xnu-792.13.8.tar.gz

[apple/xnu.git] / osfmk / i386 / mp_desc.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_OSREFERENCE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code 
 * as defined in and that are subject to the Apple Public Source License 
 * Version 2.0 (the 'License'). You may not use this file except in 
 * compliance with the License.  The rights granted to you under the 
 * License may not be used to create, or enable the creation or 
 * redistribution of, unlawful or unlicensed copies of an Apple operating 
 * system, or to circumvent, violate, or enable the circumvention or 
 * violation of, any terms of an Apple operating system software license 
 * agreement.
 *
 * Please obtain a copy of the License at 
 * http://www.opensource.apple.com/apsl/ and read it before using this 
 * file.
 *
 * The Original Code and all software distributed under the License are 
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 
 * Please see the License for the specific language governing rights and 
 * limitations under the License.
 *
 * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990 Carnegie Mellon University
 * 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.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS 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.
 */

/*
 */


#include <kern/cpu_number.h>
#include <kern/kalloc.h>
#include <kern/cpu_data.h>
#include <mach/mach_types.h>
#include <mach/machine.h>
#include <mach/vm_map.h>
#include <vm/vm_kern.h>
#include <vm/vm_map.h>

#include <i386/mp_desc.h>
#include <i386/lock.h>
#include <i386/misc_protos.h>
#include <i386/mp.h>
#include <i386/pmap.h>
#include <i386/cpu_threads.h>

#include <kern/misc_protos.h>

#include <mach_kdb.h>

/*
 * The i386 needs an interrupt stack to keep the PCB stack from being
 * overrun by interrupts.  All interrupt stacks MUST lie at lower addresses
 * than any thread`s kernel stack.
 */

/*
 * First cpu`s interrupt stack.
 */
extern uint32_t         low_intstack[]; /* bottom */
extern uint32_t         low_eintstack[];        /* top */

/*
 * Per-cpu data area pointers.
 * The master cpu (cpu 0) has its data area statically allocated;
 * others are allocated dynamically and this array is updated at runtime.
 */
cpu_data_t      cpu_data_master;
cpu_data_t      *cpu_data_ptr[MAX_CPUS] = { [0] &cpu_data_master };

decl_simple_lock_data(,cpu_lock);       /* protects real_ncpus */
unsigned int    real_ncpus = 1;
unsigned int    max_ncpus = MAX_CPUS;

extern void *hi_remap_text;
#define HI_TEXT(lo_text)        \
        (((uint32_t)&lo_text - (uint32_t)&hi_remap_text) + HIGH_MEM_BASE)

extern void     hi_sysenter(void);
extern void     hi64_sysenter(void);
extern void     hi64_syscall(void);


/*
 * Multiprocessor i386/i486 systems use a separate copy of the
 * GDT, IDT, LDT, and kernel TSS per processor.  The first three
 * are separate to avoid lock contention: the i386 uses locked
 * memory cycles to access the descriptor tables.  The TSS is
 * separate since each processor needs its own kernel stack,
 * and since using a TSS marks it busy.
 */

/*
 * Allocate and initialize the per-processor descriptor tables.
 */

struct fake_descriptor ldt_desc_pattern = {
        (unsigned int) 0,
        LDTSZ_MIN * sizeof(struct fake_descriptor) - 1,
        0,
        ACC_P|ACC_PL_K|ACC_LDT
};

struct fake_descriptor tss_desc_pattern = {
        (unsigned int) 0,
        sizeof(struct i386_tss) - 1,
        0,
        ACC_P|ACC_PL_K|ACC_TSS
};

struct fake_descriptor cpudata_desc_pattern = {
        (unsigned int) 0,
        sizeof(cpu_data_t)-1,
        SZ_32,
        ACC_P|ACC_PL_K|ACC_DATA_W
};

struct fake_descriptor userwindow_desc_pattern = {
        (unsigned int) 0,
        ((NBPDE * NCOPY_WINDOWS) / PAGE_SIZE) - 1,
        SZ_32 | SZ_G,
        ACC_P|ACC_PL_U|ACC_DATA_W
};

struct fake_descriptor physwindow_desc_pattern = {
        (unsigned int) 0,
        PAGE_SIZE - 1,
        SZ_32,
        ACC_P|ACC_PL_K|ACC_DATA_W
};

