linux-user: Support for restarting system calls for M68K targets

Update the M68K 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: 1441497448-32489-32-git-send-email-T.E.Baldwin99@members.leeds.ac.uk
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: tweak commit message; drop TARGET_USE_ERESTARTSYS define]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

3 files changed, 24 insertions, 21 deletions

diff --git a/linux-user/m68k/target_signal.h b/linux-user/m68k/target_signal.h
index 479758a421..9deaa89c80 100644
--- a/linux-user/m68k/target_signal.h
+++ b/linux-user/m68k/target_signal.h
@@ -26,4 +26,5 @@ static inline abi_ulong get_sp_from_cpustate(CPUM68KState *state)
     return state->aregs[7];
 }
 
+
 #endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/main.c b/linux-user/main.c
index 6a0be7db1c..58dc91ced5 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -3086,18 +3086,24 @@ void cpu_loop(CPUM68KState *env)
             break;
         case EXCP_TRAP0:
             {
+                abi_long ret;
                 ts->sim_syscalls = 0;
                 n = env->dregs[0];
                 env->pc += 2;
-                env->dregs[0] = do_syscall(env,
-                                          n,
-                                          env->dregs[1],
-                                          env->dregs[2],
-                                          env->dregs[3],
-                                          env->dregs[4],
-                                          env->dregs[5],
-                                          env->aregs[0],
-                                          0, 0);
+                ret = do_syscall(env,
+                                 n,
+                                 env->dregs[1],
+                                 env->dregs[2],
+                                 env->dregs[3],
+                                 env->dregs[4],
+                                 env->dregs[5],
+                                 env->aregs[0],
+                                 0, 0);
+                if (ret == -TARGET_ERESTARTSYS) {
+                    env->pc -= 2;
+                } else if (ret != -TARGET_QEMU_ESIGRETURN) {
+                    env->dregs[0] = ret;
+                }
             }
             break;
         case EXCP_INTERRUPT:
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 559e7640a5..3eea6b7981 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -5009,19 +5009,18 @@ static void setup_sigcontext(struct target_sigcontext *sc, CPUM68KState *env,
 }
 
 static void
-restore_sigcontext(CPUM68KState *env, struct target_sigcontext *sc, int *pd0)
+restore_sigcontext(CPUM68KState *env, struct target_sigcontext *sc)
 {
     int temp;
 
     __get_user(env->aregs[7], &sc->sc_usp);
+    __get_user(env->dregs[0], &sc->sc_d0);
     __get_user(env->dregs[1], &sc->sc_d1);
     __get_user(env->aregs[0], &sc->sc_a0);
     __get_user(env->aregs[1], &sc->sc_a1);
     __get_user(env->pc, &sc->sc_pc);
     __get_user(temp, &sc->sc_sr);
     env->sr = (env->sr & 0xff00) | (temp & 0xff);
-
-    *pd0 = tswapl(sc->sc_d0);
 }
 
 /*
@@ -5120,8 +5119,7 @@ static inline int target_rt_setup_ucontext(struct target_ucontext *uc,
 }
 
 static inline int target_rt_restore_ucontext(CPUM68KState *env,
-                                             struct target_ucontext *uc,
-                                             int *pd0)
+                                             struct target_ucontext *uc)
 {
     int temp;
     target_greg_t *gregs = uc->tuc_mcontext.gregs;
@@ -5151,7 +5149,6 @@ static inline int target_rt_restore_ucontext(CPUM68KState *env,
     __get_user(temp, &gregs[17]);
     env->sr = (env->sr & 0xff00) | (temp & 0xff);
 
-    *pd0 = env->dregs[0];
     return 0;
 
 badframe:
@@ -5238,7 +5235,7 @@ long do_sigreturn(CPUM68KState *env)
     abi_ulong frame_addr = env->aregs[7] - 4;
     target_sigset_t target_set;
     sigset_t set;
-    int d0, i;
+    int i;
 
     trace_user_do_sigreturn(env, frame_addr);
     if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1))
@@ -5257,10 +5254,10 @@ long do_sigreturn(CPUM68KState *env)
 
     /* restore registers */
 
-    restore_sigcontext(env, &frame->sc, &d0);
+    restore_sigcontext(env, &frame->sc);
 
     unlock_user_struct(frame, frame_addr, 0);
-    return d0;
+    return -TARGET_QEMU_ESIGRETURN;
 
 badframe:
     force_sig(TARGET_SIGSEGV);
@@ -5273,7 +5270,6 @@ long do_rt_sigreturn(CPUM68KState *env)
     abi_ulong frame_addr = env->aregs[7] - 4;
     target_sigset_t target_set;
     sigset_t set;
-    int d0;
 
     trace_user_do_rt_sigreturn(env, frame_addr);
     if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1))
@@ -5284,7 +5280,7 @@ long do_rt_sigreturn(CPUM68KState *env)
 
     /* restore registers */
 
-    if (target_rt_restore_ucontext(env, &frame->uc, &d0))
+    if (target_rt_restore_ucontext(env, &frame->uc))
         goto badframe;
 
     if (do_sigaltstack(frame_addr +
@@ -5293,7 +5289,7 @@ long do_rt_sigreturn(CPUM68KState *env)
         goto badframe;
 
     unlock_user_struct(frame, frame_addr, 0);
-    return d0;
+    return -TARGET_QEMU_ESIGRETURN;
 
 badframe:
     unlock_user_struct(frame, frame_addr, 0);