path: root/drivers/char/mem.c

/*
 *  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 mmaping 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/smp_lock.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/pipe_fs_i.h>
#include <linux/pfn.h>

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

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

/*
 * Architectures vary in how they handle caching for addresses
 * outside of main memory.
 *
 */
static inline int uncached_access(struct file *file, unsigned long addr)
{
#if defined(__i386__)
	/*
	 * On the PPro and successors, the MTRRs are used to set
	 * memory types for physical addresses outside main memory,
	 * so blindly setting PCD or PWT on those pages is wrong.
	 * For Pentiums and earlier, the surround logic should disable
	 * caching for the high addresses through the KEN pin, but
	 * we maintain the tradition of paranoia in this code.
	 */
	if (file->f_flags & O_SYNC)
		return 1;
 	return !( test_bit(X86_FEATURE_MTRR, boot_cpu_data.x86_capability) ||
		  test_bit(X86_FEATURE_K6_MTRR, boot_cpu_data.x86_capability) ||
		  test_bit(X86_FEATURE_CYRIX_ARR, boot_cpu_data.x86_capability) ||
		  test_bit(X86_FEATURE_CENTAUR_MCR, boot_cpu_data.x86_capability) )
	  && addr >= __pa(high_memory);
#elif defined(__x86_64__)
	/* 
	 * This is broken because it can generate memory type aliases,
	 * which can cause cache corruptions
	 * But it is only available for root and we have to be bug-to-bug
	 * compatible with i386.
	 */
	if (file->f_flags & O_SYNC)
		return 1;
	/* same behaviour as i386. PAT always set to cached and MTRRs control the
	   caching behaviour. 
	   Hopefully a full PAT implementation will fix that soon. */	   
	return 0;
#elif defined(CONFIG_IA64)
	/*
	 * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases.
	 */
	return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
#else
	/*
	 * Accessing memory above the top the kernel knows about or through a file pointer
	 * that was marked O_SYNC will be done non-cached.
	 */
	if (file->f_flags & O_SYNC)
		return 1;
	return addr >= __pa(high_memory);
#endif
}

#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
static inline int valid_phys_addr_range(unsigned long addr, size_t count)
{
	if (addr + count > __pa(high_memory))
		return 0;

	return 1;
}

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

/*
 * 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 = PAGE_SIZE - p;
		if (sz > count) 
			sz = count; 
		if (sz > 0) {
			if (clear_user(buf, sz))
				return -EFAULT;
			buf += sz; 
			p += sz; 
			count -= sz; 
			read += sz; 
		}
	}
#endif

	while (count > 0) {
		/*
		 * Handle first page in case it's not aligned
		 */
		if (-p & (PAGE_SIZE - 1))
			sz = -p & (PAGE_SIZE - 1);
		else
			sz = PAGE_SIZE;

		sz = min_t(unsigned long, sz, 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
		 */
		ptr = xlate_dev_mem_ptr(p);

		if (copy_to_user(buf, ptr, sz))
			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;</