22 files changed, 371 insertions, 55 deletions

diff --git a/sys/alpha/alpha/machdep.c b/sys/alpha/alpha/machdep.c
index 7a4a001..ddf67d7 100644
--- a/sys/alpha/alpha/machdep.c
+++ b/sys/alpha/alpha/machdep.c
@@ -210,7 +210,9 @@ static void freebsd4_sendsig(sig_t catcher, int sig, sigset_t *mask,
     u_long code);
 #endif
 
+static void get_fpcontext(struct thread *td, mcontext_t *mcp);
 static void identifycpu(void);
+static int  set_fpcontext(struct thread *td, const mcontext_t *mcp);
 
 struct kva_md_info kmi;
 
@@ -1405,7 +1407,7 @@ sendsig(sig_t catcher, int sig, sigset_t *mask, u_long code)
 	    frame->tf_regs[FRAME_TRAPARG_A1];
 	sf.sf_uc.uc_mcontext.mc_regs[R_TRAPARG_A2] =
 	    frame->tf_regs[FRAME_TRAPARG_A2];
-	sf.sf_uc.uc_mcontext.mc_format = __UC_REV0_SIGFRAME;
+	sf.sf_uc.uc_mcontext.mc_format = _MC_REV0_SIGFRAME;
 
 	/*
 	 * Allocate and validate space for the signal handler
@@ -1664,13 +1666,15 @@ sigreturn(struct thread *td,
 		return (error);
 	}
 #ifdef COMPAT_43
-	 if (((struct osigcontext*)&uc)->sc_regs[R_ZERO] == 0xACEDBADE)
-		  return osigreturn(td, (struct osigreturn_args *)uap);
+	if (((struct osigcontext*)&uc)->sc_regs[R_ZERO] == 0xACEDBADE)
+		return osigreturn(td, (struct osigreturn_args *)uap);
 #endif
 
 	/*
 	 * Restore the user-supplied information
 	 */
+	if ((error = set_fpcontext(td, &uc.uc_mcontext)) != 0)
+		return (error);
 	set_regs(td, (struct reg *)uc.uc_mcontext.mc_regs);
 	val = (uc.uc_mcontext.mc_regs[R_PS] | ALPHA_PSL_USERSET) &
 	    ~ALPHA_PSL_USERCLR;
@@ -1692,12 +1696,6 @@ sigreturn(struct thread *td,
 	signotify(p);
 	PROC_UNLOCK(p);
 
-	/* XXX ksc.sc_ownedfp ? */
-	alpha_fpstate_drop(td);
-	bcopy((struct fpreg *)uc.uc_mcontext.mc_fpregs,
-	      &td->td_pcb->pcb_fp, sizeof(struct fpreg));
-	td->td_pcb->pcb_fp_control = uc.uc_mcontext.mc_fp_control;
-
 	return (EJUSTRETURN);
 }
 
