From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id xevXJaIOGWB+JAAAWB0awg (envelope-from ) for ; Tue, 02 Feb 2021 03:34:42 -0500 Received: by simark.ca (Postfix, from userid 112) id 8C66E1EF80; Tue, 2 Feb 2021 03:34:42 -0500 (EST) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on simark.ca X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server2.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id 6EA441E939 for ; Tue, 2 Feb 2021 03:34:41 -0500 (EST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 221093857C7F; Tue, 2 Feb 2021 08:34:41 +0000 (GMT) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by sourceware.org (Postfix) with ESMTPS id 6CAF03857C7F for ; Tue, 2 Feb 2021 08:34:36 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 6CAF03857C7F Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tdevries@suse.de X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 82989ACAC; Tue, 2 Feb 2021 08:34:35 +0000 (UTC) Subject: Re: [PATCH][gdb/symtab] Fix assert in write_one_signatured_type To: Simon Marchi , gdb-patches@sourceware.org References: <20210201144321.GA1874@delia> From: Tom de Vries Message-ID: <40ead098-8fed-1bdc-cf03-f2fb135d606b@suse.de> Date: Tue, 2 Feb 2021 09:34:35 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gdb-patches-bounces@sourceware.org Sender: "Gdb-patches" On 2/1/21 5:16 PM, Simon Marchi wrote: > On 2021-02-01 9:43 a.m., Tom de Vries wrote:> Hi, >> >> When running test-case gdb.dwarf2/fission-reread.exp with target board >> cc-with-gdb-index, we run into an abort during the generation of the gdb-index >> by cc-with-tweaks.sh: >> ... >> build/gdb/testsuite/cache/gdb.sh: line 1: 27275 Aborted (core dumped) >> ... >> >> This can be reproduced on the command line like this: >> ... >> $ gdb -batch ./outputs/gdb.dwarf2/fission-reread/fission-reread \ >> -ex 'save gdb-index ./outputs/gdb.dwarf2/fission-reread' >> warning: Could not find DWO TU fission-reread.dwo(0x9022f1ceac7e8b19) \ >> referenced by TU at offset 0x0 [in module fission-reread] >> warning: Could not find DWO CU fission-reread.dwo(0x807060504030201) \ >> referenced by CU at offset 0x561 [in module fission-reread] >> Aborted (core dumped) >> ... >> >> The abort is a segfault due to a using a nullptr psymtab in >> write_one_signatured_type. >> >> The problem is that we're trying to write index entries for the type unit >> with signature: >> ... >> (gdb) p /x entry->signature >> $2 = 0x9022f1ceac7e8b19 >> ... >> which is a skeleton type unit: >> ... >> Contents of the .debug_types section: >> >> Compilation Unit @ offset 0x0: >> Length: 0x4a (32-bit) >> Version: 4 >> Abbrev Offset: 0x165 >> Pointer Size: 4 >> Signature: 0x9022f1ceac7e8b19 >> Type Offset: 0x0 >> <0><17>: Abbrev Number: 2 (DW_TAG_type_unit) >> <18> DW_AT_comp_dir : /tmp/src/gdb/testsuite >> <2f> DW_AT_GNU_dwo_name: fission-reread.dwo >> <42> DW_AT_GNU_pubnames: 0x0 >> <46> DW_AT_GNU_pubtypes: 0x0 >> <4a> DW_AT_GNU_addr_base: 0x0 >> ... >> referring to a .dwo file, but as the warnings show, the .dwo file is not >> found. >> >> Fix this by skipping the type unit in write_one_signatured_type if >> psymtab == nullptr. >> >> Tested on x86_64-linux. >> >> Any comments? >> >> Thanks, >> - Tom >> >> [gdb/symtab] Fix assert in write_one_signatured_type >> >> gdb/ChangeLog: >> >> 2021-02-01 Tom de Vries >> >> PR symtab/24620 >> * dwarf2/index-write.c (write_one_signatured_type): Skip if >> psymtab == nullptr. >> >> --- >> gdb/dwarf2/index-write.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/gdb/dwarf2/index-write.c b/gdb/dwarf2/index-write.c >> index 66781feaf46..a7b9ae66cae 100644 >> --- a/gdb/dwarf2/index-write.c >> +++ b/gdb/dwarf2/index-write.c >> @@ -616,6 +616,14 @@ write_one_signatured_type (void **slot, void *d) >> struct signatured_type *entry = (struct signatured_type *) *slot; >> partial_symtab *psymtab = entry->per_cu.v.psymtab; >> >> + if (psymtab == nullptr) >> + { >> + /* We can end up here when processing a skeleton CU referring to a >> + .dwo file that hasn't been found. There's not much we can do in >> + such a case, so skip this CU. */ >> + return 1; >> + } >> + >> write_psymbols (info->symtab, info->psyms_seen, >> psymtab->global_psymbols, info->cu_index, >> 0); >> > LGTM, some questions: > > 1. Do we need to emit a warning here? Probably not because another one > should have been emitted earlier, when parsing symbols. But I thought > I'd ask just in case. > Yeah, I think the existing warning is sufficient. > 2. Would it be somewhat easy to write a test for this? Have a type unit > with a dwo, delete the dwo, try to generate an index. > I've added a test-case to fission-reread.exp. > 3. Is the same situation correctly handled for standard compile units? I've tried the following experiment: I've done a gdb testsuite run with target board fission-dwp, with a hack added to cc-with-tweaks.sh to remove the .dwp file. Apart from a lot of FAILs, all I ran into was PR27313 "Segfault in insert_catch_syscall" ( https://sourceware.org/bugzilla/show_bug.cgi?id=27313 ). Committed with test-case added. Thanks, - Tom