arm64: move kernel image to base of vmalloc area

[deliverable/linux.git] / arch / arm64 / mm / mmu.c

/*
 * Based on arch/arm/mm/mmu.c
 *
 * Copyright (C) 1995-2005 Russell King
 * Copyright (C) 2012 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/libfdt.h>
#include <linux/mman.h>
#include <linux/nodemask.h>
#include <linux/memblock.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/stop_machine.h>

#include <asm/barrier.h>
#include <asm/cputype.h>
#include <asm/fixmap.h>
#include <asm/kasan.h>
#include <asm/kernel-pgtable.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/sizes.h>
#include <asm/tlb.h>
#include <asm/memblock.h>
#include <asm/mmu_context.h>

#include "mm.h"

u64 idmap_t0sz = TCR_T0SZ(VA_BITS);

/*
 * Empty_zero_page is a special page that is used for zero-initialized data
 * and COW.
 */
unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);

static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;

pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
                              unsigned long size, pgprot_t vma_prot)
{
        if (!pfn_valid(pfn))
                return pgprot_noncached(vma_prot);
        else if (file->f_flags & O_SYNC)
                return pgprot_writecombine(vma_prot);
        return vma_prot;
}
EXPORT_SYMBOL(phys_mem_access_prot);

static phys_addr_t __init early_pgtable_alloc(void)
{
        phys_addr_t phys;
        void *ptr;

        phys = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
        BUG_ON(!phys);

        /*
         * The FIX_{PGD,PUD,PMD} slots may be in active use, but the FIX_PTE
         * slot will be free, so we can (ab)use the FIX_PTE slot to initialise
         * any level of table.
         */
        ptr = pte_set_fixmap(phys);

        memset(ptr, 0, PAGE_SIZE);

        /*
         * Implicit barriers also ensure the zeroed page is visible to the page
         * table walker
         */
        pte_clear_fixmap();

        return phys;
}

/*
 * remap a PMD into pages
 */
static void split_pmd(pmd_t *pmd, pte_t *pte)
{
        unsigned long pfn = pmd_pfn(*pmd);
        int i = 0;

        do {
                /*
                 * Need to have the least restrictive permissions available
                 * permissions will be fixed up later
                 */
                set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
                pfn++;
        } while (pte++, i++, i < PTRS_PER_PTE);
}

static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
                                  unsigned long end, unsigned long pfn,
                                  pgprot_t prot,
                                  phys_addr_t (*pgtable_alloc)(void))
{
        pte_t *pte;

        if (pmd_none(*pmd) || pmd_sect(*pmd)) {
                phys_addr_t pte_phys;
                BUG_ON(!pgtable_alloc);
                pte_phys = pgtable_alloc();
                pte = pte_set_fixmap(pte_phys);
                if (pmd_sect(*pmd))
                        split_pmd(pmd, pte);
                __pmd_populate(pmd, pte_phys, PMD_TYPE_TABLE);
                flush_tlb_all();
                pte_clear_fixmap();
        }
        BUG_ON(pmd_bad(*pmd));

        pte = pte_set_fixmap_offset(pmd, addr);
        do {
                set_pte(pte, pfn_pte(pfn, prot));
                pfn++;
        } while (pte++, addr += PAGE_SIZE, addr != end);

        pte_clear_fixmap();
}

static void split_pud(pud_t *old_pud, pmd_t *pmd)
{
        unsigned long addr = pud_pfn(*old_pud) << PAGE_SHIFT;
        pgprot_t prot = __pgprot(pud_val(*old_pud) ^ addr);
        int i = 0;

        do {
                set_pmd(pmd, __pmd(addr | pgprot_val(prot)));
                addr += PMD_SIZE;
        } while (pmd++, i++, i < PTRS_PER_PMD);
}

#ifdef CONFIG_DEBUG_PAGEALLOC
static bool block_mappings_allowed(phys_addr_t (*pgtable_alloc)(void))
{

