drivers/char/mem.c



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/*
 *  linux/drivers/char/mem.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Added devfs support.
 *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
 *  Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
 */

#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/mman.h>
#include <linux/random.h>
#include <linux/init.h>
#include <linux/raw.h>
#include <linux/tty.h>
#include <linux/capability.h>
#include <linux/ptrace.h>
#include <linux/device.h>
#include <linux/highmem.h>
#include <linux/crash_dump.h>
#include <linux/backing-dev.h>
#include <linux/bootmem.h>
#include <linux/splice.h>
#include <linux/pfn.h>

#include <asm/uaccess.h>
#include <asm/io.h>

#ifdef CONFIG_IA64
# include <linux/efi.h>
#endif

static inline unsigned long size_inside_page(unsigned long start,
					     unsigned long size)
{
	unsigned long sz;

	sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));

	return min(sz, size);
}

#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
static inline int valid_phys_addr_range(unsigned long addr, size_t count)
{
	return addr + count <= __pa(high_memory);
}

static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
{
	return 1;
}
#endif

#ifdef CONFIG_STRICT_DEVMEM
static inline int range_is_allowed(unsigned long pfn, unsigned long size)
{
	u64 from = ((u64)pfn) << PAGE_SHIFT;
	u64 to = from + size;
	u64 cursor = from;

	while (cursor < to) {
		if (!devmem_is_allowed(pfn)) {
			printk(KERN_INFO
		"Program %s tried to access /dev/mem between %Lx->%Lx.\n",
				current->comm, from, to);
			return 0;
		}
		cursor += PAGE_SIZE;
		pfn++;
	}
	return 1;
}
#else
static inline int range_is_allowed(unsigned long pfn, unsigned long size)
{
	return 1;
}
#endif

void __weak unxlate_dev_mem_ptr(unsigned long phys, void *addr)
{
}

/*
 * This funcion reads the *physical* memory. The f_pos points directly to the
 * memory location.
 */
static ssize_t read_mem(struct file *file, char __user *buf,
			size_t count, loff_t *ppos)
{
	unsigned long p = *ppos;
	ssize_t read, sz;
	char *ptr;

	if (!valid_phys_addr_range(p, count))
		return -EFAULT;
	read = 0;
#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
	/* we don't have page 0 mapped on sparc and m68k.. */
	if (p < PAGE_SIZE) {
		sz = size_inside_page(p, count);
		if (sz > 0) {
			if (clear_user(buf, sz))
				return -EFAULT;
			buf += sz;
			p += sz;
			count -= sz;
			read += sz;
		}
	}
#endif

	while (count > 0) {
		unsigned long remaining;

		sz = size_inside_page(p, count);

		if (!range_is_allowed(p >> PAGE_SHIFT, count))
			return -EPERM;

		/*
		 * On ia64 if a page has been mapped somewhere as uncached, then
		 * it must also be accessed uncached by the kernel or data
		 * corruption may occur.
		 */
		ptr = xlate_dev_mem_ptr(p);
		if (!ptr)
			return -EFAULT;

		remaining = copy_to_user(buf, ptr, sz);
		unxlate_dev_mem_ptr(p, ptr);
		if (remaining)
			return -EFAULT;

		buf += sz;
		p += sz;
		count -= sz;
		read += sz;
	}

	*ppos += read;
	return read;
}

static ssize_t write_mem(struct file *file, const char __user *buf,
			 size_t count, loff_t *ppos)
{
	unsigned long p = *ppos;
	ssize_t written, sz;
	unsigned long copied;
	void *ptr;

	if (!valid_phys_addr_range(p, count))
		return -EFAULT;

	written = 0;

#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
	/* we don't have page 0 mapped on sparc and m68k.. */
	if (p < PAGE_SIZE) {
		sz = size_inside_page(p, count);
		/* Hmm. Do something? */
		buf += sz;
		p += sz;
		count -= sz;
		written += sz;
	}
#endif

	while (count > 0) {
		sz = size_inside_page(p, count);

		if (!range_is_allowed(p >> PAGE_SHIFT, sz))
			return -EPERM;

		/*
		 * On ia64 if a page has been mapped somewhere as uncached, then
		 * it must also be accessed uncached by the kernel or data
		 * corruption may occur.
		 */
		ptr = xlate_dev_mem_ptr(p);
		if (!ptr) {
			if (written)
				break;
			return -EFAULT;
		}

		copied = copy_from_user(ptr, buf, sz);
		unxlate_dev_mem_ptr(p, ptr);
		if (copied) {
			written += sz - copied;
			if (written)
				break;
			return -EFAULT;
		}

		buf += sz;
		p += sz;
		count -= sz;
		written += sz;
	}

	*ppos += written;
	return written;
}

int __weak phys_mem_access_prot_allowed(struct file *file,
	unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
{
	return 1;
}

#ifndef __HAVE_PHYS_MEM_ACCESS_PROT

/*
 * Architectures vary in how they handle caching for addresses
 * outside of main memory.
 *
 */
#ifdef pgprot_noncached
static int uncached_access(struct file *file, unsigned long addr)
{
#if defined(CONFIG_IA64)
	/*
	 * On ia64, we ignore O_DSYNC because we cannot tolerate memory
	 * attribute aliases.
	 */
	return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
#elif defined(CONFIG_MIPS)
	{
		extern int __uncached_access(struct file *file,
					     unsigned long addr);

		return __uncached_access(file, addr);
	}
#else
	/*
	 * Accessing memory above the top the kernel knows about or through a
	 * file pointer
	 * that was marked O_DSYNC will be done non-cached.
	 */
	if (file->f_flags & O_DSYNC)
		return 1;
	return addr >= __pa(high_memory);
#endif
}
#endif

static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
				     unsigned long size, pgprot_t vma_prot)
{
#ifdef pgprot_noncached
	unsigned long offset = pfn << PAGE_SHIFT;

	if (uncached_access(file, offset))
		return pgprot_noncached(vma_prot);
#endif
	return vma_prot;
}
#endif

