[apple/xnu.git] / osfmk / arm64 / arm_vm_init.c

/*
 * Copyright (c) 2007-2011 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@
 */

#include <mach_debug.h>
#include <mach_kdp.h>
#include <debug.h>

#include <mach/vm_types.h>
#include <mach/vm_param.h>
#include <kern/misc_protos.h>
#include <kern/assert.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/pmap.h>

#include <arm64/proc_reg.h>
#include <arm64/lowglobals.h>
#include <arm/cpu_data_internal.h>
#include <arm/misc_protos.h>
#include <pexpert/arm64/boot.h>

#include <libkern/kernel_mach_header.h>
#include <libkern/section_keywords.h>

#if __ARM_KERNEL_PROTECT__
#include <arm/atomic.h>
#endif /* __ARM_KERNEL_PROTECT__ */

#if __ARM_KERNEL_PROTECT__
/*
 * If we want to support __ARM_KERNEL_PROTECT__, we need a sufficient amount of
 * mappable space preceeding the kernel (as we unmap the kernel by cutting the
 * range covered by TTBR1 in half).  This must also cover the exception vectors.
 */
static_assert(KERNEL_PMAP_HEAP_RANGE_START > ARM_KERNEL_PROTECT_EXCEPTION_START);

/* The exception vectors and the kernel cannot share root TTEs. */
static_assert((KERNEL_PMAP_HEAP_RANGE_START & ~ARM_TT_ROOT_OFFMASK) > ARM_KERNEL_PROTECT_EXCEPTION_START);

/*
 * We must have enough space in the TTBR1_EL1 range to create the EL0 mapping of
 * the exception vectors.
 */
static_assert((((~ARM_KERNEL_PROTECT_EXCEPTION_START) + 1) * 2ULL) <= (ARM_TT_ROOT_SIZE + ARM_TT_ROOT_INDEX_MASK));
#endif /* __ARM_KERNEL_PROTECT__ */

#if KASAN
extern vm_offset_t shadow_pbase;
extern vm_offset_t shadow_ptop;
extern vm_offset_t physmap_vbase;
extern vm_offset_t physmap_vtop;
#endif

/*
 * Denotes the end of xnu.
 */
extern void *last_kernel_symbol;

/*
 * KASLR parameters
 */
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kernel_base;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kernel_top;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kext_base;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kext_top;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kernel_stext;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kernel_etext;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kernel_slide;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kernel_slid_base;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_kernel_slid_top;

SECURITY_READ_ONLY_LATE(vm_offset_t) vm_prelink_stext;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_prelink_etext;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_prelink_sdata;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_prelink_edata;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_prelink_sinfo;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_prelink_einfo;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_slinkedit;
SECURITY_READ_ONLY_LATE(vm_offset_t) vm_elinkedit;

/* Used by <mach/arm/vm_param.h> */
SECURITY_READ_ONLY_LATE(unsigned long) gVirtBase;
SECURITY_READ_ONLY_LATE(unsigned long) gPhysBase;
SECURITY_READ_ONLY_LATE(unsigned long) gPhysSize;


/*
 * NOTE: mem_size is bogus on large memory machines. 
 *       We will pin it to 0x80000000 if there is more than 2 GB
 *       This is left only for compatibility and max_mem should be used.
 */
vm_offset_t mem_size;                             /* Size of actual physical memory present
                                                   * minus any performance buffer and possibly
                                                   * limited by mem_limit in bytes */
uint64_t    mem_actual;                           /* The "One True" physical memory size
                                                   * actually, it's the highest physical
                                                   * address + 1 */
uint64_t    max_mem;                              /* Size of physical memory (bytes), adjusted
                                                   * by maxmem */
uint64_t    sane_size;                            /* Memory size to use for defaults
                                                   * calculations */
/* This no longer appears to be used; kill it? */
addr64_t    vm_last_addr = VM_MAX_KERNEL_ADDRESS; /* Highest kernel
                                                   * virtual address known
                                                   * to the VM system */

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segTEXTB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizeTEXT;


SECURITY_READ_ONLY_LATE(static vm_offset_t)   segDATACONSTB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizeDATACONST;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segTEXTEXECB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizeTEXTEXEC;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segDATAB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizeDATA;


SECURITY_READ_ONLY_LATE(static vm_offset_t)   segLINKB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizeLINK;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segKLDB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizeKLD;
SECURITY_READ_ONLY_LATE(static vm_offset_t)   segLASTB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizeLAST;

SECURITY_READ_ONLY_LATE(vm_offset_t)          segPRELINKTEXTB;
SECURITY_READ_ONLY_LATE(unsigned long)        segSizePRELINKTEXT;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segPLKTEXTEXECB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizePLKTEXTEXEC;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segPLKDATACONSTB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizePLKDATACONST;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segPRELINKDATAB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizePRELINKDATA;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segPLKLLVMCOVB = 0;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizePLKLLVMCOV = 0;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segPLKLINKEDITB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizePLKLINKEDIT;

SECURITY_READ_ONLY_LATE(static vm_offset_t)   segPRELINKINFOB;
SECURITY_READ_ONLY_LATE(static unsigned long) segSizePRELINKINFO;

SECURITY_READ_ONLY_LATE(static boolean_t) use_contiguous_hint = TRUE;

SECURITY_READ_ONLY_LATE(unsigned) PAGE_SHIFT_CONST;

SECURITY_READ_ONLY_LATE(vm_offset_t) end_kern;
SECURITY_READ_ONLY_LATE(vm_offset_t) etext;
SECURITY_READ_ONLY_LATE(vm_offset_t) sdata;
SECURITY_READ_ONLY_LATE(vm_offset_t) edata;

vm_offset_t alloc_ptpage(boolean_t map_static);
SECURITY_READ_ONLY_LATE(vm_offset_t) ropage_next;

/*
 * Bootstrap the system enough to run with virtual memory.
 * Map the kernel's code and data, and allocate the system page table.
 * Page_size must already be set.
 *
 * Parameters:
 * first_avail: first available physical page -
 *              after kernel page tables
 * avail_start: PA of first physical page
 * avail_end:   PA of last physical page
 */
SECURITY_READ_ONLY_LATE(vm_offset_t)     first_avail;
SECURITY_READ_ONLY_LATE(vm_offset_t)     static_memory_end;
SECURITY_READ_ONLY_LATE(pmap_paddr_t)    avail_start;
SECURITY_READ_ONLY_LATE(pmap_paddr_t)    avail_end;

#if __ARM_KERNEL_PROTECT__
extern void ExceptionVectorsBase;
extern void ExceptionVectorsEnd;
#endif /* __ARM_KERNEL_PROTECT__ */

#define MEM_SIZE_MAX            0x100000000ULL

#if defined(KERNEL_INTEGRITY_KTRR)
#if __ARM64_TWO_LEVEL_PMAP__
/* We could support this configuration, but it adds memory overhead. */
#error This configuration is not supported
#endif
#endif

/*
 * This rounds the given address up to the nearest boundary for a PTE contiguous
 * hint.
 */
static vm_offset_t
round_up_pte_hint_address(vm_offset_t address)
{
        vm_offset_t hint_size = ARM_PTE_SIZE << ARM_PTE_HINT_ENTRIES_SHIFT;
        return ((address + (hint_size - 1)) & ~(hint_size - 1));
}

/* allocate a page for a page table: we support static and dynamic mappings.
 *
 * returns a virtual address for the allocated page
 *
 * for static mappings, we allocate from the region ropagetable_begin to ro_pagetable_end-1,
 * which is defined in the DATA_CONST segment and will be protected RNX when vm_prot_finalize runs.
 *
 * for dynamic mappings, we allocate from avail_start, which should remain RWNX.
 */

vm_offset_t alloc_ptpage(boolean_t map_static) {
        vm_offset_t vaddr;

