linux-user: Use restrictive mask when calling cpsr_write()

When linux-user code is calling cpsr_write(), use a restrictive
mask to ensure we are limiting the set of CPSR bits we update.
In particular, don't allow the mode bits to be changed.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NSergey Fedorov <serge.fdrv@gmail.com>
Message-id: 1455556977-3644-5-git-send-email-peter.maydell@linaro.org

linux-user/main.c

@@ -4446,7 +4446,8 @@ int main(int argc, char **argv, char **envp)
 #elif defined(TARGET_ARM)
     {
         int i;
-        cpsr_write(env, regs->uregs[16], 0xffffffff, CPSRWriteByInstr);
+        cpsr_write(env, regs->uregs[16], CPSR_USER | CPSR_EXEC,
+                   CPSRWriteByInstr);
         for(i = 0; i < 16; i++) {
             env->regs[i] = regs->uregs[i];
         }

linux-user/signal.c

@@ -1611,7 +1611,7 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
 	env->regs[13] = frame_addr;
 	env->regs[14] = retcode;
 	env->regs[15] = handler & (thumb ? ~1 : ~3);
-        cpsr_write(env, cpsr, 0xffffffff, CPSRWriteByInstr);
+        cpsr_write(env, cpsr, CPSR_IT | CPSR_T, CPSRWriteByInstr);
 }
 
 static abi_ulong *setup_sigframe_v2_vfp(abi_ulong *regspace, CPUARMState *env)