target/arm: Don't skip MTE checks for LDRT/STRT at EL0

The LDRT/STRT "unprivileged load/store" instructions behave like
normal ones if executed at EL0. We handle this correctly for
the load/store semantics, but get the MTE checking wrong.

We always look at s->mte_active[is_unpriv] to see whether we should
be doing MTE checks, but in hflags.c when we set the TB flags that
will be used to fill the mte_active[] array we only set the
MTE0_ACTIVE bit if UNPRIV is true (i.e.  we are not at EL0).

This means that a LDRT at EL0 will see s->mte_active[1] as 0,
and will not do MTE checks even when MTE is enabled.

To avoid the translate-time code having to do an explicit check on
s->unpriv to see if it is OK to index into the mte_active[] array,
duplicate MTE_ACTIVE into MTE0_ACTIVE when UNPRIV is false.

(This isn't a very serious bug because generally nobody executes
LDRT/STRT at EL0, because they have no use there.)

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230912140434.1333369-2-peter.maydell@linaro.org

target/arm/tcg/hflags.c

@@ -306,6 +306,15 @@ static CPUARMTBFlags rebuild_hflags_a64(CPUARMState *env, int el, int fp_el,
                 && !(env->pstate & PSTATE_TCO)
                 && (sctlr & (el == 0 ? SCTLR_TCF0 : SCTLR_TCF))) {
                 DP_TBFLAG_A64(flags, MTE_ACTIVE, 1);
+                if (!EX_TBFLAG_A64(flags, UNPRIV)) {
+                    /*
+                     * In non-unpriv contexts (eg EL0), unpriv load/stores
+                     * act like normal ones; duplicate the MTE info to
+                     * avoid translate-a64.c having to check UNPRIV to see
+                     * whether it is OK to index into MTE_ACTIVE[].
+                     */
+                    DP_TBFLAG_A64(flags, MTE0_ACTIVE, 1);
+                }
             }
         }
         /* And again for unprivileged accesses, if required.  */