/*
 * This is the expanded, 64-bit variant of the kernel LDT descriptor.
 * When switching to 64-bit mode this replaces KERNEL_LDT entry
 * and the following empty slot. This enables the LDT to be referenced
 * in the uber-space remapping window on the kernel.
 */
struct fake_descriptor64 kernel_ldt_desc64 = {
        FAKE_UBER64(&master_ldt),
        LDTSZ_MIN*sizeof(struct fake_descriptor)-1,
        0,
        ACC_P|ACC_PL_K|ACC_LDT,
        0
};

/*
 * This is the expanded, 64-bit variant of the kernel TSS descriptor.
 * It is follows pattern of the KERNEL_LDT.
 */
struct fake_descriptor64 kernel_tss_desc64 = {
        FAKE_UBER64(&master_ktss64),
        sizeof(struct x86_64_tss)-1,
        0,
        ACC_P|ACC_PL_K|ACC_TSS,
        0
};

void
cpu_desc_init(
        cpu_data_t      *cdp,
        boolean_t       is_boot_cpu)
{
        cpu_desc_table_t        *cdt = cdp->cpu_desc_tablep;
        cpu_desc_index_t        *cdi = &cdp->cpu_desc_index;

        if (is_boot_cpu) {
            /*
             * Master CPU uses the tables built at boot time.
             * Just set the index pointers to the high shared-mapping space.
             * Note that the sysenter stack uses empty space above the ktss
             * in the HIGH_FIXED_KTSS page. In this case we don't map the
             * the real master_sstk in low memory.
             */
            cdi->cdi_ktss = (struct i386_tss *)
                                pmap_index_to_virt(HIGH_FIXED_KTSS) ;
            cdi->cdi_sstk  = (vm_offset_t) (cdi->cdi_ktss + 1) +
                                (vm_offset_t) &master_sstk.top -
                                (vm_offset_t) &master_sstk;
#if     MACH_KDB
            cdi->cdi_dbtss = (struct i386_tss *)
                                pmap_index_to_virt(HIGH_FIXED_DBTSS);
#endif  /* MACH_KDB */
            cdi->cdi_gdt = (struct fake_descriptor *)
                                pmap_index_to_virt(HIGH_FIXED_GDT);
            cdi->cdi_idt = (struct fake_descriptor *)
                                pmap_index_to_virt(HIGH_FIXED_IDT);
            cdi->cdi_ldt = (struct fake_descriptor *)
                                pmap_index_to_virt(HIGH_FIXED_LDT_BEGIN);

        } else {

            vm_offset_t cpu_hi_desc;

            cpu_hi_desc = pmap_cpu_high_shared_remap(cdp->cpu_number,
                                                     HIGH_CPU_DESC,
                                                     (vm_offset_t) cdt, 1);

            /*
             * Per-cpu GDT, IDT, LDT, KTSS descriptors are allocated in one
             * block (cpu_desc_table) and double-mapped into high shared space
             * in one page window.
             * Also, a transient stack for the fast sysenter path. The top of
             * which is set at context switch time to point to the PCB using
             * the high address.
             */
            cdi->cdi_gdt  = (struct fake_descriptor *) (cpu_hi_desc +
                                offsetof(cpu_desc_table_t, gdt[0]));
            cdi->cdi_idt  = (struct fake_descriptor *) (cpu_hi_desc +
                                offsetof(cpu_desc_table_t, idt[0]));
            cdi->cdi_ktss = (struct i386_tss *) (cpu_hi_desc +
                                offsetof(cpu_desc_table_t, ktss));
            cdi->cdi_sstk = cpu_hi_desc +
                                offsetof(cpu_desc_table_t, sstk.top);
                                
