armv7m: set CFSR.UNDEFINSTR on undefined instructions

When we take an exception for an undefined instruction, set the
appropriate CFSR bit.
Signed-off-by: NMichael Davidsaver <mdavidsaver@gmail.com>
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Message-id: 1485285380-10565-7-git-send-email-peter.maydell@linaro.org
[PMM: tweaked commit message, comment]
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/helper.c

@@ -6072,6 +6072,7 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
     switch (cs->exception_index) {
     case EXCP_UDEF:
         armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE);
+        env->v7m.cfsr |= R_V7M_CFSR_UNDEFINSTR_MASK;
         return;
     case EXCP_SWI:
         /* The PC already points to the next instruction.  */