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/*
* Mach Operating System
* Copyright (c) 1991,1990 Carnegie Mellon University
* Copyright (c) 1991 IBM Corporation
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation,
* and that the name IBM not be used in advertising or publicity
* pertaining to distribution of the software without specific, written
* prior permission.
*
* CARNEGIE MELLON AND IBM ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON AND IBM DISCLAIM ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
/*
* Global descriptor table.
*/
#include <mach/machine/vm_types.h>
#include "vm_param.h"
#include "gdt.h"
#include "cpu_number.h"
extern void etext();
void
gdt_init()
{
/* Initialize kernel code segment descriptor, allowing
only kernel text to be executed in kernel mode.
This will have to change to allow loaded modules and such.
A limit of (LINEAR_MAX_KERNEL_ADDRESS - LINEAR_MIN_KERNEL_ADDRESS)
allows any kernel virtual address to be executed, but not user-mode
addresses accessible from kernel mode. */
fill_gdt_descriptor(KERNEL_CS,
LINEAR_MIN_KERNEL_ADDRESS,
(oskit_addr_t)etext - 1,
ACC_PL_K|ACC_CODE_R, SZ_32);
/* Initialize kernel data segment descriptor to allow any offset
so that any linear address is accessible, including wrapping
around to zero and covering the user-mode range. */
fill_gdt_descriptor(KERNEL_DS,
LINEAR_MIN_KERNEL_ADDRESS, 0xffffffff,
ACC_PL_K|ACC_DATA_W, SZ_32);
#if MULTIPROCESSOR
/*
* Set the %gs segment register to point at
* a word containing the cpu number.
*/
fill_gdt_descriptor(KERNEL_GS,
kvtolin((oskit_addr_t)&master_cpu),
sizeof(int) - 1,
ACC_PL_K|ACC_DATA, SZ_32);
#endif
}
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