#if !(defined(KERNEL_INTEGRITY_KTRR))
        map_static = FALSE;
#endif

        if (!ropage_next) {
                ropage_next = (vm_offset_t)&ropagetable_begin;
        }

        if (map_static) {
                assert(ropage_next < (vm_offset_t)&ropagetable_end);

                vaddr = ropage_next;
                ropage_next += ARM_PGBYTES;

                return vaddr;
        } else {
                vaddr = phystokv(avail_start);
                avail_start += ARM_PGBYTES;

                return vaddr;
        }
}

#if DEBUG

void dump_kva_l2(vm_offset_t tt_base, tt_entry_t *tt, int indent, uint64_t *rosz_out, uint64_t *rwsz_out);

void dump_kva_l2(vm_offset_t tt_base, tt_entry_t *tt, int indent, uint64_t *rosz_out, uint64_t *rwsz_out) {
        unsigned int i;
        boolean_t cur_ro, prev_ro = 0;
        int start_entry = -1;
        tt_entry_t cur, prev = 0;
        pmap_paddr_t robegin = kvtophys((vm_offset_t)&ropagetable_begin);
        pmap_paddr_t roend = kvtophys((vm_offset_t)&ropagetable_end);
        boolean_t tt_static = kvtophys((vm_offset_t)tt) >= robegin &&
                              kvtophys((vm_offset_t)tt) < roend;

        for(i=0; i<TTE_PGENTRIES; i++) {
                int tte_type = tt[i] & ARM_TTE_TYPE_MASK;
                cur = tt[i] & ARM_TTE_TABLE_MASK;

                if (tt_static) {
                        /* addresses mapped by this entry are static if it is a block mapping,
                         * or the table was allocated from the RO page table region */
                        cur_ro = (tte_type == ARM_TTE_TYPE_BLOCK) || (cur >= robegin && cur < roend);
                } else {
                        cur_ro = 0;
                }

                if ((cur == 0 && prev != 0) || (cur_ro != prev_ro && prev != 0)) { // falling edge
                        uintptr_t start,end,sz;

                        start = (uintptr_t)start_entry << ARM_TT_L2_SHIFT;
                        start += tt_base;
                        end = ((uintptr_t)i << ARM_TT_L2_SHIFT) - 1;
                        end += tt_base;

                        sz = end - start + 1;
                        printf("%*s0x%08x_%08x-0x%08x_%08x %s (%luMB)\n",
                               indent*4, "",
                                   (uint32_t)(start >> 32),(uint32_t)start,
                                   (uint32_t)(end >> 32),(uint32_t)end,
                                   prev_ro ? "Static " : "Dynamic",
                                   (sz >> 20));

                        if (prev_ro) {
                                *rosz_out += sz;
                        } else {
                                *rwsz_out += sz;
                        }
                }

                if ((prev == 0 && cur != 0) || cur_ro != prev_ro) { // rising edge: set start
                        start_entry = i;
                }

                prev = cur;
                prev_ro = cur_ro;
        }
}

void dump_kva_space() {
        uint64_t tot_rosz=0, tot_rwsz=0;
        int ro_ptpages, rw_ptpages;
        pmap_paddr_t robegin = kvtophys((vm_offset_t)&ropagetable_begin);
        pmap_paddr_t roend = kvtophys((vm_offset_t)&ropagetable_end);
        boolean_t root_static = kvtophys((vm_offset_t)cpu_tte) >= robegin &&
                                kvtophys((vm_offset_t)cpu_tte) < roend;
        uint64_t kva_base = ~((1ULL << (64 - T1SZ_BOOT)) - 1);

        printf("Root page table: %s\n", root_static ? "Static" : "Dynamic");

#if !__ARM64_TWO_LEVEL_PMAP__
        for(unsigned int i=0; i<TTE_PGENTRIES; i++) {
                pmap_paddr_t cur;
                boolean_t cur_ro;
                uintptr_t start,end;
                uint64_t rosz = 0, rwsz = 0;

                if ((cpu_tte[i] & ARM_TTE_VALID) == 0)
                        continue;

                cur = cpu_tte[i] & ARM_TTE_TABLE_MASK;
                start = (uint64_t)i << ARM_TT_L1_SHIFT;
                start = start + kva_base;
                end = start + (ARM_TT_L1_SIZE - 1);
                cur_ro = cur >= robegin && cur < roend;

                printf("0x%08x_%08x-0x%08x_%08x %s\n",
                       (uint32_t)(start >> 32),(uint32_t)start,
                           (uint32_t)(end >> 32),(uint32_t)end,
                           cur_ro ? "Static " : "Dynamic");

                dump_kva_l2(start, (tt_entry_t*)phystokv(cur), 1, &rosz, &rwsz);
                tot_rosz += rosz;
                tot_rwsz += rwsz;
        }
#else
        dump_kva_l2(kva_base, cpu_tte, 0, &tot_rosz, &tot_rwsz);
#endif /* !_ARM64_TWO_LEVEL_PMAP__ */

        printf("L2 Address space mapped: Static %lluMB Dynamic %lluMB Total %lluMB\n",
          tot_rosz >> 20,
          tot_rwsz >> 20,
          (tot_rosz >> 20) + (tot_rwsz >> 20));

        ro_ptpages = (int)((ropage_next - (vm_offset_t)&ropagetable_begin) >> ARM_PGSHIFT);
        rw_ptpages = (int)(lowGlo.lgStaticSize  >> ARM_PGSHIFT);
        printf("Pages used: static %d dynamic %d\n", ro_ptpages, rw_ptpages);
}

#endif /* DEBUG */

#if __ARM_KERNEL_PROTECT__
/*
 * arm_vm_map:
 *   root_ttp: The kernel virtual address for the root of the target page tables
 *   vaddr: The target virtual address
 *   pte: A page table entry value (may be ARM_PTE_EMPTY)
 *
 * This function installs pte at vaddr in root_ttp.  Any page table pages needed
 * to install pte will be allocated by this function.
 */
static void
arm_vm_map(tt_entry_t * root_ttp, vm_offset_t vaddr, pt_entry_t pte)
{
        vm_offset_t ptpage = 0;
        tt_entry_t * ttp = root_ttp;

#if !__ARM64_TWO_LEVEL_PMAP__
        tt_entry_t * l1_ttep = NULL;
        tt_entry_t l1_tte = 0;
#endif

        tt_entry_t * l2_ttep = NULL;
        tt_entry_t l2_tte = 0;
        pt_entry_t * ptep = NULL;
        pt_entry_t cpte = 0;

        /*
         * Walk the target page table to find the PTE for the given virtual
         * address.  Allocate any page table pages needed to do this.
         */
#if !__ARM64_TWO_LEVEL_PMAP__
        l1_ttep = ttp + ((vaddr & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT);
        l1_tte = *l1_ttep;

        if (l1_tte == ARM_TTE_EMPTY) {
                ptpage = alloc_ptpage(TRUE);
                bzero((void *)ptpage, ARM_PGBYTES);
                l1_tte = kvtophys(ptpage);
                l1_tte &= ARM_TTE_TABLE_MASK;
                l1_tte |= ARM_TTE_VALID | ARM_TTE_TYPE_TABLE;
                *l1_ttep = l1_tte;
                ptpage = 0;
        }

        ttp = (tt_entry_t *)phystokv(l1_tte & ARM_TTE_TABLE_MASK);
#endif

        l2_ttep = ttp + ((vaddr & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
        l2_tte = *l2_ttep;

        if (l2_tte == ARM_TTE_EMPTY) {
                ptpage = alloc_ptpage(TRUE);
                bzero((void *)ptpage, ARM_PGBYTES);
                l2_tte = kvtophys(ptpage);
                l2_tte &= ARM_TTE_TABLE_MASK;
                l2_tte |= ARM_TTE_VALID | ARM_TTE_TYPE_TABLE;
                *l2_ttep = l2_tte;
                ptpage = 0;
        }

        ttp = (tt_entry_t *)phystokv(l2_tte & ARM_TTE_TABLE_MASK);

        ptep = ttp + ((vaddr & ARM_TT_L3_INDEX_MASK) >> ARM_TT_L3_SHIFT);
        cpte = *ptep;

        /*
         * If the existing PTE is not empty, then we are replacing a valid
         * mapping.
         */
        if (cpte != ARM_PTE_EMPTY) {
                panic("%s: cpte=%#llx is not empty, "
                      "vaddr=%#lx, pte=%#llx",
                      __FUNCTION__, cpte,
                      vaddr, pte);
        }

