From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-x533.google.com (mail-pg1-x533.google.com [IPv6:2607:f8b0:4864:20::533]) by sourceware.org (Postfix) with ESMTPS id 0BBEA3851C16 for ; Wed, 6 Jan 2021 00:51:06 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 0BBEA3851C16 Received: by mail-pg1-x533.google.com with SMTP id i5so1060379pgo.1 for ; Tue, 05 Jan 2021 16:51:06 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=FQa4ljXPGHl5PNTN6r12lK+eohtHXwKsSXK9H3+6rQM=; b=mLH/QhmBaxC+8iegDPvqktXKznrsDThEyrcA+cV9qoO0gl2xIR3qGG1fDIKErFQUlW 3S9TWMblIBxQInzaJWFsVX1W2oufs9izGfEODMs5uEN76Sli4VB5QL333tz+pV8Y19HH L0XbUOpYYZvPPE8+pAkO+1tQw+gcyCP+cFvi3SkuPEWctYCobm8bkFt13XAo6Idmy/EX tf+whv5d1/xylf/2qjKQ2YDJ1n5vZj/VROWKP9A1+jpcja7U9b8Cr9tsPTmI0esHIf1k 4OINJML9JZEwD4LnVA5p3YZghhpVPlQqp2cE1N07CtrJIewT4E/JSpDdonKQ6WBg6FRD 1Ong== X-Gm-Message-State: AOAM532GgWYlvYRo8mRCy8LeE4i6/OYIK/ijCnBltWEBBpucZ6BQbjcg jUEP26p3QSH6W9wh6qyyFbADxAQ7lQjeo//sT++NAw== X-Google-Smtp-Source: ABdhPJxedfE6r7pq555QD4cHw+ILBEiH4UwRiYYVgqG7QR7OIs+Wkhu1KcqG+Z3OdC8m0rXPXkdgKMXYGozFS1j9vJU= X-Received: by 2002:a62:61c5:0:b029:1a9:5a82:4227 with SMTP id v188-20020a6261c50000b02901a95a824227mr1443216pfb.61.1609894264989; Tue, 05 Jan 2021 16:51:04 -0800 (PST) MIME-Version: 1.0 References: <20201228194855.510315-1-maskray@google.com> <20201228214541.phbfjgv2ft3mgikj@google.com> In-Reply-To: From: =?UTF-8?B?RsSBbmctcnXDrCBTw7JuZw==?= Date: Tue, 5 Jan 2021 16:50:53 -0800 Message-ID: Subject: Re: [PATCH 0/3] Make glibc build with LLD To: "H.J. Lu" Cc: GNU C Library Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-18.7 required=5.0 tests=BAYES_00, DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, ENV_AND_HDR_SPF_MATCH, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, USER_IN_DEF_DKIM_WL, USER_IN_DEF_SPF_WL 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-List-Received-Date: Wed, 06 Jan 2021 00:51:08 -0000 On Tue, Jan 5, 2021 at 3:52 PM H.J. Lu wrote: > > On Tue, Jan 5, 2021 at 3:41 PM F=C4=81ng-ru=C3=AC S=C3=B2ng wrote: > > > > On Tue, Jan 5, 2021 at 3:34 PM H.J. Lu wrote: > > > > > > On Tue, Jan 5, 2021 at 3:03 PM F=C4=81ng-ru=C3=AC S=C3=B2ng wrote: > > > > > > > > On Mon, Dec 28, 2020 at 2:54 PM H.J. Lu wrote= : > > > > > > > > > > On Mon, Dec 28, 2020 at 1:49 PM H.J. Lu wro= te: > > > > > > > > > > > > On Mon, Dec 28, 2020 at 1:45 PM Fangrui Song wrote: > > > > > > > > > > > > > > On 2020-12-28, H.J. Lu wrote: > > > > > > > >On Mon, Dec 28, 2020 at 11:49 AM Fangrui Song via Libc-alpha > > > > > > > > wrote: > > > > > > > >> > > > > > > > >> I sent the first two in April. Resending in a patch series= to be > > > > > > > >> clearer. > > > > > > > >> > > > > > > > >> install: Replace scripts/output-format.sed with objdump = -f > > > > > > > >> > > > > > > > >> replaced https://sourceware.org/pipermail/libc-alpha/2020-= April/112733.html > > > > > > > >> by leveraging objdump -f. > > > > > > > >> > > > > > > > >> With this patch series (available in https://sourceware.or= g/git/?p=3Dglibc.git;a=3Dshortlog;h=3Drefs/heads/maskray/lld), > > > > > > > >> `make` with ld pointing to ld.lld (LLVM linker) works. > > > > > > > > > > > > > > > >I tried your branch with "LLD 11.0.0 (compatible with GNU li= nkers)" on > > > > > > > >Fedora 33/x86-64, > > > > > > > >"make check" generated: > > > > > > > > > > > > > > > >make[4]: *** [../Makerules:767: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-tlsmod2.so] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Makerules:767: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-tlsmod4.so] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Makerules:767: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-absolute-sym-lib.so] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Makerules:767: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-absolute-zero-lib.so] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Makerules:767: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-tlsmod6.so] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Makerules:767: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-tlsmod5.so] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Rules:226: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-audit16] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Rules:226: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-audit14] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Rules:226: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-audit15] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Rules:226: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/tst-tls1] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Rules:226: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/ifuncmain5] > > > > > > > >Error 1 > > > > > > > >make[4]: *** [../Rules:226: > > > > > > > >/export/users/hjl/build/gnu/tools-build/glibc-gitlab-lld/bui= ld-x86_64-linux/elf/ifuncmain1] > > > > > > > >Error 1 > > > > > > > >make[3]: *** [Makefile:479: elf/tests] Error 2 > > > > > > > > > > > > > > > >with error messages, like > > > > > > > > > > > > > > > >ld: error: /export/users/hjl/build/gnu/tools-build/glibc-git= lab-lld/build-x86_64-linux/elf/tst-tlsmod2.os > > > > > > > >has an STT_TLS symbol but doesn't have an SHF_TLS section > > > > > > > >ld: error: /export/users/hjl/build/gnu/tools-build/glibc-git= lab-lld/build-x86_64-linux/elf/tst-tlsmod4.os > > > > > > > >has an STT_TLS symbol but doesn't have an SHF_TLS section > > > > > > > > > > > > > > tst-tls* tests appear to be similar to .tls_common which look= s very > > > > > > > obsoleted and not supported by Clang. I don't think ifuncmain= * or > > > > > > > tst-audit* matters for typical usage (most users) but I can t= ake a look. > > > > > > > > > > > > "make check" should be clean on Fedora 33/x86-64. > > > > > > > > > > Because this lld error, "make check" didn't report test summary: > > > > > > > > > > Summary of test results: > > > > > 4322 PASS > > > > > 8 UNSUPPORTED > > > > > 13 XFAIL > > > > > 6 XPASS > > > > > > > > > > > > >When glibc is configured with --enable-static-pie, I got > > > > > > > > > > > > > > > >[hjl@gnu-skx-1 build-x86_64-linux]$ ./elf/ldconfig > > > > > > > >Segmentation fault (core dumped) > > > > > > > >[hjl@gnu-skx-1 build-x86_64-linux]$ > > > > > > > > > > > > > > > >You need to fix lld first and give the working lld a proper = version so that > > > > > > > >configure can check it. > > > > > > > > > > > > > > I cherry picked "Make _dl_relocate_static_pie return an int i= ndicating whether it applied relocs." > > > > > > > in google/grte/v5-2.27/master, which has fixed the issue. > > > > > > > > > > > > Why isn't it needed for ld? > > > > > > > > > > > > > > > > Also re-order your patches to place the enabling lld patch the la= st so that any > > > > > commits can build a working glibc. > > > > > > > > > > Thanks. > > > > > > > > > > -- > > > > > H.J. > > > > > > > > Without "configure: Allow LD to be LLD 9.0.0 or above", configure > > > > rejects LLD at configure time and the other commits cannot be teste= d > > > > at all... > > > > > > > > The other commits are general improvement and useful on their own, = and > > > > they are independent and can be merged separately. > > > > > > > > As I mentioned in the other reply, LLD does not want to special cas= e > > > > the definition of __rela_iplt_start depending on -no-pie (available= in > > > > gold and LLD, not available in GNU ld yet) ; -pie/-shared... > > > > The TLS common issues are obsoleted features that do not make sense= nowadays. > > > > Any case, the LLD produced executables are functional. > > > > > > The code in question is > > > > > > static void > > > apply_irel (void) > > > { > > > # ifdef IREL > > > /* We use weak references for these so that we'll still work with a= linker > > > that doesn't define them. Such a linker doesn't support IFUNC a= t all > > > and so uses won't work, but a statically-linked program that doe= sn't > > > use any IFUNC symbols won't have a problem. */ > > > extern const IREL_T IPLT_START[] __attribute__ ((weak)); > > > extern const IREL_T IPLT_END[] __attribute__ ((weak)); > > > for (const IREL_T *ipltent =3D IPLT_START; ipltent < IPLT_END; ++ip= ltent) > > > IREL (ipltent); > > > # endif > > > } > > > > > > Since IPLT_START and IPLT_END are undefined, linker should set > > > them to zero and the loop should be skipped. Why doesn't LLD do > > > that? > > > > > > > > > -- > > > H.J. > > > > LLD defines __rela_iplt_start/__rela_iplt_end if (1) __rela_iplt_start > > exists and is not defined (2) not -r (3) no .interp > > > > LLD defines __rela_iplt_start regardless of -no-pie/-pie. This > > behavior makes sense to me. > > GNU ld and gold seem to only define __rela_iplt_start in -no-pie mode. > > It is an lld bug: > > https://bugs.llvm.org/show_bug.cgi?id=3D48674 > > -- > H.J. I don't consider https://bugs.llvm.org/show_bug.cgi?id=3D48674 an LLD bug, so we have disagreement. __rela_iplt_start/__rela_iplt_end is a contract between the link editor and the dynamic loader/libc. For the perspective of a good design, I don't think it is necessary making "whether to define __rela_iplt_start" different for ld -no-pie (GNU ld does not have -no-pie currently, but gold and LLD do) and ld -pie. rtld/libc can just figure out whether it is -static-pie (since a different crt1 rcrt1.o is used) and don't reference __rela_iplt_start in that case. If this difference is dropped (by taking the glibc patch "Make _dl_relocate_static_pie return an int indicating whether it applied relocs."), diff -u =3D(ld.bfd --verbose) =3D(ld.bfd -pie --verbose) can have no difference other than the start address: __executable_start.