[PATCH 1/2] powerpc/xmon: support dumping software pagetables

Michael Ellerman mpe at ellerman.id.au
Fri Jul 21 16:59:35 AEST 2017

Nice !

Balbir Singh <bsingharora at gmail.com> writes:

> It would be nice to be able to dump page tables in a
> particular context
> Example use cases
> Dumping PTE contents to see the keys (useful for debugging)
> c0000000ba48c880 c0000000bab438b0   2677   2675 T  2 protection_keys

What is that ^ ?

> 0:mon> ds c0000000ba48c880 0x7ffff7f70000
> translating tsk c0000000ba48c880, addr 7ffff7f70000
> G: 0xb95b6400   U: 0xb6334000   M: 0xb6543000   PA: 0x012c0000, PTE: 0xd4800000012c0504

Without reading the code I don't grok what G/U/M mean.

Feel free to use more than one line of output :)

> Dumping vmalloc space
> 0:mon> ds 0 d000000000000000

I suspect we will want to do that a lot. So I'd rather the arguments
were reversed, and the second (task) can be omitted.

0:mon> ds x	== translate x via init_mm
0:mon> ds x y	== translate x via &y->mm

I guess it's easier for folks to find a task rather than an mm directly?
Otherwise it could take an mm not a task.

> translating tsk           (null), addr d000000000000000

We should special case that to say "using kernel page tables" or similar.

> G: 0x3d450400   U: 0xbc184000   M: 0x3d460000   PA: 0x7e010000, PTE: 0xc08000007e01018e

> I did not replicate the complex code of dump_pagetable and have no support
> for bolted linear mapping, thats why I've called it software pagetable
> dumping support.

Not sure about that naming. On hash it makes sense, but not on radix or
on other platforms.

Maybe 'dv' for dump Virtual address ?

It doesn't dump a PTE, it tries to translate an address into a PTE.


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