x86/ldt: Make the LDT mapping RO

[mirror_ubuntu-bionic-kernel.git] / arch / x86 / mm / pgtable.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/mm.h>
#include <linux/gfp.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/tlb.h>
#include <asm/fixmap.h>
#include <asm/mtrr.h>

#define PGALLOC_GFP (GFP_KERNEL_ACCOUNT | __GFP_NOTRACK | __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 & ~__GFP_ACCOUNT);
}

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

        pte = alloc_pages(__userpte_alloc_gfp, 0);
        if (!pte)
                return NULL;
        if (!pgtable_page_ctor(pte)) {
                __free_page(pte);
                return NULL;
        }
        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_table(tlb, pte);
}

#if CONFIG_PGTABLE_LEVELS > 2
void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
{
        struct page *page = virt_to_page(pmd);
        paravirt_release_pmd(__pa(pmd) >> PAGE_SHIFT);
        /*
         * NOTE! For PAE, any changes to the top page-directory-pointer-table
         * entries need a full cr3 reload to flush.
         */
#ifdef CONFIG_X86_PAE
        tlb->need_flush_all = 1;
#endif
        pgtable_pmd_page_dtor(page);
        tlb_remove_table(tlb, page);
}

#if CONFIG_PGTABLE_LEVELS > 3
void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
{
        paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
        tlb_remove_table(tlb, virt_to_page(pud));
}

#if CONFIG_PGTABLE_LEVELS > 4
void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d)
{
        paravirt_release_p4d(__pa(p4d) >> PAGE_SHIFT);
        tlb_remove_table(tlb, virt_to_page(p4d));
}
#endif  /* CONFIG_PGTABLE_LEVELS > 4 */
#endif  /* CONFIG_PGTABLE_LEVELS > 3 */
#endif  /* CONFIG_PGTABLE_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 (CONFIG_PGTABLE_LEVELS == 2 ||
            (CONFIG_PGTABLE_LEVELS == 3 && SHARED_KERNEL_PMD) ||
            CONFIG_PGTABLE_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.
 * -- nyc
 */

#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(struct mm_struct *mm, pmd_t *pmds[])
{
        int i;

        for(i = 0; i < PREALLOCATED_PMDS; i++)
                if (pmds[i]) {
                        pgtable_pmd_page_dtor(virt_to_page(pmds[i]));
                        free_page((unsigned long)pmds[i]);
                        mm_dec_nr_pmds(mm);
                }
}

static int preallocate_pmds(struct mm_struct *mm, pmd_t *pmds[])
{
        int i;
        bool failed = false;
        gfp_t gfp = PGALLOC_GFP;

        if (mm == &init_mm)
                gfp &= ~__GFP_ACCOUNT;

        for(i = 0; i < PREALLOCATED_PMDS; i++) {
                pmd_t *pmd = (pmd_t *)__get_free_page(gfp);
                if (!pmd)
                        failed = true;
                if (pmd && !pgtable_pmd_page_ctor(virt_to_page(pmd))) {
                        free_page((unsigned long)pmd);
                        pmd = NULL;
                        failed = true;
                }
                if (pmd)
                        mm_inc_nr_pmds(mm);
                pmds[i] = pmd;
        }

        if (failed) {
                free_pmds(mm, 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);
                        mm_dec_nr_pmds(mm);
                }
        }
}

static void pgd_prepopulate_pmd(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmds[])
{
        p4d_t *p4d;
        pud_t *pud;
        int i;

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

        p4d = p4d_offset(pgd, 0);
        pud = pud_offset(p4d, 0);

        for (i = 0; i < PREALLOCATED_PMDS; i++, pud++) {
                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);
        }
}

/*
 * Xen paravirt assumes pgd table should be in one page. 64 bit kernel also
 * assumes that pgd should be in one page.
 *
 * But kernel with PAE paging that is not running as a Xen domain
 * only needs to allocate 32 bytes for pgd instead of one page.
 */
#ifdef CONFIG_X86_PAE

