Commit d1874a0c authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390/mm: make the pxd_offset functions more robust 



Change the way how pgd_offset, p4d_offset, pud_offset and pmd_offset
walk the page tables. pgd_offset now always calculates the index for
the top-level page table and adds it to the pgd, this is either a
segment table offset for a 2-level setup, a region-3 offset for 3-levels,
region-2 offset for 4-levels, or a region-1 offset for a 5-level setup.
The other three functions p4d_offset, pud_offset and pmd_offset will
only add the respective offset if they dereference the passed pointer.

With the new way of walking the page tables a sequence like this from
mm/gup.c now works:

     pgdp = pgd_offset(current->mm, addr);
     pgd = READ_ONCE(*pgdp);
     p4dp = p4d_offset(&pgd, addr);
     p4d = READ_ONCE(*p4dp);
     pudp = pud_offset(&p4d, addr);
     pud = READ_ONCE(*pudp);
     pmdp = pmd_offset(&pud, addr);
     pmd = READ_ONCE(*pmdp);

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 6bcf74e2

arch/s390/include/asm/pgtable.h

+43 −24
Original line number Diff line number Diff line
@@ -1204,42 +1204,67 @@ static inline pte_t mk_pte(struct page *page, pgprot_t pgprot) 
#define pmd_index(address) (((address) >> PMD_SHIFT) & (PTRS_PER_PMD-1))

#define pte_index(address) (((address) >> PAGE_SHIFT) & (PTRS_PER_PTE-1))



#define pgd_offset(mm, address) ((mm)->pgd + pgd_index(address))

#define pgd_offset_k(address) pgd_offset(&init_mm, address)

#define pgd_offset_raw(pgd, addr) ((pgd) + pgd_index(addr))



#define pmd_deref(pmd) (pmd_val(pmd) & _SEGMENT_ENTRY_ORIGIN)

#define pud_deref(pud) (pud_val(pud) & _REGION_ENTRY_ORIGIN)

#define p4d_deref(pud) (p4d_val(pud) & _REGION_ENTRY_ORIGIN)

#define pgd_deref(pgd) (pgd_val(pgd) & _REGION_ENTRY_ORIGIN)



static inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long address)

/*

 * The pgd_offset function *always* adds the index for the top-level

 * region/segment table. This is done to get a sequence like the

 * following to work:

 *	pgdp = pgd_offset(current->mm, addr);

 *	pgd = READ_ONCE(*pgdp);

 *	p4dp = p4d_offset(&pgd, addr);

 *	...

 * The subsequent p4d_offset, pud_offset and pmd_offset functions

 * only add an index if they dereferenced the pointer.

 */

static inline pgd_t *pgd_offset_raw(pgd_t *pgd, unsigned long address)

{

	p4d_t *p4d = (p4d_t *) pgd;

	unsigned long rste;

	unsigned int shift;



	if ((pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R1)

		p4d = (p4d_t *) pgd_deref(*pgd);

	return p4d + p4d_index(address);

	/* Get the first entry of the top level table */

	rste = pgd_val(*pgd);

	/* Pick up the shift from the table type of the first entry */

	shift = ((rste & _REGION_ENTRY_TYPE_MASK) >> 2) * 11 + 20;

	return pgd + ((address >> shift) & (PTRS_PER_PGD - 1));

}



static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)

#define pgd_offset(mm, address) pgd_offset_raw(READ_ONCE((mm)->pgd), address)

#define pgd_offset_k(address) pgd_offset(&init_mm, address)



static inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long address)

{

	pud_t *pud = (pud_t *) p4d;

	if ((pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) >= _REGION_ENTRY_TYPE_R1)

		return (p4d_t *) pgd_deref(*pgd) + p4d_index(address);

	return (p4d_t *) pgd;

}



	if ((p4d_val(*p4d) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2)

		pud = (pud_t *) p4d_deref(*p4d);

	return pud + pud_index(address);

static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)

{

	if ((p4d_val(*p4d) & _REGION_ENTRY_TYPE_MASK) >= _REGION_ENTRY_TYPE_R2)

		return (pud_t *) p4d_deref(*p4d) + pud_index(address);

	return (pud_t *) p4d;

}



static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)

{

	pmd_t *pmd = (pmd_t *) pud;

	if ((pud_val(*pud) & _REGION_ENTRY_TYPE_MASK) >= _REGION_ENTRY_TYPE_R3)

		return (pmd_t *) pud_deref(*pud) + pmd_index(address);

	return (pmd_t *) pud;

}



	if ((pud_val(*pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)

		pmd = (pmd_t *) pud_deref(*pud);

	return pmd + pmd_index(address);

static inline pte_t *pte_offset(pmd_t *pmd, unsigned long address)

{

	return (pte_t *) pmd_deref(*pmd) + pte_index(address);

}



#define pte_offset_kernel(pmd, address) pte_offset(pmd, address)

#define pte_offset_map(pmd, address) pte_offset_kernel(pmd, address)

#define pte_unmap(pte) do { } while (0)



