[patch v2] manual: Document more sigaction flags

[DJ Delorie]

Adds documentation for three-argument handler

Adds remainder of the SA_* flags

diff --git a/manual/signal.texi b/manual/signal.texi
index 5c2ba7dae6..0f598dcc7d 100644
--- a/manual/signal.texi
+++ b/manual/signal.texi
@@ -1141,6 +1141,15 @@ This is used in the same way as the @var{action} argument to the
 @code{signal} function.  The value can be @code{SIG_DFL},
 @code{SIG_IGN}, or a function pointer.  @xref{Basic Signal Handling}.
 
+@item void (*sa_sigaction) (int @var{signum}, siginfo_t *@var{info}, void *@var{ucontext})
+This is an alternate to @code{sa_handler} that is used when the
+@code{sa_flags} includes the @code{flag SA_SIGINFO}.  Note that this
+and @code{sa_handler} overlap; only ever set one at a time.
+
+The contents of the @var{info} and @var{ucontext} structures are
+kernel and architecture dependent.  Please see
+@manpageurl{sigaction,2} for details.
+
 @item sigset_t sa_mask
 This specifies a set of signals to be blocked while the handler runs.
 Blocking is explained in @ref{Blocking for Handler}.  Note that the
@@ -1324,6 +1333,24 @@ delivered for both terminated children and stopped children.
 Setting this flag for a signal other than @code{SIGCHLD} has no effect.
 @end deftypevr
 
+@deftypevr Macro int SA_NOCLDWAIT
+This flag is meaningful only for the @code{SIGCHLD} signal.  When the
+flag is set, the terminated child will not wait for the parent to reap
+it, or become a zombie if not reaped.  The child will instead be
+reaped by the kernel immediately on termination, similar to setting
+SIGCHLD to SIG_IGN.
+
+Setting this flag for a signal other than @code{SIGCHLD} has no effect.
+@end deftypevr
+
+@deftypevr Macro int SA_NODEFER
+Normally a signal is added to the signal mask while running its own
+handler; this negates that, so that the same signal can be received
+while it's handler is running.  Note that if the signal is included in
+@code{sa_mask}, it is masked regardless of this flag.  Only useful when
+assigning a function as a signal handler.
+@end deftypevr
+
 @deftypevr Macro int SA_ONSTACK
 @standards{BSD, signal.h}
 If this flag is set for a particular signal number, the system uses the
@@ -1332,6 +1359,12 @@ If a signal with this flag arrives and you have not set a signal stack,
 the normal user stack is used instead, as if the flag had not been set.
 @end deftypevr
 
+@deftypevr Macro int SA_RESETHAND
+Resets the handler for a signal back to it default at the time the
+process spawned, at the moment specified handler function begins.
+I.e. the handler is called once, then the action resets.
+@end deftypevr
+
 @deftypevr Macro int SA_RESTART
 @standards{BSD, signal.h}
 This flag controls what happens when a signal is delivered during
@@ -1347,6 +1380,34 @@ clear, returning from a handler makes the function fail.
 @xref{Interrupted Primitives}.
 @end deftypevr
 
+@deftypevr Macro int SA_SIGINFO
+Indicates that the @code{sa_sigaction} three-argument form of the
+handler should be used in setting up a handler instead of the
+one-argument @code{sa_handler} form.
+@end deftypevr
+
+@deftypevr Macro int SA_UNSUPPORTED
+This flag exists only to probe the kernel to see what flags it
+supports.  Set this flag and any others in the @var{action} when you
+call @code{sigaction}, then call @code{sigaction} again with
+@var{old-action} set and the same signal number. If this flag isn't
+set in oldact's flags, then the kernel is new enough to clear any
+flags that aren't supported, any the flags that remain set there are
+the ones the kernel supports.
+
+Older kernels recorded and reported all the flags whether they were
+supported or not, so will leave the SA_UNSUPPORTED flag set.  Newer
+kernels never ``support'' SA_UNSUPPORTED so seeing if it's cleared is a
+test for a new enough kernel (Linux 5.11 or higher, for example).
+@end deftypevr
+
+@deftypevr Macro int SA_EXPOSE_TAGBITS
+Addresses on some targets use some of their bits as tags instead of
+address bits.  Normally these are stripped off when filling in
+siginfo_t's si_addr field, but if this flag is set, the tag bits are
+left intact instead.
+@end deftypevr
+
 @node Initial Signal Actions
 @subsection Initial Signal Actions
 @cindex initial signal actions