Re: [PATCH 45/48] x86/Kconfig: Enable CONFIG_PREFIX_SYMBOLS for FineIBT

David Laight
2026-04-24T09:02:28Z

On Thu, 23 Apr 2026 18:29:02 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> On Thu, Apr 23, 2026 at 09:23:12AM -0700, Josh Poimboeuf wrote:
>
> > > > Sorry, how do you get 64 here?
> > >
> > > DEBUG_FORCE_FUNCTION_ALIGNMENT_64B=y
> >
> > Ok, so in that case it would be 5-byte cfi symbol and 59-byte NOP gap.
> > Or a 64-byte pfx for the !CFI case.
>
> Just so.
>

Isn't there also an average of 32 NOP bytes to align the 'gap' on a 64
byte boundary?
Has anyone looked at changing clang to take a parameter for the size
of the gap?
That would significantly reduce the overhead for small functions.

David