From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x72a.google.com (mail-qk1-x72a.google.com [IPv6:2607:f8b0:4864:20::72a]) by sourceware.org (Postfix) with ESMTPS id 5999F38618B8 for ; Fri, 29 Jan 2021 18:05:02 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 5999F38618B8 Received: by mail-qk1-x72a.google.com with SMTP id k193so9583776qke.6 for ; Fri, 29 Jan 2021 10:05:02 -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=pSzkG4BABiHGYAtT+vnm0azsqM5tKvo8Q999i8A2hew=; b=VG7ig5eATohRQEL0GuAUpu0L52jBxb0dp5PXjBLuVuilVFbDiDVDJKmeKB0+YUUisn 4EeMO1Q85J/1QEpca3/6QOud9ObZ42M9/n6txmzzv+u41xVVN8Zcu+StlUQqxABjrN9o V56Tzq+iQZ0OlSFAOWwdrtpTFNsuP/iQOiA1QImYAd+JtsXsIZsD9IAuFrQU+VUe3qJU D3q3w+gvZmYmHG4Yi37qQLh23FHfIZ/Stmmu7pD1S2wrbqiC6leXGqcDvfLV5StFxyY3 PvRfidztGUK09kp6iTt48mIQEEP4g6ClNs1RhameSoGRG9EU9KD3+a6F+muI38ZsWwJi Z3XQ== X-Gm-Message-State: AOAM531GP6919kVlv3tSgazqeQqacWm29cFTWU9JcXuNNtbSUhjV7EWS 0wvENC9jnu8Jomk3J0FXnGz1G2sHtX40eg== X-Google-Smtp-Source: ABdhPJw4WpTTB/is0IsNhE27BBGua7JqS2IfRFwXLQ53ZmpBYVgahlD6+PGxDdahCMKVwFqYJvGObA== X-Received: by 2002:a37:4497:: with SMTP id r145mr5346283qka.241.1611943501388; Fri, 29 Jan 2021 10:05:01 -0800 (PST) Received: from [192.168.1.4] ([177.194.48.209]) by smtp.googlemail.com with ESMTPSA id h22sm1742392qtp.50.2021.01.29.10.04.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 Jan 2021 10:05:00 -0800 (PST) To: "H.J. Lu" Cc: =?UTF-8?B?RsSBbmctcnXDrCBTw7JuZw==?= , Florian Weimer , GNU C Library References: <20201228194855.510315-1-maskray@google.com> <20201228194855.510315-3-maskray@google.com> <4c4b4d3b-6265-7575-d1e8-879471121511@linaro.org> 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 2/3] elf: Replace a --defsym trick with an object file to be compatible with lld Message-ID: <56de4bc0-05b1-49f9-32ce-b9eab7fdc510@linaro.org> Date: Fri, 29 Jan 2021 15:04:57 -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: 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: Fri, 29 Jan 2021 18:05:05 -0000 On 29/01/2021 12:29, H.J. Lu wrote: > On Fri, Jan 29, 2021 at 7:26 AM Adhemerval Zanella via Libc-alpha > wrote: >> >> >> >> On 27/01/2021 22:03, Fāng-ruì Sòng via Libc-alpha wrote: >>> On Wed, Jan 20, 2021 at 10:51 AM Fāng-ruì Sòng wrote: >>>> >>>> On Tue, Jan 19, 2021 at 4:31 AM H.J. Lu wrote: >>>>> >>>>> On Tue, Jan 19, 2021 at 12:50 AM Fāng-ruì Sòng wrote: >>>>>> >>>>>> On Mon, Jan 18, 2021 at 4:04 PM H.J. Lu wrote: >>>>>>> >>>>>>> On Mon, Dec 28, 2020 at 11:50 AM Fangrui Song via Libc-alpha >>>>>>> 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. >>>>>>>> >>>>>>> >>>>>>> This is irrelevant since --defsym was used to create a temporary file which was >>>>>>> removed immediately after it was created: >>>>>>> >>>>>>> /usr/bin/gcc -nostdlib -nostartfiles -r -o >>>>>>> /export/users/hjl/build/gnu/tools-build/glibc-gitlab/build-x86_64-linux/elf/librtld.map.o >>>>>>> -Wl,--defsym=calloc=0 -Wl,--defsym=free=0 -Wl,--defsym=malloc=0 >>>>>>> -Wl,--defsym=realloc=0 -Wl,--defsym=__stack_chk_fail=0 >>>>>>> -Wl,--defsym=__stack_chk_fail_local=0 \ >>>>>>> '-Wl,-(' >>>>>>> /export/users/hjl/build/gnu/tools-build/glibc-gitlab/build-x86_64-linux/elf/dl-allobjs.os >>>>>>> /export/users/hjl/build/gnu/tools-build/glibc-gitlab/build-x86_64-linux/libc_pic.a >>>>>>> -lgcc '-Wl,-)' -Wl,-Map,/export/users/hjl/build/gnu/tools-build/glibc-gitlab/build-x86_64-linux/elf/librtld.mapT >>>>>>> rm -f /export/users/hjl/build/gnu/tools-build/glibc-gitlab/build-x86_64-linux/elf/librtld.map.o >>>>>>> mv -f /export/users/hjl/build/gnu/tools-build/glibc-gitlab/build-x86_64-linux/elf/librtld.mapT >>>>>>> /export/users/hjl/build/gnu/tools-build/glibc-gitlab/build-x86_64-linux/elf/librtld.map >>>>>>> >>>>>>>> --- >>>>>>>> elf/Makefile | 11 ++++------- >>>>>>>> 1 file changed, 4 insertions(+), 7 deletions(-) >>>>>>>> >>>>>>>> diff --git a/elf/Makefile b/elf/Makefile >>>>>>>> index 0b4d78c874..299bf24b49 100644 >>>>>>>> --- a/elf/Makefile >>>>>>>> +++ b/elf/Makefile >>>>>>>> @@ -524,10 +524,6 @@ 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. >>>>>>>> @@ -536,9 +532,10 @@ 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 $@.o >>>>>>>> + echo '$(patsubst %,.globl %;,$(rtld-stubbed-symbols)) $(patsubst %,%:,$(rtld-stubbed-symbols))' | \ >>>>>>>> + $(CC) -o $@T.o $(ASFLAGS) -c -x assembler - >>>>>>> >>>>>>> Please generate >>>>>>> >>>>>>> .globl symbol; >>>>>>> symbol = 0; >>>>>>> >>>>>>> to make it closer to -Wl,--defsym=symbol=0. >>>>>> >>>>>> If symbol: and symbol = 0; work, isn't symbol: slightly better because >>>>>> it looks more normal? >>>>>> Or is the intention here using SHN_ABS to make it clear these symbols >>>>>> are special? >>>>> >>>>> Generate machine independent assembly codes is tricky. We should >>>>> make before and after the change as close as possible to avoid ANY >>>>> surprises. BTW, you need to check HAVE_ASM_SET_DIRECTIVE >>>>> to decide using ".set" vs "=". >>>>> >>>>> -- >>>>> H.J. >>>> >>>> Thanks for the tip. In this case I think the patch as is (sticking >>>> with `foo:`, don't use `foo = 0` or set) is better. >>>> foo: works everywhere. >>> >>> Ping. I think the patch as-is is better than the alternative approach >>> using either `=` or `.set`. >> >> The patch breaks both arc-linux-gnuhf and hppa-linux-gnu with recent >> ld.bfd 2.26, as below. >> >> We will need to sort these out. The issue was in fact that hppa and arc uses no default asm line separators (represented by ASM_LINE_SEP within code): hppa uses '!' while arc '`'. By replacing echo with printf and issuing a new line explicit I see that all targets build: --- diff --git a/elf/Makefile b/elf/Makefile index 5d666b1b0c..e5c04f682c 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)) $(patsubst %,% = 0;\n,$(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.