Split 4.x and 5.x signal handling so that we can keep 4.x signal

handling clean and functional as 5.x evolves.  This allows some of the
nasty bandaids in the 5.x codepaths to be unwound.

Encapsulate 4.x signal handling under COMPAT_FREEBSD4 (there is an
anti-foot-shooting measure in place, 5.x folks need this for a while) and
finish encapsulating the older stuff under COMPAT_43.  Since the ancient
stuff is required on alpha (longjmp(3) passes a 'struct osigcontext *'
to the current sigreturn(2), instead of the 'ucontext_t *' that sigreturn
is supposed to take), add a compile time check to prevent foot shooting
there too.  Add uniform COMPAT_43 stubs for ia64/sparc64/powerpc.

Tested on: i386, alpha, ia64.  Compiled on sparc64 (a few days ago).
Approved by: re

4 files changed, 54 insertions, 4 deletions

diff --git a/sys/i386/include/md_var.h b/sys/i386/include/md_var.h
index f449c04..9fa3968 100644
--- a/sys/i386/include/md_var.h
+++ b/sys/i386/include/md_var.h
@@ -56,7 +56,13 @@ extern	int	need_post_dma_flush;
 #endif
 extern	void	(*ovbcopy_vector)(const void *from, void *to, size_t len);
 extern	char	sigcode[];
-extern	int	szsigcode, szosigcode;
+extern	int	szsigcode;
+#ifdef COMPAT_FREEBSD4
+extern	int	szfreebsd4_sigcode;
+#endif
+#ifdef COMPAT_43
+extern	int	szosigcode;
+#endif
 
 typedef void alias_for_inthand_t(u_int cs, u_int ef, u_int esp, u_int ss);
 struct	thread;
diff --git a/sys/i386/include/sigframe.h b/sys/i386/include/sigframe.h
index 947743d..98be731 100644
--- a/sys/i386/include/sigframe.h
+++ b/sys/i386/include/sigframe.h
@@ -35,6 +35,7 @@
  * Signal frames, arguments passed to application signal handlers.
  */
 #ifdef _KERNEL
+#ifdef COMPAT_43
 struct osigframe {
 	/*
 	 * The first four members may be used by applications.
@@ -70,6 +71,23 @@ struct osigframe {
 	osiginfo_t	sf_siginfo;
 };
 #endif
+#ifdef COMPAT_FREEBSD4
+/* FreeBSD 4.x */
+struct sigframe4 {
+	register_t	sf_signum;
+	register_t	sf_siginfo;	/* code or pointer to sf_si */
+	register_t	sf_ucontext;	/* points to sf_uc */
+	register_t	sf_addr;	/* undocumented 4th arg */
+
+	union {
+		__siginfohandler_t	*sf_action;
+		__sighandler_t		*sf_handler;
+	} sf_ahu;
+	struct ucontext4 sf_uc;		/* = *sf_ucontext */
+	siginfo_t	sf_si;		/* = *sf_siginfo (SA_SIGINFO case) */
+};
+#endif
+#endif
 
 struct sigframe {
 	/*
diff --git a/sys/i386/include/signal.h b/sys/i386/include/signal.h
index 9fcca63..29a9776 100644
--- a/sys/i386/include/signal.h
+++ b/sys/i386/include/signal.h
@@ -60,7 +60,7 @@ typedef int sig_atomic_t;
 /*
  * Only the kernel should need these old type definitions.
  */
-#ifdef _KERNEL
+#if defined(_KERNEL) && defined(COMPAT_43)
 /*
  * Information pushed on stack when a signal is delivered.
  * This is used by the kernel to restore state following
@@ -68,8 +68,6 @@ typedef int sig_atomic_t;
  * to the handler to allow it to restore state properly if
  * a non-standard exit is performed.
  */
-typedef unsigned int osigset_t;
-
 struct osigcontext {
 	int	sc_onstack;		/* sigstack state to restore */
 	osigset_t sc_mask;		/* signal mask to restore */
diff --git a/sys/i386/include/ucontext.h b/sys/i386/include/ucontext.h
index d02959c..af9b4fd 100644
--- a/sys/i386/include/ucontext.h
+++ b/sys/i386/include/ucontext.h
@@ -73,6 +73,34 @@ typedef struct __mcontext {
 } mcontext_t;
 
 #ifdef _KERNEL
+#ifdef COMPAT_FREEBSD4
+/* For 4.x binaries */
+struct mcontext4 {
+	int	mc_onstack;		/* XXX - sigcontext compat. */
+	int	mc_gs;
+	int	mc_fs;
+	int	mc_es;
+	int	mc_ds;
+	int	mc_edi;
+	int	mc_esi;
+	int	mc_ebp;
+	int	mc_isp;
+	int	mc_ebx;
+	int	mc_edx;
+	int	mc_ecx;
+	int	mc_eax;
+	int	mc_trapno;
+	int	mc_err;
+	int	mc_eip;
+	int	mc_cs;
+	int	mc_eflags;
+	int	mc_esp;			/* machine state */
+	int	mc_ss;
+	int	mc_fpregs[28];		/* env87 + fpacc87 + u_long */
+	int	__spare__[17];
+};
+#endif
+
 struct thread;
 
 void	get_mcontext(struct thread *td, mcontext_t *mcp);