On Wed, Oct 27, 2021 at 07:38:59PM +0200, Borislav Petkov wrote:
> On Tue, Oct 26, 2021 at 02:01:42PM +0200, Peter Zijlstra wrote:
> > +static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes)
> > +{
> > + retpoline_thunk_t *target;
> > + int reg, i = 0;
> > +
> > + target = addr + insn->length + insn->immediate.value;
> > + reg = target - __x86_indirect_thunk_array;
> > +
> > + if (WARN_ON_ONCE(reg & ~0xf))
> > + return -1;
> > +
> > + /* If anyone ever does: CALL/JMP *%rsp, we're in deep trouble. */
> > + BUG_ON(reg == 4);
> > +
> > + if (cpu_feature_enabled(X86_FEATURE_RETPOLINE))
> > + return -1;
>
> I wanna say this should be the first thing being checked on function
> entry but I get the feeling you'll be looking at other X86_FEATURE bits
> in future patches... /me goes into the future...
>
> yap, you do. Lemme look at the whole thing first then.
I wanted the sanity checks done unconditionally.
