From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id B4DC03858C2C for ; Thu, 28 Apr 2022 17:24:39 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org B4DC03858C2C Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-325-UWtl2MBeNjaFLvClaFl3kg-1; Thu, 28 Apr 2022 13:24:38 -0400 X-MC-Unique: UWtl2MBeNjaFLvClaFl3kg-1 Received: by mail-qv1-f71.google.com with SMTP id dv6-20020ad44ee6000000b0045642576917so4192841qvb.17 for ; Thu, 28 Apr 2022 10:24:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:references:from:organization:in-reply-to :content-transfer-encoding; bh=ldNsfpWTdDpeC1Zb4cYQszzTTovRthxWyK28zeggaQ8=; b=RSEKWrhAEDrGqgib/QrCq7lY0oTR7CJfOSBMSQdoD3m9cQIfCd5EfDyT8v/rKSVBAM U0OGqBFFTlOmIzhTxCWjwla/NjCIgdu94rR6GcfV/Y3TqK28BX5X6WewQZk/MMQoliLM ZKh5GDBwzfK8Qil6P6HzupqY6Bqc/EzU9F/8n4znmOLsp5+gm8ifDILi1asB+TlyVJ+q u6EMC5RcSJKpg/hNmmi4S7Xze997vFPZVVHDVfr8grFbW7qc9ktxPo6nQSi8e0qoQH2e FEpNL1aO108EbqeIoVH2f1fPjWzZf3q7vSRvkiHssOEvaxRfFsHtB5TaMa5qEaOkTH1V +kxA== X-Gm-Message-State: AOAM533VykHJ0yHX9ApDnAlSj7sxzkM1GhR9MlhAGV7gRGZW9D/YrskT RmqLYaZPKpzwFB2HAPXiW2e2URIUO4ZYE1y5qHyTwmwUGH8Id5NF6h5v7+WLl2SE0+In4a+WtJi aPw519kU8goO2ZJCJdLwv X-Received: by 2002:a05:6214:2626:b0:458:c61:17c8 with SMTP id gv6-20020a056214262600b004580c6117c8mr1751179qvb.2.1651166676282; Thu, 28 Apr 2022 10:24:36 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzZ6r0Rq913m4GzZ1uUSsUoEZIoXPRlGLWMjyT+xfSmfKd6Q/kLUsKRISB0ogHNCycEvJiTNA== X-Received: by 2002:a05:6214:2626:b0:458:c61:17c8 with SMTP id gv6-20020a056214262600b004580c6117c8mr1751164qvb.2.1651166675912; Thu, 28 Apr 2022 10:24:35 -0700 (PDT) Received: from [192.168.0.241] (135-23-175-80.cpe.pppoe.ca. [135.23.175.80]) by smtp.gmail.com with ESMTPSA id e13-20020a05620a12cd00b0069e908ab48dsm234899qkl.106.2022.04.28.10.24.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 Apr 2022 10:24:34 -0700 (PDT) Message-ID: <15e85a91-b6c2-0721-9f6e-bf9e1902e910@redhat.com> Date: Thu, 28 Apr 2022 13:24:33 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH] dlfcn: Implement the RTLD_DI_PHDR request type for dlinfo To: Florian Weimer , libc-alpha@sourceware.org References: <87mtgfwpqy.fsf@oldenburg.str.redhat.com> From: Carlos O'Donell Organization: Red Hat In-Reply-To: <87mtgfwpqy.fsf@oldenburg.str.redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.0 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, NICE_REPLY_A, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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: Thu, 28 Apr 2022 17:24:41 -0000 On 4/20/22 14:53, Florian Weimer via Libc-alpha wrote: > The information is theoretically available via dl_iterate_phdr as > well, but that approach is very slow if there are many shared > objects. > > Tested on i686-linux-gnu and x86_64-linux-gnu. Built with > build-many-glibcs.py. > > This patch depends on the previous dlinfo documentation patch. Pending the manual v3 and commit. LGTM. I agree that a dlinfo API for this is useful, and I saw that this helps resolve a real user request: https://sourceware.org/pipermail/libc-alpha/2022-March/137096.html Reviewed-by: Carlos O'Donell Tested-by: Carlos O'Donell > --- > dlfcn/Makefile | 4 ++ > dlfcn/dlfcn.h | 7 ++- > dlfcn/dlinfo.c | 13 ++++- > dlfcn/tst-dlinfo-phdr.c | 125 ++++++++++++++++++++++++++++++++++++++++++++++++ > manual/dynlink.texi | 15 ++++-- > 5 files changed, 159 insertions(+), 5 deletions(-) > > diff --git a/dlfcn/Makefile b/dlfcn/Makefile > index 6e0a014d99..3255ba02c5 100644 > --- a/dlfcn/Makefile > +++ b/dlfcn/Makefile > @@ -73,6 +73,10 @@ tststatic3-ENV = $(tststatic-ENV) > tststatic4-ENV = $(tststatic-ENV) > tststatic5-ENV = $(tststatic-ENV) > > +tests-internal += \ > + tst-dlinfo-phdr \ > + # tests-internal OK. > + > ifneq (,$(CXX)) > modules-names += bug-atexit3-lib > else > diff --git a/dlfcn/dlfcn.h b/dlfcn/dlfcn.h > index b5cd5c5238..a3af6051d4 100644 > --- a/dlfcn/dlfcn.h > +++ b/dlfcn/dlfcn.h > @@ -164,7 +164,12 @@ enum > segment, or if the calling thread has not allocated a block for it. */ > RTLD_DI_TLS_DATA = 10, > > - RTLD_DI_MAX = 10 > + /* Treat ARG as const ElfW(Phdr) **, and store the address of the > + program header array at that location. The dlinfo call returns > + the number of program headers in the array. */ > + RTLD_DI_PHDR = 11, > + > + RTLD_DI_MAX = 11 OK. I like that the return is the number of program headers in the array. > }; > > > diff --git a/dlfcn/dlinfo.c b/dlfcn/dlinfo.c > index fc63c02681..f64ecf59cb 100644 > --- a/dlfcn/dlinfo.c > +++ b/dlfcn/dlinfo.c > @@ -28,6 +28,10 @@ struct dlinfo_args > void *handle; > int request; > void *arg; > + > + /* This is the value that is returned from dlinfo if no error is > + signaled. */ > + int result; OK. > }; > > static void > @@ -40,6 +44,7 @@ dlinfo_doit (void *argsblock) > { > case RTLD_DI_CONFIGADDR: > default: > + args->result = -1; OK. > _dl_signal_error (0, NULL, NULL, N_("unsupported dlinfo request")); > break; > > @@ -75,6 +80,11 @@ dlinfo_doit (void *argsblock) > *(void **) args->arg = data; > break; > } > + > + case RTLD_DI_PHDR: > + *(const ElfW(Phdr) **) args->arg = l->l_phdr; > + args->result = l->l_phnum; OK. Straight forward copy of data we already have. > + break; > } > } > > @@ -82,7 +92,8 @@ static int > dlinfo_implementation (void *handle, int request, void *arg) > { > struct dlinfo_args args = { handle, request, arg }; > - return _dlerror_run (&dlinfo_doit, &args) ? -1 : 0; > + _dlerror_run (&dlinfo_doit, &args); > + return args.result; OK. We need this because result is now returned which is not just -1 or 0. > } > > #ifdef SHARED > diff --git a/dlfcn/tst-dlinfo-phdr.c b/dlfcn/tst-dlinfo-phdr.c > new file mode 100644 > index 0000000000..a15a7d48eb > --- /dev/null > +++ b/dlfcn/tst-dlinfo-phdr.c > @@ -0,0 +1,125 @@ > +/* Test for dlinfo (RTLD_DI_PHDR). OK. > + Copyright (C) 2022 Free Software Foundation, Inc. > + This file is part of the GNU C Library. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#include > +#include > +#include > +#include > +#include > +#include > + > +#include > +#include > + > +/* Used to verify that the program header array appears as expected > + among the dl_iterate_phdr callback invocations. */ > + > +struct dlip_callback_args > +{ > + struct link_map *l; /* l->l_addr is used to find the object. */ > + const ElfW(Phdr) *phdr; /* Expected program header pointed. */ > + int phnum; /* Expected program header count. */ > + bool found; /* True if l->l_addr has been found. */ > +}; > + > +static int > +dlip_callback (struct dl_phdr_info *dlpi, size_t size, void *closure) > +{ > + TEST_COMPARE (sizeof (*dlpi), size); > + struct dlip_callback_args *args = closure; > + > + if (dlpi->dlpi_addr == args->l->l_addr) > + { > + TEST_VERIFY (!args->found); > + args->found = true; > + TEST_VERIFY (args->phdr == dlpi->dlpi_phdr); > + TEST_COMPARE (args->phnum, dlpi->dlpi_phnum); > + } > + > + return 0; > +} > + > +static int > +do_test (void) > +{ > + /* Avoid a copy relocation. */ > + struct r_debug *debug = xdlsym (RTLD_DEFAULT, "_r_debug"); > + struct