        *ptep = pte;
}

/*
 * arm_vm_kernel_el0_map:
 *   vaddr: The target virtual address
 *   pte: A page table entry value (may be ARM_PTE_EMPTY)
 *
 * This function installs pte at vaddr for the EL0 kernel mappings.
 */
static void
arm_vm_kernel_el0_map(vm_offset_t vaddr, pt_entry_t pte)
{
        /* Calculate where vaddr will be in the EL1 kernel page tables. */
        vm_offset_t kernel_pmap_vaddr = vaddr - ((ARM_TT_ROOT_INDEX_MASK + ARM_TT_ROOT_SIZE) / 2ULL);
        arm_vm_map(cpu_tte, kernel_pmap_vaddr, pte);
}

/*
 * arm_vm_kernel_el1_map:
 *   vaddr: The target virtual address
 *   pte: A page table entry value (may be ARM_PTE_EMPTY)
 *
 * This function installs pte at vaddr for the EL1 kernel mappings.
 */
static void
arm_vm_kernel_el1_map(vm_offset_t vaddr, pt_entry_t pte) {
        arm_vm_map(cpu_tte, vaddr, pte);
}

/*
 * arm_vm_kernel_pte:
 *   vaddr: The target virtual address
 *
 * This function returns the PTE value for the given vaddr from the kernel page
 * tables.  If the region has been been block mapped, we return what an
 * equivalent PTE value would be (as regards permissions and flags).  We also
 * remove the HINT bit (as we are not necessarily creating contiguous mappings.
 */
static pt_entry_t
arm_vm_kernel_pte(vm_offset_t vaddr)
{
        tt_entry_t * ttp = cpu_tte;
        tt_entry_t * ttep = NULL;
        tt_entry_t tte = 0;
        pt_entry_t * ptep = NULL;
        pt_entry_t pte = 0;

#if !__ARM64_TWO_LEVEL_PMAP__
        ttep = ttp + ((vaddr & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT);
        tte = *ttep;

        assert(tte & ARM_TTE_VALID);

        if ((tte & ARM_TTE_TYPE_MASK) == ARM_TTE_TYPE_BLOCK) {
                /* This is a block mapping; return the equivalent PTE value. */
                pte = (pt_entry_t)(tte & ~ARM_TTE_TYPE_MASK);
                pte |= ARM_PTE_TYPE_VALID;
                pte |= vaddr & ((ARM_TT_L1_SIZE - 1) & ARM_PTE_PAGE_MASK);
                pte &= ~ARM_PTE_HINT_MASK;
                return pte;
        }

        ttp = (tt_entry_t *)phystokv(tte & ARM_TTE_TABLE_MASK);
#endif
        ttep = ttp + ((vaddr & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
        tte = *ttep;

        assert(tte & ARM_TTE_VALID);

        if ((tte & ARM_TTE_TYPE_MASK) == ARM_TTE_TYPE_BLOCK) {
                /* This is a block mapping; return the equivalent PTE value. */
                pte = (pt_entry_t)(tte & ~ARM_TTE_TYPE_MASK);
                pte |= ARM_PTE_TYPE_VALID;
                pte |= vaddr & ((ARM_TT_L2_SIZE - 1) & ARM_PTE_PAGE_MASK);
                pte &= ~ARM_PTE_HINT_MASK;
                return pte;
        }

        ttp = (tt_entry_t *)phystokv(tte & ARM_TTE_TABLE_MASK);

        ptep = ttp + ((vaddr & ARM_TT_L3_INDEX_MASK) >> ARM_TT_L3_SHIFT);
        pte = *ptep;
        pte &= ~ARM_PTE_HINT_MASK;
        return pte;
}

/*
 * arm_vm_prepare_kernel_el0_mappings:
 *   alloc_only: Indicates if PTE values should be copied from the EL1 kernel
 *     mappings.
 *
 * This function expands the kernel page tables to support the EL0 kernel
 * mappings, and conditionally installs the PTE values for the EL0 kernel
 * mappings (if alloc_only is false).
 */
static void
arm_vm_prepare_kernel_el0_mappings(bool alloc_only)
{
        pt_entry_t pte = 0;
        vm_offset_t start = ((vm_offset_t)&ExceptionVectorsBase) & ~PAGE_MASK;
        vm_offset_t end = (((vm_offset_t)&ExceptionVectorsEnd) + PAGE_MASK) & ~PAGE_MASK;
        vm_offset_t cur = 0;
        vm_offset_t cur_fixed = 0;

        /* Expand for/map the exceptions vectors in the EL0 kernel mappings. */
        for (cur = start, cur_fixed = ARM_KERNEL_PROTECT_EXCEPTION_START; cur < end; cur += ARM_PGBYTES, cur_fixed += ARM_PGBYTES) {
                /*
                 * We map the exception vectors at a different address than that
                 * of the kernelcache to avoid sharing page table pages with the
                 * kernelcache (as this may cause issues with TLB caching of
                 * page table pages.
                 */
                if (!alloc_only) {
                        pte = arm_vm_kernel_pte(cur);
                }

                arm_vm_kernel_el1_map(cur_fixed, pte);
                arm_vm_kernel_el0_map(cur_fixed, pte);
        }

        __builtin_arm_dmb(DMB_ISH);
        __builtin_arm_isb(ISB_SY);

        if (!alloc_only) {
                /*
                 * If we have created the alternate exception vector mappings,
                 * the boot CPU may now switch over to them.
                 */
                set_vbar_el1(ARM_KERNEL_PROTECT_EXCEPTION_START);
                __builtin_arm_isb(ISB_SY);
        }
}

/*
 * arm_vm_populate_kernel_el0_mappings:
 *
 * This function adds all required mappings to the EL0 kernel mappings.
 */
static void
arm_vm_populate_kernel_el0_mappings(void)
{
        arm_vm_prepare_kernel_el0_mappings(FALSE);
}

/*
 * arm_vm_expand_kernel_el0_mappings:
 *
 * This function expands the kernel page tables to accomodate the EL0 kernel
 * mappings.
 */
static void
arm_vm_expand_kernel_el0_mappings(void)
{
        arm_vm_prepare_kernel_el0_mappings(TRUE);
}
#endif /* __ARM_KERNEL_PROTECT__ */

#if defined(KERNEL_INTEGRITY_KTRR)
extern void bootstrap_instructions;

/*
 * arm_replace_identity_map takes the V=P map that we construct in start.s
 * and repurposes it in order to have it map only the page we need in order
 * to turn on the MMU.  This prevents us from running into issues where
 * KTRR will cause us to fault on executable block mappings that cross the
 * KTRR boundary.
 */
static void arm_replace_identity_map(boot_args * args)
{
        vm_offset_t addr;
        pmap_paddr_t paddr;

#if !__ARM64_TWO_LEVEL_PMAP__
        pmap_paddr_t l1_ptp_phys = 0;
        tt_entry_t *l1_ptp_virt = NULL;
        tt_entry_t *tte1 = NULL;
#endif
        pmap_paddr_t l2_ptp_phys = 0;
        tt_entry_t *l2_ptp_virt = NULL;
        tt_entry_t *tte2 = NULL;
        pmap_paddr_t l3_ptp_phys = 0;
        pt_entry_t *l3_ptp_virt = NULL;
        pt_entry_t *ptep = NULL;

        addr = ((vm_offset_t)&bootstrap_instructions) & ~ARM_PGMASK;
        paddr = kvtophys(addr);

        /*
         * The V=P page tables (at the time this comment was written) start
         * after the last bit of kernel data, and consist of 1 to 2 pages.
         * Grab references to those pages, and allocate an L3 page.
         */
#if !__ARM64_TWO_LEVEL_PMAP__
        l1_ptp_phys = args->topOfKernelData;
        l1_ptp_virt = (tt_entry_t *)phystokv(l1_ptp_phys);
        tte1 = &l1_ptp_virt[(((paddr) & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT)];

        l2_ptp_phys = l1_ptp_phys + ARM_PGBYTES;
#else
        l2_ptp_phys = args->topOfKernelData;
#endif
        l2_ptp_virt = (tt_entry_t *)phystokv(l2_ptp_phys);
        tte2 = &l2_ptp_virt[(((paddr) & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT)];

        l3_ptp_virt = (pt_entry_t *)alloc_ptpage(FALSE);
        l3_ptp_phys = kvtophys((vm_offset_t)l3_ptp_virt);
        ptep = &l3_ptp_virt[(((paddr) & ARM_TT_L3_INDEX_MASK) >> ARM_TT_L3_SHIFT)];

