diff options
| -rw-r--r-- | fs/userfaultfd.c | 148 | ||||
| -rw-r--r-- | include/linux/userfaultfd_k.h | 13 | ||||
| -rw-r--r-- | include/uapi/linux/userfaultfd.h | 15 | ||||
| -rw-r--r-- | kernel/fork.c | 10 |
4 files changed, 170 insertions, 16 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 87d31921b66c..6046e0b552b2 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -64,6 +64,12 @@ struct userfaultfd_ctx { struct mm_struct *mm; }; +struct userfaultfd_fork_ctx { + struct userfaultfd_ctx *orig; + struct userfaultfd_ctx *new; + struct list_head list; +}; + struct userfaultfd_wait_queue { struct uffd_msg msg; wait_queue_t wq; @@ -465,9 +471,8 @@ out: return ret; } -static int __maybe_unused userfaultfd_event_wait_completion( - struct userfaultfd_ctx *ctx, - struct userfaultfd_wait_queue *ewq) +static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, + struct userfaultfd_wait_queue *ewq) { int ret = 0; @@ -518,6 +523,79 @@ static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, __remove_wait_queue(&ctx->event_wqh, &ewq->wq); } +int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) +{ + struct userfaultfd_ctx *ctx = NULL, *octx; + struct userfaultfd_fork_ctx *fctx; + + octx = vma->vm_userfaultfd_ctx.ctx; + if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { + vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; + vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); + return 0; + } + + list_for_each_entry(fctx, fcs, list) + if (fctx->orig == octx) { + ctx = fctx->new; + break; + } + + if (!ctx) { + fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); + if (!fctx) + return -ENOMEM; + + ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); + if (!ctx) { + kfree(fctx); + return -ENOMEM; + } + + atomic_set(&ctx->refcount, 1); + ctx->flags = octx->flags; + ctx->state = UFFD_STATE_RUNNING; + ctx->features = octx->features; + ctx->released = false; + ctx->mm = vma->vm_mm; + atomic_inc(&ctx->mm->mm_users); + + userfaultfd_ctx_get(octx); + fctx->orig = octx; + fctx->new = ctx; + list_add_tail(&fctx->list, fcs); + } + + vma->vm_userfaultfd_ctx.ctx = ctx; + return 0; +} + +static int dup_fctx(struct userfaultfd_fork_ctx *fctx) +{ + struct userfaultfd_ctx *ctx = fctx->orig; + struct userfaultfd_wait_queue ewq; + + msg_init(&ewq.msg); + + ewq.msg.event = UFFD_EVENT_FORK; + ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; + + return userfaultfd_event_wait_completion(ctx, &ewq); +} + +void dup_userfaultfd_complete(struct list_head *fcs) +{ + int ret = 0; + struct userfaultfd_fork_ctx *fctx, *n; + + list_for_each_entry_safe(fctx, n, fcs, list) { + if (!ret) + ret = dup_fctx(fctx); + list_del(&fctx->list); + kfree(fctx); + } +} + static int userfaultfd_release(struct inode *inode, struct file *file) { struct userfaultfd_ctx *ctx = file->private_data; @@ -653,12 +731,49 @@ static unsigned int userfaultfd_poll(struct file *file, poll_table *wait) } } +static const struct file_operations userfaultfd_fops; + +static int resolve_userfault_fork(struct userfaultfd_ctx *ctx, + struct userfaultfd_ctx *new, + struct uffd_msg *msg) +{ + int fd; + struct file *file; + unsigned int flags = new->flags & UFFD_SHARED_FCNTL_FLAGS; + + fd = get_unused_fd_flags(flags); + if (fd < 0) + return fd; + + file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, new, + O_RDWR | flags); + if (IS_ERR(file)) { + put_unused_fd(fd); + return PTR_ERR(file); + } + + fd_install(fd, file); + msg->arg.reserved.reserved1 = 0; + msg->arg.fork.ufd = fd; + + return 0; +} + static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, struct uffd_msg *msg) { ssize_t ret; DECLARE_WAITQUEUE(wait, current); struct userfaultfd_wait_queue *uwq; + /* + * Handling fork event requires sleeping operations, so + * we drop the event_wqh lock, then do these ops, then + * lock it back and wake up the waiter. While the lock is + * dropped the ewq may go away so we keep track of it + * carefully. + */ + LIST_HEAD(fork_event); + struct userfaultfd_ctx *fork_nctx = NULL; /* always take the fd_wqh lock before the fault_pending_wqh lock */ spin_lock(&ctx->fd_wqh.lock); @@ -716,6 +831,16 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, if (uwq) { *msg = uwq->msg; + if (uwq->msg.event == UFFD_EVENT_FORK) { + fork_nctx = (struct userfaultfd_ctx *) + (unsigned long) + uwq->msg.arg.reserved.reserved1; + list_move(&uwq->wq.task_list, &fork_event); + spin_unlock(&ctx->event_wqh.lock); + ret = 0; + break; + } + userfaultfd_event_complete(ctx, uwq); spin_unlock(&ctx->event_wqh.lock); ret = 0; @@ -739,6 +864,23 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, __set_current_state(TASK_RUNNING); spin_unlock(&ctx->fd_wqh.lock); + if (!ret && msg->event == UFFD_EVENT_FORK) { + ret = resolve_userfault_fork(ctx, fork_nctx, msg); + + if (!ret) { + spin_lock(&ctx->event_wqh.lock); + if (!list_empty(&fork_event)) { + uwq = list_first_entry(&fork_event, + typeof(*uwq), + wq.task_list); + list_del(&uwq->wq.task_list); + __add_wait_queue(&ctx->event_wqh, &uwq->wq); + userfaultfd_event_complete(ctx, uwq); + } + spin_unlock(&ctx->event_wqh.lock); + } + } + return ret; } diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 11b92b047a1e..79002bca1f43 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -52,6 +52,9 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma) return vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP); } +extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *); +extern void dup_userfaultfd_complete(struct list_head *); + #else /* CONFIG_USERFAULTFD */ /* mm helpers */ @@ -76,6 +79,16 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma) return false; } +static inline int dup_userfaultfd(struct vm_area_struct *vma, + struct list_head *l) +{ + return 0; +} + +static inline void dup_userfaultfd_complete(struct list_head *l) +{ +} + #endif /* CONFIG_USERFAULTFD */ #endif /* _LINUX_USERFAULTFD_K_H */ diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 94046b8aa6ad..c8953c84fdcc 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -18,12 +18,7 @@ * means the userland is reading). */ #define UFFD_API ((__u64)0xAA) -/* - * After implementing the respective features it will become: - * #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP | \ - * UFFD_FEATURE_EVENT_FORK) - */ -#define UFFD_API_FEATURES (0) +#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -78,6 +73,10 @@ struct uffd_msg { } pagefault; struct { + __u32 ufd; + } fork; + + struct { /* unused reserved fields */ __u64 reserved1; __u64 reserved2; @@ -90,9 +89,7 @@ struct uffd_msg { * Start at 0x12 and not at 0 to be more strict against bugs. */ #define UFFD_EVENT_PAGEFAULT 0x12 -#if 0 /* not available yet */ #define UFFD_EVENT_FORK 0x13 -#endif /* flags for UFFD_EVENT_PAGEFAULT */ #define UFFD_PAGEFAULT_FLAG_WRITE (1<<0) /* If this was a write fault */ @@ -111,10 +108,8 @@ struct uffdio_api { * are to be considered implicitly always enabled in all kernels as * long as the uffdio_api.api requested matches UFFD_API. */ -#if 0 /* not available yet */ #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) -#endif __u64 features; __u64 ioctls; diff --git a/kernel/fork.c b/kernel/fork.c index ff82e24573b6..d12fcc4db8a3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -55,6 +55,7 @@ #include <linux/rmap.h> #include <linux/ksm.h> #include <linux/acct.h> +#include <linux/userfaultfd_k.h> #include <linux/tsacct_kern.h> #include <linux/cn_proc.h> #include <linux/freezer.h> @@ -561,6 +562,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, struct rb_node **rb_link, *rb_parent; int retval; unsigned long charge; + LIST_HEAD(uf); uprobe_start_dup_mmap(); if (down_write_killable(&oldmm->mmap_sem)) { @@ -617,12 +619,13 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, if (retval) goto fail_nomem_policy; tmp->vm_mm = mm; + retval = dup_userfaultfd(tmp, &uf); + if (retval) + goto fail_nomem_anon_vma_fork; if (anon_vma_fork(tmp, mpnt)) goto fail_nomem_anon_vma_fork; - tmp->vm_flags &= - ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP); + tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); tmp->vm_next = tmp->vm_prev = NULL; - tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; file = tmp->vm_file; if (file) { struct inode *inode = file_inode(file); @@ -678,6 +681,7 @@ out: up_write(&mm->mmap_sem); flush_tlb_mm(oldmm); up_write(&oldmm->mmap_sem); + dup_userfaultfd_complete(&uf); fail_uprobe_end: uprobe_end_dup_mmap(); return retval; |