buddy-dump: handle CONFIG_TRANSPARENT_HUGEPAGE

[xairy]

When I run buddy-dump -o 4 -z Normal -n while debugging a kernel that has CONFIG_TRANSPARENT_HUGEPAGE enabled, I see the following output:

gef> buddy-dump -o 4 -z Normal -n
[+] Wait for memory scan
[+] Parse OK, making output...
---------------------------------------------------------------------------------------------------------------- node[0] @ 0xffffffc00a21a780 ----------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------- zone[1] @ 0xffffffc00a21adc0 (Normal) -----------------------------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------------------------------------- per_cpu_pageset ----------------------------------------------------------------------------------------------------------------------
cpu: 0                                                                                                                                                                                                                                                       
cpu: 1
cpu: 2
cpu: 3
cpu: 4
  pcp_index: 12, order: 4 (0x010000 bytes), mtype: 0 (=Unmovable)
    page:0xfffffffe00600400  size:0x010000  virt:0xffffff8018010000-0xffffff8018020000  phys:0x0000000098010000-0x0000000098020000 (pcp, cpu=4)
    page:0xfffffffe005ffa00  size:0x010000  virt:0xffffff8017fe8000-0xffffff8017ff8000  phys:0x0000000097fe8000-0x0000000097ff8000 (pcp, cpu=4)
    page:0xfffffffe00249600  size:0x010000  virt:0xffffff8009258000-0xffffff8009268000  phys:0x0000000089258000-0x0000000089268000 (pcp, cpu=4)
...

What looks wrong here are PCP entries for order 4: PCP should only cover orders from 0 to 3.

I suspect this is just an issue with the output caused by gef forcing MIGRATE_PCPTYPES = 3 in dump_pcp_entry. When CONFIG_TRANSPARENT_HUGEPAGE is enabled, MIGRATE_PCPTYPES in the kernel is actually 4, and thus, gef miscalculates the page order based on PCP list index.

A simple fix of changing MIGRATE_PCPTYPES to be 4 solves the output issue. This might be a reasonable hot-fix.

However, possibly, the right fix would be to display Transparent HugePage PCP entries differently than normal PCP entries: I suspect at least their order should be calculated differently.