pgtable.c

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#include <linux/mm.h>
#include <linux/gfp.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/tlb.h>
#include <asm/fixmap.h>

#define PGALLOC_GFP GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO

#ifdef CONFIG_HIGHPTE
#define PGALLOC_USER_GFP __GFP_HIGHMEM
#else
#define PGALLOC_USER_GFP 0
#endif

gfp_t __userpte_alloc_gfp = PGALLOC_GFP | PGALLOC_USER_GFP;

pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
{
    return (pte_t *)__get_free_page(PGALLOC_GFP);
}

pgtable_t pte_alloc_one(struct mm_struct *mm, unsigned long address)
{
    struct page *pte;

    pte = alloc_pages(__userpte_alloc_gfp, 0);
    if (pte)
        pgtable_page_ctor(pte);
    return pte;
}

static int __init setup_userpte(char *arg)
{
    if (!arg)
        return -EINVAL;

    /*
     * "userpte=nohigh" disables allocation of user pagetables in
     * high memory.
     */
    if (strcmp(arg, "nohigh") == 0)
        __userpte_alloc_gfp &= ~__GFP_HIGHMEM;
    else
        return -EINVAL;
    return 0;
}
early_param("userpte", setup_userpte);

void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
{
    pgtable_page_dtor(pte);
    paravirt_release_pte(page_to_pfn(pte));
    tlb_remove_page(tlb, pte);
}

#if PAGETABLE_LEVELS > 2
void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
{
    paravirt_release_pmd(__pa(pmd) >> PAGE_SHIFT);
    tlb_remove_page(tlb, virt_to_page(pmd));
}

#if PAGETABLE_LEVELS > 3
void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
{
    paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
    tlb_remove_page(tlb, virt_to_page(pud));
}
#endif  /* PAGETABLE_LEVELS > 3 */
#endif  /* PAGETABLE_LEVELS > 2 */

static inline void pgd_list_add(pgd_t *pgd)
{
    struct page *page = virt_to_page(pgd);

    list_add(&page->lru, &pgd_list);
}

static inline void pgd_list_del(pgd_t *pgd)
{
    struct page *page = virt_to_page(pgd);

    list_del(&page->lru);
}

#define UNSHARED_PTRS_PER_PGD               \
    (SHARED_KERNEL_PMD ? KERNEL_PGD_BOUNDARY : PTRS_PER_PGD)


static void pgd_set_mm(pgd_t *pgd, struct mm_struct *mm)
{
    BUILD_BUG_ON(sizeof(virt_to_page(pgd)->index) < sizeof(mm));
    virt_to_page(pgd)->index = (pgoff_t)mm;
}

struct mm_struct *pgd_page_get_mm(struct page *page)
{
    return (struct mm_struct *)page->index;
}

static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd)
{
    /* If the pgd points to a shared pagetable level (either the
       ptes in non-PAE, or shared PMD in PAE), then just copy the
       references from swapper_pg_dir. */
    if (PAGETABLE_LEVELS == 2 ||
        (PAGETABLE_LEVELS == 3 && SHARED_KERNEL_PMD) ||
        PAGETABLE_LEVELS == 4) {
        clone_pgd_range(pgd + KERNEL_PGD_BOUNDARY,
                swapper_pg_dir + KERNEL_PGD_BOUNDARY,
                KERNEL_PGD_PTRS);
    }

    /* list required to sync kernel mapping updates */
    if (!SHARED_KERNEL_PMD) {
        pgd_set_mm(pgd, mm);
        pgd_list_add(pgd);
    }
}

static void pgd_dtor(pgd_t *pgd)
{
    if (SHARED_KERNEL_PMD)
        return;

    spin_lock(&pgd_lock);
    pgd_list_del(pgd);
    spin_unlock(&pgd_lock);
}

/*
 * List of all pgd's needed for non-PAE so it can invalidate entries
 * in both cached and uncached pgd's; not needed for PAE since the
 * kernel pmd is shared. If PAE were not to share the pmd a similar
 * tactic would be needed. This is essentially codepath-based locking
 * against pageattr.c; it is the unique case in which a valid change
 * of kernel pagetables can't be lazily synchronized by vmalloc faults.
 * vmalloc faults work because attached pagetables are never freed.
 * -- wli
 */

