xnu-2782.1.97.tar.gz

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

/*
 * Copyright (c) 2003-2010 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_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_OSREFERENCE_LICENSE_HEADER_END@
 */

/*
 *      Here's what to do if you want to add a new routine to the comm page:
 *
 *              1. Add a definition for it's address in osfmk/i386/cpu_capabilities.h,
 *                 being careful to reserve room for future expansion.
 *
 *              2. Write one or more versions of the routine, each with it's own
 *                 commpage_descriptor.  The tricky part is getting the "special",
 *                 "musthave", and "canthave" fields right, so that exactly one
 *                 version of the routine is selected for every machine.
 *                 The source files should be in osfmk/i386/commpage/.
 *
 *              3. Add a ptr to your new commpage_descriptor(s) in the "routines"
 *                 array in osfmk/i386/commpage/commpage_asm.s.  There are two
 *                 arrays, one for the 32-bit and one for the 64-bit commpage.
 *
 *              4. Write the code in Libc to use the new routine.
 */

#include <mach/mach_types.h>
#include <mach/machine.h>
#include <mach/vm_map.h>
#include <mach/mach_vm.h>
#include <mach/machine.h>
#include <i386/cpuid.h>
#include <i386/tsc.h>
#include <i386/rtclock_protos.h>
#include <i386/cpu_data.h>
#include <i386/machine_routines.h>
#include <i386/misc_protos.h>
#include <i386/cpuid.h>
#include <machine/cpu_capabilities.h>
#include <machine/commpage.h>
#include <machine/pmap.h>
#include <vm/vm_kern.h>
#include <vm/vm_map.h>

#include <ipc/ipc_port.h>

#include <kern/page_decrypt.h>
#include <kern/processor.h>

/* the lists of commpage routines are in commpage_asm.s  */
extern  commpage_descriptor*    commpage_32_routines[];
extern  commpage_descriptor*    commpage_64_routines[];

extern vm_map_t commpage32_map; // the shared submap, set up in vm init
extern vm_map_t commpage64_map; // the shared submap, set up in vm init
extern vm_map_t commpage_text32_map;    // the shared submap, set up in vm init
extern vm_map_t commpage_text64_map;    // the shared submap, set up in vm init


char    *commPagePtr32 = NULL;          // virtual addr in kernel map of 32-bit commpage
char    *commPagePtr64 = NULL;          // ...and of 64-bit commpage
char    *commPageTextPtr32 = NULL;      // virtual addr in kernel map of 32-bit commpage
char    *commPageTextPtr64 = NULL;      // ...and of 64-bit commpage

uint64_t     _cpu_capabilities = 0;     // define the capability vector

typedef uint32_t commpage_address_t;

static commpage_address_t       next;   // next available address in comm page

static char    *commPagePtr;            // virtual addr in kernel map of commpage we are working on
static commpage_address_t       commPageBaseOffset; // subtract from 32-bit runtime address to get offset in virtual commpage in kernel map

static  commpage_time_data      *time_data32 = NULL;
static  commpage_time_data      *time_data64 = NULL;

decl_simple_lock_data(static,commpage_active_cpus_lock);

/* Allocate the commpage and add to the shared submap created by vm:
 *      1. allocate a page in the kernel map (RW)
 *      2. wire it down
 *      3. make a memory entry out of it
 *      4. map that entry into the shared comm region map (R-only)
 */

static  void*
commpage_allocate( 
        vm_map_t        submap,                 // commpage32_map or commpage_map64
        size_t          area_used,              // _COMM_PAGE32_AREA_USED or _COMM_PAGE64_AREA_USED
        vm_prot_t       uperm)
{
        vm_offset_t     kernel_addr = 0;        // address of commpage in kernel map
        vm_offset_t     zero = 0;
        vm_size_t       size = area_used;       // size actually populated
        vm_map_entry_t  entry;
        ipc_port_t      handle;
        kern_return_t   kr;

        if (submap == NULL)
                panic("commpage submap is null");

        if ((kr = vm_map(kernel_map,&kernel_addr,area_used,0,VM_FLAGS_ANYWHERE,NULL,0,FALSE,VM_PROT_ALL,VM_PROT_ALL,VM_INHERIT_NONE)))
                panic("cannot allocate commpage %d", kr);

        if ((kr = vm_map_wire(kernel_map,kernel_addr,kernel_addr+area_used,VM_PROT_DEFAULT,FALSE)))
                panic("cannot wire commpage: %d", kr);

