Re: [Crash-utility] Kernel pages reported as PAGE_EXCLUDED
----- Original Message -----
----- Original Message -----
> Hi,
> I'm analyzing a dump file ("KDUMP" header) with crash 7.0.1 that
seems
> to have some kernel pages missing:
>
> crash> struct foo ffff81101e19e000
> struct foo struct: page excluded: kernel virtual address: ffff81101e19e000 type:
"gdb_readmem_callback"
> Cannot access memory at address 0xffff81101e19e000
>
> When I set debug to 1 it turns out that even crash's 'mount' command
hits excluded pages:
> mount: page excluded: kernel virtual address: ffff81101d688000 type:
> "read_string characters"
I also see that on some dumps, but I don't believe that it's a problem since it
doesn't
affect the command when it's run normally:
crash> set debug 1
debug: 1
crash> mount
VFSMOUNT SUPERBLK TYPE DEVNAME DIRNAME
ffff9a9fd3ddc080 ffff8a1fdfcf2400 rootfs rootfs /
ffff8e9fd25f7e80 ffff9d9fdfcf1800 proc proc /proc
ffff919fd3612e80 ffff949fdfd01400 sysfs sysfs /sys
ffff949fd3483e80 ffff931fd3281c00 devtmpfs devtmpfs /dev/
ffff9a9fd3ddce80 ffff961fd24db400 devpts devpts /pts
ffff9a9fd3ddcd80 ffff9a9fd3b51c00 tmpfs tmpfs /shm
ffff8a1fcef1fe80 ffff8a1fd13f1400 ext4 /dev/mapper/mpathap4 /
ffff901fd2519e80 ffff9c1fd24e7000 selinuxfs none /selinux
ffff931fd156ee80 ffff931fd3281c00 devtmpfs devtmpfs /dev
ffff8e9fd25f7080 ffff949fd1698400 usbfs /proc/bus/usb /proc/bus/usb
ffff9d9fd2439e80 ffff9d9fd1837c00 ext4 /dev/mapper/mpathap2 /boot
ffff9d9fd2439d80 ffff9d9fd1994800 vfat /dev/mapper/mpathap1 /boot/efi
ffff8d1fc7705e80 ffff8d1fd1e73800 mount: page excluded: kernel virtual address:
ffff8d1fc7f98000 type: "read_string characters"
binfmt_misc none /proc/sys/fs/binfmt_misc
ffff919fd3612280 ffff919fd3b97c00 cgroup cgroup /cgroup/cpuset
ffff919fd2227ec0 ffff919fd3e5c400 cgroup cgroup /cgroup/cpu
ffff919fd2227dc0 ffff919fd1130400 cgroup cgroup /cgroup/cpuacct
ffff919fd2227cc0 ffff919fd3e5c800 cgroup cgroup /cgroup/memory
ffff919fd2227bc0 ffff919fd1793400 cgroup cgroup /cgroup/devices
ffff919fd2227ac0 ffff919fd3e5cc00 cgroup cgroup /cgroup/freezer
ffff919fd22279c0 ffff919fd2b93400 cgroup cgroup /cgroup/net_cls
ffff919fd22278c0 ffff919fd232c400 cgroup cgroup /cgroup/blkio
ffff9c1fd13c5e80 ffff9c1fd109cc00 autofs /etc/auto.misc /misc
ffff961fd3debe80 ffff961fd23c6800 autofs -hosts /net
crash>
I haven't checked the exact location where that error message is
being generated from, but I note that there are several constructs in the
mount-command-related code that do "if (read_string(...)) else ...", so they
are potentially expected to fail behind the scenes (quietly unless
debug is 1).
So I wouldn't worry about that particular issue, but I would be concerned
if you can prove that an address that you're trying to read is absolutely
a kernel data structure. And I'm not aware of any "struct foo" instances
in the kernel... ;-)
Dave