#include <linux/slab.h>

#define PGD_SIZE        (PTRS_PER_PGD * sizeof(pgd_t))
#define PGD_ALIGN       32

static struct kmem_cache *pgd_cache;

static int __init pgd_cache_init(void)
{
        /*
         * When PAE kernel is running as a Xen domain, it does not use
         * shared kernel pmd. And this requires a whole page for pgd.
         */
        if (!SHARED_KERNEL_PMD)
                return 0;

        /*
         * when PAE kernel is not running as a Xen domain, it uses
         * shared kernel pmd. Shared kernel pmd does not require a whole
         * page for pgd. We are able to just allocate a 32-byte for pgd.
         * During boot time, we create a 32-byte slab for pgd table allocation.
         */
        pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_ALIGN,
                                      SLAB_PANIC, NULL);
        if (!pgd_cache)
                return -ENOMEM;

        return 0;
}
core_initcall(pgd_cache_init);

static inline pgd_t *_pgd_alloc(void)
{
        /*
         * If no SHARED_KERNEL_PMD, PAE kernel is running as a Xen domain.
         * We allocate one page for pgd.
         */
        if (!SHARED_KERNEL_PMD)
                return (pgd_t *)__get_free_page(PGALLOC_GFP);

        /*
         * Now PAE kernel is not running as a Xen domain. We can allocate
         * a 32-byte slab for pgd to save memory space.
         */
        return kmem_cache_alloc(pgd_cache, PGALLOC_GFP);
}

static inline void _pgd_free(pgd_t *pgd)
{
        if (!SHARED_KERNEL_PMD)
                free_page((unsigned long)pgd);
        else
                kmem_cache_free(pgd_cache, pgd);
}
#else

static inline pgd_t *_pgd_alloc(void)
{
        return (pgd_t *)__get_free_pages(PGALLOC_GFP, PGD_ALLOCATION_ORDER);
}

static inline void _pgd_free(pgd_t *pgd)
{
        free_pages((unsigned long)pgd, PGD_ALLOCATION_ORDER);
}
#endif /* CONFIG_X86_PAE */

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

        pgd = _pgd_alloc();

        if (pgd == NULL)
                goto out;

        mm->pgd = pgd;

        if (preallocate_pmds(mm, 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(mm, pmds);
out_free_pgd:
        _pgd_free(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);
        _pgd_free(pgd);
}

/*
 * Used to set accessed or dirty bits in the page table entries
 * on other architectures. On x86, the accessed and dirty bits
 * are tracked by hardware. However, do_wp_page calls this function
 * to also make the pte writeable at the same time the dirty bit is
 * set. In that case we do actually need to write the PTE.
 */
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;

        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;
                /*
                 * We had a write-protection fault here and changed the pmd
                 * to to more permissive. No need to flush the TLB for that,
                 * #PF is architecturally guaranteed to do that and in the
                 * worst-case we'll generate a spurious fault.
                 */
        }

        return changed;
}

int pudp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
                          pud_t *pudp, pud_t entry, int dirty)
{
        int changed = !pud_same(*pudp, entry);

        VM_BUG_ON(address & ~HPAGE_PUD_MASK);

        if (changed && dirty) {
                *pudp = entry;
                /*
                 * We had a write-protection fault here and changed the pud
                 * to to more permissive. No need to flush the TLB for that,
                 * #PF is architecturally guaranteed to do that and in the
                 * worst-case we'll generate a spurious fault.
                 */
        }

        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);

        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);

        return ret;
}
int pudp_test_and_clear_young(struct vm_area_struct *vma,
                              unsigned long addr, pud_t *pudp)
{
        int ret = 0;

        if (pud_young(*pudp))
                ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
                                         (unsigned long *)pudp);

        return ret;
}
#endif

int ptep_clear_flush_young(struct vm_area_struct *vma,
                           unsigned long address, pte_t *ptep)
{
        /*
         * On x86 CPUs, clearing the accessed bit without a TLB flush
         * doesn't cause data corruption. [ It could cause incorrect
         * page aging and the (mistaken) reclaim of hot pages, but the
         * chance of that should be relatively low. ]
         *
         * So as a performance optimization don't flush the TLB when
         * clearing the accessed bit, it will eventually be flushed by
         * a context switch or a VM operation anyway. [ In the rare
         * event of it not getting flushed for a long time the delay
         * shouldn't really matter because there's no real memory
         * pressure for swapout to react to. ]
         */
        return ptep_test_and_clear_young(vma, address, ptep);
}

