Re: [RFC 0/5] kernel: backtrace unwind support

[Benjamin Herrenschmidt]

On Fri, 2012-02-10 at 12:37 -0800, Linus Torvalds wrote:
> On Fri, Feb 10, 2012 at 12:18 PM, Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> >
> > yep, looks interesting.. not sure about the mathematical proof though ;)
> 
> Well, I can already say what the old code did horribly horribly wrong:
> 
>  - *all* stack accesses need to go through a validation function, they
> can never *ever* just try to access the stack.
> 
>     The validation function really needs to really check the full
> range of the stack area, not something random.
> 
>  - all dwarf information accesses need to similarly validate the
> access, and accept that sometimes the dwarf info is simply missing or
> actively wrong.

In addition it should all go through something like
copy_from_user_inatomic(), ie, all access to that stuff should have
built-in fault recovery without triggering high level page faults, stack
expansion etc...

Cheers,
Ben.


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