xref: /freebsd/sys/x86/include/psl.h (revision 29363fb446372cb3f10bc98664e9767c53fbb457)

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * William Jolitz.
 *
 * 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 REGENTS 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 REGENTS 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 _MACHINE_PSL_H_
#define	_MACHINE_PSL_H_

/*
 * 386 processor status longword.
 */
#define	PSL_C		0x00000001	/* carry bit */
#define	PSL_PF		0x00000004	/* parity bit */
#define	PSL_AF		0x00000010	/* bcd carry bit */
#define	PSL_Z		0x00000040	/* zero bit */
#define	PSL_N		0x00000080	/* negative bit */
#define	PSL_T		0x00000100	/* trace enable bit */
#define	PSL_I		0x00000200	/* interrupt enable bit */
#define	PSL_D		0x00000400	/* string instruction direction bit */
#define	PSL_V		0x00000800	/* overflow bit */
#define	PSL_IOPL	0x00003000	/* i/o privilege level */
#define	PSL_NT		0x00004000	/* nested task bit */
#define	PSL_RF		0x00010000	/* resume flag bit */
#define	PSL_VM		0x00020000	/* virtual 8086 mode bit */
#define	PSL_AC		0x00040000	/* alignment checking */
#define	PSL_VIF		0x00080000	/* virtual interrupt enable */
#define	PSL_VIP		0x00100000	/* virtual interrupt pending */
#define	PSL_ID		0x00200000	/* identification bit */

/*
 * The i486 manual says that we are not supposed to change reserved flags,
 * but this is too much trouble since the reserved flags depend on the cpu
 * and setting them to their historical values works in practice.
 */
#define	PSL_RESERVED_DEFAULT	0x00000002

/*
 * Initial flags for kernel and user mode.  The kernel later inherits
 * PSL_I and some other flags from user mode.
 */
#define	PSL_KERNEL	PSL_RESERVED_DEFAULT
#define	PSL_USER	(PSL_RESERVED_DEFAULT | PSL_I)

/*
 * Bits that can be changed in user mode on 486's.  We allow these bits
 * to be changed using ptrace(), sigreturn() and procfs.  Setting PS_NT
 * is undesirable but it may as well be allowed since users can inflict
 * it on the kernel directly.  Changes to PSL_AC are silently ignored on
 * 386's.
 *
 * Users are allowed to change the privileged flag PSL_RF.  The cpu sets PSL_RF
 * in tf_eflags for faults.  Debuggers should sometimes set it there too.
 * tf_eflags is kept in the signal context during signal handling and there is
 * no other place to remember it, so the PSL_RF bit may be corrupted by the
 * signal handler without us knowing.  Corruption of the PSL_RF bit at worst
 * causes one more or one less debugger trap, so allowing it is fairly
 * harmless.
 */
#define	PSL_USERCHANGE (PSL_C | PSL_PF | PSL_AF | PSL_Z | PSL_N | PSL_T \
			| PSL_D | PSL_V | PSL_NT | PSL_RF | PSL_AC | PSL_ID)

#endif /* !_MACHINE_PSL_H_ */