        /* 
         * Now that the object is created and wired into the kernel map, mark it so that no delay
         * copy-on-write will ever be performed on it as a result of mapping it into user-space.
         * If such a delayed copy ever occurred, we could remove the kernel's wired mapping - and
         * that would be a real disaster.
         *
         * JMM - What we really need is a way to create it like this in the first place.
         */
        if (!(kr = vm_map_lookup_entry( kernel_map, vm_map_trunc_page(kernel_addr, VM_MAP_PAGE_MASK(kernel_map)), &entry) || entry->is_sub_map))
                panic("cannot find commpage entry %d", kr);
        entry->object.vm_object->copy_strategy = MEMORY_OBJECT_COPY_NONE;

        if ((kr = mach_make_memory_entry( kernel_map,           // target map
                                    &size,              // size 
                                    kernel_addr,        // offset (address in kernel map)
                                    uperm,      // protections as specified
                                    &handle,            // this is the object handle we get
                                    NULL )))            // parent_entry (what is this?)
                panic("cannot make entry for commpage %d", kr);

        if ((kr = vm_map_64(    submap,                         // target map (shared submap)
                        &zero,                          // address (map into 1st page in submap)
                        area_used,                      // size
                        0,                              // mask
                        VM_FLAGS_FIXED,                 // flags (it must be 1st page in submap)
                        handle,                         // port is the memory entry we just made
                        0,                              // offset (map 1st page in memory entry)
                        FALSE,                          // copy
                        uperm,   // cur_protection (R-only in user map)
                        uperm,   // max_protection
                        VM_INHERIT_SHARE )))             // inheritance
                panic("cannot map commpage %d", kr);

        ipc_port_release(handle);
        /* Make the kernel mapping non-executable. This cannot be done
         * at the time of map entry creation as mach_make_memory_entry
         * cannot handle disjoint permissions at this time.
         */
        kr = vm_protect(kernel_map, kernel_addr, area_used, FALSE, VM_PROT_READ | VM_PROT_WRITE);
        assert (kr == KERN_SUCCESS);

        return (void*)(intptr_t)kernel_addr;                     // return address in kernel map
}

/* Get address (in kernel map) of a commpage field. */

static void*
commpage_addr_of(
    commpage_address_t     addr_at_runtime )
{
        return  (void*) ((uintptr_t)commPagePtr + (addr_at_runtime - commPageBaseOffset));
}

/* Determine number of CPUs on this system.  We cannot rely on
 * machine_info.max_cpus this early in the boot.
 */
static int
commpage_cpus( void )
{
        int cpus;

        cpus = ml_get_max_cpus();                   // NB: this call can block

        if (cpus == 0)
                panic("commpage cpus==0");
        if (cpus > 0xFF)
                cpus = 0xFF;

        return cpus;
}

/* Initialize kernel version of _cpu_capabilities vector (used by KEXTs.) */

static void
commpage_init_cpu_capabilities( void )
{
        uint64_t bits;
        int cpus;
        ml_cpu_info_t cpu_info;

        bits = 0;
        ml_cpu_get_info(&cpu_info);
        
        switch (cpu_info.vector_unit) {
                case 9:
                        bits |= kHasAVX1_0;
                        /* fall thru */
                case 8:
                        bits |= kHasSSE4_2;
                        /* fall thru */
                case 7:
                        bits |= kHasSSE4_1;
                        /* fall thru */
                case 6:
                        bits |= kHasSupplementalSSE3;
                        /* fall thru */
                case 5:
                        bits |= kHasSSE3;
                        /* fall thru */
                case 4:
                        bits |= kHasSSE2;
                        /* fall thru */
                case 3:
                        bits |= kHasSSE;
                        /* fall thru */
                case 2:
                        bits |= kHasMMX;
                default:
                        break;
        }
        switch (cpu_info.cache_line_size) {
                case 128:
                        bits |= kCache128;
                        break;
                case 64:
                        bits |= kCache64;
                        break;
                case 32:
                        bits |= kCache32;
                        break;
                default:
                        break;
        }
        cpus = commpage_cpus();                 // how many CPUs do we have

        bits |= (cpus << kNumCPUsShift);

        bits |= kFastThreadLocalStorage;        // we use %gs for TLS

#define setif(_bits, _bit, _condition) \
        if (_condition) _bits |= _bit

        setif(bits, kUP,         cpus == 1);
        setif(bits, k64Bit,      cpu_mode_is64bit());
        setif(bits, kSlow,       tscFreq <= SLOW_TSC_THRESHOLD);

