Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[GitHub/LineageOS/android_kernel_motorola_exynos9610.git] / arch / x86 / mm / init_32.c

/*
 *
 *  Copyright (C) 1995  Linus Torvalds
 *
 *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
 */

#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/swap.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/pci.h>
#include <linux/pfn.h>
#include <linux/poison.h>
#include <linux/bootmem.h>
#include <linux/memblock.h>
#include <linux/proc_fs.h>
#include <linux/memory_hotplug.h>
#include <linux/initrd.h>
#include <linux/cpumask.h>
#include <linux/gfp.h>

#include <asm/asm.h>
#include <asm/bios_ebda.h>
#include <asm/processor.h>
#include <linux/uaccess.h>
#include <asm/pgtable.h>
#include <asm/dma.h>
#include <asm/fixmap.h>
#include <asm/e820.h>
#include <asm/apic.h>
#include <asm/bugs.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/olpc_ofw.h>
#include <asm/pgalloc.h>
#include <asm/sections.h>
#include <asm/paravirt.h>
#include <asm/setup.h>
#include <asm/cacheflush.h>
#include <asm/page_types.h>
#include <asm/init.h>

#include "mm_internal.h"

unsigned long highstart_pfn, highend_pfn;

static noinline int do_test_wp_bit(void);

bool __read_mostly __vmalloc_start_set = false;

/*
 * Creates a middle page table and puts a pointer to it in the
 * given global directory entry. This only returns the gd entry
 * in non-PAE compilation mode, since the middle layer is folded.
 */
static pmd_t * __init one_md_table_init(pgd_t *pgd)
{
        pud_t *pud;
        pmd_t *pmd_table;

#ifdef CONFIG_X86_PAE
        if (!(pgd_val(*pgd) & _PAGE_PRESENT)) {
                pmd_table = (pmd_t *)alloc_low_page();
                paravirt_alloc_pmd(&init_mm, __pa(pmd_table) >> PAGE_SHIFT);
                set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
                pud = pud_offset(pgd, 0);
                BUG_ON(pmd_table != pmd_offset(pud, 0));

                return pmd_table;
        }
#endif
        pud = pud_offset(pgd, 0);
        pmd_table = pmd_offset(pud, 0);

        return pmd_table;
}

/*
 * Create a page table and place a pointer to it in a middle page
 * directory entry:
 */
static pte_t * __init one_page_table_init(pmd_t *pmd)
{
        if (!(pmd_val(*pmd) & _PAGE_PRESENT)) {
                pte_t *page_table = (pte_t *)alloc_low_page();

                paravirt_alloc_pte(&init_mm, __pa(page_table) >> PAGE_SHIFT);
                set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));
                BUG_ON(page_table != pte_offset_kernel(pmd, 0));
        }

        return pte_offset_kernel(pmd, 0);
}

pmd_t * __init populate_extra_pmd(unsigned long vaddr)
{
        int pgd_idx = pgd_index(vaddr);
        int pmd_idx = pmd_index(vaddr);

        return one_md_table_init(swapper_pg_dir + pgd_idx) + pmd_idx;
}

pte_t * __init populate_extra_pte(unsigned long vaddr)
{
        int pte_idx = pte_index(vaddr);
        pmd_t *pmd;

        pmd = populate_extra_pmd(vaddr);
        return one_page_table_init(pmd) + pte_idx;
}

static unsigned long __init
page_table_range_init_count(unsigned long start, unsigned long end)
{
        unsigned long count = 0;
#ifdef CONFIG_HIGHMEM
        int pmd_idx_kmap_begin = fix_to_virt(FIX_KMAP_END) >> PMD_SHIFT;
        int pmd_idx_kmap_end = fix_to_virt(FIX_KMAP_BEGIN) >> PMD_SHIFT;
        int pgd_idx, pmd_idx;
        unsigned long vaddr;

        if (pmd_idx_kmap_begin == pmd_idx_kmap_end)
                return 0;

        vaddr = start;
        pgd_idx = pgd_index(vaddr);
        pmd_idx = pmd_index(vaddr);