link_map *l = (struct link_map *) debug->r_map; OK. Using tests-internal view of struct link_map. > + TEST_VERIFY_EXIT (l != NULL); > + > + do > + { > + printf ("info: checking link map %p (%p) for \"%s\"\n", > + l, l->l_phdr, l->l_name); > + > + /* Cause dlerror () to return an error message. */ > + dlsym (RTLD_DEFAULT, "does-not-exist"); > + > + /* Use the extension that link maps are valid dlopen handles. */ > + const ElfW(Phdr) *phdr; > + int phnum = dlinfo (l, RTLD_DI_PHDR, &phdr); OK. Call dlinfo with new request. > + TEST_VERIFY (phnum >= 0); > + /* Verify that the error message has been cleared. */ > + TEST_COMPARE_STRING (dlerror (), NULL); > + > + TEST_VERIFY (phdr == l->l_phdr); > + TEST_COMPARE (phnum, l->l_phnum); OK. Compare. > + > + /* Check that we can find PT_DYNAMIC among the array. */ > + { > + bool dynamic_found = false; > + for (int i = 0; i < phnum; ++i) > + if (phdr[i].p_type == PT_DYNAMIC) > + { > + dynamic_found = true; > + TEST_COMPARE ((ElfW(Addr)) l->l_ld, l->l_addr + phdr[i].p_vaddr); OK. Compare. > + } > + TEST_VERIFY (dynamic_found); > + } > + > + /* Check that dl_iterate_phdr finds the link map with the same > + program headers. */ > + { > + struct dlip_callback_args args = > + { > + .l = l, > + .phdr = phdr, > + .phnum = phnum, > + .found = false, > + }; > + TEST_COMPARE (dl_iterate_phdr (dlip_callback, &args), 0); OK. Run comparison now with dl_iterate_phdr (after comparison via raw _r_debug values). > + TEST_VERIFY (args.found); > + } > + > + if (l->l_prev == NULL) > + { > + /* This is the executable, so the information is also > + available via getauxval. */ > + TEST_COMPARE_STRING (l->l_name, ""); > + TEST_VERIFY (phdr == (const ElfW(Phdr) *) getauxval (AT_PHDR)); > + TEST_COMPARE (phnum, getauxval (AT_PHNUM)); OK. Compare now via getauxval. > + } > + > + l = l->l_next; > + } > + while (l != NULL); > + > + return 0; > +} > + > +#include > diff --git a/manual/dynlink.texi b/manual/dynlink.texi > index 6d74fbe2ef..18f78ee002 100644 > --- a/manual/dynlink.texi > +++ b/manual/dynlink.texi > @@ -28,9 +28,9 @@ location @var{arg}, based on @var{request}. The @var{handle} argument > must be a pointer returned by @code{dlopen} or @code{dlmopen}; it must > not have been closed by @code{dlclose}. > > -On success, @code{dlinfo} returns 0. If there is an error, the function > -returns @math{-1}, and @code{dlerror} can be used to obtain a > -corresponding error message. > +On success, @code{dlinfo} returns 0 for most request types; exceptions > +are noted below. If there is an error, the function returns @math{-1}, > +and @code{dlerror} can be used to obtain a corresponding error message. OK. > > The following operations are defined for use with @var{request}: > > @@ -82,6 +82,15 @@ This request writes the TLS module ID for the shared object @var{handle} > to @code{*@var{arg}}. The argument @var{arg} must be the address of an > object of type @code{size_t}. The module ID is zero if the object > does not have an associated TLS block. > + > +@item RTLD_DI_PHDR > +This request writes the address of the program header array to > +@code{*@var{arg}}. The argument @var{arg} must be the address of an > +object of type @code{const ElfW(Phdr) *} (that is, > +@code{const Elf32_Phdr *} or @code{const Elf64_Phdr *}, as appropriate > +for the current architecture). For this request, the value returned by > +@code{dlinfo} is the number of program headers in the program header > +array. OK. > @end vtable > @end deftypefun > > -- Cheers, Carlos.