From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.osci.io (polly.osci.io [8.43.85.229]) by sourceware.org (Postfix) with ESMTP id E1DA13899401 for ; Thu, 12 Mar 2020 05:59:12 +0000 (GMT) Received: by mx1.osci.io (Postfix, from userid 994) id E174820CFB; Thu, 12 Mar 2020 01:59:11 -0400 (EDT) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-Spam-Level: X-Spam-Status: No, score=-26.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, SPF_HELO_NONE, SPF_NONE autolearn=ham autolearn_force=no version=3.4.2 Received: from gnutoolchain-gerrit.osci.io (gnutoolchain-gerrit.osci.io [8.43.85.239]) by mx1.osci.io (Postfix) with ESMTP id 867DC20495; Thu, 12 Mar 2020 01:59:07 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by gnutoolchain-gerrit.osci.io (Postfix) with ESMTP id 5ED4620AF7; Thu, 12 Mar 2020 01:59:07 -0400 (EDT) X-Gerrit-PatchSet: 2 Date: Thu, 12 Mar 2020 01:59:06 -0400 From: "Sourceware to Gerrit sync (Code Review)" To: Kevin Buettner , gdb-patches@sourceware.org Auto-Submitted: auto-generated X-Gerrit-MessageType: newpatchset Subject: [pushed] Avoid infinite recursion in find_pc_sect_line X-Gerrit-Change-Id: I595470be6ab5f61ca7e4e9e70c61a252c0deaeaa X-Gerrit-Change-Number: 682 X-Gerrit-ChangeURL: X-Gerrit-Commit: dd69bf7a78a489783c397f2552eeb7999defcb6a In-Reply-To: References: Reply-To: noreply@gnutoolchain-gerrit.osci.io, simon.marchi@polymtl.ca, luis.machado@linaro.org, kevinb@redhat.com, gdb-patches@sourceware.org MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Disposition: inline User-Agent: Gerrit/3.0.3-79-g83ff7f88f1 Content-Type: text/plain; charset=UTF-8 Message-Id: <20200312055907.5ED4620AF7@gnutoolchain-gerrit.osci.io> 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: , X-List-Received-Date: Thu, 12 Mar 2020 05:59:13 -0000 The original change was created by Kevin Buettner. Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/682 ...................................................................... Avoid infinite recursion in find_pc_sect_line 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 --- M gdb/ChangeLog M gdb/symtab.c 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index e8fc63c..f6bd31c 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2020-03-11 Kevin Buettner + + * symtab.c (find_pc_sect_line): Add check which prevents infinite + recursion. + 2020-03-11 Simon Marchi * configure: Re-generate. diff --git a/gdb/symtab.c b/gdb/symtab.c index 44b7113..aa415a9 100644 --- a/gdb/symtab.c +++ b/gdb/symtab.c @@ -3158,7 +3158,17 @@ ; /* 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; -- Gerrit-Project: binutils-gdb Gerrit-Branch: master Gerrit-Change-Id: I595470be6ab5f61ca7e4e9e70c61a252c0deaeaa Gerrit-Change-Number: 682 Gerrit-PatchSet: 2 Gerrit-Owner: Kevin Buettner Gerrit-Reviewer: Kevin Buettner Gerrit-CC: Luis Machado Gerrit-CC: Simon Marchi Gerrit-MessageType: newpatchset