        for ( ; (pgd_idx < PTRS_PER_PGD) && (vaddr != end); pgd_idx++) {
                for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end);
                                                        pmd_idx++) {
                        if ((vaddr >> PMD_SHIFT) >= pmd_idx_kmap_begin &&
                            (vaddr >> PMD_SHIFT) <= pmd_idx_kmap_end)
                                count++;
                        vaddr += PMD_SIZE;
                }
                pmd_idx = 0;
        }
#endif
        return count;
}

static pte_t *__init page_table_kmap_check(pte_t *pte, pmd_t *pmd,
                                           unsigned long vaddr, pte_t *lastpte,
                                           void **adr)
{
#ifdef CONFIG_HIGHMEM
        /*
         * Something (early fixmap) may already have put a pte
         * page here, which causes the page table allocation
         * to become nonlinear. Attempt to fix it, and if it
         * is still nonlinear then we have to bug.
         */
        int pmd_idx_kmap_begin = fix_to_virt(FIX_KMAP_END) >> PMD_SHIFT;
        int pmd_idx_kmap_end = fix_to_virt(FIX_KMAP_BEGIN) >> PMD_SHIFT;

        if (pmd_idx_kmap_begin != pmd_idx_kmap_end
            && (vaddr >> PMD_SHIFT) >= pmd_idx_kmap_begin
            && (vaddr >> PMD_SHIFT) <= pmd_idx_kmap_end) {
                pte_t *newpte;
                int i;

                BUG_ON(after_bootmem);
                newpte = *adr;
                for (i = 0; i < PTRS_PER_PTE; i++)
                        set_pte(newpte + i, pte[i]);
                *adr = (void *)(((unsigned long)(*adr)) + PAGE_SIZE);

                paravirt_alloc_pte(&init_mm, __pa(newpte) >> PAGE_SHIFT);
                set_pmd(pmd, __pmd(__pa(newpte)|_PAGE_TABLE));
                BUG_ON(newpte != pte_offset_kernel(pmd, 0));
                __flush_tlb_all();

                paravirt_release_pte(__pa(pte) >> PAGE_SHIFT);
                pte = newpte;
        }
        BUG_ON(vaddr < fix_to_virt(FIX_KMAP_BEGIN - 1)
               && vaddr > fix_to_virt(FIX_KMAP_END)
               && lastpte && lastpte + PTRS_PER_PTE != pte);
#endif
        return pte;
}

/*
 * This function initializes a certain range of kernel virtual memory
 * with new bootmem page tables, everywhere page tables are missing in
 * the given range.
 *
 * NOTE: The pagetables are allocated contiguous on the physical space
 * so we can cache the place of the first one and move around without
 * checking the pgd every time.
 */
static void __init
page_table_range_init(unsigned long start, unsigned long end, pgd_t *pgd_base)
{
        int pgd_idx, pmd_idx;
        unsigned long vaddr;
        pgd_t *pgd;
        pmd_t *pmd;
        pte_t *pte = NULL;
        unsigned long count = page_table_range_init_count(start, end);
        void *adr = NULL;

        if (count)
                adr = alloc_low_pages(count);

        vaddr = start;
        pgd_idx = pgd_index(vaddr);
        pmd_idx = pmd_index(vaddr);
        pgd = pgd_base + pgd_idx;

        for ( ; (pgd_idx < PTRS_PER_PGD) && (vaddr != end); pgd++, pgd_idx++) {
                pmd = one_md_table_init(pgd);
                pmd = pmd + pmd_index(vaddr);
                for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end);
                                                        pmd++, pmd_idx++) {
                        pte = page_table_kmap_check(one_page_table_init(pmd),
                                                    pmd, vaddr, pte, &adr);

                        vaddr += PMD_SIZE;
                }
                pmd_idx = 0;
        }
}

static inline int is_kernel_text(unsigned long addr)
{
        if (addr >= (unsigned long)_text && addr <= (unsigned long)__init_end)
                return 1;
        return 0;
}

