From patchwork Wed Dec 4 21:54:39 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Buettner X-Patchwork-Id: 36525 Received: (qmail 97108 invoked by alias); 4 Dec 2019 21:55:10 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 97093 invoked by uid 89); 4 Dec 2019 21:55:10 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-16.0 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_STOCKGEN autolearn=ham version=3.3.1 spammy=1999, surrounding, April, diligence X-HELO: us-smtp-delivery-1.mimecast.com Received: from us-smtp-1.mimecast.com (HELO us-smtp-delivery-1.mimecast.com) (205.139.110.61) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 04 Dec 2019 21:55:08 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575496507; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=mVc8V0VQP4tUzey90zZhv1hxCboOn3Wtar1r7rqcYK8=; b=gEuWWcDgHAAwwirpi1fjN3j41EbBLAUg+LdJKv4KHdctGfrg9Bo/zaYF9FTYTpBNTcDUdF cYk+xUZaWZ8by4DMPLfFOJeCt6ASUTPfag8Bpq2/kYc9KLC58WT9w0KUBc4quTTPp6pzUC FnvBdUGrsisFRlXaFoh+KbokZzuGE1Y= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-226-LSAaRYmeOrG95NzKgQtIgg-1; Wed, 04 Dec 2019 16:55:06 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6EA0318B6380 for ; Wed, 4 Dec 2019 21:55:05 +0000 (UTC) Received: from f31-1.lan (ovpn-116-54.phx2.redhat.com [10.3.116.54]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2BB5310013A1; Wed, 4 Dec 2019 21:55:05 +0000 (UTC) From: Kevin Buettner To: gdb-patches@sourceware.org Cc: Kevin Buettner Subject: [PATCH v2] Avoid infinite recursion in find_pc_sect_line Date: Wed, 4 Dec 2019 14:54:39 -0700 Message-Id: <20191204215439.1748221-1-kevinb@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-IsSubscribed: yes A patch somewhat like this patch has been in Fedora GDB for well over a decade. The Fedora patch was written by Jan Kratochvil. The Fedora version prints a warning and attempts to continue. This version will error out, fatally. An earlier version of this patch was more like the Fedora version than this one. Simon Marchi recommended use of an assertion to test for the infinite recursion; I decided to use an explicit test (with an "if" statement) along with a call to internal_error() if the condition is met. This way, I could include a plea to file a bug report. It was motivated by a customer reported bug (back in 2006!) which showed infinite mutual recursion between find_pc_sect_line and find_pc_line. Here is a portion of the backtrace from the bug report: (gdb) bt #0 0x00000000004450a4 in lookup_minimal_symbol_by_pc_section ( pc=251700325328, section=0x570f500) at gdb/minsyms.c:484 #1 0x00000000004bbfb2 in find_pc_sect_line (pc=251700325328, section=0x570f500, notcurrent=0) at gdb/symtab.c:2057 #2 0x00000000004bc480 in find_pc_line (pc=251700325328, notcurrent=0) at gdb/symtab.c:2232 #3 0x00000000004bc1ff in find_pc_sect_line (pc=251700325328, section=0x570f500, notcurrent=0) at gdb/symtab.c:2081 ... (lots and lots of the same two functions with the same parameters) #1070 0x00000000004bc480 in find_pc_line (pc=251700325328, notcurrent=0) at gdb/symtab.c:2232 #1071 0x00000000004bc1ff in find_pc_sect_line (pc=251700325328, section=0x570f500, notcurrent=0) at gdb/symtab.c:2081 #1072 0x00000000004bc480 in find_pc_line (pc=251700325328, notcurrent=0) at gdb/symtab.c:2232 #1073 0x00000000004bc1ff in find_pc_sect_line (pc=251700325328, section=0x570f500, notcurrent=0) at gdb/symtab.c:2081 #1074 0x00000000004bc480 in find_pc_line (pc=251700325328, notcurrent=0) at gdb/symtab.c:2232 #1075 0x00000000004bc1ff in find_pc_sect_line (pc=251696794399, section=0x59b0df8, notcurrent=0) at gdb/symtab.c:2081 #1076 0x00000000004bc480 in find_pc_line (pc=251696794399, notcurrent=0) at gdb/symtab.c:2232 #1077 0x000000000055550e in find_frame_sal (frame=0xb3f3e0, sal=0x7fff1d1a8200) at gdb/frame.c:1392 #1078 0x00000000004d86fd in set_current_sal_from_frame (frame=0x1648, center=1) at gdb/stack.c:379 #1079 0x00000000004cf137 in normal_stop () at gdb/infrun.c:3147 ... The test case was a large application. Attempts were made to make a small(er) test case, but those attempts were not successful. Therefore, I cannot provide a new test for this patch. That said, we ought to guard against recursively calling find_pc_sect_line (via find_pc_line) with the identical PC value that it had been called with. Should this happen, infinite recursion (as shown in the above backtrace) is the result. This patch prevents that from happening. If this should happens, there is a bug somewhere, perhaps in GDB, perhaps in some other part of the toolchain or a library. We error out fatally with a message briefly describing the condition along with a plea to file a bug report. I spent some time looking at the surrounding code and commentary which handle the case of PC being in a stub/trampoline. It first appeared in the public GDB repository in April, 1999. The ChangeLog entry for this commit is from 1998-12-31. The relevant portion is: (find_pc_sect_line): Return correct information if pc is in import or export stub (trampoline). What's remarkable about the overall ChangeLog entry is that it's over 2500+ lines long! I believe that this was part of the infamous "HP merge" (in which insufficient due diligence was given in accepting a large batch of changes from an outside source). In the years that followed, much of this code was either significantly revised or outright removed. For this particular case, I'm grateful that extensive comments were provided by "RT". (I haven't been able to figure out who RT is/was.) I've decided against attempting to revise this stub/trampoline handling code any further than adding Jan's test which prevents an obvious case of infinite recursion. I've tested on Fedora 31, x86-64. I see no regressions. I've also searched the logfile for the new message, but as expected, no message was found (which is good). gdb/ChangeLog: * symtab.c (find_pc_sect_line): Add check which prevents infinite recursion. Change-Id: I595470be6ab5f61ca7e4e9e70c61a252c0deaeaa --- gdb/symtab.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/gdb/symtab.c b/gdb/symtab.c index 5c33fbf9ab..95020d843c 100644 --- a/gdb/symtab.c +++ b/gdb/symtab.c @@ -3167,7 +3167,17 @@ find_pc_sect_line (CORE_ADDR pc, struct obj_section *section, int notcurrent) ; /* fall through */ else - return find_pc_line (BMSYMBOL_VALUE_ADDRESS (mfunsym), 0); + { + /* Detect an obvious case of infinite recursion. If this + should occur, we'd like to know about it, so error out, + fatally. */ + if (BMSYMBOL_VALUE_ADDRESS (mfunsym) == pc) + internal_error (__FILE__, __LINE__, + _("Infinite recursion detected in find_pc_sect_line;" + "please file a bug report")); + + return find_pc_line (BMSYMBOL_VALUE_ADDRESS (mfunsym), 0); + } } symtab_and_line val;