        /*
         * If debug_page_alloc is enabled we must map the linear map
         * using pages. However, other mappings created by
         * create_mapping_noalloc must use sections in some cases. Allow
         * sections to be used in those cases, where no pgtable_alloc
         * function is provided.
         */
        return !pgtable_alloc || !debug_pagealloc_enabled();
}
#else
static bool block_mappings_allowed(phys_addr_t (*pgtable_alloc)(void))
{
        return true;
}
#endif

static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
                                  phys_addr_t phys, pgprot_t prot,
                                  phys_addr_t (*pgtable_alloc)(void))
{
        pmd_t *pmd;
        unsigned long next;

        /*
         * Check for initial section mappings in the pgd/pud and remove them.
         */
        if (pud_none(*pud) || pud_sect(*pud)) {
                phys_addr_t pmd_phys;
                BUG_ON(!pgtable_alloc);
                pmd_phys = pgtable_alloc();
                pmd = pmd_set_fixmap(pmd_phys);
                if (pud_sect(*pud)) {
                        /*
                         * need to have the 1G of mappings continue to be
                         * present
                         */
                        split_pud(pud, pmd);
                }
                __pud_populate(pud, pmd_phys, PUD_TYPE_TABLE);
                flush_tlb_all();
                pmd_clear_fixmap();
        }
        BUG_ON(pud_bad(*pud));

        pmd = pmd_set_fixmap_offset(pud, addr);
        do {
                next = pmd_addr_end(addr, end);
                /* try section mapping first */
                if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
                      block_mappings_allowed(pgtable_alloc)) {
                        pmd_t old_pmd =*pmd;
                        set_pmd(pmd, __pmd(phys |
                                           pgprot_val(mk_sect_prot(prot))));
                        /*
                         * Check for previous table entries created during
                         * boot (__create_page_tables) and flush them.
                         */
                        if (!pmd_none(old_pmd)) {
                                flush_tlb_all();
                                if (pmd_table(old_pmd)) {
                                        phys_addr_t table = pmd_page_paddr(old_pmd);
                                        if (!WARN_ON_ONCE(slab_is_available()))
                                                memblock_free(table, PAGE_SIZE);
                                }
                        }
                } else {
                        alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
                                       prot, pgtable_alloc);
                }
                phys += next - addr;
        } while (pmd++, addr = next, addr != end);

        pmd_clear_fixmap();
}

static inline bool use_1G_block(unsigned long addr, unsigned long next,
                        unsigned long phys)
{
        if (PAGE_SHIFT != 12)
                return false;

        if (((addr | next | phys) & ~PUD_MASK) != 0)
                return false;

        return true;
}

static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
                                  phys_addr_t phys, pgprot_t prot,
                                  phys_addr_t (*pgtable_alloc)(void))
{
        pud_t *pud;
        unsigned long next;

        if (pgd_none(*pgd)) {
                phys_addr_t pud_phys;
                BUG_ON(!pgtable_alloc);
                pud_phys = pgtable_alloc();
                __pgd_populate(pgd, pud_phys, PUD_TYPE_TABLE);
        }
        BUG_ON(pgd_bad(*pgd));

        pud = pud_set_fixmap_offset(pgd, addr);
        do {
                next = pud_addr_end(addr, end);

                /*
                 * For 4K granule only, attempt to put down a 1GB block
                 */
                if (use_1G_block(addr, next, phys) &&
                    block_mappings_allowed(pgtable_alloc)) {
                        pud_t old_pud = *pud;
                        set_pud(pud, __pud(phys |
                                           pgprot_val(mk_sect_prot(prot))));