            /*
             * LDT descriptors are mapped into a seperate area.
             */
            cdi->cdi_ldt  = (struct fake_descriptor *)
                                pmap_cpu_high_shared_remap(
                                    cdp->cpu_number,
                                    HIGH_CPU_LDT_BEGIN,
                                    (vm_offset_t) cdp->cpu_ldtp,
                                    HIGH_CPU_LDT_END - HIGH_CPU_LDT_BEGIN + 1);

            /*
             * Copy the tables
             */
            bcopy((char *)master_idt,
                  (char *)cdt->idt,
                  sizeof(master_idt));
            bcopy((char *)master_gdt,
                  (char *)cdt->gdt,
                  sizeof(master_gdt));
            bcopy((char *)master_ldt,
                  (char *)cdp->cpu_ldtp,
                  sizeof(master_ldt));
            bzero((char *)&cdt->ktss,
                  sizeof(struct i386_tss));

#if     MACH_KDB
            cdi->cdi_dbtss = (struct i386_tss *) (cpu_hi_desc +
                                offsetof(cpu_desc_table_t, dbtss));
            bcopy((char *)&master_dbtss,
                  (char *)&cdt->dbtss,
                  sizeof(struct i386_tss));
#endif  /* MACH_KDB */

            /*
             * Fix up the entries in the GDT to point to
             * this LDT and this TSS.
             */
            cdt->gdt[sel_idx(KERNEL_LDT)] = ldt_desc_pattern;
            cdt->gdt[sel_idx(KERNEL_LDT)].offset = (vm_offset_t) cdi->cdi_ldt;
            fix_desc(&cdt->gdt[sel_idx(KERNEL_LDT)], 1);

            cdt->gdt[sel_idx(USER_LDT)] = ldt_desc_pattern;
            cdt->gdt[sel_idx(USER_LDT)].offset = (vm_offset_t) cdi->cdi_ldt;
            fix_desc(&cdt->gdt[sel_idx(USER_LDT)], 1);

            cdt->gdt[sel_idx(KERNEL_TSS)] = tss_desc_pattern;
            cdt->gdt[sel_idx(KERNEL_TSS)].offset = (vm_offset_t) cdi->cdi_ktss;
            fix_desc(&cdt->gdt[sel_idx(KERNEL_TSS)], 1);

            cdt->gdt[sel_idx(CPU_DATA_GS)] = cpudata_desc_pattern;
            cdt->gdt[sel_idx(CPU_DATA_GS)].offset = (vm_offset_t) cdp;
            fix_desc(&cdt->gdt[sel_idx(CPU_DATA_GS)], 1);

#if     MACH_KDB
            cdt->gdt[sel_idx(DEBUG_TSS)] = tss_desc_pattern;
            cdt->gdt[sel_idx(DEBUG_TSS)].offset = (vm_offset_t) cdi->cdi_dbtss;
            fix_desc(&cdt->gdt[sel_idx(DEBUG_TSS)], 1);

            cdt->dbtss.esp0 = (int)(db_task_stack_store +
                    (INTSTACK_SIZE * (cdp->cpu_number)) - sizeof (natural_t));
            cdt->dbtss.esp = cdt->dbtss.esp0;
            cdt->dbtss.eip = (int)&db_task_start;
#endif  /* MACH_KDB */

            cdt->ktss.ss0 = KERNEL_DS;
            cdt->ktss.io_bit_map_offset = 0x0FFF;       /* no IO bitmap */

            cpu_window_init(cdp->cpu_number);

