linux-user/sh4: Clean env->flags on signal boundaries

If a signal is delivered during the execution of a delay slot,
or a gUSA region, clear those bits from the environment so that
the signal handler does not start in that same state.

Cleaning the bits on signal return is paranoid good sense.
Reviewed-by: NAurelien Jarno <aurelien@aurel32.net>
Signed-off-by: NRichard Henderson <rth@twiddle.net>
Message-Id: <20170718200255.31647-10-rth@twiddle.net>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

linux-user/signal.c

@@ -3549,6 +3549,7 @@ static void restore_sigcontext(CPUSH4State *regs, struct target_sigcontext *sc)
     __get_user(regs->fpul, &sc->sc_fpul);
 
     regs->tra = -1;         /* disable syscall checks */
+    regs->flags &= ~(DELAY_SLOT_MASK | GUSA_MASK);
 }
 
 static void setup_frame(int sig, struct target_sigaction *ka,
@@ -3592,6 +3593,7 @@ static void setup_frame(int sig, struct target_sigaction *ka,
     regs->gregs[5] = 0;
     regs->gregs[6] = frame_addr += offsetof(typeof(*frame), sc);
     regs->pc = (unsigned long) ka->_sa_handler;
+    regs->flags &= ~(DELAY_SLOT_MASK | GUSA_MASK);
 
     unlock_user_struct(frame, frame_addr, 1);
     return;
@@ -3654,6 +3656,7 @@ static void setup_rt_frame(int sig, struct target_sigaction *ka,
     regs->gregs[5] = frame_addr + offsetof(typeof(*frame), info);
     regs->gregs[6] = frame_addr + offsetof(typeof(*frame), uc);
     regs->pc = (unsigned long) ka->_sa_handler;
+    regs->flags &= ~(DELAY_SLOT_MASK | GUSA_MASK);
 
     unlock_user_struct(frame, frame_addr, 1);
     return;