freebsd-dev/sys/i386/include/pcb.h

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/*-
* 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.
* 4. 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.
*
* from: @(#)pcb.h 5.10 (Berkeley) 5/12/91
1999-08-28 01:08:13 +00:00
* $FreeBSD$
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*/
#ifndef _I386_PCB_H_
#define _I386_PCB_H_
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/*
* Intel 386 process control block
*/
#ifndef _KERNEL
#include <machine/segments.h>
#endif
#include <machine/npx.h>
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struct pcb {
int pcb_cr3;
int pcb_edi;
int pcb_esi;
int pcb_ebp;
int pcb_esp;
int pcb_ebx;
int pcb_eip;
int pcb_dr0;
int pcb_dr1;
int pcb_dr2;
int pcb_dr3;
int pcb_dr6;
int pcb_dr7;
union savefpu pcb_save;
u_int pcb_flags;
#define FP_SOFTFP 0x01 /* process using software fltng pnt emulator */
#define PCB_DBREGS 0x02 /* process using debug registers */
#define PCB_NPXTRAP 0x04 /* npx trap pending */
#define PCB_NPXINITDONE 0x08 /* fpu state is initialized */
#define PCB_VM86CALL 0x10 /* in vm86 call */
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caddr_t pcb_onfault; /* copyin/out fault recovery */
int pcb_gs;
Change the segment limits to 4GB, we set the user accessible bit on all of the kernel address space already. Intel recommend this anyway, because using a non-4GB limit adds an additional clock cycle to address generation. We were able to install 4GB segments into the LDT, so any limits we imposed on %cs and %ds were academic anyway. More importantly, this allows us to make a page in the kernel readable to user applications, for holding things like the signal trampoline and other fun things. Move the user %cs/%ds segments from the LDT to the GDT. There was no good reason for them to be there anyway. The old LDT entries are still there but we can now relax the restriction that prevented users from emptying the default LDT entries. Putting user and kernel %cs and %ds together allows us to access the fast sysenter/sysexit/syscall/sysret instructions. syscall/sysret in particular require that the user/kernel segments be laid out this way. Reserve a slot specifically for NDIS while here. Create two user controllable slots in the GDT that are context switched with the (kernel) thread. This allows user applications to set two user privilige selectors to arbitary values. Create i386_set_fsbase(void *base) and friends. (get/set, fs/gs). For i386, %gs is used by tls and the thread libraries and this means that user processes no longer have to have the cost of having a custom LDT, and we will no longer to do a ldt switch when activating a kthread/ithread in the usual case any more. In other words, we can now set the base address for %fs and %gs to arbitary addresses without the pain of messing with ldt segments.
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struct segment_descriptor pcb_fsd;
struct segment_descriptor pcb_gsd;
struct pcb_ext *pcb_ext; /* optional pcb extension */
int pcb_psl; /* process status long */
u_long pcb_vm86[2]; /* vm86bios scratch space */
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};
#ifdef _KERNEL
struct trapframe;
void makectx(struct trapframe *, struct pcb *);
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void savectx(struct pcb *);
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#endif
#endif /* _I386_PCB_H_ */