From be1db4753ee6a0db80a900df9dbbf6ad2acc4bd1 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Tue, 17 Dec 2019 20:51:41 -0800 Subject: [PATCH] mm/memory.c: add apply_to_existing_page_range() helper apply_to_page_range() takes an address range, and if any parts of it are not covered by the existing page table hierarchy, it allocates memory to fill them in. In some use cases, this is not what we want - we want to be able to operate exclusively on PTEs that are already in the tables. Add apply_to_existing_page_range() for this. Adjust the walker functions for apply_to_page_range to take 'create', which switches them between the old and new modes. This will be used in KASAN vmalloc. [akpm@linux-foundation.org: reduce code duplication] [akpm@linux-foundation.org: s/apply_to_existing_pages/apply_to_existing_page_range/] [akpm@linux-foundation.org: initialize __apply_to_page_range::err] Link: http://lkml.kernel.org/r/20191205140407.1874-1-dja@axtens.net Signed-off-by: Daniel Axtens Cc: Dmitry Vyukov Cc: Uladzislau Rezki (Sony) Cc: Alexander Potapenko Cc: Daniel Axtens Cc: Qian Cai Cc: Andrey Ryabinin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 3 + mm/memory.c | 152 ++++++++++++++++++++++++++++++--------------- 2 files changed, 105 insertions(+), 50 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index c97ea3b694e6..80a9162b406c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2621,6 +2621,9 @@ static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags) typedef int (*pte_fn_t)(pte_t *pte, unsigned long addr, void *data); extern int apply_to_page_range(struct mm_struct *mm, unsigned long address, unsigned long size, pte_fn_t fn, void *data); +extern int apply_to_existing_page_range(struct mm_struct *mm, + unsigned long address, unsigned long size, + pte_fn_t fn, void *data); #ifdef CONFIG_PAGE_POISONING extern bool page_poisoning_enabled(void); diff --git a/mm/memory.c b/mm/memory.c index 606da187d1de..45442d9a4f52 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2021,26 +2021,34 @@ EXPORT_SYMBOL(vm_iomap_memory); static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd, unsigned long addr, unsigned long end, - pte_fn_t fn, void *data) + pte_fn_t fn, void *data, bool create) { pte_t *pte; - int err; + int err = 0; spinlock_t *uninitialized_var(ptl); - pte = (mm == &init_mm) ? - pte_alloc_kernel(pmd, addr) : - pte_alloc_map_lock(mm, pmd, addr, &ptl); - if (!pte) - return -ENOMEM; + if (create) { + pte = (mm == &init_mm) ? + pte_alloc_kernel(pmd, addr) : + pte_alloc_map_lock(mm, pmd, addr, &ptl); + if (!pte) + return -ENOMEM; + } else { + pte = (mm == &init_mm) ? + pte_offset_kernel(pmd, addr) : + pte_offset_map_lock(mm, pmd, addr, &ptl); + } BUG_ON(pmd_huge(*pmd)); arch_enter_lazy_mmu_mode(); do { - err = fn(pte++, addr, data); - if (err) - break; + if (create || !pte_none(*pte)) { + err = fn(pte++, addr, data); + if (err) + break; + } } while (addr += PAGE_SIZE, addr != end); arch_leave_lazy_mmu_mode(); @@ -2052,63 +2060,109 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd, static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud, unsigned long addr, unsigned long end, - pte_fn_t fn, void *data) + pte_fn_t fn, void *data, bool create) { pmd_t *pmd; unsigned long next; - int err; + int err = 0; BUG_ON(pud_huge(*pud)); - pmd = pmd_alloc(mm, pud, addr); - if (!pmd) - return -ENOMEM; + if (create) { + pmd = pmd_alloc(mm, pud, addr); + if (!pmd) + return -ENOMEM; + } else { + pmd = pmd_offset(pud, addr); + } do { next = pmd_addr_end(addr, end); - err = apply_to_pte_range(mm, pmd, addr, next, fn, data); - if (err) - break; + if (create || !pmd_none_or_clear_bad(pmd)) { + err = apply_to_pte_range(mm, pmd, addr, next, fn, data, + create); + if (err) + break; + } } while (pmd++, addr = next, addr != end); return err; } static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d, unsigned long addr, unsigned long end, - pte_fn_t fn, void *data) + pte_fn_t fn, void *data, bool create) { pud_t *pud; unsigned long next; - int err; + int err = 0; - pud = pud_alloc(mm, p4d, addr); - if (!pud) - return -ENOMEM; + if (create) { + pud = pud_alloc(mm, p4d, addr); + if (!pud) + return -ENOMEM; + } else { + pud = pud_offset(p4d, addr); + } do { next = pud_addr_end(addr, end); - err = apply_to_pmd_range(mm, pud, addr, next, fn, data); - if (err) - break; + if (create || !pud_none_or_clear_bad(pud)) { + err = apply_to_pmd_range(mm, pud, addr, next, fn, data, + create); + if (err) + break; + } } while (pud++, addr = next, addr != end); return err; } static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd, unsigned long addr, unsigned long end, - pte_fn_t fn, void *data) + pte_fn_t fn, void *data, bool create) { p4d_t *p4d; unsigned long next; - int err; + int err = 0; - p4d = p4d_alloc(mm, pgd, addr); - if (!p4d) - return -ENOMEM; + if (create) { + p4d = p4d_alloc(mm, pgd, addr); + if (!p4d) + return -ENOMEM; + } else { + p4d = p4d_offset(pgd, addr); + } do { next = p4d_addr_end(addr, end); - err = apply_to_pud_range(mm, p4d, addr, next, fn, data); + if (create || !p4d_none_or_clear_bad(p4d)) { + err = apply_to_pud_range(mm, p4d, addr, next, fn, data, + create); + if (err) + break; + } + } while (p4d++, addr = next, addr != end); + return err; +} + +static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr, + unsigned long size, pte_fn_t fn, + void *data, bool create) +{ + pgd_t *pgd; + unsigned long next; + unsigned long end = addr + size; + int err = 0; + + if (WARN_ON(addr >= end)) + return -EINVAL; + + pgd = pgd_offset(mm, addr); + do { + next = pgd_addr_end(addr, end); + if (!create && pgd_none_or_clear_bad(pgd)) + continue; + err = apply_to_p4d_range(mm, pgd, addr, next, fn, data, create); if (err) break; - } while (p4d++, addr = next, addr != end); + } while (pgd++, addr = next, addr != end); + return err; } @@ -2119,26 +2173,24 @@ static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd, int apply_to_page_range(struct mm_struct *mm, unsigned long addr, unsigned long size, pte_fn_t fn, void *data) { - pgd_t *pgd; - unsigned long next; - unsigned long end = addr + size; - int err; - - if (WARN_ON(addr >= end)) - return -EINVAL; - - pgd = pgd_offset(mm, addr); - do { - next = pgd_addr_end(addr, end); - err = apply_to_p4d_range(mm, pgd, addr, next, fn, data); - if (err) - break; - } while (pgd++, addr = next, addr != end); - - return err; + return __apply_to_page_range(mm, addr, size, fn, data, true); } EXPORT_SYMBOL_GPL(apply_to_page_range); +/* + * Scan a region of virtual memory, calling a provided function on + * each leaf page table where it exists. + * + * Unlike apply_to_page_range, this does _not_ fill in page tables + * where they are absent. + */ +int apply_to_existing_page_range(struct mm_struct *mm, unsigned long addr, + unsigned long size, pte_fn_t fn, void *data) +{ + return __apply_to_page_range(mm, addr, size, fn, data, false); +} +EXPORT_SYMBOL_GPL(apply_to_existing_page_range); + /* * handle_pte_fault chooses page fault handler according to an entry which was * read non-atomically. Before making any commitment, on those architectures