#ifndef CONFIG_MMU
static unsigned long get_unmapped_area_mem(struct file *file,
					   unsigned long addr,
					   unsigned long len,
					   unsigned long pgoff,
					   unsigned long flags)
{
	if (!valid_mmap_phys_addr_range(pgoff, len))
		return (unsigned long) -EINVAL;
	return pgoff << PAGE_SHIFT;
}

/* can't do an in-place private mapping if there's no MMU */
static inline int private_mapping_ok(struct vm_area_struct *vma)
{
	return vma->vm_flags & VM_MAYSHARE;
}
#else
#define get_unmapped_area_mem	NULL

static inline int private_mapping_ok(struct vm_area_struct *vma)
{
	return 1;
}
#endif

static const struct vm_operations_struct mmap_mem_ops = {
#ifdef CONFIG_HAVE_IOREMAP_PROT
	.access = generic_access_phys
#endif
};

static int mmap_mem(struct file *file, struct vm_area_struct *vma)
{
	size_t size = vma->vm_end - vma->vm_start;

	if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
		return -EINVAL;

	if (!private_mapping_ok(vma))
		return -ENOSYS;

	if (!range_is_allowed(vma->vm_pgoff, size))
		return -EPERM;

	if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
						&vma->vm_page_prot))
		return -EINVAL;

	vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
						 size,
						 vma->vm_page_prot);

	vma->vm_ops = &mmap_mem_ops;

	/* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
	if (remap_pfn_range(vma,
			    vma->vm_start,
			    vma->vm_pgoff,
			    size,
			    vma->vm_page_prot)) {
		return -EAGAIN;
	}
	return 0;
}

#ifdef CONFIG_DEVKMEM
static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
{
	unsigned long pfn;

	/* Turn a kernel-virtual address into a physical page frame */
	pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;

	/*
	 * RED-PEN: on some architectures there is more mapped memory than
	 * available in mem_map which pfn_valid checks for. Perhaps should add a
	 * new macro here.
	 *
	 * RED-PEN: vmalloc is not supported right now.
	 */
	if (!pfn_valid(pfn))
		return -EIO;

	vma->vm_pgoff = pfn;
	return mmap_mem(file, vma);
}
#endif

#ifdef CONFIG_CRASH_DUMP
/*
 * Read memory corresponding to the old kernel.
 */
static ssize_t read_oldmem(struct file *file, char __user *buf,
				size_t count, loff_t *ppos)
{
	unsigned long pfn, offset;
	size_t read = 0, csize;
	int rc = 0;

	while (count) {
		pfn = *ppos / PAGE_SIZE;
		if (pfn > saved_max_pfn)
			return read;

		offset = (unsigned long)(*ppos % PAGE_SIZE);
		if (count > PAGE_SIZE - offset)
			csize = PAGE_SIZE - offset;
		else
			csize = count;

		rc = copy_oldmem_page(pfn, buf, csize, offset, 1);
		if (rc < 0)
			return rc;
		buf += csize;
		*ppos += csize;
		read += csize;
		count -= csize;
	}
	return read;
}
#endif

#ifdef CONFIG_DEVKMEM
/*
 * This function reads the *virtual* memory as seen by the kernel.
 */
static ssize_t read_kmem(struct file *file, char __user *buf,
			 size_t count, loff_t *ppos)
{
	unsigned long p = *ppos;
	ssize_t low_count, read, sz;
	char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
	int err = 0;

	read = 0;
	if (p < (unsigned long) high_memory) {
		low_count = count;
		if (count > (unsigned long)high_memory - p)
			low_count = (unsigned long)high_memory - p;

#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
		/* we don't have page 0 mapped on sparc and m68k.. */
		if (p < PAGE_SIZE && low_count > 0) {
			sz = size_inside_page(p, low_count);
			if (clear_user(buf, sz))
				return -EFAULT;
			buf += sz;
			p += sz;
			read += sz;
			low_count -= sz;
			count -= sz;
		}
#endif
		while (low_count > 0) {
			sz = size_inside_page(p, low_count);

			/*
			 * On ia64 if a page has been mapped somewhere as
			 * uncached, then it must also be accessed uncached
			 * by the kernel or data corruption may occur
			 */
			kbuf = xlate_dev_kmem_ptr((char *)p);

			if (copy_to_user(buf, kbuf, sz))
				return -EFAULT;
			buf += sz;
			p += sz;
			read += sz;
			low_count -= sz;
			count -= sz;
		}
	}

	if (count > 0) {
		kbuf = (char *)__get_free_page(GFP_KERNEL);
		if (!kbuf)
			return -ENOMEM;
		while (count > 0) {
			sz = size_inside_page(p, count);
			if (!is_vmalloc_or_module_addr((void *)p)) {
				err = -ENXIO;
				break;
			}
			sz = vread(kbuf, (char *)p, sz);
			if (!sz)
				break;
			if (copy_to_user(buf, kbuf, sz)) {
				err = -EFAULT;
				break;