@@ -2011,6 +2009,133 @@ set_regs(td, regs)
 }
 
 int
+get_mcontext(struct thread *td, mcontext_t *mcp)
+{
+	/*
+	 * Use a trapframe for getsetcontext, so just copy the
+	 * threads trapframe.
+	 */
+	bcopy(&td->td_frame, &mcp->mc_regs, sizeof(td->td_frame));
+
+	/*
+	 * When the thread is the current thread, the user stack pointer
+	 * is not in the PCB; it must be read from the PAL.
+	 */
+	if (td == curthread)
+		mcp->mc_regs[FRAME_SP] = alpha_pal_rdusp();
+
+	mcp->mc_format = _MC_REV0_TRAPFRAME;
+	mcp->mc_onstack = sigonstack(alpha_pal_rdusp()) ? 1 : 0;
+	get_fpcontext(td, mcp);
+	return (0);
+}
+
+int
+set_mcontext(struct thread *td, const mcontext_t *mcp)
+{
+	int ret;
+	unsigned long val;
+
+	if ((mcp->mc_format != _MC_REV0_TRAPFRAME) &&
+	    (mcp->mc_format != _MC_REV0_SIGFRAME))
+		return (EINVAL);
+	else if ((ret = set_fpcontext(td, mcp)) != 0)
+		return (ret);
+
+	if (mcp->mc_format == _MC_REV0_SIGFRAME) {
+		set_regs(td, (struct reg *)&mcp->mc_regs);
+		val = (mcp->mc_regs[R_PS] | ALPHA_PSL_USERSET) &
+		    ~ALPHA_PSL_USERCLR;
+		td->td_frame->tf_regs[FRAME_PS] = val;
+		td->td_frame->tf_regs[FRAME_PC] = mcp->mc_regs[R_PC];
+		td->td_frame->tf_regs[FRAME_FLAGS] = 0;
+		if (td == curthread)
+			alpha_pal_wrusp(mcp->mc_regs[R_SP]);
+
+	} else {
+		if (td == curthread)
+			alpha_pal_wrusp(mcp->mc_regs[FRAME_SP]);
+		/*
+		 * The context is a trapframe, so just copy it over the
+		 * threads frame.
+		 */
+		bcopy(&mcp->mc_regs, &td->td_frame, sizeof(td->td_frame));
+	}
+	return (0);
+}
+
+static void
+get_fpcontext(struct thread *td, mcontext_t *mcp)
+{
+	register_t s;
+
+	s = intr_disable();
+	if ((td->td_md.md_flags & MDTD_FPUSED) == 0) {
+		intr_restore(s);
+		mcp->mc_ownedfp = _MC_FPOWNED_NONE;
+	} else if (PCPU_GET(fpcurthread) == td) {
+		/* See comments in alpha_fpstate_save() regarding FEN. */
+		if (td != curthread)
+			alpha_pal_wrfen(1);
+		/*
+		 * The last field (fpr_cr) of struct fpreg isn't
+		 * included in mc_fpregs, but it immediately follows
+		 * it in mcontext_t.
+		 */
+		savefpstate((struct fpreg *)&mcp->mc_fpregs);
+		if (td != curthread)
+			alpha_pal_wrfen(0);
+		intr_restore(s);
+		mcp->mc_ownedfp = _MC_FPOWNED_FPU;
+	} else {
+		/*
+		 * The thread doesn't own the FPU so get the state from
+		 * the PCB.
+		 */
+		intr_restore(s);
+		bcopy(&td->td_pcb->pcb_fp, &mcp->mc_fpregs,
+		    sizeof(td->td_pcb->pcb_fp));
+		mcp->mc_ownedfp = _MC_FPOWNED_PCB;
+	}
+	/* There's no harm in always doing the following. */
+	mcp->mc_fp_control = td->td_pcb->pcb_fp_control;
+}
+
+static int
+set_fpcontext(struct thread *td, const mcontext_t *mcp)
+{
+	register_t s;
+
+	if (mcp->mc_ownedfp == _MC_FPOWNED_NONE) {
+		/* XXX - Drop fpu state so we get a clean state? */
+		alpha_fpstate_drop(td);
+	}
+	else if ((mcp->mc_ownedfp != _MC_FPOWNED_FPU) &&
+	    (mcp->mc_ownedfp != _MC_FPOWNED_PCB))
+		return (EINVAL);
+	else {
+		s = intr_disable();
+		if (PCPU_GET(fpcurthread) == td) {
+			/*
+			 * The last field (fpr_cr) of struct fpreg isn't
+			 * included in mc_fpregs, but it immediately follows
+			 * it in mcontext_t.
+			 */
+			restorefpstate((struct fpreg *)&mcp->mc_fpregs);
+			intr_restore(s);
+		}
+		else {
+			/* Just save the state in the PCB. */
+			intr_restore(s);
+			bcopy(&mcp->mc_fpregs, &td->td_pcb->pcb_fp,
+			    sizeof (td->td_pcb->pcb_fp));
+		}
+		td->td_pcb->pcb_fp_control = mcp->mc_fp_control;
+	}
+	return (0);
+}
+
+int
 fill_dbregs(struct thread *td, struct dbreg *dbregs)
 {
 
