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

Update the SPARC main loop and sigreturn code:
 * on TARGET_ERESTARTSYS, wind guest PC backwards to repeat syscall insn
 * set all guest CPU state within signal.c code on sigreturn
 * handle TARGET_QEMU_ESIGRETURN in the main loop as the indication
   that the main loop should not touch any guest CPU state

Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Message-id: 1441497448-32489-9-git-send-email-T.E.Baldwin99@members.leeds.ac.uk
[PMM: Commit message tweaks; drop TARGET_USE_ERESTARTSYS define]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

linux-user/main.c

@@ -1376,6 +1376,9 @@ void cpu_loop (CPUSPARCState *env)
                               env->regwptr[2], env->regwptr[3],
                               env->regwptr[4], env->regwptr[5],
                               0, 0);
+            if (ret == -TARGET_ERESTARTSYS || ret == -TARGET_QEMU_ESIGRETURN) {
+                break;
+            }
             if ((abi_ulong)ret >= (abi_ulong)(-515)) {
 #if defined(TARGET_SPARC64) && !defined(TARGET_ABI32)
                 env->xcc |= PSR_CARRY;

linux-user/signal.c

@@ -2449,7 +2449,7 @@ long do_sigreturn(CPUSPARCState *env)
         goto segv_and_exit;
     }
     unlock_user_struct(sf, sf_addr, 0);
-    return env->regwptr[0];
+    return -TARGET_QEMU_ESIGRETURN;
 
 segv_and_exit:
     unlock_user_struct(sf, sf_addr, 0);

linux-user/sparc/target_signal.h

@@ -33,4 +33,5 @@ static inline abi_ulong get_sp_from_cpustate(CPUSPARCState *state)
     return state->regwptr[UREG_FP];
 }
 
+
 #endif /* TARGET_SIGNAL_H */

linux-user/sparc64/target_signal.h

@@ -33,4 +33,5 @@ static inline abi_ulong get_sp_from_cpustate(CPUSPARCState *state)
     return state->regwptr[UREG_FP];
 }
 
+
 #endif /* TARGET_SIGNAL_H */