Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 436 insertions, 0 deletions

diff --git a/fs/eventfd.c b/fs/eventfd.c
new file mode 100644
index 000000000..ce1d1711f
--- /dev/null
+++ b/fs/eventfd.c
@@ -0,0 +1,436 @@
+/*
+ *  fs/eventfd.c
+ *
+ *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
+ *
+ */
+
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/sched/signal.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/anon_inodes.h>
+#include <linux/syscalls.h>
+#include <linux/export.h>
+#include <linux/kref.h>
+#include <linux/eventfd.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+
+DEFINE_PER_CPU(int, eventfd_wake_count);
+
+struct eventfd_ctx {
+	struct kref kref;
+	wait_queue_head_t wqh;
+	/*
+	 * Every time that a write(2) is performed on an eventfd, the
+	 * value of the __u64 being written is added to "count" and a
+	 * wakeup is performed on "wqh". A read(2) will return the "count"
+	 * value to userspace, and will reset "count" to zero. The kernel
+	 * side eventfd_signal() also, adds to the "count" counter and
+	 * issue a wakeup.
+	 */
+	__u64 count;
+	unsigned int flags;
+};
+
+/**
+ * eventfd_signal - Adds @n to the eventfd counter.
+ * @ctx: [in] Pointer to the eventfd context.
+ * @n: [in] Value of the counter to be added to the eventfd internal counter.
+ *          The value cannot be negative.
+ *
+ * This function is supposed to be called by the kernel in paths that do not
+ * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
+ * value, and we signal this as overflow condition by returning a EPOLLERR
+ * to poll(2).
+ *
+ * Returns the amount by which the counter was incremented.  This will be less
+ * than @n if the counter has overflowed.
+ */
+__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
+{
+	unsigned long flags;
+
+	/*
+	 * Deadlock or stack overflow issues can happen if we recurse here
+	 * through waitqueue wakeup handlers. If the caller users potentially
+	 * nested waitqueues with custom wakeup handlers, then it should
+	 * check eventfd_signal_count() before calling this function. If
+	 * it returns true, the eventfd_signal() call should be deferred to a
+	 * safe context.
+	 */
+	if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count)))
+		return 0;
+
+	spin_lock_irqsave(&ctx->wqh.lock, flags);
+	this_cpu_inc(eventfd_wake_count);
+	if (ULLONG_MAX - ctx->count < n)
+		n = ULLONG_MAX - ctx->count;
+	ctx->count += n;
+	if (waitqueue_active(&ctx->wqh))
+		wake_up_locked_poll(&ctx->wqh, EPOLLIN);
+	this_cpu_dec(eventfd_wake_count);
+	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
+
+	return n;
+}
+EXPORT_SYMBOL_GPL(eventfd_signal);
+
+static void eventfd_free_ctx(struct eventfd_ctx *ctx)
+{
+	kfree(ctx);
+}
+
+static void eventfd_free(struct kref *kref)
+{
+	struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
+
+	eventfd_free_ctx(ctx);
+}
+
+/**
+ * eventfd_ctx_put - Releases a reference to the internal eventfd context.
+ * @ctx: [in] Pointer to eventfd context.
+ *
+ * The eventfd context reference must have been previously acquired either
+ * with eventfd_ctx_fdget() or eventfd_ctx_fileget().
+ */
+void eventfd_ctx_put(struct eventfd_ctx *ctx)
+{
+	kref_put(&ctx->kref, eventfd_free);
+}
+EXPORT_SYMBOL_GPL(eventfd_ctx_put);
+
+static int eventfd_release(struct inode *inode, struct file *file)
+{
+	struct eventfd_ctx *ctx = file->private_data;
+
+	wake_up_poll(&ctx->wqh, EPOLLHUP);
+	eventfd_ctx_put(ctx);
+	return 0;
+}
+
+static __poll_t eventfd_poll(struct file *file, poll_table *wait)
+{
+	struct eventfd_ctx *ctx = file->private_data;
+	__poll_t events = 0;
+	u64 count;
+
+	poll_wait(file, &ctx->wqh, wait);
+
+	/*
+	 * All writes to ctx->count occur within ctx->wqh.lock.  This read
+	 * can be done outside ctx->wqh.lock because we know that poll_wait
+	 * takes that lock (through add_wait_queue) if our caller will sleep.
