ARM: mmp: fix potential NULL dereference

[linux/fpc-iii.git] / arch / x86 / mm / pgtable.c

#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

/**
 * reserve_top_address - reserves a hole in the top of kernel address space
 * @reserve - size of hole to reserve
 *
 * Can be used to relocate the fixmap area and poke a hole in the top
 * of kernel address space to make room for a hypervisor.
 */
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));
}