diff --git a/sys/alpha/include/cpu.h b/sys/alpha/include/cpu.h
index 9d05765..0e39182 100644
--- a/sys/alpha/include/cpu.h
+++ b/sys/alpha/include/cpu.h
@@ -115,11 +115,11 @@ void	XentRestart(void);					/* MAGIC */
 void	XentSys(u_int64_t, u_int64_t, u_int64_t);		/* MAGIC */
 void	XentUna(u_int64_t, u_int64_t, u_int64_t);		/* MAGIC */
 void	alpha_init(u_long, u_long, u_long, u_long, u_long);
+void	alpha_fpstate_check(struct thread *td);
+void	alpha_fpstate_drop(struct thread *td);
+void	alpha_fpstate_save(struct thread *td, int write);
+void	alpha_fpstate_switch(struct thread *td);
 int	alpha_pa_access(u_long);
-void	alpha_fpstate_check(struct thread *p);
-void	alpha_fpstate_save(struct thread *p, int write);
-void	alpha_fpstate_drop(struct thread *p);
-void	alpha_fpstate_switch(struct thread *p);
 int	badaddr	(void *, size_t);
 int	badaddr_read(void *, size_t, void *);
 u_int64_t console_restart(u_int64_t, u_int64_t, u_int64_t);
diff --git a/sys/alpha/include/fpu.h b/sys/alpha/include/fpu.h
index 712a1f9..9f4800f 100644
--- a/sys/alpha/include/fpu.h
+++ b/sys/alpha/include/fpu.h
@@ -116,9 +116,7 @@
 	__asm__("trapb")
 
 #ifdef _KERNEL
-
-extern int fp_software_completion(u_int64_t regmask, struct thread *p);
-
+extern int fp_software_completion(u_int64_t regmask, struct thread *td);
 #endif
 
 #endif /* ! _MACHINE_FPU_H_ */
diff --git a/sys/alpha/include/signal.h b/sys/alpha/include/signal.h
index 2a1f17b..37a969e 100644
--- a/sys/alpha/include/signal.h
+++ b/sys/alpha/include/signal.h
@@ -94,10 +94,9 @@ struct sigcontext {
 	unsigned long sc_fpregs[32];	/* FP register set (see above) */
 	unsigned long sc_fpcr;		/* FP control register (see above) */
 	unsigned long sc_fp_control;	/* FP software control word */
-	long	sc_ownedfp;		/* fp has been used */
-	long	sc_xxx1[2];		/* sc_ssize, sc_sbase on DUX */
-	long	sc_xxx2[3];		/* sc_fp_trap_pc, sc_fp_trigger_sum, sc_fp_trigger_inst */
-	long	sc_reserved[2];		/* XXX */
+	long	sc_ownedfp;		/* fp has been used; see mcontext_t */
+	long	sc_format;		/* see mcontext_t */
+	long	sc_spare[6];		/* XXX */
 };
 
 #define	sc_sp	sc_regs[R_SP]
diff --git a/sys/alpha/include/ucontext.h b/sys/alpha/include/ucontext.h
index bfc18df..2c3ed70 100644
--- a/sys/alpha/include/ucontext.h
+++ b/sys/alpha/include/ucontext.h
@@ -43,11 +43,14 @@ typedef struct __mcontext {
 	unsigned long mc_fpregs[32];
 	unsigned long mc_fpcr;
 	unsigned long mc_fp_control;
+#define	_MC_FPOWNED_NONE	0	/* FP state not used */
+#define	_MC_FPOWNED_FPU		1	/* FP state came from FPU */
+#define	_MC_FPOWNED_PCB		2	/* FP state came from PCB */
 	long	mc_ownedfp;
-#define	__UC_REV0_SIGFRAME	1	/* context is a signal frame */
-#define	__UC_REV0_TRAPFRAME	2	/* context is a trap frame */
+#define	_MC_REV0_SIGFRAME	1	/* context is a signal frame */
+#define	_MC_REV0_TRAPFRAME	2	/* context is a trap frame */
 	long	mc_format;
-	long	__spare__[6];
+	long	mc_spare[6];
 } mcontext_t;
 
 #if defined(_KERNEL) && defined(COMPAT_FREEBSD4)
diff --git a/sys/amd64/amd64/fpu.c b/sys/amd64/amd64/fpu.c
index 3395c99..661a698 100644
--- a/sys/amd64/amd64/fpu.c
+++ b/sys/amd64/amd64/fpu.c
@@ -161,14 +161,14 @@ void	stop_emulating(void);
 
 typedef u_char bool_t;
 