                        /*
                         * If we have an old value for a pud, it will
                         * be pointing to a pmd table that we no longer
                         * need (from swapper_pg_dir).
                         *
                         * Look up the old pmd table and free it.
                         */
                        if (!pud_none(old_pud)) {
                                flush_tlb_all();
                                if (pud_table(old_pud)) {
                                        phys_addr_t table = pud_page_paddr(old_pud);
                                        if (!WARN_ON_ONCE(slab_is_available()))
                                                memblock_free(table, PAGE_SIZE);
                                }
                        }
                } else {
                        alloc_init_pmd(pud, addr, next, phys, prot,
                                       pgtable_alloc);
                }
                phys += next - addr;
        } while (pud++, addr = next, addr != end);

        pud_clear_fixmap();
}

/*
 * Create the page directory entries and any necessary page tables for the
 * mapping specified by 'md'.
 */
static void init_pgd(pgd_t *pgd, phys_addr_t phys, unsigned long virt,
                                    phys_addr_t size, pgprot_t prot,
                                    phys_addr_t (*pgtable_alloc)(void))
{
        unsigned long addr, length, end, next;

        /*
         * If the virtual and physical address don't have the same offset
         * within a page, we cannot map the region as the caller expects.
         */
        if (WARN_ON((phys ^ virt) & ~PAGE_MASK))
                return;

        phys &= PAGE_MASK;
        addr = virt & PAGE_MASK;
        length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));

        end = addr + length;
        do {
                next = pgd_addr_end(addr, end);
                alloc_init_pud(pgd, addr, next, phys, prot, pgtable_alloc);
                phys += next - addr;
        } while (pgd++, addr = next, addr != end);
}

static phys_addr_t late_pgtable_alloc(void)
{
        void *ptr = (void *)__get_free_page(PGALLOC_GFP);
        BUG_ON(!ptr);

        /* Ensure the zeroed page is visible to the page table walker */
        dsb(ishst);
        return __pa(ptr);
}

static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
                                 unsigned long virt, phys_addr_t size,
                                 pgprot_t prot,
                                 phys_addr_t (*alloc)(void))
{
        init_pgd(pgd_offset_raw(pgdir, virt), phys, virt, size, prot, alloc);
}

/*
 * This function can only be used to modify existing table entries,
 * without allocating new levels of table. Note that this permits the
 * creation of new section or page entries.
 */
static void __init create_mapping_noalloc(phys_addr_t phys, unsigned long virt,
                                  phys_addr_t size, pgprot_t prot)
{
        if (virt < VMALLOC_START) {
                pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
                        &phys, virt);
                return;
        }
        __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
                             NULL);
}

void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
                               unsigned long virt, phys_addr_t size,
                               pgprot_t prot)
{
        __create_pgd_mapping(mm->pgd, phys, virt, size, prot,
                             late_pgtable_alloc);
}

static void create_mapping_late(phys_addr_t phys, unsigned long virt,
                                  phys_addr_t size, pgprot_t prot)
{
        if (virt < VMALLOC_START) {
                pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
                        &phys, virt);
                return;
        }

        __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
                             late_pgtable_alloc);
}

static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end)
{
        unsigned long kernel_start = __pa(_stext);
        unsigned long kernel_end = __pa(_etext);

        /*
         * Take care not to create a writable alias for the
         * read-only text and rodata sections of the kernel image.
         */

        /* No overlap with the kernel text */
        if (end < kernel_start || start >= kernel_end) {
                __create_pgd_mapping(pgd, start, __phys_to_virt(start),
                                     end - start, PAGE_KERNEL,
                                     early_pgtable_alloc);
                return;
        }

        /*
         * This block overlaps the kernel text mapping.
         * Map the portion(s) which don't overlap.
         */
        if (start < kernel_start)
                __create_pgd_mapping(pgd, start,
                                     __phys_to_virt(start),
                                     kernel_start - start, PAGE_KERNEL,
                                     early_pgtable_alloc);
        if (kernel_end < end)
                __create_pgd_mapping(pgd, kernel_end,
                                     __phys_to_virt(kernel_end),
                                     end - kernel_end, PAGE_KERNEL,
                                     early_pgtable_alloc);

        /*
         * Map the linear alias of the [_stext, _etext) interval as
         * read-only/non-executable. This makes the contents of the
         * region accessible to subsystems such as hibernate, but
         * protects it from inadvertent modification or execution.
         */
        __create_pgd_mapping(pgd, kernel_start, __phys_to_virt(kernel_start),
                             kernel_end - kernel_start, PAGE_KERNEL_RO,
                             early_pgtable_alloc);
}

static void __init map_mem(pgd_t *pgd)
{
        struct memblock_region *reg;

