[RFC PATCH v3 2/3] arm64/kernel: don't ban ADRP to work around Cortex-A53 erratum #843419

[Mark Rutland]

On Sat, Feb 24, 2018 at 05:54:01PM +0000, Ard Biesheuvel wrote:
> On 23 February 2018 at 17:25, Mark Rutland <mark.rutland at arm.com> wrote:
> > On Fri, Feb 23, 2018 at 05:17:31PM +0000, Ard Biesheuvel wrote:
> >> On 23 February 2018 at 17:15, Mark Rutland <mark.rutland at arm.com> wrote:
> >> > On Wed, Feb 14, 2018 at 11:36:44AM +0000, Ard Biesheuvel wrote:

> >> >> +     /* patch ADRP to ADR if it is in range */
> >> >> +     if (!reloc_insn_imm(RELOC_OP_PREL, place, val & ~0xfff, 0, 21,
> >> >> +                         AARCH64_INSN_IMM_ADR)) {
> >> >> +             ((u8 *)place)[3] &= 0x7f; /* clear opcode bit 31 */

> >> > Can we not construct the equivalent ADR using the usual insn code, and
> >> > insert it?
> >>
> >> Sure.
> >
> > Cheers!
> 
> Umm, it appears we don't have any code to emit ADR or ADRP
> instructions, and I am reluctant to add a bunch of routines that are
> only ever used to flick a single opcode bit.

Fair enough.

Mark.