path: root/kernel/relay.c

/*
 * Public API and common code for kernel->userspace relay file support.
 *
 * See Documentation/filesystems/relay.txt for an overview.
 *
 * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
 * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
 *
 * Moved to kernel/relay.c by Paul Mundt, 2006.
 * November 2006 - CPU hotplug support by Mathieu Desnoyers
 * 	(mathieu.desnoyers@polymtl.ca)
 *
 * This file is released under the GPL.
 */
#include <linux/errno.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/relay.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/splice.h>

/* list of open channels, for cpu hotplug */
static DEFINE_MUTEX(relay_channels_mutex);
static LIST_HEAD(relay_channels);

/*
 * close() vm_op implementation for relay file mapping.
 */
static void relay_file_mmap_close(struct vm_area_struct *vma)
{
	struct rchan_buf *buf = vma->vm_private_data;
	buf->chan->cb->buf_unmapped(buf, vma->vm_file);
}

/*
 * fault() vm_op implementation for relay file mapping.
 */
static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
	struct page *page;
	struct rchan_buf *buf = vma->vm_private_data;
	pgoff_t pgoff = vmf->pgoff;

	if (!buf)
		return VM_FAULT_OOM;

	page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
	if (!page)
		return VM_FAULT_SIGBUS;
	get_page(page);
	vmf->page = page;

	return 0;
}

/*
 * vm_ops for relay file mappings.
 */
static struct vm_operations_struct relay_file_mmap_ops = {
	.fault = relay_buf_fault,
	.close = relay_file_mmap_close,
};

/*
 * allocate an array of pointers of struct page
 */
static struct page **relay_alloc_page_array(unsigned int n_pages)
{
	struct page **array;
	size_t pa_size = n_pages * sizeof(struct page *);

	if (pa_size > PAGE_SIZE) {
		array = vmalloc(pa_size);
		if (array)
			memset(array, 0, pa_size);
	} else {
		array = kzalloc(pa_size, GFP_KERNEL);
	}
	return array;
}

/*
 * free an array of pointers of struct page
 */
static void relay_free_page_array(struct page **array)
{
	if (is_vmalloc_addr(array))
		vfree(array);
	else
		kfree(array);
}

/**
 *	relay_mmap_buf: - mmap channel buffer to process address space
 *	@buf: relay channel buffer
 *	@vma: vm_area_struct describing memory to be mapped
 *
 *	Returns 0 if ok, negative on error
 *
 *	Caller should already have grabbed mmap_sem.
 */
static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
{
	unsigned long length = vma->vm_end - vma->vm_start;
	struct file *filp = vma->vm_file;

	if (!buf)
		return -EBADF;

	if (length != (unsigned long)buf->chan->alloc_size)
		return -EINVAL