The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d1874a0c2805fcfa9162c972d6b7541e57adb542 Mon Sep 17 00:00:00 2001

From: Martin Schwidefsky schwidefsky@de.ibm.com Date: Tue, 23 Apr 2019 10:51:12 +0200 Subject: [PATCH] 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: Martin Schwidefsky schwidefsky@de.ibm.com

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 76dc344edb8c..d48be9c27df9 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -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; diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c index 2809d11c7a28..a5ffcb132191 100644 --- a/arch/s390/mm/gup.c +++ b/arch/s390/mm/gup.c @@ -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);