        /*
         * Replace the large V=P mapping with a mapping that provides only the
         * mappings needed to turn on the MMU.
         */
#if !__ARM64_TWO_LEVEL_PMAP__
        bzero(l1_ptp_virt, ARM_PGBYTES);
        *tte1 = ARM_TTE_BOOT_TABLE | (l2_ptp_phys & ARM_TTE_TABLE_MASK);
#endif
        bzero(l2_ptp_virt, ARM_PGBYTES);
        *tte2 = ARM_TTE_BOOT_TABLE | (l3_ptp_phys & ARM_TTE_TABLE_MASK);

        *ptep = (paddr & ARM_PTE_MASK) |
                ARM_PTE_TYPE_VALID |
                ARM_PTE_SH(SH_OUTER_MEMORY) |
                ARM_PTE_ATTRINDX(CACHE_ATTRINDX_WRITEBACK) |
                ARM_PTE_AF |
                ARM_PTE_AP(AP_RONA) |
                ARM_PTE_NX;
}
#endif /* defined(KERNEL_INTEGRITY_KTRR)*/

/*
 * arm_vm_page_granular_helper updates protections at the L3 level.  It will (if
 * neccessary) allocate a page for the L3 table and update the corresponding L2
 * entry.  Then, it will iterate over the L3 table, updating protections as necessary.
 * This expects to be invoked on a L2 entry or sub L2 entry granularity, so this should
 * not be invoked from a context that does not do L2 iteration separately (basically,
 * don't call this except from arm_vm_page_granular_prot).
 */
static void
arm_vm_page_granular_helper(vm_offset_t start, vm_offset_t _end, vm_offset_t va,
                            int pte_prot_APX, int pte_prot_XN, int forceCoarse,
                            pt_entry_t **deferred_pte, pt_entry_t *deferred_ptmp)
{
        if (va & ARM_TT_L2_OFFMASK) { /* ragged edge hanging over a ARM_TT_L2_SIZE  boundary */
#if __ARM64_TWO_LEVEL_PMAP__
                tt_entry_t *tte2;
#else
                tt_entry_t *tte1, *tte2;
#endif
                tt_entry_t tmplate;
                pmap_paddr_t pa;
                pt_entry_t *ppte, *recursive_pte = NULL, ptmp, recursive_ptmp = 0;
                addr64_t ppte_phys;
                unsigned i;

                va &= ~ARM_TT_L2_OFFMASK;
                pa = va - gVirtBase + gPhysBase;

#if __ARM64_TWO_LEVEL_PMAP__
                tte2 = &cpu_tte[(((va) & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT)];
#else
                tte1 = &cpu_tte[(((va) & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT)];
                tte2 = &((tt_entry_t*) phystokv((*tte1) & ARM_TTE_TABLE_MASK))[(((va) & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT)];
#endif

                tmplate = *tte2;

                if (ARM_TTE_TYPE_TABLE == (tmplate & ARM_TTE_TYPE_MASK)) {
                        /* pick up the existing page table. */
                        ppte = (pt_entry_t *)phystokv((tmplate & ARM_TTE_TABLE_MASK));
                } else {
                        // TTE must be reincarnated COARSE.
                        ppte = (pt_entry_t*)alloc_ptpage(TRUE);
                        ppte_phys = kvtophys((vm_offset_t)ppte);

                        pmap_init_pte_static_page(kernel_pmap, ppte, pa);

                        *tte2 = pa_to_tte(ppte_phys) | ARM_TTE_TYPE_TABLE  | ARM_TTE_VALID;
                }

                /* Apply the desired protections to the specified page range */
                for (i = 0; i <= (ARM_TT_L3_INDEX_MASK>>ARM_TT_L3_SHIFT); i++) {
                        if ((start <= va) && (va < _end)) {

                                ptmp = pa | ARM_PTE_AF | ARM_PTE_SH(SH_OUTER_MEMORY) | ARM_PTE_TYPE;
                                ptmp = ptmp | ARM_PTE_ATTRINDX(CACHE_ATTRINDX_DEFAULT);
                                ptmp = ptmp | ARM_PTE_AP(pte_prot_APX);
                                ptmp = ptmp | ARM_PTE_NX;
#if __ARM_KERNEL_PROTECT__
                                ptmp = ptmp | ARM_PTE_NG;
#endif /* __ARM_KERNEL_PROTECT__ */

                                if (pte_prot_XN) {
                                        ptmp = ptmp | ARM_PTE_PNX;
                                }

                                /*
                                 * If we can, apply the contiguous hint to this range.  The hint is
                                 * applicable if we are not trying to create per-page mappings and
                                 * if the current address falls within a hint-sized range that will
                                 * be fully covered by this mapping request.
                                 */
                                if ((va >= round_up_pte_hint_address(start)) && (round_up_pte_hint_address(va + 1) < _end) &&
                                    !forceCoarse && use_contiguous_hint) {
                                        ptmp |= ARM_PTE_HINT;
                                }

                                if ((pt_entry_t*)(phystokv(pa)) == ppte) {
                                        assert(recursive_pte == NULL);  
                                        /* This assert should be reenabled as part of rdar://problem/30149465 */
                                        assert(!forceCoarse);
                                        recursive_pte = &ppte[i];
                                        recursive_ptmp = ptmp;
                                } else if ((deferred_pte != NULL) && (&ppte[i] == &recursive_pte[1])) {
                                        assert(*deferred_pte == NULL);
                                        assert(deferred_ptmp != NULL);
                                        *deferred_pte = &ppte[i];
                                        *deferred_ptmp = ptmp;
                                } else {
                                        ppte[i] = ptmp;
                                }
                        }

                        va += ARM_PGBYTES;
                        pa += ARM_PGBYTES;
                }
                if (recursive_pte != NULL)
                        *recursive_pte = recursive_ptmp;
        }
}

/*
 * arm_vm_page_granular_prot updates protections by iterating over the L2 entries and
 * changing them.  If a particular chunk necessitates L3 entries (for reasons of
 * alignment or length, or an explicit request that the entry be fully expanded), we
 * hand off to arm_vm_page_granular_helper to deal with the L3 chunk of the logic.
 *
 * Note that counterintuitively a forceCoarse request is a request to expand the entries
 * out to L3, i.e. to make *finer* grained mappings. That comes from historical arm32
 * nomenclature in which the 4K granule is "coarse" vs. the 1K "fine" granule (which we
 * don't use). 
 */
static void
arm_vm_page_granular_prot(vm_offset_t start, unsigned long size,
                          int tte_prot_XN, int pte_prot_APX, int pte_prot_XN, int forceCoarse)
{
        pt_entry_t *deferred_pte = NULL, deferred_ptmp = 0;
        vm_offset_t _end = start + size;
        vm_offset_t align_start = (start + ARM_TT_L2_OFFMASK) & ~ARM_TT_L2_OFFMASK;

        if (size == 0x0UL)
                return;

        if (align_start > _end) {
                arm_vm_page_granular_helper(start, _end, start, pte_prot_APX, pte_prot_XN, forceCoarse, NULL, NULL);
                return;
        }

        arm_vm_page_granular_helper(start, align_start, start, pte_prot_APX, pte_prot_XN, forceCoarse, &deferred_pte, &deferred_ptmp);

        while ((_end - align_start)  >= ARM_TT_L2_SIZE) {
                if (forceCoarse)
                        arm_vm_page_granular_helper(align_start, align_start+ARM_TT_L2_SIZE, align_start + 1,
                                                    pte_prot_APX, pte_prot_XN, forceCoarse, NULL, NULL);
                else {
#if __ARM64_TWO_LEVEL_PMAP__
                        tt_entry_t *tte2;
#else
                        tt_entry_t *tte1, *tte2;
#endif
                        tt_entry_t tmplate;