+static	void	fpusave(union savefpu *);
+static	void	fpurstor(union savefpu *);
 static	int	npx_attach(device_t dev);
 static	void	npx_identify(driver_t *driver, device_t parent);
 #ifndef SMP
 static	void	npx_intr(void *);
 #endif
 static	int	npx_probe(device_t dev);
-static	void	fpusave(union savefpu *);
-static	void	fpurstor(union savefpu *);
 #ifdef I586_CPU_XXX
 static	long	timezero(const char *funcname,
 		    void (*func)(void *buf, size_t len));
diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 181463e..1aedc3d 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -2317,7 +2317,7 @@ set_fpregs(struct thread *td, struct fpreg *fpregs)
 /*
  * Get machine context.
  */
-void
+int
 get_mcontext(struct thread *td, mcontext_t *mcp)
 {
 	struct trapframe *tp;
@@ -2344,6 +2344,7 @@ get_mcontext(struct thread *td, mcontext_t *mcp)
 	mcp->mc_ss = tp->tf_ss;
 	mcp->mc_len = sizeof(*mcp);
 	get_fpcontext(td, mcp);
+	return (0);
 }
 
 /*
diff --git a/sys/amd64/include/signal.h b/sys/amd64/include/signal.h
index 29a9776..efc7ef0 100644
--- a/sys/amd64/include/signal.h
+++ b/sys/amd64/include/signal.h
@@ -119,7 +119,7 @@ struct sigcontext {
 	int	sc_efl;
 	int	sc_esp;
 	int	sc_ss;
-	int	sc_len;			/* sizeof(struct mcontext_t) */
+	int	sc_len;			/* sizeof(mcontext_t) */
 	/*
 	 * XXX - See <machine/ucontext.h> and <machine/npx.h> for
 	 *       the following fields.
@@ -127,7 +127,7 @@ struct sigcontext {
 	int	sc_fpformat;
 	int	sc_ownedfp;
 	int	sc_spare1[1];
-	int	sc_fpregs[128];
+	int	sc_fpstate[128];
 	int	sc_spare2[8];
 };
 
diff --git a/sys/amd64/include/ucontext.h b/sys/amd64/include/ucontext.h
index af9b4fd..ea6f0b6 100644
--- a/sys/amd64/include/ucontext.h
+++ b/sys/amd64/include/ucontext.h
@@ -38,7 +38,7 @@ typedef struct __mcontext {
 	 * and ucontext_t at the same time.
 	 */
 	int	mc_onstack;		/* XXX - sigcontext compat. */
-	int	mc_gs;
+	int	mc_gs;			/* machine state (trapframe) */
 	int	mc_fs;
 	int	mc_es;
 	int	mc_ds;
@@ -55,7 +55,7 @@ typedef struct __mcontext {
 	int	mc_eip;
 	int	mc_cs;
 	int	mc_eflags;
-	int	mc_esp;			/* machine state */
+	int	mc_esp;
 	int	mc_ss;
 
 	int	mc_len;			/* sizeof(mcontext_t) */
@@ -72,8 +72,7 @@ typedef struct __mcontext {
 	int	mc_spare2[8];
 } mcontext_t;
 
-#ifdef _KERNEL
-#ifdef COMPAT_FREEBSD4
+#if defined(_KERNEL) && defined(COMPAT_FREEBSD4)
 /* For 4.x binaries */
 struct mcontext4 {
 	int	mc_onstack;		/* XXX - sigcontext compat. */
@@ -101,10 +100,4 @@ struct mcontext4 {
 };
 #endif
 
-struct thread;
-
-void	get_mcontext(struct thread *td, mcontext_t *mcp);
-int	set_mcontext(struct thread *td, const mcontext_t *mcp);
-#endif
-
 #endif /* !_MACHINE_UCONTEXT_H_ */
diff --git a/sys/amd64/isa/npx.c b/sys/amd64/isa/npx.c
index 3395c99..661a698 100644
--- a/sys/amd64/isa/npx.c
+++ b/sys/amd64/isa/npx.c
@@ -161,14 +161,14 @@ void	stop_emulating(void);
 
 typedef u_char bool_t;
 
