From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 65172 invoked by alias); 26 Sep 2017 03:15:50 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 65105 invoked by uid 89); 26 Sep 2017 03:15:38 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.0 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,RCVD_IN_DNSWL_NONE,RCVD_IN_SORBS_SPAM,RP_MATCHES_RCVD,SPF_PASS autolearn=ham version=3.3.2 spammy=Depends X-HELO: mail-io0-f171.google.com Received: from mail-io0-f171.google.com (HELO mail-io0-f171.google.com) (209.85.223.171) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 26 Sep 2017 03:15:36 +0000 Received: by mail-io0-f171.google.com with SMTP id v36so11588088ioi.1 for ; Mon, 25 Sep 2017 20:15:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=cBTdSwkQhiknPQUiD4znDZad+dJm/ahDw8vkKcQhU68=; b=mnZKwuJNC8hWXarNToCc7DwwTlPbFs7K4jPum28feOJMvyeAjcJEyiZ90CpPRL1Jqf xJZ4MGcsjND4UFWTiQntPjkHv3Y4/7BaNHNlDZdnyN7AcASIanJy7zxsLVQ7nbuMJKYz bkLHPi2hlJ0tpTanhZhew+dknTvmACM9qRBLaM5KDJ3rZ5CkQFHpZdw8GnWAO5r2ao9J 5x/OxpsWw8N1rcFLf/7Hx1wS/4w4lzcFEKVxNsCCfWhRDJVImhjfQoayuuTXYpWc/D3O twD8pk9RsjdDWM8A1jwGB0NgWzAX9wZWrEHt7839jFKmTNpI+xLzGT0T3kX5/VOTpHiU W4Tw== X-Gm-Message-State: AHPjjUh8A6GIKvxiq8SX8jI8iFANtlZbnFwauxJkzOZqXuE5WrM6Asbe oM2zoReDLDt/IUaLXm+auSx1TX8glEuSdLJKec5UyQ== X-Google-Smtp-Source: AOwi7QBntGyiJ5S/N6+tnE1CLNPaXbeh+u4JTDkpnJU3psVx7Tmm+xTJbyMTdYGK97XzzWxMhnebl7t8yip4Ar9Zseg= X-Received: by 10.107.131.198 with SMTP id n67mr12239469ioi.74.1506395734453; Mon, 25 Sep 2017 20:15:34 -0700 (PDT) MIME-Version: 1.0 Received: by 10.107.34.131 with HTTP; Mon, 25 Sep 2017 20:14:53 -0700 (PDT) In-Reply-To: References: From: "Doug Evans via gdb-patches" Reply-To: Doug Evans Date: Tue, 26 Sep 2017 03:15:00 -0000 Message-ID: Subject: Re: [PATCH] Fix reading .dwp files without .debug_tu_index To: Alexander Shaposhnikov Cc: gdb-patches Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2017-09/txt/msg00779.txt.bz2 On Tue, Sep 19, 2017 at 12:58 PM, Alexander Shaposhnikov wrote: > This patch fixes segmentation fault (due to dereferencing of a null pointer) > in dwarf2read.c in the code dwp_file->cus->version != dwp_file->tus->version > by adding defensive checks similarly to how it's already done > at the lines 11208 - 11215 (in the same file dwarf2read.c). > The issue can be reproduced with dwp packages built by llvm-dwp utility > (from the current upstream) since at the moment llvm-dwp doesn't create > .debug_tu_index section, thus dwp_file->tus will be null. > > Test plan: > > BUILD: > main.cpp: > int f() { > int x = 0; > int y = 1; > return x + y; > } > g++ -fPIC -gsplit-dwarf -g -O0 main.cpp -o main.exe > llvm-dwp main.dwo -o main.exe.dwp > # This step is a workaround to a separate issue (unrelated to this patch). > # At the moment llvm tools & clang put .strtab section first (its index is > 1), > # while gcc/gold/binutils put it at the end. > # Unfortunately gdb (in the code reading dwps) appears to depend on the > order > # of sections, That's odd. Depends on the order of sections how? > to workaround this (to reproduce the issue which this patch > # aims to address) we use objcopy to do the following trick: > # if one asks to remove .strtab objcopy will do that but at the same time > # it will create a new .shstrtab section at the end. > objcopy --remove-section .strtab main.exe.dwp > RUN: > gdb main.exe > One can observe that now there is no crash and debugging functionality > works as expected (setting breakpoints, printing local variable, exploring > the stack). > > gdb/ChangeLog: > yyyy-mm-dd Alexander Shaposhnikov > > * dwarf2read.c: Fix segmentation fault on reading > > .dwp files without .debug_tu_index section. > > Patch: > > diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c > > index b1914cf876..547e3f034e 100644 > --- a/gdb/dwarf2read.c > +++ b/gdb/dwarf2read.c > @@ -11185,7 +11185,8 @@ open_and_init_dwp_file (void) > dwp_file->tus = create_dwp_hash_table (dwp_file, 1); > > /* The DWP file version is stored in the hash table. Oh well. */ > - if (dwp_file->cus->version != dwp_file->tus->version) > + if (dwp_file->cus && dwp_file->tus > + && dwp_file->cus->version != dwp_file->tus->version) > { > /* Technically speaking, we should try to limp along, but this is > pretty bizarre. We use pulongest here because that's the established > @@ -11195,7 +11196,7 @@ open_and_init_dwp_file (void) > pulongest (dwp_file->cus->version), > pulongest (dwp_file->tus->version), dwp_name.c_str ()); > } > - dwp_file->version = dwp_file->cus->version; > + dwp_file->version = dwp_file->cus ? dwp_file->cus->version : 0; A version of 0 doesn't seem right. I'd go with something like (untested and likely improperly formatted): if (dwp_file->cus) dwp_file->version = dwp_file-cus->version; else if (dwp_file->tus) dwp_file->version = dwp_file->tus->version else dwp_file->version = 2; ok with that change. > > if (dwp_file->version == 2) > bfd_map_over_sections (dwp_file->dbfd, dwarf2_locate_v2_dwp_sections, > > > Kind regards, > Alexander Shaposhnikov