        /* map all the memory banks */
        for_each_memblock(memory, reg) {
                phys_addr_t start = reg->base;
                phys_addr_t end = start + reg->size;

                if (start >= end)
                        break;
                if (memblock_is_nomap(reg))
                        continue;

                __map_memblock(pgd, start, end);
        }
}

void mark_rodata_ro(void)
{
        if (!IS_ENABLED(CONFIG_DEBUG_RODATA))
                return;

        create_mapping_late(__pa(_stext), (unsigned long)_stext,
                                (unsigned long)_etext - (unsigned long)_stext,
                                PAGE_KERNEL_ROX);
}

void fixup_init(void)
{
        /*
         * Unmap the __init region but leave the VM area in place. This
         * prevents the region from being reused for kernel modules, which
         * is not supported by kallsyms.
         */
        unmap_kernel_range((u64)__init_begin, (u64)(__init_end - __init_begin));
}

static void __init map_kernel_chunk(pgd_t *pgd, void *va_start, void *va_end,
                                    pgprot_t prot, struct vm_struct *vma)
{
        phys_addr_t pa_start = __pa(va_start);
        unsigned long size = va_end - va_start;

        BUG_ON(!PAGE_ALIGNED(pa_start));
        BUG_ON(!PAGE_ALIGNED(size));

        __create_pgd_mapping(pgd, pa_start, (unsigned long)va_start, size, prot,
                             early_pgtable_alloc);

        vma->addr       = va_start;
        vma->phys_addr  = pa_start;
        vma->size       = size;
        vma->flags      = VM_MAP;
        vma->caller     = __builtin_return_address(0);

        vm_area_add_early(vma);
}

/*
 * Create fine-grained mappings for the kernel.
 */
static void __init map_kernel(pgd_t *pgd)
{
        static struct vm_struct vmlinux_text, vmlinux_init, vmlinux_data;

        map_kernel_chunk(pgd, _stext, _etext, PAGE_KERNEL_EXEC, &vmlinux_text);
        map_kernel_chunk(pgd, __init_begin, __init_end, PAGE_KERNEL_EXEC,
                         &vmlinux_init);
        map_kernel_chunk(pgd, _data, _end, PAGE_KERNEL, &vmlinux_data);

        if (!pgd_val(*pgd_offset_raw(pgd, FIXADDR_START))) {
                /*
                 * The fixmap falls in a separate pgd to the kernel, and doesn't
                 * live in the carveout for the swapper_pg_dir. We can simply
                 * re-use the existing dir for the fixmap.
                 */
                set_pgd(pgd_offset_raw(pgd, FIXADDR_START),
                        *pgd_offset_k(FIXADDR_START));
        } else if (CONFIG_PGTABLE_LEVELS > 3) {
                /*
                 * The fixmap shares its top level pgd entry with the kernel
                 * mapping. This can really only occur when we are running
                 * with 16k/4 levels, so we can simply reuse the pud level
                 * entry instead.
                 */
                BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
                set_pud(pud_set_fixmap_offset(pgd, FIXADDR_START),
                        __pud(__pa(bm_pmd) | PUD_TYPE_TABLE));
                pud_clear_fixmap();
        } else {
                BUG();
        }

        kasan_copy_shadow(pgd);
}

/*
 * paging_init() sets up the page tables, initialises the zone memory
 * maps and sets up the zero page.
 */
void __init paging_init(void)
{
        phys_addr_t pgd_phys = early_pgtable_alloc();
        pgd_t *pgd = pgd_set_fixmap(pgd_phys);

        map_kernel(pgd);
        map_mem(pgd);

