Added simple implementation of epoll_pwait

Golang 1.10.x started using epoll_pwait instead of regular
epoll_wait and the golang-httpserver app does not work anymore.
This patch adds basic implementation of epoll_pwait that returns
error if non-null sigmask was passed otherwise delegates to
epoll_wait.

Signed-off-by: Waldemar Kozaczuk <[email protected]>

linux.cc

@@ -345,6 +345,17 @@ static int pselect6(int nfds, fd_set *readfds, fd_set *writefds,
     return pselect(nfds, readfds, writefds, exceptfds, timeout_ts, NULL);
 }
 
+static int epoll_pwait(int epfd, struct epoll_event *events, int maxevents,
+                       int timeout_ms, void *sig)
+{
+    if(sig) {
+        WARN_ONCE("epoll_pwait(): unimplemented with not-null sigmask\n");
+        errno = ENOSYS;
+        return -1;
+    }
+
+    return epoll_wait(epfd, events, maxevents, timeout_ms);
+}
 
 long syscall(long number, ...)
 {
@@ -405,6 +416,7 @@ long syscall(long number, ...)
     SYSCALL4(pread64, int, void *, size_t, off_t);
     SYSCALL2(ftruncate, int, off_t);
     SYSCALL1(fsync, int);
+    SYSCALL5(epoll_pwait, int, struct epoll_event *, int, int, void*);
     }
 
     debug_always("syscall(): unimplemented system call %d\n", number);