target/arm: Set FSR for BKPT, BRK when raising exception

Now that we have a helper function specifically for the BRK and
BKPT instructions, we can set the exception.fsr there rather
than in arm_cpu_do_interrupt_aarch32(). This allows us to
use our new arm_debug_exception_fsr() helper.

In particular this fixes a bug where we were hardcoding the
short-form IFSR value, which is wrong if the target exception
level has LPAE enabled.

Fixes: https://bugs.launchpad.net/qemu/+bug/1756927
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180320134114.30418-4-peter.maydell@linaro.org

target/arm/helper.c

@@ -7910,7 +7910,6 @@ static void arm_cpu_do_interrupt_aarch32(CPUState *cs)
         offset = 0;
         break;
     case EXCP_BKPT:
-        env->exception.fsr = 2;
         /* Fall through to prefetch abort.  */
     case EXCP_PREFETCH_ABORT:
         A32_BANKED_CURRENT_REG_SET(env, ifsr, env->exception.fsr);

target/arm/op_helper.c

@@ -488,6 +488,8 @@ void HELPER(exception_with_syndrome)(CPUARMState *env, uint32_t excp,
  */
 void HELPER(exception_bkpt_insn)(CPUARMState *env, uint32_t syndrome)
 {
+    /* FSR will only be used if the debug target EL is AArch32. */
+    env->exception.fsr = arm_debug_exception_fsr(env);
     raise_exception(env, EXCP_BKPT, syndrome, arm_debug_target_el(env));
 }