        }

}

void
cpu_desc_init64(
        cpu_data_t      *cdp,
        boolean_t       is_boot_cpu)
{
        cpu_desc_table64_t      *cdt = (cpu_desc_table64_t *)
                                        cdp->cpu_desc_tablep;
        cpu_desc_index_t        *cdi = &cdp->cpu_desc_index;

        if (is_boot_cpu) {
            /*
             * Master CPU uses the tables built at boot time.
             * Just set the index pointers to the low memory space.
             * Note that in 64-bit mode these are addressed in the
             * double-mapped window (uber-space).
             */
            cdi->cdi_ktss = (struct i386_tss *) &master_ktss64;
            cdi->cdi_sstk = (vm_offset_t) &master_sstk.top;
            cdi->cdi_gdt  = master_gdt;
            cdi->cdi_idt  = (struct fake_descriptor *) &master_idt64;
            cdi->cdi_ldt  = (struct fake_descriptor *) &master_ldt;

            /* Replace the expanded LDT and TSS slots in the GDT: */
            *(struct fake_descriptor64 *) &master_gdt[sel_idx(KERNEL_LDT)] =
                kernel_ldt_desc64;
            *(struct fake_descriptor64 *) &master_gdt[sel_idx(KERNEL_TSS)] =
                kernel_tss_desc64;

            /*
             * Fix up the expanded descriptors for 64-bit.
             */
            fix_desc64((void *) &master_idt64, IDTSZ);
            fix_desc64((void *) &master_gdt[sel_idx(KERNEL_LDT)], 1);
            fix_desc64((void *) &master_gdt[sel_idx(KERNEL_TSS)], 1);

            /*
             * Set the double-fault stack as IST1 in the 64-bit TSS 
             */
            master_ktss64.ist1 = UBER64(df_task_stack_end);

        } else {
            /*
             * Per-cpu GDT, IDT, KTSS descriptors are allocated in kernel 
             * heap (cpu_desc_table) and double-mapped in uber-space (over 4GB).
             * LDT descriptors are mapped into a separate area.
             */
            cdi->cdi_gdt  = cdt->gdt;
            cdi->cdi_idt  = (struct fake_descriptor *) cdt->idt;
            cdi->cdi_ktss = (struct i386_tss *) &cdt->ktss;
            cdi->cdi_sstk = (vm_offset_t) &cdt->sstk.top;
            cdi->cdi_ldt  = cdp->cpu_ldtp;

            /*
             * Copy the tables
             */
            bcopy((char *)master_idt64,
                  (char *)cdt->idt,
                  sizeof(master_idt64));
            bcopy((char *)master_gdt,
                  (char *)cdt->gdt,
                  sizeof(master_gdt));
            bcopy((char *)master_ldt,
                  (char *)cdp->cpu_ldtp,
                  sizeof(master_ldt));
            bcopy((char *)&master_ktss64,
                  (char *)&cdt->ktss,
                  sizeof(struct x86_64_tss));

            /*
             * Fix up the entries in the GDT to point to
             * this LDT and this TSS.
             */
            kernel_ldt_desc64.offset[0] = (vm_offset_t) cdi->cdi_ldt;
            *(struct fake_descriptor64 *) &cdt->gdt[sel_idx(KERNEL_LDT)] =
                        kernel_ldt_desc64;
            fix_desc64(&cdt->gdt[sel_idx(KERNEL_LDT)], 1);

            kernel_ldt_desc64.offset[0] = (vm_offset_t) cdi->cdi_ldt;
            *(struct fake_descriptor64 *) &cdt->gdt[sel_idx(USER_LDT)] =
                        kernel_ldt_desc64;
            fix_desc64(&cdt->gdt[sel_idx(USER_LDT)], 1);

            kernel_tss_desc64.offset[0] = (vm_offset_t) cdi->cdi_ktss;
            *(struct fake_descriptor64 *) &cdt->gdt[sel_idx(KERNEL_TSS)] =
                        kernel_tss_desc64;
            fix_desc64(&cdt->gdt[sel_idx(KERNEL_TSS)], 1);

            cdt->gdt[sel_idx(CPU_DATA_GS)] = cpudata_desc_pattern;
            cdt->gdt[sel_idx(CPU_DATA_GS)].offset = (vm_offset_t) cdp;
            fix_desc(&cdt->gdt[sel_idx(CPU_DATA_GS)], 1);