#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;
}
#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);
        __FIXADDR_TOP = round_down(-reserve, 1 << PMD_SHIFT) - PAGE_SIZE;
        printk(KERN_INFO "Reserving virtual address space above 0x%08lx (rounded to 0x%08lx)\n",
               -reserve, __FIXADDR_TOP + 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));
}

#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
#ifdef CONFIG_X86_5LEVEL
/**
 * p4d_set_huge - setup kernel P4D mapping
 *
 * No 512GB pages yet -- always return 0
 */
int p4d_set_huge(p4d_t *p4d, phys_addr_t addr, pgprot_t prot)
{
        return 0;
}

/**
 * p4d_clear_huge - clear kernel P4D mapping when it is set
 *
 * No 512GB pages yet -- always return 0
 */
int p4d_clear_huge(p4d_t *p4d)
{
        return 0;
}
#endif

/**
 * pud_set_huge - setup kernel PUD mapping
 *
 * MTRRs can override PAT memory types with 4KiB granularity. Therefore, this
 * function sets up a huge page only if any of the following conditions are met:
 *
 * - MTRRs are disabled, or
 *
 * - MTRRs are enabled and the range is completely covered by a single MTRR, or
 *
 * - MTRRs are enabled and the corresponding MTRR memory type is WB, which
 *   has no effect on the requested PAT memory type.
 *
 * Callers should try to decrease page size (1GB -> 2MB -> 4K) if the bigger
 * page mapping attempt fails.
 *
 * Returns 1 on success and 0 on failure.
 */
int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
{
        u8 mtrr, uniform;

        mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE, &uniform);
        if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) &&
            (mtrr != MTRR_TYPE_WRBACK))
                return 0;

        prot = pgprot_4k_2_large(prot);

        set_pte((pte_t *)pud, pfn_pte(
                (u64)addr >> PAGE_SHIFT,
                __pgprot(pgprot_val(prot) | _PAGE_PSE)));

        return 1;
}

/**
 * pmd_set_huge - setup kernel PMD mapping
 *
 * See text over pud_set_huge() above.
 *
 * Returns 1 on success and 0 on failure.
 */
int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
{
        u8 mtrr, uniform;

        mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE, &uniform);
        if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) &&
            (mtrr != MTRR_TYPE_WRBACK)) {
                pr_warn_once("%s: Cannot satisfy [mem %#010llx-%#010llx] with a huge-page mapping due to MTRR override.\n",
                             __func__, addr, addr + PMD_SIZE);
                return 0;
        }

        prot = pgprot_4k_2_large(prot);

        set_pte((pte_t *)pmd, pfn_pte(
                (u64)addr >> PAGE_SHIFT,
                __pgprot(pgprot_val(prot) | _PAGE_PSE)));

        return 1;
}

/**
 * pud_clear_huge - clear kernel PUD mapping when it is set
 *
 * Returns 1 on success and 0 on failure (no PUD map is found).
 */
int pud_clear_huge(pud_t *pud)
{
        if (pud_large(*pud)) {
                pud_clear(pud);
                return 1;
        }

        return 0;
}

/**
 * pmd_clear_huge - clear kernel PMD mapping when it is set
 *
 * Returns 1 on success and 0 on failure (no PMD map is found).
 */
int pmd_clear_huge(pmd_t *pmd)
{
        if (pmd_large(*pmd)) {
                pmd_clear(pmd);
                return 1;
        }

        return 0;
}
#endif  /* CONFIG_HAVE_ARCH_HUGE_VMAP */