#ifdef CONFIG_X86_PAE
/*
 * In PAE mode, we need to do a cr3 reload (=tlb flush) when
 * updating the top-level pagetable entries to guarantee the
 * processor notices the update.  Since this is expensive, and
 * all 4 top-level entries are used almost immediately in a
 * new process's life, we just pre-populate them here.
 *
 * Also, if we're in a paravirt environment where the kernel pmd is
 * not shared between pagetables (!SHARED_KERNEL_PMDS), we allocate
 * and initialize the kernel pmds here.
 */
#define PREALLOCATED_PMDS   UNSHARED_PTRS_PER_PGD

void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd)
{
    paravirt_alloc_pmd(mm, __pa(pmd) >> PAGE_SHIFT);

    /* Note: almost everything apart from _PAGE_PRESENT is
       reserved at the pmd (PDPT) level. */
    set_pud(pudp, __pud(__pa(pmd) | _PAGE_PRESENT));

    /*
     * According to Intel App note "TLBs, Paging-Structure Caches,
     * and Their Invalidation", April 2007, document 317080-001,
     * section 8.1: in PAE mode we explicitly have to flush the
     * TLB via cr3 if the top-level pgd is changed...
     */
    flush_tlb_mm(mm);
}
#else  /* !CONFIG_X86_PAE */

/* No need to prepopulate any pagetable entries in non-PAE modes. */
#define PREALLOCATED_PMDS   0

#endif  /* CONFIG_X86_PAE */

static void free_pmds(pmd_t *pmds[])
{
    int i;

    for(i = 0; i < PREALLOCATED_PMDS; i++)
        if (pmds[i])
            free_page((unsigned long)pmds[i]);
}

static int preallocate_pmds(pmd_t *pmds[])
{
    int i;
    bool failed = false;

    for(i = 0; i < PREALLOCATED_PMDS; i++) {
        pmd_t *pmd = (pmd_t *)__get_free_page(PGALLOC_GFP);
        if (pmd == NULL)
            failed = true;
        pmds[i] = pmd;
    }

    if (failed) {
        free_pmds(pmds);
        return -ENOMEM;
    }

    return 0;
}

/*
 * Mop up any pmd pages which may still be attached to the pgd.
 * Normally they will be freed by munmap/exit_mmap, but any pmd we
 * preallocate which never got a corresponding vma will need to be
 * freed manually.
 */
static void pgd_mop_up_pmds(struct mm_struct *mm, pgd_t *pgdp)
{
    int i;

    for(i = 0; i < PREALLOCATED_PMDS; i++) {
        pgd_t pgd = pgdp[i];

        if (pgd_val(pgd) != 0) {
            pmd_t *pmd = (pmd_t *)pgd_page_vaddr(pgd);

            pgdp[i] = native_make_pgd(0);

            paravirt_release_pmd(pgd_val(pgd) >> PAGE_SHIFT);
            pmd_free(mm, pmd);
        }
    }
}

static void pgd_prepopulate_pmd(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmds[])
{
    pud_t *pud;
    unsigned long addr;
    int i;

    if (PREALLOCATED_PMDS == 0) /* Work around gcc-3.4.x bug */
        return;

    pud = pud_offset(pgd, 0);

    for (addr = i = 0; i < PREALLOCATED_PMDS;
         i++, pud++, addr += PUD_SIZE) {
        pmd_t *pmd = pmds[i];

        if (i >= KERNEL_PGD_BOUNDARY)
            memcpy(pmd, (pmd_t *)pgd_page_vaddr(swapper_pg_dir[i]),
                   sizeof(pmd_t) * PTRS_PER_PMD);

        pud_populate(mm, pud, pmd);
    }
}

pgd_t *pgd_alloc(struct mm_struct *mm)
{
    pgd_t *pgd;
    pmd_t *pmds[PREALLOCATED_PMDS];

    pgd = (pgd_t *)__get_free_page(PGALLOC_GFP);

    if (pgd == NULL)
        goto out;

    mm->pgd = pgd;

    if (preallocate_pmds(pmds) != 0)
        goto out_free_pgd;

    if (paravirt_pgd_alloc(mm) != 0)
        goto out_free_pmds;