            /* Set double-fault stack as IST1 */
            cdt->ktss.ist1 = UBER64(cdt->dfstk + sizeof(cdt->dfstk));

            /*
             * Allocate copyio windows.
             */
            cpu_window_init(cdp->cpu_number);

        }

        /* Require that the top of the sysenter stack is 16-byte aligned */
        if ((cdi->cdi_sstk % 16) != 0)
                panic("cpu_desc_init64() sysenter stack not 16-byte aligned");
}

/*
 * Set MSRs for sysenter/sysexit for 64-bit.
 */
void
fast_syscall_init64(void)
{
        wrmsr64(MSR_IA32_SYSENTER_CS, SYSENTER_CS); 
        wrmsr64(MSR_IA32_SYSENTER_EIP, UBER64(hi64_sysenter));
        wrmsr64(MSR_IA32_SYSENTER_ESP, UBER64(current_sstk()));

        /* Enable syscall/sysret */
        wrmsr64(MSR_IA32_EFER, rdmsr64(MSR_IA32_EFER) | MSR_IA32_EFER_SCE);

        /*
         * MSRs for 64-bit syscall/sysret
         * Note USER_CS because sysret uses this + 16 when returning to
         * 64-bit code.
         */
        wrmsr64(MSR_IA32_LSTAR, UBER64(hi64_syscall));
        wrmsr64(MSR_IA32_STAR, (((uint64_t)USER_CS)     << 48) |
                               (((uint64_t)KERNEL64_CS) << 32));
        /*
         * Emulate eflags cleared by sysenter but note that
         * we also clear the trace trap to avoid the complications
         * of single-stepping into a syscall. We also clear
         * the nested task bit to avoid a spurious "task switch"
         * on IRET.
         */
        wrmsr64(MSR_IA32_FMASK, EFL_DF|EFL_IF|EFL_TF|EFL_NT);

        /*
         * Set the Kermel GS base MSR to point to per-cpu data in uber-space.
         * The uber-space handler (hi64_syscall) uses the swapgs instruction.
         */
        wrmsr64(MSR_IA32_KERNEL_GS_BASE, UBER64(current_cpu_datap()));
        kprintf("fast_syscall_init64() KERNEL_GS_BASE=0x%016llx\n",
                rdmsr64(MSR_IA32_KERNEL_GS_BASE));
}

/*
 * Set MSRs for sysenter/sysexit
 */
void
fast_syscall_init(void)
{
        wrmsr(MSR_IA32_SYSENTER_CS, SYSENTER_CS, 0); 
        wrmsr(MSR_IA32_SYSENTER_EIP, HI_TEXT(hi_sysenter), 0);
        wrmsr(MSR_IA32_SYSENTER_ESP, current_sstk(), 0);
}

cpu_data_t *
cpu_data_alloc(boolean_t is_boot_cpu)
{
        int             ret;
        cpu_data_t      *cdp;

        if (is_boot_cpu) {
                assert(real_ncpus == 1);
                simple_lock_init(&cpu_lock, 0);
                cdp = &cpu_data_master;
                if (cdp->cpu_processor == NULL) {
                        cdp->cpu_processor = cpu_processor_alloc(TRUE);
                        cdp->cpu_pmap = pmap_cpu_alloc(TRUE);
                        cdp->cpu_this = cdp;
                        cdp->cpu_is64bit = FALSE;
                        cdp->cpu_int_stack_top = (vm_offset_t) low_eintstack;
                        cpu_desc_init(cdp, TRUE);
                        fast_syscall_init();
                }
                return cdp;
        }

        /* Check count before making allocations */
        if (real_ncpus >= max_ncpus)
                return NULL;

        /*
         * Allocate per-cpu data:
         */
        ret = kmem_alloc(kernel_map, 
                         (vm_offset_t *) &cdp, sizeof(cpu_data_t));
        if (ret != KERN_SUCCESS) {
                printf("cpu_data_alloc() failed, ret=%d\n", ret);
                goto abort;
        }
        bzero((void*) cdp, sizeof(cpu_data_t));
        cdp->cpu_this = cdp;

