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Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 6018 |
1 files changed, 6018 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c new file mode 100644 index 000000000..fc8b264ec --- /dev/null +++ b/mm/memory.c @@ -0,0 +1,6018 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/mm/memory.c + * + * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds + */ + +/* + * demand-loading started 01.12.91 - seems it is high on the list of + * things wanted, and it should be easy to implement. - Linus + */ + +/* + * Ok, demand-loading was easy, shared pages a little bit tricker. Shared + * pages started 02.12.91, seems to work. - Linus. + * + * Tested sharing by executing about 30 /bin/sh: under the old kernel it + * would have taken more than the 6M I have free, but it worked well as + * far as I could see. + * + * Also corrected some "invalidate()"s - I wasn't doing enough of them. + */ + +/* + * Real VM (paging to/from disk) started 18.12.91. Much more work and + * thought has to go into this. Oh, well.. + * 19.12.91 - works, somewhat. Sometimes I get faults, don't know why. + * Found it. Everything seems to work now. + * 20.12.91 - Ok, making the swap-device changeable like the root. + */ + +/* + * 05.04.94 - Multi-page memory management added for v1.1. + * Idea by Alex Bligh (alex@cconcepts.co.uk) + * + * 16.07.99 - Support of BIGMEM added by Gerhard Wichert, Siemens AG + * (Gerhard.Wichert@pdb.siemens.de) + * + * Aug/Sep 2004 Changed to four level page tables (Andi Kleen) + */ + +#include <linux/kernel_stat.h> +#include <linux/mm.h> +#include <linux/mm_inline.h> +#include <linux/sched/mm.h> +#include <linux/sched/coredump.h> +#include <linux/sched/numa_balancing.h> +#include <linux/sched/task.h> +#include <linux/hugetlb.h> +#include <linux/mman.h> +#include <linux/swap.h> +#include <linux/highmem.h> +#include <linux/pagemap.h> +#include <linux/memremap.h> +#include <linux/kmsan.h> +#include <linux/ksm.h> +#include <linux/rmap.h> +#include <linux/export.h> +#include <linux/delayacct.h> +#include <linux/init.h> +#include <linux/pfn_t.h> +#include <linux/writeback.h> +#include <linux/memcontrol.h> +#include <linux/mmu_notifier.h> +#include <linux/swapops.h> +#include <linux/elf.h> +#include <linux/gfp.h> +#include <linux/migrate.h> +#include <linux/string.h> +#include <linux/memory-tiers.h> +#include <linux/debugfs.h> +#include <linux/userfaultfd_k.h> +#include <linux/dax.h> +#include <linux/oom.h> +#include <linux/numa.h> +#include <linux/perf_event.h> +#include <linux/ptrace.h> +#include <linux/vmalloc.h> +#include <linux/sched/sysctl.h> + +#include <trace/events/kmem.h> + +#include <asm/io.h> +#include <asm/mmu_context.h> +#include <asm/pgalloc.h> +#include <linux/uaccess.h> +#include <asm/tlb.h> +#include <asm/tlbflush.h> + +#include "pgalloc-track.h" +#include "internal.h" +#include "swap.h" + +#if defined(LAST_CPUPID_NOT_IN_PAGE_FLAGS) && !defined(CONFIG_COMPILE_TEST) +#warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid. +#endif + +#ifndef CONFIG_NUMA +unsigned long max_mapnr; +EXPORT_SYMBOL(max_mapnr); + +struct page *mem_map; +EXPORT_SYMBOL(mem_map); +#endif + +static vm_fault_t do_fault(struct vm_fault *vmf); + +/* + * A number of key systems in x86 including ioremap() rely on the assumption + * that high_memory defines the upper bound on direct map memory, then end + * of ZONE_NORMAL. Under CONFIG_DISCONTIG this means that max_low_pfn and + * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL + * and ZONE_HIGHMEM. + */ +void *high_memory; +EXPORT_SYMBOL(high_memory); + +/* + * Randomize the address space (stacks, mmaps, brk, etc.). + * + * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization, + * as ancient (libc5 based) binaries can segfault. ) + */ +int randomize_va_space __read_mostly = +#ifdef CONFIG_COMPAT_BRK + 1; +#else + 2; +#endif + +#ifndef arch_wants_old_prefaulted_pte +static inline bool arch_wants_old_prefaulted_pte(void) +{ + /* + * Transitioning a PTE from 'old' to 'young' can be expensive on + * some architectures, even if it's performed in hardware. By + * default, "false" means prefaulted entries will be 'young'. + */ + return false; +} +#endif + +static int __init disable_randmaps(char *s) +{ + randomize_va_space = 0; + return 1; +} +__setup("norandmaps", disable_randmaps); + +unsigned long zero_pfn __read_mostly; +EXPORT_SYMBOL(zero_pfn); + +unsigned long highest_memmap_pfn __read_mostly; + +/* + * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init() + */ +static int __init init_zero_pfn(void) +{ + zero_pfn = page_to_pfn(ZERO_PAGE(0)); + return 0; +} +early_initcall(init_zero_pfn); + +void mm_trace_rss_stat(struct mm_struct *mm, int member, long count) +{ + trace_rss_stat(mm, member, count); +} + +#if defined(SPLIT_RSS_COUNTING) + +void sync_mm_rss(struct mm_struct *mm) +{ + int i; + + for (i = 0; i < NR_MM_COUNTERS; i++) { + if (current->rss_stat.count[i]) { + add_mm_counter(mm, i, current->rss_stat.count[i]); + current->rss_stat.count[i] = 0; + } + } + current->rss_stat.events = 0; +} + +static void add_mm_counter_fast(struct mm_struct *mm, int member, int val) +{ + struct task_struct *task = current; + + if (likely(task->mm == mm)) + task->rss_stat.count[member] += val; + else + add_mm_counter(mm, member, val); +} +#define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1) +#define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1) + +/* sync counter once per 64 page faults */ +#define TASK_RSS_EVENTS_THRESH (64) +static void check_sync_rss_stat(struct task_struct *task) +{ + if (unlikely(task != current)) + return; + if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH)) + sync_mm_rss(task->mm); +} +#else /* SPLIT_RSS_COUNTING */ + +#define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member) +#define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member) + +static void check_sync_rss_stat(struct task_struct *task) +{ +} + +#endif /* SPLIT_RSS_COUNTING */ + +/* + * Note: this doesn't free the actual pages themselves. That + * has been handled earlier when unmapping all the memory regions. + */ +static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd, + unsigned long addr) +{ + pgtable_t token = pmd_pgtable(*pmd); + pmd_clear(pmd); + pte_free_tlb(tlb, token, addr); + mm_dec_nr_ptes(tlb->mm); +} + +static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud, + unsigned long addr, unsigned long end, + unsigned long floor, unsigned long ceiling) +{ + pmd_t *pmd; + unsigned long next; + unsigned long start; + + start = addr; + pmd = pmd_offset(pud, addr); + do { + next = pmd_addr_end(addr, end); + if (pmd_none_or_clear_bad(pmd)) + continue; + free_pte_range(tlb, pmd, addr); + } while (pmd++, addr = next, addr != end); + + start &= PUD_MASK; + if (start < floor) + return; + if (ceiling) { + ceiling &= PUD_MASK; + if (!ceiling) + return; + } + if (end - 1 > ceiling - 1) + return; + + pmd = pmd_offset(pud, start); + pud_clear(pud); + pmd_free_tlb(tlb, pmd, start); + mm_dec_nr_pmds(tlb->mm); +} + +static inline void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d, + unsigned long addr, unsigned long end, + unsigned long floor, unsigned long ceiling) +{ + pud_t *pud; + unsigned long next; + unsigned long start; + + start = addr; + pud = pud_offset(p4d, addr); + do { + next = pud_addr_end(addr, end); + if (pud_none_or_clear_bad(pud)) + continue; + free_pmd_range(tlb, pud, addr, next, floor, ceiling); + } while (pud++, addr = next, addr != end); + + start &= P4D_MASK; + if (start < floor) + return; + if (ceiling) { + ceiling &= P4D_MASK; + if (!ceiling) + return; + } + if (end - 1 > ceiling - 1) + return; + + pud = pud_offset(p4d, start); + p4d_clear(p4d); + pud_free_tlb(tlb, pud, start); + mm_dec_nr_puds(tlb->mm); +} + +static inline void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd, + unsigned long addr, unsigned long end, + unsigned long floor, unsigned long ceiling) +{ + p4d_t *p4d; + unsigned long next; + unsigned long start; + + start = addr; + p4d = p4d_offset(pgd, addr); + do { + next = p4d_addr_end(addr, end); + if (p4d_none_or_clear_bad(p4d)) + continue; + free_pud_range(tlb, p4d, addr, next, floor, ceiling); + } while (p4d++, addr = next, addr != end); + + start &= PGDIR_MASK; + if (start < floor) + return; + if (ceiling) { + ceiling &= PGDIR_MASK; + if (!ceiling) + return; + } + if (end - 1 > ceiling - 1) + return; + + p4d = p4d_offset(pgd, start); + pgd_clear(pgd); + p4d_free_tlb(tlb, p4d, start); +} + +/* + * This function frees user-level page tables of a process. + */ +void free_pgd_range(struct mmu_gather *tlb, + unsigned long addr, unsigned long end, + unsigned long floor, unsigned long ceiling) +{ + pgd_t *pgd; + unsigned long next; + + /* + * The next few lines have given us lots of grief... + * + * Why are we testing PMD* at this top level? Because often + * there will be no work to do at all, and we'd prefer not to + * go all the way down to the bottom just to discover that. + * + * Why all these "- 1"s? Because 0 represents both the bottom + * of the address space and the top of it (using -1 for the + * top wouldn't help much: the masks would do the wrong thing). + * The rule is that addr 0 and floor 0 refer to the bottom of + * the address space, but end 0 and ceiling 0 refer to the top + * Comparisons need to use "end - 1" and "ceiling - 1" (though + * that end 0 case should be mythical). + * + * Wherever addr is brought up or ceiling brought down, we must + * be careful to reject "the opposite 0" before it confuses the + * subsequent tests. But what about where end is brought down + * by PMD_SIZE below? no, end can't go down to 0 there. + * + * Whereas we round start (addr) and ceiling down, by different + * masks at different levels, in order to test whether a table + * now has no other vmas using it, so can be freed, we don't + * bother to round floor or end up - the tests don't need that. + */ + + addr &= PMD_MASK; + if (addr < floor) { + addr += PMD_SIZE; + if (!addr) + return; + } + if (ceiling) { + ceiling &= PMD_MASK; + if (!ceiling) + return; + } + if (end - 1 > ceiling - 1) + end -= PMD_SIZE; + if (addr > end - 1) + return; + /* + * We add page table cache pages with PAGE_SIZE, + * (see pte_free_tlb()), flush the tlb if we need + */ + tlb_change_page_size(tlb, PAGE_SIZE); + pgd = pgd_offset(tlb->mm, addr); + do { + next = pgd_addr_end(addr, end); + if (pgd_none_or_clear_bad(pgd)) + continue; + free_p4d_range(tlb, pgd, addr, next, floor, ceiling); + } while (pgd++, addr = next, addr != end); +} + +void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt, + struct vm_area_struct *vma, unsigned long floor, + unsigned long ceiling) +{ + MA_STATE(mas, mt, vma->vm_end, vma->vm_end); + + do { + unsigned long addr = vma->vm_start; + struct vm_area_struct *next; + + /* + * Note: USER_PGTABLES_CEILING may be passed as ceiling and may + * be 0. This will underflow and is okay. + */ + next = mas_find(&mas, ceiling - 1); + + /* + * Hide vma from rmap and truncate_pagecache before freeing + * pgtables + */ + unlink_anon_vmas(vma); + unlink_file_vma(vma); + + if (is_vm_hugetlb_page(vma)) { + hugetlb_free_pgd_range(tlb, addr, vma->vm_end, + floor, next ? next->vm_start : ceiling); + } else { + /* + * Optimization: gather nearby vmas into one call down + */ + while (next && next->vm_start <= vma->vm_end + PMD_SIZE + && !is_vm_hugetlb_page(next)) { + vma = next; + next = mas_find(&mas, ceiling - 1); + unlink_anon_vmas(vma); + unlink_file_vma(vma); + } + free_pgd_range(tlb, addr, vma->vm_end, + floor, next ? next->vm_start : ceiling); + } + vma = next; + } while (vma); +} + +void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte) +{ + spinlock_t *ptl = pmd_lock(mm, pmd); + + if (likely(pmd_none(*pmd))) { /* Has another populated it ? */ + mm_inc_nr_ptes(mm); + /* + * Ensure all pte setup (eg. pte page lock and page clearing) are + * visible before the pte is made visible to other CPUs by being + * put into page tables. + * + * The other side of the story is the pointer chasing in the page + * table walking code (when walking the page table without locking; + * ie. most of the time). Fortunately, these data accesses consist + * of a chain of data-dependent loads, meaning most CPUs (alpha + * being the notable exception) will already guarantee loads are + * seen in-order. See the alpha page table accessors for the + * smp_rmb() barriers in page table walking code. + */ + smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */ + pmd_populate(mm, pmd, *pte); + *pte = NULL; + } + spin_unlock(ptl); +} + +int __pte_alloc(struct mm_struct *mm, pmd_t *pmd) +{ + pgtable_t new = pte_alloc_one(mm); + if (!new) + return -ENOMEM; + + pmd_install(mm, pmd, &new); + if (new) + pte_free(mm, new); + return 0; +} + +int __pte_alloc_kernel(pmd_t *pmd) +{ + pte_t *new = pte_alloc_one_kernel(&init_mm); + if (!new) + return -ENOMEM; + + spin_lock(&init_mm.page_table_lock); + if (likely(pmd_none(*pmd))) { /* Has another populated it ? */ + smp_wmb(); /* See comment in pmd_install() */ + pmd_populate_kernel(&init_mm, pmd, new); + new = NULL; + } + spin_unlock(&init_mm.page_table_lock); + if (new) + pte_free_kernel(&init_mm, new); + return 0; +} + +static inline void init_rss_vec(int *rss) +{ + memset(rss, 0, sizeof(int) * NR_MM_COUNTERS); +} + +static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss) +{ + int i; + + if (current->mm == mm) + sync_mm_rss(mm); + for (i = 0; i < NR_MM_COUNTERS; i++) + if (rss[i]) + add_mm_counter(mm, i, rss[i]); +} + +/* + * This function is called to print an error when a bad pte + * is found. For example, we might have a PFN-mapped pte in + * a region that doesn't allow it. + * + * The calling function must still handle the error. + */ +static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr, + pte_t pte, struct page *page) +{ + pgd_t *pgd = pgd_offset(vma->vm_mm, addr); + p4d_t *p4d = p4d_offset(pgd, addr); + pud_t *pud = pud_offset(p4d, addr); + pmd_t *pmd = pmd_offset(pud, addr); + struct address_space *mapping; + pgoff_t index; + static unsigned long resume; + static unsigned long nr_shown; + static unsigned long nr_unshown; + + /* + * Allow a burst of 60 reports, then keep quiet for that minute; + * or allow a steady drip of one report per second. + */ + if (nr_shown == 60) { + if (time_before(jiffies, resume)) { + nr_unshown++; + return; + } + if (nr_unshown) { + pr_alert("BUG: Bad page map: %lu messages suppressed\n", + nr_unshown); + nr_unshown = 0; + } + nr_shown = 0; + } + if (nr_shown++ == 0) + resume = jiffies + 60 * HZ; + + mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL; + index = linear_page_index(vma, addr); + + pr_alert("BUG: Bad page map in process %s pte:%08llx pmd:%08llx\n", + current->comm, + (long long)pte_val(pte), (long long)pmd_val(*pmd)); + if (page) + dump_page(page, "bad pte"); + pr_alert("addr:%px vm_flags:%08lx anon_vma:%px mapping:%px index:%lx\n", + (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index); + pr_alert("file:%pD fault:%ps mmap:%ps read_folio:%ps\n", + vma->vm_file, + vma->vm_ops ? vma->vm_ops->fault : NULL, + vma->vm_file ? vma->vm_file->f_op->mmap : NULL, + mapping ? mapping->a_ops->read_folio : NULL); + dump_stack(); + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); +} + +/* + * vm_normal_page -- This function gets the "struct page" associated with a pte. + * + * "Special" mappings do not wish to be associated with a "struct page" (either + * it doesn't exist, or it exists but they don't want to touch it). In this + * case, NULL is returned here. "Normal" mappings do have a struct page. + * + * There are 2 broad cases. Firstly, an architecture may define a pte_special() + * pte bit, in which case this function is trivial. Secondly, an architecture + * may not have a spare pte bit, which requires a more complicated scheme, + * described below. + * + * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a + * special mapping (even if there are underlying and valid "struct pages"). + * COWed pages of a VM_PFNMAP are always normal. + * + * The way we recognize COWed pages within VM_PFNMAP mappings is through the + * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit + * set, and the vm_pgoff will point to the first PFN mapped: thus every special + * mapping will always honor the rule + * + * pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT) + * + * And for normal mappings this is false. + * + * This restricts such mappings to be a linear translation from virtual address + * to pfn. To get around this restriction, we allow arbitrary mappings so long + * as the vma is not a COW mapping; in that case, we know that all ptes are + * special (because none can have been COWed). + * + * + * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP. + * + * VM_MIXEDMAP mappings can likewise contain memory with or without "struct + * page" backing, however the difference is that _all_ pages with a struct + * page (that is, those where pfn_valid is true) are refcounted and considered + * normal pages by the VM. The disadvantage is that pages are refcounted + * (which can be slower and simply not an option for some PFNMAP users). The + * advantage is that we don't have to follow the strict linearity rule of + * PFNMAP mappings in order to support COWable mappings. + * + */ +struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, + pte_t pte) +{ + unsigned long pfn = pte_pfn(pte); + + if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) { + if (likely(!pte_special(pte))) + goto check_pfn; + if (vma->vm_ops && vma->vm_ops->find_special_page) + return vma->vm_ops->find_special_page(vma, addr); + if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)) + return NULL; + if (is_zero_pfn(pfn)) + return NULL; + if (pte_devmap(pte)) + /* + * NOTE: New users of ZONE_DEVICE will not set pte_devmap() + * and will have refcounts incremented on their struct pages + * when they are inserted into PTEs, thus they are safe to + * return here. Legacy ZONE_DEVICE pages that set pte_devmap() + * do not have refcounts. Example of legacy ZONE_DEVICE is + * MEMORY_DEVICE_FS_DAX type in pmem or virtio_fs drivers. + */ + return NULL; + + print_bad_pte(vma, addr, pte, NULL); + return NULL; + } + + /* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */ + + if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) { + if (vma->vm_flags & VM_MIXEDMAP) { + if (!pfn_valid(pfn)) + return NULL; + goto out; + } else { + unsigned long off; + off = (addr - vma->vm_start) >> PAGE_SHIFT; + if (pfn == vma->vm_pgoff + off) + return NULL; + if (!is_cow_mapping(vma->vm_flags)) + return NULL; + } + } + + if (is_zero_pfn(pfn)) + return NULL; + +check_pfn: + if (unlikely(pfn > highest_memmap_pfn)) { + print_bad_pte(vma, addr, pte, NULL); + return NULL; + } + + /* + * NOTE! We still have PageReserved() pages in the page tables. + * eg. VDSO mappings can cause them to exist. + */ +out: + return pfn_to_page(pfn); +} + +struct folio *vm_normal_folio(struct vm_area_struct *vma, unsigned long addr, + pte_t pte) +{ + struct page *page = vm_normal_page(vma, addr, pte); + + if (page) + return page_folio(page); + return NULL; +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr, + pmd_t pmd) +{ + unsigned long pfn = pmd_pfn(pmd); + + /* + * There is no pmd_special() but there may be special pmds, e.g. + * in a direct-access (dax) mapping, so let's just replicate the + * !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here. + */ + if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) { + if (vma->vm_flags & VM_MIXEDMAP) { + if (!pfn_valid(pfn)) + return NULL; + goto out; + } else { + unsigned long off; + off = (addr - vma->vm_start) >> PAGE_SHIFT; + if (pfn == vma->vm_pgoff + off) + return NULL; + if (!is_cow_mapping(vma->vm_flags)) + return NULL; + } + } + + if (pmd_devmap(pmd)) + return NULL; + if (is_huge_zero_pmd(pmd)) + return NULL; + if (unlikely(pfn > highest_memmap_pfn)) + return NULL; + + /* + * NOTE! We still have PageReserved() pages in the page tables. + * eg. VDSO mappings can cause them to exist. + */ +out: + return pfn_to_page(pfn); +} +#endif + +static void restore_exclusive_pte(struct vm_area_struct *vma, + struct page *page, unsigned long address, + pte_t *ptep) +{ + pte_t pte; + swp_entry_t entry; + + pte = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot))); + if (pte_swp_soft_dirty(*ptep)) + pte = pte_mksoft_dirty(pte); + + entry = pte_to_swp_entry(*ptep); + if (pte_swp_uffd_wp(*ptep)) + pte = pte_mkuffd_wp(pte); + else if (is_writable_device_exclusive_entry(entry)) + pte = maybe_mkwrite(pte_mkdirty(pte), vma); + + VM_BUG_ON(pte_write(pte) && !(PageAnon(page) && PageAnonExclusive(page))); + + /* + * No need to take a page reference as one was already + * created when the swap entry was made. + */ + if (PageAnon(page)) + page_add_anon_rmap(page, vma, address, RMAP_NONE); + else + /* + * Currently device exclusive access only supports anonymous + * memory so the entry shouldn't point to a filebacked page. + */ + WARN_ON_ONCE(1); + + set_pte_at(vma->vm_mm, address, ptep, pte); + + /* + * No need to invalidate - it was non-present before. However + * secondary CPUs may have mappings that need invalidating. + */ + update_mmu_cache(vma, address, ptep); +} + +/* + * Tries to restore an exclusive pte if the page lock can be acquired without + * sleeping. + */ +static int +try_restore_exclusive_pte(pte_t *src_pte, struct vm_area_struct *vma, + unsigned long addr) +{ + swp_entry_t entry = pte_to_swp_entry(*src_pte); + struct page *page = pfn_swap_entry_to_page(entry); + + if (trylock_page(page)) { + restore_exclusive_pte(vma, page, addr, src_pte); + unlock_page(page); + return 0; + } + + return -EBUSY; +} + +/* + * copy one vm_area from one task to the other. Assumes the page tables + * already present in the new task to be cleared in the whole range + * covered by this vma. + */ + +static unsigned long +copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, + pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma, unsigned long addr, int *rss) +{ + unsigned long vm_flags = dst_vma->vm_flags; + pte_t pte = *src_pte; + struct page *page; + swp_entry_t entry = pte_to_swp_entry(pte); + + if (likely(!non_swap_entry(entry))) { + if (swap_duplicate(entry) < 0) + return -EIO; + + /* make sure dst_mm is on swapoff's mmlist. */ + if (unlikely(list_empty(&dst_mm->mmlist))) { + spin_lock(&mmlist_lock); + if (list_empty(&dst_mm->mmlist)) + list_add(&dst_mm->mmlist, + &src_mm->mmlist); + spin_unlock(&mmlist_lock); + } + /* Mark the swap entry as shared. */ + if (pte_swp_exclusive(*src_pte)) { + pte = pte_swp_clear_exclusive(*src_pte); + set_pte_at(src_mm, addr, src_pte, pte); + } + rss[MM_SWAPENTS]++; + } else if (is_migration_entry(entry)) { + page = pfn_swap_entry_to_page(entry); + + rss[mm_counter(page)]++; + + if (!is_readable_migration_entry(entry) && + is_cow_mapping(vm_flags)) { + /* + * COW mappings require pages in both parent and child + * to be set to read. A previously exclusive entry is + * now shared. + */ + entry = make_readable_migration_entry( + swp_offset(entry)); + pte = swp_entry_to_pte(entry); + if (pte_swp_soft_dirty(*src_pte)) + pte = pte_swp_mksoft_dirty(pte); + if (pte_swp_uffd_wp(*src_pte)) + pte = pte_swp_mkuffd_wp(pte); + set_pte_at(src_mm, addr, src_pte, pte); + } + } else if (is_device_private_entry(entry)) { + page = pfn_swap_entry_to_page(entry); + + /* + * Update rss count even for unaddressable pages, as + * they should treated just like normal pages in this + * respect. + * + * We will likely want to have some new rss counters + * for unaddressable pages, at some point. But for now + * keep things as they are. + */ + get_page(page); + rss[mm_counter(page)]++; + /* Cannot fail as these pages cannot get pinned. */ + BUG_ON(page_try_dup_anon_rmap(page, false, src_vma)); + + /* + * We do not preserve soft-dirty information, because so + * far, checkpoint/restore is the only feature that + * requires that. And checkpoint/restore does not work + * when a device driver is involved (you cannot easily + * save and restore device driver state). + */ + if (is_writable_device_private_entry(entry) && + is_cow_mapping(vm_flags)) { + entry = make_readable_device_private_entry( + swp_offset(entry)); + pte = swp_entry_to_pte(entry); + if (pte_swp_uffd_wp(*src_pte)) + pte = pte_swp_mkuffd_wp(pte); + set_pte_at(src_mm, addr, src_pte, pte); + } + } else if (is_device_exclusive_entry(entry)) { + /* + * Make device exclusive entries present by restoring the + * original entry then copying as for a present pte. Device + * exclusive entries currently only support private writable + * (ie. COW) mappings. + */ + VM_BUG_ON(!is_cow_mapping(src_vma->vm_flags)); + if (try_restore_exclusive_pte(src_pte, src_vma, addr)) + return -EBUSY; + return -ENOENT; + } else if (is_pte_marker_entry(entry)) { + if (userfaultfd_wp(dst_vma)) + set_pte_at(dst_mm, addr, dst_pte, pte); + return 0; + } + if (!userfaultfd_wp(dst_vma)) + pte = pte_swp_clear_uffd_wp(pte); + set_pte_at(dst_mm, addr, dst_pte, pte); + return 0; +} + +/* + * Copy a present and normal page. + * + * NOTE! The usual case is that this isn't required; + * instead, the caller can just increase the page refcount + * and re-use the pte the traditional way. + * + * And if we need a pre-allocated page but don't yet have + * one, return a negative error to let the preallocation + * code know so that it can do so outside the page table + * lock. + */ +static inline int +copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, + pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, + struct page **prealloc, struct page *page) +{ + struct page *new_page; + pte_t pte; + + new_page = *prealloc; + if (!new_page) + return -EAGAIN; + + /* + * We have a prealloc page, all good! Take it + * over and copy the page & arm it. + */ + *prealloc = NULL; + copy_user_highpage(new_page, page, addr, src_vma); + __SetPageUptodate(new_page); + page_add_new_anon_rmap(new_page, dst_vma, addr); + lru_cache_add_inactive_or_unevictable(new_page, dst_vma); + rss[mm_counter(new_page)]++; + + /* All done, just insert the new page copy in the child */ + pte = mk_pte(new_page, dst_vma->vm_page_prot); + pte = maybe_mkwrite(pte_mkdirty(pte), dst_vma); + if (userfaultfd_pte_wp(dst_vma, *src_pte)) + /* Uffd-wp needs to be delivered to dest pte as well */ + pte = pte_wrprotect(pte_mkuffd_wp(pte)); + set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte); + return 0; +} + +/* + * Copy one pte. Returns 0 if succeeded, or -EAGAIN if one preallocated page + * is required to copy this pte. + */ +static inline int +copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, + pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, + struct page **prealloc) +{ + struct mm_struct *src_mm = src_vma->vm_mm; + unsigned long vm_flags = src_vma->vm_flags; + pte_t pte = *src_pte; + struct page *page; + + page = vm_normal_page(src_vma, addr, pte); + if (page && PageAnon(page)) { + /* + * If this page may have been pinned by the parent process, + * copy the page immediately for the child so that we'll always + * guarantee the pinned page won't be randomly replaced in the + * future. + */ + get_page(page); + if (unlikely(page_try_dup_anon_rmap(page, false, src_vma))) { + /* Page maybe pinned, we have to copy. */ + put_page(page); + return copy_present_page(dst_vma, src_vma, dst_pte, src_pte, + addr, rss, prealloc, page); + } + rss[mm_counter(page)]++; + } else if (page) { + get_page(page); + page_dup_file_rmap(page, false); + rss[mm_counter(page)]++; + } + + /* + * If it's a COW mapping, write protect it both + * in the parent and the child + */ + if (is_cow_mapping(vm_flags) && pte_write(pte)) { + ptep_set_wrprotect(src_mm, addr, src_pte); + pte = pte_wrprotect(pte); + } + VM_BUG_ON(page && PageAnon(page) && PageAnonExclusive(page)); + + /* + * If it's a shared mapping, mark it clean in + * the child + */ + if (vm_flags & VM_SHARED) + pte = pte_mkclean(pte); + pte = pte_mkold(pte); + + if (!userfaultfd_wp(dst_vma)) + pte = pte_clear_uffd_wp(pte); + + set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte); + return 0; +} + +static inline struct page * +page_copy_prealloc(struct mm_struct *src_mm, struct vm_area_struct *vma, + unsigned long addr) +{ + struct page *new_page; + + new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, addr); + if (!new_page) + return NULL; + + if (mem_cgroup_charge(page_folio(new_page), src_mm, GFP_KERNEL)) { + put_page(new_page); + return NULL; + } + cgroup_throttle_swaprate(new_page, GFP_KERNEL); + + return new_page; +} + +static int +copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, + pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, + unsigned long end) +{ + struct mm_struct *dst_mm = dst_vma->vm_mm; + struct mm_struct *src_mm = src_vma->vm_mm; + pte_t *orig_src_pte, *orig_dst_pte; + pte_t *src_pte, *dst_pte; + spinlock_t *src_ptl, *dst_ptl; + int progress, ret = 0; + int rss[NR_MM_COUNTERS]; + swp_entry_t entry = (swp_entry_t){0}; + struct page *prealloc = NULL; + +again: + progress = 0; + init_rss_vec(rss); + + dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl); + if (!dst_pte) { + ret = -ENOMEM; + goto out; + } + src_pte = pte_offset_map(src_pmd, addr); + src_ptl = pte_lockptr(src_mm, src_pmd); + spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); + orig_src_pte = src_pte; + orig_dst_pte = dst_pte; + arch_enter_lazy_mmu_mode(); + + do { + /* + * We are holding two locks at this point - either of them + * could generate latencies in another task on another CPU. + */ + if (progress >= 32) { + progress = 0; + if (need_resched() || + spin_needbreak(src_ptl) || spin_needbreak(dst_ptl)) + break; + } + if (pte_none(*src_pte)) { + progress++; + continue; + } + if (unlikely(!pte_present(*src_pte))) { + ret = copy_nonpresent_pte(dst_mm, src_mm, + dst_pte, src_pte, + dst_vma, src_vma, + addr, rss); + if (ret == -EIO) { + entry = pte_to_swp_entry(*src_pte); + break; + } else if (ret == -EBUSY) { + break; + } else if (!ret) { + progress += 8; + continue; + } + + /* + * Device exclusive entry restored, continue by copying + * the now present pte. + */ + WARN_ON_ONCE(ret != -ENOENT); + } + /* copy_present_pte() will clear `*prealloc' if consumed */ + ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte, + addr, rss, &prealloc); + /* + * If we need a pre-allocated page for this pte, drop the + * locks, allocate, and try again. + */ + if (unlikely(ret == -EAGAIN)) + break; + if (unlikely(prealloc)) { + /* + * pre-alloc page cannot be reused by next time so as + * to strictly follow mempolicy (e.g., alloc_page_vma() + * will allocate page according to address). This + * could only happen if one pinned pte changed. + */ + put_page(prealloc); + prealloc = NULL; + } + progress += 8; + } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end); + + arch_leave_lazy_mmu_mode(); + spin_unlock(src_ptl); + pte_unmap(orig_src_pte); + add_mm_rss_vec(dst_mm, rss); + pte_unmap_unlock(orig_dst_pte, dst_ptl); + cond_resched(); + + if (ret == -EIO) { + VM_WARN_ON_ONCE(!entry.val); + if (add_swap_count_continuation(entry, GFP_KERNEL) < 0) { + ret = -ENOMEM; + goto out; + } + entry.val = 0; + } else if (ret == -EBUSY) { + goto out; + } else if (ret == -EAGAIN) { + prealloc = page_copy_prealloc(src_mm, src_vma, addr); + if (!prealloc) + return -ENOMEM; + } else if (ret) { + VM_WARN_ON_ONCE(1); + } + + /* We've captured and resolved the error. Reset, try again. */ + ret = 0; + + if (addr != end) + goto again; +out: + if (unlikely(prealloc)) + put_page(prealloc); + return ret; +} + +static inline int +copy_pmd_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, + pud_t *dst_pud, pud_t *src_pud, unsigned long addr, + unsigned long end) +{ + struct mm_struct *dst_mm = dst_vma->vm_mm; + struct mm_struct *src_mm = src_vma->vm_mm; + pmd_t *src_pmd, *dst_pmd; + unsigned long next; + + dst_pmd = pmd_alloc(dst_mm, dst_pud, addr); + if (!dst_pmd) + return -ENOMEM; + src_pmd = pmd_offset(src_pud, addr); + do { + next = pmd_addr_end(addr, end); + if (is_swap_pmd(*src_pmd) || pmd_trans_huge(*src_pmd) + || pmd_devmap(*src_pmd)) { + int err; + VM_BUG_ON_VMA(next-addr != HPAGE_PMD_SIZE, src_vma); + err = copy_huge_pmd(dst_mm, src_mm, dst_pmd, src_pmd, + addr, dst_vma, src_vma); + if (err == -ENOMEM) + return -ENOMEM; + if (!err) + continue; + /* fall through */ + } + if (pmd_none_or_clear_bad(src_pmd)) + continue; + if (copy_pte_range(dst_vma, src_vma, dst_pmd, src_pmd, + addr, next)) + return -ENOMEM; + } while (dst_pmd++, src_pmd++, addr = next, addr != end); + return 0; +} + +static inline int +copy_pud_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, + p4d_t *dst_p4d, p4d_t *src_p4d, unsigned long addr, + unsigned long end) +{ + struct mm_struct *dst_mm = dst_vma->vm_mm; + struct mm_struct *src_mm = src_vma->vm_mm; + pud_t *src_pud, *dst_pud; + unsigned long next; + + dst_pud = pud_alloc(dst_mm, dst_p4d, addr); + if (!dst_pud) + return -ENOMEM; + src_pud = pud_offset(src_p4d, addr); + do { + next = pud_addr_end(addr, end); + if (pud_trans_huge(*src_pud) || pud_devmap(*src_pud)) { + int err; + + VM_BUG_ON_VMA(next-addr != HPAGE_PUD_SIZE, src_vma); + err = copy_huge_pud(dst_mm, src_mm, + dst_pud, src_pud, addr, src_vma); + if (err == -ENOMEM) + return -ENOMEM; + if (!err) + continue; + /* fall through */ + } + if (pud_none_or_clear_bad(src_pud)) + continue; + if (copy_pmd_range(dst_vma, src_vma, dst_pud, src_pud, + addr, next)) + return -ENOMEM; + } while (dst_pud++, src_pud++, addr = next, addr != end); + return 0; +} + +static inline int +copy_p4d_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, + pgd_t *dst_pgd, pgd_t *src_pgd, unsigned long addr, + unsigned long end) +{ + struct mm_struct *dst_mm = dst_vma->vm_mm; + p4d_t *src_p4d, *dst_p4d; + unsigned long next; + + dst_p4d = p4d_alloc(dst_mm, dst_pgd, addr); + if (!dst_p4d) + return -ENOMEM; + src_p4d = p4d_offset(src_pgd, addr); + do { + next = p4d_addr_end(addr, end); + if (p4d_none_or_clear_bad(src_p4d)) + continue; + if (copy_pud_range(dst_vma, src_vma, dst_p4d, src_p4d, + addr, next)) + return -ENOMEM; + } while (dst_p4d++, src_p4d++, addr = next, addr != end); + return 0; +} + +/* + * Return true if the vma needs to copy the pgtable during this fork(). Return + * false when we can speed up fork() by allowing lazy page faults later until + * when the child accesses the memory range. + */ +static bool +vma_needs_copy(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) +{ + /* + * Always copy pgtables when dst_vma has uffd-wp enabled even if it's + * file-backed (e.g. shmem). Because when uffd-wp is enabled, pgtable + * contains uffd-wp protection information, that's something we can't + * retrieve from page cache, and skip copying will lose those info. + */ + if (userfaultfd_wp(dst_vma)) + return true; + + if (src_vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)) + return true; + + if (src_vma->anon_vma) + return true; + + /* + * Don't copy ptes where a page fault will fill them correctly. Fork + * becomes much lighter when there are big shared or private readonly + * mappings. The tradeoff is that copy_page_range is more efficient + * than faulting. + */ + return false; +} + +int +copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) +{ + pgd_t *src_pgd, *dst_pgd; + unsigned long next; + unsigned long addr = src_vma->vm_start; + unsigned long end = src_vma->vm_end; + struct mm_struct *dst_mm = dst_vma->vm_mm; + struct mm_struct *src_mm = src_vma->vm_mm; + struct mmu_notifier_range range; + bool is_cow; + int ret; + + if (!vma_needs_copy(dst_vma, src_vma)) + return 0; + + if (is_vm_hugetlb_page(src_vma)) + return copy_hugetlb_page_range(dst_mm, src_mm, dst_vma, src_vma); + + if (unlikely(src_vma->vm_flags & VM_PFNMAP)) { + /* + * We do not free on error cases below as remove_vma + * gets called on error from higher level routine + */ + ret = track_pfn_copy(src_vma); + if (ret) + return ret; + } + + /* + * We need to invalidate the secondary MMU mappings only when + * there could be a permission downgrade on the ptes of the + * parent mm. And a permission downgrade will only happen if + * is_cow_mapping() returns true. + */ + is_cow = is_cow_mapping(src_vma->vm_flags); + + if (is_cow) { + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, + 0, src_vma, src_mm, addr, end); + mmu_notifier_invalidate_range_start(&range); + /* + * Disabling preemption is not needed for the write side, as + * the read side doesn't spin, but goes to the mmap_lock. + * + * Use the raw variant of the seqcount_t write API to avoid + * lockdep complaining about preemptibility. + */ + mmap_assert_write_locked(src_mm); + raw_write_seqcount_begin(&src_mm->write_protect_seq); + } + + ret = 0; + dst_pgd = pgd_offset(dst_mm, addr); + src_pgd = pgd_offset(src_mm, addr); + do { + next = pgd_addr_end(addr, end); + if (pgd_none_or_clear_bad(src_pgd)) + continue; + if (unlikely(copy_p4d_range(dst_vma, src_vma, dst_pgd, src_pgd, + addr, next))) { + ret = -ENOMEM; + break; + } + } while (dst_pgd++, src_pgd++, addr = next, addr != end); + + if (is_cow) { + raw_write_seqcount_end(&src_mm->write_protect_seq); + mmu_notifier_invalidate_range_end(&range); + } + return ret; +} + +/* Whether we should zap all COWed (private) pages too */ +static inline bool should_zap_cows(struct zap_details *details) +{ + /* By default, zap all pages */ + if (!details) + return true; + + /* Or, we zap COWed pages only if the caller wants to */ + return details->even_cows; +} + +/* Decides whether we should zap this page with the page pointer specified */ +static inline bool should_zap_page(struct zap_details *details, struct page *page) +{ + /* If we can make a decision without *page.. */ + if (should_zap_cows(details)) + return true; + + /* E.g. the caller passes NULL for the case of a zero page */ + if (!page) + return true; + + /* Otherwise we should only zap non-anon pages */ + return !PageAnon(page); +} + +static inline bool zap_drop_file_uffd_wp(struct zap_details *details) +{ + if (!details) + return false; + + return details->zap_flags & ZAP_FLAG_DROP_MARKER; +} + +/* + * This function makes sure that we'll replace the none pte with an uffd-wp + * swap special pte marker when necessary. Must be with the pgtable lock held. + */ +static inline void +zap_install_uffd_wp_if_needed(struct vm_area_struct *vma, + unsigned long addr, pte_t *pte, + struct zap_details *details, pte_t pteval) +{ +#ifdef CONFIG_PTE_MARKER_UFFD_WP + if (zap_drop_file_uffd_wp(details)) + return; + + pte_install_uffd_wp_if_needed(vma, addr, pte, pteval); +#endif +} + +static unsigned long zap_pte_range(struct mmu_gather *tlb, + struct vm_area_struct *vma, pmd_t *pmd, + unsigned long addr, unsigned long end, + struct zap_details *details) +{ + struct mm_struct *mm = tlb->mm; + int force_flush = 0; + int rss[NR_MM_COUNTERS]; + spinlock_t *ptl; + pte_t *start_pte; + pte_t *pte; + swp_entry_t entry; + + tlb_change_page_size(tlb, PAGE_SIZE); +again: + init_rss_vec(rss); + start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl); + pte = start_pte; + flush_tlb_batched_pending(mm); + arch_enter_lazy_mmu_mode(); + do { + pte_t ptent = *pte; + struct page *page; + + if (pte_none(ptent)) + continue; + + if (need_resched()) + break; + + if (pte_present(ptent)) { + page = vm_normal_page(vma, addr, ptent); + if (unlikely(!should_zap_page(details, page))) + continue; + ptent = ptep_get_and_clear_full(mm, addr, pte, + tlb->fullmm); + tlb_remove_tlb_entry(tlb, pte, addr); + zap_install_uffd_wp_if_needed(vma, addr, pte, details, + ptent); + if (unlikely(!page)) + continue; + + if (!PageAnon(page)) { + if (pte_dirty(ptent)) { + force_flush = 1; + set_page_dirty(page); + } + if (pte_young(ptent) && + likely(!(vma->vm_flags & VM_SEQ_READ))) + mark_page_accessed(page); + } + rss[mm_counter(page)]--; + page_remove_rmap(page, vma, false); + if (unlikely(page_mapcount(page) < 0)) + print_bad_pte(vma, addr, ptent, page); + if (unlikely(__tlb_remove_page(tlb, page))) { + force_flush = 1; + addr += PAGE_SIZE; + break; + } + continue; + } + + entry = pte_to_swp_entry(ptent); + if (is_device_private_entry(entry) || + is_device_exclusive_entry(entry)) { + page = pfn_swap_entry_to_page(entry); + if (unlikely(!should_zap_page(details, page))) + continue; + /* + * Both device private/exclusive mappings should only + * work with anonymous page so far, so we don't need to + * consider uffd-wp bit when zap. For more information, + * see zap_install_uffd_wp_if_needed(). + */ + WARN_ON_ONCE(!vma_is_anonymous(vma)); + rss[mm_counter(page)]--; + if (is_device_private_entry(entry)) + page_remove_rmap(page, vma, false); + put_page(page); + } else if (!non_swap_entry(entry)) { + /* Genuine swap entry, hence a private anon page */ + if (!should_zap_cows(details)) + continue; + rss[MM_SWAPENTS]--; + if (unlikely(!free_swap_and_cache(entry))) + print_bad_pte(vma, addr, ptent, NULL); + } else if (is_migration_entry(entry)) { + page = pfn_swap_entry_to_page(entry); + if (!should_zap_page(details, page)) + continue; + rss[mm_counter(page)]--; + } else if (pte_marker_entry_uffd_wp(entry)) { + /* Only drop the uffd-wp marker if explicitly requested */ + if (!zap_drop_file_uffd_wp(details)) + continue; + } else if (is_hwpoison_entry(entry) || + is_swapin_error_entry(entry)) { + if (!should_zap_cows(details)) + continue; + } else { + /* We should have covered all the swap entry types */ + WARN_ON_ONCE(1); + } + pte_clear_not_present_full(mm, addr, pte, tlb->fullmm); + zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent); + } while (pte++, addr += PAGE_SIZE, addr != end); + + add_mm_rss_vec(mm, rss); + arch_leave_lazy_mmu_mode(); + + /* Do the actual TLB flush before dropping ptl */ + if (force_flush) + tlb_flush_mmu_tlbonly(tlb); + pte_unmap_unlock(start_pte, ptl); + + /* + * If we forced a TLB flush (either due to running out of + * batch buffers or because we needed to flush dirty TLB + * entries before releasing the ptl), free the batched + * memory too. Restart if we didn't do everything. + */ + if (force_flush) { + force_flush = 0; + tlb_flush_mmu(tlb); + } + + if (addr != end) { + cond_resched(); + goto again; + } + + return addr; +} + +static inline unsigned long zap_pmd_range(struct mmu_gather *tlb, + struct vm_area_struct *vma, pud_t *pud, + unsigned long addr, unsigned long end, + struct zap_details *details) +{ + pmd_t *pmd; + unsigned long next; + + pmd = pmd_offset(pud, addr); + do { + next = pmd_addr_end(addr, end); + if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) { + if (next - addr != HPAGE_PMD_SIZE) + __split_huge_pmd(vma, pmd, addr, false, NULL); + else if (zap_huge_pmd(tlb, vma, pmd, addr)) + goto next; + /* fall through */ + } else if (details && details->single_folio && + folio_test_pmd_mappable(details->single_folio) && + next - addr == HPAGE_PMD_SIZE && pmd_none(*pmd)) { + spinlock_t *ptl = pmd_lock(tlb->mm, pmd); + /* + * Take and drop THP pmd lock so that we cannot return + * prematurely, while zap_huge_pmd() has cleared *pmd, + * but not yet decremented compound_mapcount(). + */ + spin_unlock(ptl); + } + + /* + * Here there can be other concurrent MADV_DONTNEED or + * trans huge page faults running, and if the pmd is + * none or trans huge it can change under us. This is + * because MADV_DONTNEED holds the mmap_lock in read + * mode. + */ + if (pmd_none_or_trans_huge_or_clear_bad(pmd)) + goto next; + next = zap_pte_range(tlb, vma, pmd, addr, next, details); +next: + cond_resched(); + } while (pmd++, addr = next, addr != end); + + return addr; +} + +static inline unsigned long zap_pud_range(struct mmu_gather *tlb, + struct vm_area_struct *vma, p4d_t *p4d, + unsigned long addr, unsigned long end, + struct zap_details *details) +{ + pud_t *pud; + unsigned long next; + + pud = pud_offset(p4d, addr); + do { + next = pud_addr_end(addr, end); + if (pud_trans_huge(*pud) || pud_devmap(*pud)) { + if (next - addr != HPAGE_PUD_SIZE) { + mmap_assert_locked(tlb->mm); + split_huge_pud(vma, pud, addr); + } else if (zap_huge_pud(tlb, vma, pud, addr)) + goto next; + /* fall through */ + } + if (pud_none_or_clear_bad(pud)) + continue; + next = zap_pmd_range(tlb, vma, pud, addr, next, details); +next: + cond_resched(); + } while (pud++, addr = next, addr != end); + + return addr; +} + +static inline unsigned long zap_p4d_range(struct mmu_gather *tlb, + struct vm_area_struct *vma, pgd_t *pgd, + unsigned long addr, unsigned long end, + struct zap_details *details) +{ + p4d_t *p4d; + unsigned long next; + + p4d = p4d_offset(pgd, addr); + do { + next = p4d_addr_end(addr, end); + if (p4d_none_or_clear_bad(p4d)) + continue; + next = zap_pud_range(tlb, vma, p4d, addr, next, details); + } while (p4d++, addr = next, addr != end); + + return addr; +} + +void unmap_page_range(struct mmu_gather *tlb, + struct vm_area_struct *vma, + unsigned long addr, unsigned long end, + struct zap_details *details) +{ + pgd_t *pgd; + unsigned long next; + + BUG_ON(addr >= end); + tlb_start_vma(tlb, vma); + pgd = pgd_offset(vma->vm_mm, addr); + do { + next = pgd_addr_end(addr, end); + if (pgd_none_or_clear_bad(pgd)) + continue; + next = zap_p4d_range(tlb, vma, pgd, addr, next, details); + } while (pgd++, addr = next, addr != end); + tlb_end_vma(tlb, vma); +} + + +static void unmap_single_vma(struct mmu_gather *tlb, + struct vm_area_struct *vma, unsigned long start_addr, + unsigned long end_addr, + struct zap_details *details) +{ + unsigned long start = max(vma->vm_start, start_addr); + unsigned long end; + + if (start >= vma->vm_end) + return; + end = min(vma->vm_end, end_addr); + if (end <= vma->vm_start) + return; + + if (vma->vm_file) + uprobe_munmap(vma, start, end); + + if (unlikely(vma->vm_flags & VM_PFNMAP)) + untrack_pfn(vma, 0, 0); + + if (start != end) { + if (unlikely(is_vm_hugetlb_page(vma))) { + /* + * It is undesirable to test vma->vm_file as it + * should be non-null for valid hugetlb area. + * However, vm_file will be NULL in the error + * cleanup path of mmap_region. When + * hugetlbfs ->mmap method fails, + * mmap_region() nullifies vma->vm_file + * before calling this function to clean up. + * Since no pte has actually been setup, it is + * safe to do nothing in this case. + */ + if (vma->vm_file) { + zap_flags_t zap_flags = details ? + details->zap_flags : 0; + __unmap_hugepage_range_final(tlb, vma, start, end, + NULL, zap_flags); + } + } else + unmap_page_range(tlb, vma, start, end, details); + } +} + +/** + * unmap_vmas - unmap a range of memory covered by a list of vma's + * @tlb: address of the caller's struct mmu_gather + * @mt: the maple tree + * @vma: the starting vma + * @start_addr: virtual address at which to start unmapping + * @end_addr: virtual address at which to end unmapping + * + * Unmap all pages in the vma list. + * + * Only addresses between `start' and `end' will be unmapped. + * + * The VMA list must be sorted in ascending virtual address order. + * + * unmap_vmas() assumes that the caller will flush the whole unmapped address + * range after unmap_vmas() returns. So the only responsibility here is to + * ensure that any thus-far unmapped pages are flushed before unmap_vmas() + * drops the lock and schedules. + */ +void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt, + struct vm_area_struct *vma, unsigned long start_addr, + unsigned long end_addr) +{ + struct mmu_notifier_range range; + struct zap_details details = { + .zap_flags = ZAP_FLAG_DROP_MARKER | ZAP_FLAG_UNMAP, + /* Careful - we need to zap private pages too! */ + .even_cows = true, + }; + MA_STATE(mas, mt, vma->vm_end, vma->vm_end); + + mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm, + start_addr, end_addr); + mmu_notifier_invalidate_range_start(&range); + do { + unmap_single_vma(tlb, vma, start_addr, end_addr, &details); + } while ((vma = mas_find(&mas, end_addr - 1)) != NULL); + mmu_notifier_invalidate_range_end(&range); +} + +/** + * zap_page_range - remove user pages in a given range + * @vma: vm_area_struct holding the applicable pages + * @start: starting address of pages to zap + * @size: number of bytes to zap + * + * Caller must protect the VMA list + */ +void zap_page_range(struct vm_area_struct *vma, unsigned long start, + unsigned long size) +{ + struct maple_tree *mt = &vma->vm_mm->mm_mt; + unsigned long end = start + size; + struct mmu_notifier_range range; + struct mmu_gather tlb; + MA_STATE(mas, mt, vma->vm_end, vma->vm_end); + + lru_add_drain(); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, + start, start + size); + tlb_gather_mmu(&tlb, vma->vm_mm); + update_hiwater_rss(vma->vm_mm); + mmu_notifier_invalidate_range_start(&range); + do { + unmap_single_vma(&tlb, vma, start, range.end, NULL); + } while ((vma = mas_find(&mas, end - 1)) != NULL); + mmu_notifier_invalidate_range_end(&range); + tlb_finish_mmu(&tlb); +} + +/** + * zap_page_range_single - remove user pages in a given range + * @vma: vm_area_struct holding the applicable pages + * @address: starting address of pages to zap + * @size: number of bytes to zap + * @details: details of shared cache invalidation + * + * The range must fit into one VMA. + */ +void zap_page_range_single(struct vm_area_struct *vma, unsigned long address, + unsigned long size, struct zap_details *details) +{ + const unsigned long end = address + size; + struct mmu_notifier_range range; + struct mmu_gather tlb; + + lru_add_drain(); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, + address, end); + if (is_vm_hugetlb_page(vma)) + adjust_range_if_pmd_sharing_possible(vma, &range.start, + &range.end); + tlb_gather_mmu(&tlb, vma->vm_mm); + update_hiwater_rss(vma->vm_mm); + mmu_notifier_invalidate_range_start(&range); + /* + * unmap 'address-end' not 'range.start-range.end' as range + * could have been expanded for hugetlb pmd sharing. + */ + unmap_single_vma(&tlb, vma, address, end, details); + mmu_notifier_invalidate_range_end(&range); + tlb_finish_mmu(&tlb); +} + +/** + * zap_vma_ptes - remove ptes mapping the vma + * @vma: vm_area_struct holding ptes to be zapped + * @address: starting address of pages to zap + * @size: number of bytes to zap + * + * This function only unmaps ptes assigned to VM_PFNMAP vmas. + * + * The entire address range must be fully contained within the vma. + * + */ +void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address, + unsigned long size) +{ + if (!range_in_vma(vma, address, address + size) || + !(vma->vm_flags & VM_PFNMAP)) + return; + + zap_page_range_single(vma, address, size, NULL); +} +EXPORT_SYMBOL_GPL(zap_vma_ptes); + +static pmd_t *walk_to_pmd(struct mm_struct *mm, unsigned long addr) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + + pgd = pgd_offset(mm, addr); + p4d = p4d_alloc(mm, pgd, addr); + if (!p4d) + return NULL; + pud = pud_alloc(mm, p4d, addr); + if (!pud) + return NULL; + pmd = pmd_alloc(mm, pud, addr); + if (!pmd) + return NULL; + + VM_BUG_ON(pmd_trans_huge(*pmd)); + return pmd; +} + +pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr, + spinlock_t **ptl) +{ + pmd_t *pmd = walk_to_pmd(mm, addr); + + if (!pmd) + return NULL; + return pte_alloc_map_lock(mm, pmd, addr, ptl); +} + +static int validate_page_before_insert(struct page *page) +{ + if (PageAnon(page) || PageSlab(page) || page_has_type(page)) + return -EINVAL; + flush_dcache_page(page); + return 0; +} + +static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte, + unsigned long addr, struct page *page, pgprot_t prot) +{ + if (!pte_none(*pte)) + return -EBUSY; + /* Ok, finally just insert the thing.. */ + get_page(page); + inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page)); + page_add_file_rmap(page, vma, false); + set_pte_at(vma->vm_mm, addr, pte, mk_pte(page, prot)); + return 0; +} + +/* + * This is the old fallback for page remapping. + * + * For historical reasons, it only allows reserved pages. Only + * old drivers should use this, and they needed to mark their + * pages reserved for the old functions anyway. + */ +static int insert_page(struct vm_area_struct *vma, unsigned long addr, + struct page *page, pgprot_t prot) +{ + int retval; + pte_t *pte; + spinlock_t *ptl; + + retval = validate_page_before_insert(page); + if (retval) + goto out; + retval = -ENOMEM; + pte = get_locked_pte(vma->vm_mm, addr, &ptl); + if (!pte) + goto out; + retval = insert_page_into_pte_locked(vma, pte, addr, page, prot); + pte_unmap_unlock(pte, ptl); +out: + return retval; +} + +#ifdef pte_index +static int insert_page_in_batch_locked(struct vm_area_struct *vma, pte_t *pte, + unsigned long addr, struct page *page, pgprot_t prot) +{ + int err; + + if (!page_count(page)) + return -EINVAL; + err = validate_page_before_insert(page); + if (err) + return err; + return insert_page_into_pte_locked(vma, pte, addr, page, prot); +} + +/* insert_pages() amortizes the cost of spinlock operations + * when inserting pages in a loop. Arch *must* define pte_index. + */ +static int insert_pages(struct vm_area_struct *vma, unsigned long addr, + struct page **pages, unsigned long *num, pgprot_t prot) +{ + pmd_t *pmd = NULL; + pte_t *start_pte, *pte; + spinlock_t *pte_lock; + struct mm_struct *const mm = vma->vm_mm; + unsigned long curr_page_idx = 0; + unsigned long remaining_pages_total = *num; + unsigned long pages_to_write_in_pmd; + int ret; +more: + ret = -EFAULT; + pmd = walk_to_pmd(mm, addr); + if (!pmd) + goto out; + + pages_to_write_in_pmd = min_t(unsigned long, + remaining_pages_total, PTRS_PER_PTE - pte_index(addr)); + + /* Allocate the PTE if necessary; takes PMD lock once only. */ + ret = -ENOMEM; + if (pte_alloc(mm, pmd)) + goto out; + + while (pages_to_write_in_pmd) { + int pte_idx = 0; + const int batch_size = min_t(int, pages_to_write_in_pmd, 8); + + start_pte = pte_offset_map_lock(mm, pmd, addr, &pte_lock); + for (pte = start_pte; pte_idx < batch_size; ++pte, ++pte_idx) { + int err = insert_page_in_batch_locked(vma, pte, + addr, pages[curr_page_idx], prot); + if (unlikely(err)) { + pte_unmap_unlock(start_pte, pte_lock); + ret = err; + remaining_pages_total -= pte_idx; + goto out; + } + addr += PAGE_SIZE; + ++curr_page_idx; + } + pte_unmap_unlock(start_pte, pte_lock); + pages_to_write_in_pmd -= batch_size; + remaining_pages_total -= batch_size; + } + if (remaining_pages_total) + goto more; + ret = 0; +out: + *num = remaining_pages_total; + return ret; +} +#endif /* ifdef pte_index */ + +/** + * vm_insert_pages - insert multiple pages into user vma, batching the pmd lock. + * @vma: user vma to map to + * @addr: target start user address of these pages + * @pages: source kernel pages + * @num: in: number of pages to map. out: number of pages that were *not* + * mapped. (0 means all pages were successfully mapped). + * + * Preferred over vm_insert_page() when inserting multiple pages. + * + * In case of error, we may have mapped a subset of the provided + * pages. It is the caller's responsibility to account for this case. + * + * The same restrictions apply as in vm_insert_page(). + */ +int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr, + struct page **pages, unsigned long *num) +{ +#ifdef pte_index + const unsigned long end_addr = addr + (*num * PAGE_SIZE) - 1; + + if (addr < vma->vm_start || end_addr >= vma->vm_end) + return -EFAULT; + if (!(vma->vm_flags & VM_MIXEDMAP)) { + BUG_ON(mmap_read_trylock(vma->vm_mm)); + BUG_ON(vma->vm_flags & VM_PFNMAP); + vma->vm_flags |= VM_MIXEDMAP; + } + /* Defer page refcount checking till we're about to map that page. */ + return insert_pages(vma, addr, pages, num, vma->vm_page_prot); +#else + unsigned long idx = 0, pgcount = *num; + int err = -EINVAL; + + for (; idx < pgcount; ++idx) { + err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]); + if (err) + break; + } + *num = pgcount - idx; + return err; +#endif /* ifdef pte_index */ +} +EXPORT_SYMBOL(vm_insert_pages); + +/** + * vm_insert_page - insert single page into user vma + * @vma: user vma to map to + * @addr: target user address of this page + * @page: source kernel page + * + * This allows drivers to insert individual pages they've allocated + * into a user vma. + * + * The page has to be a nice clean _individual_ kernel allocation. + * If you allocate a compound page, you need to have marked it as + * such (__GFP_COMP), or manually just split the page up yourself + * (see split_page()). + * + * NOTE! Traditionally this was done with "remap_pfn_range()" which + * took an arbitrary page protection parameter. This doesn't allow + * that. Your vma protection will have to be set up correctly, which + * means that if you want a shared writable mapping, you'd better + * ask for a shared writable mapping! + * + * The page does not need to be reserved. + * + * Usually this function is called from f_op->mmap() handler + * under mm->mmap_lock write-lock, so it can change vma->vm_flags. + * Caller must set VM_MIXEDMAP on vma if it wants to call this + * function from other places, for example from page-fault handler. + * + * Return: %0 on success, negative error code otherwise. + */ +int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, + struct page *page) +{ + if (addr < vma->vm_start || addr >= vma->vm_end) + return -EFAULT; + if (!page_count(page)) + return -EINVAL; + if (!(vma->vm_flags & VM_MIXEDMAP)) { + BUG_ON(mmap_read_trylock(vma->vm_mm)); + BUG_ON(vma->vm_flags & VM_PFNMAP); + vma->vm_flags |= VM_MIXEDMAP; + } + return insert_page(vma, addr, page, vma->vm_page_prot); +} +EXPORT_SYMBOL(vm_insert_page); + +/* + * __vm_map_pages - maps range of kernel pages into user vma + * @vma: user vma to map to + * @pages: pointer to array of source kernel pages + * @num: number of pages in page array + * @offset: user's requested vm_pgoff + * + * This allows drivers to map range of kernel pages into a user vma. + * + * Return: 0 on success and error code otherwise. + */ +static int __vm_map_pages(struct vm_area_struct *vma, struct page **pages, + unsigned long num, unsigned long offset) +{ + unsigned long count = vma_pages(vma); + unsigned long uaddr = vma->vm_start; + int ret, i; + + /* Fail if the user requested offset is beyond the end of the object */ + if (offset >= num) + return -ENXIO; + + /* Fail if the user requested size exceeds available object size */ + if (count > num - offset) + return -ENXIO; + + for (i = 0; i < count; i++) { + ret = vm_insert_page(vma, uaddr, pages[offset + i]); + if (ret < 0) + return ret; + uaddr += PAGE_SIZE; + } + + return 0; +} + +/** + * vm_map_pages - maps range of kernel pages starts with non zero offset + * @vma: user vma to map to + * @pages: pointer to array of source kernel pages + * @num: number of pages in page array + * + * Maps an object consisting of @num pages, catering for the user's + * requested vm_pgoff + * + * If we fail to insert any page into the vma, the function will return + * immediately leaving any previously inserted pages present. Callers + * from the mmap handler may immediately return the error as their caller + * will destroy the vma, removing any successfully inserted pages. Other + * callers should make their own arrangements for calling unmap_region(). + * + * Context: Process context. Called by mmap handlers. + * Return: 0 on success and error code otherwise. + */ +int vm_map_pages(struct vm_area_struct *vma, struct page **pages, + unsigned long num) +{ + return __vm_map_pages(vma, pages, num, vma->vm_pgoff); +} +EXPORT_SYMBOL(vm_map_pages); + +/** + * vm_map_pages_zero - map range of kernel pages starts with zero offset + * @vma: user vma to map to + * @pages: pointer to array of source kernel pages + * @num: number of pages in page array + * + * Similar to vm_map_pages(), except that it explicitly sets the offset + * to 0. This function is intended for the drivers that did not consider + * vm_pgoff. + * + * Context: Process context. Called by mmap handlers. + * Return: 0 on success and error code otherwise. + */ +int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages, + unsigned long num) +{ + return __vm_map_pages(vma, pages, num, 0); +} +EXPORT_SYMBOL(vm_map_pages_zero); + +static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr, + pfn_t pfn, pgprot_t prot, bool mkwrite) +{ + struct mm_struct *mm = vma->vm_mm; + pte_t *pte, entry; + spinlock_t *ptl; + + pte = get_locked_pte(mm, addr, &ptl); + if (!pte) + return VM_FAULT_OOM; + if (!pte_none(*pte)) { + if (mkwrite) { + /* + * For read faults on private mappings the PFN passed + * in may not match the PFN we have mapped if the + * mapped PFN is a writeable COW page. In the mkwrite + * case we are creating a writable PTE for a shared + * mapping and we expect the PFNs to match. If they + * don't match, we are likely racing with block + * allocation and mapping invalidation so just skip the + * update. + */ + if (pte_pfn(*pte) != pfn_t_to_pfn(pfn)) { + WARN_ON_ONCE(!is_zero_pfn(pte_pfn(*pte))); + goto out_unlock; + } + entry = pte_mkyoung(*pte); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + if (ptep_set_access_flags(vma, addr, pte, entry, 1)) + update_mmu_cache(vma, addr, pte); + } + goto out_unlock; + } + + /* Ok, finally just insert the thing.. */ + if (pfn_t_devmap(pfn)) + entry = pte_mkdevmap(pfn_t_pte(pfn, prot)); + else + entry = pte_mkspecial(pfn_t_pte(pfn, prot)); + + if (mkwrite) { + entry = pte_mkyoung(entry); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + } + + set_pte_at(mm, addr, pte, entry); + update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */ + +out_unlock: + pte_unmap_unlock(pte, ptl); + return VM_FAULT_NOPAGE; +} + +/** + * vmf_insert_pfn_prot - insert single pfn into user vma with specified pgprot + * @vma: user vma to map to + * @addr: target user address of this page + * @pfn: source kernel pfn + * @pgprot: pgprot flags for the inserted page + * + * This is exactly like vmf_insert_pfn(), except that it allows drivers + * to override pgprot on a per-page basis. + * + * This only makes sense for IO mappings, and it makes no sense for + * COW mappings. In general, using multiple vmas is preferable; + * vmf_insert_pfn_prot should only be used if using multiple VMAs is + * impractical. + * + * See vmf_insert_mixed_prot() for a discussion of the implication of using + * a value of @pgprot different from that of @vma->vm_page_prot. + * + * Context: Process context. May allocate using %GFP_KERNEL. + * Return: vm_fault_t value. + */ +vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, + unsigned long pfn, pgprot_t pgprot) +{ + /* + * Technically, architectures with pte_special can avoid all these + * restrictions (same for remap_pfn_range). However we would like + * consistency in testing and feature parity among all, so we should + * try to keep these invariants in place for everybody. + */ + BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))); + BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == + (VM_PFNMAP|VM_MIXEDMAP)); + BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); + BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn)); + + if (addr < vma->vm_start || addr >= vma->vm_end) + return VM_FAULT_SIGBUS; + + if (!pfn_modify_allowed(pfn, pgprot)) + return VM_FAULT_SIGBUS; + + track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV)); + + return insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot, + false); +} +EXPORT_SYMBOL(vmf_insert_pfn_prot); + +/** + * vmf_insert_pfn - insert single pfn into user vma + * @vma: user vma to map to + * @addr: target user address of this page + * @pfn: source kernel pfn + * + * Similar to vm_insert_page, this allows drivers to insert individual pages + * they've allocated into a user vma. Same comments apply. + * + * This function should only be called from a vm_ops->fault handler, and + * in that case the handler should return the result of this function. + * + * vma cannot be a COW mapping. + * + * As this is called only for pages that do not currently exist, we + * do not need to flush old virtual caches or the TLB. + * + * Context: Process context. May allocate using %GFP_KERNEL. + * Return: vm_fault_t value. + */ +vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr, + unsigned long pfn) +{ + return vmf_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot); +} +EXPORT_SYMBOL(vmf_insert_pfn); + +static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn) +{ + /* these checks mirror the abort conditions in vm_normal_page */ + if (vma->vm_flags & VM_MIXEDMAP) + return true; + if (pfn_t_devmap(pfn)) + return true; + if (pfn_t_special(pfn)) + return true; + if (is_zero_pfn(pfn_t_to_pfn(pfn))) + return true; + return false; +} + +static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma, + unsigned long addr, pfn_t pfn, pgprot_t pgprot, + bool mkwrite) +{ + int err; + + BUG_ON(!vm_mixed_ok(vma, pfn)); + + if (addr < vma->vm_start || addr >= vma->vm_end) + return VM_FAULT_SIGBUS; + + track_pfn_insert(vma, &pgprot, pfn); + + if (!pfn_modify_allowed(pfn_t_to_pfn(pfn), pgprot)) + return VM_FAULT_SIGBUS; + + /* + * If we don't have pte special, then we have to use the pfn_valid() + * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must* + * refcount the page if pfn_valid is true (hence insert_page rather + * than insert_pfn). If a zero_pfn were inserted into a VM_MIXEDMAP + * without pte special, it would there be refcounted as a normal page. + */ + if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && + !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) { + struct page *page; + + /* + * At this point we are committed to insert_page() + * regardless of whether the caller specified flags that + * result in pfn_t_has_page() == false. + */ + page = pfn_to_page(pfn_t_to_pfn(pfn)); + err = insert_page(vma, addr, page, pgprot); + } else { + return insert_pfn(vma, addr, pfn, pgprot, mkwrite); + } + + if (err == -ENOMEM) + return VM_FAULT_OOM; + if (err < 0 && err != -EBUSY) + return VM_FAULT_SIGBUS; + + return VM_FAULT_NOPAGE; +} + +/** + * vmf_insert_mixed_prot - insert single pfn into user vma with specified pgprot + * @vma: user vma to map to + * @addr: target user address of this page + * @pfn: source kernel pfn + * @pgprot: pgprot flags for the inserted page + * + * This is exactly like vmf_insert_mixed(), except that it allows drivers + * to override pgprot on a per-page basis. + * + * Typically this function should be used by drivers to set caching- and + * encryption bits different than those of @vma->vm_page_prot, because + * the caching- or encryption mode may not be known at mmap() time. + * This is ok as long as @vma->vm_page_prot is not used by the core vm + * to set caching and encryption bits for those vmas (except for COW pages). + * This is ensured by core vm only modifying these page table entries using + * functions that don't touch caching- or encryption bits, using pte_modify() + * if needed. (See for example mprotect()). + * Also when new page-table entries are created, this is only done using the + * fault() callback, and never using the value of vma->vm_page_prot, + * except for page-table entries that point to anonymous pages as the result + * of COW. + * + * Context: Process context. May allocate using %GFP_KERNEL. + * Return: vm_fault_t value. + */ +vm_fault_t vmf_insert_mixed_prot(struct vm_area_struct *vma, unsigned long addr, + pfn_t pfn, pgprot_t pgprot) +{ + return __vm_insert_mixed(vma, addr, pfn, pgprot, false); +} +EXPORT_SYMBOL(vmf_insert_mixed_prot); + +vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr, + pfn_t pfn) +{ + return __vm_insert_mixed(vma, addr, pfn, vma->vm_page_prot, false); +} +EXPORT_SYMBOL(vmf_insert_mixed); + +/* + * If the insertion of PTE failed because someone else already added a + * different entry in the mean time, we treat that as success as we assume + * the same entry was actually inserted. + */ +vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma, + unsigned long addr, pfn_t pfn) +{ + return __vm_insert_mixed(vma, addr, pfn, vma->vm_page_prot, true); +} +EXPORT_SYMBOL(vmf_insert_mixed_mkwrite); + +/* + * maps a range of physical memory into the requested pages. the old + * mappings are removed. any references to nonexistent pages results + * in null mappings (currently treated as "copy-on-access") + */ +static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd, + unsigned long addr, unsigned long end, + unsigned long pfn, pgprot_t prot) +{ + pte_t *pte, *mapped_pte; + spinlock_t *ptl; + int err = 0; + + mapped_pte = pte = pte_alloc_map_lock(mm, pmd, addr, &ptl); + if (!pte) + return -ENOMEM; + arch_enter_lazy_mmu_mode(); + do { + BUG_ON(!pte_none(*pte)); + if (!pfn_modify_allowed(pfn, prot)) { + err = -EACCES; + break; + } + set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot))); + pfn++; + } while (pte++, addr += PAGE_SIZE, addr != end); + arch_leave_lazy_mmu_mode(); + pte_unmap_unlock(mapped_pte, ptl); + return err; +} + +static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud, + unsigned long addr, unsigned long end, + unsigned long pfn, pgprot_t prot) +{ + pmd_t *pmd; + unsigned long next; + int err; + + pfn -= addr >> PAGE_SHIFT; + pmd = pmd_alloc(mm, pud, addr); + if (!pmd) + return -ENOMEM; + VM_BUG_ON(pmd_trans_huge(*pmd)); + do { + next = pmd_addr_end(addr, end); + err = remap_pte_range(mm, pmd, addr, next, + pfn + (addr >> PAGE_SHIFT), prot); + if (err) + return err; + } while (pmd++, addr = next, addr != end); + return 0; +} + +static inline int remap_pud_range(struct mm_struct *mm, p4d_t *p4d, + unsigned long addr, unsigned long end, + unsigned long pfn, pgprot_t prot) +{ + pud_t *pud; + unsigned long next; + int err; + + pfn -= addr >> PAGE_SHIFT; + pud = pud_alloc(mm, p4d, addr); + if (!pud) + return -ENOMEM; + do { + next = pud_addr_end(addr, end); + err = remap_pmd_range(mm, pud, addr, next, + pfn + (addr >> PAGE_SHIFT), prot); + if (err) + return err; + } while (pud++, addr = next, addr != end); + return 0; +} + +static inline int remap_p4d_range(struct mm_struct *mm, pgd_t *pgd, + unsigned long addr, unsigned long end, + unsigned long pfn, pgprot_t prot) +{ + p4d_t *p4d; + unsigned long next; + int err; + + pfn -= addr >> PAGE_SHIFT; + p4d = p4d_alloc(mm, pgd, addr); + if (!p4d) + return -ENOMEM; + do { + next = p4d_addr_end(addr, end); + err = remap_pud_range(mm, p4d, addr, next, + pfn + (addr >> PAGE_SHIFT), prot); + if (err) + return err; + } while (p4d++, addr = next, addr != end); + return 0; +} + +/* + * Variant of remap_pfn_range that does not call track_pfn_remap. The caller + * must have pre-validated the caching bits of the pgprot_t. + */ +int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr, + unsigned long pfn, unsigned long size, pgprot_t prot) +{ + pgd_t *pgd; + unsigned long next; + unsigned long end = addr + PAGE_ALIGN(size); + struct mm_struct *mm = vma->vm_mm; + int err; + + if (WARN_ON_ONCE(!PAGE_ALIGNED(addr))) + return -EINVAL; + + /* + * Physically remapped pages are special. Tell the + * rest of the world about it: + * VM_IO tells people not to look at these pages + * (accesses can have side effects). + * VM_PFNMAP tells the core MM that the base pages are just + * raw PFN mappings, and do not have a "struct page" associated + * with them. + * VM_DONTEXPAND + * Disable vma merging and expanding with mremap(). + * VM_DONTDUMP + * Omit vma from core dump, even when VM_IO turned off. + * + * There's a horrible special case to handle copy-on-write + * behaviour that some programs depend on. We mark the "original" + * un-COW'ed pages by matching them up with "vma->vm_pgoff". + * See vm_normal_page() for details. + */ + if (is_cow_mapping(vma->vm_flags)) { + if (addr != vma->vm_start || end != vma->vm_end) + return -EINVAL; + vma->vm_pgoff = pfn; + } + + vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP; + + BUG_ON(addr >= end); + pfn -= addr >> PAGE_SHIFT; + pgd = pgd_offset(mm, addr); + flush_cache_range(vma, addr, end); + do { + next = pgd_addr_end(addr, end); + err = remap_p4d_range(mm, pgd, addr, next, + pfn + (addr >> PAGE_SHIFT), prot); + if (err) + return err; + } while (pgd++, addr = next, addr != end); + + return 0; +} + +/** + * remap_pfn_range - remap kernel memory to userspace + * @vma: user vma to map to + * @addr: target page aligned user address to start at + * @pfn: page frame number of kernel physical memory address + * @size: size of mapping area + * @prot: page protection flags for this mapping + * + * Note: this is only safe if the mm semaphore is held when called. + * + * Return: %0 on success, negative error code otherwise. + */ +int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, + unsigned long pfn, unsigned long size, pgprot_t prot) +{ + int err; + + err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size)); + if (err) + return -EINVAL; + + err = remap_pfn_range_notrack(vma, addr, pfn, size, prot); + if (err) + untrack_pfn(vma, pfn, PAGE_ALIGN(size)); + return err; +} +EXPORT_SYMBOL(remap_pfn_range); + +/** + * vm_iomap_memory - remap memory to userspace + * @vma: user vma to map to + * @start: start of the physical memory to be mapped + * @len: size of area + * + * This is a simplified io_remap_pfn_range() for common driver use. The + * driver just needs to give us the physical memory range to be mapped, + * we'll figure out the rest from the vma information. + * + * NOTE! Some drivers might want to tweak vma->vm_page_prot first to get + * whatever write-combining details or similar. + * + * Return: %0 on success, negative error code otherwise. + */ +int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len) +{ + unsigned long vm_len, pfn, pages; + + /* Check that the physical memory area passed in looks valid */ + if (start + len < start) + return -EINVAL; + /* + * You *really* shouldn't map things that aren't page-aligned, + * but we've historically allowed it because IO memory might + * just have smaller alignment. + */ + len += start & ~PAGE_MASK; + pfn = start >> PAGE_SHIFT; + pages = (len + ~PAGE_MASK) >> PAGE_SHIFT; + if (pfn + pages < pfn) + return -EINVAL; + + /* We start the mapping 'vm_pgoff' pages into the area */ + if (vma->vm_pgoff > pages) + return -EINVAL; + pfn += vma->vm_pgoff; + pages -= vma->vm_pgoff; + + /* Can we fit all of the mapping? */ + vm_len = vma->vm_end - vma->vm_start; + if (vm_len >> PAGE_SHIFT > pages) + return -EINVAL; + + /* Ok, let it rip */ + return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot); +} +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, bool create, + pgtbl_mod_mask *mask) +{ + pte_t *pte, *mapped_pte; + int err = 0; + spinlock_t *ptl; + + if (create) { + mapped_pte = pte = (mm == &init_mm) ? + pte_alloc_kernel_track(pmd, addr, mask) : + pte_alloc_map_lock(mm, pmd, addr, &ptl); + if (!pte) + return -ENOMEM; + } else { + mapped_pte = 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(); + + if (fn) { + do { + if (create || !pte_none(*pte)) { + err = fn(pte++, addr, data); + if (err) + break; + } + } while (addr += PAGE_SIZE, addr != end); + } + *mask |= PGTBL_PTE_MODIFIED; + + arch_leave_lazy_mmu_mode(); + + if (mm != &init_mm) + pte_unmap_unlock(mapped_pte, ptl); + return err; +} + +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, bool create, + pgtbl_mod_mask *mask) +{ + pmd_t *pmd; + unsigned long next; + int err = 0; + + BUG_ON(pud_huge(*pud)); + + if (create) { + pmd = pmd_alloc_track(mm, pud, addr, mask); + if (!pmd) + return -ENOMEM; + } else { + pmd = pmd_offset(pud, addr); + } + do { + next = pmd_addr_end(addr, end); + if (pmd_none(*pmd) && !create) + continue; + if (WARN_ON_ONCE(pmd_leaf(*pmd))) + return -EINVAL; + if (!pmd_none(*pmd) && WARN_ON_ONCE(pmd_bad(*pmd))) { + if (!create) + continue; + pmd_clear_bad(pmd); + } + err = apply_to_pte_range(mm, pmd, addr, next, + fn, data, create, mask); + 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, bool create, + pgtbl_mod_mask *mask) +{ + pud_t *pud; + unsigned long next; + int err = 0; + + if (create) { + pud = pud_alloc_track(mm, p4d, addr, mask); + if (!pud) + return -ENOMEM; + } else { + pud = pud_offset(p4d, addr); + } + do { + next = pud_addr_end(addr, end); + if (pud_none(*pud) && !create) + continue; + if (WARN_ON_ONCE(pud_leaf(*pud))) + return -EINVAL; + if (!pud_none(*pud) && WARN_ON_ONCE(pud_bad(*pud))) { + if (!create) + continue; + pud_clear_bad(pud); + } + err = apply_to_pmd_range(mm, pud, addr, next, + fn, data, create, mask); + 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, bool create, + pgtbl_mod_mask *mask) +{ + p4d_t *p4d; + unsigned long next; + int err = 0; + + if (create) { + p4d = p4d_alloc_track(mm, pgd, addr, mask); + if (!p4d) + return -ENOMEM; + } else { + p4d = p4d_offset(pgd, addr); + } + do { + next = p4d_addr_end(addr, end); + if (p4d_none(*p4d) && !create) + continue; + if (WARN_ON_ONCE(p4d_leaf(*p4d))) + return -EINVAL; + if (!p4d_none(*p4d) && WARN_ON_ONCE(p4d_bad(*p4d))) { + if (!create) + continue; + p4d_clear_bad(p4d); + } + err = apply_to_pud_range(mm, p4d, addr, next, + fn, data, create, mask); + 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 start = addr, next; + unsigned long end = addr + size; + pgtbl_mod_mask mask = 0; + int err = 0; + + if (WARN_ON(addr >= end)) + return -EINVAL; + + pgd = pgd_offset(mm, addr); + do { + next = pgd_addr_end(addr, end); + if (pgd_none(*pgd) && !create) + continue; + if (WARN_ON_ONCE(pgd_leaf(*pgd))) + return -EINVAL; + if (!pgd_none(*pgd) && WARN_ON_ONCE(pgd_bad(*pgd))) { + if (!create) + continue; + pgd_clear_bad(pgd); + } + err = apply_to_p4d_range(mm, pgd, addr, next, + fn, data, create, &mask); + if (err) + break; + } while (pgd++, addr = next, addr != end); + + if (mask & ARCH_PAGE_TABLE_SYNC_MASK) + arch_sync_kernel_mappings(start, start + size); + + return err; +} + +/* + * Scan a region of virtual memory, filling in page tables as necessary + * and calling a provided function on each leaf page table. + */ +int apply_to_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, 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 + * or configurations (e.g. i386 with PAE) which might give a mix of unmatched + * parts, do_swap_page must check under lock before unmapping the pte and + * proceeding (but do_wp_page is only called after already making such a check; + * and do_anonymous_page can safely check later on). + */ +static inline int pte_unmap_same(struct vm_fault *vmf) +{ + int same = 1; +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPTION) + if (sizeof(pte_t) > sizeof(unsigned long)) { + spinlock_t *ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); + spin_lock(ptl); + same = pte_same(*vmf->pte, vmf->orig_pte); + spin_unlock(ptl); + } +#endif + pte_unmap(vmf->pte); + vmf->pte = NULL; + return same; +} + +/* + * Return: + * 0: copied succeeded + * -EHWPOISON: copy failed due to hwpoison in source page + * -EAGAIN: copied failed (some other reason) + */ +static inline int __wp_page_copy_user(struct page *dst, struct page *src, + struct vm_fault *vmf) +{ + int ret; + void *kaddr; + void __user *uaddr; + bool locked = false; + struct vm_area_struct *vma = vmf->vma; + struct mm_struct *mm = vma->vm_mm; + unsigned long addr = vmf->address; + + if (likely(src)) { + if (copy_mc_user_highpage(dst, src, addr, vma)) { + memory_failure_queue(page_to_pfn(src), 0); + return -EHWPOISON; + } + return 0; + } + + /* + * If the source page was a PFN mapping, we don't have + * a "struct page" for it. We do a best-effort copy by + * just copying from the original user address. If that + * fails, we just zero-fill it. Live with it. + */ + kaddr = kmap_atomic(dst); + uaddr = (void __user *)(addr & PAGE_MASK); + + /* + * On architectures with software "accessed" bits, we would + * take a double page fault, so mark it accessed here. + */ + if (!arch_has_hw_pte_young() && !pte_young(vmf->orig_pte)) { + pte_t entry; + + vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl); + locked = true; + if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) { + /* + * Other thread has already handled the fault + * and update local tlb only + */ + update_mmu_tlb(vma, addr, vmf->pte); + ret = -EAGAIN; + goto pte_unlock; + } + + entry = pte_mkyoung(vmf->orig_pte); + if (ptep_set_access_flags(vma, addr, vmf->pte, entry, 0)) + update_mmu_cache(vma, addr, vmf->pte); + } + + /* + * This really shouldn't fail, because the page is there + * in the page tables. But it might just be unreadable, + * in which case we just give up and fill the result with + * zeroes. + */ + if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) { + if (locked) + goto warn; + + /* Re-validate under PTL if the page is still mapped */ + vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl); + locked = true; + if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) { + /* The PTE changed under us, update local tlb */ + update_mmu_tlb(vma, addr, vmf->pte); + ret = -EAGAIN; + goto pte_unlock; + } + + /* + * The same page can be mapped back since last copy attempt. + * Try to copy again under PTL. + */ + if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) { + /* + * Give a warn in case there can be some obscure + * use-case + */ +warn: + WARN_ON_ONCE(1); + clear_page(kaddr); + } + } + + ret = 0; + +pte_unlock: + if (locked) + pte_unmap_unlock(vmf->pte, vmf->ptl); + kunmap_atomic(kaddr); + flush_dcache_page(dst); + + return ret; +} + +static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma) +{ + struct file *vm_file = vma->vm_file; + + if (vm_file) + return mapping_gfp_mask(vm_file->f_mapping) | __GFP_FS | __GFP_IO; + + /* + * Special mappings (e.g. VDSO) do not have any file so fake + * a default GFP_KERNEL for them. + */ + return GFP_KERNEL; +} + +/* + * Notify the address space that the page is about to become writable so that + * it can prohibit this or wait for the page to get into an appropriate state. + * + * We do this without the lock held, so that it can sleep if it needs to. + */ +static vm_fault_t do_page_mkwrite(struct vm_fault *vmf) +{ + vm_fault_t ret; + struct page *page = vmf->page; + unsigned int old_flags = vmf->flags; + + vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE; + + if (vmf->vma->vm_file && + IS_SWAPFILE(vmf->vma->vm_file->f_mapping->host)) + return VM_FAULT_SIGBUS; + + ret = vmf->vma->vm_ops->page_mkwrite(vmf); + /* Restore original flags so that caller is not surprised */ + vmf->flags = old_flags; + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) + return ret; + if (unlikely(!(ret & VM_FAULT_LOCKED))) { + lock_page(page); + if (!page->mapping) { + unlock_page(page); + return 0; /* retry */ + } + ret |= VM_FAULT_LOCKED; + } else + VM_BUG_ON_PAGE(!PageLocked(page), page); + return ret; +} + +/* + * Handle dirtying of a page in shared file mapping on a write fault. + * + * The function expects the page to be locked and unlocks it. + */ +static vm_fault_t fault_dirty_shared_page(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + struct address_space *mapping; + struct page *page = vmf->page; + bool dirtied; + bool page_mkwrite = vma->vm_ops && vma->vm_ops->page_mkwrite; + + dirtied = set_page_dirty(page); + VM_BUG_ON_PAGE(PageAnon(page), page); + /* + * Take a local copy of the address_space - page.mapping may be zeroed + * by truncate after unlock_page(). The address_space itself remains + * pinned by vma->vm_file's reference. We rely on unlock_page()'s + * release semantics to prevent the compiler from undoing this copying. + */ + mapping = page_rmapping(page); + unlock_page(page); + + if (!page_mkwrite) + file_update_time(vma->vm_file); + + /* + * Throttle page dirtying rate down to writeback speed. + * + * mapping may be NULL here because some device drivers do not + * set page.mapping but still dirty their pages + * + * Drop the mmap_lock before waiting on IO, if we can. The file + * is pinning the mapping, as per above. + */ + if ((dirtied || page_mkwrite) && mapping) { + struct file *fpin; + + fpin = maybe_unlock_mmap_for_io(vmf, NULL); + balance_dirty_pages_ratelimited(mapping); + if (fpin) { + fput(fpin); + return VM_FAULT_COMPLETED; + } + } + + return 0; +} + +/* + * Handle write page faults for pages that can be reused in the current vma + * + * This can happen either due to the mapping being with the VM_SHARED flag, + * or due to us being the last reference standing to the page. In either + * case, all we need to do here is to mark the page as writable and update + * any related book-keeping. + */ +static inline void wp_page_reuse(struct vm_fault *vmf) + __releases(vmf->ptl) +{ + struct vm_area_struct *vma = vmf->vma; + struct page *page = vmf->page; + pte_t entry; + + VM_BUG_ON(!(vmf->flags & FAULT_FLAG_WRITE)); + VM_BUG_ON(page && PageAnon(page) && !PageAnonExclusive(page)); + + /* + * Clear the pages cpupid information as the existing + * information potentially belongs to a now completely + * unrelated process. + */ + if (page) + page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1); + + flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); + entry = pte_mkyoung(vmf->orig_pte); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1)) + update_mmu_cache(vma, vmf->address, vmf->pte); + pte_unmap_unlock(vmf->pte, vmf->ptl); + count_vm_event(PGREUSE); +} + +/* + * Handle the case of a page which we actually need to copy to a new page, + * either due to COW or unsharing. + * + * Called with mmap_lock locked and the old page referenced, but + * without the ptl held. + * + * High level logic flow: + * + * - Allocate a page, copy the content of the old page to the new one. + * - Handle book keeping and accounting - cgroups, mmu-notifiers, etc. + * - Take the PTL. If the pte changed, bail out and release the allocated page + * - If the pte is still the way we remember it, update the page table and all + * relevant references. This includes dropping the reference the page-table + * held to the old page, as well as updating the rmap. + * - In any case, unlock the PTL and drop the reference we took to the old page. + */ +static vm_fault_t wp_page_copy(struct vm_fault *vmf) +{ + const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE; + struct vm_area_struct *vma = vmf->vma; + struct mm_struct *mm = vma->vm_mm; + struct page *old_page = vmf->page; + struct page *new_page = NULL; + pte_t entry; + int page_copied = 0; + struct mmu_notifier_range range; + int ret; + + delayacct_wpcopy_start(); + + if (unlikely(anon_vma_prepare(vma))) + goto oom; + + if (is_zero_pfn(pte_pfn(vmf->orig_pte))) { + new_page = alloc_zeroed_user_highpage_movable(vma, + vmf->address); + if (!new_page) + goto oom; + } else { + new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, + vmf->address); + if (!new_page) + goto oom; + + ret = __wp_page_copy_user(new_page, old_page, vmf); + if (ret) { + /* + * COW failed, if the fault was solved by other, + * it's fine. If not, userspace would re-fault on + * the same address and we will handle the fault + * from the second attempt. + * The -EHWPOISON case will not be retried. + */ + put_page(new_page); + if (old_page) + put_page(old_page); + + delayacct_wpcopy_end(); + return ret == -EHWPOISON ? VM_FAULT_HWPOISON : 0; + } + kmsan_copy_page_meta(new_page, old_page); + } + + if (mem_cgroup_charge(page_folio(new_page), mm, GFP_KERNEL)) + goto oom_free_new; + cgroup_throttle_swaprate(new_page, GFP_KERNEL); + + __SetPageUptodate(new_page); + + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, + vmf->address & PAGE_MASK, + (vmf->address & PAGE_MASK) + PAGE_SIZE); + mmu_notifier_invalidate_range_start(&range); + + /* + * Re-check the pte - we dropped the lock + */ + vmf->pte = pte_offset_map_lock(mm, vmf->pmd, vmf->address, &vmf->ptl); + if (likely(pte_same(*vmf->pte, vmf->orig_pte))) { + if (old_page) { + if (!PageAnon(old_page)) { + dec_mm_counter_fast(mm, + mm_counter_file(old_page)); + inc_mm_counter_fast(mm, MM_ANONPAGES); + } + } else { + inc_mm_counter_fast(mm, MM_ANONPAGES); + } + flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); + entry = mk_pte(new_page, vma->vm_page_prot); + entry = pte_sw_mkyoung(entry); + if (unlikely(unshare)) { + if (pte_soft_dirty(vmf->orig_pte)) + entry = pte_mksoft_dirty(entry); + if (pte_uffd_wp(vmf->orig_pte)) + entry = pte_mkuffd_wp(entry); + } else { + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + } + + /* + * Clear the pte entry and flush it first, before updating the + * pte with the new entry, to keep TLBs on different CPUs in + * sync. This code used to set the new PTE then flush TLBs, but + * that left a window where the new PTE could be loaded into + * some TLBs while the old PTE remains in others. + */ + ptep_clear_flush_notify(vma, vmf->address, vmf->pte); + page_add_new_anon_rmap(new_page, vma, vmf->address); + lru_cache_add_inactive_or_unevictable(new_page, vma); + /* + * We call the notify macro here because, when using secondary + * mmu page tables (such as kvm shadow page tables), we want the + * new page to be mapped directly into the secondary page table. + */ + BUG_ON(unshare && pte_write(entry)); + set_pte_at_notify(mm, vmf->address, vmf->pte, entry); + update_mmu_cache(vma, vmf->address, vmf->pte); + if (old_page) { + /* + * Only after switching the pte to the new page may + * we remove the mapcount here. Otherwise another + * process may come and find the rmap count decremented + * before the pte is switched to the new page, and + * "reuse" the old page writing into it while our pte + * here still points into it and can be read by other + * threads. + * + * The critical issue is to order this + * page_remove_rmap with the ptp_clear_flush above. + * Those stores are ordered by (if nothing else,) + * the barrier present in the atomic_add_negative + * in page_remove_rmap. + * + * Then the TLB flush in ptep_clear_flush ensures that + * no process can access the old page before the + * decremented mapcount is visible. And the old page + * cannot be reused until after the decremented + * mapcount is visible. So transitively, TLBs to + * old page will be flushed before it can be reused. + */ + page_remove_rmap(old_page, vma, false); + } + + /* Free the old page.. */ + new_page = old_page; + page_copied = 1; + } else { + update_mmu_tlb(vma, vmf->address, vmf->pte); + } + + if (new_page) + put_page(new_page); + + pte_unmap_unlock(vmf->pte, vmf->ptl); + /* + * No need to double call mmu_notifier->invalidate_range() callback as + * the above ptep_clear_flush_notify() did already call it. + */ + mmu_notifier_invalidate_range_only_end(&range); + if (old_page) { + if (page_copied) + free_swap_cache(old_page); + put_page(old_page); + } + + delayacct_wpcopy_end(); + return (page_copied && !unshare) ? VM_FAULT_WRITE : 0; +oom_free_new: + put_page(new_page); +oom: + if (old_page) + put_page(old_page); + + delayacct_wpcopy_end(); + return VM_FAULT_OOM; +} + +/** + * finish_mkwrite_fault - finish page fault for a shared mapping, making PTE + * writeable once the page is prepared + * + * @vmf: structure describing the fault + * + * This function handles all that is needed to finish a write page fault in a + * shared mapping due to PTE being read-only once the mapped page is prepared. + * It handles locking of PTE and modifying it. + * + * The function expects the page to be locked or other protection against + * concurrent faults / writeback (such as DAX radix tree locks). + * + * Return: %0 on success, %VM_FAULT_NOPAGE when PTE got changed before + * we acquired PTE lock. + */ +vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf) +{ + WARN_ON_ONCE(!(vmf->vma->vm_flags & VM_SHARED)); + vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, vmf->address, + &vmf->ptl); + /* + * We might have raced with another page fault while we released the + * pte_offset_map_lock. + */ + if (!pte_same(*vmf->pte, vmf->orig_pte)) { + update_mmu_tlb(vmf->vma, vmf->address, vmf->pte); + pte_unmap_unlock(vmf->pte, vmf->ptl); + return VM_FAULT_NOPAGE; + } + wp_page_reuse(vmf); + return 0; +} + +/* + * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED + * mapping + */ +static vm_fault_t wp_pfn_shared(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + + if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) { + vm_fault_t ret; + + pte_unmap_unlock(vmf->pte, vmf->ptl); + vmf->flags |= FAULT_FLAG_MKWRITE; + ret = vma->vm_ops->pfn_mkwrite(vmf); + if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)) + return ret; + return finish_mkwrite_fault(vmf); + } + wp_page_reuse(vmf); + return VM_FAULT_WRITE; +} + +static vm_fault_t wp_page_shared(struct vm_fault *vmf) + __releases(vmf->ptl) +{ + struct vm_area_struct *vma = vmf->vma; + vm_fault_t ret = VM_FAULT_WRITE; + + get_page(vmf->page); + + if (vma->vm_ops && vma->vm_ops->page_mkwrite) { + vm_fault_t tmp; + + pte_unmap_unlock(vmf->pte, vmf->ptl); + tmp = do_page_mkwrite(vmf); + if (unlikely(!tmp || (tmp & + (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { + put_page(vmf->page); + return tmp; + } + tmp = finish_mkwrite_fault(vmf); + if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) { + unlock_page(vmf->page); + put_page(vmf->page); + return tmp; + } + } else { + wp_page_reuse(vmf); + lock_page(vmf->page); + } + ret |= fault_dirty_shared_page(vmf); + put_page(vmf->page); + + return ret; +} + +/* + * This routine handles present pages, when + * * users try to write to a shared page (FAULT_FLAG_WRITE) + * * GUP wants to take a R/O pin on a possibly shared anonymous page + * (FAULT_FLAG_UNSHARE) + * + * It is done by copying the page to a new address and decrementing the + * shared-page counter for the old page. + * + * Note that this routine assumes that the protection checks have been + * done by the caller (the low-level page fault routine in most cases). + * Thus, with FAULT_FLAG_WRITE, we can safely just mark it writable once we've + * done any necessary COW. + * + * In case of FAULT_FLAG_WRITE, we also mark the page dirty at this point even + * though the page will change only once the write actually happens. This + * avoids a few races, and potentially makes it more efficient. + * + * We enter with non-exclusive mmap_lock (to exclude vma changes, + * but allow concurrent faults), with pte both mapped and locked. + * We return with mmap_lock still held, but pte unmapped and unlocked. + */ +static vm_fault_t do_wp_page(struct vm_fault *vmf) + __releases(vmf->ptl) +{ + const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE; + struct vm_area_struct *vma = vmf->vma; + struct folio *folio; + + VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE)); + VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE)); + + if (likely(!unshare)) { + if (userfaultfd_pte_wp(vma, *vmf->pte)) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + return handle_userfault(vmf, VM_UFFD_WP); + } + + /* + * Userfaultfd write-protect can defer flushes. Ensure the TLB + * is flushed in this case before copying. + */ + if (unlikely(userfaultfd_wp(vmf->vma) && + mm_tlb_flush_pending(vmf->vma->vm_mm))) + flush_tlb_page(vmf->vma, vmf->address); + } + + vmf->page = vm_normal_page(vma, vmf->address, vmf->orig_pte); + if (!vmf->page) { + if (unlikely(unshare)) { + /* No anonymous page -> nothing to do. */ + pte_unmap_unlock(vmf->pte, vmf->ptl); + return 0; + } + + /* + * VM_MIXEDMAP !pfn_valid() case, or VM_SOFTDIRTY clear on a + * VM_PFNMAP VMA. + * + * We should not cow pages in a shared writeable mapping. + * Just mark the pages writable and/or call ops->pfn_mkwrite. + */ + if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) == + (VM_WRITE|VM_SHARED)) + return wp_pfn_shared(vmf); + + pte_unmap_unlock(vmf->pte, vmf->ptl); + return wp_page_copy(vmf); + } + + /* + * Take out anonymous pages first, anonymous shared vmas are + * not dirty accountable. + */ + folio = page_folio(vmf->page); + if (folio_test_anon(folio)) { + /* + * If the page is exclusive to this process we must reuse the + * page without further checks. + */ + if (PageAnonExclusive(vmf->page)) + goto reuse; + + /* + * We have to verify under folio lock: these early checks are + * just an optimization to avoid locking the folio and freeing + * the swapcache if there is little hope that we can reuse. + * + * KSM doesn't necessarily raise the folio refcount. + */ + if (folio_test_ksm(folio) || folio_ref_count(folio) > 3) + goto copy; + if (!folio_test_lru(folio)) + /* + * Note: We cannot easily detect+handle references from + * remote LRU pagevecs or references to LRU folios. + */ + lru_add_drain(); + if (folio_ref_count(folio) > 1 + folio_test_swapcache(folio)) + goto copy; + if (!folio_trylock(folio)) + goto copy; + if (folio_test_swapcache(folio)) + folio_free_swap(folio); + if (folio_test_ksm(folio) || folio_ref_count(folio) != 1) { + folio_unlock(folio); + goto copy; + } + /* + * Ok, we've got the only folio reference from our mapping + * and the folio is locked, it's dark out, and we're wearing + * sunglasses. Hit it. + */ + page_move_anon_rmap(vmf->page, vma); + folio_unlock(folio); +reuse: + if (unlikely(unshare)) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + return 0; + } + wp_page_reuse(vmf); + return VM_FAULT_WRITE; + } else if (unshare) { + /* No anonymous page -> nothing to do. */ + pte_unmap_unlock(vmf->pte, vmf->ptl); + return 0; + } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) == + (VM_WRITE|VM_SHARED))) { + return wp_page_shared(vmf); + } +copy: + /* + * Ok, we need to copy. Oh, well.. + */ + get_page(vmf->page); + + pte_unmap_unlock(vmf->pte, vmf->ptl); +#ifdef CONFIG_KSM + if (PageKsm(vmf->page)) + count_vm_event(COW_KSM); +#endif + return wp_page_copy(vmf); +} + +static void unmap_mapping_range_vma(struct vm_area_struct *vma, + unsigned long start_addr, unsigned long end_addr, + struct zap_details *details) +{ + zap_page_range_single(vma, start_addr, end_addr - start_addr, details); +} + +static inline void unmap_mapping_range_tree(struct rb_root_cached *root, + pgoff_t first_index, + pgoff_t last_index, + struct zap_details *details) +{ + struct vm_area_struct *vma; + pgoff_t vba, vea, zba, zea; + + vma_interval_tree_foreach(vma, root, first_index, last_index) { + vba = vma->vm_pgoff; + vea = vba + vma_pages(vma) - 1; + zba = max(first_index, vba); + zea = min(last_index, vea); + + unmap_mapping_range_vma(vma, + ((zba - vba) << PAGE_SHIFT) + vma->vm_start, + ((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start, + details); + } +} + +/** + * unmap_mapping_folio() - Unmap single folio from processes. + * @folio: The locked folio to be unmapped. + * + * Unmap this folio from any userspace process which still has it mmaped. + * Typically, for efficiency, the range of nearby pages has already been + * unmapped by unmap_mapping_pages() or unmap_mapping_range(). But once + * truncation or invalidation holds the lock on a folio, it may find that + * the page has been remapped again: and then uses unmap_mapping_folio() + * to unmap it finally. + */ +void unmap_mapping_folio(struct folio *folio) +{ + struct address_space *mapping = folio->mapping; + struct zap_details details = { }; + pgoff_t first_index; + pgoff_t last_index; + + VM_BUG_ON(!folio_test_locked(folio)); + + first_index = folio->index; + last_index = folio->index + folio_nr_pages(folio) - 1; + + details.even_cows = false; + details.single_folio = folio; + details.zap_flags = ZAP_FLAG_DROP_MARKER; + + i_mmap_lock_read(mapping); + if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))) + unmap_mapping_range_tree(&mapping->i_mmap, first_index, + last_index, &details); + i_mmap_unlock_read(mapping); +} + +/** + * unmap_mapping_pages() - Unmap pages from processes. + * @mapping: The address space containing pages to be unmapped. + * @start: Index of first page to be unmapped. + * @nr: Number of pages to be unmapped. 0 to unmap to end of file. + * @even_cows: Whether to unmap even private COWed pages. + * + * Unmap the pages in this address space from any userspace process which + * has them mmaped. Generally, you want to remove COWed pages as well when + * a file is being truncated, but not when invalidating pages from the page + * cache. + */ +void unmap_mapping_pages(struct address_space *mapping, pgoff_t start, + pgoff_t nr, bool even_cows) +{ + struct zap_details details = { }; + pgoff_t first_index = start; + pgoff_t last_index = start + nr - 1; + + details.even_cows = even_cows; + if (last_index < first_index) + last_index = ULONG_MAX; + + i_mmap_lock_read(mapping); + if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))) + unmap_mapping_range_tree(&mapping->i_mmap, first_index, + last_index, &details); + i_mmap_unlock_read(mapping); +} +EXPORT_SYMBOL_GPL(unmap_mapping_pages); + +/** + * unmap_mapping_range - unmap the portion of all mmaps in the specified + * address_space corresponding to the specified byte range in the underlying + * file. + * + * @mapping: the address space containing mmaps to be unmapped. + * @holebegin: byte in first page to unmap, relative to the start of + * the underlying file. This will be rounded down to a PAGE_SIZE + * boundary. Note that this is different from truncate_pagecache(), which + * must keep the partial page. In contrast, we must get rid of + * partial pages. + * @holelen: size of prospective hole in bytes. This will be rounded + * up to a PAGE_SIZE boundary. A holelen of zero truncates to the + * end of the file. + * @even_cows: 1 when truncating a file, unmap even private COWed pages; + * but 0 when invalidating pagecache, don't throw away private data. + */ +void unmap_mapping_range(struct address_space *mapping, + loff_t const holebegin, loff_t const holelen, int even_cows) +{ + pgoff_t hba = (pgoff_t)(holebegin) >> PAGE_SHIFT; + pgoff_t hlen = ((pgoff_t)(holelen) + PAGE_SIZE - 1) >> PAGE_SHIFT; + + /* Check for overflow. */ + if (sizeof(holelen) > sizeof(hlen)) { + long long holeend = + (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (holeend & ~(long long)ULONG_MAX) + hlen = ULONG_MAX - hba + 1; + } + + unmap_mapping_pages(mapping, hba, hlen, even_cows); +} +EXPORT_SYMBOL(unmap_mapping_range); + +/* + * Restore a potential device exclusive pte to a working pte entry + */ +static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf) +{ + struct folio *folio = page_folio(vmf->page); + struct vm_area_struct *vma = vmf->vma; + struct mmu_notifier_range range; + + /* + * We need a reference to lock the folio because we don't hold + * the PTL so a racing thread can remove the device-exclusive + * entry and unmap it. If the folio is free the entry must + * have been removed already. If it happens to have already + * been re-allocated after being freed all we do is lock and + * unlock it. + */ + if (!folio_try_get(folio)) + return 0; + + if (!folio_lock_or_retry(folio, vma->vm_mm, vmf->flags)) { + folio_put(folio); + return VM_FAULT_RETRY; + } + mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, vma, + vma->vm_mm, vmf->address & PAGE_MASK, + (vmf->address & PAGE_MASK) + PAGE_SIZE, NULL); + mmu_notifier_invalidate_range_start(&range); + + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, + &vmf->ptl); + if (likely(pte_same(*vmf->pte, vmf->orig_pte))) + restore_exclusive_pte(vma, vmf->page, vmf->address, vmf->pte); + + pte_unmap_unlock(vmf->pte, vmf->ptl); + folio_unlock(folio); + folio_put(folio); + + mmu_notifier_invalidate_range_end(&range); + return 0; +} + +static inline bool should_try_to_free_swap(struct folio *folio, + struct vm_area_struct *vma, + unsigned int fault_flags) +{ + if (!folio_test_swapcache(folio)) + return false; + if (mem_cgroup_swap_full(folio) || (vma->vm_flags & VM_LOCKED) || + folio_test_mlocked(folio)) + return true; + /* + * If we want to map a page that's in the swapcache writable, we + * have to detect via the refcount if we're really the exclusive + * user. Try freeing the swapcache to get rid of the swapcache + * reference only in case it's likely that we'll be the exlusive user. + */ + return (fault_flags & FAULT_FLAG_WRITE) && !folio_test_ksm(folio) && + folio_ref_count(folio) == 2; +} + +static vm_fault_t pte_marker_clear(struct vm_fault *vmf) +{ + vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, + vmf->address, &vmf->ptl); + /* + * Be careful so that we will only recover a special uffd-wp pte into a + * none pte. Otherwise it means the pte could have changed, so retry. + */ + if (is_pte_marker(*vmf->pte)) + pte_clear(vmf->vma->vm_mm, vmf->address, vmf->pte); + pte_unmap_unlock(vmf->pte, vmf->ptl); + return 0; +} + +/* + * This is actually a page-missing access, but with uffd-wp special pte + * installed. It means this pte was wr-protected before being unmapped. + */ +static vm_fault_t pte_marker_handle_uffd_wp(struct vm_fault *vmf) +{ + /* + * Just in case there're leftover special ptes even after the region + * got unregistered - we can simply clear them. We can also do that + * proactively when e.g. when we do UFFDIO_UNREGISTER upon some uffd-wp + * ranges, but it should be more efficient to be done lazily here. + */ + if (unlikely(!userfaultfd_wp(vmf->vma) || vma_is_anonymous(vmf->vma))) + return pte_marker_clear(vmf); + + /* do_fault() can handle pte markers too like none pte */ + return do_fault(vmf); +} + +static vm_fault_t handle_pte_marker(struct vm_fault *vmf) +{ + swp_entry_t entry = pte_to_swp_entry(vmf->orig_pte); + unsigned long marker = pte_marker_get(entry); + + /* + * PTE markers should always be with file-backed memories, and the + * marker should never be empty. If anything weird happened, the best + * thing to do is to kill the process along with its mm. + */ + if (WARN_ON_ONCE(vma_is_anonymous(vmf->vma) || !marker)) + return VM_FAULT_SIGBUS; + + if (pte_marker_entry_uffd_wp(entry)) + return pte_marker_handle_uffd_wp(vmf); + + /* This is an unknown pte marker */ + return VM_FAULT_SIGBUS; +} + +/* + * We enter with non-exclusive mmap_lock (to exclude vma changes, + * but allow concurrent faults), and pte mapped but not yet locked. + * We return with pte unmapped and unlocked. + * + * We return with the mmap_lock locked or unlocked in the same cases + * as does filemap_fault(). + */ +vm_fault_t do_swap_page(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + struct folio *swapcache, *folio = NULL; + struct page *page; + struct swap_info_struct *si = NULL; + rmap_t rmap_flags = RMAP_NONE; + bool exclusive = false; + swp_entry_t entry; + pte_t pte; + int locked; + vm_fault_t ret = 0; + void *shadow = NULL; + + if (!pte_unmap_same(vmf)) + goto out; + + entry = pte_to_swp_entry(vmf->orig_pte); + if (unlikely(non_swap_entry(entry))) { + if (is_migration_entry(entry)) { + migration_entry_wait(vma->vm_mm, vmf->pmd, + vmf->address); + } else if (is_device_exclusive_entry(entry)) { + vmf->page = pfn_swap_entry_to_page(entry); + ret = remove_device_exclusive_entry(vmf); + } else if (is_device_private_entry(entry)) { + vmf->page = pfn_swap_entry_to_page(entry); + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, + vmf->address, &vmf->ptl); + if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) { + spin_unlock(vmf->ptl); + goto out; + } + + /* + * Get a page reference while we know the page can't be + * freed. + */ + get_page(vmf->page); + pte_unmap_unlock(vmf->pte, vmf->ptl); + ret = vmf->page->pgmap->ops->migrate_to_ram(vmf); + put_page(vmf->page); + } else if (is_hwpoison_entry(entry)) { + ret = VM_FAULT_HWPOISON; + } else if (is_swapin_error_entry(entry)) { + ret = VM_FAULT_SIGBUS; + } else if (is_pte_marker_entry(entry)) { + ret = handle_pte_marker(vmf); + } else { + print_bad_pte(vma, vmf->address, vmf->orig_pte, NULL); + ret = VM_FAULT_SIGBUS; + } + goto out; + } + + /* Prevent swapoff from happening to us. */ + si = get_swap_device(entry); + if (unlikely(!si)) + goto out; + + folio = swap_cache_get_folio(entry, vma, vmf->address); + if (folio) + page = folio_file_page(folio, swp_offset(entry)); + swapcache = folio; + + if (!folio) { + if (data_race(si->flags & SWP_SYNCHRONOUS_IO) && + __swap_count(entry) == 1) { + /* skip swapcache */ + folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, + vma, vmf->address, false); + page = &folio->page; + if (folio) { + __folio_set_locked(folio); + __folio_set_swapbacked(folio); + + if (mem_cgroup_swapin_charge_folio(folio, + vma->vm_mm, GFP_KERNEL, + entry)) { + ret = VM_FAULT_OOM; + goto out_page; + } + mem_cgroup_swapin_uncharge_swap(entry); + + shadow = get_shadow_from_swap_cache(entry); + if (shadow) + workingset_refault(folio, shadow); + + folio_add_lru(folio); + + /* To provide entry to swap_readpage() */ + folio_set_swap_entry(folio, entry); + swap_readpage(page, true, NULL); + folio->private = NULL; + } + } else { + page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, + vmf); + if (page) + folio = page_folio(page); + swapcache = folio; + } + + if (!folio) { + /* + * Back out if somebody else faulted in this pte + * while we released the pte lock. + */ + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, + vmf->address, &vmf->ptl); + if (likely(pte_same(*vmf->pte, vmf->orig_pte))) + ret = VM_FAULT_OOM; + goto unlock; + } + + /* Had to read the page from swap area: Major fault */ + ret = VM_FAULT_MAJOR; + count_vm_event(PGMAJFAULT); + count_memcg_event_mm(vma->vm_mm, PGMAJFAULT); + } else if (PageHWPoison(page)) { + /* + * hwpoisoned dirty swapcache pages are kept for killing + * owner processes (which may be unknown at hwpoison time) + */ + ret = VM_FAULT_HWPOISON; + goto out_release; + } + + locked = folio_lock_or_retry(folio, vma->vm_mm, vmf->flags); + + if (!locked) { + ret |= VM_FAULT_RETRY; + goto out_release; + } + + if (swapcache) { + /* + * Make sure folio_free_swap() or swapoff did not release the + * swapcache from under us. The page pin, and pte_same test + * below, are not enough to exclude that. Even if it is still + * swapcache, we need to check that the page's swap has not + * changed. + */ + if (unlikely(!folio_test_swapcache(folio) || + page_private(page) != entry.val)) + goto out_page; + + /* + * KSM sometimes has to copy on read faults, for example, if + * page->index of !PageKSM() pages would be nonlinear inside the + * anon VMA -- PageKSM() is lost on actual swapout. + */ + page = ksm_might_need_to_copy(page, vma, vmf->address); + if (unlikely(!page)) { + ret = VM_FAULT_OOM; + goto out_page; + } + folio = page_folio(page); + + /* + * If we want to map a page that's in the swapcache writable, we + * have to detect via the refcount if we're really the exclusive + * owner. Try removing the extra reference from the local LRU + * pagevecs if required. + */ + if ((vmf->flags & FAULT_FLAG_WRITE) && folio == swapcache && + !folio_test_ksm(folio) && !folio_test_lru(folio)) + lru_add_drain(); + } + + cgroup_throttle_swaprate(page, GFP_KERNEL); + + /* + * Back out if somebody else already faulted in this pte. + */ + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, + &vmf->ptl); + if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) + goto out_nomap; + + if (unlikely(!folio_test_uptodate(folio))) { + ret = VM_FAULT_SIGBUS; + goto out_nomap; + } + + /* + * PG_anon_exclusive reuses PG_mappedtodisk for anon pages. A swap pte + * must never point at an anonymous page in the swapcache that is + * PG_anon_exclusive. Sanity check that this holds and especially, that + * no filesystem set PG_mappedtodisk on a page in the swapcache. Sanity + * check after taking the PT lock and making sure that nobody + * concurrently faulted in this page and set PG_anon_exclusive. + */ + BUG_ON(!folio_test_anon(folio) && folio_test_mappedtodisk(folio)); + BUG_ON(folio_test_anon(folio) && PageAnonExclusive(page)); + + /* + * Check under PT lock (to protect against concurrent fork() sharing + * the swap entry concurrently) for certainly exclusive pages. + */ + if (!folio_test_ksm(folio)) { + /* + * Note that pte_swp_exclusive() == false for architectures + * without __HAVE_ARCH_PTE_SWP_EXCLUSIVE. + */ + exclusive = pte_swp_exclusive(vmf->orig_pte); + if (folio != swapcache) { + /* + * We have a fresh page that is not exposed to the + * swapcache -> certainly exclusive. + */ + exclusive = true; + } else if (exclusive && folio_test_writeback(folio) && + data_race(si->flags & SWP_STABLE_WRITES)) { + /* + * This is tricky: not all swap backends support + * concurrent page modifications while under writeback. + * + * So if we stumble over such a page in the swapcache + * we must not set the page exclusive, otherwise we can + * map it writable without further checks and modify it + * while still under writeback. + * + * For these problematic swap backends, simply drop the + * exclusive marker: this is perfectly fine as we start + * writeback only if we fully unmapped the page and + * there are no unexpected references on the page after + * unmapping succeeded. After fully unmapped, no + * further GUP references (FOLL_GET and FOLL_PIN) can + * appear, so dropping the exclusive marker and mapping + * it only R/O is fine. + */ + exclusive = false; + } + } + + /* + * Some architectures may have to restore extra metadata to the page + * when reading from swap. This metadata may be indexed by swap entry + * so this must be called before swap_free(). + */ + arch_swap_restore(entry, folio); + + /* + * Remove the swap entry and conditionally try to free up the swapcache. + * We're already holding a reference on the page but haven't mapped it + * yet. + */ + swap_free(entry); + if (should_try_to_free_swap(folio, vma, vmf->flags)) + folio_free_swap(folio); + + inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES); + dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS); + pte = mk_pte(page, vma->vm_page_prot); + + /* + * Same logic as in do_wp_page(); however, optimize for pages that are + * certainly not shared either because we just allocated them without + * exposing them to the swapcache or because the swap entry indicates + * exclusivity. + */ + if (!folio_test_ksm(folio) && + (exclusive || folio_ref_count(folio) == 1)) { + if (vmf->flags & FAULT_FLAG_WRITE) { + pte = maybe_mkwrite(pte_mkdirty(pte), vma); + vmf->flags &= ~FAULT_FLAG_WRITE; + ret |= VM_FAULT_WRITE; + } + rmap_flags |= RMAP_EXCLUSIVE; + } + flush_icache_page(vma, page); + if (pte_swp_soft_dirty(vmf->orig_pte)) + pte = pte_mksoft_dirty(pte); + if (pte_swp_uffd_wp(vmf->orig_pte)) { + pte = pte_mkuffd_wp(pte); + pte = pte_wrprotect(pte); + } + vmf->orig_pte = pte; + + /* ksm created a completely new copy */ + if (unlikely(folio != swapcache && swapcache)) { + page_add_new_anon_rmap(page, vma, vmf->address); + folio_add_lru_vma(folio, vma); + } else { + page_add_anon_rmap(page, vma, vmf->address, rmap_flags); + } + + VM_BUG_ON(!folio_test_anon(folio) || + (pte_write(pte) && !PageAnonExclusive(page))); + set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte); + arch_do_swap_page(vma->vm_mm, vma, vmf->address, pte, vmf->orig_pte); + + folio_unlock(folio); + if (folio != swapcache && swapcache) { + /* + * Hold the lock to avoid the swap entry to be reused + * until we take the PT lock for the pte_same() check + * (to avoid false positives from pte_same). For + * further safety release the lock after the swap_free + * so that the swap count won't change under a + * parallel locked swapcache. + */ + folio_unlock(swapcache); + folio_put(swapcache); + } + + if (vmf->flags & FAULT_FLAG_WRITE) { + ret |= do_wp_page(vmf); + if (ret & VM_FAULT_ERROR) + ret &= VM_FAULT_ERROR; + goto out; + } + + /* No need to invalidate - it was non-present before */ + update_mmu_cache(vma, vmf->address, vmf->pte); +unlock: + pte_unmap_unlock(vmf->pte, vmf->ptl); +out: + if (si) + put_swap_device(si); + return ret; +out_nomap: + pte_unmap_unlock(vmf->pte, vmf->ptl); +out_page: + folio_unlock(folio); +out_release: + folio_put(folio); + if (folio != swapcache && swapcache) { + folio_unlock(swapcache); + folio_put(swapcache); + } + if (si) + put_swap_device(si); + return ret; +} + +/* + * We enter with non-exclusive mmap_lock (to exclude vma changes, + * but allow concurrent faults), and pte mapped but not yet locked. + * We return with mmap_lock still held, but pte unmapped and unlocked. + */ +static vm_fault_t do_anonymous_page(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + struct page *page; + vm_fault_t ret = 0; + pte_t entry; + + /* File mapping without ->vm_ops ? */ + if (vma->vm_flags & VM_SHARED) + return VM_FAULT_SIGBUS; + + /* + * Use pte_alloc() instead of pte_alloc_map(). We can't run + * pte_offset_map() on pmds where a huge pmd might be created + * from a different thread. + * + * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when + * parallel threads are excluded by other means. + * + * Here we only have mmap_read_lock(mm). + */ + if (pte_alloc(vma->vm_mm, vmf->pmd)) + return VM_FAULT_OOM; + + /* See comment in handle_pte_fault() */ + if (unlikely(pmd_trans_unstable(vmf->pmd))) + return 0; + + /* Use the zero-page for reads */ + if (!(vmf->flags & FAULT_FLAG_WRITE) && + !mm_forbids_zeropage(vma->vm_mm)) { + entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address), + vma->vm_page_prot)); + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, + vmf->address, &vmf->ptl); + if (!pte_none(*vmf->pte)) { + update_mmu_tlb(vma, vmf->address, vmf->pte); + goto unlock; + } + ret = check_stable_address_space(vma->vm_mm); + if (ret) + goto unlock; + /* Deliver the page fault to userland, check inside PT lock */ + if (userfaultfd_missing(vma)) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + return handle_userfault(vmf, VM_UFFD_MISSING); + } + goto setpte; + } + + /* Allocate our own private page. */ + if (unlikely(anon_vma_prepare(vma))) + goto oom; + page = alloc_zeroed_user_highpage_movable(vma, vmf->address); + if (!page) + goto oom; + + if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL)) + goto oom_free_page; + cgroup_throttle_swaprate(page, GFP_KERNEL); + + /* + * The memory barrier inside __SetPageUptodate makes sure that + * preceding stores to the page contents become visible before + * the set_pte_at() write. + */ + __SetPageUptodate(page); + + entry = mk_pte(page, vma->vm_page_prot); + entry = pte_sw_mkyoung(entry); + if (vma->vm_flags & VM_WRITE) + entry = pte_mkwrite(pte_mkdirty(entry)); + + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, + &vmf->ptl); + if (!pte_none(*vmf->pte)) { + update_mmu_tlb(vma, vmf->address, vmf->pte); + goto release; + } + + ret = check_stable_address_space(vma->vm_mm); + if (ret) + goto release; + + /* Deliver the page fault to userland, check inside PT lock */ + if (userfaultfd_missing(vma)) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + put_page(page); + return handle_userfault(vmf, VM_UFFD_MISSING); + } + + inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES); + page_add_new_anon_rmap(page, vma, vmf->address); + lru_cache_add_inactive_or_unevictable(page, vma); +setpte: + set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry); + + /* No need to invalidate - it was non-present before */ + update_mmu_cache(vma, vmf->address, vmf->pte); +unlock: + pte_unmap_unlock(vmf->pte, vmf->ptl); + return ret; +release: + put_page(page); + goto unlock; +oom_free_page: + put_page(page); +oom: + return VM_FAULT_OOM; +} + +/* + * The mmap_lock must have been held on entry, and may have been + * released depending on flags and vma->vm_ops->fault() return value. + * See filemap_fault() and __lock_page_retry(). + */ +static vm_fault_t __do_fault(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + vm_fault_t ret; + + /* + * Preallocate pte before we take page_lock because this might lead to + * deadlocks for memcg reclaim which waits for pages under writeback: + * lock_page(A) + * SetPageWriteback(A) + * unlock_page(A) + * lock_page(B) + * lock_page(B) + * pte_alloc_one + * shrink_page_list + * wait_on_page_writeback(A) + * SetPageWriteback(B) + * unlock_page(B) + * # flush A, B to clear the writeback + */ + if (pmd_none(*vmf->pmd) && !vmf->prealloc_pte) { + vmf->prealloc_pte = pte_alloc_one(vma->vm_mm); + if (!vmf->prealloc_pte) + return VM_FAULT_OOM; + } + + ret = vma->vm_ops->fault(vmf); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | + VM_FAULT_DONE_COW))) + return ret; + + if (unlikely(PageHWPoison(vmf->page))) { + struct page *page = vmf->page; + vm_fault_t poisonret = VM_FAULT_HWPOISON; + if (ret & VM_FAULT_LOCKED) { + if (page_mapped(page)) + unmap_mapping_pages(page_mapping(page), + page->index, 1, false); + /* Retry if a clean page was removed from the cache. */ + if (invalidate_inode_page(page)) + poisonret = VM_FAULT_NOPAGE; + unlock_page(page); + } + put_page(page); + vmf->page = NULL; + return poisonret; + } + + if (unlikely(!(ret & VM_FAULT_LOCKED))) + lock_page(vmf->page); + else + VM_BUG_ON_PAGE(!PageLocked(vmf->page), vmf->page); + + return ret; +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static void deposit_prealloc_pte(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + + pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, vmf->prealloc_pte); + /* + * We are going to consume the prealloc table, + * count that as nr_ptes. + */ + mm_inc_nr_ptes(vma->vm_mm); + vmf->prealloc_pte = NULL; +} + +vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page) +{ + struct vm_area_struct *vma = vmf->vma; + bool write = vmf->flags & FAULT_FLAG_WRITE; + unsigned long haddr = vmf->address & HPAGE_PMD_MASK; + pmd_t entry; + int i; + vm_fault_t ret = VM_FAULT_FALLBACK; + + if (!transhuge_vma_suitable(vma, haddr)) + return ret; + + page = compound_head(page); + if (compound_order(page) != HPAGE_PMD_ORDER) + return ret; + + /* + * Just backoff if any subpage of a THP is corrupted otherwise + * the corrupted page may mapped by PMD silently to escape the + * check. This kind of THP just can be PTE mapped. Access to + * the corrupted subpage should trigger SIGBUS as expected. + */ + if (unlikely(PageHasHWPoisoned(page))) + return ret; + + /* + * Archs like ppc64 need additional space to store information + * related to pte entry. Use the preallocated table for that. + */ + if (arch_needs_pgtable_deposit() && !vmf->prealloc_pte) { + vmf->prealloc_pte = pte_alloc_one(vma->vm_mm); + if (!vmf->prealloc_pte) + return VM_FAULT_OOM; + } + + vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); + if (unlikely(!pmd_none(*vmf->pmd))) + goto out; + + for (i = 0; i < HPAGE_PMD_NR; i++) + flush_icache_page(vma, page + i); + + entry = mk_huge_pmd(page, vma->vm_page_prot); + if (write) + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + + add_mm_counter(vma->vm_mm, mm_counter_file(page), HPAGE_PMD_NR); + page_add_file_rmap(page, vma, true); + + /* + * deposit and withdraw with pmd lock held + */ + if (arch_needs_pgtable_deposit()) + deposit_prealloc_pte(vmf); + + set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); + + update_mmu_cache_pmd(vma, haddr, vmf->pmd); + + /* fault is handled */ + ret = 0; + count_vm_event(THP_FILE_MAPPED); +out: + spin_unlock(vmf->ptl); + return ret; +} +#else +vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page) +{ + return VM_FAULT_FALLBACK; +} +#endif + +void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr) +{ + struct vm_area_struct *vma = vmf->vma; + bool uffd_wp = pte_marker_uffd_wp(vmf->orig_pte); + bool write = vmf->flags & FAULT_FLAG_WRITE; + bool prefault = vmf->address != addr; + pte_t entry; + + flush_icache_page(vma, page); + entry = mk_pte(page, vma->vm_page_prot); + + if (prefault && arch_wants_old_prefaulted_pte()) + entry = pte_mkold(entry); + else + entry = pte_sw_mkyoung(entry); + + if (write) + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + if (unlikely(uffd_wp)) + entry = pte_mkuffd_wp(pte_wrprotect(entry)); + /* copy-on-write page */ + if (write && !(vma->vm_flags & VM_SHARED)) { + inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES); + page_add_new_anon_rmap(page, vma, addr); + lru_cache_add_inactive_or_unevictable(page, vma); + } else { + inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page)); + page_add_file_rmap(page, vma, false); + } + set_pte_at(vma->vm_mm, addr, vmf->pte, entry); +} + +static bool vmf_pte_changed(struct vm_fault *vmf) +{ + if (vmf->flags & FAULT_FLAG_ORIG_PTE_VALID) + return !pte_same(*vmf->pte, vmf->orig_pte); + + return !pte_none(*vmf->pte); +} + +/** + * finish_fault - finish page fault once we have prepared the page to fault + * + * @vmf: structure describing the fault + * + * This function handles all that is needed to finish a page fault once the + * page to fault in is prepared. It handles locking of PTEs, inserts PTE for + * given page, adds reverse page mapping, handles memcg charges and LRU + * addition. + * + * The function expects the page to be locked and on success it consumes a + * reference of a page being mapped (for the PTE which maps it). + * + * Return: %0 on success, %VM_FAULT_ code in case of error. + */ +vm_fault_t finish_fault(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + struct page *page; + vm_fault_t ret; + + /* Did we COW the page? */ + if ((vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) + page = vmf->cow_page; + else + page = vmf->page; + + /* + * check even for read faults because we might have lost our CoWed + * page + */ + if (!(vma->vm_flags & VM_SHARED)) { + ret = check_stable_address_space(vma->vm_mm); + if (ret) + return ret; + } + + if (pmd_none(*vmf->pmd)) { + if (PageTransCompound(page)) { + ret = do_set_pmd(vmf, page); + if (ret != VM_FAULT_FALLBACK) + return ret; + } + + if (vmf->prealloc_pte) + pmd_install(vma->vm_mm, vmf->pmd, &vmf->prealloc_pte); + else if (unlikely(pte_alloc(vma->vm_mm, vmf->pmd))) + return VM_FAULT_OOM; + } + + /* + * See comment in handle_pte_fault() for how this scenario happens, we + * need to return NOPAGE so that we drop this page. + */ + if (pmd_devmap_trans_unstable(vmf->pmd)) + return VM_FAULT_NOPAGE; + + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, + vmf->address, &vmf->ptl); + + /* Re-check under ptl */ + if (likely(!vmf_pte_changed(vmf))) { + do_set_pte(vmf, page, vmf->address); + + /* no need to invalidate: a not-present page won't be cached */ + update_mmu_cache(vma, vmf->address, vmf->pte); + + ret = 0; + } else { + update_mmu_tlb(vma, vmf->address, vmf->pte); + ret = VM_FAULT_NOPAGE; + } + + pte_unmap_unlock(vmf->pte, vmf->ptl); + return ret; +} + +static unsigned long fault_around_bytes __read_mostly = + rounddown_pow_of_two(65536); + +#ifdef CONFIG_DEBUG_FS +static int fault_around_bytes_get(void *data, u64 *val) +{ + *val = fault_around_bytes; + return 0; +} + +/* + * fault_around_bytes must be rounded down to the nearest page order as it's + * what do_fault_around() expects to see. + */ +static int fault_around_bytes_set(void *data, u64 val) +{ + if (val / PAGE_SIZE > PTRS_PER_PTE) + return -EINVAL; + if (val > PAGE_SIZE) + fault_around_bytes = rounddown_pow_of_two(val); + else + fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */ + return 0; +} +DEFINE_DEBUGFS_ATTRIBUTE(fault_around_bytes_fops, + fault_around_bytes_get, fault_around_bytes_set, "%llu\n"); + +static int __init fault_around_debugfs(void) +{ + debugfs_create_file_unsafe("fault_around_bytes", 0644, NULL, NULL, + &fault_around_bytes_fops); + return 0; +} +late_initcall(fault_around_debugfs); +#endif + +/* + * do_fault_around() tries to map few pages around the fault address. The hope + * is that the pages will be needed soon and this will lower the number of + * faults to handle. + * + * It uses vm_ops->map_pages() to map the pages, which skips the page if it's + * not ready to be mapped: not up-to-date, locked, etc. + * + * This function doesn't cross the VMA boundaries, in order to call map_pages() + * only once. + * + * fault_around_bytes defines how many bytes we'll try to map. + * do_fault_around() expects it to be set to a power of two less than or equal + * to PTRS_PER_PTE. + * + * The virtual address of the area that we map is naturally aligned to + * fault_around_bytes rounded down to the machine page size + * (and therefore to page order). This way it's easier to guarantee + * that we don't cross page table boundaries. + */ +static vm_fault_t do_fault_around(struct vm_fault *vmf) +{ + unsigned long address = vmf->address, nr_pages, mask; + pgoff_t start_pgoff = vmf->pgoff; + pgoff_t end_pgoff; + int off; + + nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT; + mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK; + + address = max(address & mask, vmf->vma->vm_start); + off = ((vmf->address - address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1); + start_pgoff -= off; + + /* + * end_pgoff is either the end of the page table, the end of + * the vma or nr_pages from start_pgoff, depending what is nearest. + */ + end_pgoff = start_pgoff - + ((address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) + + PTRS_PER_PTE - 1; + end_pgoff = min3(end_pgoff, vma_pages(vmf->vma) + vmf->vma->vm_pgoff - 1, + start_pgoff + nr_pages - 1); + + if (pmd_none(*vmf->pmd)) { + vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm); + if (!vmf->prealloc_pte) + return VM_FAULT_OOM; + } + + return vmf->vma->vm_ops->map_pages(vmf, start_pgoff, end_pgoff); +} + +/* Return true if we should do read fault-around, false otherwise */ +static inline bool should_fault_around(struct vm_fault *vmf) +{ + /* No ->map_pages? No way to fault around... */ + if (!vmf->vma->vm_ops->map_pages) + return false; + + if (uffd_disable_fault_around(vmf->vma)) + return false; + + return fault_around_bytes >> PAGE_SHIFT > 1; +} + +static vm_fault_t do_read_fault(struct vm_fault *vmf) +{ + vm_fault_t ret = 0; + + /* + * Let's call ->map_pages() first and use ->fault() as fallback + * if page by the offset is not ready to be mapped (cold cache or + * something). + */ + if (should_fault_around(vmf)) { + ret = do_fault_around(vmf); + if (ret) + return ret; + } + + ret = __do_fault(vmf); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) + return ret; + + ret |= finish_fault(vmf); + unlock_page(vmf->page); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) + put_page(vmf->page); + return ret; +} + +static vm_fault_t do_cow_fault(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + vm_fault_t ret; + + if (unlikely(anon_vma_prepare(vma))) + return VM_FAULT_OOM; + + vmf->cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address); + if (!vmf->cow_page) + return VM_FAULT_OOM; + + if (mem_cgroup_charge(page_folio(vmf->cow_page), vma->vm_mm, + GFP_KERNEL)) { + put_page(vmf->cow_page); + return VM_FAULT_OOM; + } + cgroup_throttle_swaprate(vmf->cow_page, GFP_KERNEL); + + ret = __do_fault(vmf); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) + goto uncharge_out; + if (ret & VM_FAULT_DONE_COW) + return ret; + + copy_user_highpage(vmf->cow_page, vmf->page, vmf->address, vma); + __SetPageUptodate(vmf->cow_page); + + ret |= finish_fault(vmf); + unlock_page(vmf->page); + put_page(vmf->page); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) + goto uncharge_out; + return ret; +uncharge_out: + put_page(vmf->cow_page); + return ret; +} + +static vm_fault_t do_shared_fault(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + vm_fault_t ret, tmp; + + ret = __do_fault(vmf); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) + return ret; + + /* + * Check if the backing address space wants to know that the page is + * about to become writable + */ + if (vma->vm_ops->page_mkwrite) { + unlock_page(vmf->page); + tmp = do_page_mkwrite(vmf); + if (unlikely(!tmp || + (tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { + put_page(vmf->page); + return tmp; + } + } + + ret |= finish_fault(vmf); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | + VM_FAULT_RETRY))) { + unlock_page(vmf->page); + put_page(vmf->page); + return ret; + } + + ret |= fault_dirty_shared_page(vmf); + return ret; +} + +/* + * We enter with non-exclusive mmap_lock (to exclude vma changes, + * but allow concurrent faults). + * The mmap_lock may have been released depending on flags and our + * return value. See filemap_fault() and __folio_lock_or_retry(). + * If mmap_lock is released, vma may become invalid (for example + * by other thread calling munmap()). + */ +static vm_fault_t do_fault(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + struct mm_struct *vm_mm = vma->vm_mm; + vm_fault_t ret; + + /* + * The VMA was not fully populated on mmap() or missing VM_DONTEXPAND + */ + if (!vma->vm_ops->fault) { + /* + * If we find a migration pmd entry or a none pmd entry, which + * should never happen, return SIGBUS + */ + if (unlikely(!pmd_present(*vmf->pmd))) + ret = VM_FAULT_SIGBUS; + else { + vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, + vmf->pmd, + vmf->address, + &vmf->ptl); + /* + * Make sure this is not a temporary clearing of pte + * by holding ptl and checking again. A R/M/W update + * of pte involves: take ptl, clearing the pte so that + * we don't have concurrent modification by hardware + * followed by an update. + */ + if (unlikely(pte_none(*vmf->pte))) + ret = VM_FAULT_SIGBUS; + else + ret = VM_FAULT_NOPAGE; + + pte_unmap_unlock(vmf->pte, vmf->ptl); + } + } else if (!(vmf->flags & FAULT_FLAG_WRITE)) + ret = do_read_fault(vmf); + else if (!(vma->vm_flags & VM_SHARED)) + ret = do_cow_fault(vmf); + else + ret = do_shared_fault(vmf); + + /* preallocated pagetable is unused: free it */ + if (vmf->prealloc_pte) { + pte_free(vm_mm, vmf->prealloc_pte); + vmf->prealloc_pte = NULL; + } + return ret; +} + +int numa_migrate_prep(struct page *page, struct vm_area_struct *vma, + unsigned long addr, int page_nid, int *flags) +{ + get_page(page); + + count_vm_numa_event(NUMA_HINT_FAULTS); + if (page_nid == numa_node_id()) { + count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); + *flags |= TNF_FAULT_LOCAL; + } + + return mpol_misplaced(page, vma, addr); +} + +static vm_fault_t do_numa_page(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + struct page *page = NULL; + int page_nid = NUMA_NO_NODE; + int last_cpupid; + int target_nid; + pte_t pte, old_pte; + bool was_writable = pte_savedwrite(vmf->orig_pte); + int flags = 0; + + /* + * The "pte" at this point cannot be used safely without + * validation through pte_unmap_same(). It's of NUMA type but + * the pfn may be screwed if the read is non atomic. + */ + vmf->ptl = pte_lockptr(vma->vm_mm, vmf->pmd); + spin_lock(vmf->ptl); + if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + goto out; + } + + /* Get the normal PTE */ + old_pte = ptep_get(vmf->pte); + pte = pte_modify(old_pte, vma->vm_page_prot); + + page = vm_normal_page(vma, vmf->address, pte); + if (!page || is_zone_device_page(page)) + goto out_map; + + /* TODO: handle PTE-mapped THP */ + if (PageCompound(page)) + goto out_map; + + /* + * Avoid grouping on RO pages in general. RO pages shouldn't hurt as + * much anyway since they can be in shared cache state. This misses + * the case where a mapping is writable but the process never writes + * to it but pte_write gets cleared during protection updates and + * pte_dirty has unpredictable behaviour between PTE scan updates, + * background writeback, dirty balancing and application behaviour. + */ + if (!was_writable) + flags |= TNF_NO_GROUP; + + /* + * Flag if the page is shared between multiple address spaces. This + * is later used when determining whether to group tasks together + */ + if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED)) + flags |= TNF_SHARED; + + page_nid = page_to_nid(page); + /* + * For memory tiering mode, cpupid of slow memory page is used + * to record page access time. So use default value. + */ + if ((sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && + !node_is_toptier(page_nid)) + last_cpupid = (-1 & LAST_CPUPID_MASK); + else + last_cpupid = page_cpupid_last(page); + target_nid = numa_migrate_prep(page, vma, vmf->address, page_nid, + &flags); + if (target_nid == NUMA_NO_NODE) { + put_page(page); + goto out_map; + } + pte_unmap_unlock(vmf->pte, vmf->ptl); + + /* Migrate to the requested node */ + if (migrate_misplaced_page(page, vma, target_nid)) { + page_nid = target_nid; + flags |= TNF_MIGRATED; + } else { + flags |= TNF_MIGRATE_FAIL; + vmf->pte = pte_offset_map(vmf->pmd, vmf->address); + spin_lock(vmf->ptl); + if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + goto out; + } + goto out_map; + } + +out: + if (page_nid != NUMA_NO_NODE) + task_numa_fault(last_cpupid, page_nid, 1, flags); + return 0; +out_map: + /* + * Make it present again, depending on how arch implements + * non-accessible ptes, some can allow access by kernel mode. + */ + old_pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte); + pte = pte_modify(old_pte, vma->vm_page_prot); + pte = pte_mkyoung(pte); + if (was_writable) + pte = pte_mkwrite(pte); + ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte); + update_mmu_cache(vma, vmf->address, vmf->pte); + pte_unmap_unlock(vmf->pte, vmf->ptl); + goto out; +} + +static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf) +{ + if (vma_is_anonymous(vmf->vma)) + return do_huge_pmd_anonymous_page(vmf); + if (vmf->vma->vm_ops->huge_fault) + return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD); + return VM_FAULT_FALLBACK; +} + +/* `inline' is required to avoid gcc 4.1.2 build error */ +static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf) +{ + const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE; + + if (vma_is_anonymous(vmf->vma)) { + if (likely(!unshare) && + userfaultfd_huge_pmd_wp(vmf->vma, vmf->orig_pmd)) + return handle_userfault(vmf, VM_UFFD_WP); + return do_huge_pmd_wp_page(vmf); + } + if (vmf->vma->vm_ops->huge_fault) { + vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD); + + if (!(ret & VM_FAULT_FALLBACK)) + return ret; + } + + /* COW or write-notify handled on pte level: split pmd. */ + __split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL); + + return VM_FAULT_FALLBACK; +} + +static vm_fault_t create_huge_pud(struct vm_fault *vmf) +{ +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \ + defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) + /* No support for anonymous transparent PUD pages yet */ + if (vma_is_anonymous(vmf->vma)) + return VM_FAULT_FALLBACK; + if (vmf->vma->vm_ops->huge_fault) + return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD); +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + return VM_FAULT_FALLBACK; +} + +static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud) +{ +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \ + defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) + /* No support for anonymous transparent PUD pages yet */ + if (vma_is_anonymous(vmf->vma)) + goto split; + if (vmf->vma->vm_ops->huge_fault) { + vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD); + + if (!(ret & VM_FAULT_FALLBACK)) + return ret; + } +split: + /* COW or write-notify not handled on PUD level: split pud.*/ + __split_huge_pud(vmf->vma, vmf->pud, vmf->address); +#endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ + return VM_FAULT_FALLBACK; +} + +/* + * These routines also need to handle stuff like marking pages dirty + * and/or accessed for architectures that don't do it in hardware (most + * RISC architectures). The early dirtying is also good on the i386. + * + * There is also a hook called "update_mmu_cache()" that architectures + * with external mmu caches can use to update those (ie the Sparc or + * PowerPC hashed page tables that act as extended TLBs). + * + * We enter with non-exclusive mmap_lock (to exclude vma changes, but allow + * concurrent faults). + * + * The mmap_lock may have been released depending on flags and our return value. + * See filemap_fault() and __folio_lock_or_retry(). + */ +static vm_fault_t handle_pte_fault(struct vm_fault *vmf) +{ + pte_t entry; + + if (unlikely(pmd_none(*vmf->pmd))) { + /* + * Leave __pte_alloc() until later: because vm_ops->fault may + * want to allocate huge page, and if we expose page table + * for an instant, it will be difficult to retract from + * concurrent faults and from rmap lookups. + */ + vmf->pte = NULL; + vmf->flags &= ~FAULT_FLAG_ORIG_PTE_VALID; + } else { + /* + * If a huge pmd materialized under us just retry later. Use + * pmd_trans_unstable() via pmd_devmap_trans_unstable() instead + * of pmd_trans_huge() to ensure the pmd didn't become + * pmd_trans_huge under us and then back to pmd_none, as a + * result of MADV_DONTNEED running immediately after a huge pmd + * fault in a different thread of this mm, in turn leading to a + * misleading pmd_trans_huge() retval. All we have to ensure is + * that it is a regular pmd that we can walk with + * pte_offset_map() and we can do that through an atomic read + * in C, which is what pmd_trans_unstable() provides. + */ + if (pmd_devmap_trans_unstable(vmf->pmd)) + return 0; + /* + * A regular pmd is established and it can't morph into a huge + * pmd from under us anymore at this point because we hold the + * mmap_lock read mode and khugepaged takes it in write mode. + * So now it's safe to run pte_offset_map(). + */ + vmf->pte = pte_offset_map(vmf->pmd, vmf->address); + vmf->orig_pte = *vmf->pte; + vmf->flags |= FAULT_FLAG_ORIG_PTE_VALID; + + /* + * some architectures can have larger ptes than wordsize, + * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and + * CONFIG_32BIT=y, so READ_ONCE cannot guarantee atomic + * accesses. The code below just needs a consistent view + * for the ifs and we later double check anyway with the + * ptl lock held. So here a barrier will do. + */ + barrier(); + if (pte_none(vmf->orig_pte)) { + pte_unmap(vmf->pte); + vmf->pte = NULL; + } + } + + if (!vmf->pte) { + if (vma_is_anonymous(vmf->vma)) + return do_anonymous_page(vmf); + else + return do_fault(vmf); + } + + if (!pte_present(vmf->orig_pte)) + return do_swap_page(vmf); + + if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma)) + return do_numa_page(vmf); + + vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); + spin_lock(vmf->ptl); + entry = vmf->orig_pte; + if (unlikely(!pte_same(*vmf->pte, entry))) { + update_mmu_tlb(vmf->vma, vmf->address, vmf->pte); + goto unlock; + } + if (vmf->flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) { + if (!pte_write(entry)) + return do_wp_page(vmf); + else if (likely(vmf->flags & FAULT_FLAG_WRITE)) + entry = pte_mkdirty(entry); + } + entry = pte_mkyoung(entry); + if (ptep_set_access_flags(vmf->vma, vmf->address, vmf->pte, entry, + vmf->flags & FAULT_FLAG_WRITE)) { + update_mmu_cache(vmf->vma, vmf->address, vmf->pte); + } else { + /* Skip spurious TLB flush for retried page fault */ + if (vmf->flags & FAULT_FLAG_TRIED) + goto unlock; + /* + * This is needed only for protection faults but the arch code + * is not yet telling us if this is a protection fault or not. + * This still avoids useless tlb flushes for .text page faults + * with threads. + */ + if (vmf->flags & FAULT_FLAG_WRITE) + flush_tlb_fix_spurious_fault(vmf->vma, vmf->address); + } +unlock: + pte_unmap_unlock(vmf->pte, vmf->ptl); + return 0; +} + +/* + * By the time we get here, we already hold the mm semaphore + * + * The mmap_lock may have been released depending on flags and our + * return value. See filemap_fault() and __folio_lock_or_retry(). + */ +static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma, + unsigned long address, unsigned int flags) +{ + struct vm_fault vmf = { + .vma = vma, + .address = address & PAGE_MASK, + .real_address = address, + .flags = flags, + .pgoff = linear_page_index(vma, address), + .gfp_mask = __get_fault_gfp_mask(vma), + }; + struct mm_struct *mm = vma->vm_mm; + unsigned long vm_flags = vma->vm_flags; + pgd_t *pgd; + p4d_t *p4d; + vm_fault_t ret; + + pgd = pgd_offset(mm, address); + p4d = p4d_alloc(mm, pgd, address); + if (!p4d) + return VM_FAULT_OOM; + + vmf.pud = pud_alloc(mm, p4d, address); + if (!vmf.pud) + return VM_FAULT_OOM; +retry_pud: + if (pud_none(*vmf.pud) && + hugepage_vma_check(vma, vm_flags, false, true, true)) { + ret = create_huge_pud(&vmf); + if (!(ret & VM_FAULT_FALLBACK)) + return ret; + } else { + pud_t orig_pud = *vmf.pud; + + barrier(); + if (pud_trans_huge(orig_pud) || pud_devmap(orig_pud)) { + + /* + * TODO once we support anonymous PUDs: NUMA case and + * FAULT_FLAG_UNSHARE handling. + */ + if ((flags & FAULT_FLAG_WRITE) && !pud_write(orig_pud)) { + ret = wp_huge_pud(&vmf, orig_pud); + if (!(ret & VM_FAULT_FALLBACK)) + return ret; + } else { + huge_pud_set_accessed(&vmf, orig_pud); + return 0; + } + } + } + + vmf.pmd = pmd_alloc(mm, vmf.pud, address); + if (!vmf.pmd) + return VM_FAULT_OOM; + + /* Huge pud page fault raced with pmd_alloc? */ + if (pud_trans_unstable(vmf.pud)) + goto retry_pud; + + if (pmd_none(*vmf.pmd) && + hugepage_vma_check(vma, vm_flags, false, true, true)) { + ret = create_huge_pmd(&vmf); + if (!(ret & VM_FAULT_FALLBACK)) + return ret; + } else { + vmf.orig_pmd = *vmf.pmd; + + barrier(); + if (unlikely(is_swap_pmd(vmf.orig_pmd))) { + VM_BUG_ON(thp_migration_supported() && + !is_pmd_migration_entry(vmf.orig_pmd)); + if (is_pmd_migration_entry(vmf.orig_pmd)) + pmd_migration_entry_wait(mm, vmf.pmd); + return 0; + } + if (pmd_trans_huge(vmf.orig_pmd) || pmd_devmap(vmf.orig_pmd)) { + if (pmd_protnone(vmf.orig_pmd) && vma_is_accessible(vma)) + return do_huge_pmd_numa_page(&vmf); + + if ((flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) && + !pmd_write(vmf.orig_pmd)) { + ret = wp_huge_pmd(&vmf); + if (!(ret & VM_FAULT_FALLBACK)) + return ret; + } else { + huge_pmd_set_accessed(&vmf); + return 0; + } + } + } + + return handle_pte_fault(&vmf); +} + +/** + * mm_account_fault - Do page fault accounting + * + * @regs: the pt_regs struct pointer. When set to NULL, will skip accounting + * of perf event counters, but we'll still do the per-task accounting to + * the task who triggered this page fault. + * @address: the faulted address. + * @flags: the fault flags. + * @ret: the fault retcode. + * + * This will take care of most of the page fault accounting. Meanwhile, it + * will also include the PERF_COUNT_SW_PAGE_FAULTS_[MAJ|MIN] perf counter + * updates. However, note that the handling of PERF_COUNT_SW_PAGE_FAULTS should + * still be in per-arch page fault handlers at the entry of page fault. + */ +static inline void mm_account_fault(struct pt_regs *regs, + unsigned long address, unsigned int flags, + vm_fault_t ret) +{ + bool major; + + /* + * We don't do accounting for some specific faults: + * + * - Unsuccessful faults (e.g. when the address wasn't valid). That + * includes arch_vma_access_permitted() failing before reaching here. + * So this is not a "this many hardware page faults" counter. We + * should use the hw profiling for that. + * + * - Incomplete faults (VM_FAULT_RETRY). They will only be counted + * once they're completed. + */ + if (ret & (VM_FAULT_ERROR | VM_FAULT_RETRY)) + return; + + /* + * We define the fault as a major fault when the final successful fault + * is VM_FAULT_MAJOR, or if it retried (which implies that we couldn't + * handle it immediately previously). + */ + major = (ret & VM_FAULT_MAJOR) || (flags & FAULT_FLAG_TRIED); + + if (major) + current->maj_flt++; + else + current->min_flt++; + + /* + * If the fault is done for GUP, regs will be NULL. We only do the + * accounting for the per thread fault counters who triggered the + * fault, and we skip the perf event updates. + */ + if (!regs) + return; + + if (major) + perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); + else + perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); +} + +#ifdef CONFIG_LRU_GEN +static void lru_gen_enter_fault(struct vm_area_struct *vma) +{ + /* the LRU algorithm doesn't apply to sequential or random reads */ + current->in_lru_fault = !