+static	void	fpusave(union savefpu *);
+static	void	fpurstor(union savefpu *);
 static	int	npx_attach(device_t dev);
 static	void	npx_identify(driver_t *driver, device_t parent);
 #ifndef SMP
 static	void	npx_intr(void *);
 #endif
 static	int	npx_probe(device_t dev);
-static	void	fpusave(union savefpu *);
-static	void	fpurstor(union savefpu *);
 #ifdef I586_CPU_XXX
 static	long	timezero(const char *funcname,
 		    void (*func)(void *buf, size_t len));
diff --git a/sys/conf/files b/sys/conf/files
index 300fe54..c562b1b 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -975,6 +975,7 @@ kern/kern_alq.c		optional alq
 kern/kern_clock.c	standard
 kern/kern_condvar.c	standard
 kern/kern_conf.c	standard
+kern/kern_context.c	standard
 kern/kern_descrip.c	standard
 kern/kern_poll.c	optional device_polling
 kern/kern_environment.c	standard
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 181463e..1aedc3d 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -2317,7 +2317,7 @@ set_fpregs(struct thread *td, struct fpreg *fpregs)
 /*
  * Get machine context.
  */
-void
+int
 get_mcontext(struct thread *td, mcontext_t *mcp)
 {
 	struct trapframe *tp;
@@ -2344,6 +2344,7 @@ get_mcontext(struct thread *td, mcontext_t *mcp)
 	mcp->mc_ss = tp->tf_ss;
 	mcp->mc_len = sizeof(*mcp);
 	get_fpcontext(td, mcp);
+	return (0);
 }
 
 /*
diff --git a/sys/i386/include/signal.h b/sys/i386/include/signal.h
index 29a9776..efc7ef0 100644
--- a/sys/i386/include/signal.h
+++ b/sys/i386/include/signal.h
@@ -119,7 +119,7 @@ struct sigcontext {
 	int	sc_efl;
 	int	sc_esp;
 	int	sc_ss;
-	int	sc_len;			/* sizeof(struct mcontext_t) */
+	int	sc_len;			/* sizeof(mcontext_t) */
 	/*
 	 * XXX - See <machine/ucontext.h> and <machine/npx.h> for
 	 *       the following fields.
@@ -127,7 +127,7 @@ struct sigcontext {
 	int	sc_fpformat;
 	int	sc_ownedfp;
 	int	sc_spare1[1];
-	int	sc_fpregs[128];
+	int	sc_fpstate[128];
 	int	sc_spare2[8];
 };
 
diff --git a/sys/i386/include/ucontext.h b/sys/i386/include/ucontext.h
index af9b4fd..ea6f0b6 100644
--- a/sys/i386/include/ucontext.h
+++ b/sys/i386/include/ucontext.h
@@ -38,7 +38,7 @@ typedef struct __mcontext {
 	 * and ucontext_t at the same time.
 	 */
 	int	mc_onstack;		/* XXX - sigcontext compat. */
-	int	mc_gs;
+	int	mc_gs;			/* machine state (trapframe) */
 	int	mc_fs;
 	int	mc_es;
 	int	mc_ds;
@@ -55,7 +55,7 @@ typedef struct __mcontext {
 	int	mc_eip;
 	int	mc_cs;
 	int	mc_eflags;
-	int	mc_esp;			/* machine state */
+	int	mc_esp;
 	int	mc_ss;
 
 	int	mc_len;			/* sizeof(mcontext_t) */
@@ -72,8 +72,7 @@ typedef struct __mcontext {
 	int	mc_spare2[8];
 } mcontext_t;
 
-#ifdef _KERNEL
-#ifdef COMPAT_FREEBSD4
+#if defined(_KERNEL) && defined(COMPAT_FREEBSD4)
 /* For 4.x binaries */
 struct mcontext4 {
 	int	mc_onstack;		/* XXX - sigcontext compat. */
@@ -101,10 +100,4 @@ struct mcontext4 {
 };
 #endif
 
-struct thread;
-
-void	get_mcontext(struct thread *td, mcontext_t *mcp);
-int	set_mcontext(struct thread *td, const mcontext_t *mcp);
-#endif
-
 #endif /* !_MACHINE_UCONTEXT_H_ */
diff --git a/sys/i386/isa/npx.c b/sys/i386/isa/npx.c
index 3395c99..661a698 100644
--- a/sys/i386/isa/npx.c
+++ b/sys/i386/isa/npx.c
@@ -161,14 +161,14 @@ void	stop_emulating(void);
 
 typedef u_char bool_t;
 
