----- "Jun Koi" <junkoi2004@xxxxxxxxx> wrote: > Hi, > > When using the latest crash on 2.6.27.14 to analyze live memory > (running crash without any option), I got a bug like below. How can I > fix that? > > (A similar problem is also seen on 2.6.27.8) > > Thanks, > Jun The "read error" indications are most likely due to your kernel being configured with CONFIG_STRICT_DEVMEM, which restricts /dev/mem access to the first 256 pages of physical memory, which makes it useless for the crash utility. If you cannot reconfigure your kernel without it, then you have two other options. 1. Port the RHEL/Fedora /dev/crash (drivers/char/crash.c) memory driver, and insmod it prior to invoking crash. Red Hat kernels have had the /dev/mem restriction in place by default since RHEL4. It's only fairly recently that it's been imposed by default in upstream kernels. 2. You can also write a simple kprobe module module that modifies the kernel's devmem_is_allowed() function to always return 1. That will fake the /dev/mem driver into accepting all physical address requests. I don't have the links off-hand, but if you search through this mailing list's archives, say since the September 2008 timeframe, you can find threads that that describe how (1) and (2) can be accomplished. But if it all possible, the easiest way to go is by reconfiguring your kernel with CONFIG_STRICT_DEVMEM turned off. I'm going to be out of touch for a couple of days, so I won't be of much further help until Wednesday. If anybody else on the list has done this, please give this guy any pointers you might have. Thanks, Dave > > ..... > GNU gdb 6.1 > Copyright 2004 Free Software Foundation, Inc. > GDB 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. > Type "show copying" to see the conditions. > There is absolutely no warranty for GDB. Type "show warranty" for > details. > This GDB was configured as "i686-pc-linux-gnu"... > > crash: read error: kernel virtual address: c0488200 type: > "cpu_possible_map" > WARNING: cannot read cpu_possible_map > crash: read error: kernel virtual address: c041b428 type: > "cpu_present_map" > WARNING: cannot read cpu_present_map > crash: read error: kernel virtual address: c041ab00 type: > "cpu_online_map" > WARNING: cannot read cpu_online_map > crash: read error: kernel virtual address: c04b1900 type: "xtime" > > -- > Crash-utility mailing list > Crash-utility@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/crash-utility -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility