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ)); +} + +static void lru_gen_exit_fault(void) +{ + current->in_lru_fault = false; +} +#else +static void lru_gen_enter_fault(struct vm_area_struct *vma) +{ +} + +static void lru_gen_exit_fault(void) +{ +} +#endif /* CONFIG_LRU_GEN */ + +/* + * By the time we get here, we already hold the mm semaphore + * + * The mmap_lock may have been released depending on flags and our + * return value. See filemap_fault() and __folio_lock_or_retry(). + */ +vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, + unsigned int flags, struct pt_regs *regs) +{ + vm_fault_t ret; + + __set_current_state(TASK_RUNNING); + + count_vm_event(PGFAULT); + count_memcg_event_mm(vma->vm_mm, PGFAULT); + + /* do counter updates before entering really critical section. */ + check_sync_rss_stat(current); + + if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE, + flags & FAULT_FLAG_INSTRUCTION, + flags & FAULT_FLAG_REMOTE)) + return VM_FAULT_SIGSEGV; + + /* + * Enable the memcg OOM handling for faults triggered in user + * space. Kernel faults are handled more gracefully. + */ + if (flags & FAULT_FLAG_USER) + mem_cgroup_enter_user_fault(); + + lru_gen_enter_fault(vma); + + if (unlikely(is_vm_hugetlb_page(vma))) + ret = hugetlb_fault(vma->vm_mm, vma, address, flags); + else + ret = __handle_mm_fault(vma, address, flags); + + lru_gen_exit_fault(); + + if (flags & FAULT_FLAG_USER) { + mem_cgroup_exit_user_fault(); + /* + * The task may have entered a memcg OOM situation but + * if the allocation error was handled gracefully (no + * VM_FAULT_OOM), there is no need to kill anything. + * Just clean up the OOM state peacefully. + */ + if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM)) + mem_cgroup_oom_synchronize(false); + } + + mm_account_fault(regs, address, flags, ret); + + return ret; +} +EXPORT_SYMBOL_GPL(handle_mm_fault); + +#ifdef CONFIG_LOCK_MM_AND_FIND_VMA +#include <linux/extable.h> + +static inline bool get_mmap_lock_carefully(struct mm_struct *mm, struct pt_regs *regs) +{ + /* Even if this succeeds, make it clear we *might* have slept */ + if (likely(mmap_read_trylock(mm))) { + might_sleep(); + return true; + } + + if (regs && !user_mode(regs)) { + unsigned long ip = instruction_pointer(regs); + if (!search_exception_tables(ip)) + return false; + } + + return !mmap_read_lock_killable(mm); +} + +static inline bool mmap_upgrade_trylock(struct mm_struct *mm) +{ + /* + * We don't have this operation yet. + * + * It should be easy enough to do: it's basically a + * atomic_long_try_cmpxchg_acquire() + * from RWSEM_READER_BIAS -> RWSEM_WRITER_LOCKED, but + * it also needs the proper lockdep magic etc. + */ + return false; +} + +static inline bool upgrade_mmap_lock_carefully(struct mm_struct *mm, struct pt_regs *regs) +{ + mmap_read_unlock(mm); + if (regs && !user_mode(regs)) { + unsigned long ip = instruction_pointer(regs); + if (!search_exception_tables(ip)) + return false; + } + return !mmap_write_lock_killable(mm); +} + +/* + * Helper for page fault handling. + * + * This is kind of equivalend to "mmap_read_lock()" followed + * by "find_extend_vma()", except it's a lot more careful about + * the locking (and will drop the lock on failure). + * + * For example, if we have a kernel bug that causes a page + * fault, we don't want to just use mmap_read_lock() to get + * the mm lock, because that would deadlock if the bug were + * to happen while we're holding the mm lock for writing. + * + * So this checks the exception tables on kernel faults in + * order to only do this all for instructions that are actually + * expected to fault. + * + * We can also actually take the mm lock for writing if we + * need to extend the vma, which helps the VM layer a lot. + */ +struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm, + unsigned long addr, struct pt_regs *regs) +{ + struct vm_area_struct *vma; + + if (!get_mmap_lock_carefully(mm, regs)) + return NULL; + + vma = find_vma(mm, addr); + if (likely(vma && (vma->vm_start <= addr))) + return vma; + + /* + * Well, dang. We might still be successful, but only + * if we can extend a vma to do so. + */ + if (!vma || !(vma->vm_flags & VM_GROWSDOWN)) { + mmap_read_unlock(mm); + return NULL; + } + + /* + * We can try to upgrade the mmap lock atomically, + * in which case we can continue to use the vma + * we already looked up. + * + * Otherwise we'll have to drop the mmap lock and + * re-take it, and also look up the vma again, + * re-checking it. + */ + if (!mmap_upgrade_trylock(mm)) { + if (!upgrade_mmap_lock_carefully(mm, regs)) + return NULL; + + vma = find_vma(mm, addr); + if (!vma) + goto fail; + if (vma->vm_start <= addr) + goto success; + if (!(vma->vm_flags & VM_GROWSDOWN)) + goto fail; + } + + if (expand_stack_locked(vma, addr)) + goto fail; + +success: + mmap_write_downgrade(mm); + return vma; + +fail: + mmap_write_unlock(mm); + return NULL; +} +#endif + +#ifndef __PAGETABLE_P4D_FOLDED +/* + * Allocate p4d page table. + * We've already handled the fast-path in-line. + */ +int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address) +{ + p4d_t *new = p4d_alloc_one(mm, address); + if (!new) + return -ENOMEM; + + spin_lock(&mm->page_table_lock); + if (pgd_present(*pgd)) { /* Another has populated it */ + p4d_free(mm, new); + } else { + smp_wmb(); /* See comment in pmd_install() */ + pgd_populate(mm, pgd, new); + } + spin_unlock(&mm->page_table_lock); + return 0; +} +#endif /* __PAGETABLE_P4D_FOLDED */ + +#ifndef __PAGETABLE_PUD_FOLDED +/* + * Allocate page upper directory. + * We've already handled the fast-path in-line. + */ +int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, unsigned long address) +{ + pud_t *new = pud_alloc_one(mm, address); + if (!new) + return -ENOMEM; + + spin_lock(&mm->page_table_lock); + if (!p4d_present(*p4d)) { + mm_inc_nr_puds(mm); + smp_wmb(); /* See comment in pmd_install() */ + p4d_populate(mm, p4d, new); + } else /* Another has populated it */ + pud_free(mm, new); + spin_unlock(&mm->page_table_lock); + return 0; +} +#endif /* __PAGETABLE_PUD_FOLDED */ + +#ifndef __PAGETABLE_PMD_FOLDED +/* + * Allocate page middle directory. + * We've already handled the fast-path in-line. + */ +int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address) +{ + spinlock_t *ptl; + pmd_t *new = pmd_alloc_one(mm, address); + if (!new) + return -ENOMEM; + + ptl = pud_lock(mm, pud); + if (!pud_present(*pud)) { + mm_inc_nr_pmds(mm); + smp_wmb(); /* See comment in pmd_install() */ + pud_populate(mm, pud, new); + } else { /* Another has populated it */ + pmd_free(mm, new); + } + spin_unlock(ptl); + return 0; +} +#endif /* __PAGETABLE_PMD_FOLDED */ + +/** + * follow_pte - look up PTE at a user virtual address + * @mm: the mm_struct of the target address space + * @address: user virtual address + * @ptepp: location to store found PTE + * @ptlp: location to store the lock for the PTE + * + * On a successful return, the pointer to the PTE is stored in @ptepp; + * the corresponding lock is taken and its location is stored in @ptlp. + * The contents of the PTE are only stable until @ptlp is released; + * any further use, if any, must be protected against invalidation + * with MMU notifiers. + * + * Only IO mappings and raw PFN mappings are allowed. The mmap semaphore + * should be taken for read. + * + * KVM uses this function. While it is arguably less bad than ``follow_pfn``, + * it is not a good general-purpose API. + * + * Return: zero on success, -ve otherwise. + */ +int follow_pte(struct mm_struct *mm, unsigned long address, + pte_t **ptepp, spinlock_t **ptlp) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + pte_t *ptep; + + pgd = pgd_offset(mm, address); + if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) + goto out; + + p4d = p4d_offset(pgd, address); + if (p4d_none(*p4d) || unlikely(p4d_bad(*p4d))) + goto out; + + pud = pud_offset(p4d, address); + if (pud_none(*pud) || unlikely(pud_bad(*pud))) + goto out; + + pmd = pmd_offset(pud, address); + VM_BUG_ON(pmd_trans_huge(*pmd)); + + if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd))) + goto out; + + ptep = pte_offset_map_lock(mm, pmd, address, ptlp); + if (!pte_present(*ptep)) + goto unlock; + *ptepp = ptep; + return 0; +unlock: + pte_unmap_unlock(ptep, *ptlp); +out: + return -EINVAL; +} +EXPORT_SYMBOL_GPL(follow_pte); + +/** + * follow_pfn - look up PFN at a user virtual address + * @vma: memory mapping + * @address: user virtual address + * @pfn: location to store found PFN + * + * Only IO mappings and raw PFN mappings are allowed. + * + * This function does not allow the caller to read the permissions + * of the PTE. Do not use it. + * + * Return: zero and the pfn at @pfn on success, -ve otherwise. + */ +int follow_pfn(struct vm_area_struct *vma, unsigned long address, + unsigned long *pfn) +{ + int ret = -EINVAL; + spinlock_t *ptl; + pte_t *ptep; + + if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) + return ret; + + ret = follow_pte(vma->vm_mm, address, &ptep, &ptl); + if (ret) + return ret; + *pfn = pte_pfn(*ptep); + pte_unmap_unlock(ptep, ptl); + return 0; +} +EXPORT_SYMBOL(follow_pfn); + +#ifdef CONFIG_HAVE_IOREMAP_PROT +int follow_phys(struct vm_area_struct *vma, + unsigned long address, unsigned int flags, + unsigned long *prot, resource_size_t *phys) +{ + int ret = -EINVAL; + pte_t *ptep, pte; + spinlock_t *ptl; + + if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) + goto out; + + if (follow_pte(vma->vm_mm, address, &ptep, &ptl)) + goto out; + pte = *ptep; + + if ((flags & FOLL_WRITE) && !pte_write(pte)) + goto unlock; + + *prot = pgprot_val(pte_pgprot(pte)); + *phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT; + + ret = 0; +unlock: + pte_unmap_unlock(ptep, ptl); +out: + return ret; +} + +/** + * generic_access_phys - generic implementation for iomem mmap access + * @vma: the vma to access + * @addr: userspace address, not relative offset within @vma + * @buf: buffer to read/write + * @len: length of transfer + * @write: set to FOLL_WRITE when writing, otherwise reading + * + * This is a generic implementation for &vm_operations_struct.access for an + * iomem mapping. This callback is used by access_process_vm() when the @vma is + * not page based. + */ +int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, + void *buf, int len, int write) +{ + resource_size_t phys_addr; + unsigned long prot = 0; + void __iomem *maddr; + pte_t *ptep, pte; + spinlock_t *ptl; + int offset = offset_in_page(addr); + int ret = -EINVAL; + + if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) + return -EINVAL; + +retry: + if (follow_pte(vma->vm_mm, addr, &ptep, &ptl)) + return -EINVAL; + pte = *ptep; + pte_unmap_unlock(ptep, ptl); + + prot = pgprot_val(pte_pgprot(pte)); + phys_addr = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT; + + if ((write & FOLL_WRITE) && !pte_write(pte)) + return -EINVAL; + + maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot); + if (!maddr) + return -ENOMEM; + + if (follow_pte(vma->vm_mm, addr, &ptep, &ptl)) + goto out_unmap; + + if (!pte_same(pte, *ptep)) { + pte_unmap_unlock(ptep, ptl); + iounmap(maddr); + + goto retry; + } + + if (write) + memcpy_toio(maddr + offset, buf, len); + else + memcpy_fromio(buf, maddr + offset, len); + ret = len; + pte_unmap_unlock(ptep, ptl); +out_unmap: + iounmap(maddr); + + return ret; +} +EXPORT_SYMBOL_GPL(generic_access_phys); +#endif + +/* + * Access another process' address space as given in mm. + */ +int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf, + int len, unsigned int gup_flags) +{ + struct vm_area_struct *vma; + void *old_buf = buf; + int write = gup_flags & FOLL_WRITE; + + if (mmap_read_lock_killable(mm)) + return 0; + + /* We might need to expand the stack to access it */ + vma = vma_lookup(mm, addr); + if (!vma) { + vma = expand_stack(mm, addr); + if (!vma) + return 0; + } + + /* ignore errors, just check how much was successfully transferred */ + while (len) { + int bytes, ret, offset; + void *maddr; + struct page *page = NULL; + + ret = get_user_pages_remote(mm, addr, 1, + gup_flags, &page, &vma, NULL); + if (ret <= 0) { +#ifndef CONFIG_HAVE_IOREMAP_PROT + break; +#else + /* + * Check if this is a VM_IO | VM_PFNMAP VMA, which + * we can access using slightly different code. + */ + vma = vma_lookup(mm, addr); + if (!vma) + break; + if (vma->vm_ops && vma->vm_ops->access) + ret = vma->vm_ops->access(vma, addr, buf, + len, write); + if (ret <= 0) + break; + bytes = ret; +#endif + } else { + bytes = len; + offset = addr & (PAGE_SIZE-1); + if (bytes > PAGE_SIZE-offset) + bytes = PAGE_SIZE-offset; + + maddr = kmap(page); + if (write) { + copy_to_user_page(vma, page, addr, + maddr + offset, buf, bytes); + set_page_dirty_lock(page); + } else { + copy_from_user_page(vma, page, addr, + buf, maddr + offset, bytes); + } + kunmap(page); + put_page(page); + } + len -= bytes; + buf += bytes; + addr += bytes; + } + mmap_read_unlock(mm); + + return buf - old_buf; +} + +/** + * access_remote_vm - access another process' address space + * @mm: the mm_struct of the target address space + * @addr: start address to access + * @buf: source or destination buffer + * @len: number of bytes to transfer + * @gup_flags: flags modifying lookup behaviour + * + * The caller must hold a reference on @mm. + * + * Return: number of bytes copied from source to destination. + */ +int access_remote_vm(struct mm_struct *mm, unsigned long addr, + void *buf, int len, unsigned int gup_flags) +{ + return __access_remote_vm(mm, addr, buf, len, gup_flags); +} + +/* + * Access another process' address space. + * Source/target buffer must be kernel space, + * Do not walk the page table directly, use get_user_pages + */ +int access_process_vm(struct task_struct *tsk, unsigned long addr, + void *buf, int len, unsigned int gup_flags) +{ + struct mm_struct *mm; + int ret; + + mm = get_task_mm(tsk); + if (!mm) + return 0; + + ret = __access_remote_vm(mm, addr, buf, len, gup_flags); + + mmput(mm); + + return ret; +} +EXPORT_SYMBOL_GPL(access_process_vm); + +/* + * Print the name of a VMA. + */ +void print_vma_addr(char *prefix, unsigned long ip) +{ + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma; + + /* + * we might be running from an atomic context so we cannot sleep + */ + if (!mmap_read_trylock(mm)) + return; + + vma = find_vma(mm, ip); + if (vma && vma->vm_file) { + struct file *f = vma->vm_file; + char *buf = (char *)__get_free_page(GFP_NOWAIT); + if (buf) { + char *p; + + p = file_path(f, buf, PAGE_SIZE); + if (IS_ERR(p)) + p = "?"; + printk("%s%s[%lx+%lx]", prefix, kbasename(p), + vma->vm_start, + vma->vm_end - vma->vm_start); + free_page((unsigned long)buf); + } + } + mmap_read_unlock(mm); +} + +#if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP) +void __might_fault(const char *file, int line) +{ + if (pagefault_disabled()) + return; + __might_sleep(file, line); +#if defined(CONFIG_DEBUG_ATOMIC_SLEEP) + if (current->mm) + might_lock_read(¤t->mm->mmap_lock); +#endif +} +EXPORT_SYMBOL(__might_fault); +#endif + +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS) +/* + * Process all subpages of the specified huge page with the specified + * operation. The target subpage will be processed last to keep its + * cache lines hot. + */ +static inline void process_huge_page( + unsigned long addr_hint, unsigned int pages_per_huge_page, + void (*process_subpage)(unsigned long addr, int idx, void *arg), + void *arg) +{ + int i, n, base, l; + unsigned long addr = addr_hint & + ~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1); + + /* Process target subpage last to keep its cache lines hot */ + might_sleep(); + n = (addr_hint - addr) / PAGE_SIZE; + if (2 * n <= pages_per_huge_page) { + /* If target subpage in first half of huge page */ + base = 0; + l = n; + /* Process subpages at the end of huge page */ + for (i = pages_per_huge_page - 1; i >= 2 * n; i--) { + cond_resched(); + process_subpage(addr + i * PAGE_SIZE, i, arg); + } + } else { + /* If target subpage in second half of huge page */ + base = pages_per_huge_page - 2 * (pages_per_huge_page - n); + l = pages_per_huge_page - n; + /* Process subpages at the begin of huge page */ + for (i = 0; i < base; i++) { + cond_resched(); + process_subpage(addr + i * PAGE_SIZE, i, arg); + } + } + /* + * Process remaining subpages in left-right-left-right pattern + * towards the target subpage + */ + for (i = 0; i < l; i++) { + int left_idx = base + i; + int right_idx = base + 2 * l - 1 - i; + + cond_resched(); + process_subpage(addr + left_idx * PAGE_SIZE, left_idx, arg); + cond_resched(); + process_subpage(addr + right_idx * PAGE_SIZE, right_idx, arg); + } +} + +static void clear_gigantic_page(struct page *page, + unsigned long addr, + unsigned int pages_per_huge_page) +{ + int i; + struct page *p; + + might_sleep(); + for (i = 0; i < pages_per_huge_page; i++) { + p = nth_page(page, i); + cond_resched(); + clear_user_highpage(p, addr + i * PAGE_SIZE); + } +} + +static void clear_subpage(unsigned long addr, int idx, void *arg) +{ + struct page *page = arg; + + clear_user_highpage(page + idx, addr); +} + +void clear_huge_page(struct page *page, + unsigned long addr_hint, unsigned int pages_per_huge_page) +{ + unsigned long addr = addr_hint & + ~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1); + + if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) { + clear_gigantic_page(page, addr, pages_per_huge_page); + return; + } + + process_huge_page(addr_hint, pages_per_huge_page, clear_subpage, page); +} + +static void copy_user_gigantic_page(struct page *dst, struct page *src, + unsigned long addr, + struct vm_area_struct *vma, + unsigned int pages_per_huge_page) +{ + int i; + struct page *dst_base = dst; + struct page *src_base = src; + + for (i = 0; i < pages_per_huge_page; i++) { + dst = nth_page(dst_base, i); + src = nth_page(src_base, i); + + cond_resched(); + copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma); + } +} + +struct copy_subpage_arg { + struct page *dst; + struct page *src; + struct vm_area_struct *vma; +}; + +static void copy_subpage(unsigned long addr, int idx, void *arg) +{ + struct copy_subpage_arg *copy_arg = arg; + + copy_user_highpage(copy_arg->dst + idx, copy_arg->src + idx, + addr, copy_arg->vma); +} + +void copy_user_huge_page(struct page *dst, struct page *src, + unsigned long addr_hint, struct vm_area_struct *vma, + unsigned int pages_per_huge_page) +{ + unsigned long addr = addr_hint & + ~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1); + struct copy_subpage_arg arg = { + .dst = dst, + .src = src, + .vma = vma, + }; + + if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) { + copy_user_gigantic_page(dst, src, addr, vma, + pages_per_huge_page); + return; + } + + process_huge_page(addr_hint, pages_per_huge_page, copy_subpage, &arg); +} + +long copy_huge_page_from_user(struct page *dst_page, + const void __user *usr_src, + unsigned int pages_per_huge_page, + bool allow_pagefault) +{ + void *page_kaddr; + unsigned long i, rc = 0; + unsigned long ret_val = pages_per_huge_page * PAGE_SIZE; + struct page *subpage; + + for (i = 0; i < pages_per_huge_page; i++) { + subpage = nth_page(dst_page, i); + if (allow_pagefault) + page_kaddr = kmap(subpage); + else + page_kaddr = kmap_atomic(subpage); + rc = copy_from_user(page_kaddr, + usr_src + i * PAGE_SIZE, PAGE_SIZE); + if (allow_pagefault) + kunmap(subpage); + else + kunmap_atomic(page_kaddr); + + ret_val -= (PAGE_SIZE - rc); + if (rc) + break; + + flush_dcache_page(subpage); + + cond_resched(); + } + return ret_val; +} +#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */ + +#if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS + +static struct kmem_cache *page_ptl_cachep; + +void __init ptlock_cache_init(void) +{ + page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0, + SLAB_PANIC, NULL); +} + +bool ptlock_alloc(struct page *page) +{ + spinlock_t *ptl; + + ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL); + if (!ptl) + return false; + page->ptl = ptl; + return true; +} + +void ptlock_free(struct page *page) +{ + kmem_cache_free(page_ptl_cachep, page->ptl); +} +#endif |