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  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *  linux/drivers/char/mem.c
  4 *
  5 *  Copyright (C) 1991, 1992  Linus Torvalds
  6 *
  7 *  Added devfs support.
  8 *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
  9 *  Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
 10 */
 11
 12#include <linux/mm.h>
 13#include <linux/miscdevice.h>
 14#include <linux/slab.h>
 15#include <linux/vmalloc.h>
 16#include <linux/mman.h>
 17#include <linux/random.h>
 18#include <linux/init.h>
 
 19#include <linux/tty.h>
 20#include <linux/capability.h>
 21#include <linux/ptrace.h>
 22#include <linux/device.h>
 23#include <linux/highmem.h>
 24#include <linux/backing-dev.h>
 25#include <linux/shmem_fs.h>
 26#include <linux/splice.h>
 27#include <linux/pfn.h>
 28#include <linux/export.h>
 29#include <linux/io.h>
 30#include <linux/uio.h>
 
 31#include <linux/uaccess.h>
 32#include <linux/security.h>
 33
 34#ifdef CONFIG_IA64
 35# include <linux/efi.h>
 36#endif
 37
 38#define DEVMEM_MINOR	1
 39#define DEVPORT_MINOR	4
 40
 41static inline unsigned long size_inside_page(unsigned long start,
 42					     unsigned long size)
 43{
 44	unsigned long sz;
 45
 46	sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
 47
 48	return min(sz, size);
 49}
 50
 51#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
 52static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
 53{
 54	return addr + count <= __pa(high_memory);
 55}
 56
 57static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
 58{
 59	return 1;
 60}
 61#endif
 62
 63#ifdef CONFIG_STRICT_DEVMEM
 64static inline int page_is_allowed(unsigned long pfn)
 65{
 66	return devmem_is_allowed(pfn);
 67}
 68static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 69{
 70	u64 from = ((u64)pfn) << PAGE_SHIFT;
 71	u64 to = from + size;
 72	u64 cursor = from;
 73
 74	while (cursor < to) {
 75		if (!devmem_is_allowed(pfn))
 
 
 
 76			return 0;
 
 77		cursor += PAGE_SIZE;
 78		pfn++;
 79	}
 80	return 1;
 81}
 82#else
 83static inline int page_is_allowed(unsigned long pfn)
 84{
 85	return 1;
 86}
 87static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 88{
 89	return 1;
 90}
 91#endif
 92
 93#ifndef unxlate_dev_mem_ptr
 94#define unxlate_dev_mem_ptr unxlate_dev_mem_ptr
 95void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
 96{
 97}
 98#endif
 99
100static inline bool should_stop_iteration(void)
101{
102	if (need_resched())
103		cond_resched();
104	return signal_pending(current);
105}
106
107/*
108 * This funcion reads the *physical* memory. The f_pos points directly to the
109 * memory location.
110 */
111static ssize_t read_mem(struct file *file, char __user *buf,
112			size_t count, loff_t *ppos)
113{
114	phys_addr_t p = *ppos;
115	ssize_t read, sz;
116	void *ptr;
117	char *bounce;
118	int err;
119
120	if (p != *ppos)
121		return 0;
122
123	if (!valid_phys_addr_range(p, count))
124		return -EFAULT;
125	read = 0;
126#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
127	/* we don't have page 0 mapped on sparc and m68k.. */
128	if (p < PAGE_SIZE) {
129		sz = size_inside_page(p, count);
130		if (sz > 0) {
131			if (clear_user(buf, sz))
132				return -EFAULT;
133			buf += sz;
134			p += sz;
135			count -= sz;
136			read += sz;
137		}
138	}
139#endif
140
141	bounce = kmalloc(PAGE_SIZE, GFP_KERNEL);
142	if (!bounce)
143		return -ENOMEM;
144
145	while (count > 0) {
146		unsigned long remaining;
147		int allowed, probe;
148
149		sz = size_inside_page(p, count);
150
151		err = -EPERM;
152		allowed = page_is_allowed(p >> PAGE_SHIFT);
153		if (!allowed)
154			goto failed;
155
156		err = -EFAULT;
157		if (allowed == 2) {
158			/* Show zeros for restricted memory. */
159			remaining = clear_user(buf, sz);
160		} else {
161			/*
162			 * On ia64 if a page has been mapped somewhere as
163			 * uncached, then it must also be accessed uncached
164			 * by the kernel or data corruption may occur.
165			 */
166			ptr = xlate_dev_mem_ptr(p);
167			if (!ptr)
168				goto failed;
169
170			probe = copy_from_kernel_nofault(bounce, ptr, sz);
171			unxlate_dev_mem_ptr(p, ptr);
172			if (probe)
173				goto failed;
174
175			remaining = copy_to_user(buf, bounce, sz);
176		}
 
 
 
 
 
 
177
 
 
178		if (remaining)
179			goto failed;
180
181		buf += sz;
182		p += sz;
183		count -= sz;
184		read += sz;
185		if (should_stop_iteration())
186			break;
187	}
188	kfree(bounce);
189
190	*ppos += read;
191	return read;
192
193failed:
194	kfree(bounce);
195	return err;
196}
197
198static ssize_t write_mem(struct file *file, const char __user *buf,
199			 size_t count, loff_t *ppos)
200{
201	phys_addr_t p = *ppos;
202	ssize_t written, sz;
203	unsigned long copied;
204	void *ptr;
205
206	if (p != *ppos)
207		return -EFBIG;
208
209	if (!valid_phys_addr_range(p, count))
210		return -EFAULT;
211
212	written = 0;
213
214#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
215	/* we don't have page 0 mapped on sparc and m68k.. */
216	if (p < PAGE_SIZE) {
217		sz = size_inside_page(p, count);
218		/* Hmm. Do something? */
219		buf += sz;
220		p += sz;
221		count -= sz;
222		written += sz;
223	}
224#endif
225
226	while (count > 0) {
227		int allowed;
228
229		sz = size_inside_page(p, count);
230
231		allowed = page_is_allowed(p >> PAGE_SHIFT);
232		if (!allowed)
233			return -EPERM;
234
235		/* Skip actual writing when a page is marked as restricted. */
236		if (allowed == 1) {
237			/*
238			 * On ia64 if a page has been mapped somewhere as
239			 * uncached, then it must also be accessed uncached
240			 * by the kernel or data corruption may occur.
241			 */
242			ptr = xlate_dev_mem_ptr(p);
243			if (!ptr) {
244				if (written)
245					break;
246				return -EFAULT;
247			}
248
249			copied = copy_from_user(ptr, buf, sz);
250			unxlate_dev_mem_ptr(p, ptr);
251			if (copied) {
252				written += sz - copied;
253				if (written)
254					break;
255				return -EFAULT;
256			}
257		}
258
259		buf += sz;
260		p += sz;
261		count -= sz;
262		written += sz;
263		if (should_stop_iteration())
264			break;
265	}
266
267	*ppos += written;
268	return written;
269}
270
271int __weak phys_mem_access_prot_allowed(struct file *file,
272	unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
273{
274	return 1;
275}
276
277#ifndef __HAVE_PHYS_MEM_ACCESS_PROT
278
279/*
280 * Architectures vary in how they handle caching for addresses
281 * outside of main memory.
282 *
283 */
284#ifdef pgprot_noncached
285static int uncached_access(struct file *file, phys_addr_t addr)
286{
287#if defined(CONFIG_IA64)
288	/*
289	 * On ia64, we ignore O_DSYNC because we cannot tolerate memory
290	 * attribute aliases.
291	 */
292	return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
 
 
 
 
 
 
 
293#else
294	/*
295	 * Accessing memory above the top the kernel knows about or through a
296	 * file pointer
297	 * that was marked O_DSYNC will be done non-cached.
298	 */
299	if (file->f_flags & O_DSYNC)
300		return 1;
301	return addr >= __pa(high_memory);
302#endif
303}
304#endif
305
306static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
307				     unsigned long size, pgprot_t vma_prot)
308{
309#ifdef pgprot_noncached
310	phys_addr_t offset = pfn << PAGE_SHIFT;
311
312	if (uncached_access(file, offset))
313		return pgprot_noncached(vma_prot);
314#endif
315	return vma_prot;
316}
317#endif
318
319#ifndef CONFIG_MMU
320static unsigned long get_unmapped_area_mem(struct file *file,
321					   unsigned long addr,
322					   unsigned long len,
323					   unsigned long pgoff,
324					   unsigned long flags)
325{
326	if (!valid_mmap_phys_addr_range(pgoff, len))
327		return (unsigned long) -EINVAL;
328	return pgoff << PAGE_SHIFT;
329}
330
331/* permit direct mmap, for read, write or exec */
332static unsigned memory_mmap_capabilities(struct file *file)
333{
334	return NOMMU_MAP_DIRECT |
335		NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
336}
337
338static unsigned zero_mmap_capabilities(struct file *file)
339{
340	return NOMMU_MAP_COPY;
341}
342
343/* can't do an in-place private mapping if there's no MMU */
344static inline int private_mapping_ok(struct vm_area_struct *vma)
345{
346	return vma->vm_flags & VM_MAYSHARE;
347}
348#else
349
350static inline int private_mapping_ok(struct vm_area_struct *vma)
351{
352	return 1;
353}
354#endif
355
356static const struct vm_operations_struct mmap_mem_ops = {
357#ifdef CONFIG_HAVE_IOREMAP_PROT
358	.access = generic_access_phys
359#endif
360};
361
362static int mmap_mem(struct file *file, struct vm_area_struct *vma)
363{
364	size_t size = vma->vm_end - vma->vm_start;
365	phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
366
367	/* Does it even fit in phys_addr_t? */
368	if (offset >> PAGE_SHIFT != vma->vm_pgoff)
369		return -EINVAL;
370
371	/* It's illegal to wrap around the end of the physical address space. */
372	if (offset + (phys_addr_t)size - 1 < offset)
373		return -EINVAL;
374
375	if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
376		return -EINVAL;
377
378	if (!private_mapping_ok(vma))
379		return -ENOSYS;
380
381	if (!range_is_allowed(vma->vm_pgoff, size))
382		return -EPERM;
383
384	if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
385						&vma->vm_page_prot))
386		return -EINVAL;
387
388	vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
389						 size,
390						 vma->vm_page_prot);
391
392	vma->vm_ops = &mmap_mem_ops;
393
394	/* Remap-pfn-range will mark the range VM_IO */
395	if (remap_pfn_range(vma,
396			    vma->vm_start,
397			    vma->vm_pgoff,
398			    size,
399			    vma->vm_page_prot)) {
400		return -EAGAIN;
401	}
402	return 0;
403}
404
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
405static ssize_t read_port(struct file *file, char __user *buf,
406			 size_t count, loff_t *ppos)
407{
408	unsigned long i = *ppos;
409	char __user *tmp = buf;
410
411	if (!access_ok(buf, count))
412		return -EFAULT;
413	while (count-- > 0 && i < 65536) {
414		if (__put_user(inb(i), tmp) < 0)
415			return -EFAULT;
416		i++;
417		tmp++;
418	}
419	*ppos = i;
420	return tmp-buf;
421}
422
423static ssize_t write_port(struct file *file, const char __user *buf,
424			  size_t count, loff_t *ppos)
425{
426	unsigned long i = *ppos;
427	const char __user *tmp = buf;
428
429	if (!access_ok(buf, count))
430		return -EFAULT;
431	while (count-- > 0 && i < 65536) {
432		char c;
433
434		if (__get_user(c, tmp)) {
435			if (tmp > buf)
436				break;
437			return -EFAULT;
438		}
439		outb(c, i);
440		i++;
441		tmp++;
442	}
443	*ppos = i;
444	return tmp-buf;
445}
446
447static ssize_t read_null(struct file *file, char __user *buf,
448			 size_t count, loff_t *ppos)
449{
450	return 0;
451}
452
453static ssize_t write_null(struct file *file, const char __user *buf,
454			  size_t count, loff_t *ppos)
455{
456	return count;
457}
458
459static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)
460{
461	return 0;
462}
463
464static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
465{
466	size_t count = iov_iter_count(from);
467	iov_iter_advance(from, count);
468	return count;
469}
470
471static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
472			struct splice_desc *sd)
473{
474	return sd->len;
475}
476
477static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
478				 loff_t *ppos, size_t len, unsigned int flags)
479{
480	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
481}
482
483static int uring_cmd_null(struct io_uring_cmd *ioucmd, unsigned int issue_flags)
484{
485	return 0;
486}
487
488static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
489{
490	size_t written = 0;
491
492	while (iov_iter_count(iter)) {
493		size_t chunk = iov_iter_count(iter), n;
494
495		if (chunk > PAGE_SIZE)
496			chunk = PAGE_SIZE;	/* Just for latency reasons */
497		n = iov_iter_zero(chunk, iter);
498		if (!n && iov_iter_count(iter))
499			return written ? written : -EFAULT;
500		written += n;
501		if (signal_pending(current))
502			return written ? written : -ERESTARTSYS;
503		if (!need_resched())
504			continue;
505		if (iocb->ki_flags & IOCB_NOWAIT)
506			return written ? written : -EAGAIN;
507		cond_resched();
508	}
509	return written;
510}
511
512static ssize_t read_zero(struct file *file, char __user *buf,
513			 size_t count, loff_t *ppos)
514{
515	size_t cleared = 0;
516
517	while (count) {
518		size_t chunk = min_t(size_t, count, PAGE_SIZE);
519		size_t left;
520
521		left = clear_user(buf + cleared, chunk);
522		if (unlikely(left)) {
523			cleared += (chunk - left);
524			if (!cleared)
525				return -EFAULT;
526			break;
527		}
528		cleared += chunk;
529		count -= chunk;
530
531		if (signal_pending(current))
532			break;
533		cond_resched();
534	}
535
536	return cleared;
537}
538
539static int mmap_zero(struct file *file, struct vm_area_struct *vma)
540{
541#ifndef CONFIG_MMU
542	return -ENOSYS;
543#endif
544	if (vma->vm_flags & VM_SHARED)
545		return shmem_zero_setup(vma);
546	vma_set_anonymous(vma);
547	return 0;
548}
549
550static unsigned long get_unmapped_area_zero(struct file *file,
551				unsigned long addr, unsigned long len,
552				unsigned long pgoff, unsigned long flags)
553{
554#ifdef CONFIG_MMU
555	if (flags & MAP_SHARED) {
556		/*
557		 * mmap_zero() will call shmem_zero_setup() to create a file,
558		 * so use shmem's get_unmapped_area in case it can be huge;
559		 * and pass NULL for file as in mmap.c's get_unmapped_area(),
560		 * so as not to confuse shmem with our handle on "/dev/zero".
561		 */
562		return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags);
563	}
564
565	/* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */
566	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
567#else
568	return -ENOSYS;
569#endif
570}
571
572static ssize_t write_full(struct file *file, const char __user *buf,
573			  size_t count, loff_t *ppos)
574{
575	return -ENOSPC;
576}
577
578/*
579 * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
580 * can fopen() both devices with "a" now.  This was previously impossible.
581 * -- SRB.
582 */
583static loff_t null_lseek(struct file *file, loff_t offset, int orig)
584{
585	return file->f_pos = 0;
586}
587
588/*
589 * The memory devices use the full 32/64 bits of the offset, and so we cannot
590 * check against negative addresses: they are ok. The return value is weird,
591 * though, in that case (0).
592 *
593 * also note that seeking relative to the "end of file" isn't supported:
594 * it has no meaning, so it returns -EINVAL.
595 */
596static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
597{
598	loff_t ret;
599
600	inode_lock(file_inode(file));
601	switch (orig) {
602	case SEEK_CUR:
603		offset += file->f_pos;
604		fallthrough;
605	case SEEK_SET:
606		/* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
607		if ((unsigned long long)offset >= -MAX_ERRNO) {
608			ret = -EOVERFLOW;
609			break;
610		}
611		file->f_pos = offset;
612		ret = file->f_pos;
613		force_successful_syscall_return();
614		break;
615	default:
616		ret = -EINVAL;
617	}
618	inode_unlock(file_inode(file));
619	return ret;
620}
621
622static int open_port(struct inode *inode, struct file *filp)
623{
624	int rc;
625
626	if (!capable(CAP_SYS_RAWIO))
627		return -EPERM;
628
629	rc = security_locked_down(LOCKDOWN_DEV_MEM);
630	if (rc)
631		return rc;
632
633	if (iminor(inode) != DEVMEM_MINOR)
634		return 0;
635
636	/*
637	 * Use a unified address space to have a single point to manage
638	 * revocations when drivers want to take over a /dev/mem mapped
639	 * range.
640	 */
641	filp->f_mapping = iomem_get_mapping();
642
643	return 0;
644}
645
646#define zero_lseek	null_lseek
647#define full_lseek      null_lseek
648#define write_zero	write_null
649#define write_iter_zero	write_iter_null
650#define open_mem	open_port
 