/*
 * This maps the physical memory to kernel virtual address space, a total
 * of max_low_pfn pages, by creating page tables starting from address
 * PAGE_OFFSET:
 */
unsigned long __init
kernel_physical_mapping_init(unsigned long start,
                             unsigned long end,
                             unsigned long page_size_mask)
{
        int use_pse = page_size_mask == (1<<PG_LEVEL_2M);
        unsigned long last_map_addr = end;
        unsigned long start_pfn, end_pfn;
        pgd_t *pgd_base = swapper_pg_dir;
        int pgd_idx, pmd_idx, pte_ofs;
        unsigned long pfn;
        pgd_t *pgd;
        pmd_t *pmd;
        pte_t *pte;
        unsigned pages_2m, pages_4k;
        int mapping_iter;

        start_pfn = start >> PAGE_SHIFT;
        end_pfn = end >> PAGE_SHIFT;

        /*
         * First iteration will setup identity mapping using large/small pages
         * based on use_pse, with other attributes same as set by
         * the early code in head_32.S
         *
         * Second iteration will setup the appropriate attributes (NX, GLOBAL..)
         * as desired for the kernel identity mapping.
         *
         * This two pass mechanism conforms to the TLB app note which says:
         *
         *     "Software should not write to a paging-structure entry in a way
         *      that would change, for any linear address, both the page size
         *      and either the page frame or attributes."
         */
        mapping_iter = 1;

        if (!boot_cpu_has(X86_FEATURE_PSE))
                use_pse = 0;

repeat:
        pages_2m = pages_4k = 0;
        pfn = start_pfn;
        pgd_idx = pgd_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
        pgd = pgd_base + pgd_idx;
        for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
                pmd = one_md_table_init(pgd);

                if (pfn >= end_pfn)
                        continue;
#ifdef CONFIG_X86_PAE
                pmd_idx = pmd_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
                pmd += pmd_idx;
#else
                pmd_idx = 0;
#endif
                for (; pmd_idx < PTRS_PER_PMD && pfn < end_pfn;
                     pmd++, pmd_idx++) {
                        unsigned int addr = pfn * PAGE_SIZE + PAGE_OFFSET;

                        /*
                         * Map with big pages if possible, otherwise
                         * create normal page tables:
                         */
                        if (use_pse) {
                                unsigned int addr2;
                                pgprot_t prot = PAGE_KERNEL_LARGE;
                                /*
                                 * first pass will use the same initial
                                 * identity mapping attribute + _PAGE_PSE.
                                 */
                                pgprot_t init_prot =
                                        __pgprot(PTE_IDENT_ATTR |
                                                 _PAGE_PSE);

                                pfn &= PMD_MASK >> PAGE_SHIFT;
                                addr2 = (pfn + PTRS_PER_PTE-1) * PAGE_SIZE +
                                        PAGE_OFFSET + PAGE_SIZE-1;

                                if (is_kernel_text(addr) ||
                                    is_kernel_text(addr2))
                                        prot = PAGE_KERNEL_LARGE_EXEC;

                                pages_2m++;
                                if (mapping_iter == 1)
                                        set_pmd(pmd, pfn_pmd(pfn, init_prot));
                                else
                                        set_pmd(pmd, pfn_pmd(pfn, prot));

                                pfn += PTRS_PER_PTE;
                                continue;
                        }
                        pte = one_page_table_init(pmd);

                        pte_ofs = pte_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
                        pte += pte_ofs;
                        for (; pte_ofs < PTRS_PER_PTE && pfn < end_pfn;
                             pte++, pfn++, pte_ofs++, addr += PAGE_SIZE) {
                                pgprot_t prot = PAGE_KERNEL;
                                /*
                                 * first pass will use the same initial
                                 * identity mapping attribute.
                                 */
                                pgprot_t init_prot = __pgprot(PTE_IDENT_ATTR);

                                if (is_kernel_text(addr))
                                        prot = PAGE_KERNEL_EXEC;

                                pages_4k++;
                                if (mapping_iter == 1) {
                                        set_pte(pte, pfn_pte(pfn, init_prot));
                                        last_map_addr = (pfn << PAGE_SHIFT) + PAGE_SIZE;
                                } else
                                        set_pte(pte, pfn_pte(pfn, prot));
                        }
                }
        }
        if (mapping_iter == 1) {
                /*
                 * update direct mapping page count only in the first
                 * iteration.
                 */
                update_page_count(PG_LEVEL_2M, pages_2m);
                update_page_count(PG_LEVEL_4K, pages_4k);

