On Mon, Apr 14, 2025 at 04:43:26PM -0700, Josh Poimboeuf wrote:
> > + * Verify all indirect calls are kCFI adorned by checking for the
> > + * UD2. Notably, doing __nocfi calls to regular (cfi) functions is
> > + * broken.
>
> This "__nocfi calls" is confusing me. IIUC, there are two completely
> different meanings for "nocfi":
>
> - __nocfi: disable the kcfi function entry stuff
Ah, no. __nocfi is a bit of a mess, this is both the function entry
thing, but also very much the caller verification stuff for indirect
calls done inside this function.
This leads to lovely stuff like:
void (*foo)(void);
static __always_inline __nocfi void nocfi_caller(void)
{
foo();
}
void bar(void)
{
nocfi_caller();
foo();
}
This actually compiles and has bar() have two distinctly different
indirect calls to foo, while bar itself has a __cfi preamble.
Anyway, let me have a poke at the annotation.