        /*
         * We want to reuse the original swapper_pg_dir so we don't have to
         * communicate the new address to non-coherent secondaries in
         * secondary_entry, and so cpu_switch_mm can generate the address with
         * adrp+add rather than a load from some global variable.
         *
         * To do this we need to go via a temporary pgd.
         */
        cpu_replace_ttbr1(__va(pgd_phys));
        memcpy(swapper_pg_dir, pgd, PAGE_SIZE);
        cpu_replace_ttbr1(swapper_pg_dir);

        pgd_clear_fixmap();
        memblock_free(pgd_phys, PAGE_SIZE);

        /*
         * We only reuse the PGD from the swapper_pg_dir, not the pud + pmd
         * allocated with it.
         */
        memblock_free(__pa(swapper_pg_dir) + PAGE_SIZE,
                      SWAPPER_DIR_SIZE - PAGE_SIZE);

        bootmem_init();
}

/*
 * Check whether a kernel address is valid (derived from arch/x86/).
 */
int kern_addr_valid(unsigned long addr)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

        if ((((long)addr) >> VA_BITS) != -1UL)
                return 0;

        pgd = pgd_offset_k(addr);
        if (pgd_none(*pgd))
                return 0;

        pud = pud_offset(pgd, addr);
        if (pud_none(*pud))
                return 0;

        if (pud_sect(*pud))
                return pfn_valid(pud_pfn(*pud));

        pmd = pmd_offset(pud, addr);
        if (pmd_none(*pmd))
                return 0;

        if (pmd_sect(*pmd))
                return pfn_valid(pmd_pfn(*pmd));

        pte = pte_offset_kernel(pmd, addr);
        if (pte_none(*pte))
                return 0;

        return pfn_valid(pte_pfn(*pte));
}
#ifdef CONFIG_SPARSEMEM_VMEMMAP
#if !ARM64_SWAPPER_USES_SECTION_MAPS
int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
{
        return vmemmap_populate_basepages(start, end, node);
}
#else   /* !ARM64_SWAPPER_USES_SECTION_MAPS */
int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
{
        unsigned long addr = start;
        unsigned long next;
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;

        do {
                next = pmd_addr_end(addr, end);

                pgd = vmemmap_pgd_populate(addr, node);
                if (!pgd)
                        return -ENOMEM;

                pud = vmemmap_pud_populate(pgd, addr, node);
                if (!pud)
                        return -ENOMEM;

                pmd = pmd_offset(pud, addr);
                if (pmd_none(*pmd)) {
                        void *p = NULL;

                        p = vmemmap_alloc_block_buf(PMD_SIZE, node);
                        if (!p)
                                return -ENOMEM;

                        set_pmd(pmd, __pmd(__pa(p) | PROT_SECT_NORMAL));
                } else
                        vmemmap_verify((pte_t *)pmd, node, addr, next);
        } while (addr = next, addr != end);

        return 0;
}
#endif  /* CONFIG_ARM64_64K_PAGES */
void vmemmap_free(unsigned long start, unsigned long end)
{
}
#endif  /* CONFIG_SPARSEMEM_VMEMMAP */

static inline pud_t * fixmap_pud(unsigned long addr)
{
        pgd_t *pgd = pgd_offset_k(addr);

        BUG_ON(pgd_none(*pgd) || pgd_bad(*pgd));

        return pud_offset_kimg(pgd, addr);
}

static inline pmd_t * fixmap_pmd(unsigned long addr)
{
        pud_t *pud = fixmap_pud(addr);

        BUG_ON(pud_none(*pud) || pud_bad(*pud));

        return pmd_offset_kimg(pud, addr);
}

static inline pte_t * fixmap_pte(unsigned long addr)
{
        return &bm_pte[pte_index(addr)];
}

void __init early_fixmap_init(void)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        unsigned long addr = FIXADDR_START;

        pgd = pgd_offset_k(addr);
        if (CONFIG_PGTABLE_LEVELS > 3 && !pgd_none(*pgd)) {
                /*
                 * We only end up here if the kernel mapping and the fixmap
                 * share the top level pgd entry, which should only happen on
                 * 16k/4 levels configurations.
                 */
                BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
                pud = pud_offset_kimg(pgd, addr);
        } else {
                pgd_populate(&init_mm, pgd, bm_pud);
                pud = fixmap_pud(addr);
        }
        pud_populate(&init_mm, pud, bm_pmd);
        pmd = fixmap_pmd(addr);
        pmd_populate_kernel(&init_mm, pmd, bm_pte);