                /*
                 * local global flush tlb, which will flush the previous
                 * mappings present in both small and large page TLB's.
                 */
                __flush_tlb_all();

                /*
                 * Second iteration will set the actual desired PTE attributes.
                 */
                mapping_iter = 2;
                goto repeat;
        }
        return last_map_addr;
}

pte_t *kmap_pte;

static inline pte_t *kmap_get_fixmap_pte(unsigned long vaddr)
{
        return pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr),
                        vaddr), vaddr), vaddr);
}

static void __init kmap_init(void)
{
        unsigned long kmap_vstart;

        /*
         * Cache the first kmap pte:
         */
        kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
        kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
}

#ifdef CONFIG_HIGHMEM
static void __init permanent_kmaps_init(pgd_t *pgd_base)
{
        unsigned long vaddr;
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

        vaddr = PKMAP_BASE;
        page_table_range_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, pgd_base);

        pgd = swapper_pg_dir + pgd_index(vaddr);
        pud = pud_offset(pgd, vaddr);
        pmd = pmd_offset(pud, vaddr);
        pte = pte_offset_kernel(pmd, vaddr);
        pkmap_page_table = pte;
}

void __init add_highpages_with_active_regions(int nid,
                         unsigned long start_pfn, unsigned long end_pfn)
{
        phys_addr_t start, end;
        u64 i;

        for_each_free_mem_range(i, nid, MEMBLOCK_NONE, &start, &end, NULL) {
                unsigned long pfn = clamp_t(unsigned long, PFN_UP(start),
                                            start_pfn, end_pfn);
                unsigned long e_pfn = clamp_t(unsigned long, PFN_DOWN(end),
                                              start_pfn, end_pfn);
                for ( ; pfn < e_pfn; pfn++)
                        if (pfn_valid(pfn))
                                free_highmem_page(pfn_to_page(pfn));
        }
}
#else
static inline void permanent_kmaps_init(pgd_t *pgd_base)
{
}
#endif /* CONFIG_HIGHMEM */

void __init native_pagetable_init(void)
{
        unsigned long pfn, va;
        pgd_t *pgd, *base = swapper_pg_dir;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

        /*
         * Remove any mappings which extend past the end of physical
         * memory from the boot time page table.
         * In virtual address space, we should have at least two pages
         * from VMALLOC_END to pkmap or fixmap according to VMALLOC_END
         * definition. And max_low_pfn is set to VMALLOC_END physical
         * address. If initial memory mapping is doing right job, we
         * should have pte used near max_low_pfn or one pmd is not present.
         */
        for (pfn = max_low_pfn; pfn < 1<<(32-PAGE_SHIFT); pfn++) {
                va = PAGE_OFFSET + (pfn<<PAGE_SHIFT);
                pgd = base + pgd_index(va);
                if (!pgd_present(*pgd))
                        break;

                pud = pud_offset(pgd, va);
                pmd = pmd_offset(pud, va);
                if (!pmd_present(*pmd))
                        break;

                /* should not be large page here */
                if (pmd_large(*pmd)) {
                        pr_warn("try to clear pte for ram above max_low_pfn: pfn: %lx pmd: %p pmd phys: %lx, but pmd is big page and is not using pte !\n",
                                pfn, pmd, __pa(pmd));
                        BUG_ON(1);
                }

                pte = pte_offset_kernel(pmd, va);
                if (!pte_present(*pte))
                        break;

                printk(KERN_DEBUG "clearing pte for ram above max_low_pfn: pfn: %lx pmd: %p pmd phys: %lx pte: %p pte phys: %lx\n",
                                pfn, pmd, __pa(pmd), pte, __pa(pte));
                pte_clear(NULL, va, pte);
        }
        paravirt_alloc_pmd(&init_mm, __pa(base) >> PAGE_SHIFT);
        paging_init();
}