#if __ARM64_TWO_LEVEL_PMAP__
                        tte2 = &cpu_tte[((align_start & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT)];
#else
                        tte1 = &cpu_tte[((align_start & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT)];
                        tte2 = &((tt_entry_t*) phystokv((*tte1) & ARM_TTE_TABLE_MASK))[((align_start & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT)];
#endif

                        tmplate = *tte2;

                        tmplate = (tmplate & ~ARM_TTE_BLOCK_APMASK) | ARM_TTE_BLOCK_AP(pte_prot_APX);
                        tmplate = tmplate | ARM_TTE_BLOCK_NX;
#if __ARM_KERNEL_PROTECT__
                        tmplate = tmplate | ARM_TTE_BLOCK_NG;
#endif /* __ARM_KERNEL_PROTECT__ */
                        if (tte_prot_XN)
                                tmplate = tmplate | ARM_TTE_BLOCK_PNX;

                        *tte2 = tmplate;
                }
                align_start += ARM_TT_L2_SIZE;
        }

        if (align_start < _end)
                arm_vm_page_granular_helper(align_start, _end, _end, pte_prot_APX, pte_prot_XN, forceCoarse, &deferred_pte, &deferred_ptmp);

        if (deferred_pte != NULL)
                *deferred_pte = deferred_ptmp;
}

static inline void
arm_vm_page_granular_RNX(vm_offset_t start, unsigned long size, int forceCoarse)
{
        arm_vm_page_granular_prot(start, size, 1, AP_RONA, 1, forceCoarse);
}

static inline void
arm_vm_page_granular_ROX(vm_offset_t start, unsigned long size, int forceCoarse)
{
        arm_vm_page_granular_prot(start, size, 0, AP_RONA, 0, forceCoarse);
}

static inline void
arm_vm_page_granular_RWNX(vm_offset_t start, unsigned long size, int forceCoarse)
{
        arm_vm_page_granular_prot(start, size, 1, AP_RWNA, 1, forceCoarse);
}

static inline void
arm_vm_page_granular_RWX(vm_offset_t start, unsigned long size, int forceCoarse)
{
        arm_vm_page_granular_prot(start, size, 0, AP_RWNA, 0, forceCoarse);
}

void
arm_vm_prot_init(boot_args * args)
{
        /*
         * Enforce W^X protections on sections that have been identified so far. This will be
         * further refined for each KEXT's TEXT and DATA segments in readPrelinkedExtensions()
         */
        bool use_small_page_mappings = FALSE;

        /*
         * First off, we'll create mappings for any physical memory preceeding the kernel TEXT.
         * This is memory that we want to give to the VM; this will be accomplished through an
         * ml_static_mfree call in arm_vm_prot_finalize.  This allows the pmap/vm bootstrap
         * routines to assume they will have a physically contiguous chunk of memory to deal
         * with during bootstrap, while reclaiming this memory later.
         */
        arm_vm_page_granular_RWNX(gVirtBase, segPRELINKTEXTB - gVirtBase, use_small_page_mappings); // Memory for the VM

        /* Map coalesced kext TEXT segment RWNX for now */
        arm_vm_page_granular_RWNX(segPRELINKTEXTB, segSizePRELINKTEXT, FALSE); // Refined in OSKext::readPrelinkedExtensions

        /* Map coalesced kext DATA_CONST segment RWNX (could be empty) */
        arm_vm_page_granular_RWNX(segPLKDATACONSTB, segSizePLKDATACONST, FALSE); // Refined in OSKext::readPrelinkedExtensions

        /* Map coalesced kext TEXT_EXEC segment RWX (could be empty) */
        arm_vm_page_granular_ROX(segPLKTEXTEXECB, segSizePLKTEXTEXEC, FALSE); // Refined in OSKext::readPrelinkedExtensions

        /* if new segments not present, set space between PRELINK_TEXT and xnu TEXT to RWNX
         * otherwise we no longer expecting any space between the coalesced kext read only segments and xnu rosegments
         */
        if (!segSizePLKDATACONST && !segSizePLKTEXTEXEC) {
                arm_vm_page_granular_RWNX(segPRELINKTEXTB + segSizePRELINKTEXT, segTEXTB - (segPRELINKTEXTB + segSizePRELINKTEXT), FALSE);
        } else {
                /*
                 * If we have the new segments, we should still protect the gap between kext
                 * read-only pages and kernel read-only pages, in the event that this gap
                 * exists.
                 */
                if ((segPLKDATACONSTB + segSizePLKDATACONST) < segTEXTB) {
                        arm_vm_page_granular_RWNX(segPLKDATACONSTB + segSizePLKDATACONST, segTEXTB - (segPLKDATACONSTB + segSizePLKDATACONST), FALSE);
                }
        }

        /*
         * Protection on kernel text is loose here to allow shenanigans early on.  These
         * protections are tightened in arm_vm_prot_finalize().  This is necessary because
         * we currently patch LowResetVectorBase in cpu.c.
         *
         * TEXT segment contains mach headers and other non-executable data. This will become RONX later.
         */
        arm_vm_page_granular_RNX(segTEXTB, segSizeTEXT, FALSE);

        /* Can DATACONST start out and stay RNX?
         * NO, stuff in this segment gets modified during startup (viz. mac_policy_init()/mac_policy_list)
         * Make RNX in prot_finalize
         */
        arm_vm_page_granular_RWNX(segDATACONSTB, segSizeDATACONST, FALSE);

        /* TEXTEXEC contains read only executable code: becomes ROX in prot_finalize */
        arm_vm_page_granular_RWX(segTEXTEXECB, segSizeTEXTEXEC, FALSE);


        /* DATA segment will remain RWNX */
        arm_vm_page_granular_RWNX(segDATAB, segSizeDATA, FALSE);

        arm_vm_page_granular_ROX(segKLDB, segSizeKLD, FALSE);
        arm_vm_page_granular_RWNX(segLINKB, segSizeLINK, FALSE);
        arm_vm_page_granular_ROX(segLASTB, segSizeLAST, FALSE); // __LAST may be empty, but we cannot assume this

        arm_vm_page_granular_RWNX(segPRELINKDATAB, segSizePRELINKDATA, FALSE); // Prelink __DATA for kexts (RW data)

        if (segSizePLKLLVMCOV > 0)
                arm_vm_page_granular_RWNX(segPLKLLVMCOVB, segSizePLKLLVMCOV, FALSE); // LLVM code coverage data

        arm_vm_page_granular_RWNX(segPLKLINKEDITB, segSizePLKLINKEDIT, use_small_page_mappings); // Coalesced kext LINKEDIT segment

        arm_vm_page_granular_RWNX(segPRELINKINFOB, segSizePRELINKINFO, FALSE); /* PreLinkInfoDictionary */
        arm_vm_page_granular_RWNX(end_kern, phystokv(args->topOfKernelData) - end_kern, use_small_page_mappings); /* Device Tree, RAM Disk (if present), bootArgs */

        /*
         * This is offset by 4 pages to make room for the boot page tables; we could probably
         * include them in the overall mapping, but we'll be paranoid for now.
         */
        vm_offset_t extra = 0;
#if KASAN
        /* add the KASAN stolen memory to the physmap */
        extra = shadow_ptop - shadow_pbase;

        /* record the extent of the physmap */
        physmap_vbase = phystokv(args->topOfKernelData) + ARM_PGBYTES * 4;
        physmap_vtop = static_memory_end;
#endif
        arm_vm_page_granular_RNX(phystokv(args->topOfKernelData), ARM_PGBYTES * 4, FALSE); // Boot page tables; they should not be mutable.
        arm_vm_page_granular_RWNX(phystokv(args->topOfKernelData) + ARM_PGBYTES * 4,
                                  extra + static_memory_end - ((phystokv(args->topOfKernelData) + ARM_PGBYTES * 4)), use_small_page_mappings); // rest of physmem
}

void
arm_vm_prot_finalize(boot_args * args)
{
#pragma unused(args)
        /*
         * At this point, we are far enough along in the boot process that it will be
         * safe to free up all of the memory preceeding the kernel.  It may in fact
         * be safe to do this earlier.
         *
         * This keeps the memory in the V-to-P mapping, but advertises it to the VM
         * as usable.
         */

