linux-user: Support for restarting system calls for PPC targets

Update the PPC main loop code:
 * on TARGET_ERESTARTSYS, wind guest PC backwards to repeat syscall insn

(We already handle TARGET_QEMU_ESIGRETURN.)
Signed-off-by: NTimothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Message-id: 1441497448-32489-8-git-send-email-T.E.Baldwin99@members.leeds.ac.uk
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
[PMM: tweak commit message; drop TARGET_USE_ERESTARTSYS define]
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NRiku Voipio <riku.voipio@linaro.org>

linux-user/main.c

@@ -1987,6 +1987,10 @@ void cpu_loop(CPUPPCState *env)
             ret = do_syscall(env, env->gpr[0], env->gpr[3], env->gpr[4],
                              env->gpr[5], env->gpr[6], env->gpr[7],
                              env->gpr[8], 0, 0);
+            if (ret == -TARGET_ERESTARTSYS) {
+                env->nip -= 4;
+                break;
+            }
             if (ret == (target_ulong)(-TARGET_QEMU_ESIGRETURN)) {
                 /* Returning from a successful sigreturn syscall.
                    Avoid corrupting register state.  */

linux-user/ppc/target_signal.h

@@ -26,4 +26,5 @@ static inline abi_ulong get_sp_from_cpustate(CPUPPCState *state)
     return state->gpr[1];
 }
 
+
 #endif /* TARGET_SIGNAL_H */