/*
 * Build a proper pagetable for the kernel mappings.  Up until this
 * point, we've been running on some set of pagetables constructed by
 * the boot process.
 *
 * If we're booting on native hardware, this will be a pagetable
 * constructed in arch/x86/kernel/head_32.S.  The root of the
 * pagetable will be swapper_pg_dir.
 *
 * If we're booting paravirtualized under a hypervisor, then there are
 * more options: we may already be running PAE, and the pagetable may
 * or may not be based in swapper_pg_dir.  In any case,
 * paravirt_pagetable_init() will set up swapper_pg_dir
 * appropriately for the rest of the initialization to work.
 *
 * In general, pagetable_init() assumes that the pagetable may already
 * be partially populated, and so it avoids stomping on any existing
 * mappings.
 */
void __init early_ioremap_page_table_range_init(void)
{
        pgd_t *pgd_base = swapper_pg_dir;
        unsigned long vaddr, end;

        /*
         * Fixed mappings, only the page table structure has to be
         * created - mappings will be set by set_fixmap():
         */
        vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
        end = (FIXADDR_TOP + PMD_SIZE - 1) & PMD_MASK;
        page_table_range_init(vaddr, end, pgd_base);
        early_ioremap_reset();
}

static void __init pagetable_init(void)
{
        pgd_t *pgd_base = swapper_pg_dir;

        permanent_kmaps_init(pgd_base);
}

pteval_t __supported_pte_mask __read_mostly = ~(_PAGE_NX | _PAGE_GLOBAL);
EXPORT_SYMBOL_GPL(__supported_pte_mask);

/* user-defined highmem size */
static unsigned int highmem_pages = -1;

/*
 * highmem=size forces highmem to be exactly 'size' bytes.
 * This works even on boxes that have no highmem otherwise.
 * This also works to reduce highmem size on bigger boxes.
 */
static int __init parse_highmem(char *arg)
{
        if (!arg)
                return -EINVAL;

        highmem_pages = memparse(arg, &arg) >> PAGE_SHIFT;
        return 0;
}
early_param("highmem", parse_highmem);

#define MSG_HIGHMEM_TOO_BIG \
        "highmem size (%luMB) is bigger than pages available (%luMB)!\n"

#define MSG_LOWMEM_TOO_SMALL \
        "highmem size (%luMB) results in <64MB lowmem, ignoring it!\n"
/*
 * All of RAM fits into lowmem - but if user wants highmem
 * artificially via the highmem=x boot parameter then create
 * it:
 */
static void __init lowmem_pfn_init(void)
{
        /* max_low_pfn is 0, we already have early_res support */
        max_low_pfn = max_pfn;

        if (highmem_pages == -1)
                highmem_pages = 0;
#ifdef CONFIG_HIGHMEM
        if (highmem_pages >= max_pfn) {
                printk(KERN_ERR MSG_HIGHMEM_TOO_BIG,
                        pages_to_mb(highmem_pages), pages_to_mb(max_pfn));
                highmem_pages = 0;
        }
        if (highmem_pages) {
                if (max_low_pfn - highmem_pages < 64*1024*1024/PAGE_SIZE) {
                        printk(KERN_ERR MSG_LOWMEM_TOO_SMALL,
                                pages_to_mb(highmem_pages));
                        highmem_pages = 0;
                }
                max_low_pfn -= highmem_pages;
        }
#else
        if (highmem_pages)
                printk(KERN_ERR "ignoring highmem size on non-highmem kernel!\n");
#endif
}

#define MSG_HIGHMEM_TOO_SMALL \
        "only %luMB highmem pages available, ignoring highmem size of %luMB!\n"

#define MSG_HIGHMEM_TRIMMED \
        "Warning: only 4GB will be used. Use a HIGHMEM64G enabled kernel!\n"
/*
 * We have more RAM than fits into lowmem - we try to put it into
 * highmem, also taking the highmem=x boot parameter into account:
 */
static void __init highmem_pfn_init(void)
{
        max_low_pfn = MAXMEM_PFN;

        if (highmem_pages == -1)
                highmem_pages = max_pfn - MAXMEM_PFN;

        if (highmem_pages + MAXMEM_PFN < max_pfn)
                max_pfn = MAXMEM_PFN + highmem_pages;

