[Xen-devel] xen domU core dump question.

[Nehal Bandi <nehal.bandi@xxxxxxxxx>]

Hello,

I have some questions about xen  dump-core which is an ELF format and I am sure this is the best place to ask for advice because I doubt the xen-users list 

will be very helpful for this.

http://xenbits.xen.org/docs/unstable/misc/dump-core-format.txt

One of the section in the core dump ELF format is about 'xen_pages' which I think is the domain's memory.

I wanted to extract HVM domain memory from xen domain core dump.

Following is what is read from a core dump of win-7 domU with 2 GB memory.

========================================================

readelf -S win7_xen.core 

There are 7 section headers, starting at offset 0x40:

Section Headers:

  [Nr] Name              Type             Address           Offset

       Size              EntSize          Flags  Link  Info  Align

  [ 0] <no-name>         NULL             0000000000000000  00000000

       0000000000000000  0000000000000000           0     0     0

  [ 1] <no-name>         STRTAB           0000000000000000  00000000803f6fa0

       0000000000000048  0000000000000000           0     0     0

  [ 2] <no-name>         NOTE             0000000000000000  00000200

       0000000000000564  0000000000000000           0     0     0

  [ 3] <no-name>         PROGBITS         0000000000000000  00000764

       0000000000001430  0000000000001430           0     0     8

  [ 4] <no-name>         PROGBITS         0000000000000000  00001b94

       0000000000001000  0000000000001000           0     0     8

  [ 5] <no-name>         PROGBITS         0000000000000000  00003000

       000000007fff4000  0000000000001000           0     0     4096

  [ 6] <no-name>         PROGBITS         0000000000000000  7fff7000

       00000000003fffa0  0000000000000008           0     0     8

=====================================

In the above Elf image I extracted the section 5 ( xen_pages)  size is 2GB - 48 KB ( 12 pages less then full 2GB).

Window's 64 bit domain dump with 4 GB memory.

Section Headers:

  [Nr] Name              Type             Address           Offset

       Size              EntSize          Flags  Link  Info  Align

  [ 0]                   NULL             0000000000000000  00000000

       0000000000000000  0000000000000000           0     0     0

  [ 1]                   STRTAB           0000000000000000  00000001007f6fa0

       0000000000000048  0000000000000000           0     0     0

  [ 2]                   NOTE             0000000000000000  00000200

       0000000000000564  0000000000000000           0     0     0

  [ 3]                   PROGBITS         0000000000000000  00000764

       0000000000001430  0000000000001430           0     0     8

  [ 4]                   PROGBITS         0000000000000000  00001b94

       0000000000001000  0000000000001000           0     0     8

  [ 5]                   PROGBITS         0000000000000000  00003000

       00000000ffff4000  0000000000001000           0     0     4096

  [ 6]                   PROGBITS         0000000000000000  00000000ffff7000

       00000000007fffa0  0000000000000008           0     0     8

============================================================

In the above Elf again the section 5 is 4GB - 48KB (again 12 pages less then 4GB domain memory)

The questions I have are :

Is my understanding correct about the 'xen_pages', is it really VM memory ?

are these missing  48KB (12 pages) xen specific ?? Can I get those pages from xen ??

Thank you in advance.

-Regards,

Nehal

 

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