        setif(bits, kHasAES,     cpuid_features() &
                                        CPUID_FEATURE_AES);
        setif(bits, kHasF16C,    cpuid_features() &
                                        CPUID_FEATURE_F16C);
        setif(bits, kHasRDRAND,  cpuid_features() &
                                        CPUID_FEATURE_RDRAND);
        setif(bits, kHasFMA,     cpuid_features() &
                                        CPUID_FEATURE_FMA);

        setif(bits, kHasBMI1,    cpuid_leaf7_features() &
                                        CPUID_LEAF7_FEATURE_BMI1);
        setif(bits, kHasBMI2,    cpuid_leaf7_features() &
                                        CPUID_LEAF7_FEATURE_BMI2);
        setif(bits, kHasRTM,     cpuid_leaf7_features() &
                                        CPUID_LEAF7_FEATURE_RTM);
        setif(bits, kHasHLE,     cpuid_leaf7_features() &
                                        CPUID_LEAF7_FEATURE_HLE);
        setif(bits, kHasAVX2_0,  cpuid_leaf7_features() &
                                        CPUID_LEAF7_FEATURE_AVX2);
        
        uint64_t misc_enable = rdmsr64(MSR_IA32_MISC_ENABLE);
        setif(bits, kHasENFSTRG, (misc_enable & 1ULL) &&
                                 (cpuid_leaf7_features() &
                                        CPUID_LEAF7_FEATURE_ERMS));
        
        _cpu_capabilities = bits;               // set kernel version for use by drivers etc
}

/* initialize the approx_time_supported flag and set the approx time to 0.
 * Called during initial commpage population.
 */
static void
commpage_mach_approximate_time_init(void)
{
        char *cp = commPagePtr32;
        uint8_t supported;

#ifdef CONFIG_MACH_APPROXIMATE_TIME
        supported = 1;
#else
        supported = 0;
#endif
        if ( cp ) {
                cp += (_COMM_PAGE_APPROX_TIME_SUPPORTED - _COMM_PAGE32_BASE_ADDRESS);
                *(boolean_t *)cp = supported;
        }
        cp = commPagePtr64;
        if ( cp ) {
                cp += (_COMM_PAGE_APPROX_TIME_SUPPORTED - _COMM_PAGE32_START_ADDRESS);
                *(boolean_t *)cp = supported;
        }
        commpage_update_mach_approximate_time(0);
}


uint64_t
_get_cpu_capabilities(void)
{
        return _cpu_capabilities;
}

/* Copy data into commpage. */

static void
commpage_stuff(
    commpage_address_t  address,
    const void  *source,
    int         length  )
{    
    void        *dest = commpage_addr_of(address);
    
    if (address < next)
       panic("commpage overlap at address 0x%p, 0x%x < 0x%x", dest, address, next);
    
    bcopy(source,dest,length);
    
    next = address + length;
}

/* Copy a routine into comm page if it matches running machine.
 */
static void
commpage_stuff_routine(
    commpage_descriptor *rd     )
{
        commpage_stuff(rd->commpage_address,rd->code_address,rd->code_length);
}

/* Fill in the 32- or 64-bit commpage.  Called once for each.
 */

static void
commpage_populate_one( 
        vm_map_t        submap,         // commpage32_map or compage64_map
        char **         kernAddressPtr, // &commPagePtr32 or &commPagePtr64
        size_t          area_used,      // _COMM_PAGE32_AREA_USED or _COMM_PAGE64_AREA_USED
        commpage_address_t base_offset, // will become commPageBaseOffset
        commpage_time_data** time_data, // &time_data32 or &time_data64
        const char*     signature,      // "commpage 32-bit" or "commpage 64-bit"
        vm_prot_t       uperm)
{
        uint8_t         c1;
        uint16_t        c2;
        int             c4;
        uint64_t        c8;
        uint32_t        cfamily;
        short   version = _COMM_PAGE_THIS_VERSION;

        next = 0;
        commPagePtr = (char *)commpage_allocate( submap, (vm_size_t) area_used, uperm );
        *kernAddressPtr = commPagePtr;                          // save address either in commPagePtr32 or 64
        commPageBaseOffset = base_offset;

        *time_data = commpage_addr_of( _COMM_PAGE_TIME_DATA_START );

