[Crash-utility] [Question] page excluded: kernel virtual address

Sunday, 28 May 2023

Dear Mantainers,

I find there is an inevitable problem for linux-5.x ARM64 kdump that&nbsp;the error
"page excluded: kernel virtual address: xxx" will be occured when read the
address of ext4_super_block for&nbsp;ext4 filesystem in latest crash utility debugging
enviroment.

1)&nbsp;Here's my reproduce steps:

crash64&gt; mount
&nbsp; &nbsp; &nbsp;MOUNT &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; SUPERBLK &nbsp; &nbsp; TYPE &nbsp; DEVNAME &nbsp; DIRNAME
ffff000001e65180 ffff000001c1c000 rootfs none &nbsp; &nbsp; &nbsp;/
ffff00002ea66000 ffff00000288e000 ext4 &nbsp; /dev/root /
crash64&gt; struct super_block.s_fs_info -x ffff00000288e000&nbsp; s_fs_info =
0xffff000002885000,
crash64&gt; struct ext4_sb_info.s_es -x 0xffff000002885000
&nbsp; s_es = 0xffff0000043c2400,
crash64&gt; struct ext4_sb_info.s_es -x 0xffff0000043c2400
struct: page excluded: kernel virtual address: ffff0000043c2400 &nbsp;type:
"gdb_readmem_callback"
crash64&gt; rd 0xffff0000043c2400rd: page excluded: kernel virtual address:
ffff0000043c2400 &nbsp;type: "64-bit KVADDR"

crash64&gt; kmem -p 0xffff0000043c2400&nbsp; &nbsp; &nbsp; PAGE &nbsp;
&nbsp; &nbsp; PHYSICAL &nbsp; &nbsp; &nbsp;MAPPING &nbsp;
&nbsp; &nbsp; INDEX CNT FLAGS
fffffc000010f080 443c2000 ffff000002f93af0 &nbsp; &nbsp; &nbsp; &nbsp;0
&nbsp;2 ffff00000022036 referenced,uptodate,lru,active,private,mappedtodisk
crash64&gt; vtop 0xffff0000043c2400
VIRTUAL &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; PHYSICAL
ffff0000043c2400 &nbsp;443c2400

PAGE DIRECTORY: ffff80001163b000
&nbsp; &nbsp;PGD: ffff80001163b000 =&gt; 180000007fff9803
&nbsp; &nbsp;PUD: ffff00003fff9000 =&gt; 180000007fff8803
&nbsp; &nbsp;PMD: ffff00003fff8108 =&gt; 180000007ffe0803
&nbsp; &nbsp;PTE: ffff00003ffe0e10 =&gt; 680000443c2f07
&nbsp; PAGE: 443c2000

&nbsp; &nbsp; &nbsp;PTE &nbsp; &nbsp; &nbsp; &nbsp;PHYSICAL
&nbsp;FLAGS
680000443c2f07 &nbsp;443c2000 &nbsp;(VALID|SHARED|AF|NG|PXN|UXN)

&nbsp; &nbsp; &nbsp; PAGE &nbsp; &nbsp; &nbsp; PHYSICAL &nbsp;
&nbsp; &nbsp;MAPPING &nbsp; &nbsp; &nbsp; INDEX CNT FLAGS
fffffc000010f080 443c2000 ffff000002f93af0 &nbsp; &nbsp; &nbsp; &nbsp;0
&nbsp;2 ffff00000022036 referenced,uptodate,lru,active,private,mappedtodisk

2)&nbsp;Here's the kernel virtual kernel memory layout for my tested arm64 kernel
version 5.15, we can see&nbsp;0xffff0000043c2400 is in the kernel&nbsp;linear
memory region&nbsp;:
[ &nbsp; &nbsp;0.000000] Virtual kernel memory layout:[ &nbsp;
&nbsp;0.000000] &nbsp; &nbsp; modules : 0xffff800008000000 -
0xffff800010000000 &nbsp; ( &nbsp; 128 MB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; vmalloc : 0xffff800010000000 -
0xfffffbfff0000000 &nbsp; (126975 GB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; &nbsp; .text :
0xffff800010000000 - 0xffff8000111a0000 &nbsp; ( 18048 KB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; &nbsp; .init :
0xffff800011640000 - 0xffff800011760000 &nbsp; ( &nbsp;1152 KB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; .rodata : 0xffff8000111a0000 -
0xffff800011636000 &nbsp; ( &nbsp;4696 KB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; &nbsp; .data :
0xffff800011760000 - 0xffff800011902200 &nbsp; ( &nbsp;1673 KB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; &nbsp; &nbsp;.bss :
0xffff800011902200 - 0xffff8000119c6fb0 &nbsp; ( &nbsp; 788 KB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; fixed &nbsp; :
0xfffffbfffdbf9000 - 0xfffffbfffe000000 &nbsp; ( &nbsp;4124 KB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; PCI I/O : 0xfffffbfffe800000 -
0xfffffbffff800000 &nbsp; ( &nbsp; &nbsp;16 MB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; vmemmap : 0xfffffc0000000000 -
0xfffffe0000000000 &nbsp; ( &nbsp;2048 GB maximum)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; 0xfffffc0000000000 - 0xfffffc0001000000 &nbsp; ( &nbsp;
&nbsp;16 MB actual)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; memory &nbsp;:
0xffff000000000000 - 0xffff000040000000 &nbsp; ( &nbsp;1024 MB)
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; PAGE_OFFSET &nbsp;:
0xffff000000000000
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; KIMAGE_VADDR &nbsp;:
0xffff800010000000
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; kimage_voffset :
0xffff7fffcfe00000
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; PHYS_OFFSET &nbsp;:
0x40000000
[ &nbsp; &nbsp;0.000000] &nbsp; &nbsp; start memory &nbsp;:
0x40000000

I have no idea whether this problem is something wrong with crash utility. Could anybody
please help this?

Thanks

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[Crash-utility] [Question] page excluded: kernel virtual address