powerpc: dump as a single line areas mapping a single physical page.

powerpc: dump as a single line areas mapping a single physical page.

When using KASAN, there are parts of the shadow area where all
pages are mapped to the kasan_early_shadow_page. It is pointless
to dump one line for each of those pages (in the example below there
are 7168 entries pointing to the same physical page).

~# cat /sys/kernel/debug/kernel_page_tables
 ...
---[ kasan shadow mem start ]---
0xf7c00000-0xf8bfffff 0x06fac000       16M        rw       present           dirty  accessed
0xf8c00000-0xf8c03fff 0x00cd0000       16K        r        present           dirty  accessed
0xf8c04000-0xf8c07fff 0x00cd0000       16K        r        present           dirty  accessed
0xf8c08000-0xf8c0bfff 0x00cd0000       16K        r        present           dirty  accessed
0xf8c0c000-0xf8c0ffff 0x00cd0000       16K        r        present           dirty  accessed
0xf8c10000-0xf8c13fff 0x00cd0000       16K        r        present           dirty  accessed
 ... 7168 identical lines
0xffbfc000-0xffbfffff 0x00cd0000       16K        r        present           dirty  accessed
---[ kasan shadow mem end ]---
 ...

This patch modifies linux table dump to dump as a single line areas
where all addresses points to the same physical page. That physical
address is put inside [] to show that all virt pages points to the
same phys page.

~# cat /sys/kernel/debug/kernel_page_tables
 ...
---[ kasan shadow mem start ]---
0xf7c00000-0xf8bfffff  0x06fac000        16M        rw       present           dirty  accessed
0xf8c00000-0xffbfffff [0x00cd0000]       16K        r        present           dirty  accessed
---[ kasan shadow mem end ]---
 ...

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>