        /* Stuff in the constants.  We move things into the comm page in strictly
        * ascending order, so we can check for overlap and panic if so.
        * Note: the 32-bit cpu_capabilities vector is retained in addition to
        * the expanded 64-bit vector.
        */
        commpage_stuff(_COMM_PAGE_SIGNATURE,signature,(int)MIN(_COMM_PAGE_SIGNATURELEN, strlen(signature)));
        commpage_stuff(_COMM_PAGE_CPU_CAPABILITIES64,&_cpu_capabilities,sizeof(_cpu_capabilities));
        commpage_stuff(_COMM_PAGE_VERSION,&version,sizeof(short));
        commpage_stuff(_COMM_PAGE_CPU_CAPABILITIES,&_cpu_capabilities,sizeof(uint32_t));

        c2 = 32;  // default
        if (_cpu_capabilities & kCache64)
                c2 = 64;
        else if (_cpu_capabilities & kCache128)
                c2 = 128;
        commpage_stuff(_COMM_PAGE_CACHE_LINESIZE,&c2,2);

        c4 = MP_SPIN_TRIES;
        commpage_stuff(_COMM_PAGE_SPIN_COUNT,&c4,4);

        /* machine_info valid after ml_get_max_cpus() */
        c1 = machine_info.physical_cpu_max;
        commpage_stuff(_COMM_PAGE_PHYSICAL_CPUS,&c1,1);
        c1 = machine_info.logical_cpu_max;
        commpage_stuff(_COMM_PAGE_LOGICAL_CPUS,&c1,1);

        c8 = ml_cpu_cache_size(0);
        commpage_stuff(_COMM_PAGE_MEMORY_SIZE, &c8, 8);

        cfamily = cpuid_info()->cpuid_cpufamily;
        commpage_stuff(_COMM_PAGE_CPUFAMILY, &cfamily, 4);

        if (next > _COMM_PAGE_END)
                panic("commpage overflow: next = 0x%08x, commPagePtr = 0x%p", next, commPagePtr);

}


/* Fill in commpages: called once, during kernel initialization, from the
 * startup thread before user-mode code is running.
 *
 * See the top of this file for a list of what you have to do to add
 * a new routine to the commpage.
 */  

void
commpage_populate( void )
{
        commpage_init_cpu_capabilities();
        
        commpage_populate_one(  commpage32_map, 
                                &commPagePtr32,
                                _COMM_PAGE32_AREA_USED,
                                _COMM_PAGE32_BASE_ADDRESS,
                                &time_data32,
                                "commpage 32-bit",
                                VM_PROT_READ);
#ifndef __LP64__
        pmap_commpage32_init((vm_offset_t) commPagePtr32, _COMM_PAGE32_BASE_ADDRESS, 
                           _COMM_PAGE32_AREA_USED/INTEL_PGBYTES);
#endif                     
        time_data64 = time_data32;                      /* if no 64-bit commpage, point to 32-bit */

        if (_cpu_capabilities & k64Bit) {
                commpage_populate_one(  commpage64_map, 
                                        &commPagePtr64,
                                        _COMM_PAGE64_AREA_USED,
                                        _COMM_PAGE32_START_ADDRESS, /* commpage address are relative to 32-bit commpage placement */
                                        &time_data64,
                                        "commpage 64-bit",
                                        VM_PROT_READ);
#ifndef __LP64__
                pmap_commpage64_init((vm_offset_t) commPagePtr64, _COMM_PAGE64_BASE_ADDRESS, 
                                   _COMM_PAGE64_AREA_USED/INTEL_PGBYTES);
#endif
        }

        simple_lock_init(&commpage_active_cpus_lock, 0);

        commpage_update_active_cpus();
        commpage_mach_approximate_time_init();
        rtc_nanotime_init_commpage();
}

/* Fill in the common routines during kernel initialization. 
 * This is called before user-mode code is running.
 */
void commpage_text_populate( void ){
        commpage_descriptor **rd;
        
        next = 0;
        commPagePtr = (char *) commpage_allocate(commpage_text32_map, (vm_size_t) _COMM_PAGE_TEXT_AREA_USED, VM_PROT_READ | VM_PROT_EXECUTE);
        commPageTextPtr32 = commPagePtr;
        
        char *cptr = commPagePtr;
        int i=0;
        for(; i< _COMM_PAGE_TEXT_AREA_USED; i++){
                cptr[i]=0xCC;
        }
        
        commPageBaseOffset = _COMM_PAGE_TEXT_START;
        for (rd = commpage_32_routines; *rd != NULL; rd++) {
                commpage_stuff_routine(*rd);
        }