        /*
         * if old style PRELINK segment exists, free memory before it, and after it before XNU text
         * otherwise we're dealing with a new style kernel cache, so we should just free the
         * memory before PRELINK_TEXT segment, since the rest of the KEXT read only data segments
         * should be immediately followed by XNU's TEXT segment
         */

        ml_static_mfree(gVirtBase, segPRELINKTEXTB - gVirtBase);

        if (!segSizePLKDATACONST && !segSizePLKTEXTEXEC) {
                /* If new segments not present, PRELINK_TEXT is not dynamically sized, free DRAM between it and xnu TEXT */
                ml_static_mfree(segPRELINKTEXTB + segSizePRELINKTEXT, segTEXTB - (segPRELINKTEXTB + segSizePRELINKTEXT));
        }

        /*
         * LowResetVectorBase patching should be done by now, so tighten executable
         * protections.
         */
        arm_vm_page_granular_ROX(segTEXTEXECB, segSizeTEXTEXEC, FALSE);

        /* tighten permissions on kext read only data and code */
        if (segSizePLKDATACONST && segSizePLKTEXTEXEC) {
                arm_vm_page_granular_RNX(segPRELINKTEXTB, segSizePRELINKTEXT, FALSE);
                arm_vm_page_granular_ROX(segPLKTEXTEXECB, segSizePLKTEXTEXEC, FALSE);
                arm_vm_page_granular_RNX(segPLKDATACONSTB, segSizePLKDATACONST, FALSE);
        }

#if __ARM_KERNEL_PROTECT__
        arm_vm_populate_kernel_el0_mappings();
#endif /* __ARM_KERNEL_PROTECT__ */

#if defined(KERNEL_INTEGRITY_KTRR)
        /*
         * __LAST,__pinst should no longer be executable.
         */
        arm_vm_page_granular_RNX(segLASTB, segSizeLAST, FALSE);

        /*
         * Must wait until all other region permissions are set before locking down DATA_CONST
         * as the kernel static page tables live in DATA_CONST on KTRR enabled systems
         * and will become immutable.
         */
#endif

        arm_vm_page_granular_RNX(segDATACONSTB, segSizeDATACONST, FALSE);

#ifndef __ARM_L1_PTW__
        FlushPoC_Dcache();
#endif
        flush_mmu_tlb();
}

#define TBI_USER 0x1
#define TBI_KERNEL 0x2

boolean_t user_tbi = TRUE;

/*
 * TBI (top-byte ignore) is an ARMv8 feature for ignoring the top 8 bits of
 * address accesses. It can be enabled separately for TTBR0 (user) and
 * TTBR1 (kernel). We enable it by default for user only, but allow both
 * to be controlled by the 'tbi' boot-arg.
 */
static void
set_tbi(void)
{
#if !__ARM_KERNEL_PROTECT__
        /* If we are not built with __ARM_KERNEL_PROTECT__, TBI can be turned
         * off with a boot-arg.
         */
        uint64_t old_tcr, new_tcr;
        int tbi = 0;

        if (PE_parse_boot_argn("tbi", &tbi, sizeof(tbi)))
                user_tbi = ((tbi & TBI_USER) == TBI_USER);
        old_tcr = new_tcr = get_tcr();
        new_tcr |= (user_tbi) ? TCR_TBI0_TOPBYTE_IGNORED : 0;
        new_tcr |= (tbi & TBI_KERNEL) ? TCR_TBI1_TOPBYTE_IGNORED : 0;

        if (old_tcr != new_tcr) {
                set_tcr(new_tcr);
                sysreg_restore.tcr_el1 = new_tcr;
        }
#endif /* !__ARM_KERNEL_PROTECT__ */
}

void
arm_vm_init(uint64_t memory_size, boot_args * args)
{
#if !__ARM64_TWO_LEVEL_PMAP__
        vm_map_address_t va_l1, va_l1_end;
        pmap_paddr_t     pa_l1;
        tt_entry_t       *cpu_l1_tte;
#else
        /*
         * If we are using two level page tables, rather than the
         * 3 level page tables that xnu defaults to for ARM64,
         * then a great deal of the code in this path becomes
         * redundant.  As a result, most of the logic having to
         * do with L1 pages will be excluded from such
         * configurations in this function.
         */
#endif
        vm_map_address_t va_l2, va_l2_end;
        pmap_paddr_t     pa_l2;
        tt_entry_t       *cpu_l2_tte;
        pmap_paddr_t     boot_ttep;
        tt_entry_t       *boot_tte;
        uint64_t         mem_segments;
        vm_offset_t      ptpage_vaddr;


        /*
         * Get the virtual and physical memory base from boot_args.
         */
        gVirtBase = args->virtBase;
        gPhysBase = args->physBase;
        gPhysSize = args->memSize;
        mem_size = args->memSize;
        if ((memory_size != 0) && (mem_size > memory_size))
                mem_size = memory_size;
        if (mem_size > MEM_SIZE_MAX )
                mem_size = MEM_SIZE_MAX;
        static_memory_end = gVirtBase + mem_size;

        boot_ttep = args->topOfKernelData;
        boot_tte = (tt_entry_t *) phystokv(boot_ttep);

        /* 
         * Four pages: 
         *  TTBR0 L1, TTBR0 L2 - 1:1 bootstrap mapping.
         *  TTBR1 L1, TTBR1 L2 - kernel mapping
         */
        avail_start = boot_ttep + 4*ARM_PGBYTES; 

#if defined(KERNEL_INTEGRITY_KTRR)
        arm_replace_identity_map(args);
#endif

        /* Initialize invalid tte page */
        invalid_tte = (tt_entry_t *)alloc_ptpage(TRUE);
        invalid_ttep = kvtophys((vm_offset_t)invalid_tte);
        bzero(invalid_tte, ARM_PGBYTES);

        /*
         * Initialize l1 page table page
         */
#if __ARM64_TWO_LEVEL_PMAP__
        /*
         * If we're using a two level page table, we still need to
         * set the cpu_ttep to avail_start, as this will be the root
         * of our page table regardless of how many levels we are
         * using.
         */
#endif
        cpu_tte = (tt_entry_t *)alloc_ptpage(TRUE);
        cpu_ttep = kvtophys((vm_offset_t)cpu_tte);
        bzero(cpu_tte, ARM_PGBYTES);
        avail_end = gPhysBase + mem_size;

        /*
         * Initialize l1 and l2 page table pages :
         *   map physical memory at the kernel base virtual address
         *   cover the kernel dynamic address range section
         *
         *   the so called physical aperture should be statically mapped
         */
#if !__ARM64_TWO_LEVEL_PMAP__
        pa_l1 = gPhysBase;
        va_l1 = gVirtBase;
        va_l1_end = gVirtBase + mem_size;
#if KASAN
        /* add the KASAN stolen memory to the physmap */
        va_l1_end = gVirtBase + (shadow_ptop - gPhysBase);
#endif
        cpu_l1_tte = cpu_tte + ((va_l1 & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT);

        while (va_l1 < va_l1_end) {
                tt_entry_t *new_tte = (tt_entry_t *)alloc_ptpage(TRUE);
                /* Allocate a page and setup L1 Table TTE in L1 */
                *cpu_l1_tte = (kvtophys((vm_offset_t)new_tte) & ARM_TTE_TABLE_MASK)  | ARM_TTE_TYPE_TABLE | ARM_TTE_VALID;
                bzero((void *)new_tte, ARM_PGBYTES);

                va_l2 = va_l1;

                if (((va_l1 & ~ARM_TT_L1_OFFMASK)+ARM_TT_L1_SIZE) < va_l1) {
                        /* If this is the last L1 entry, it must cover the last mapping. */
                        va_l2_end = va_l1_end;
                } else {
                        va_l2_end = MIN((va_l1 & ~ARM_TT_L1_OFFMASK)+ARM_TT_L1_SIZE, va_l1_end);
                }

                pa_l2 = pa_l1;
                cpu_l2_tte = ((tt_entry_t *) phystokv(((*cpu_l1_tte) & ARM_TTE_TABLE_MASK))) + ((va_l1 & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
#else
                va_l2 = gVirtBase;
                va_l2_end = gVirtBase + mem_size;
                pa_l2 = gPhysBase;
                cpu_l2_tte = cpu_tte + ((va_l2 & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);

