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

Update the 32-bit and 64-bit ARM 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: NTimothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Message-id: 1441497448-32489-6-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/arm/target_signal.h

@@ -26,4 +26,5 @@ static inline abi_ulong get_sp_from_cpustate(CPUARMState *state)
    return state->regs[13];
 }
 
+
 #endif /* TARGET_SIGNAL_H */

linux-user/main.c

@@ -727,6 +727,7 @@ void cpu_loop(CPUARMState *env)
     unsigned int n, insn;
     target_siginfo_t info;
     uint32_t addr;
+    abi_ulong ret;
 
     for(;;) {
         cpu_exec_start(cs);
@@ -865,15 +866,20 @@ void cpu_loop(CPUARMState *env)
                             break;
                         }
                     } else {
-                        env->regs[0] = do_syscall(env,
-                                                  n,
-                                                  env->regs[0],
-                                                  env->regs[1],
-                                                  env->regs[2],
-                                                  env->regs[3],
-                                                  env->regs[4],
-                                                  env->regs[5],
-                                                  0, 0);
+                        ret = do_syscall(env,
+                                         n,
+                                         env->regs[0],
+                                         env->regs[1],
+                                         env->regs[2],
+                                         env->regs[3],
+                                         env->regs[4],
+                                         env->regs[5],
+                                         0, 0);
+                        if (ret == -TARGET_ERESTARTSYS) {
+                            env->regs[15] -= env->thumb ? 2 : 4;
+                        } else if (ret != -TARGET_QEMU_ESIGRETURN) {
+                            env->regs[0] = ret;
+                        }
                     }
                 } else {
                     goto error;
@@ -1056,6 +1062,7 @@ void cpu_loop(CPUARMState *env)
 {
     CPUState *cs = CPU(arm_env_get_cpu(env));
     int trapnr, sig;
+    abi_long ret;
     target_siginfo_t info;
 
     for (;;) {
@@ -1065,15 +1072,20 @@ void cpu_loop(CPUARMState *env)
 
         switch (trapnr) {
         case EXCP_SWI:
-            env->xregs[0] = do_syscall(env,
-                                       env->xregs[8],
-                                       env->xregs[0],
-                                       env->xregs[1],
-                                       env->xregs[2],
-                                       env->xregs[3],
-                                       env->xregs[4],
-                                       env->xregs[5],
-                                       0, 0);
+            ret = do_syscall(env,
+                             env->xregs[8],
+                             env->xregs[0],
+                             env->xregs[1],
+                             env->xregs[2],
+                             env->xregs[3],
+                             env->xregs[4],
+                             env->xregs[5],
+                             0, 0);
+            if (ret == -TARGET_ERESTARTSYS) {
+                env->pc -= 4;
+            } else if (ret != -TARGET_QEMU_ESIGRETURN) {
+                env->xregs[0] = ret;
+            }
             break;
         case EXCP_INTERRUPT:
             /* just indicate that signals should be handled asap */

linux-user/signal.c

@@ -1390,7 +1390,7 @@ long do_rt_sigreturn(CPUARMState *env)
     }
 
     unlock_user_struct(frame, frame_addr, 0);
-    return env->xregs[0];
+    return -TARGET_QEMU_ESIGRETURN;
 
  badframe:
     unlock_user_struct(frame, frame_addr, 0);
@@ -1902,7 +1902,7 @@ static long do_sigreturn_v1(CPUARMState *env)
         send_sig(SIGTRAP, current, 1);
 #endif
     unlock_user_struct(frame, frame_addr, 0);
-    return env->regs[0];
+    return -TARGET_QEMU_ESIGRETURN;
 
 badframe:
     force_sig(TARGET_SIGSEGV /* , current */);
@@ -2028,7 +2028,7 @@ static long do_sigreturn_v2(CPUARMState *env)
     }
 
     unlock_user_struct(frame, frame_addr, 0);
-    return env->regs[0];
+    return -TARGET_QEMU_ESIGRETURN;
 
 badframe:
     unlock_user_struct(frame, frame_addr, 0);
@@ -2082,7 +2082,7 @@ static long do_rt_sigreturn_v1(CPUARMState *env)
         send_sig(SIGTRAP, current, 1);
 #endif
     unlock_user_struct(frame, frame_addr, 0);
-    return env->regs[0];
+    return -TARGET_QEMU_ESIGRETURN;
 
 badframe:
     unlock_user_struct(frame, frame_addr, 0);
@@ -2115,7 +2115,7 @@ static long do_rt_sigreturn_v2(CPUARMState *env)
     }
 
     unlock_user_struct(frame, frame_addr, 0);
-    return env->regs[0];
+    return -TARGET_QEMU_ESIGRETURN;
 
 badframe:
     unlock_user_struct(frame, frame_addr, 0);