651
652static const struct file_operations __maybe_unused mem_fops = {
653	.llseek		= memory_lseek,
654	.read		= read_mem,
655	.write		= write_mem,
656	.mmap		= mmap_mem,
657	.open		= open_mem,
658#ifndef CONFIG_MMU
659	.get_unmapped_area = get_unmapped_area_mem,
660	.mmap_capabilities = memory_mmap_capabilities,
661#endif
662};
663
 
 
 
 
 
 
 
 
 
 
 
 
664static const struct file_operations null_fops = {
665	.llseek		= null_lseek,
666	.read		= read_null,
667	.write		= write_null,
668	.read_iter	= read_iter_null,
669	.write_iter	= write_iter_null,
670	.splice_write	= splice_write_null,
671	.uring_cmd	= uring_cmd_null,
672};
673
674static const struct file_operations __maybe_unused port_fops = {
675	.llseek		= memory_lseek,
676	.read		= read_port,
677	.write		= write_port,
678	.open		= open_port,
679};
680
681static const struct file_operations zero_fops = {
682	.llseek		= zero_lseek,
683	.write		= write_zero,
684	.read_iter	= read_iter_zero,
685	.read		= read_zero,
686	.write_iter	= write_iter_zero,
687	.mmap		= mmap_zero,
688	.get_unmapped_area = get_unmapped_area_zero,
689#ifndef CONFIG_MMU
690	.mmap_capabilities = zero_mmap_capabilities,
691#endif
692};
693
694static const struct file_operations full_fops = {
695	.llseek		= full_lseek,
696	.read_iter	= read_iter_zero,
697	.write		= write_full,
698};
699
700static const struct memdev {
701	const char *name;
702	umode_t mode;
703	const struct file_operations *fops;
704	fmode_t fmode;
705} devlist[] = {
706#ifdef CONFIG_DEVMEM
707	 [DEVMEM_MINOR] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },
 
 
 
708#endif
709	 [3] = { "null", 0666, &null_fops, FMODE_NOWAIT },
710#ifdef CONFIG_DEVPORT
711	 [4] = { "port", 0, &port_fops, 0 },
712#endif
713	 [5] = { "zero", 0666, &zero_fops, FMODE_NOWAIT },
714	 [7] = { "full", 0666, &full_fops, 0 },
715	 [8] = { "random", 0666, &random_fops, FMODE_NOWAIT },
716	 [9] = { "urandom", 0666, &urandom_fops, FMODE_NOWAIT },
717#ifdef CONFIG_PRINTK
718	[11] = { "kmsg", 0644, &kmsg_fops, 0 },
719#endif
720};
721
722static int memory_open(struct inode *inode, struct file *filp)
723{
724	int minor;
725	const struct memdev *dev;
726
727	minor = iminor(inode);
728	if (minor >= ARRAY_SIZE(devlist))
729		return -ENXIO;
730
731	dev = &devlist[minor];
732	if (!dev->fops)
733		return -ENXIO;
734
735	filp->f_op = dev->fops;
736	filp->f_mode |= dev->fmode;
737
738	if (dev->fops->open)
739		return dev->fops->open(inode, filp);
740
741	return 0;
742}
743
744static const struct file_operations memory_fops = {
745	.open = memory_open,
746	.llseek = noop_llseek,
747};
748
749static char *mem_devnode(const struct device *dev, umode_t *mode)
750{
751	if (mode && devlist[MINOR(dev->devt)].mode)
752		*mode = devlist[MINOR(dev->devt)].mode;
753	return NULL;
754}
755
756static struct class *mem_class;
757
758static int __init chr_dev_init(void)
759{
760	int minor;
761
762	if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
763		printk("unable to get major %d for memory devs\n", MEM_MAJOR);
764
765	mem_class = class_create(THIS_MODULE, "mem");
766	if (IS_ERR(mem_class))
767		return PTR_ERR(mem_class);
768
769	mem_class->devnode = mem_devnode;
770	for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
771		if (!devlist[minor].name)
772			continue;
773
774		/*
775		 * Create /dev/port?
776		 */
777		if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
778			continue;
779
780		device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
781			      NULL, devlist[minor].name);
782	}
783
784	return tty_init();
785}
786
787fs_initcall(chr_dev_init);
v4.6
 