    /*
     * Make sure that pre-populating the pmds is atomic with
     * respect to anything walking the pgd_list, so that they
     * never see a partially populated pgd.
     */
    spin_lock(&pgd_lock);

    pgd_ctor(mm, pgd);
    pgd_prepopulate_pmd(mm, pgd, pmds);

    spin_unlock(&pgd_lock);

    return pgd;

out_free_pmds:
    free_pmds(pmds);
out_free_pgd:
    free_page((unsigned long)pgd);
out:
    return NULL;
}

void pgd_free(struct mm_struct *mm, pgd_t *pgd)
{
    pgd_mop_up_pmds(mm, pgd);
    pgd_dtor(pgd);
    paravirt_pgd_free(mm, pgd);
    free_page((unsigned long)pgd);
}

int ptep_set_access_flags(struct vm_area_struct *vma,
              unsigned long address, pte_t *ptep,
              pte_t entry, int dirty)
{
    int changed = !pte_same(*ptep, entry);

    if (changed && dirty) {
        *ptep = entry;
        pte_update_defer(vma->vm_mm, address, ptep);
        flush_tlb_page(vma, address);
    }

    return changed;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pmdp_set_access_flags(struct vm_area_struct *vma,
              unsigned long address, pmd_t *pmdp,
              pmd_t entry, int dirty)
{
    int changed = !pmd_same(*pmdp, entry);

    VM_BUG_ON(address & ~HPAGE_PMD_MASK);

    if (changed && dirty) {
        *pmdp = entry;
        pmd_update_defer(vma->vm_mm, address, pmdp);
        flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
    }

    return changed;
}
#endif

int ptep_test_and_clear_young(struct vm_area_struct *vma,
                  unsigned long addr, pte_t *ptep)
{
    int ret = 0;

    if (pte_young(*ptep))
        ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
                     (unsigned long *) &ptep->pte);

    if (ret)
        pte_update(vma->vm_mm, addr, ptep);

    return ret;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pmdp_test_and_clear_young(struct vm_area_struct *vma,
                  unsigned long addr, pmd_t *pmdp)
{
    int ret = 0;

    if (pmd_young(*pmdp))
        ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
                     (unsigned long *)pmdp);

    if (ret)
        pmd_update(vma->vm_mm, addr, pmdp);

    return ret;
}
#endif

int ptep_clear_flush_young(struct vm_area_struct *vma,
               unsigned long address, pte_t *ptep)
{
    int young;

    young = ptep_test_and_clear_young(vma, address, ptep);
    if (young)
        flush_tlb_page(vma, address);

    return young;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pmdp_clear_flush_young(struct vm_area_struct *vma,
               unsigned long address, pmd_t *pmdp)
{
    int young;

    VM_BUG_ON(address & ~HPAGE_PMD_MASK);

    young = pmdp_test_and_clear_young(vma, address, pmdp);
    if (young)
        flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

    return young;
}

void pmdp_splitting_flush(struct vm_area_struct *vma,
              unsigned long address, pmd_t *pmdp)
{
    int set;
    VM_BUG_ON(address & ~HPAGE_PMD_MASK);
    set = !test_and_set_bit(_PAGE_BIT_SPLITTING,
                (unsigned long *)pmdp);
    if (set) {
        pmd_update(vma->vm_mm, address, pmdp);
        /* need tlb flush only to serialize against gup-fast */
        flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
    }
}
#endif

void __init reserve_top_address(unsigned long reserve)
{
#ifdef CONFIG_X86_32
    BUG_ON(fixmaps_set > 0);
    printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",
           (int)-reserve);
    __FIXADDR_TOP = -reserve - PAGE_SIZE;
#endif
}

int fixmaps_set;

void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)
{
    unsigned long address = __fix_to_virt(idx);

    if (idx >= __end_of_fixed_addresses) {
        BUG();
        return;
    }
    set_pte_vaddr(address, pte);
    fixmaps_set++;
}

void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
               pgprot_t flags)
{
    __native_set_fixmap(idx, pfn_pte(phys >> PAGE_SHIFT, flags));
}