        /* Propagate mode */
        cdp->cpu_is64bit = cpu_mode_is64bit();

        /*
         * Allocate interrupt stack:
         */
        ret = kmem_alloc(kernel_map, 
                         (vm_offset_t *) &cdp->cpu_int_stack_top,
                         INTSTACK_SIZE);
        if (ret != KERN_SUCCESS) {
                printf("cpu_data_alloc() int stack failed, ret=%d\n", ret);
                goto abort;
        }
        bzero((void*) cdp->cpu_int_stack_top, INTSTACK_SIZE);
        cdp->cpu_int_stack_top += INTSTACK_SIZE;

        /*
         * Allocate descriptor table:
         * Size depends on cpu mode.
         */
        ret = kmem_alloc(kernel_map, 
                         (vm_offset_t *) &cdp->cpu_desc_tablep,
                         cdp->cpu_is64bit ? sizeof(cpu_desc_table64_t)
                                          : sizeof(cpu_desc_table_t));
        if (ret != KERN_SUCCESS) {
                printf("cpu_data_alloc() desc_table failed, ret=%d\n", ret);
                goto abort;
        }

        /*
         * Allocate LDT
         */
        ret = kmem_alloc(kernel_map, 
                         (vm_offset_t *) &cdp->cpu_ldtp,
                         sizeof(struct real_descriptor) * LDTSZ);
        if (ret != KERN_SUCCESS) {
                printf("cpu_data_alloc() ldt failed, ret=%d\n", ret);
                goto abort;
        }

        simple_lock(&cpu_lock);
        if (real_ncpus >= max_ncpus) {
                simple_unlock(&cpu_lock);
                goto abort;
        }
        cpu_data_ptr[real_ncpus] = cdp;
        cdp->cpu_number = real_ncpus;
        real_ncpus++;
        simple_unlock(&cpu_lock);

        kprintf("cpu_data_alloc(%d) 0x%x desc_table: 0x%x "
                "ldt: 0x%x "
                "int_stack: 0x%x-0x%x\n",
                cdp->cpu_number, cdp, cdp->cpu_desc_tablep, cdp->cpu_ldtp,
                cdp->cpu_int_stack_top - INTSTACK_SIZE, cdp->cpu_int_stack_top);

        return cdp;

abort:
        if (cdp) {
                if (cdp->cpu_desc_tablep)
                        kfree((void *) cdp->cpu_desc_tablep,
                                sizeof(*cdp->cpu_desc_tablep));
                if (cdp->cpu_int_stack_top)
                        kfree((void *) (cdp->cpu_int_stack_top - INTSTACK_SIZE),
                                INTSTACK_SIZE);
                kfree((void *) cdp, sizeof(*cdp));
        }
        return NULL;
}

boolean_t
valid_user_segment_selectors(uint16_t cs,
                             uint16_t ss,
                             uint16_t ds,
                             uint16_t es,
                             uint16_t fs,
                             uint16_t gs)
{       
        return valid_user_code_selector(cs)  &&
               valid_user_stack_selector(ss) &&
               valid_user_data_selector(ds)  &&
               valid_user_data_selector(es)  &&
               valid_user_data_selector(fs)  &&
               valid_user_data_selector(gs);
}


static vm_offset_t user_window_base = 0;
static vm_offset_t phys_window_base = 0;

void
cpu_window_init(int cpu)
{
        cpu_data_t              *cdp = cpu_data_ptr[cpu];
        cpu_desc_index_t        *cdi;
        vm_offset_t             user_window;
        vm_offset_t             phys_window;
        vm_offset_t             vaddr;
        int                     num_cpus;

        num_cpus = ml_get_max_cpus();

        if (cpu >= num_cpus)
                panic("copy_window_init: cpu > num_cpus");

        if (user_window_base == 0) {

                if (vm_allocate(kernel_map, &vaddr,
                                (NBPDE * NCOPY_WINDOWS * num_cpus) + NBPDE,
                                VM_FLAGS_ANYWHERE) != KERN_SUCCESS)
                        panic("copy_window_init: "
                                "couldn't allocate user map window");

