Re: [PATCH v4 0/3] Compile-time stack frame pointer validation

Ingo Molnar
2015-05-20T10:33:46Z

* Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> In discussions around the live kernel patching consistency model RFC
> [1], Peter and Ingo correctly pointed out that stack traces aren't
> reliable. And as Ingo said, there's no "strong force" which ensures we
> can rely on them.
>
> So I've been thinking about how to fix that. My goal is to eventually
> make stack traces reliable. Or at the very least, to be able to detect
> at runtime when a given stack trace *might* be unreliable. But improved
> stack traces would broadly benefit the entire kernel, regardless of the
> outcome of the live kernel patching consistency model discussions.
>
> This patch set is just the first in a series of proposed stack trace
> reliability improvements. Future proposals will include runtime stack
> reliability checking, as well as compile-time and runtime DWARF
> validations.
>
> As far as I can tell, there are two main obstacles which prevent frame
> pointer based stack traces from being reliable:
>
> 1) Missing frame pointer logic: currently, most assembly functions don't
> set up the frame pointer.

Could you please paste here the output of what the new checks print
for x86/64 defconfig?

> As a first step, all reported non-compliances result in warnings.
> Right now I'm seeing 200+ warnings. Once we get them all cleaned
> up, we can change the warnings to build errors so the asm code can
> stay clean.

That's quite a bit ...

Thanks,

Ingo