From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 40383 invoked by alias); 18 Mar 2015 13:59:10 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 40368 invoked by uid 89); 18 Mar 2015 13:59:10 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=4.8 required=5.0 tests=AWL,BAYES_50,FREEMAIL_FROM,KAM_FROM_URIBL_PCCC,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=no version=3.3.2 X-HELO: mail-oi0-f42.google.com Received: from mail-oi0-f42.google.com (HELO mail-oi0-f42.google.com) (209.85.218.42) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Wed, 18 Mar 2015 13:59:07 +0000 Received: by oigv203 with SMTP id v203so36727342oig.3 for ; Wed, 18 Mar 2015 06:59:05 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.182.20.195 with SMTP id p3mr56128517obe.1.1426687145846; Wed, 18 Mar 2015 06:59:05 -0700 (PDT) Received: by 10.202.187.66 with HTTP; Wed, 18 Mar 2015 06:59:05 -0700 (PDT) In-Reply-To: References: <20150318115630.GA64546@msticlxl57.ims.intel.com> Date: Wed, 18 Mar 2015 13:59:00 -0000 Message-ID: Subject: Re: [PATCH, libmpx, i386, PR driver/65444] Pass '-z bndplt' when building dynamic objects with MPX From: Ilya Enkovich To: "H.J. Lu" Cc: Richard Biener , GCC Patches , Uros Bizjak Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2015-03/txt/msg00939.txt.bz2 2015-03-18 16:52 GMT+03:00 H.J. Lu : > On Wed, Mar 18, 2015 at 6:41 AM, Ilya Enkovich wrote: >> 2015-03-18 16:31 GMT+03:00 H.J. Lu : >>> On Wed, Mar 18, 2015 at 6:24 AM, Ilya Enkovich wrote: >>>> 2015-03-18 15:42 GMT+03:00 Richard Biener : >>>>> On Wed, Mar 18, 2015 at 1:25 PM, H.J. Lu wrote: >>>>>> On Wed, Mar 18, 2015 at 5:13 AM, Ilya Enkovich wrote: >>>>>>> 2015-03-18 15:08 GMT+03:00 H.J. Lu : >>>>>>>> On Wed, Mar 18, 2015 at 5:05 AM, Ilya Enkovich wrote: >>>>>>>>> 2015-03-18 15:02 GMT+03:00 H.J. Lu : >>>>>>>>>> On Wed, Mar 18, 2015 at 4:56 AM, Ilya Enkovich wrote: >>>>>>>>>>> Hi, >>>>>>>>>>> >>>>>>>>>>> This patch fixes PR target/65444 by passing '-z bndplt' to linker when appropriate. Bootstrapped and tested on x86_64-unknown-linux-gnu. Will commit it to trunk in a couple of days if no objections arise. >>>>>>>>>>> >>>>>>>>>>> Thanks, >>>>>>>>>>> Ilya >>>>>>>>>>> -- >>>>>>>>>>> gcc/ >>>>>>>>>>> >>>>>>>>>>> 2015-03-18 Ilya Enkovich >>>>>>>>>>> >>>>>>>>>>> PR driver/65444 >>>>>>>>>>> * config/i386/linux-common.h (MPX_SPEC): New. >>>>>>>>>>> (CHKP_SPEC): Add MPX_SPEC. >>>>>>>>>>> >>>>>>>>>>> libmpx/ >>>>>>>>>>> >>>>>>>>>>> 2015-03-18 Ilya Enkovich >>>>>>>>>>> >>>>>>>>>>> PR driver/65444 >>>>>>>>>>> * configure.ac: Add check for '-z bndplt' support >>>>>>>>>>> by linker. Add link_mpx output variable. >>>>>>>>>>> * libmpx.spec.in (link_mpx): New. >>>>>>>>>>> * configure: Regenerate. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> diff --git a/gcc/config/i386/linux-common.h b/gcc/config/i386/linux-common.h >>>>>>>>>>> index 9c6560b..dd79ec6 100644 >>>>>>>>>>> --- a/gcc/config/i386/linux-common.h >>>>>>>>>>> +++ b/gcc/config/i386/linux-common.h >>>>>>>>>>> @@ -59,6 +59,11 @@ along with GCC; see the file COPYING3. If not see >>>>>>>>>>> %:include(libmpx.spec)%(link_libmpx)" >>>>>>>>>>> #endif >>>>>>>>>>> >>>>>>>>>>> +#ifndef MPX_SPEC >>>>>>>>>>> +#define MPX_SPEC "\ >>>>>>>>>>> + %{mmpx:%{fcheck-pointer-bounds:%{!static:%:include(libmpx.spec)%(link_mpx)}}}" >>>>>>>>>>> +#endif >>>>>>>>>>> + >>>>>>>>>>> #ifndef LIBMPX_SPEC >>>>>>>>>>> #if defined(HAVE_LD_STATIC_DYNAMIC) >>>>>>>>>>> #define LIBMPX_SPEC "\ >>>>>>>>>>> @@ -89,5 +94,5 @@ along with GCC; see the file COPYING3. If not see >>>>>>>>>>> >>>>>>>>>>> #ifndef CHKP_SPEC >>>>>>>>>>> #define CHKP_SPEC "\ >>>>>>>>>>> -%{!nostdlib:%{!nodefaultlibs:" LIBMPX_SPEC LIBMPXWRAPPERS_SPEC "}}" >>>>>>>>>>> +%{!nostdlib:%{!nodefaultlibs:" LIBMPX_SPEC LIBMPXWRAPPERS_SPEC "}}" MPX_SPEC >>>>>>>>>>> #endif >>>>>>>>>>> diff --git a/libmpx/configure.ac b/libmpx/configure.ac >>>>>>>>>>> index fe0d3f2..3f8b50f 100644 >>>>>>>>>>> --- a/libmpx/configure.ac >>>>>>>>>>> +++ b/libmpx/configure.ac >>>>>>>>>>> @@ -40,7 +40,18 @@ AC_MSG_RESULT($LIBMPX_SUPPORTED) >>>>>>>>>>> AM_CONDITIONAL(LIBMPX_SUPPORTED, [test "x$LIBMPX_SUPPORTED" = "xyes"]) >>>>>>>>>>> >>>>>>>>>>> link_libmpx="-lpthread" >>>>>>>>>>> +link_mpx="" >>>>>>>>>>> +AC_MSG_CHECKING([whether ld accepts -z bndplt]) >>>>>>>>>>> +echo "int main() {};" > conftest.c >>>>>>>>>>> +if AC_TRY_COMMAND([${CC} ${CFLAGS} -Wl,-z,bndplt -o conftest conftest.c 1>&AS_MESSAGE_LOG_FD]) >>>>>>>>>>> +then >>>>>>>>>>> + AC_MSG_RESULT([yes]) >>>>>>>>>>> + link_mpx="$link_mpx -z bndplt" >>>>>>>>>>> +else >>>>>>>>>>> + AC_MSG_RESULT([no]) >>>>>>>>>>> +fi >>>>>>>>>>> AC_SUBST(link_libmpx) >>>>>>>>>>> +AC_SUBST(link_mpx) >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Without -z bndplt, MPX won't work correctly. We should always pass -z bndplt >>>>>>>>>> to linker. If linker doesn't support it, ld will issue a warning, not >>>>>>>>>> error and users >>>>>>>>>> will know their linker is too old. When they update linker, they don't have to >>>>>>>>>> rebuild GCC. >>>>>>>>> >>>>>>>>> If ld issues a warning instead of an error, then configure test passes >>>>>>>>> and we pass '-z bndplt' to linker. >>>>>>>>> >>>>>>>> >>>>>>>> Can you verify it with an older linker? The unknown XXX in -z XXX is always >>>>>>>> warned and ignored in Linux linker. If testing it on Linux always passes, >>>>>>>> it is useless. >>>>>>> >>>>>>> Old ld issues a warning: >>>>>>> >>>>>>> ld: warning: -z bndplt ignored. >>>>>> >>>>>> Does configure test pass? >>>>>> >>>>>>> But gold issues an error: >>>>>>> >>>>>>> ld.gold: bndplt: unknown -z option >>>>>>> ld.gold: use the --help option for usage information >>>>>> >>>>>> If gold is used, MPX won't work. What should we do here? >>>>>> Should we hardcode -fuse-ld=bfd for MPX? >>>>> >>>>> Is MPX disabled when the host linker is gold and gld isn't available? >>>> >>>> No. You may use MPX with gold and old ld but you would loose passed >>>> bounds when make a call via plt. >>>> >>> >>> If gold is default linker, the configure test will fail and we never pass >>> -z bndplt to linker even if ld.bfd is available and ld.gold is fixed later. >>> I'd rather always pass -z bndplt to ld. >> >> If gold is used and it doesn't support '-z bndplt' then it doesn't >> mean user can't use MPX. > > They can use -fuse-ld=bfd to select bfd linker if gold fails to generate > proper MPX binary. Which is a weird thing to do just to have a warning instead of an error. You don't guarantee MPX PLT generation by always passing '-z bndplt' but remove an opportunity to use gold at all. With current check you may use any linker and manually provide additional options if you want to. Ilya > > > -- > H.J.