#ifndef __LP64__
        pmap_commpage32_init((vm_offset_t) commPageTextPtr32, _COMM_PAGE_TEXT_START, 
                           _COMM_PAGE_TEXT_AREA_USED/INTEL_PGBYTES);
#endif  

        if (_cpu_capabilities & k64Bit) {
                next = 0;
                commPagePtr = (char *) commpage_allocate(commpage_text64_map, (vm_size_t) _COMM_PAGE_TEXT_AREA_USED, VM_PROT_READ | VM_PROT_EXECUTE);
                commPageTextPtr64 = commPagePtr;

                cptr=commPagePtr;
                for(i=0; i<_COMM_PAGE_TEXT_AREA_USED; i++){
                        cptr[i]=0xCC;
                }

                for (rd = commpage_64_routines; *rd !=NULL; rd++) {
                        commpage_stuff_routine(*rd);
                }

#ifndef __LP64__
        pmap_commpage64_init((vm_offset_t) commPageTextPtr64, _COMM_PAGE_TEXT_START, 
                           _COMM_PAGE_TEXT_AREA_USED/INTEL_PGBYTES);
#endif  
        }

        if (next > _COMM_PAGE_TEXT_END) 
                panic("commpage text overflow: next=0x%08x, commPagePtr=%p", next, commPagePtr); 

}

/* Update commpage nanotime information.
 *
 * This routine must be serialized by some external means, ie a lock.
 */

void
commpage_set_nanotime(
        uint64_t        tsc_base,
        uint64_t        ns_base,
        uint32_t        scale,
        uint32_t        shift )
{
        commpage_time_data      *p32 = time_data32;
        commpage_time_data      *p64 = time_data64;
        static uint32_t generation = 0;
        uint32_t        next_gen;
        
        if (p32 == NULL)                /* have commpages been allocated yet? */
                return;
                
        if ( generation != p32->nt_generation )
                panic("nanotime trouble 1");    /* possibly not serialized */
        if ( ns_base < p32->nt_ns_base )
                panic("nanotime trouble 2");
        if ((shift != 0) && ((_cpu_capabilities & kSlow)==0) )
                panic("nanotime trouble 3");
                
        next_gen = ++generation;
        if (next_gen == 0)
                next_gen = ++generation;
        
        p32->nt_generation = 0;         /* mark invalid, so commpage won't try to use it */
        p64->nt_generation = 0;
        
        p32->nt_tsc_base = tsc_base;
        p64->nt_tsc_base = tsc_base;
        
        p32->nt_ns_base = ns_base;
        p64->nt_ns_base = ns_base;
        
        p32->nt_scale = scale;
        p64->nt_scale = scale;
        
        p32->nt_shift = shift;
        p64->nt_shift = shift;
        
        p32->nt_generation = next_gen;  /* mark data as valid */
        p64->nt_generation = next_gen;
}


/* Disable commpage gettimeofday(), forcing commpage to call through to the kernel.  */

void
commpage_disable_timestamp( void )
{
        time_data32->gtod_generation = 0;
        time_data64->gtod_generation = 0;
}


/* Update commpage gettimeofday() information.  As with nanotime(), we interleave
 * updates to the 32- and 64-bit commpage, in order to keep time more nearly in sync 
 * between the two environments.
 *
 * This routine must be serializeed by some external means, ie a lock.
 */
 
 void
 commpage_set_timestamp(
        uint64_t        abstime,
        uint64_t        secs )
{
        commpage_time_data      *p32 = time_data32;
        commpage_time_data      *p64 = time_data64;
        static uint32_t generation = 0;
        uint32_t        next_gen;
        
        next_gen = ++generation;
        if (next_gen == 0)
                next_gen = ++generation;
        
        p32->gtod_generation = 0;               /* mark invalid, so commpage won't try to use it */
        p64->gtod_generation = 0;
        
        p32->gtod_ns_base = abstime;
        p64->gtod_ns_base = abstime;
        
        p32->gtod_sec_base = secs;
        p64->gtod_sec_base = secs;
        
        p32->gtod_generation = next_gen;        /* mark data as valid */
        p64->gtod_generation = next_gen;
}


