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<p class="MsoNormal">Hi:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Six years ago Dave and I were discussing using gdb on KDUMP files:<br>
<br>
<o:p></o:p></p>
<p class="MsoNormal"> <a href="http://www.redhat.com/archives/crash-utility/2008-March/msg00039.html">
http://www.redhat.com/archives/crash-utility/2008-March/msg00039.html</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">At the time you weren’t sure of gdb could read 64bit elf headers.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m trying to look at KDUMP files with gdb and seeing similar problems.<o:p></o:p></p>
<p class="MsoNormal">I configured and built gdb with –enable-largefile but it didn’t help.<o:p></o:p></p>
<p class="MsoNormal">I also tried uncommenting _<i>LARGE</i>_FILE in gdb/config.h thought I doubt that’s correct.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Wondering what’s been done in the last six years on this. The kernel I’m<o:p></o:p></p>
<p class="MsoNormal">Running with is only using 4GB but is running in 64 bit mode.<o:p></o:p></p>
<p class="MsoNormal"><o:p></o:p></p>
<p class="MsoNormal">Looking at the kexec src if seems KEXEC use to support:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> # KEXEC_ARGS="--elf32-core-headers"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">This was used to force the dump to be elf32 just so gdb could read the core file<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">It appears that this support was dropped for 64 bit machines by Vivek Goyak
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Who seems was concerned for the health of the crash utility:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif";color:#002060"> http://lse.sourceforge.net/kdump/patches/1.101-kdump10/broken-out/x86_64-kdump-remove-elf32-core-header-support.patch<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><br>
The Linux kernel Documentation/kdump/kdump.txt was last<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Updated on July 4<sup>th</sup> of this year and clearly says that gdb can<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Read KDUMP files but says the crash-dumping kernel should<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Be started with --elf32-core-headers kernel option:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">420 Analysis<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">421 ========<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">422<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">423 Before analyzing the dump image, you should reboot into a stable kernel.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">424<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">425 You can do limited analysis using GDB on the dump file copied out of<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">426 /proc/vmcore. Use the debug vmlinux built with -g and run the following<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">427 command:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">428<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">429
<b>gdb vmlinux <dump-file></b><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">430<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">431 Stack trace for the task on processor 0, register display, and memory<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">432 display work fine.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">433<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">434 Note: GDB cannot analyze core files generated in ELF64 format for x86.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">435 On systems with a maximum of 4GB of memory, you can generate<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">436 ELF32-format headers using the
<b>--elf32-core-headers</b> kernel option on the<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New"">437 dump kernel.<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">But I can’t fine the string
</span><span style="font-size:9.0pt;font-family:"Courier New"">elf32-core-headers
</span><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">in the kernel source code.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Looking at the gdb Bugzilla page:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><a href="https://sourceware.org/bugzilla/buglist.cgi?quicksearch=elf64">https://sourceware.org/bugzilla/buglist.cgi?quicksearch=elf64</a><o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Reading a few bug reports seems to indicate that gdb supports 64 bit elf.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">I’m just trying to get the normal stack back-trace to work,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">With formal and local variables, from a crash dump as well
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">as mapping the normal kernel memory so I can follow list like
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">that for the the system tasks.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">With gdb I can read the init_task with both gdb and crash but can only<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">follow the list with crash.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Anyone know what’s going on?<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">--<o:p></o:p></p>
<p class="MsoNormal">Pete/Piet Delaney
<o:p></o:p></p>
<p class="MsoNormal">O: +1 408 935-1813<o:p></o:p></p>
<p class="MsoNormal">C: +1 408 646-8557<o:p></o:p></p>
<p class="MsoNormal">H: +1 408 243-8872<o:p></o:p></p>
<p class="MsoNormal">Home Email: <a href="mailto:piet.delaney@gmail.com">piet.delaney@gmail.com</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><img border="0" width="504" height="89" id="Picture_x0020_1" src="cid:image001.jpg@01CFDD97.C9283790" alt="Unity_Email_Sig"><o:p></o:p></p>
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