Merge branch 'fixes-jgarzik' of git://git.kernel.org/pub/scm/linux/kernel/git/linvill...

[mirror_ubuntu-jammy-kernel.git] / arch / x86 / mm / init_32.c

/*
 *  linux/arch/i386/mm/init.c
 *
 *  Copyright (C) 1995  Linus Torvalds
 *
 *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
 */

#include <linux/module.h>
#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/pfn.h>
#include <linux/poison.h>
#include <linux/bootmem.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/efi.h>
#include <linux/memory_hotplug.h>
#include <linux/initrd.h>
#include <linux/cpumask.h>

#include <asm/processor.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/dma.h>
#include <asm/fixmap.h>
#include <asm/e820.h>
#include <asm/apic.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/paravirt.h>

unsigned int __VMALLOC_RESERVE = 128 << 20;

DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
unsigned long highstart_pfn, highend_pfn;

static int noinline do_test_wp_bit(void);

/*
 * 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_bootmem_low_pages(PAGE_SIZE);

                paravirt_alloc_pd(__pa(pmd_table) >> PAGE_SHIFT);
                set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
                pud = pud_offset(pgd, 0);
                if (pmd_table != pmd_offset(pud, 0))
                        BUG();
        }
#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 = NULL;

#ifdef CONFIG_DEBUG_PAGEALLOC
                page_table = (pte_t *) alloc_bootmem_pages(PAGE_SIZE);
#endif
                if (!page_table)
                        page_table =
                                (pte_t *)alloc_bootmem_low_pages(PAGE_SIZE);

                paravirt_alloc_pt(&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);
}

/*
 * 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)
{
        pgd_t *pgd;
        pmd_t *pmd;
        int pgd_idx, pmd_idx;
        unsigned long vaddr;

        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++) {
                        one_page_table_init(pmd);

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

static inline int is_kernel_text(unsigned long addr)
{
        if (addr >= PAGE_OFFSET && 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.
 */
static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
{
        unsigned long pfn;
        pgd_t *pgd;
        pmd_t *pmd;
        pte_t *pte;
        int pgd_idx, pmd_idx, pte_ofs;

        pgd_idx = pgd_index(PAGE_OFFSET);
        pgd = pgd_base + pgd_idx;
        pfn = 0;

        for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
                pmd = one_md_table_init(pgd);
                if (pfn >= max_low_pfn)
                        continue;
                for (pmd_idx = 0; pmd_idx < PTRS_PER_PMD && pfn < max_low_pfn; pmd++, pmd_idx++) {
                        unsigned int address = pfn * PAGE_SIZE + PAGE_OFFSET;

                        /* Map with big pages if possible, otherwise create normal page tables. */
                        if (cpu_has_pse) {
                                unsigned int address2 = (pfn + PTRS_PER_PTE - 1) * PAGE_SIZE + PAGE_OFFSET + PAGE_SIZE-1;
                                if (is_kernel_text(address) || is_kernel_text(address2))
                                        set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE_EXEC));
                                else
                                        set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE));

                                pfn += PTRS_PER_PTE;
                        } else {
                                pte = one_page_table_init(pmd);

                                for (pte_ofs = 0;
                                     pte_ofs < PTRS_PER_PTE && pfn < max_low_pfn;
                                     pte++, pfn++, pte_ofs++, address += PAGE_SIZE) {
                                        if (is_kernel_text(address))
                                                set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
                                        else
                                                set_pte(pte, pfn_pte(pfn, PAGE_KERNEL));
                                }
                        }
                }
        }
}

static inline int page_kills_ppro(unsigned long pagenr)
{
        if (pagenr >= 0x70000 && pagenr <= 0x7003F)
                return 1;
        return 0;
}

int page_is_ram(unsigned long pagenr)
{
        int i;
        unsigned long addr, end;

        if (efi_enabled) {
                efi_memory_desc_t *md;
                void *p;

                for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
                        md = p;
                        if (!is_available_memory(md))
                                continue;
                        addr = (md->phys_addr+PAGE_SIZE-1) >> PAGE_SHIFT;
                        end = (md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT)) >> PAGE_SHIFT;