                /*
                 * window must start on a page table boundary
                 * in the virtual address space
                 */
                user_window_base = (vaddr + (NBPDE - 1)) & ~(NBPDE - 1);

                /*
                 * get rid of any allocation leading up to our
                 * starting boundary
                 */
                vm_deallocate(kernel_map, vaddr, user_window_base - vaddr);

                /*
                 * get rid of tail that we don't need
                 */
                user_window = user_window_base +
                                        (NBPDE * NCOPY_WINDOWS * num_cpus);

                vm_deallocate(kernel_map, user_window,
                                (vaddr +
                                 ((NBPDE * NCOPY_WINDOWS * num_cpus) + NBPDE)) -
                                 user_window);

                if (vm_allocate(kernel_map, &phys_window_base,
                                PAGE_SIZE * num_cpus, VM_FLAGS_ANYWHERE)
                                        != KERN_SUCCESS)
                        panic("copy_window_init: "
                                "couldn't allocate phys map window");
        }

        user_window = user_window_base + (cpu * NCOPY_WINDOWS * NBPDE);
        phys_window = phys_window_base + (cpu * PAGE_SIZE);

        cdi = &cdp->cpu_desc_index;
          
        cdp->cpu_copywindow_base = user_window;
        cdp->cpu_copywindow_pdp  = pmap_pde(kernel_pmap, user_window);

        cdi->cdi_gdt[sel_idx(USER_WINDOW_SEL)] = userwindow_desc_pattern;
        cdi->cdi_gdt[sel_idx(USER_WINDOW_SEL)].offset = user_window;

        fix_desc(&cdi->cdi_gdt[sel_idx(USER_WINDOW_SEL)], 1);

        cdp->cpu_physwindow_base = phys_window;

        /*
         * make sure the page that encompasses the
         * pte pointer we're interested in actually
         * exists in the page table
         */
        pmap_expand(kernel_pmap, phys_window);

        cdp->cpu_physwindow_ptep = vtopte(phys_window);

        cdi->cdi_gdt[sel_idx(PHYS_WINDOW_SEL)] = physwindow_desc_pattern;
        cdi->cdi_gdt[sel_idx(PHYS_WINDOW_SEL)].offset = phys_window;

        fix_desc(&cdi->cdi_gdt[sel_idx(PHYS_WINDOW_SEL)], 1);
}


typedef struct {
        uint16_t        length;
        uint32_t        offset[2];
} __attribute__((__packed__)) table_descriptor64_t;

extern  table_descriptor64_t    gdtptr64;
extern  table_descriptor64_t    idtptr64;
/*
 * Load the segment descriptor tables for the current processor.
 */
void
cpu_desc_load64(cpu_data_t *cdp)
{
        cpu_desc_index_t        *cdi = &cdp->cpu_desc_index;

        /*
         * Load up the new descriptors etc
         * ml_load_desc64() expects these global pseudo-descriptors:
         *   gdtptr64 -> master_gdt
         *   idtptr64 -> master_idt64
         * These are 10-byte descriptors with 64-bit addresses into
         * uber-space.
         */
        gdtptr64.length = sizeof(master_gdt) - 1;
        gdtptr64.offset[0] = (uint32_t) cdi->cdi_gdt;
        gdtptr64.offset[1] = KERNEL_UBER_BASE_HI32;
        idtptr64.length = sizeof(master_idt64) - 1;
        idtptr64.offset[0] = (uint32_t) cdi->cdi_idt;
        idtptr64.offset[1] = KERNEL_UBER_BASE_HI32;

        /* Make sure busy bit is cleared in the TSS */
        gdt_desc_p(KERNEL_TSS)->access &= ~ACC_TSS_BUSY;
        
        ml_load_desc64();

        kprintf("64-bit descriptor tables loaded\n");
}