/* Update _COMM_PAGE_MEMORY_PRESSURE.  Called periodically from vm's compute_memory_pressure()  */

void
commpage_set_memory_pressure(
        unsigned int    pressure )
{
        char        *cp;
        uint32_t    *ip;
        
        cp = commPagePtr32;
        if ( cp ) {
                cp += (_COMM_PAGE_MEMORY_PRESSURE - _COMM_PAGE32_BASE_ADDRESS);
                ip = (uint32_t*) (void *) cp;
                *ip = (uint32_t) pressure;
        }
        
        cp = commPagePtr64;
        if ( cp ) {
                cp += (_COMM_PAGE_MEMORY_PRESSURE - _COMM_PAGE32_START_ADDRESS);
                ip = (uint32_t*) (void *) cp;
                *ip = (uint32_t) pressure;
        }

}


/* Update _COMM_PAGE_SPIN_COUNT.  We might want to reduce when running on a battery, etc. */

void
commpage_set_spin_count(
        unsigned int    count )
{
        char        *cp;
        uint32_t    *ip;
        
        if (count == 0)     /* we test for 0 after decrement, not before */
            count = 1;
            
        cp = commPagePtr32;
        if ( cp ) {
                cp += (_COMM_PAGE_SPIN_COUNT - _COMM_PAGE32_BASE_ADDRESS);
                ip = (uint32_t*) (void *) cp;
                *ip = (uint32_t) count;
        }
        
        cp = commPagePtr64;
        if ( cp ) {
                cp += (_COMM_PAGE_SPIN_COUNT - _COMM_PAGE32_START_ADDRESS);
                ip = (uint32_t*) (void *) cp;
                *ip = (uint32_t) count;
        }

}

/* Updated every time a logical CPU goes offline/online */
void
commpage_update_active_cpus(void)
{
        char        *cp;
        volatile uint8_t    *ip;
        
        /* At least 32-bit commpage must be initialized */
        if (!commPagePtr32)
                return;

        simple_lock(&commpage_active_cpus_lock);

        cp = commPagePtr32;
        cp += (_COMM_PAGE_ACTIVE_CPUS - _COMM_PAGE32_BASE_ADDRESS);
        ip = (volatile uint8_t*) cp;
        *ip = (uint8_t) processor_avail_count;
        
        cp = commPagePtr64;
        if ( cp ) {
                cp += (_COMM_PAGE_ACTIVE_CPUS - _COMM_PAGE32_START_ADDRESS);
                ip = (volatile uint8_t*) cp;
                *ip = (uint8_t) processor_avail_count;
        }

        simple_unlock(&commpage_active_cpus_lock);
}

/*
 * update the commpage data for last known value of mach_absolute_time()
 */

void
commpage_update_mach_approximate_time(uint64_t abstime)
{
#ifdef CONFIG_MACH_APPROXIMATE_TIME
        uint64_t saved_data;
        char *cp;

        cp = commPagePtr32;
        if ( cp ) {
                cp += (_COMM_PAGE_APPROX_TIME - _COMM_PAGE32_BASE_ADDRESS);
                saved_data = *(uint64_t *)cp;
                if (saved_data < abstime) {
                        /* ignoring the success/fail return value assuming that
                         * if the value has been updated since we last read it,
                         * "someone" has a newer timestamp than us and ours is
                         * now invalid. */
                        OSCompareAndSwap64(saved_data, abstime, (uint64_t *)cp);
                }
        }
        cp = commPagePtr64;
        if ( cp ) {
                cp += (_COMM_PAGE_APPROX_TIME - _COMM_PAGE32_START_ADDRESS);
                saved_data = *(uint64_t *)cp;
                if (saved_data < abstime) {
                        /* ignoring the success/fail return value assuming that
                         * if the value has been updated since we last read it,
                         * "someone" has a newer timestamp than us and ours is
                         * now invalid. */
                        OSCompareAndSwap64(saved_data, abstime, (uint64_t *)cp);
                }
        }
#else
#pragma unused (abstime)
#endif
}


extern user32_addr_t commpage_text32_location;
extern user64_addr_t commpage_text64_location;

/* Check to see if a given address is in the Preemption Free Zone (PFZ) */

uint32_t
commpage_is_in_pfz32(uint32_t addr32)
{
        if ( (addr32 >= (commpage_text32_location + _COMM_TEXT_PFZ_START_OFFSET)) 
                && (addr32 < (commpage_text32_location+_COMM_TEXT_PFZ_END_OFFSET))) {
                return 1;
        }
        else
                return 0;
}

uint32_t
commpage_is_in_pfz64(addr64_t addr64)
{
        if ( (addr64 >= (commpage_text64_location + _COMM_TEXT_PFZ_START_OFFSET))
             && (addr64 <  (commpage_text64_location + _COMM_TEXT_PFZ_END_OFFSET))) {
                return 1;
        }
        else
                return 0;
}