- Add support for the ucontext system calls (getcontext, setcontext,

swapcontext, and makecontext).
- Fix VM to not erroneously think the stack segment and data segment have
  collided when a user-space thread invokes brk().
- Add test51 to test ucontext functionality.
- Add man pages for ucontext system calls.

kernel/system/Makefile

@@ -57,7 +57,8 @@ OBJECTS	= \
 	do_sprofile.o \
 	do_cprofile.o \
 	do_profbuf.o \
-	do_vmctl.o
+	do_vmctl.o \
+	do_mcontext.o
 
 build $(SYSTEM):	$(SYSTEM)($(OBJECTS))
 	aal cr $@ *.o

kernel/system/do_mcontext.c

@@ -0,0 +1,94 @@
+/* The kernel calls that are implemented in this file:
+ *   m_type:	SYS_SETMCONTEXT
+ *   m_type:	SYS_GETMCONTEXT
+ *
+ * The parameters for these kernel calls are:
+ *     m1_i1:	PR_ENDPT        # proc endpoint doing call
+ *     m1_p1:	PR_MEM_PTR	# pointer to mcontext structure
+ *
+ */
+
+#include "../system.h"
+#include <string.h>
+#include <machine/mcontext.h>
+
+#if USE_MCONTEXT 
+/*===========================================================================*
+ *			      do_getmcontext				     *
+ *===========================================================================*/
+PUBLIC int do_getmcontext(struct proc * caller, message * m_ptr)
+{
+/* Retrieve machine context of a process */
+
+  register struct proc *rp;
+  int proc_nr, r;
+  mcontext_t mc;
+
+  if (! isokendpt(m_ptr->PR_ENDPT, &proc_nr)) return(EINVAL);
+  if (iskerneln(proc_nr)) return(EPERM);
+  rp = proc_addr(proc_nr);
+
+#if (_MINIX_CHIP == _CHIP_INTEL)
+  if (!(rp->p_misc_flags & MF_FPU_INITIALIZED)) 
+	return(OK);	/* No state to copy */
+#endif
+
+  /* Get the mcontext structure into our address space.  */
+  if ((r = data_copy(m_ptr->PR_ENDPT, (vir_bytes) m_ptr->PR_CTX_PTR, KERNEL,
+		(vir_bytes) &mc, (phys_bytes) sizeof(struct __mcontext))) != OK)
+	return(r);
+
+#if (_MINIX_CHIP == _CHIP_INTEL)
+  /* Copy FPU state */
+  mc.mc_fpu_flags = 0;
+  if (rp->p_misc_flags & MF_FPU_INITIALIZED) {
+	mc.mc_fpu_flags = 0 | rp->p_misc_flags & MF_FPU_INITIALIZED;
+	memcpy(&(mc.mc_fpu_state), rp->p_fpu_state.fpu_save_area_p,
+							FPU_XFP_SIZE);
+  } 
+#endif
+
+
+  /* Copy the mcontext structure to the user's address space. */
+  if ((r = data_copy(KERNEL, (vir_bytes) &mc, m_ptr->PR_ENDPT, 
+	(vir_bytes) m_ptr->PR_CTX_PTR,
+	(phys_bytes) sizeof(struct __mcontext))) != OK)
+	return(r);
+
+  return(OK);
+}
+
+
+/*===========================================================================*
+ *			      do_setmcontext				     *
+ *===========================================================================*/
+PUBLIC int do_setmcontext(struct proc * caller, message * m_ptr)
+{
+/* Set machine context of a process */
+
+  register struct proc *rp;
+  int proc_nr, r;
+  mcontext_t mc;
+
+  if (!isokendpt(m_ptr->PR_ENDPT, &proc_nr)) return(EINVAL);
+  rp = proc_addr(proc_nr);
+
+  /* Get the mcontext structure into our address space.  */
+  if ((r = data_copy(m_ptr->PR_ENDPT, (vir_bytes) m_ptr->PR_CTX_PTR, KERNEL,
+		(vir_bytes) &mc, (phys_bytes) sizeof(struct __mcontext))) != OK)
+	return(r);
+
+#if (_MINIX_CHIP == _CHIP_INTEL)
+  /* Copy FPU state */
+  if (mc.mc_fpu_flags & MF_FPU_INITIALIZED) {
+	rp->p_misc_flags |= MF_FPU_INITIALIZED;
+	memcpy(rp->p_fpu_state.fpu_save_area_p, &(mc.mc_fpu_state),
+								FPU_XFP_SIZE);
+  } else
+	rp->p_misc_flags &= ~MF_FPU_INITIALIZED;
+#endif
+
+  return(OK);
+}
+
+#endif