On Fri, Jan 09, 2015 at 06:06:33PM +0100, Andrew Jones wrote:
> Cleanup XN/PXN handling in get_phys_addr_lpae, and implement all but
> EL2 support of the following ARMv8 sections
>
> D4.5.1 Memory access control: Access permissions for instruction
> execution
> G4.7.2 Execute-never restrictions on instruction fetching
>
> G4.7.2 matches the ARMv7 section B3.7.2 when long-descriptors are used.
>
> Signed-off-by: Andrew Jones <drjo...@redhat.com>
>
> ---
> I didn't test this with secure mode (I didn't even check if that's
> currently possible), but I did test all other EL1&0 XN controls with
> both tcg-arm (cortex-a15) and tcg-aarch64 (cortex-a57) by hacking up
> some tests with kvm-unit-tests/arm[64]. I also booted Linux (just
> up to looking for a rootfs) with both.
> ---
> target-arm/helper.c | 99
> ++++++++++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 79 insertions(+), 20 deletions(-)
>
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 3ef0f1f38eda5..48a83cff957fb 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -4516,6 +4516,69 @@ static inline int check_ap(CPUARMState *env, int ap,
> int domain_prot,
> }
> }
>
> +/* Check section/page execution permission.
> + *
> + * Returns PAGE_EXEC if execution is permitted, otherwise zero.
> + *
> + * Supports AArch64, AArch32, and v7-LPAE. Doesn't yet support
> + * EL2. Actually, for v7-LPAE, we'd also need to emulate Virt
> + * Extensions to truly have WXN/UWXN. We don't support checking
> + * for that yet, so we just assume we have them.
> + *
> + * @env : CPUARMState
> + * @is_user : 0 for privileged access, 1 for user
> + * @ap : Access permissions (AP[2:1]) from descriptor
> + * @ns : (NSTable || NS) from descriptors
> + * @xn : ([U]XNTable || [U]XN) descriptors
> + * @pxn : (PXNTable || PXN) descriptors
Just realized I'm missing 'from' in the last two lines above.
> + */
> +static int check_xn_lpae(CPUARMState *env, int is_user, int ap,
> + int ns, int xn, int pxn)
> +{
> + int wxn;
> +
> + switch (arm_current_el(env)) {
> + case 0:
> + case 1:
> + if (is_user && !(ap & 1)) {
> + return 0;
> + }
> + wxn = env->cp15.sctlr_el[1] & SCTLR_WXN;
> + if (arm_el_is_aa64(env, 1)) {
> + pxn = pxn || ((ap & 1) && !(ap & 2));
> + xn = is_user ? xn : pxn;
> + } else {
> + int uwxn = env->cp15.sctlr_el[1] & SCTLR_UWXN;
> + pxn = pxn || (uwxn && (ap & 1) && !(ap & 2));
> + xn = xn || (!is_user && pxn);
> + }
> + if (arm_is_secure(env)) {
> + xn = xn || (ns && (env->cp15.scr_el3 & SCR_SIF));
> + }
> + break;
> + case 2:
> + /* TODO actually support EL2 */
> + assert(true);
And, argh... brain wires got crossed here. Of course this should
be 'assert(false)'. I'll send a v2.
> +
> + if (arm_el_is_aa64(env, 2)) {
> + wxn = env->cp15.sctlr_el[2] & SCTLR_WXN;
> + } else {
> + /* wxn = HSCTLR.WXN */
> + }
> + break;
> + case 3:
> + if (arm_el_is_aa64(env, 3)) {
> + wxn = env->cp15.sctlr_el[3] & SCTLR_WXN;
> + } else {
> + wxn = 0;
> + }
> + xn = xn || (ns && (env->cp15.scr_el3 & SCR_SIF));
> + break;
> + }
> +
> + return xn || (!(ap & 2) && wxn) ? 0 : PAGE_EXEC;
> +}
> +
> static bool get_level1_table_address(CPUARMState *env, uint32_t *table,
> uint32_t address)
> {
> @@ -4787,7 +4850,7 @@ static int get_phys_addr_lpae(CPUARMState *env,
> target_ulong address,
> hwaddr descaddr, descmask;
> uint32_t tableattrs;
> target_ulong page_size;
> - uint32_t attrs;
> + uint32_t attrs, ap;
> int32_t granule_sz = 9;
> int32_t va_size = 32;
> int32_t tbi = 0;
> @@ -4941,7 +5004,7 @@ static int get_phys_addr_lpae(CPUARMState *env,
> target_ulong address,
> if (extract32(tableattrs, 2, 1)) {
> attrs &= ~(1 << 4);
> }
> - /* Since we're always in the Non-secure state, NSTable is ignored. */
> + attrs |= extract32(tableattrs, 4, 1) << 3; /* NS */
> break;
> }
> /* Here descaddr is the final physical address, and attributes
> @@ -4952,29 +5015,25 @@ static int get_phys_addr_lpae(CPUARMState *env,
> target_ulong address,
> /* Access flag */
> goto do_fault;
> }
> +
> fault_type = permission_fault;
> - if (is_user && !(attrs & (1 << 4))) {
> + ap = extract32(attrs, 4, 2); /* AP[2:1] */
> +
> + if (is_user && !(ap & 1)) {
> /* Unprivileged access not enabled */
> goto do_fault;
> }
> - *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
> - if ((arm_feature(env, ARM_FEATURE_V8) && is_user && (attrs & (1 << 12)))
> ||
> - (!arm_feature(env, ARM_FEATURE_V8) && (attrs & (1 << 12))) ||
> - (!is_user && (attrs & (1 << 11)))) {
> - /* XN/UXN or PXN. Since we only implement EL0/EL1 we unconditionally
> - * treat XN/UXN as UXN for v8.
> - */
> - if (access_type == 2) {
> - goto do_fault;
> - }
> - *prot &= ~PAGE_EXEC;
> +
> + *prot = PAGE_READ;
> + *prot |= check_xn_lpae(env, is_user, ap, extract32(attrs, 3, 1),
> + extract32(attrs, 12, 1), extract32(attrs, 11, 1));
> + if (!(*prot & PAGE_EXEC) && access_type == 2) {
> + goto do_fault;
> }
> - if (attrs & (1 << 5)) {
> - /* Write access forbidden */
> - if (access_type == 1) {
> - goto do_fault;
> - }
> - *prot &= ~PAGE_WRITE;
> +
> + *prot |= !(ap & 2) ? PAGE_WRITE : 0;
> + if (!(*prot & PAGE_WRITE) && access_type == 1) {
> + goto do_fault;
> }
>
> *phys_ptr = descaddr;
> --
> 1.9.3
>