                        if ((pagenr >= addr) && (pagenr < end))
                                return 1;
                }
                return 0;
        }

        for (i = 0; i < e820.nr_map; i++) {

                if (e820.map[i].type != E820_RAM)       /* not usable memory */
                        continue;
                /*
                 *      !!!FIXME!!! Some BIOSen report areas as RAM that
                 *      are not. Notably the 640->1Mb area. We need a sanity
                 *      check here.
                 */
                addr = (e820.map[i].addr+PAGE_SIZE-1) >> PAGE_SHIFT;
                end = (e820.map[i].addr+e820.map[i].size) >> PAGE_SHIFT;
                if  ((pagenr >= addr) && (pagenr < end))
                        return 1;
        }
        return 0;
}

#ifdef CONFIG_HIGHMEM
pte_t *kmap_pte;
pgprot_t kmap_prot;

#define kmap_get_fixmap_pte(vaddr)                                      \
        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);

        kmap_prot = PAGE_KERNEL;
}

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

        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; 
}

static void __meminit free_new_highpage(struct page *page)
{
        init_page_count(page);
        __free_page(page);
        totalhigh_pages++;
}

void __init add_one_highpage_init(struct page *page, int pfn, int bad_ppro)
{
        if (page_is_ram(pfn) && !(bad_ppro && page_kills_ppro(pfn))) {
                ClearPageReserved(page);
                free_new_highpage(page);
        } else
                SetPageReserved(page);
}

static int __meminit add_one_highpage_hotplug(struct page *page, unsigned long pfn)
{
        free_new_highpage(page);
        totalram_pages++;
#ifdef CONFIG_FLATMEM
        max_mapnr = max(pfn, max_mapnr);
#endif
        num_physpages++;
        return 0;
}

/*
 * Not currently handling the NUMA case.
 * Assuming single node and all memory that
 * has been added dynamically that would be
 * onlined here is in HIGHMEM
 */
void __meminit online_page(struct page *page)
{
        ClearPageReserved(page);
        add_one_highpage_hotplug(page, page_to_pfn(page));
}


#ifdef CONFIG_NUMA
extern void set_highmem_pages_init(int);
#else
static void __init set_highmem_pages_init(int bad_ppro)
{
        int pfn;
        for (pfn = highstart_pfn; pfn < highend_pfn; pfn++)
                add_one_highpage_init(pfn_to_page(pfn), pfn, bad_ppro);
        totalram_pages += totalhigh_pages;
}
#endif /* CONFIG_FLATMEM */

#else
#define kmap_init() do { } while (0)
#define permanent_kmaps_init(pgd_base) do { } while (0)
#define set_highmem_pages_init(bad_ppro) do { } while (0)
#endif /* CONFIG_HIGHMEM */

unsigned long long __PAGE_KERNEL = _PAGE_KERNEL;
EXPORT_SYMBOL(__PAGE_KERNEL);
unsigned long long __PAGE_KERNEL_EXEC = _PAGE_KERNEL_EXEC;

#ifdef CONFIG_NUMA
extern void __init remap_numa_kva(void);
#else
#define remap_numa_kva() do {} while (0)
#endif

void __init native_pagetable_setup_start(pgd_t *base)
{
#ifdef CONFIG_X86_PAE
        int i;

        /*
         * Init entries of the first-level page table to the
         * zero page, if they haven't already been set up.
         *
         * In a normal native boot, we'll be running on a
         * pagetable rooted in swapper_pg_dir, but not in PAE
         * mode, so this will end up clobbering the mappings
         * for the lower 24Mbytes of the address space,
         * without affecting the kernel address space.
         */
        for (i = 0; i < USER_PTRS_PER_PGD; i++)
                set_pgd(&base[i],
                        __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));

