Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/linux/signal.h b/include/linux/signal.h
index e4d0146..1a5f883 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -11,17 +11,21 @@
 /* for sysctl */
 extern int print_fatal_signals;
 
-static inline void copy_siginfo(struct siginfo *to, const struct siginfo *from)
+static inline void copy_siginfo(kernel_siginfo_t *to,
+				const kernel_siginfo_t *from)
 {
 	memcpy(to, from, sizeof(*to));
 }
 
-static inline void clear_siginfo(struct siginfo *info)
+static inline void clear_siginfo(kernel_siginfo_t *info)
 {
 	memset(info, 0, sizeof(*info));
 }
 
-int copy_siginfo_to_user(struct siginfo __user *to, const struct siginfo *from);
+#define SI_EXPANSION_SIZE (sizeof(struct siginfo) - sizeof(struct kernel_siginfo))
+
+int copy_siginfo_to_user(siginfo_t __user *to, const kernel_siginfo_t *from);
+int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from);
 
 enum siginfo_layout {
 	SIL_KILL,
@@ -125,9 +129,11 @@
 		b3 = b->sig[3]; b2 = b->sig[2];				\
 		r->sig[3] = op(a3, b3);					\
 		r->sig[2] = op(a2, b2);					\
+		/* fall through */					\
 	case 2:								\
 		a1 = a->sig[1]; b1 = b->sig[1];				\
 		r->sig[1] = op(a1, b1);					\
+		/* fall through */					\
 	case 1:								\
 		a0 = a->sig[0]; b0 = b->sig[0];				\
 		r->sig[0] = op(a0, b0);					\
@@ -157,7 +163,9 @@
 	switch (_NSIG_WORDS) {						\
 	case 4:	set->sig[3] = op(set->sig[3]);				\
 		set->sig[2] = op(set->sig[2]);				\
+		/* fall through */					\
 	case 2:	set->sig[1] = op(set->sig[1]);				\
+		/* fall through */					\
 	case 1:	set->sig[0] = op(set->sig[0]);				\
 		    break;						\
 	default:							\
@@ -178,6 +186,7 @@
 		memset(set, 0, sizeof(sigset_t));
 		break;
 	case 2: set->sig[1] = 0;
+		/* fall through */
 	case 1:	set->sig[0] = 0;
 		break;
 	}
@@ -190,6 +199,7 @@
 		memset(set, -1, sizeof(sigset_t));
 		break;
 	case 2: set->sig[1] = -1;
+		/* fall through */
 	case 1:	set->sig[0] = -1;
 		break;
 	}
@@ -257,11 +267,11 @@
 enum pid_type;
 
 extern int next_signal(struct sigpending *pending, sigset_t *mask);
-extern int do_send_sig_info(int sig, struct siginfo *info,
+extern int do_send_sig_info(int sig, struct kernel_siginfo *info,
 				struct task_struct *p, enum pid_type type);
-extern int group_send_sig_info(int sig, struct siginfo *info,
+extern int group_send_sig_info(int sig, struct kernel_siginfo *info,
 			       struct task_struct *p, enum pid_type type);
-extern int __group_send_sig_info(int, struct siginfo *, struct task_struct *);
+extern int __group_send_sig_info(int, struct kernel_siginfo *, struct task_struct *);
 extern int sigprocmask(int, sigset_t *, sigset_t *);
 extern void set_current_blocked(sigset_t *);
 extern void __set_current_blocked(const sigset_t *);
@@ -272,6 +282,9 @@
 extern void exit_signals(struct task_struct *tsk);
 extern void kernel_sigaction(int, __sighandler_t);
 
+#define SIG_KTHREAD ((__force __sighandler_t)2)
+#define SIG_KTHREAD_KERNEL ((__force __sighandler_t)3)
+
 static inline void allow_signal(int sig)
 {
 	/*
@@ -279,7 +292,17 @@
 	 * know it'll be handled, so that they don't get converted to
 	 * SIGKILL or just silently dropped.
 	 */
-	kernel_sigaction(sig, (__force __sighandler_t)2);
+	kernel_sigaction(sig, SIG_KTHREAD);
+}
+
+static inline void allow_kernel_signal(int sig)
+{
+	/*
+	 * Kernel threads handle their own signals. Let the signal code
+	 * know signals sent by the kernel will be handled, so that they
+	 * don't get silently dropped.
+	 */
+	kernel_sigaction(sig, SIG_KTHREAD_KERNEL);
 }
 
 static inline void disallow_signal(int sig)
@@ -378,7 +401,7 @@
 #endif
 
 #define siginmask(sig, mask) \
-	((sig) < SIGRTMIN && (rt_sigmask(sig) & (mask)))
+	((sig) > 0 && (sig) < SIGRTMIN && (rt_sigmask(sig) & (mask)))
 
 #define SIG_KERNEL_ONLY_MASK (\
 	rt_sigmask(SIGKILL)   |  rt_sigmask(SIGSTOP))