From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qv1-xf2d.google.com (mail-qv1-xf2d.google.com [IPv6:2607:f8b0:4864:20::f2d]) by sourceware.org (Postfix) with ESMTPS id 663703836C2F for ; Mon, 1 Feb 2021 13:19:18 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 663703836C2F Received: by mail-qv1-xf2d.google.com with SMTP id w11so8028295qvz.12 for ; Mon, 01 Feb 2021 05:19:18 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:autocrypt:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=EG9krrOvhG/4RYt+uLe98QY4NYkqeVdh60ckGzro458=; b=OdF4H5TNwyG359TyPNzssTNqU03BCkqpdlb1GqgGVZxLC+tgXutmEPUUPlhmizfS0x veu6qKfIMcR5oVSG7pPdZVcpYOtSHydAnWz17H82hfjSWasUKWjl3uRmx9BWP2klWvPl s12Ic562trfhvmIfVT+iRVpcfA3d5cLJjfsBHXJdt6F73nDrQV+FaCaQpexwEJLuADuI ufrsXy9lfLPo8QUK5zQFfBGZl5XNRbZUHSzYDRdcGfOBJ8B2IQMXy8TCPIolnzpVYDUf UXLTXTsl/rxtoAiOm+jmL5QWGA7fZO++bRUFaC1i7ICLJ6PLIoktpSHUfN5eNgroWx+u xUkA== X-Gm-Message-State: AOAM532Omv/OE7dZhMWw19g46KIfg2xgWl4rCjF0i6n44jGDUBbGCbEb lpfsRtJIGpZIxcBuaqW0LGByKUDhPsBaEg== X-Google-Smtp-Source: ABdhPJyUcoB7GOJTf9NcUsNA69Grxzs0ns+1zcJHP+DtaH75YQc+dZWok2s4SFvrN1jpGJFKC4OOXQ== X-Received: by 2002:a05:6214:446:: with SMTP id cc6mr4779297qvb.31.1612185558004; Mon, 01 Feb 2021 05:19:18 -0800 (PST) Received: from [192.168.1.4] ([177.194.48.209]) by smtp.googlemail.com with ESMTPSA id 12sm13430191qkg.39.2021.02.01.05.19.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Feb 2021 05:19:17 -0800 (PST) To: Fangrui Song , libc-alpha@sourceware.org References: <56de4bc0-05b1-49f9-32ce-b9eab7fdc510@linaro.org> <20210129192824.804615-1-maskray@google.com> From: Adhemerval Zanella Autocrypt: addr=adhemerval.zanella@linaro.org; prefer-encrypt=mutual; keydata= mQINBFcVGkoBEADiQU2x/cBBmAVf5C2d1xgz6zCnlCefbqaflUBw4hB/bEME40QsrVzWZ5Nq 8kxkEczZzAOKkkvv4pRVLlLn/zDtFXhlcvQRJ3yFMGqzBjofucOrmdYkOGo0uCaoJKPT186L NWp53SACXguFJpnw4ODI64ziInzXQs/rUJqrFoVIlrPDmNv/LUv1OVPKz20ETjgfpg8MNwG6 iMizMefCl+RbtXbIEZ3TE/IaDT/jcOirjv96lBKrc/pAL0h/O71Kwbbp43fimW80GhjiaN2y WGByepnkAVP7FyNarhdDpJhoDmUk9yfwNuIuESaCQtfd3vgKKuo6grcKZ8bHy7IXX1XJj2X/ BgRVhVgMHAnDPFIkXtP+SiarkUaLjGzCz7XkUn4XAGDskBNfbizFqYUQCaL2FdbW3DeZqNIa nSzKAZK7Dm9+0VVSRZXP89w71Y7JUV56xL/PlOE+YKKFdEw+gQjQi0e+DZILAtFjJLoCrkEX w4LluMhYX/X8XP6/C3xW0yOZhvHYyn72sV4yJ1uyc/qz3OY32CRy+bwPzAMAkhdwcORA3JPb kPTlimhQqVgvca8m+MQ/JFZ6D+K7QPyvEv7bQ7M+IzFmTkOCwCJ3xqOD6GjX3aphk8Sr0dq3 4Awlf5xFDAG8dn8Uuutb7naGBd/fEv6t8dfkNyzj6yvc4jpVxwARAQABtElBZGhlbWVydmFs IFphbmVsbGEgTmV0dG8gKExpbmFybyBWUE4gS2V5KSA8YWRoZW1lcnZhbC56YW5lbGxhQGxp bmFyby5vcmc+iQI3BBMBCAAhBQJXFRpKAhsDBQsJCAcDBRUKCQgLBRYCAwEAAh4BAheAAAoJ EKqx7BSnlIjv0e8P/1YOYoNkvJ+AJcNUaM5a2SA9oAKjSJ/M/EN4Id5Ow41ZJS4lUA0apSXW NjQg3VeVc2RiHab2LIB4MxdJhaWTuzfLkYnBeoy4u6njYcaoSwf3g9dSsvsl3mhtuzm6aXFH /Qsauav77enJh99tI4T+58rp0EuLhDsQbnBic/ukYNv7sQV8dy9KxA54yLnYUFqH6pfH8Lly sTVAMyi5Fg5O5/hVV+Z0Kpr+ZocC1YFJkTsNLAW5EIYSP9ftniqaVsim7MNmodv/zqK0IyDB GLLH1kjhvb5+6ySGlWbMTomt/or/uvMgulz0bRS+LUyOmlfXDdT+t38VPKBBVwFMarNuREU2 69M3a3jdTfScboDd2ck1u7l+QbaGoHZQ8ZNUrzgObltjohiIsazqkgYDQzXIMrD9H19E+8fw kCNUlXxjEgH/Kg8DlpoYJXSJCX0fjMWfXywL6ZXc2xyG/hbl5hvsLNmqDpLpc1CfKcA0BkK+ k8R57fr91mTCppSwwKJYO9T+8J+o4ho/CJnK/jBy1pWKMYJPvvrpdBCWq3MfzVpXYdahRKHI ypk8m4QlRlbOXWJ3TDd/SKNfSSrWgwRSg7XCjSlR7PNzNFXTULLB34sZhjrN6Q8NQZsZnMNs TX8nlGOVrKolnQPjKCLwCyu8PhllU8OwbSMKskcD1PSkG6h3r0AquQINBFcVGkoBEACgAdbR Ck+fsfOVwT8zowMiL3l9a2DP3Eeak23ifdZG+8Avb/SImpv0UMSbRfnw/N81IWwlbjkjbGTu oT37iZHLRwYUFmA8fZX0wNDNKQUUTjN6XalJmvhdz9l71H3WnE0wneEM5ahu5V1L1utUWTyh VUwzX1lwJeV3vyrNgI1kYOaeuNVvq7npNR6t6XxEpqPsNc6O77I12XELic2+36YibyqlTJIQ V1SZEbIy26AbC2zH9WqaKyGyQnr/IPbTJ2Lv0dM3RaXoVf+CeK7gB2B+w1hZummD21c1Laua +VIMPCUQ+EM8W9EtX+0iJXxI+wsztLT6vltQcm+5Q7tY+HFUucizJkAOAz98YFucwKefbkTp eKvCfCwiM1bGatZEFFKIlvJ2QNMQNiUrqJBlW9nZp/k7pbG3oStOjvawD9ZbP9e0fnlWJIsj 6c7pX354Yi7kxIk/6gREidHLLqEb/otuwt1aoMPg97iUgDV5mlNef77lWE8vxmlY0FBWIXuZ yv0XYxf1WF6dRizwFFbxvUZzIJp3spAao7jLsQj1DbD2s5+S1BW09A0mI/1DjB6EhNN+4bDB SJCOv/ReK3tFJXuj/HbyDrOdoMt8aIFbe7YFLEExHpSk+HgN05Lg5TyTro8oW7TSMTk+8a5M kzaH4UGXTTBDP/g5cfL3RFPl79ubXwARAQABiQIfBBgBCAAJBQJXFRpKAhsMAAoJEKqx7BSn lIjvI/8P/jg0jl4Tbvg3B5kT6PxJOXHYu9OoyaHLcay6Cd+ZrOd1VQQCbOcgLFbf4Yr+rE9l mYsY67AUgq2QKmVVbn9pjvGsEaz8UmfDnz5epUhDxC6yRRvY4hreMXZhPZ1pbMa6A0a/WOSt AgFj5V6Z4dXGTM/lNManr0HjXxbUYv2WfbNt3/07Db9T+GZkpUotC6iknsTA4rJi6u2ls0W9 1UIvW4o01vb4nZRCj4rni0g6eWoQCGoVDk/xFfy7ZliR5B+3Z3EWRJcQskip/QAHjbLa3pml xAZ484fVxgeESOoaeC9TiBIp0NfH8akWOI0HpBCiBD5xaCTvR7ujUWMvhsX2n881r/hNlR9g fcE6q00qHSPAEgGr1bnFv74/1vbKtjeXLCcRKk3Ulw0bY1OoDxWQr86T2fZGJ/HIZuVVBf3+ gaYJF92GXFynHnea14nFFuFgOni0Mi1zDxYH/8yGGBXvo14KWd8JOW0NJPaCDFJkdS5hu0VY 7vJwKcyHJGxsCLU+Et0mryX8qZwqibJIzu7kUJQdQDljbRPDFd/xmGUFCQiQAncSilYOcxNU EMVCXPAQTteqkvA+gNqSaK1NM9tY0eQ4iJpo+aoX8HAcn4sZzt2pfUB9vQMTBJ2d4+m/qO6+ cFTAceXmIoFsN8+gFN3i8Is3u12u8xGudcBPvpoy4OoG Subject: Re: [PATCH v2] elf: Replace a --defsym trick with an object file to be compatible with LLD Message-ID: <2d93f58d-64d2-cc71-1909-e08d486b2de8@linaro.org> Date: Mon, 1 Feb 2021 10:19:14 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210129192824.804615-1-maskray@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-13.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, 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-List-Received-Date: Mon, 01 Feb 2021 13:19:20 -0000 On 29/01/2021 16:28, Fangrui Song wrote: > The existing code specifies -Wl,--defsym=malloc=0 and other malloc.os > definitions before libc_pic.a so that libc_pic.a(malloc.os) is not > fetched. This trick is used to avoid multiple definition errors which > would happen as a chain result: > > dl-allobjs.os has an undefined __libc_scratch_buffer_set_array_size > __libc_scratch_buffer_set_array_size fetches libc_pic.a(scratch_buffer_set_array_size.os) > libc_pic.a(scratch_buffer_set_array_size.os) has an undefined free > free fetches libc_pic.a(malloc.os) > libc_pic.a(malloc.os) has an undefined __libc_message > __libc_message fetches libc_pic.a(libc_fatal.os) > > libc_fatal.os will cause a multiple definition error (__GI___libc_fatal) > >>> defined at dl-fxstatat64.c > >>> /tmp/p/glibc/Release/elf/dl-allobjs.os:(__GI___libc_fatal) > >>> defined at libc_fatal.c > >>> libc_fatal.os:(.text+0x240) in archive /tmp/p/glibc/Release/libc_pic.a > > LLD processes --defsym after all input files, so this trick does not > suppress multiple definition errors with LLD. Split the step into two > and use an object file to make the intention more obvious and make LLD > work. > > This is conceptually more appropriate because --defsym defines a SHN_ABS > symbol while a normal definition is relative to the image base. > > See https://sourceware.org/pipermail/libc-alpha/2020-March/111910.html > for discussions about the --defsym semantics. > > This commit is available on https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/maskray/lld > --- > elf/Makefile | 11 ++++------- > 1 file changed, 4 insertions(+), 7 deletions(-) > > diff --git a/elf/Makefile b/elf/Makefile > index 5d666b1b0c..03e4034cc7 100644 > --- a/elf/Makefile > +++ b/elf/Makefile > @@ -526,10 +526,6 @@ rtld-stubbed-symbols = \ > malloc \ > realloc \ > > -# The GCC arguments that implement $(rtld-stubbed-symbols). > -rtld-stubbed-symbols-args = \ > - $(patsubst %,-Wl$(comma)--defsym=%=0, $(rtld-stubbed-symbols)) > - > ifeq ($(have-ssp),yes) > # rtld is not built with the stack protector, so these references will > # go away in the rebuilds. > @@ -538,9 +534,10 @@ endif > > $(objpfx)librtld.map: $(objpfx)dl-allobjs.os $(common-objpfx)libc_pic.a > @-rm -f $@T > - $(reloc-link) -o $@.o $(rtld-stubbed-symbols-args) \ > - '-Wl,-(' $^ -lgcc '-Wl,-)' -Wl,-Map,$@T > - rm -f $@.o > + printf '$(patsubst %,.globl %\n,$(rtld-stubbed-symbols)) $(patsubst %,%:\n,$(rtld-stubbed-symbols))' | \ > + $(CC) -o $@T.o $(ASFLAGS) -c -x assembler - > + $(reloc-link) -o $@.o $@T.o '-Wl,-(' $^ -lgcc '-Wl,-)' -Wl,-Map,$@T > + rm -f %@T.o $@.o > mv -f $@T $@ > > # For lld, skip preceding addresses and values before matching the archive and the member. Looks ok, I haven't see any build issue. The '=' seems unrequired, although '=' seems to work on all supported architectures (HAVE_ASM_SET_DIRECTIVE does not seem to be necessary to handle here). It is ok for 2.34 from my side. H.J, do you see any issues of not setting the symbol to '0'?