        /* Make sure kernel address space is empty so that a pagetable
           will be allocated for it. */
        memset(&base[USER_PTRS_PER_PGD], 0,
               KERNEL_PGD_PTRS * sizeof(pgd_t));
#else
        paravirt_alloc_pd(__pa(swapper_pg_dir) >> PAGE_SHIFT);
#endif
}

void __init native_pagetable_setup_done(pgd_t *base)
{
#ifdef CONFIG_X86_PAE
        /*
         * Add low memory identity-mappings - SMP needs it when
         * starting up on an AP from real-mode. In the non-PAE
         * case we already have these mappings through head.S.
         * All user-space mappings are explicitly cleared after
         * SMP startup.
         */
        set_pgd(&base[0], base[USER_PTRS_PER_PGD]);
#endif
}

/*
 * 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/i386/kernel/head.S, and not running in PAE mode
 * (even if we'll end up running in PAE).  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_setup_start() 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.
 */
static void __init pagetable_init (void)
{
        unsigned long vaddr, end;
        pgd_t *pgd_base = swapper_pg_dir;

        paravirt_pagetable_setup_start(pgd_base);

        /* Enable PSE if available */
        if (cpu_has_pse)
                set_in_cr4(X86_CR4_PSE);

        /* Enable PGE if available */
        if (cpu_has_pge) {
                set_in_cr4(X86_CR4_PGE);
                __PAGE_KERNEL |= _PAGE_GLOBAL;
                __PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
        }

        kernel_physical_mapping_init(pgd_base);
        remap_numa_kva();

        /*
         * 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);

        permanent_kmaps_init(pgd_base);

        paravirt_pagetable_setup_done(pgd_base);
}

#if defined(CONFIG_HIBERNATION) || defined(CONFIG_ACPI)
/*
 * Swap suspend & friends need this for resume because things like the intel-agp
 * driver might have split up a kernel 4MB mapping.
 */
char __nosavedata swsusp_pg_dir[PAGE_SIZE]
        __attribute__ ((aligned (PAGE_SIZE)));

static inline void save_pg_dir(void)
{
        memcpy(swsusp_pg_dir, swapper_pg_dir, PAGE_SIZE);
}
#else
static inline void save_pg_dir(void)
{
}
#endif

void zap_low_mappings (void)
{
        int i;

        save_pg_dir();

        /*
         * Zap initial low-memory mappings.
         *
         * Note that "pgd_clear()" doesn't do it for
         * us, because pgd_clear() is a no-op on i386.
         */
        for (i = 0; i < USER_PTRS_PER_PGD; i++)
#ifdef CONFIG_X86_PAE
                set_pgd(swapper_pg_dir+i, __pgd(1 + __pa(empty_zero_page)));
#else
                set_pgd(swapper_pg_dir+i, __pgd(0));
#endif
        flush_tlb_all();
}

int nx_enabled = 0;

#ifdef CONFIG_X86_PAE

static int disable_nx __initdata = 0;
u64 __supported_pte_mask __read_mostly = ~_PAGE_NX;
EXPORT_SYMBOL_GPL(__supported_pte_mask);

/*
 * noexec = on|off
 *
 * Control non executable mappings.
 *
 * on      Enable
 * off     Disable
 */
static int __init noexec_setup(char *str)
{
        if (!str || !strcmp(str, "on")) {
                if (cpu_has_nx) {
                        __supported_pte_mask |= _PAGE_NX;
                        disable_nx = 0;
                }
        } else if (!strcmp(str,"off")) {
                disable_nx = 1;
                __supported_pte_mask &= ~_PAGE_NX;
        } else
                return -EINVAL;

        return 0;
}
early_param("noexec", noexec_setup);

static void __init set_nx(void)
{
        unsigned int v[4], l, h;

        if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
                cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
                if ((v[3] & (1 << 20)) && !disable_nx) {
                        rdmsr(MSR_EFER, l, h);
                        l |= EFER_NX;
                        wrmsr(MSR_EFER, l, h);
                        nx_enabled = 1;
                        __supported_pte_mask |= _PAGE_NX;
                }
        }
}

