Re: [RFC PATCH v1 18/57] trace: Remove PAGE_SIZE compile-time constant assumption
From: Steven Rostedt
Date: Fri Oct 18 2024 - 11:23:55 EST
On Tue, 15 Oct 2024 12:09:38 +0100
Ryan Roberts <ryan.roberts@xxxxxxx> wrote:
> >
> > Not to mention, when function graph tracing is enabled, this gets triggered
> > for *every* function call! So I do not want any runtime test done. Every
> > nanosecond counts in this code path.
> >
> > If anything, this needs to be moved to initialization and checked once, if
> > it fails, gives a WARN_ON() and disables function graph tracing.
>
> I'm hoping my suggestion above to decouple SHADOW_STACK_SIZE from PAGE_SIZE is
> acceptable and simpler? If not, happy to do as you suggest here.
Yeah, I think we can do that. In fact, I'm thinking it should turn into a
kmem_cache item that doesn't have to be a power of two (but must be evenly
divisible by the size of long).
I'll write up a patch.
-- Steve