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s390/mm: make the pxd_offset functions more robust
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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: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Martin Schwidefsky committed Apr 23, 2019
1 parent 6bcf74e commit d1874a0
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Showing 2 changed files with 55 additions and 45 deletions.
67 changes: 43 additions & 24 deletions arch/s390/include/asm/pgtable.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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))
Expand All @@ -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;
Expand Down
33 changes: 12 additions & 21 deletions arch/s390/mm/gup.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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();
Expand Down Expand Up @@ -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();
Expand All @@ -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);
Expand Down Expand Up @@ -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();
Expand All @@ -186,31 +180,28 @@ 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);

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);

Expand Down Expand Up @@ -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);
Expand Down

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