+	 *
+	 * The read _can_ therefore seep into add_wait_queue's critical
+	 * section, but cannot move above it!  add_wait_queue's spin_lock acts
+	 * as an acquire barrier and ensures that the read be ordered properly
+	 * against the writes.  The following CAN happen and is safe:
+	 *
+	 *     poll                               write
+	 *     -----------------                  ------------
+	 *     lock ctx->wqh.lock (in poll_wait)
+	 *     count = ctx->count
+	 *     __add_wait_queue
+	 *     unlock ctx->wqh.lock
+	 *                                        lock ctx->qwh.lock
+	 *                                        ctx->count += n
+	 *                                        if (waitqueue_active)
+	 *                                          wake_up_locked_poll
+	 *                                        unlock ctx->qwh.lock
+	 *     eventfd_poll returns 0
+	 *
+	 * but the following, which would miss a wakeup, cannot happen:
+	 *
+	 *     poll                               write
+	 *     -----------------                  ------------
+	 *     count = ctx->count (INVALID!)
+	 *                                        lock ctx->qwh.lock
+	 *                                        ctx->count += n
+	 *                                        **waitqueue_active is false**
+	 *                                        **no wake_up_locked_poll!**
+	 *                                        unlock ctx->qwh.lock
+	 *     lock ctx->wqh.lock (in poll_wait)
+	 *     __add_wait_queue
+	 *     unlock ctx->wqh.lock
+	 *     eventfd_poll returns 0
+	 */
+	count = READ_ONCE(ctx->count);
+
+	if (count > 0)
+		events |= EPOLLIN;
+	if (count == ULLONG_MAX)
+		events |= EPOLLERR;
+	if (ULLONG_MAX - 1 > count)
+		events |= EPOLLOUT;
+
+	return events;
+}
+
+static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
+{
+	*cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
+	ctx->count -= *cnt;
+}
+
+/**
+ * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
+ * @ctx: [in] Pointer to eventfd context.
+ * @wait: [in] Wait queue to be removed.
+ * @cnt: [out] Pointer to the 64-bit counter value.
+ *
+ * Returns %0 if successful, or the following error codes:
+ *
+ * -EAGAIN      : The operation would have blocked.
+ *
+ * This is used to atomically remove a wait queue entry from the eventfd wait
+ * queue head, and read/reset the counter value.
+ */
+int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
+				  __u64 *cnt)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ctx->wqh.lock, flags);
+	eventfd_ctx_do_read(ctx, cnt);
+	__remove_wait_queue(&ctx->wqh, wait);
+	if (*cnt != 0 && waitqueue_active(&ctx->wqh))
+		wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
+	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
+
+	return *cnt != 0 ? 0 : -EAGAIN;
+}
+EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
+
+static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
+			    loff_t *ppos)
+{
+	struct eventfd_ctx *ctx = file->private_data;
+	ssize_t res;
+	__u64 ucnt = 0;
+	DECLARE_WAITQUEUE(wait, current);
+
+	if (count < sizeof(ucnt))
+		return -EINVAL;
+
+	spin_lock_irq(&ctx->wqh.lock);
+	res = -EAGAIN;
+	if (ctx->count > 0)
+		res = sizeof(ucnt);
+	else if (!(file->f_flags & O_NONBLOCK)) {
+		__add_wait_queue(&ctx->wqh, &wait);
+		for (;;) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			if (ctx->count > 0) {
+				res = sizeof(ucnt);
+				break;
+			}
+			if (signal_pending(current)) {
+				res = -ERESTARTSYS;
+				break;
+			}
+			spin_unlock_irq(&ctx->wqh.lock);
+			schedule();
+			spin_lock_irq(&ctx->wqh.lock);
+		}
+		__remove_wait_queue(&ctx->wqh, &wait);
+		__set_current_state(TASK_RUNNING);
+	}
+	if (likely(res > 0)) {
+		eventfd_ctx_do_read(ctx, &ucnt);
+		if (waitqueue_active(&ctx->wqh))
+			wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
+	}
+	spin_unlock_irq(&ctx->wqh.lock);
+
+	if (res > 0 && put_user(ucnt, (__u64 __user *)buf))
+		return -EFAULT;
+
+	return res;
+}
+
+static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
+			     loff_t *ppos)
+{
+	struct eventfd_ctx *ctx = file->private_data;
+	ssize_t res;
