From 897ab3e0c49e24b62e2d54d165c7afec6bbca65b Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Fri, 24 Feb 2017 14:58:22 -0800 Subject: userfaultfd: non-cooperative: add event for memory unmaps When a non-cooperative userfaultfd monitor copies pages in the background, it may encounter regions that were already unmapped. Addition of UFFD_EVENT_UNMAP allows the uffd monitor to track precisely changes in the virtual memory layout. Since there might be different uffd contexts for the affected VMAs, we first should create a temporary representation for the unmap event for each uffd context and then notify them one by one to the appropriate userfault file descriptors. The event notification occurs after the mmap_sem has been released. [arnd@arndb.de: fix nommu build] Link: http://lkml.kernel.org/r/20170203165141.3665284-1-arnd@arndb.de [mhocko@suse.com: fix nommu build] Link: http://lkml.kernel.org/r/20170202091503.GA22823@dhcp22.suse.cz Link: http://lkml.kernel.org/r/1485542673-24387-3-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport Signed-off-by: Michal Hocko Signed-off-by: Arnd Bergmann Acked-by: Hillf Danton Cc: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Mike Kravetz Cc: Pavel Emelyanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mmap.c | 46 +++++++++++++++++++++++++++++++--------------- 1 file changed, 31 insertions(+), 15 deletions(-) (limited to 'mm/mmap.c') diff --git a/mm/mmap.c b/mm/mmap.c index 13d16a2b7623..1cec28d20583 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -176,7 +176,7 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) return next; } -static int do_brk(unsigned long addr, unsigned long len); +static int do_brk(unsigned long addr, unsigned long len, struct list_head *uf); SYSCALL_DEFINE1(brk, unsigned long, brk) { @@ -185,6 +185,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) struct mm_struct *mm = current->mm; unsigned long min_brk; bool populate; + LIST_HEAD(uf); if (down_write_killable(&mm->mmap_sem)) return -EINTR; @@ -222,7 +223,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) /* Always allow shrinking brk. */ if (brk <= mm->brk) { - if (!do_munmap(mm, newbrk, oldbrk-newbrk)) + if (!do_munmap(mm, newbrk, oldbrk-newbrk, &uf)) goto set_brk; goto out; } @@ -232,13 +233,14 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) goto out; /* Ok, looks good - let it rip. */ - if (do_brk(oldbrk, newbrk-oldbrk) < 0) + if (do_brk(oldbrk, newbrk-oldbrk, &uf) < 0) goto out; set_brk: mm->brk = brk; populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0; up_write(&mm->mmap_sem); + userfaultfd_unmap_complete(mm, &uf); if (populate) mm_populate(oldbrk, newbrk - oldbrk); return brk; @@ -1304,7 +1306,8 @@ static inline int mlock_future_check(struct mm_struct *mm, unsigned long do_mmap(struct file *file, unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags, vm_flags_t vm_flags, - unsigned long pgoff, unsigned long *populate) + unsigned long pgoff, unsigned long *populate, + struct list_head *uf) { struct mm_struct *mm = current->mm; int pkey = 0; @@ -1447,7 +1450,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr, vm_flags |= VM_NORESERVE; } - addr = mmap_region(file, addr, len, vm_flags, pgoff); + addr = mmap_region(file, addr, len, vm_flags, pgoff, uf); if (!IS_ERR_VALUE(addr) && ((vm_flags & VM_LOCKED) || (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE)) @@ -1583,7 +1586,8 @@ static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags) } unsigned long mmap_region(struct file *file, unsigned long addr, - unsigned long len, vm_flags_t vm_flags, unsigned long pgoff) + unsigned long len, vm_flags_t vm_flags, unsigned long pgoff, + struct list_head *uf) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma, *prev; @@ -1609,7 +1613,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, /* Clear old maps */ while (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent)) { - if (do_munmap(mm, addr, len)) + if (do_munmap(mm, addr, len, uf)) return -ENOMEM; } @@ -2579,7 +2583,8 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma, * work. This now handles partial unmappings. * Jeremy Fitzhardinge */ -int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) +int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, + struct list_head *uf) { unsigned long end; struct vm_area_struct *vma, *prev, *last; @@ -2603,6 +2608,13 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) if (vma->vm_start >= end) return 0; + if (uf) { + int error = userfaultfd_unmap_prep(vma, start, end, uf); + + if (error) + return error; + } + /* * If we need to split any vma, do it now to save pain later. * @@ -2668,12 +2680,14 @@ int vm_munmap(unsigned long start, size_t len) { int ret; struct mm_struct *mm = current->mm; + LIST_HEAD(uf); if (down_write_killable(&mm->mmap_sem)) return -EINTR; - ret = do_munmap(mm, start, len); + ret = do_munmap(mm, start, len, &uf); up_write(&mm->mmap_sem); + userfaultfd_unmap_complete(mm, &uf); return ret; } EXPORT_SYMBOL(vm_munmap); @@ -2773,7 +2787,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, file = get_file(vma->vm_file); ret = do_mmap_pgoff(vma->vm_file, start, size, - prot, flags, pgoff, &populate); + prot, flags, pgoff, &populate, NULL); fput(file); out: up_write(&mm->mmap_sem); @@ -2799,7 +2813,7 @@ static inline void verify_mm_writelocked(struct mm_struct *mm) * anonymous maps. eventually we may be able to do some * brk-specific accounting here. */ -static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags) +static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags, struct list_head *uf) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma, *prev; @@ -2838,7 +2852,7 @@ static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long */ while (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent)) { - if (do_munmap(mm, addr, len)) + if (do_munmap(mm, addr, len, uf)) return -ENOMEM; } @@ -2885,9 +2899,9 @@ out: return 0; } -static int do_brk(unsigned long addr, unsigned long len) +static int do_brk(unsigned long addr, unsigned long len, struct list_head *uf) { - return do_brk_flags(addr, len, 0); + return do_brk_flags(addr, len, 0, uf); } int vm_brk_flags(unsigned long addr, unsigned long len, unsigned long flags) @@ -2895,13 +2909,15 @@ int vm_brk_flags(unsigned long addr, unsigned long len, unsigned long flags) struct mm_struct *mm = current->mm; int ret; bool populate; + LIST_HEAD(uf); if (down_write_killable(&mm->mmap_sem)) return -EINTR; - ret = do_brk_flags(addr, len, flags); + ret = do_brk_flags(addr, len, flags, &uf); populate = ((mm->def_flags & VM_LOCKED) != 0); up_write(&mm->mmap_sem); + userfaultfd_unmap_complete(mm, &uf); if (populate && !ret) mm_populate(addr, len); return ret; -- cgit v1.2.3