  1/*
  2 *  linux/drivers/char/mem.c
  3 *
  4 *  Copyright (C) 1991, 1992  Linus Torvalds
  5 *
  6 *  Added devfs support.
  7 *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
  8 *  Shared /dev/zero mmapping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
  9 */
 10
 11#include <linux/mm.h>
 12#include <linux/miscdevice.h>
 13#include <linux/slab.h>
 14#include <linux/vmalloc.h>
 15#include <linux/mman.h>
 16#include <linux/random.h>
 17#include <linux/init.h>
 18#include <linux/raw.h>
 19#include <linux/tty.h>
 20#include <linux/capability.h>
 21#include <linux/ptrace.h>
 22#include <linux/device.h>
 23#include <linux/highmem.h>
 24#include <linux/backing-dev.h>
 
 25#include <linux/splice.h>
 26#include <linux/pfn.h>
 27#include <linux/export.h>
 28#include <linux/io.h>
 29#include <linux/uio.h>
 30
 31#include <linux/uaccess.h>
 
 32
 33#ifdef CONFIG_IA64
 34# include <linux/efi.h>
 35#endif
 36
 
 37#define DEVPORT_MINOR	4
 38
 39static inline unsigned long size_inside_page(unsigned long start,
 40					     unsigned long size)
 41{
 42	unsigned long sz;
 43
 44	sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
 45
 46	return min(sz, size);
 47}
 48
 49#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
 50static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
 51{
 52	return addr + count <= __pa(high_memory);
 53}
 54
 55static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
 56{
 57	return 1;
 58}
 59#endif
 60
 61#ifdef CONFIG_STRICT_DEVMEM
 
 
 
 
 62static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 63{
 64	u64 from = ((u64)pfn) << PAGE_SHIFT;
 65	u64 to = from + size;
 66	u64 cursor = from;
 67
 68	while (cursor < to) {
 69		if (!devmem_is_allowed(pfn)) {
 70			printk(KERN_INFO
 71		"Program %s tried to access /dev/mem between %Lx->%Lx.\n",
 72				current->comm, from, to);
 73			return 0;
 74		}
 75		cursor += PAGE_SIZE;
 76		pfn++;
 77	}
 78	return 1;
 79}
 80#else
 
 
 
 
 81static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 82{
 83	return 1;
 84}
 85#endif
 86
 87#ifndef unxlate_dev_mem_ptr
 88#define unxlate_dev_mem_ptr unxlate_dev_mem_ptr
 89void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
 90{
 91}
 92#endif
 93
 
 
 
 
 
 
 
 94/*
 95 * This funcion reads the *physical* memory. The f_pos points directly to the
 96 * memory location.
 97 */
 98static ssize_t read_mem(struct file *file, char __user *buf,
 99			size_t count, loff_t *ppos)
100{
101	phys_addr_t p = *ppos;
102	ssize_t read, sz;
103	void *ptr;
 
 
104
105	if (p != *ppos)
106		return 0;
107
108	if (!valid_phys_addr_range(p, count))
109		return -EFAULT;
110	read = 0;
111#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
112	/* we don't have page 0 mapped on sparc and m68k.. */
113	if (p < PAGE_SIZE) {
114		sz = size_inside_page(p, count);
115		if (sz > 0) {
116			if (clear_user(buf, sz))
117				return -EFAULT;
118			buf += sz;
119			p += sz;
120			count -= sz;
121			read += sz;
122		}
123	}
124#endif
125
 
 
 
 
126	while (count > 0) {
127		unsigned long remaining;
 
128
129		sz = size_inside_page(p, count);
130
131		if (!range_is_allowed(p >> PAGE_SHIFT, count))
132			return -EPERM;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
133
134		/*
135		 * On ia64 if a page has been mapped somewhere as uncached, then
136		 * it must also be accessed uncached by the kernel or data
137		 * corruption may occur.
138		 */
139		ptr = xlate_dev_mem_ptr(p);
140		if (!ptr)
141			return -EFAULT;
142
143		remaining = copy_to_user(buf, ptr, sz);
144		unxlate_dev_mem_ptr(p, ptr);
145		if (remaining)
146			return -EFAULT;
147
148		buf += sz;
149		p += sz;
150		count -= sz;
151		read += sz;
 
