linux-user: Split out do_syscall1

There was supposed to be a single point of return for do_syscall
so that tracing works properly.  However, there are a few bugs
in that area.  It is significantly simpler to simply split out
an inner function to enforce this.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20180818190118.12911-3-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

1 files changed, 48 insertions, 29 deletions

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 2e45f854f7..f651024357 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8092,13 +8092,15 @@ static int host_to_target_cpu_mask(const unsigned long *host_mask,
     return 0;
 }
 
-/* do_syscall() should always have a single exit point at the end so
-   that actions, such as logging of syscall results, can be performed.
-   All errnos that do_syscall() returns must be -TARGET_<errcode>. */
-abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
-                    abi_long arg2, abi_long arg3, abi_long arg4,
-                    abi_long arg5, abi_long arg6, abi_long arg7,
-                    abi_long arg8)
+/* This is an internal helper for do_syscall so that it is easier
+ * to have a single return point, so that actions, such as logging
+ * of syscall results, can be performed.
+ * All errnos that do_syscall() returns must be -TARGET_<errcode>.
+ */
+static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
+                            abi_long arg2, abi_long arg3, abi_long arg4,
+                            abi_long arg5, abi_long arg6, abi_long arg7,
+                            abi_long arg8)
 {
     CPUState *cpu = ENV_GET_CPU(cpu_env);
     abi_long ret;
@@ -8113,25 +8115,6 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
 #endif
     void *p;
 
-#if defined(DEBUG_ERESTARTSYS)
-    /* Debug-only code for exercising the syscall-restart code paths
-     * in the per-architecture cpu main loops: restart every syscall
-     * the guest makes once before letting it through.
-     */
-    {
-        static int flag;
-
-        flag = !flag;
-        if (flag) {
-            return -TARGET_ERESTARTSYS;
-        }
-    }
-#endif
-
-    trace_guest_user_syscall(cpu, num, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8);
-    if(do_strace)
-        print_syscall(num, arg1, arg2, arg3, arg4, arg5, arg6);
-
     switch(num) {
     case TARGET_NR_exit:
         /* In old applications this may be used to implement _exit(2).
@@ -12942,11 +12925,47 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         break;
     }
 fail:
-    if(do_strace)
-        print_syscall_ret(num, ret);
-    trace_guest_user_syscall_ret(cpu, num, ret);
     return ret;
 efault:
     ret = -TARGET_EFAULT;
     goto fail;
 }
+
+abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
+                    abi_long arg2, abi_long arg3, abi_long arg4,
+                    abi_long arg5, abi_long arg6, abi_long arg7,
+                    abi_long arg8)
+{
+    CPUState *cpu = ENV_GET_CPU(cpu_env);
+    abi_long ret;
+
+#ifdef DEBUG_ERESTARTSYS
+    /* Debug-only code for exercising the syscall-restart code paths
+     * in the per-architecture cpu main loops: restart every syscall
+     * the guest makes once before letting it through.
+     */
+    {
+        static bool flag;
+        flag = !flag;
+        if (flag) {
+            return -TARGET_ERESTARTSYS;
+        }
+    }
+#endif
+
+    trace_guest_user_syscall(cpu, num, arg1, arg2, arg3, arg4,
+                             arg5, arg6, arg7, arg8);
+
+    if (unlikely(do_strace)) {
+        print_syscall(num, arg1, arg2, arg3, arg4, arg5, arg6);
+        ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4,
+                          arg5, arg6, arg7, arg8);
+        print_syscall_ret(num, ret);
+    } else {
+        ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4,
+                          arg5, arg6, arg7, arg8);
+    }
+
+    trace_guest_user_syscall_ret(cpu, num, ret);
+    return ret;
+}