[MIPS] Fix sigset_t endianess swapping issues in 32-bit compat code.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/linux32.c

@@ -39,6 +39,7 @@
 #include <net/sock.h>
 #include <net/scm.h>
 
+#include <asm/compat-signal.h>
 #include <asm/ipc.h>
 #include <asm/sim.h>
 #include <asm/uaccess.h>
@@ -736,3 +737,49 @@ _sys32_clone(nabi_no_regargs struct pt_regs regs)
 	return do_fork(clone_flags, newsp, &regs, 0,
 	               parent_tidptr, child_tidptr);
 }
+
+/*
+ * Implement the event wait interface for the eventpoll file. It is the kernel
+ * part of the user space epoll_pwait(2).
+ */
+asmlinkage long compat_sys_epoll_pwait(int epfd,
+	struct epoll_event __user *events, int maxevents, int timeout,
+	const compat_sigset_t __user *sigmask, size_t sigsetsize)
+{
+	int error;
+	sigset_t ksigmask, sigsaved;
+
+	/*
+	 * If the caller wants a certain signal mask to be set during the wait,
+	 * we apply it here.
+	 */
+	if (sigmask) {
+		if (sigsetsize != sizeof(sigset_t))
+			return -EINVAL;
+		if (!access_ok(VERIFY_READ, sigmask, sizeof(ksigmask)))
+			return -EFAULT;
+		if (__copy_conv_sigset_from_user(&ksigmask, sigmask))
+			return -EFAULT;
+		sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
+		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
+	}
+
+	error = sys_epoll_wait(epfd, events, maxevents, timeout);
+
+	/*
+	 * If we changed the signal mask, we need to restore the original one.
+	 * In case we've got a signal while waiting, we do not restore the
+	 * signal mask yet, and we allow do_signal() to deliver the signal on
+	 * the way back to userspace, before the signal mask is restored.
+	 */
+	if (sigmask) {
+		if (error == -EINTR) {
+			memcpy(&current->saved_sigmask, &sigsaved,
+				sizeof(sigsaved));
+			set_thread_flag(TIF_RESTORE_SIGMASK);
+		} else
+			sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+	}
+
+	return error;
+}