From patchwork Thu May 18 20:07:15 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Siddhesh Poyarekar X-Patchwork-Id: 20492 Received: (qmail 116422 invoked by alias); 18 May 2017 20:07:39 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 116315 invoked by uid 89); 18 May 2017 20:07:38 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-26.1 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_NEUTRAL autolearn=ham version=3.3.2 spammy=Capability, cores, online X-HELO: homiemail-a68.g.dreamhost.com From: Siddhesh Poyarekar To: libc-alpha@sourceware.org Cc: adhemerval.zanella@linaro.org Subject: [PATCH 2/5] tunables: Add LD_HWCAP_MASK to tunables Date: Fri, 19 May 2017 01:37:15 +0530 Message-Id: <1495138038-32212-3-git-send-email-siddhesh@sourceware.org> In-Reply-To: <1495138038-32212-1-git-send-email-siddhesh@sourceware.org> References: <1495138038-32212-1-git-send-email-siddhesh@sourceware.org> Add LD_HWCAP_MASK to tunables in preparation of it being removed from rtld.c. This allows us to read LD_HWCAP_MASK much earlier so that it can influence IFUNC resolution in aarch64. This patch does not actually do anything other than read the LD_HWCAP_MASK variable and add the tunables way to set the LD_HWCAP_MASK, i.e. via the glibc.tune.hwcap_mask tunable. In a follow-up patch, the _dl_hwcap_mask will be replaced with glibc.tune.hwcap_mask to complete the transition. * elf/dl-tunables.list: Add glibc.tune.hwcap_mask. * scripts/gen-tunables.awk: Include dl-procinfo.h. * manual/tunables.texi: Document glibc.tune.hwcap_mask. --- elf/dl-tunables.list | 7 +++++++ manual/tunables.texi | 22 ++++++++++++++++++++++ scripts/gen-tunables.awk | 1 + 3 files changed, 30 insertions(+) diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list index b9f1488..41ce9af 100644 --- a/elf/dl-tunables.list +++ b/elf/dl-tunables.list @@ -77,4 +77,11 @@ glibc { security_level: SXID_IGNORE } } + tune { + hwcap_mask { + type: UINT_64 + env_alias: LD_HWCAP_MASK + default: HWCAP_IMPORTANT + } + } } diff --git a/manual/tunables.texi b/manual/tunables.texi index ac8c38f..37aefca 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -31,6 +31,8 @@ their own namespace. @menu * Tunable names:: The structure of a tunable name * Memory Allocation Tunables:: Tunables in the memory allocation subsystem +* Hardware Capability Tunables:: Tunables that modify the hardware + capabilities seen by @theglibc{} @end menu @node Tunable names @@ -190,3 +192,23 @@ number of arenas is determined by the number of CPU cores online. For 32-bit systems the limit is twice the number of cores online and on 64-bit systems, it is 8 times the number of cores online. @end deftp + +@node Hardware Capability Tunables +@section Hardware Capability Tunables +@cindex hardware capability tunables +@cindex hwcap tunables +@cindex tunables, hwcap + +@deftp {Tunable namespace} glibc.tune +Behavior of @theglibc{} can be tuned to assume specific hardware capabilities +by setting the following tunables in the @code{tune} namespace: +@end deftp + +@deftp Tunable glibc.tune.hwcap_mask +This tunable supersedes the @env{LD_HWCAP_MASK} environment variable and is +identical in features. + +The @code{AT_HWCAP} key in the Auxilliary Vector specifies instruction set +extensions available in the processor at runtime for some architectures. The +@code{glibc.tune.hwcap_mask} tunable allows the user to mask out those +capabilities at runtime, thus disabling use of those extensions. diff --git a/scripts/gen-tunables.awk b/scripts/gen-tunables.awk index b10b00e..93e5aff 100644 --- a/scripts/gen-tunables.awk +++ b/scripts/gen-tunables.awk @@ -134,6 +134,7 @@ END { print "# error \"Do not include this file directly.\"" print "# error \"Include tunables.h instead.\"" print "#endif" + print "#include \n" # Now, the enum names print "\ntypedef enum"