/*
 * Enables/disables executability of a given kernel page and
 * returns the previous setting.
 */
int __init set_kernel_exec(unsigned long vaddr, int enable)
{
        pte_t *pte;
        int ret = 1;

        if (!nx_enabled)
                goto out;

        pte = lookup_address(vaddr);
        BUG_ON(!pte);

        if (!pte_exec_kernel(*pte))
                ret = 0;

        if (enable)
                pte->pte_high &= ~(1 << (_PAGE_BIT_NX - 32));
        else
                pte->pte_high |= 1 << (_PAGE_BIT_NX - 32);
        pte_update_defer(&init_mm, vaddr, pte);
        __flush_tlb_all();
out:
        return ret;
}

#endif

/*
 * 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)
{
#ifdef CONFIG_X86_PAE
        set_nx();
        if (nx_enabled)
                printk("NX (Execute Disable) protection: active\n");
#endif

        pagetable_init();

        load_cr3(swapper_pg_dir);

#ifdef CONFIG_X86_PAE
        /*
         * We will bail out later - printk doesn't work right now so
         * the user would just see a hanging kernel.
         */
        if (cpu_has_pae)
                set_in_cr4(X86_CR4_PAE);
#endif
        __flush_tlb_all();

        kmap_init();
}

/*
 * Test if the WP bit works in supervisor mode. It isn't supported on 386's
 * and also on some strange 486's (NexGen etc.). 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("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_READONLY);
        boot_cpu_data.wp_works_ok = do_test_wp_bit();
        clear_fixmap(FIX_WP_TEST);

        if (!boot_cpu_data.wp_works_ok) {
                printk("No.\n");
#ifdef CONFIG_X86_WP_WORKS_OK
                panic("This kernel doesn't support CPU's with broken WP. Recompile it for a 386!");
#endif
        } else {
                printk("Ok.\n");
        }
}

static struct kcore_list kcore_mem, kcore_vmalloc; 

void __init mem_init(void)
{
        extern int ppro_with_ram_bug(void);
        int codesize, reservedpages, datasize, initsize;
        int tmp;
        int bad_ppro;

#ifdef CONFIG_FLATMEM
        BUG_ON(!mem_map);
#endif
        
        bad_ppro = ppro_with_ram_bug();

#ifdef CONFIG_HIGHMEM
        /* check that fixmap and pkmap do not overlap */
        if (PKMAP_BASE+LAST_PKMAP*PAGE_SIZE >= FIXADDR_START) {
                printk(KERN_ERR "fixmap and kmap areas overlap - this will crash\n");
                printk(KERN_ERR "pkstart: %lxh pkend: %lxh fixstart %lxh\n",
                                PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE, FIXADDR_START);
                BUG();
        }
#endif
 
        /* this will put all low memory onto the freelists */
        totalram_pages += free_all_bootmem();

        reservedpages = 0;
        for (tmp = 0; tmp < max_low_pfn; tmp++)
                /*
                 * Only count reserved RAM pages
                 */
                if (page_is_ram(tmp) && PageReserved(pfn_to_page(tmp)))
                        reservedpages++;

        set_highmem_pages_init(bad_ppro);

        codesize =  (unsigned long) &_etext - (unsigned long) &_text;
        datasize =  (unsigned long) &_edata - (unsigned long) &_etext;
        initsize =  (unsigned long) &__init_end - (unsigned long) &__init_begin;

        kclist_add(&kcore_mem, __va(0), max_low_pfn << PAGE_SHIFT); 
        kclist_add(&kcore_vmalloc, (void *)VMALLOC_START, 
                   VMALLOC_END-VMALLOC_START);

        printk(KERN_INFO "Memory: %luk/%luk available (%dk kernel code, %dk reserved, %dk data, %dk init, %ldk highmem)\n",
                (unsigned long) nr_free_pages() << (PAGE_SHIFT-10),
                num_physpages << (PAGE_SHIFT-10),
                codesize >> 10,
                reservedpages << (PAGE_SHIFT-10),
                datasize >> 10,
                initsize >> 10,
                (unsigned long) (totalhigh_pages << (PAGE_SHIFT-10))
               );