        if (highmem_pages + MAXMEM_PFN > max_pfn) {
                printk(KERN_WARNING MSG_HIGHMEM_TOO_SMALL,
                        pages_to_mb(max_pfn - MAXMEM_PFN),
                        pages_to_mb(highmem_pages));
                highmem_pages = 0;
        }
#ifndef CONFIG_HIGHMEM
        /* Maximum memory usable is what is directly addressable */
        printk(KERN_WARNING "Warning only %ldMB will be used.\n", MAXMEM>>20);
        if (max_pfn > MAX_NONPAE_PFN)
                printk(KERN_WARNING "Use a HIGHMEM64G enabled kernel.\n");
        else
                printk(KERN_WARNING "Use a HIGHMEM enabled kernel.\n");
        max_pfn = MAXMEM_PFN;
#else /* !CONFIG_HIGHMEM */
#ifndef CONFIG_HIGHMEM64G
        if (max_pfn > MAX_NONPAE_PFN) {
                max_pfn = MAX_NONPAE_PFN;
                printk(KERN_WARNING MSG_HIGHMEM_TRIMMED);
        }
#endif /* !CONFIG_HIGHMEM64G */
#endif /* !CONFIG_HIGHMEM */
}

/*
 * Determine low and high memory ranges:
 */
void __init find_low_pfn_range(void)
{
        /* it could update max_pfn */

        if (max_pfn <= MAXMEM_PFN)
                lowmem_pfn_init();
        else
                highmem_pfn_init();
}

#ifndef CONFIG_NEED_MULTIPLE_NODES
void __init initmem_init(void)
{
#ifdef CONFIG_HIGHMEM
        highstart_pfn = highend_pfn = max_pfn;
        if (max_pfn > max_low_pfn)
                highstart_pfn = max_low_pfn;
        printk(KERN_NOTICE "%ldMB HIGHMEM available.\n",
                pages_to_mb(highend_pfn - highstart_pfn));
        high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
#else
        high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
#endif

        memblock_set_node(0, (phys_addr_t)ULLONG_MAX, &memblock.memory, 0);
        sparse_memory_present_with_active_regions(0);

#ifdef CONFIG_FLATMEM
        max_mapnr = IS_ENABLED(CONFIG_HIGHMEM) ? highend_pfn : max_low_pfn;
#endif
        __vmalloc_start_set = true;

        printk(KERN_NOTICE "%ldMB LOWMEM available.\n",
                        pages_to_mb(max_low_pfn));

        setup_bootmem_allocator();
}
#endif /* !CONFIG_NEED_MULTIPLE_NODES */

void __init setup_bootmem_allocator(void)
{
        printk(KERN_INFO "  mapped low ram: 0 - %08lx\n",
                 max_pfn_mapped<<PAGE_SHIFT);
        printk(KERN_INFO "  low ram: 0 - %08lx\n", max_low_pfn<<PAGE_SHIFT);
}

/*
 * paging_init() sets up the page tables - note that the first 8MB are
 * already mapped by head.S.
 *
 * This routines also unmaps the page at virtual kernel address 0, so
 * that we can trap those pesky NULL-reference errors in the kernel.
 */
void __init paging_init(void)
{
        pagetable_init();

        __flush_tlb_all();

        kmap_init();

        /*
         * NOTE: at this point the bootmem allocator is fully available.
         */
        olpc_dt_build_devicetree();
        sparse_memory_present_with_active_regions(MAX_NUMNODES);
        sparse_init();
        zone_sizes_init();
}

/*
 * Test if the WP bit works in supervisor mode. It isn't supported on 386's
 * and also on some strange 486's. All 586+'s are OK. This used to involve
 * black magic jumps to work around some nasty CPU bugs, but fortunately the
 * switch to using exceptions got rid of all that.
 */
static void __init test_wp_bit(void)
{
        printk(KERN_INFO
  "Checking if this processor honours the WP bit even in supervisor mode...");

