target/arm: Implement FEAT_PAN3
FEAT_PAN3 adds an EPAN bit to SCTLR_EL1 and SCTLR_EL2, which allows
the PAN bit to make memory non-privileged-read/write if it is
user-executable as well as if it is user-read/write.
Implement this feature and enable it in the AArch64 'max' CPU.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230331145045.2584941-4-peter.maydell@linaro.org
diff --git a/target/arm/ptw.c b/target/arm/ptw.c
index 6d72950..bd75da8 100644
--- a/target/arm/ptw.c
+++ b/target/arm/ptw.c
@@ -947,6 +947,7 @@
static int get_S1prot(CPUARMState *env, ARMMMUIdx mmu_idx, bool is_aa64,
int ap, int ns, int xn, int pxn)
{
+ ARMCPU *cpu = env_archcpu(env);
bool is_user = regime_is_user(env, mmu_idx);
int prot_rw, user_rw;
bool have_wxn;
@@ -958,8 +959,19 @@
if (is_user) {
prot_rw = user_rw;
} else {
+ /*
+ * PAN controls can forbid data accesses but don't affect insn fetch.
+ * Plain PAN forbids data accesses if EL0 has data permissions;
+ * PAN3 forbids data accesses if EL0 has either data or exec perms.
+ * Note that for AArch64 the 'user can exec' case is exactly !xn.
+ * We make the IMPDEF choices that SCR_EL3.SIF and Realm EL2&0
+ * do not affect EPAN.
+ */
if (user_rw && regime_is_pan(env, mmu_idx)) {
- /* PAN forbids data accesses but doesn't affect insn fetch */
+ prot_rw = 0;
+ } else if (cpu_isar_feature(aa64_pan3, cpu) && is_aa64 &&
+ regime_is_pan(env, mmu_idx) &&
+ (regime_sctlr(env, mmu_idx) & SCTLR_EPAN) && !xn) {
prot_rw = 0;
} else {
prot_rw = simple_ap_to_rw_prot_is_user(ap, false);