#if KASAN
                /* add the KASAN stolen memory to the physmap */
                va_l2_end = gVirtBase + (shadow_ptop - gPhysBase);
#endif

#endif

                while (va_l2 < va_l2_end) {
                        /* Set up L2 Block TTE in L2 */
                        *cpu_l2_tte = (pa_l2 & ARM_TTE_BLOCK_L2_MASK) | ARM_TTE_TYPE_BLOCK
                                      | ARM_TTE_VALID | ARM_TTE_BLOCK_AF
                                      | ARM_TTE_BLOCK_AP(AP_RWNA) | ARM_TTE_BLOCK_SH(SH_OUTER_MEMORY)
                                      | ARM_TTE_BLOCK_ATTRINDX(CACHE_ATTRINDX_WRITEBACK);
#if __ARM_KERNEL_PROTECT__
                        *cpu_l2_tte |= ARM_TTE_BLOCK_NG;
#endif /* __ARM_KERNEL_PROTECT__ */
                        va_l2 += ARM_TT_L2_SIZE;
                        pa_l2 += ARM_TT_L2_SIZE;
                        cpu_l2_tte++;
                }
#if !__ARM64_TWO_LEVEL_PMAP__
                cpu_l1_tte++;
                va_l1 = va_l2;
                pa_l1 = pa_l2;
        }
#endif

#if __ARM_KERNEL_PROTECT__
        /* Expand the page tables to prepare for the EL0 mappings. */
        arm_vm_expand_kernel_el0_mappings();
#endif /* __ARM_KERNEL_PROTECT__ */

        /*
         * Now retrieve addresses for end, edata, and etext from MACH-O headers
         */
        segPRELINKTEXTB  = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__PRELINK_TEXT", &segSizePRELINKTEXT);
        segPLKDATACONSTB = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__PLK_DATA_CONST", &segSizePLKDATACONST);
        segPLKTEXTEXECB  = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__PLK_TEXT_EXEC", &segSizePLKTEXTEXEC);
        segTEXTB         = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__TEXT", &segSizeTEXT);
        segDATACONSTB    = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__DATA_CONST", &segSizeDATACONST);
        segTEXTEXECB     = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__TEXT_EXEC", &segSizeTEXTEXEC);
        segDATAB         = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__DATA", &segSizeDATA);
        segLINKB         = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__LINKEDIT", &segSizeLINK);
        segKLDB          = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__KLD", &segSizeKLD);
        segPRELINKDATAB  = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__PRELINK_DATA", &segSizePRELINKDATA);
        segPRELINKINFOB  = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__PRELINK_INFO", &segSizePRELINKINFO);
        segPLKLLVMCOVB   = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__PLK_LLVM_COV", &segSizePLKLLVMCOV);
        segPLKLINKEDITB  = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__PLK_LINKEDIT", &segSizePLKLINKEDIT);
        segLASTB         = (vm_offset_t) getsegdatafromheader(&_mh_execute_header, "__LAST", &segSizeLAST);

        (void) PE_parse_boot_argn("use_contiguous_hint", &use_contiguous_hint, sizeof(use_contiguous_hint));
        assert(segSizePRELINKTEXT < 0x03000000); /* 23355738 */

        /* if one of the new segments is present, the other one better be as well */
        if (segSizePLKDATACONST || segSizePLKTEXTEXEC) {
                assert(segSizePLKDATACONST && segSizePLKTEXTEXEC);
        }

        etext = (vm_offset_t) segTEXTB + segSizeTEXT;
        sdata = (vm_offset_t) segDATAB;
        edata = (vm_offset_t) segDATAB + segSizeDATA;
        end_kern = round_page(getlastaddr());      /* Force end to next page */

        vm_set_page_size();

        vm_kernel_base = segTEXTB;
        vm_kernel_top = (vm_offset_t) &last_kernel_symbol;
        vm_kext_base = segPRELINKTEXTB;
        vm_kext_top = vm_kext_base + segSizePRELINKTEXT;

        vm_prelink_stext = segPRELINKTEXTB;
        if (!segSizePLKTEXTEXEC && !segSizePLKDATACONST) {
                vm_prelink_etext = segPRELINKTEXTB + segSizePRELINKTEXT;
        } else {
                vm_prelink_etext = segPRELINKTEXTB + segSizePRELINKTEXT + segSizePLKDATACONST + segSizePLKTEXTEXEC;
        }
        vm_prelink_sinfo = segPRELINKINFOB;
        vm_prelink_einfo = segPRELINKINFOB + segSizePRELINKINFO;
        vm_slinkedit = segLINKB;
        vm_elinkedit = segLINKB + segSizeLINK;

        vm_prelink_sdata = segPRELINKDATAB;
        vm_prelink_edata = segPRELINKDATAB + segSizePRELINKDATA;

        arm_vm_prot_init(args);


        /*
         * Initialize the page tables for the low globals:
         *   cover this address range:
         *     LOW_GLOBAL_BASE_ADDRESS + 2MB
         */
#if __ARM64_TWO_LEVEL_PMAP__
        va_l2 = LOW_GLOBAL_BASE_ADDRESS;
        cpu_l2_tte = cpu_tte + ((va_l2 & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
#else
        va_l1 = va_l2 = LOW_GLOBAL_BASE_ADDRESS;
        cpu_l1_tte = cpu_tte + ((va_l1 & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT);
        cpu_l2_tte = ((tt_entry_t *) phystokv(((*cpu_l1_tte) & ARM_TTE_TABLE_MASK))) + ((va_l2 & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
#endif
        ptpage_vaddr = alloc_ptpage(TRUE);
        *cpu_l2_tte = (kvtophys(ptpage_vaddr) & ARM_TTE_TABLE_MASK) | ARM_TTE_TYPE_TABLE | ARM_TTE_VALID | ARM_TTE_TABLE_PXN | ARM_TTE_TABLE_XN;
        bzero((void *)ptpage_vaddr, ARM_PGBYTES);

        /*
         * Initialize l2 page table pages :
         *   cover this address range:
         *    KERNEL_DYNAMIC_ADDR - VM_MAX_KERNEL_ADDRESS
         */
#if !__ARM64_TWO_LEVEL_PMAP__
        va_l1 = (gVirtBase+MEM_SIZE_MAX+ ~0xFFFFFFFFFF800000ULL) & 0xFFFFFFFFFF800000ULL;
        va_l1_end = VM_MAX_KERNEL_ADDRESS;
        cpu_l1_tte = cpu_tte + ((va_l1 & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT);

        while (va_l1 < va_l1_end) {
                if (*cpu_l1_tte == ARM_TTE_EMPTY) {
                        /* Allocate a page and setup L1 Table TTE in L1 */
                        ptpage_vaddr = alloc_ptpage(TRUE);
                        *cpu_l1_tte = (kvtophys(ptpage_vaddr) & ARM_TTE_TABLE_MASK) | ARM_TTE_TYPE_TABLE | ARM_TTE_VALID | ARM_TTE_TABLE_PXN | ARM_TTE_TABLE_XN;
                        bzero((void *)ptpage_vaddr, ARM_PGBYTES);
                }

                if ((va_l1 + ARM_TT_L1_SIZE) < va_l1) {
                        /* If this is the last L1 entry, it must cover the last mapping. */
                        break;
                }

                va_l1 += ARM_TT_L1_SIZE;
                cpu_l1_tte++;
        }
#endif

#if KASAN
        kasan_init();
#endif

        set_mmu_ttb(invalid_ttep & TTBR_BADDR_MASK);
        set_mmu_ttb_alternate(cpu_ttep & TTBR_BADDR_MASK);
        set_tbi();
        flush_mmu_tlb();

