On Thu, Mar 19, 2015 at 01:59:33PM +0000, Marc Zyngier wrote:
> Since all immediate branches are PC-relative on Aarch64, these
> instructions cannot be used as an alternative with the simplistic
> approach we currently have (the immediate has been computed from
> the .altinstr_replacement section, and end-up being completely off
> if we insert it directly).
>
> This patch handles the b and bl instructions in a different way,
> using the insn framework to recompute the immediate, and generate
> the right displacement.
>
> Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm64/kernel/alternative.c | 55 +++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 53 insertions(+), 2 deletions(-)
[...]
> static int __apply_alternatives(void *alt_region)
> {
> struct alt_instr *alt;
> @@ -40,16 +83,24 @@ static int __apply_alternatives(void *alt_region)
> u8 *origptr, *replptr;
>
> for (alt = region->begin; alt < region->end; alt++) {
> + u32 insn;
> + int i;
> +
> if (!cpus_have_cap(alt->cpufeature))
> continue;
>
> - BUG_ON(alt->alt_len > alt->orig_len);
> + BUG_ON(alt->alt_len != alt->orig_len);
>
> pr_info_once("patching kernel code\n");
>
> origptr = (u8 *)&alt->orig_offset + alt->orig_offset;
> replptr = (u8 *)&alt->alt_offset + alt->alt_offset;
> - memcpy(origptr, replptr, alt->alt_len);
> +
> + for (i = 0; i < alt->alt_len; i += sizeof(insn)) {
> + insn = get_alt_insn(origptr + i, replptr + i);
> + *(u32 *)(origptr + i) = insn;
My brain's not firing on all cylinders right now, but do you need a
cpu_to_le32 here?
Will
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