        /* Any page-aligned address will do, the test is non-destructive */
        __set_fixmap(FIX_WP_TEST, __pa(&swapper_pg_dir), PAGE_KERNEL_RO);
        boot_cpu_data.wp_works_ok = do_test_wp_bit();
        clear_fixmap(FIX_WP_TEST);

        if (!boot_cpu_data.wp_works_ok) {
                printk(KERN_CONT "No.\n");
                panic("Linux doesn't support CPUs with broken WP.");
        } else {
                printk(KERN_CONT "Ok.\n");
        }
}

void __init mem_init(void)
{
        pci_iommu_alloc();

#ifdef CONFIG_FLATMEM
        BUG_ON(!mem_map);
#endif
        /*
         * With CONFIG_DEBUG_PAGEALLOC initialization of highmem pages has to
         * be done before free_all_bootmem(). Memblock use free low memory for
         * temporary data (see find_range_array()) and for this purpose can use
         * pages that was already passed to the buddy allocator, hence marked as
         * not accessible in the page tables when compiled with
         * CONFIG_DEBUG_PAGEALLOC. Otherwise order of initialization is not
         * important here.
         */
        set_highmem_pages_init();

        /* this will put all low memory onto the freelists */
        free_all_bootmem();

        after_bootmem = 1;

        mem_init_print_info(NULL);
        printk(KERN_INFO "virtual kernel memory layout:\n"
                "    fixmap  : 0x%08lx - 0x%08lx   (%4ld kB)\n"
#ifdef CONFIG_HIGHMEM
                "    pkmap   : 0x%08lx - 0x%08lx   (%4ld kB)\n"
#endif
                "    vmalloc : 0x%08lx - 0x%08lx   (%4ld MB)\n"
                "    lowmem  : 0x%08lx - 0x%08lx   (%4ld MB)\n"
                "      .init : 0x%08lx - 0x%08lx   (%4ld kB)\n"
                "      .data : 0x%08lx - 0x%08lx   (%4ld kB)\n"
                "      .text : 0x%08lx - 0x%08lx   (%4ld kB)\n",
                FIXADDR_START, FIXADDR_TOP,
                (FIXADDR_TOP - FIXADDR_START) >> 10,

#ifdef CONFIG_HIGHMEM
                PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE,
                (LAST_PKMAP*PAGE_SIZE) >> 10,
#endif

                VMALLOC_START, VMALLOC_END,
                (VMALLOC_END - VMALLOC_START) >> 20,

                (unsigned long)__va(0), (unsigned long)high_memory,
                ((unsigned long)high_memory - (unsigned long)__va(0)) >> 20,

                (unsigned long)&__init_begin, (unsigned long)&__init_end,
                ((unsigned long)&__init_end -
                 (unsigned long)&__init_begin) >> 10,

                (unsigned long)&_etext, (unsigned long)&_edata,
                ((unsigned long)&_edata - (unsigned long)&_etext) >> 10,

                (unsigned long)&_text, (unsigned long)&_etext,
                ((unsigned long)&_etext - (unsigned long)&_text) >> 10);

        /*
         * Check boundaries twice: Some fundamental inconsistencies can
         * be detected at build time already.
         */
#define __FIXADDR_TOP (-PAGE_SIZE)
#ifdef CONFIG_HIGHMEM
        BUILD_BUG_ON(PKMAP_BASE + LAST_PKMAP*PAGE_SIZE  > FIXADDR_START);
        BUILD_BUG_ON(VMALLOC_END                        > PKMAP_BASE);
#endif
#define high_memory (-128UL << 20)
        BUILD_BUG_ON(VMALLOC_START                      >= VMALLOC_END);
#undef high_memory
#undef __FIXADDR_TOP

#ifdef CONFIG_HIGHMEM
        BUG_ON(PKMAP_BASE + LAST_PKMAP*PAGE_SIZE        > FIXADDR_START);
        BUG_ON(VMALLOC_END                              > PKMAP_BASE);
#endif
        BUG_ON(VMALLOC_START                            >= VMALLOC_END);
        BUG_ON((unsigned long)high_memory               > VMALLOC_START);