        /*
         * TODO: We're hardcoding the expected virtual TEXT base here;
         * that gives us an ugly dependency on a linker argument in
         * the make files.  Clean this up, so we don't hardcode it
         * twice; this is nothing but trouble.
         */
        sane_size = mem_size - (avail_start - gPhysBase);
        max_mem = mem_size;
        vm_kernel_slid_base = segPRELINKTEXTB;
        vm_kernel_slid_top = vm_prelink_einfo;
        vm_kernel_slide = segTEXTB-0xfffffff007004000;
        vm_kernel_stext = segTEXTB;
        assert(segDATACONSTB == segTEXTB + segSizeTEXT);
         assert(segTEXTEXECB == segDATACONSTB + segSizeDATACONST);
        vm_kernel_etext = segTEXTB + segSizeTEXT + segSizeDATACONST + segSizeTEXTEXEC;

        pmap_bootstrap((gVirtBase+MEM_SIZE_MAX+ ~0xFFFFFFFFFF800000ULL) & 0xFFFFFFFFFF800000ULL);

        /*
         * Initialize l3 page table pages :
         *   cover this address range:
         *    2MB + FrameBuffer size + 10MB for each 256MB segment
         */

        mem_segments = (mem_size + 0x0FFFFFFF) >> 28;

#if !__ARM64_TWO_LEVEL_PMAP__
        va_l1 = (gVirtBase+MEM_SIZE_MAX+ ~0xFFFFFFFFFF800000ULL) & 0xFFFFFFFFFF800000ULL;
        va_l1_end = va_l1 + ((2 + (mem_segments * 10)) << 20);
        va_l1_end += round_page(args->Video.v_height * args->Video.v_rowBytes);
        va_l1_end = (va_l1_end + 0x00000000007FFFFFULL) & 0xFFFFFFFFFF800000ULL;

        cpu_l1_tte = cpu_tte + ((va_l1 & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT);

        while (va_l1 < va_l1_end) {

                va_l2 = va_l1;

                if (((va_l1 & ~ARM_TT_L1_OFFMASK)+ARM_TT_L1_SIZE) < va_l1) {
                        /* If this is the last L1 entry, it must cover the last mapping. */
                        va_l2_end = va_l1_end;
                } else {
                        va_l2_end = MIN((va_l1 & ~ARM_TT_L1_OFFMASK)+ARM_TT_L1_SIZE, va_l1_end);
                }

                cpu_l2_tte = ((tt_entry_t *) phystokv(((*cpu_l1_tte) & ARM_TTE_TABLE_MASK))) + ((va_l2 & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
#else
                va_l2 = (gVirtBase+MEM_SIZE_MAX+ ~0xFFFFFFFFFF800000ULL) & 0xFFFFFFFFFF800000ULL;
                va_l2_end = va_l2 + ((2 + (mem_segments * 10)) << 20);
                va_l2_end += round_page(args->Video.v_height * args->Video.v_rowBytes);
                va_l2_end = (va_l2_end + 0x00000000007FFFFFULL) & 0xFFFFFFFFFF800000ULL;
                cpu_l2_tte = cpu_tte + ((va_l2 & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
#endif

                while (va_l2 < va_l2_end) {
                        pt_entry_t *    ptp;
                        pmap_paddr_t    ptp_phys;

                        /* Allocate a page and setup L3 Table TTE in L2 */
                        ptp = (pt_entry_t *) alloc_ptpage(FALSE);
                        ptp_phys = (pmap_paddr_t)kvtophys((vm_offset_t)ptp);

                        pmap_init_pte_page(kernel_pmap, ptp, va_l2, 3, TRUE);

                        *cpu_l2_tte = (pa_to_tte (ptp_phys)) | ARM_TTE_TYPE_TABLE | ARM_TTE_VALID | ARM_TTE_TABLE_PXN | ARM_TTE_TABLE_XN;

                        va_l2 += ARM_TT_L2_SIZE;
                        cpu_l2_tte++;
                };
#if !__ARM64_TWO_LEVEL_PMAP__
                va_l1 = va_l2_end;
                cpu_l1_tte++;
        }
#endif

        /*
         * Initialize l3 page table pages :
         *   cover this address range:
         *   (VM_MAX_KERNEL_ADDRESS & CPUWINDOWS_BASE_MASK) - VM_MAX_KERNEL_ADDRESS
         */
#if !__ARM64_TWO_LEVEL_PMAP__
        va_l1 = VM_MAX_KERNEL_ADDRESS & CPUWINDOWS_BASE_MASK;
        va_l1_end = VM_MAX_KERNEL_ADDRESS;

        cpu_l1_tte = cpu_tte + ((va_l1 & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT);

        while (va_l1 < va_l1_end) {

                va_l2 = va_l1;

                if (((va_l1 & ~ARM_TT_L1_OFFMASK)+ARM_TT_L1_SIZE) < va_l1) {
                        /* If this is the last L1 entry, it must cover the last mapping. */
                        va_l2_end = va_l1_end;
                } else {
                        va_l2_end = MIN((va_l1 & ~ARM_TT_L1_OFFMASK)+ARM_TT_L1_SIZE, va_l1_end);
                }

                cpu_l2_tte = ((tt_entry_t *) phystokv(((*cpu_l1_tte) & ARM_TTE_TABLE_MASK))) + ((va_l2 & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
#else
                va_l2 = VM_MAX_KERNEL_ADDRESS & CPUWINDOWS_BASE_MASK;
                va_l2_end = VM_MAX_KERNEL_ADDRESS;
                cpu_l2_tte = cpu_tte + ((va_l2 & ARM_TT_L2_INDEX_MASK) >> ARM_TT_L2_SHIFT);
#endif

                while (va_l2 < va_l2_end) {
                        pt_entry_t *    ptp;
                        pmap_paddr_t    ptp_phys;

                        /* Allocate a page and setup L3 Table TTE in L2 */
                        ptp = (pt_entry_t *) alloc_ptpage(FALSE);
                        ptp_phys = (pmap_paddr_t)kvtophys((vm_offset_t)ptp);

                        pmap_init_pte_page(kernel_pmap, ptp, va_l2, 3, TRUE);

                        *cpu_l2_tte = (pa_to_tte (ptp_phys)) | ARM_TTE_TYPE_TABLE | ARM_TTE_VALID | ARM_TTE_TABLE_PXN | ARM_TTE_TABLE_XN;

                        va_l2 += ARM_TT_L2_SIZE;
                        cpu_l2_tte++;
                };
#if !__ARM64_TWO_LEVEL_PMAP__
                va_l1 = va_l2_end;
                cpu_l1_tte++;
        }
#endif

#if __ARM64_PMAP_SUBPAGE_L1__ && __ARM_16K_PG__
        /*
         * In this configuration, the bootstrap mappings (arm_vm_init) and
         * the heap mappings occupy separate L1 regions.  Explicitly set up
         * the heap L1 allocations here.
         */
        va_l1 = VM_MIN_KERNEL_ADDRESS & ~ARM_TT_L1_OFFMASK;
        cpu_l1_tte = cpu_tte + ((va_l1 & ARM_TT_L1_INDEX_MASK) >> ARM_TT_L1_SHIFT);

        while ((va_l1 >= (VM_MIN_KERNEL_ADDRESS & ~ARM_TT_L1_OFFMASK)) && (va_l1 < VM_MAX_KERNEL_ADDRESS)) {
                /*
                 * If the L1 entry has not yet been allocated, allocate it
                 * now and treat it as a heap table.
                 */
                if (*cpu_l1_tte == ARM_TTE_EMPTY) {
                        tt_entry_t *new_tte = (tt_entry_t*)alloc_ptpage(FALSE);
                        bzero(new_tte, ARM_PGBYTES);
                        *cpu_l1_tte = (kvtophys((vm_offset_t)new_tte) & ARM_TTE_TABLE_MASK)  | ARM_TTE_TYPE_TABLE | ARM_TTE_VALID | ARM_TTE_TABLE_PXN | ARM_TTE_TABLE_XN;
                }

                cpu_l1_tte++;
                va_l1 += ARM_TT_L1_SIZE;
        }
#endif

        /*
         * Adjust avail_start so that the range that the VM owns
         * starts on a PAGE_SIZE aligned boundary.
         */
        avail_start = (avail_start + PAGE_MASK) & ~PAGE_MASK;


        first_avail = avail_start;
        patch_low_glo_static_region(args->topOfKernelData, avail_start - args->topOfKernelData);
}