+static	void	fpusave(union savefpu *);
+static	void	fpurstor(union savefpu *);
 static	int	npx_attach(device_t dev);
 static	void	npx_identify(driver_t *driver, device_t parent);
 #ifndef SMP
 static	void	npx_intr(void *);
 #endif
 static	int	npx_probe(device_t dev);
-static	void	fpusave(union savefpu *);
-static	void	fpurstor(union savefpu *);
 #ifdef I586_CPU_XXX
 static	long	timezero(const char *funcname,
 		    void (*func)(void *buf, size_t len));
diff --git a/sys/ia64/ia64/machdep.c b/sys/ia64/ia64/machdep.c
index df7dc4a..3bb9e34 100644
--- a/sys/ia64/ia64/machdep.c
+++ b/sys/ia64/ia64/machdep.c
@@ -1038,6 +1038,20 @@ freebsd4_sigreturn(struct thread *td, struct freebsd4_sigreturn_args *uap)
 }
 #endif
 
+int
+get_mcontext(struct thread *td, mcontext_t *mcp)
+{
+
+	return (ENOSYS);
+}
+
+int
+set_mcontext(struct thread *td, const mcontext_t *mcp)
+{
+
+	return (ENOSYS);
+}
+
 /*
  * Machine dependent boot() routine
  */
diff --git a/sys/kern/kern_context.c b/sys/kern/kern_context.c
new file mode 100644
index 0000000..1cc0eac
--- /dev/null
+++ b/sys/kern/kern_context.c
@@ -0,0 +1,134 @@
+/*-
+ * Copyright (c) 2002 Daniel M. Eischen <deischen@freebsd.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+/*
+ * $FreeBSD$
+ */
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/proc.h>
+#include <sys/sysent.h>
+#include <sys/systm.h>
+#include <sys/sysproto.h>
+#include <sys/signalvar.h>
+#include <sys/ucontext.h>
+
+/*
+ * The first two fields of a ucontext_t are the signal mask and
+ * the machine context.  The next field is uc_link; we want to
+ * avoid destroying the link when copying out contexts.
+ */
+#define	UC_COPY_SIZE	(sizeof(sigset_t) + sizeof(mcontext_t))
+
+
+#ifndef _SYS_SYSPROTO_H_
+struct getcontext_args {
+	struct __ucontext *ucp;
+}
+struct setcontext_args {
+	const struct __ucontext_t *ucp;
+}
+struct swapcontext_args {
+	struct __ucontext *oucp;
+	const struct __ucontext_t *ucp;
+}
+#endif
+
+/*
+ * MPSAFE
+ */
+int
+getcontext(struct thread *td, struct getcontext_args *uap)
+{
+	ucontext_t uc;
+	int ret;	
+
+	if (uap->ucp == NULL)
+		ret = EINVAL;
+	else {
+		get_mcontext(td, &uc.uc_mcontext);
+		uc.uc_sigmask = td->td_proc->p_sigmask;
+		ret = copyout(&uc, uap->ucp, UC_COPY_SIZE);
+	}
+	return (ret);
+}
+
+/*
+ * MPSAFE
+ */
+int
+setcontext(struct thread *td, struct setcontext_args *uap)
+{
+	ucontext_t uc;
+	int ret;	
+
+	if (uap->ucp == NULL)
+		ret = EINVAL;
+	else {
+		ret = copyin(uap->ucp, &uc, UC_COPY_SIZE);
+		if (ret == 0) {
+			ret = set_mcontext(td, &uc.uc_mcontext);
+			if (ret == 0) {
+				SIG_CANTMASK(uc.uc_sigmask);
+				PROC_LOCK(td->td_proc);
+				td->td_proc->p_sigmask = uc.uc_sigmask;
+				PROC_UNLOCK(td->td_proc);
+			}
+		}
+	}
+	return (ret);
+}
+
+int
+swapcontext(struct thread *td, struct swapcontext_args *uap)
+{
+	ucontext_t uc;
+	int ret;	
+
+	if (uap->oucp == NULL || uap->ucp == NULL)
+		ret = EINVAL;
+	else {
+		get_mcontext(td, &uc.uc_mcontext);
+		uc.uc_sigmask = td->td_proc->p_sigmask;
+		ret = copyout(&uc, uap->oucp, UC_COPY_SIZE);
+		if (ret == 0) {
+			ret = copyin(uap->ucp, &uc, UC_COPY_SIZE);
+			if (ret == 0) {
+				ret = set_mcontext(td, &uc.uc_mcontext);
+				if (ret == 0) {
+					SIG_CANTMASK(uc.uc_sigmask);
+					PROC_LOCK(td->td_proc);
+					td->td_proc->p_sigmask = uc.uc_sigmask;
+					PROC_UNLOCK(td->td_proc);
+				}
+			}
+		}
+	}
+	return (ret);
+}
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
index 650c65b..a41eb12 100644
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -608,6 +608,10 @@
 418	UNIMPL	BSD	__xstat
 419	UNIMPL	BSD	__xfstat
 420	UNIMPL	BSD	__xlstat
+421	MSTD	BSD	{ int getcontext(struct __ucontext *ucp); }
+422	MSTD	BSD	{ int setcontext(const struct __ucontext *ucp); }
+423	MSTD	BSD	{ int swapcontext(struct __ucontext *oucp, \
+			    const struct __ucontext *ucp); }
 