#if 1 /* double-sanity-check paranoia */
        printk("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);

#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);
#endif /* double-sanity-check paranoia */

#ifdef CONFIG_X86_PAE
        if (!cpu_has_pae)
                panic("cannot execute a PAE-enabled kernel on a PAE-less CPU!");
#endif
        if (boot_cpu_data.wp_works_ok < 0)
                test_wp_bit();

        /*
         * Subtle. SMP is doing it's boot stuff late (because it has to
         * fork idle threads) - but it also needs low mappings for the
         * protected-mode entry to work. We zap these entries only after
         * the WP-bit has been tested.
         */
#ifndef CONFIG_SMP
        zap_low_mappings();
#endif
}

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

        return __add_pages(zone, start_pfn, nr_pages);
}

#endif

struct kmem_cache *pmd_cache;

void __init pgtable_cache_init(void)
{
        if (PTRS_PER_PMD > 1)
                pmd_cache = kmem_cache_create("pmd",
                                              PTRS_PER_PMD*sizeof(pmd_t),
                                              PTRS_PER_PMD*sizeof(pmd_t),
                                              SLAB_PANIC,
                                              pmd_ctor);
}

/*
 * 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 int noinline 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"
                ".section __ex_table,\"a\"\n"
                "       .align 4        \n"
                "       .long 1b,2b     \n"
                ".previous              \n"
                :"=m" (*(char *)fix_to_virt(FIX_WP_TEST)),
                 "=q" (tmp_reg),
                 "=r" (flag)
                :"2" (1)
                :"memory");
        
        return flag;
}

#ifdef CONFIG_DEBUG_RODATA

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

#ifndef CONFIG_KPROBES
#ifdef CONFIG_HOTPLUG_CPU
        /* It must still be possible to apply SMP alternatives. */
        if (num_possible_cpus() <= 1)
#endif
        {
                change_page_attr(virt_to_page(start),
                                 size >> PAGE_SHIFT, PAGE_KERNEL_RX);
                printk("Write protecting the kernel text: %luk\n", size >> 10);
        }
#endif
        start += size;
        size = (unsigned long)__end_rodata - start;
        change_page_attr(virt_to_page(start),
                         size >> PAGE_SHIFT, PAGE_KERNEL_RO);
        printk("Write protecting the kernel read-only data: %luk\n",
               size >> 10);

        /*
         * change_page_attr() requires a global_flush_tlb() call after it.
         * We do this after the printk so that if something went wrong in the
         * change, the printk gets out at least to give a better debug hint
         * of who is the culprit.
         */
        global_flush_tlb();
}
#endif

void free_init_pages(char *what, unsigned long begin, unsigned long end)
{
        unsigned long addr;

        for (addr = begin; addr < end; addr += PAGE_SIZE) {
                ClearPageReserved(virt_to_page(addr));
                init_page_count(virt_to_page(addr));
                memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
                free_page(addr);
                totalram_pages++;
        }
        printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
}

void free_initmem(void)
{
        free_init_pages("unused kernel memory",
                        (unsigned long)(&__init_begin),
                        (unsigned long)(&__init_end));
}

#ifdef CONFIG_BLK_DEV_INITRD
void free_initrd_mem(unsigned long start, unsigned long end)
{
        free_init_pages("initrd memory", start, end);
}
#endif