 
152	}
 
153
154	*ppos += read;
155	return read;
 
 
 
 
156}
157
158static ssize_t write_mem(struct file *file, const char __user *buf,
159			 size_t count, loff_t *ppos)
160{
161	phys_addr_t p = *ppos;
162	ssize_t written, sz;
163	unsigned long copied;
164	void *ptr;
165
166	if (p != *ppos)
167		return -EFBIG;
168
169	if (!valid_phys_addr_range(p, count))
170		return -EFAULT;
171
172	written = 0;
173
174#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
175	/* we don't have page 0 mapped on sparc and m68k.. */
176	if (p < PAGE_SIZE) {
177		sz = size_inside_page(p, count);
178		/* Hmm. Do something? */
179		buf += sz;
180		p += sz;
181		count -= sz;
182		written += sz;
183	}
184#endif
185
186	while (count > 0) {
 
 
187		sz = size_inside_page(p, count);
188
189		if (!range_is_allowed(p >> PAGE_SHIFT, sz))
 
190			return -EPERM;
191
192		/*
193		 * On ia64 if a page has been mapped somewhere as uncached, then
194		 * it must also be accessed uncached by the kernel or data
195		 * corruption may occur.
196		 */
197		ptr = xlate_dev_mem_ptr(p);
198		if (!ptr) {
199			if (written)
200				break;
201			return -EFAULT;
202		}
 
 
203
204		copied = copy_from_user(ptr, buf, sz);
205		unxlate_dev_mem_ptr(p, ptr);
206		if (copied) {
207			written += sz - copied;
208			if (written)
209				break;
210			return -EFAULT;
 
211		}
212
213		buf += sz;
214		p += sz;
215		count -= sz;
216		written += sz;
 
 
217	}
218
219	*ppos += written;
220	return written;
221}
222
223int __weak phys_mem_access_prot_allowed(struct file *file,
224	unsigned long pfn, unsigned long size, pgprot_t *vma_prot)
225{
226	return 1;
227}
228
229#ifndef __HAVE_PHYS_MEM_ACCESS_PROT
230
231/*
232 * Architectures vary in how they handle caching for addresses
233 * outside of main memory.
234 *
235 */
236#ifdef pgprot_noncached
237static int uncached_access(struct file *file, phys_addr_t addr)
238{
239#if defined(CONFIG_IA64)
240	/*
241	 * On ia64, we ignore O_DSYNC because we cannot tolerate memory
242	 * attribute aliases.
243	 */
244	return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
245#elif defined(CONFIG_MIPS)
246	{
247		extern int __uncached_access(struct file *file,
248					     unsigned long addr);
249
250		return __uncached_access(file, addr);
251	}
252#else
253	/*
254	 * Accessing memory above the top the kernel knows about or through a
255	 * file pointer
256	 * that was marked O_DSYNC will be done non-cached.
257	 */
258	if (file->f_flags & O_DSYNC)
259		return 1;
260	return addr >= __pa(high_memory);
261#endif
262}
263#endif
264
265static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
266				     unsigned long size, pgprot_t vma_prot)
267{
268#ifdef pgprot_noncached
269	phys_addr_t offset = pfn << PAGE_SHIFT;
270
271	if (uncached_access(file, offset))
272		return pgprot_noncached(vma_prot);
273#endif
274	return vma_prot;
275}
276#endif
277
278#ifndef CONFIG_MMU
279static unsigned long get_unmapped_area_mem(struct file *file,
280					   unsigned long addr,
281					   unsigned long len,
282					   unsigned long pgoff,
283					   unsigned long flags)
284{
285	if (!valid_mmap_phys_addr_range(pgoff, len))
286		return (unsigned long) -EINVAL;
287	return pgoff << PAGE_SHIFT;
288}
289
290/* permit direct mmap, for read, write or exec */
291static unsigned memory_mmap_capabilities(struct file *file)
292{
293	return NOMMU_MAP_DIRECT |
294		NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
295}
296
297static unsigned zero_mmap_capabilities(struct file *file)
298{
299	return NOMMU_MAP_COPY;
300}
301
302/* can't do an in-place private mapping if there's no MMU */
303static inline int private_mapping_ok(struct vm_area_struct *vma)
304{
305	return vma->vm_flags & VM_MAYSHARE;
306}
307#else
308
309static inline int private_mapping_ok(struct vm_area_struct *vma)
310{
311	return 1;
312}
313#endif
314
315static const struct vm_operations_struct mmap_mem_ops = {
316#ifdef CONFIG_HAVE_IOREMAP_PROT
317	.access = generic_access_phys
318#endif
319};
320
321static int mmap_mem(struct file *file, struct vm_area_struct *vma)
322{
323	size_t size = vma->vm_end - vma->vm_start;
 
