[Crash-utility] "cannot access vmalloc'd module memory" when loading kdump'ed vmcore in crash

[Worth, Kevin]

Hello kexec and crash mailing lists,

Sorry to spam whoever's code this ISN'T an issue with, but I really am unsure of whether is a kdump or a crash issue. I am running an Ubuntu 7.04 with a 2.6.20 kernel (includes Ubuntus patches- source at http://packages.ubuntu.com/feisty/linux-source-2.6.20 ) and a modified VMSPLIT/PAGE_OFFSET value (see bottom for details) on an i386 machine with 4GB of memory. At first I thought this could be an issue with makedumpfile stripping out things it shouldn't, but I've found that setting up my initrd script so that it simply performs "cp /proc/vmcore /var/crash/vmcore" results in the same issue.

I've tried this with both crash 4.0-6.3 and 4.0-7.2 and get the same result. Unfortunately I'm locked at kernel 2.6.20 for other reasons, or else I would try that.

If anyone can offer suggestions of what to try, please let me know. If this is something that has already been resolved elsewhere, sorry to waste time, and if someone can point me to what resolved it, perhaps I can look at backporting the fix myself. Thanks for your time.

crash-4.0-7.2$ ./crash ~/vmcore ~/targetfiles/vmlinux-2.6.20-17.39-custom2

crash 4.0-7.2
<snip>Copyright notices...</snip>
GNU gdb 6.1
<snip>Copyright notices...</snip>
This GDB was configured as "i686-pc-linux-gnu"...

please wait... (gathering module symbol data)
WARNING: cannot access vmalloc'd module memory

      KERNEL: /home/worthk/targetfiles/vmlinux-2.6.20-17.39-custom2
    DUMPFILE: /home/worthk/vmcore
        CPUS: 2
        DATE: Wed Oct  1 12:30:50 2008
      UPTIME: 00:35:11
LOAD AVERAGE: 0.07, 0.09, 0.08
       TASKS: 94
    NODENAME: test-module
     RELEASE: 2.6.20-17.39-custom2
     VERSION: #3 SMP Wed Sep 24 10:11:03 PDT 2008
     MACHINE: i686  (2200 Mhz)
      MEMORY: 5 GB
<6>SysRq : Trigger a crashdump"
         PID: 4304
     COMMAND: "bash"
        TASK: 5d7e9030  [THREAD_INFO: f4b70000]
         CPU: 0
       STATE: TASK_RUNNING (SYSRQ)

crash> mod -s test
mod: cannot access vmalloc'd module memory


My kernel config is a bit outside the norm, in that the VMSPLIT value has been modified to give 3GB of memory the kernelspace and 1GB of memory to userspace. Below is a diff between the default Ubuntu "generic" config and mine:

diff /boot/config-2.6.20-17-generic /boot/config-2.6.20-17.37-custom2
3,4c3,4
< # Linux kernel version: 2.6.20-17-generic < # Wed Aug 20 14:43:36 2008
---
> # Linux kernel version: 2.6.20-17.37-custom2 # Tue Aug 19 18:50:53
> 2008
33c33
< CONFIG_VERSION_SIGNATURE="Ubuntu 2.6.20-17.39-generic"
---
> CONFIG_VERSION_SIGNATURE="Ubuntu 2.6.20-17.37-generic"
51c51
< # CONFIG_EMBEDDED is not set
---
> CONFIG_EMBEDDED=y
188,190c188,194
< CONFIG_HIGHMEM4G=y
< # CONFIG_HIGHMEM64G is not set
< CONFIG_PAGE_OFFSET=0xC0000000
---
> # CONFIG_HIGHMEM4G is not set
> CONFIG_HIGHMEM64G=y
> # CONFIG_VMSPLIT_3G is not set
> # CONFIG_VMSPLIT_3G_OPT is not set
> # CONFIG_VMSPLIT_2G is not set
> CONFIG_VMSPLIT_1G=y
> CONFIG_PAGE_OFFSET=0x40000000
191a196
> CONFIG_X86_PAE=y
204c209
< # CONFIG_RESOURCES_64BIT is not set
---
> CONFIG_RESOURCES_64BIT=y
1161a1167
> CONFIG_IDE_MAX_HWIFS=4
1443a1450
> # CONFIG_PATA_PLATFORM is not set
1525a1533
> CONFIG_I2O_EXT_ADAPTEC_DMA64=y


Kevin Worth
Network Security Software Engineer
ProCurve networking by HP
kevin.worth at hp.com<mailto:kevin.worth at hp.com>
ph 916.785.4528
fx 916.785.1196
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