linux-user: fix getrusage and wait4 failures with invalid rusage struct

Implementations of system calls getrusage and wait4 have not previously
handled correctly cases when incorrect address of struct rusage is
passed.
This change makes sure return values are correctly set for these cases.
Signed-off-by: NPetar Jovanovic <petar.jovanovic@imgtec.com>
Signed-off-by: NRiku Voipio <riku.voipio@linaro.org>

linux-user/syscall.c

@@ -6243,7 +6243,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
             struct rusage rusage;
             ret = get_errno(getrusage(arg1, &rusage));
             if (!is_error(ret)) {
-                host_to_target_rusage(arg2, &rusage);
+                ret = host_to_target_rusage(arg2, &rusage);
             }
         }
         break;
@@ -6908,6 +6908,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
             abi_long status_ptr = arg2;
             struct rusage rusage, *rusage_ptr;
             abi_ulong target_rusage = arg4;
+            abi_long rusage_err;
             if (target_rusage)
                 rusage_ptr = &rusage;
             else
@@ -6919,8 +6920,12 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
                     if (put_user_s32(status, status_ptr))
                         goto efault;
                 }
-                if (target_rusage)
-                    host_to_target_rusage(target_rusage, &rusage);
+                if (target_rusage) {
+                    rusage_err = host_to_target_rusage(target_rusage, &rusage);
+                    if (rusage_err) {
+                        ret = rusage_err;
+                    }
+                }
             }
         }
         break;