#define pfn_pte(pfn,pgprot) mk_pte_phys(__pa((pfn) << PAGE_SHIFT),(pgprot))

#define pte_pfn(x) (pte_val(x) >> PAGE_SHIFT)

#define pte_page(x) pfn_to_page(pte_pfn(x))
@@ -1249,12 +1274,6 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address) 
#define p4d_page(p4d) pfn_to_page(p4d_pfn(p4d))

#define pgd_page(pgd) pfn_to_page(pgd_pfn(pgd))



/* Find an entry in the lowest level page table.. */

#define pte_offset(pmd, addr) ((pte_t *) pmd_deref(*(pmd)) + pte_index(addr))

#define pte_offset_kernel(pmd, address) pte_offset(pmd,address)

#define pte_offset_map(pmd, address) pte_offset_kernel(pmd, address)

#define pte_unmap(pte) do { } while (0)



static inline pmd_t pmd_wrprotect(pmd_t pmd)

{

	pmd_val(pmd) &= ~_SEGMENT_ENTRY_WRITE;

arch/s390/mm/gup.c

+12 −21
Original line number Diff line number Diff line
@@ -18,7 +18,7 @@ 
 * inlines everything into a single function which results in too much

 * register pressure.

 */

static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,

static inline int gup_pte_range(pmd_t pmd, unsigned long addr,

		unsigned long end, int write, struct page **pages, int *nr)

{

	struct page *head, *page;
@@ -27,7 +27,7 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, 


	mask = (write ? _PAGE_PROTECT : 0) | _PAGE_INVALID | _PAGE_SPECIAL;



	ptep = ((pte_t *) pmd_deref(pmd)) + pte_index(addr);

	ptep = pte_offset_map(&pmd, addr);

	do {

		pte = *ptep;

		barrier();
@@ -93,16 +93,13 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, 
}





static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,

static inline int gup_pmd_range(pud_t pud, unsigned long addr,

		unsigned long end, int write, struct page **pages, int *nr)

{

	unsigned long next;

	pmd_t *pmdp, pmd;



	pmdp = (pmd_t *) pudp;

	if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)

		pmdp = (pmd_t *) pud_deref(pud);

	pmdp += pmd_index(addr);

	pmdp = pmd_offset(&pud, addr);

	do {

		pmd = *pmdp;

		barrier();
@@ -120,7 +117,7 @@ static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, 
			if (!gup_huge_pmd(pmdp, pmd, addr, next,

					  write, pages, nr))

				return 0;

		} else if (!gup_pte_range(pmdp, pmd, addr, next,

		} else if (!gup_pte_range(pmd, addr, next,

					  write, pages, nr))

			return 0;

	} while (pmdp++, addr = next, addr != end);
@@ -166,16 +163,13 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr, 
	return 1;

}



static inline int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr,

static inline int gup_pud_range(p4d_t p4d, unsigned long addr,

		unsigned long end, int write, struct page **pages, int *nr)

{

	unsigned long next;

	pud_t *pudp, pud;



	pudp = (pud_t *) p4dp;

	if ((p4d_val(p4d) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2)

		pudp = (pud_t *) p4d_deref(p4d);

	pudp += pud_index(addr);

	pudp = pud_offset(&p4d, addr);

	do {

		pud = *pudp;

		barrier();
@@ -186,7 +180,7 @@ static inline int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, 
			if (!gup_huge_pud(pudp, pud, addr, next, write, pages,

					  nr))

				return 0;

		} else if (!gup_pmd_range(pudp, pud, addr, next, write, pages,

		} else if (!gup_pmd_range(pud, addr, next, write, pages,

					  nr))

			return 0;

	} while (pudp++, addr = next, addr != end);
@@ -194,23 +188,20 @@ static inline int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, 
	return 1;

}



static inline int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,

static inline int gup_p4d_range(pgd_t pgd, unsigned long addr,

		unsigned long end, int write, struct page **pages, int *nr)

{

	unsigned long next;

	p4d_t *p4dp, p4d;



	p4dp = (p4d_t *) pgdp;

	if ((pgd_val(pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R1)

		p4dp = (p4d_t *) pgd_deref(pgd);

	p4dp += p4d_index(addr);

	p4dp = p4d_offset(&pgd, addr);

	do {

		p4d = *p4dp;

		barrier();

		next = p4d_addr_end(addr, end);

		if (p4d_none(p4d))

			return 0;

		if (!gup_pud_range(p4dp, p4d, addr, next, write, pages, nr))

		if (!gup_pud_range(p4d, addr, next, write, pages, nr))

			return 0;

	} while (p4dp++, addr = next, addr != end);
@@ -253,7 +244,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, 
		next = pgd_addr_end(addr, end);

		if (pgd_none(pgd))

			break;

		if (!gup_p4d_range(pgdp, pgd, addr, next, write, pages, &nr))

		if (!gup_p4d_range(pgd, addr, next, write, pages, &nr))

			break;

	} while (pgdp++, addr = next, addr != end);

	local_irq_restore(flags);

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