        if (boot_cpu_data.wp_works_ok < 0)
                test_wp_bit();
}

#ifdef CONFIG_MEMORY_HOTPLUG
int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
{
        struct pglist_data *pgdata = NODE_DATA(nid);
        struct zone *zone = pgdata->node_zones +
                zone_for_memory(nid, start, size, ZONE_HIGHMEM, for_device);
        unsigned long start_pfn = start >> PAGE_SHIFT;
        unsigned long nr_pages = size >> PAGE_SHIFT;

        return __add_pages(nid, zone, start_pfn, nr_pages);
}

#ifdef CONFIG_MEMORY_HOTREMOVE
int arch_remove_memory(u64 start, u64 size)
{
        unsigned long start_pfn = start >> PAGE_SHIFT;
        unsigned long nr_pages = size >> PAGE_SHIFT;
        struct zone *zone;

        zone = page_zone(pfn_to_page(start_pfn));
        return __remove_pages(zone, start_pfn, nr_pages);
}
#endif
#endif

/*
 * This function cannot be __init, since exceptions don't work in that
 * section.  Put this after the callers, so that it cannot be inlined.
 */
static noinline int do_test_wp_bit(void)
{
        char tmp_reg;
        int flag;

        __asm__ __volatile__(
                "       movb %0, %1     \n"
                "1:     movb %1, %0     \n"
                "       xorl %2, %2     \n"
                "2:                     \n"
                _ASM_EXTABLE(1b,2b)
                :"=m" (*(char *)fix_to_virt(FIX_WP_TEST)),
                 "=q" (tmp_reg),
                 "=r" (flag)
                :"2" (1)
                :"memory");

        return flag;
}

int kernel_set_to_readonly __read_mostly;

void set_kernel_text_rw(void)
{
        unsigned long start = PFN_ALIGN(_text);
        unsigned long size = PFN_ALIGN(_etext) - start;

        if (!kernel_set_to_readonly)
                return;

        pr_debug("Set kernel text: %lx - %lx for read write\n",
                 start, start+size);

        set_pages_rw(virt_to_page(start), size >> PAGE_SHIFT);
}

void set_kernel_text_ro(void)
{
        unsigned long start = PFN_ALIGN(_text);
        unsigned long size = PFN_ALIGN(_etext) - start;

        if (!kernel_set_to_readonly)
                return;

        pr_debug("Set kernel text: %lx - %lx for read only\n",
                 start, start+size);

        set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
}

static void mark_nxdata_nx(void)
{
        /*
         * When this called, init has already been executed and released,
         * so everything past _etext should be NX.
         */
        unsigned long start = PFN_ALIGN(_etext);
        /*
         * This comes from is_kernel_text upper limit. Also HPAGE where used:
         */
        unsigned long size = (((unsigned long)__init_end + HPAGE_SIZE) & HPAGE_MASK) - start;

        if (__supported_pte_mask & _PAGE_NX)
                printk(KERN_INFO "NX-protecting the kernel data: %luk\n", size >> 10);
        set_pages_nx(virt_to_page(start), size >> PAGE_SHIFT);
}

void mark_rodata_ro(void)
{
        unsigned long start = PFN_ALIGN(_text);
        unsigned long size = PFN_ALIGN(_etext) - start;

        set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
        printk(KERN_INFO "Write protecting the kernel text: %luk\n",
                size >> 10);

        kernel_set_to_readonly = 1;

#ifdef CONFIG_CPA_DEBUG
        printk(KERN_INFO "Testing CPA: Reverting %lx-%lx\n",
                start, start+size);
        set_pages_rw(virt_to_page(start), size>>PAGE_SHIFT);

        printk(KERN_INFO "Testing CPA: write protecting again\n");
        set_pages_ro(virt_to_page(start), size>>PAGE_SHIFT);
#endif

        start += size;
        size = (unsigned long)__end_rodata - start;
        set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
        printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
                size >> 10);

#ifdef CONFIG_CPA_DEBUG
        printk(KERN_INFO "Testing CPA: undo %lx-%lx\n", start, start + size);
        set_pages_rw(virt_to_page(start), size >> PAGE_SHIFT);

        printk(KERN_INFO "Testing CPA: write protecting again\n");
        set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
#endif
        mark_nxdata_nx();
        if (__supported_pte_mask & _PAGE_NX)
                debug_checkwx();
}