This is a request for some help from the IBM'ers on the list... Starting somewhere in the 3.10 timeframe (I believe), the virtual-to-physical translation of kernel modules no longer works for ppc64. User-space vtop also seems to be broken. For example, here's an example using a 3.10.0-0.rc4.59.el7.ppc64 kernel, which shows the "WARNING: cannot access vmalloc'd module memory" message during initialization, and I also show the results of a "vtop" on the first and last module addresses in the kernel's "modules" list: # crash crash 7.0.1 Copyright (C) 2002-2013 Red Hat, Inc. Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation Copyright (C) 1999-2006 Hewlett-Packard Co Copyright (C) 2005, 2006, 2011, 2012 Fujitsu Limited Copyright (C) 2006, 2007 VA Linux Systems Japan K.K. Copyright (C) 2005, 2011 NEC Corporation Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc. Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc. This program is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Enter "help copying" to see the conditions. This program has absolutely no warranty. Enter "help warranty" for details. GNU gdb (GDB) 7.6 Copyright (C) 2013 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "powerpc64-unknown-linux-gnu"... WARNING: cannot access vmalloc'd module memory KERNEL: /usr/lib/debug/lib/modules/3.10.0-0.rc4.59.el7.ppc64/vmlinux DUMPFILE: /dev/crash CPUS: 28 DATE: Mon Jun 24 13:35:45 2013 UPTIME: 01:54:23 LOAD AVERAGE: 0.00, 0.17, 0.23 TASKS: 318 NODENAME: ibm-p730-04-lp4.rhts.eng.bos.redhat.com RELEASE: 3.10.0-0.rc4.59.el7.ppc64 VERSION: #1 SMP Mon Jun 3 14:42:22 EDT 2013 MACHINE: ppc64 (3550 Mhz) MEMORY: 8 GB PID: 30000 COMMAND: "crash" TASK: c000000192860000 [THREAD_INFO: c0000001c6c00000] CPU: 5 STATE: TASK_RUNNING (ACTIVE) crash> p modules modules = $1 = { next = 0xd00000000d019080, prev = 0xd000000001016f10 } crash> vtop 0xd00000000d019080 VIRTUAL PHYSICAL d00000000d019080 (not mapped) PAGE DIRECTORY: c0000000011d0000 L4: c0000000011d0000 => c0000001fba80000 PMD: c0000001fba80000 => c0000001fba70000 PMD: c0000001fba80000 => fba76808 PTE: fba76808 => 0 crash> vtop 0xd000000001016f10 VIRTUAL PHYSICAL d000000001016f10 (not mapped) PAGE DIRECTORY: c0000000011d0000 L4: c0000000011d0000 => c0000001fba80000 PMD: c0000001fba80000 => c0000001fba70000 PMD: c0000001fba80000 => fba70808 PTE: fba70808 => 0 crash> I'm not at all familiar with ppc64 page table walk-throughs, but what little debugging I've tried has yielded nothing other than module-address-translation that end up with PTE's that contain zero like the above. Also, the vtop of user-space addresses also seems to be completely disfunctional. Taking the live system above, if I take the user-space address of the page-table page buffer used by the crash utility itself, and try to do a vtop on it, it yields this obviously bogus result: crash> help -m | grep ptbl: ptbl: 100133d6f10 crash> vtop 100133d6f10 VIRTUAL PHYSICAL 100133d6f10 (not mapped) PAGE DIRECTORY: c0000001e0940000 L4: c0000001e0940008 => 0 VMA START END FLAGS FILE c00000001b7d0000 10012fe0000 100167b0000 100073 crash> It seems to have been something recently introduced, as here's a 3.9.0-0.rc8.54.el7.ppc64 kernel, which works just fine: # crash crash 7.0.1 Copyright (C) 2002-2013 Red Hat, Inc. Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation Copyright (C) 1999-2006 Hewlett-Packard Co Copyright (C) 2005, 2006, 2011, 2012 Fujitsu Limited Copyright (C) 2006, 2007 VA Linux Systems Japan K.K. Copyright (C) 2005, 2011 NEC Corporation Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc. Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc. This program is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Enter "help copying" to see the conditions. This program has absolutely no warranty. Enter "help warranty" for details. GNU gdb (GDB) 7.6 Copyright (C) 2013 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "powerpc64-unknown-linux-gnu"... KERNEL: /usr/lib/debug/lib/modules/3.9.0-0.rc8.54.el7.ppc64/vmlinux DUMPFILE: /dev/crash CPUS: 28 DATE: Mon Jun 24 13:50:38 2013 UPTIME: 00:12:20 LOAD AVERAGE: 0.22, 0.17, 0.16 TASKS: 316 NODENAME: ibm-p730-04-lp4.rhts.eng.bos.redhat.com RELEASE: 3.9.0-0.rc8.54.el7.ppc64 VERSION: #1 SMP Mon Apr 22 18:30:40 EDT 2013 MACHINE: ppc64 (3550 Mhz) MEMORY: 8 GB PID: 7035 COMMAND: "crash" TASK: c0000001ddf00000 [THREAD_INFO: c0000001bb780000] CPU: 4 STATE: TASK_RUNNING (ACTIVE) crash> p modules modules = $1 = { next = 0xd00000000c729100, prev = 0xd000000000fe6ff8 } crash> vtop 0xd00000000c729100 VIRTUAL PHYSICAL d00000000c729100 1cfb29100 PAGE DIRECTORY: c000000001190000 L4: c000000001190000 => c0000001fba80000 PMD: c0000001fba80000 => c0000001fba60000 PMD: c0000001fba80000 => fba66390 PTE: fba66390 => 73ec88000395 PAGE: 1cfb20000 PTE PHYSICAL FLAGS 73ec88000395 1cfb20000 (PRESENT|RW|COHERENT|DIRTY|ACCESSED) PAGE PHYSICAL MAPPING INDEX CNT FLAGS c0000000042c26f0 1cfb20000 0 0 1 73c0400000000 crash> vtop 0xd000000000fe6ff8 VIRTUAL PHYSICAL d000000000fe6ff8 1eba16ff8 PAGE DIRECTORY: c000000001190000 L4: c000000001190000 => c0000001fba80000 PMD: c0000001fba80000 => c0000001fba60000 PMD: c0000001fba80000 => fba607f0 PTE: fba607f0 => 7ae848000395 PAGE: 1eba10000 PTE PHYSICAL FLAGS 7ae848000395 1eba10000 (PRESENT|RW|COHERENT|DIRTY|ACCESSED) PAGE PHYSICAL MAPPING INDEX CNT FLAGS c000000004482338 1eba10000 0 0 1 7ac0400000000 crash> And the user-space vtop example works as expected: crash> help -m | grep ptbl: ptbl: 1001d208c80 crash> vtop 1001d208c80 VIRTUAL PHYSICAL 1001d208c80 1a1b18c80 PAGE DIRECTORY: c0000001ec8a9c00 L4: c0000001ec8a9c08 => c0000001f0a50000 PMD: c0000001f0a50008 => c0000001c7f20000 PMD: c0000001f0a50008 => c7f26900 PTE: c7f26900 => 686c48000393 PAGE: 1a1b10000 PTE PHYSICAL FLAGS 686c48000393 1a1b10000 (PRESENT|USER|COHERENT|DIRTY|ACCESSED) VMA START END FLAGS FILE c0000001eb523af0 1001ce20000 100206f0000 100073 PAGE PHYSICAL MAPPING INDEX CNT FLAGS c000000003fe26b8 1a1b10000 c0000001e93f4c41 1001d20 1 6840400080068 crash> Any ideas? Thanks, Dave