Re: [Crash-utility] [PATCH] crash utility: fix max_mapnr issue on system has over 44-bit addressing

----- Original Message ----- > The patch will add support for new compressed dumpfile header_version 6. > > This bug was posted here: > http://lists.infradead.org/pipermail/kexec/2013-September/009587.html > > This patch will add a new field in struct kdump_sub_header. > unsigned long max_mapnr; > > And the old "unsigned int max_mapnr" in struct disk_dump_header will > not be used anymore. But still be there for compatibility purpose. > > Signed-off-by: Jingbai Ma&lt;jingbai.ma(a)hp.com&gt; Hello Jingbai, This patch needs to be backwards-compatible with respect to diskdump dumpfiles. Your patch presumes that it's always dealing with a compressed kdump, and as a result it immediately generates a SIGSEGV when presented with a diskdump dumpfile: $ crash vmcore vmlinux.gz crash 7.0.3rc5 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. Segmentation fault (core dumped) $ The SIGSEGV is generated from this patch to read_dump_header(): + if (header->header_version< 6) + sub_header_kdump->max_mapnr = header->max_mapnr; because the sub_header_kdump pointer is only malloc'd if the dumpfile is a compressed kdump. And after that, all of the presumptive usages of the kdump_sub_header must be handled differently, e.g., this will fail: static inline int -dump_is_partial(const struct disk_dump_header *header) +dump_is_partial(const struct disk_dump_header *header, + const struct kdump_sub_header *sub_header) { return header->bitmap_blocks>= - divideup(divideup(header->max_mapnr, 8), dd->block_size) * 2; + divideup(divideup(sub_header->max_mapnr, 8), dd->block_size) * 2; } So pretty much everywhere that you've replaced "dd->header->max_mapnr" with either "sub_header_kdump->max_mapnr" or "dd->sub_header_kdump->max_mapnr" needs to be changed to use something like a pre-initialized local variable "max_mapnr" that gets set appropriately to the dumpfile type. Thanks, Dave