kmemleak: enable tracking for percpu pointers

Patch series "kmemleak: support for percpu memory leak detect'.

This is a rework of this series:
https://lore.kernel.org/lkml/20200921020007.35803-1-chenjun102@huawei.com/

Originally I was investigating a percpu leak on our customer nodes and
having this functionality was a huge help, which lead to this fix [1].

So probably it's a good idea to have it in mainstream too, especially as
after [2] it became much easier to implement (we already have a separate
tree for percpu pointers).

[1] commit 0af8c09c ("netfilter: x_tables: fix percpu counter block leak on error path when creating new netns")
[2] commit 39042079 ("kmemleak: avoid RCU stalls when freeing metadata for per-CPU pointers")


This patch (of 2):

This basically does:

- Add min_percpu_addr and max_percpu_addr to filter out unrelated data
  similar to min_addr and max_addr;

- Set min_count for percpu pointers to 1 to start tracking them;

- Calculate checksum of percpu area as xor of crc32 for each cpu;

- Split pointer lookup and update refs code into separate helper and use
  it twice: once as if the pointer is a virtual pointer and once as if
  it's percpu.

[ptikhomirov@virtuozzo.com: v2]
  Link: https://lkml.kernel.org/r/20240731025526.157529-2-ptikhomirov@virtuozzo.com
Link: https://lkml.kernel.org/r/20240725041223.872472-1-ptikhomirov@virtuozzo.com
Link: https://lkml.kernel.org/r/20240725041223.872472-2-ptikhomirov@virtuozzo.com


Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Cc: Chen Jun <chenjun102@huawei.com>
Cc: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>