Re: [patch 064/158] mm: add generic ptdump

Linus Torvalds
2019-12-01T14:53:48Z

On Sun, Dec 1, 2019 at 1:09 AM Borislav Petkov <bp@alien8.de> wrote:
>
> That generic ptdump stuff is probably causing a splat on 32-bit:
>
> https://lkml.kernel.org/r/20191125144946.GA6628@duo.ucw.cz

Hmm. I'm not sure about code generation, but for me that config gives me

60: 55 push %ebp
61: 89 e5 mov %esp,%ebp
63: 57 push %edi
64: 8b 4d 08 mov 0x8(%ebp),%ecx
67: 56 push %esi
68: 53 push %ebx
69: 8b 30 mov (%eax),%esi
6b: 8b 59 10 mov 0x10(%ecx),%ebx

so that "ptdump_pte_entry+9" is the "mov (%eax),%esi"

And that is "READ_ONCE(*pte)"

So the pte pointer itself is broken. Which sounds really odd.

Hmm. I've applied the whole series to a local branch, but I'm not
merging it into my master branch yet. Can somebody figure out how the
page walking could get that broken?

Linus