+	__u64 ucnt;
+	DECLARE_WAITQUEUE(wait, current);
+
+	if (count < sizeof(ucnt))
+		return -EINVAL;
+	if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
+		return -EFAULT;
+	if (ucnt == ULLONG_MAX)
+		return -EINVAL;
+	spin_lock_irq(&ctx->wqh.lock);
+	res = -EAGAIN;
+	if (ULLONG_MAX - ctx->count > ucnt)
+		res = sizeof(ucnt);
+	else if (!(file->f_flags & O_NONBLOCK)) {
+		__add_wait_queue(&ctx->wqh, &wait);
+		for (res = 0;;) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			if (ULLONG_MAX - ctx->count > ucnt) {
+				res = sizeof(ucnt);
+				break;
+			}
+			if (signal_pending(current)) {
+				res = -ERESTARTSYS;
+				break;
+			}
+			spin_unlock_irq(&ctx->wqh.lock);
+			schedule();
+			spin_lock_irq(&ctx->wqh.lock);
+		}
+		__remove_wait_queue(&ctx->wqh, &wait);
+		__set_current_state(TASK_RUNNING);
+	}
+	if (likely(res > 0)) {
+		ctx->count += ucnt;
+		if (waitqueue_active(&ctx->wqh))
+			wake_up_locked_poll(&ctx->wqh, EPOLLIN);
+	}
+	spin_unlock_irq(&ctx->wqh.lock);
+
+	return res;
+}
+
+#ifdef CONFIG_PROC_FS
+static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
+{
+	struct eventfd_ctx *ctx = f->private_data;
+
+	spin_lock_irq(&ctx->wqh.lock);
+	seq_printf(m, "eventfd-count: %16llx\n",
+		   (unsigned long long)ctx->count);
+	spin_unlock_irq(&ctx->wqh.lock);
+}
+#endif
+
+static const struct file_operations eventfd_fops = {
+#ifdef CONFIG_PROC_FS
+	.show_fdinfo	= eventfd_show_fdinfo,
+#endif
+	.release	= eventfd_release,
+	.poll		= eventfd_poll,
+	.read		= eventfd_read,
+	.write		= eventfd_write,
+	.llseek		= noop_llseek,
+};
+
+/**
+ * eventfd_fget - Acquire a reference of an eventfd file descriptor.
+ * @fd: [in] Eventfd file descriptor.
+ *
+ * Returns a pointer to the eventfd file structure in case of success, or the
+ * following error pointer:
+ *
+ * -EBADF    : Invalid @fd file descriptor.
+ * -EINVAL   : The @fd file descriptor is not an eventfd file.
+ */
+struct file *eventfd_fget(int fd)
+{
+	struct file *file;
+
+	file = fget(fd);
+	if (!file)
+		return ERR_PTR(-EBADF);
+	if (file->f_op != &eventfd_fops) {
+		fput(file);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return file;
+}
+EXPORT_SYMBOL_GPL(eventfd_fget);
+
+/**
+ * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
+ * @fd: [in] Eventfd file descriptor.
+ *
+ * Returns a pointer to the internal eventfd context, otherwise the error
+ * pointers returned by the following functions:
+ *
+ * eventfd_fget
+ */
+struct eventfd_ctx *eventfd_ctx_fdget(int fd)
+{
+	struct eventfd_ctx *ctx;
+	struct fd f = fdget(fd);
+	if (!f.file)
+		return ERR_PTR(-EBADF);
+	ctx = eventfd_ctx_fileget(f.file);
+	fdput(f);
+	return ctx;
+}
+EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
+
+/**
+ * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
+ * @file: [in] Eventfd file pointer.
+ *
+ * Returns a pointer to the internal eventfd context, otherwise the error
+ * pointer:
+ *
+ * -EINVAL   : The @fd file descriptor is not an eventfd file.
+ */
+struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
+{
+	struct eventfd_ctx *ctx;
+
+	if (file->f_op != &eventfd_fops)
+		return ERR_PTR(-EINVAL);
+
+	ctx = file->private_data;
+	kref_get(&ctx->kref);
+	return ctx;
+}
+EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
+
+static int do_eventfd(unsigned int count, int flags)
+{
+	struct eventfd_ctx *ctx;
+	int fd;
+
+	/* Check the EFD_* constants for consistency.  */
+	BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
+	BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
+
+	if (flags & ~EFD_FLAGS_SET)
+		return -EINVAL;
+
+	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	kref_init(&ctx->kref);
+	init_waitqueue_head(&ctx->wqh);
+	ctx->count = count;
+	ctx->flags = flags;
+
+	fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
+			      O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
+	if (fd < 0)
+		eventfd_free_ctx(ctx);
+
+	return fd;
+}
+
+SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
+{
+	return do_eventfd(count, flags);
+}
+
+SYSCALL_DEFINE1(eventfd, unsigned int, count)
+{
+	return do_eventfd(count, 0);
+}
+