From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 125273 invoked by alias); 19 Oct 2017 17:54:49 -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 124999 invoked by uid 89); 19 Oct 2017 17:54:49 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.9 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,RP_MATCHES_RCVD,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 spammy= X-HELO: smtp.polymtl.ca Received: from smtp.polymtl.ca (HELO smtp.polymtl.ca) (132.207.4.11) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 19 Oct 2017 17:54:47 +0000 Received: from simark.ca (simark.ca [158.69.221.121]) (authenticated bits=0) by smtp.polymtl.ca (8.14.7/8.14.7) with ESMTP id v9JHseEc015896 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 19 Oct 2017 13:54:45 -0400 Received: by simark.ca (Postfix, from userid 112) id 8082E1E540; Thu, 19 Oct 2017 13:54:40 -0400 (EDT) Received: from simark.ca (localhost [127.0.0.1]) by simark.ca (Postfix) with ESMTP id 0EE731E08F; Thu, 19 Oct 2017 13:54:29 -0400 (EDT) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 19 Oct 2017 17:54:00 -0000 From: Simon Marchi To: Mike Gulick Cc: gdb-patches@sourceware.org Subject: Re: [RFC][PATCH] fix gdb segv when objfile can't be opened In-Reply-To: <8c08307a-94ad-92b8-9c8b-c713cad541fd@mathworks.com> References: <59E8B251.4050100@mathworks.com> <8c08307a-94ad-92b8-9c8b-c713cad541fd@mathworks.com> Message-ID: <56b1cb34b33613ca4496abfcd28f135a@polymtl.ca> X-Sender: simon.marchi@polymtl.ca User-Agent: Roundcube Webmail/1.3.0 X-Poly-FromMTA: (simark.ca [158.69.221.121]) at Thu, 19 Oct 2017 17:54:40 +0000 X-IsSubscribed: yes X-SW-Source: 2017-10/txt/msg00641.txt.bz2 On 2017-10-19 11:59, Mike Gulick wrote: > I apologize for the improperly formatted patch -- I'm really struggling > to get thunderbird to behave as I want. > > Here is an updated patch. I would have sent it with git send-email, > but > I could not figure out the proper way to add this preface before the > patch (without it looking like part of the commit message). Hi Mike, Thanks, I was able to apply this version correctly. If I have a short comment that's not meant to be in the commit message, I usually include it in brackets like this: [Re-sending this patch because the first try was not formatted correctly.] If it's longer you can always end it with a line "Actual commit message:". Either way, it's not really a big deal, as long as it's clear. You can use the --annotate option of git-send-email to edit the message before sending it. > --- > From 5dee04076518554e4baae864569d6f4faee9b685 Mon Sep 17 00:00:00 2001 > From: Mike Gulick > Date: Wed, 18 Oct 2017 16:04:27 -0400 > Subject: [PATCH] fix gdb segv when objfile can't be opened > > This fixes PR 16577. > > This patch changes gdb_bfd_map_section to issue a warning rather than > an > error if it is unable to read the object file, and sets the size of the > section/frame that it attempted to read to 0 on error. > > The description of gdb_bfd_map_section states that it will try to read > or map the contents of the section SECT, and if successful, the section > data is returned and *SIZE is set to the size of the section data. > This > function was throwing an error and leaving *size as-is. Setting the > section size to 0 indicates to dwarf2_build_frame_info that there is no > data to read, otherwise it will try to read from an invalid frame > pointer. > > Changing the error to a warning allows this to be handled gracefully. > Additionally, the error was clobbering the breakpoint output indicating > the current frame (function name, arguments, source file, and line > number). > E.g. > > Thread 3 "foo" hit Breakpoint 1, BFD: reopening > /tmp/jna-1013829440/jna2973250704389291330.tmp: No such file or > directory > > BFD: reopening /tmp/jna-1013829440/jna2973250704389291330.tmp: No such > file or directory For some reason, I am not able to reproduce the crash using the instructions in the bug report, and gdb master. (gdb) up #1 0x00007ffff78d525a in sleep () from /lib/x86_64-linux-gnu/libc.so.6 (gdb) BFD: reopening ./badlib.so: No such file or directory BFD: reopening ./badlib.so: No such file or directory Can't read data for section '.eh_frame' in file './badlib.so' (gdb) Initial frame selected; you cannot go up. (gdb) Initial frame selected; you cannot go up. (gdb) Initial frame selected; you cannot go up. (gdb) bt #0 0x00007ffff78d52f0 in nanosleep () from /lib/x86_64-linux-gnu/libc.so.6 #1 0x00007ffff78d525a in sleep () from /lib/x86_64-linux-gnu/libc.so.6 Would you be able to create a test case to reproduce it? We would need one to go in with the fix in the end anyway, and it's easier for reviewers if they can just run a test file rather than try to reproduce by hand. You can start by copying an existing solib test, like gdb.base/solib-display.exp. See here for more details about tests: http://sourceware.org/gdb/wiki/TestingGDB http://sourceware.org/gdb/wiki/GDBTestcaseCookbook Don't hesitate to ask here or on IRC if you need assistance. > (gdb) > > While the "BFD: reopening ..." messages will still appear interspersed > in the > breakpoint output, the current frame info is now displayed: > > Thread 3 "foo" hit Breakpoint 1, BFD: reopening > /tmp/jna-1013829440/jna1875755897659885075.tmp: No such file or > directory > > BFD: reopening /tmp/jna-1013829440/jna1875755897659885075.tmp: No such > file or directory > > warning: Can't read data for section '.eh_frame' in file > '/tmp/jna-1013829440/jna1875755897659885075.tmp' > do_something () at file.cpp:80 > 80 { > (gdb) > --- > gdb/gdb_bfd.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c > index 29080b8..229f5ae 100644 > --- a/gdb/gdb_bfd.c > +++ b/gdb/gdb_bfd.c > @@ -705,9 +705,15 @@ gdb_bfd_map_section (asection *sectp, > bfd_size_type *size) > > data = NULL; > if (!bfd_get_full_section_contents (abfd, sectp, &data)) > - error (_("Can't read data for section '%s' in file '%s'"), > - bfd_get_section_name (abfd, sectp), > - bfd_get_filename (abfd)); > + { > + warning (_("Can't read data for section '%s' in file '%s'"), > + bfd_get_section_name (abfd, sectp), > + bfd_get_filename (abfd)); > + /* Section is invalid -- set size to 0 and return NULL */ > + descriptor->size = 0; > + *size = descriptor->size; > + return (const gdb_byte *) NULL; > + } > descriptor->data = data; > > done: I don't know if it is really this function's responsibility to clear *size in case of error, or it would be the callers responsibility to properly check for errors. But if the function doesn't throw anymore, the comment in gdb_bfd.h should be updated accordingly. Thanks, Simon