On 25 June 2018 at 17:00, Alex Bennée <alex.ben...@linaro.org> wrote:
> Although technically not visible to userspace the kernel does make
> them visible via trap and emulate. For user mode we can provide the
> value directly but we need to relax our permission checks to do this.
>
> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
> ---
> target/arm/helper.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 6e6b1762e8..9d81feb124 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -5813,7 +5813,19 @@ void define_one_arm_cp_reg_with_opaque(ARMCPU *cpu,
> if (r->state != ARM_CP_STATE_AA32) {
> int mask = 0;
> switch (r->opc1) {
> - case 0: case 1: case 2:
> + case 0:
> +#ifdef CONFIG_USER_ONLY
> + /* Some AArch64 CPU ID/feature are exported to userspace
> + * by the kernel (see HWCAP_CPUID) */
> + if (r->opc0 == 3 && r->crn == 0 &&
> + (r->crm == 0 ||
> + (r->crm >= 4 && r->crm <= 7))) {
> + mask = PL0_R;
> + break;
> + }
> +#endif
> + /* fall-through */
> + case 1: case 2:
> /* min_EL EL1 */
> mask = PL1_RW;
> break;
This looks like a rather inelegant place to shove a CONFIG_USER_ONLY
special case. Isn't there a cleaner way to do whatever this is trying
to achieve?
thanks
-- PMM
