Implement SA_SIGINFO for i386. Thanks to Bruce Evans for much more

than a review, this was a nice puzzle.

This is supposed to be binary and source compatible with older
applications that access the old FreeBSD-style three arguments to a
signal handler.

Except those applications that access hidden signal handler arguments
bejond the documented third one. If you have applications that do,
please let me know so that we take the opportunity to provide the
functionality they need in a documented manner.

Also except application that use 'struct sigframe' directly. You need
to recompile gdb and doscmd. `make world` is recommended.

Example program that demonstrates how SA_SIGINFO and old-style FreeBSD
handlers (with their three args) may be used in the same process is at
http://www3.cons.org/tmp/fbsd-siginfo.c

Programs that use the old FreeBSD-style three arguments are easy to
change to SA_SIGINFO (although they don't need to, since the old style
will still work):

  Old args to signal handler:
    void handler_sn(int sig, int code, struct sigcontext *scp)

  New args:
    void handler_si(int sig, siginfo_t *si, void *third)
  where:
    old:code == new:second->si_code
    old:scp == &(new:si->si_scp)     /* Passed by value! */

The latter is also pointed to by new:third, but accessing via
si->si_scp is preferred because it is type-save.

FreeBSD implementation notes:
- This is just the framework to make the interface POSIX compatible.
  For now, no additional functionality is provided. This is supposed
  to happen now, starting with floating point values.
- We don't use 'sigcontext_t.si_value' for now (POSIX meant it for
  realtime-related values).
- Documentation will be updated when new functionality is added and
  the exact arguments passed are determined. The comments in
  sys/signal.h are meant to be useful.

Reviewed by:	BDE

1 files changed, 32 insertions, 8 deletions

diff --git a/sys/amd64/include/frame.h b/sys/amd64/include/frame.h
index 5c0dcda..f339f01 100644
--- a/sys/amd64/include/frame.h
+++ b/sys/amd64/include/frame.h
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)frame.h	5.2 (Berkeley) 1/18/91
- *	$Id: frame.h,v 1.16 1999/04/28 01:03:59 luoqi Exp $
+ *	$Id: frame.h,v 1.17 1999/05/11 16:29:01 luoqi Exp $
  */
 
 #ifndef _MACHINE_FRAME_H_
@@ -158,15 +158,39 @@ struct clockframe {
 };
 
 /*
- * Signal frame
+ * Signal frame, arguments passed to application signal handlers.
  */
 struct sigframe {
-	int	sf_signum;
-	int	sf_code;
-	struct	sigcontext *sf_scp;
-	char	*sf_addr;
-	sig_t	sf_handler;
-	struct	sigcontext sf_sc;
+	/* 
+	 * The first three members may be used by applications.
+	 */
+
+	register_t sf_signum;
+
+	/* 
+	 * Either 'int' for old-style FreeBSD handler or 'siginfo_t *'
+	 * pointing to sf_siginfo for SA_SIGINFO handlers. 
+	 */
+	register_t sf_arg2;
+
+	/* Points to sf_siginfo.si_sc. */
+	register_t sf_scp;
+
+	/* 
+	 * The following arguments are not constrained  by the 
+	 * function call protocol.
+	 * Applications are not supposed to access these members,
+	 * except using the pointers we provide in the first three
+	 * arguments. 
+	 */
+	char    *sf_addr;
+	union {
+		__siginfohandler_t *sf_action;
+		__sighandler_t     *sf_handler;
+	} sf_ahu;
+
+	/* In the SA_SIGINFO case, sf_arg2 points here. */
+	siginfo_t  sf_siginfo;
 };
 
 int	kdb_trap __P((int, int, struct trapframe *));