:%u: bad syntax in hwcap line"), - filename, lineno); - break; - } - if (n >= (64 - _DL_FIRST_EXTRA)) - error (EXIT_FAILURE, 0, - _("%s:%u: hwcap index %lu above maximum %u"), - filename, lineno, n, 64 - _DL_FIRST_EXTRA - 1); - if (hwcap_extra[n] == NULL) - { - for (unsigned long int h = 0; h < (64 - _DL_FIRST_EXTRA); ++h) - if (hwcap_extra[h] != NULL && !strcmp (name, hwcap_extra[h])) - error (EXIT_FAILURE, 0, - _("%s:%u: hwcap index %lu already defined as %s"), - filename, lineno, h, name); - hwcap_extra[n] = xstrdup (name); - } - else - { - if (strcmp (name, hwcap_extra[n])) - error (EXIT_FAILURE, 0, - _("%s:%u: hwcap index %lu already defined as %s"), - filename, lineno, n, hwcap_extra[n]); - if (opt_verbose) - error (0, 0, _("%s:%u: duplicate hwcap %lu %s"), - filename, lineno, n, name); - } - } + error (0, 0, _("%s:%u: hwcap directive ignored"), filename, lineno); else add_dir_1 (cp, filename, lineno); } @@ -1304,12 +1255,6 @@ main (int argc, char **argv) add_dir_1 (argv[i], "", 0); } - /* The last entry in hwcap_extra is reserved for the "tls" pseudo-hwcap which - indicates support for TLS. This pseudo-hwcap is only used by old versions - under which TLS support was optional. The entry is no longer needed, but - must remain for compatibility. */ - hwcap_extra[63 - _DL_FIRST_EXTRA] = "tls"; - set_hwcap (); if (opt_chroot)