        /*
         * The boot-ioremap range spans multiple pmds, for which
         * we are not prepared:
         */
        BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
                     != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));

        if ((pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)))
             || pmd != fixmap_pmd(fix_to_virt(FIX_BTMAP_END))) {
                WARN_ON(1);
                pr_warn("pmd %p != %p, %p\n",
                        pmd, fixmap_pmd(fix_to_virt(FIX_BTMAP_BEGIN)),
                        fixmap_pmd(fix_to_virt(FIX_BTMAP_END)));
                pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
                        fix_to_virt(FIX_BTMAP_BEGIN));
                pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
                        fix_to_virt(FIX_BTMAP_END));

                pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
                pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
        }
}

void __set_fixmap(enum fixed_addresses idx,
                               phys_addr_t phys, pgprot_t flags)
{
        unsigned long addr = __fix_to_virt(idx);
        pte_t *pte;

        BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);

        pte = fixmap_pte(addr);

        if (pgprot_val(flags)) {
                set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags));
        } else {
                pte_clear(&init_mm, addr, pte);
                flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
        }
}

void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
{
        const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
        pgprot_t prot = PAGE_KERNEL_RO;
        int size, offset;
        void *dt_virt;

        /*
         * Check whether the physical FDT address is set and meets the minimum
         * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
         * at least 8 bytes so that we can always access the size field of the
         * FDT header after mapping the first chunk, double check here if that
         * is indeed the case.
         */
        BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
        if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
                return NULL;

        /*
         * Make sure that the FDT region can be mapped without the need to
         * allocate additional translation table pages, so that it is safe
         * to call create_mapping_noalloc() this early.
         *
         * On 64k pages, the FDT will be mapped using PTEs, so we need to
         * be in the same PMD as the rest of the fixmap.
         * On 4k pages, we'll use section mappings for the FDT so we only
         * have to be in the same PUD.
         */
        BUILD_BUG_ON(dt_virt_base % SZ_2M);

        BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
                     __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);

        offset = dt_phys % SWAPPER_BLOCK_SIZE;
        dt_virt = (void *)dt_virt_base + offset;

        /* map the first chunk so we can read the size from the header */
        create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE),
                        dt_virt_base, SWAPPER_BLOCK_SIZE, prot);

        if (fdt_check_header(dt_virt) != 0)
                return NULL;

        size = fdt_totalsize(dt_virt);
        if (size > MAX_FDT_SIZE)
                return NULL;

        if (offset + size > SWAPPER_BLOCK_SIZE)
                create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
                               round_up(offset + size, SWAPPER_BLOCK_SIZE), prot);

        memblock_reserve(dt_phys, size);

        return dt_virt;
}

int __init arch_ioremap_pud_supported(void)
{
        /* only 4k granule supports level 1 block mappings */
        return IS_ENABLED(CONFIG_ARM64_4K_PAGES);
}

int __init arch_ioremap_pmd_supported(void)
{
        return 1;
}

int pud_set_huge(pud_t *pud, phys_addr_t phys, pgprot_t prot)
{
        BUG_ON(phys & ~PUD_MASK);
        set_pud(pud, __pud(phys | PUD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));
        return 1;
}

int pmd_set_huge(pmd_t *pmd, phys_addr_t phys, pgprot_t prot)
{
        BUG_ON(phys & ~PMD_MASK);
        set_pmd(pmd, __pmd(phys | PMD_TYPE_SECT | pgprot_val(mk_sect_prot(prot))));
        return 1;
}

int pud_clear_huge(pud_t *pud)
{
        if (!pud_sect(*pud))
                return 0;
        pud_clear(pud);
        return 1;
}

int pmd_clear_huge(pmd_t *pmd)
{
        if (!pmd_sect(*pmd))
                return 0;
        pmd_clear(pmd);
        return 1;
}