 ; Please copy any additions and changes to the following compatability tables:
 ; sys/ia64/ia32/syscalls.master  (take a best guess)
diff --git a/sys/powerpc/aim/machdep.c b/sys/powerpc/aim/machdep.c
index a14d966..ffb5070 100644
--- a/sys/powerpc/aim/machdep.c
+++ b/sys/powerpc/aim/machdep.c
@@ -638,6 +638,20 @@ freebsd4_sigreturn(struct thread *td, struct freebsd4_sigreturn_args *uap)
 }
 #endif
 
+int
+get_mcontext(struct thread *td, mcontext_t *mcp)
+{
+
+	return (ENOSYS);
+}
+
+int
+set_mcontext(struct thread *td, const mcontext_t *mcp)
+{
+
+	return (ENOSYS);
+}
+
 void
 cpu_boot(int howto)
 {
diff --git a/sys/powerpc/powerpc/machdep.c b/sys/powerpc/powerpc/machdep.c
index a14d966..ffb5070 100644
--- a/sys/powerpc/powerpc/machdep.c
+++ b/sys/powerpc/powerpc/machdep.c
@@ -638,6 +638,20 @@ freebsd4_sigreturn(struct thread *td, struct freebsd4_sigreturn_args *uap)
 }
 #endif
 
+int
+get_mcontext(struct thread *td, mcontext_t *mcp)
+{
+
+	return (ENOSYS);
+}
+
+int
+set_mcontext(struct thread *td, const mcontext_t *mcp)
+{
+
+	return (ENOSYS);
+}
+
 void
 cpu_boot(int howto)
 {
diff --git a/sys/sparc64/sparc64/machdep.c b/sys/sparc64/sparc64/machdep.c
index 116741b..84cf92a 100644
--- a/sys/sparc64/sparc64/machdep.c
+++ b/sys/sparc64/sparc64/machdep.c
@@ -504,6 +504,20 @@ freebsd4_sigreturn(struct thread *td, struct freebsd4_sigreturn_args *uap)
 }
 #endif
 
+int
+get_mcontext(struct thread *td, mcontext_t *mcp)
+{
+
+	return (ENOSYS);
+}
+
+int
+set_mcontext(struct thread *td, const mcontext_t *mcp)
+{
+
+	return (ENOSYS);
+}
+
 /*
  * Exit the kernel and execute a firmware call that will not return, as
  * specified by the arguments.
diff --git a/sys/sys/ucontext.h b/sys/sys/ucontext.h
index dcce16e..1ea01d5 100644
--- a/sys/sys/ucontext.h
+++ b/sys/sys/ucontext.h
@@ -79,6 +79,14 @@ int	swapcontext(ucontext_t *, const ucontext_t *);
 
 __END_DECLS
 
+#else /* _KERNEL */
+
+struct thread;
+
+/* Machine-dependent functions: */
+int	get_mcontext(struct thread *td, mcontext_t *mcp);
+int	set_mcontext(struct thread *td, const mcontext_t *mcp);
+
 #endif /* !_KERNEL */
 
 #endif /* !_SYS_UCONTEXT_H_ */