1 files changed, 125 insertions, 0 deletions
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 1474905..3fa0fab 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -243,6 +243,131 @@ extern int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
 
 extern struct kmem_cache *sighand_cachep;
 
+/*
+ * In POSIX a signal is sent either to a specific thread (Linux task)
+ * or to the process as a whole (Linux thread group).  How the signal
+ * is sent determines whether it's to one thread or the whole group,
+ * which determines which signal mask(s) are involved in blocking it
+ * from being delivered until later.  When the signal is delivered,
+ * either it's caught or ignored by a user handler or it has a default
+ * effect that applies to the whole thread group (POSIX process).
+ *
+ * The possible effects an unblocked signal set to SIG_DFL can have are:
+ *   ignore	- Nothing Happens
+ *   terminate	- kill the process, i.e. all threads in the group,
+ * 		  similar to exit_group.  The group leader (only) reports
+ *		  WIFSIGNALED status to its parent.
+ *   coredump	- write a core dump file describing all threads using
+ *		  the same mm and then kill all those threads
+ *   stop 	- stop all the threads in the group, i.e. TASK_STOPPED state
+ *
+ * SIGKILL and SIGSTOP cannot be caught, blocked, or ignored.
+ * Other signals when not blocked and set to SIG_DFL behaves as follows.
+ * The job control signals also have other special effects.
+ *
+ *	+--------------------+------------------+
+ *	|  POSIX signal      |  default action  |
+ *	+--------------------+------------------+
+ *	|  SIGHUP            |  terminate	|
+ *	|  SIGINT            |	terminate	|
+ *	|  SIGQUIT           |	coredump 	|
+ *	|  SIGILL            |	coredump 	|
+ *	|  SIGTRAP           |	coredump 	|
+ *	|  SIGABRT/SIGIOT    |	coredump 	|
+ *	|  SIGBUS            |	coredump 	|
+ *	|  SIGFPE            |	coredump 	|
+ *	|  SIGKILL           |	terminate(+)	|
+ *	|  SIGUSR1           |	terminate	|
+ *	|  SIGSEGV           |	coredump 	|
+ *	|  SIGUSR2           |	terminate	|
+ *	|  SIGPIPE           |	terminate	|
+ *	|  SIGALRM           |	terminate	|
+ *	|  SIGTERM           |	terminate	|
+ *	|  SIGCHLD           |	ignore   	|
+ *	|  SIGCONT           |	ignore(*)	|
+ *	|  SIGSTOP           |	stop(*)(+)  	|
+ *	|  SIGTSTP           |	stop(*)  	|
+ *	|  SIGTTIN           |	stop(*)  	|
+ *	|  SIGTTOU           |	stop(*)  	|
+ *	|  SIGURG            |	ignore   	|
+ *	|  SIGXCPU           |	coredump 	|
+ *	|  SIGXFSZ           |	coredump 	|
+ *	|  SIGVTALRM         |	terminate	|
+ *	|  SIGPROF           |	terminate	|
+ *	|  SIGPOLL/SIGIO     |	terminate	|
+ *	|  SIGSYS/SIGUNUSED  |	coredump 	|
+ *	|  SIGSTKFLT         |	terminate	|
+ *	|  SIGWINCH          |	ignore   	|
+ *	|  SIGPWR            |	terminate	|
+ *	|  SIGRTMIN-SIGRTMAX |	terminate       |
+ *	+--------------------+------------------+
+ *	|  non-POSIX signal  |  default action  |
+ *	+--------------------+------------------+
+ *	|  SIGEMT            |  coredump	|
+ *	+--------------------+------------------+
+ *
+ * (+) For SIGKILL and SIGSTOP the action is "always", not just "default".
+ * (*) Special job control effects:
+ * When SIGCONT is sent, it resumes the process (all threads in the group)
+ * from TASK_STOPPED state and also clears any pending/queued stop signals
+ * (any of those marked with "stop(*)").  This happens regardless of blocking,
+ * catching, or ignoring SIGCONT.  When any stop signal is sent, it clears
+ * any pending/queued SIGCONT signals; this happens regardless of blocking,
+ * catching, or ignored the stop signal, though (except for SIGSTOP) the
+ * default action of stopping the process may happen later or never.
+ */
+
+#ifdef SIGEMT
+#define SIGEMT_MASK	rt_sigmask(SIGEMT)
+#else
+#define SIGEMT_MASK	0
+#endif
+
+#if SIGRTMIN > BITS_PER_LONG
+#define rt_sigmask(sig)	(1ULL << ((sig)-1))
+#else
+#define rt_sigmask(sig)	sigmask(sig)
+#endif
+#define siginmask(sig, mask) (rt_sigmask(sig) & (mask))
+
+#define SIG_KERNEL_ONLY_MASK (\
+	rt_sigmask(SIGKILL)   |  rt_sigmask(SIGSTOP))
+
+#define SIG_KERNEL_STOP_MASK (\
+	rt_sigmask(SIGSTOP)   |  rt_sigmask(SIGTSTP)   | \
+	rt_sigmask(SIGTTIN)   |  rt_sigmask(SIGTTOU)   )
+
+#define SIG_KERNEL_COREDUMP_MASK (\
+        rt_sigmask(SIGQUIT)   |  rt_sigmask(SIGILL)    | \
+	rt_sigmask(SIGTRAP)   |  rt_sigmask(SIGABRT)   | \
+        rt_sigmask(SIGFPE)    |  rt_sigmask(SIGSEGV)   | \
+	rt_sigmask(SIGBUS)    |  rt_sigmask(SIGSYS)    | \
+        rt_sigmask(SIGXCPU)   |  rt_sigmask(SIGXFSZ)   | \
+	SIGEMT_MASK				       )
+
+#define SIG_KERNEL_IGNORE_MASK (\
+        rt_sigmask(SIGCONT)   |  rt_sigmask(SIGCHLD)   | \
+	rt_sigmask(SIGWINCH)  |  rt_sigmask(SIGURG)    )
+
+#define sig_kernel_only(sig) \
+	(((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_ONLY_MASK))
+#define sig_kernel_coredump(sig) \
+	(((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_COREDUMP_MASK))
+#define sig_kernel_ignore(sig) \
+	(((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_IGNORE_MASK))
+#define sig_kernel_stop(sig) \
+	(((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_STOP_MASK))
+
+#define sig_needs_tasklist(sig)	((sig) == SIGCONT)
+
+#define sig_user_defined(t, signr) \
+	(((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_DFL) &&	\
+	 ((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_IGN))
+
+#define sig_fatal(t, signr) \
+	(!siginmask(signr, SIG_KERNEL_IGNORE_MASK|SIG_KERNEL_STOP_MASK) && \
+	 (t)->sighand->action[(signr)-1].sa.sa_handler == SIG_DFL)
+
 #endif /* __KERNEL__ */
 
 #endif /* _LINUX_SIGNAL_H */