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[81.151.181.184]) by smtp.gmail.com with ESMTPSA id t2sm4404742wmt.15.2020.05.06.12.13.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 May 2020 12:13:57 -0700 (PDT) Date: Wed, 6 May 2020 20:13:56 +0100 From: Andrew Burgess To: Kunal Chauhan Cc: gdb@gnu.org Subject: Re: Fwd: Help: please help to use gdb and its related terms Message-ID: <20200506191356.GB2242921@embecosm.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: Linux/5.5.17-200.fc31.x86_64 (x86_64) X-Uptime: 20:03:50 up 16 days, 6:31, X-Editor: GNU Emacs [ http://www.gnu.org/software/emacs ] Received-SPF: pass client-ip=2a00:1450:4864:20::32f; envelope-from=andrew.burgess@embecosm.com; helo=mail-wm1-x32f.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-Spam-Status: No, score=-13.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_SOFTFAIL, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gdb@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 May 2020 19:14:07 -0000 * Kunal Chauhan via Gdb [2020-05-05 21:39:32 +0530]: > ---------- Forwarded message ---------- > From: "Kunal Chauhan" > Date: 5 May 2020 6:55 p.m. > Subject: Help: please help to use gdb and its related terms > To: > Cc: > > Hi Team, > > Here is some output of gdb I am not understanding . > > #0 0xb66e8ee4 in strlen () from /lib/libc.so.6 > > [Current thread is 1 (LWP 2084)] > > (gdb) bt full > > #0 0xb66e8ee4 in strlen () from /lib/libc.so.6 > > No symbol table info available. You're currently in strlen in libc.so.6 (at address 0xb66e8ee4), but you don't have debug information available, so GDB will have unwound the stack using analysis of the function prologue (instead of using unwind information from the debug info). > > #1 0xb6da3854 in ?? () from /opt/qcom/lib/libcurl.so.4 > > No symbol table info available. The previous frame was somewhere is libcurl.so.4 (at address 0xb6da3854) , though GDB couldn't find a nearby text symbol (that's what the '??' tells us). There's no debug information available for this library either. The '??' could be the result of some really aggressive symbol removal from libcurl, or might indicate that the previous unwind went wrong and you're not really at 0xb6da3854. Again, the stack is going to be unwound using prologue analysis as there's no debug information available. > > #2 0x05b40000 in ?? () > > No symbol table info available. This is starting to look very wrong now (I'm always suspicious of addresses ending with 0000), GDB couldn't identify a function or even a file that claims this address. Again (obviously maybe) no debug information, prologue analysis unwind. > > Backtrace stopped: previous frame identical to this frame (corrupt stack?) > After unwinding GDB got back the same stack pointer and program counter for the previous frame. This most likely means the prologue analysis unwinder is trying to unwind an incorrect location, and is just getting back the same junk each time. GDB prints the above message and stops to avoid going into an endless loop. You should consider installing debug information if possible for libc and libcurl, this might aid the unwinder. It's possible that the prologue analysis unwinder went wrong for your target, you should try manually unwinding the stack (by checking the ABI for your target, and examining the machine state) and see if you agree with GDB. Hope this helps, Thanks, Andrew