Initial Spring 2016 commit.

kern/include/current.h

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * 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.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY 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 UNIVERSITY 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.
+ */
+
+#ifndef _CURRENT_H_
+#define _CURRENT_H_
+
+/*
+ * Definition of curcpu and curthread.
+ *
+ * The machine-dependent header should define either curcpu or curthread
+ * as a macro (but not both); then we use one to get the other, and include
+ * the header file needed to make that reference. (These includes are why
+ * this file isn't rolled into either cpu.h or thread.h.)
+ *
+ * This material is machine-dependent because on some platforms it is
+ * better/easier to keep track of curcpu and make curthread be
+ * curcpu->c_curthread, and on others to keep track of curthread and
+ * make curcpu be curthread->t_cpu.
+ *
+ * Either way we don't want retrieving curthread or curcpu to be
+ * expensive; digging around in system board registers and whatnot is
+ * not a very good idea. So we want to keep either curthread or curcpu
+ * on-chip somewhere in some fashion.
+ *
+ * There are various possible approaches; for example, one might use
+ * the MMU on each CPU to map that CPU's cpu structure to a fixed
+ * virtual address that's the same on all CPUs. Then curcpu can be a
+ * constant. (But one has to remember to use curcpu->c_self as the
+ * canonical form of the pointer anywhere that's visible to other
+ * CPUs.) On some CPUs the CPU number or cpu structure base address
+ * can be stored in a supervisor-mode register, where it can be set up
+ * during boot and then left alone. An alternative approach is to
+ * reserve a register to hold curthread, and update it during context
+ * switch.
+ *
+ * See each platform's machine/current.h for a discussion of what it
+ * does and why.
+ */
+
+#include <machine/current.h>
+
+#if defined(__NEED_CURTHREAD)
+
+#include <cpu.h>
+#define curthread curcpu->c_curthread
+#define CURCPU_EXISTS() (curcpu != NULL)
+
+#endif
+
+#if defined(__NEED_CURCPU)
+
+#include <thread.h>
+#define curcpu curthread->t_cpu
+#define CURCPU_EXISTS() (curthread != NULL)
+
+#endif
+
+/*
+ * Definition of curproc.
+ *
+ * curproc is always the current thread's process.
+ */
+
+#define curproc (curthread->t_proc)
+
+
+#endif /* _CURRENT_H_ */