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hugetlbpage.c

/*
 *  IBM System z Huge TLB Page Support for Kernel.
 *
 *    Copyright 2007 IBM Corp.
 *    Author(s): Gerald Schaefer <gerald.schaefer@de.ibm.com>
 */

#include <linux/mm.h>
#include <linux/hugetlb.h>


void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
                           pte_t *pteptr, pte_t pteval)
{
      pmd_t *pmdp = (pmd_t *) pteptr;
      pte_t shadow_pteval = pteval;
      unsigned long mask;

      if (!MACHINE_HAS_HPAGE) {
            pteptr = (pte_t *) pte_page(pteval)[1].index;
            mask = pte_val(pteval) &
                        (_SEGMENT_ENTRY_INV | _SEGMENT_ENTRY_RO);
            pte_val(pteval) = (_SEGMENT_ENTRY + __pa(pteptr)) | mask;
            if (mm->context.noexec) {
                  pteptr += PTRS_PER_PTE;
                  pte_val(shadow_pteval) =
                              (_SEGMENT_ENTRY + __pa(pteptr)) | mask;
            }
      }

      pmd_val(*pmdp) = pte_val(pteval);
      if (mm->context.noexec) {
            pmdp = get_shadow_table(pmdp);
            pmd_val(*pmdp) = pte_val(shadow_pteval);
      }
}

int arch_prepare_hugepage(struct page *page)
{
      unsigned long addr = page_to_phys(page);
      pte_t pte;
      pte_t *ptep;
      int i;

      if (MACHINE_HAS_HPAGE)
            return 0;

      ptep = (pte_t *) pte_alloc_one(&init_mm, address);
      if (!ptep)
            return -ENOMEM;

      pte = mk_pte(page, PAGE_RW);
      for (i = 0; i < PTRS_PER_PTE; i++) {
            set_pte_at(&init_mm, addr + i * PAGE_SIZE, ptep + i, pte);
            pte_val(pte) += PAGE_SIZE;
      }
      page[1].index = (unsigned long) ptep;
      return 0;
}

void arch_release_hugepage(struct page *page)
{
      pte_t *ptep;

      if (MACHINE_HAS_HPAGE)
            return;

      ptep = (pte_t *) page[1].index;
      if (!ptep)
            return;
      pte_free(&init_mm, ptep);
      page[1].index = 0;
}

pte_t *huge_pte_alloc(struct mm_struct *mm,
                  unsigned long addr, unsigned long sz)
{
      pgd_t *pgdp;
      pud_t *pudp;
      pmd_t *pmdp = NULL;

      pgdp = pgd_offset(mm, addr);
      pudp = pud_alloc(mm, pgdp, addr);
      if (pudp)
            pmdp = pmd_alloc(mm, pudp, addr);
      return (pte_t *) pmdp;
}

pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
      pgd_t *pgdp;
      pud_t *pudp;
      pmd_t *pmdp = NULL;

      pgdp = pgd_offset(mm, addr);
      if (pgd_present(*pgdp)) {
            pudp = pud_offset(pgdp, addr);
            if (pud_present(*pudp))
                  pmdp = pmd_offset(pudp, addr);
      }
      return (pte_t *) pmdp;
}

int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
{
      return 0;
}

struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
                        int write)
{
      return ERR_PTR(-EINVAL);
}

int pmd_huge(pmd_t pmd)
{
      if (!MACHINE_HAS_HPAGE)
            return 0;

      return !!(pmd_val(pmd) & _SEGMENT_ENTRY_LARGE);
}

int pud_huge(pud_t pud)
{
      return 0;
}

struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
                       pmd_t *pmdp, int write)
{
      struct page *page;

      if (!MACHINE_HAS_HPAGE)
            return NULL;

      page = pmd_page(*pmdp);
      if (page)
            page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
      return page;
}

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