 
 
 
 
 
 
 
 
324
325	if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
326		return -EINVAL;
327
328	if (!private_mapping_ok(vma))
329		return -ENOSYS;
330
331	if (!range_is_allowed(vma->vm_pgoff, size))
332		return -EPERM;
333
334	if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
335						&vma->vm_page_prot))
336		return -EINVAL;
337
338	vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
339						 size,
340						 vma->vm_page_prot);
341
342	vma->vm_ops = &mmap_mem_ops;
343
344	/* Remap-pfn-range will mark the range VM_IO */
345	if (remap_pfn_range(vma,
346			    vma->vm_start,
347			    vma->vm_pgoff,
348			    size,
349			    vma->vm_page_prot)) {
350		return -EAGAIN;
351	}
352	return 0;
353}
354
355static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
356{
357	unsigned long pfn;
358
359	/* Turn a kernel-virtual address into a physical page frame */
360	pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
361
362	/*
363	 * RED-PEN: on some architectures there is more mapped memory than
364	 * available in mem_map which pfn_valid checks for. Perhaps should add a
365	 * new macro here.
366	 *
367	 * RED-PEN: vmalloc is not supported right now.
368	 */
369	if (!pfn_valid(pfn))
370		return -EIO;
371
372	vma->vm_pgoff = pfn;
373	return mmap_mem(file, vma);
374}
375
376/*
377 * This function reads the *virtual* memory as seen by the kernel.
378 */
379static ssize_t read_kmem(struct file *file, char __user *buf,
380			 size_t count, loff_t *ppos)
381{
382	unsigned long p = *ppos;
383	ssize_t low_count, read, sz;
384	char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
385	int err = 0;
386
387	read = 0;
388	if (p < (unsigned long) high_memory) {
389		low_count = count;
390		if (count > (unsigned long)high_memory - p)
391			low_count = (unsigned long)high_memory - p;
392
393#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
394		/* we don't have page 0 mapped on sparc and m68k.. */
395		if (p < PAGE_SIZE && low_count > 0) {
396			sz = size_inside_page(p, low_count);
397			if (clear_user(buf, sz))
398				return -EFAULT;
399			buf += sz;
400			p += sz;
401			read += sz;
402			low_count -= sz;
403			count -= sz;
404		}
405#endif
406		while (low_count > 0) {
407			sz = size_inside_page(p, low_count);
408
409			/*
410			 * On ia64 if a page has been mapped somewhere as
411			 * uncached, then it must also be accessed uncached
412			 * by the kernel or data corruption may occur
413			 */
414			kbuf = xlate_dev_kmem_ptr((void *)p);
415
416			if (copy_to_user(buf, kbuf, sz))
417				return -EFAULT;
418			buf += sz;
419			p += sz;
420			read += sz;
421			low_count -= sz;
422			count -= sz;
423		}
424	}
425
426	if (count > 0) {
427		kbuf = (char *)__get_free_page(GFP_KERNEL);
428		if (!kbuf)
429			return -ENOMEM;
430		while (count > 0) {
431			sz = size_inside_page(p, count);
432			if (!is_vmalloc_or_module_addr((void *)p)) {
433				err = -ENXIO;
434				break;
435			}
436			sz = vread(kbuf, (char *)p, sz);
437			if (!sz)
438				break;
439			if (copy_to_user(buf, kbuf, sz)) {
440				err = -EFAULT;
441				break;
442			}
443			count -= sz;
444			buf += sz;
445			read += sz;
446			p += sz;
447		}
448		free_page((unsigned long)kbuf);
449	}
450	*ppos = p;
451	return read ? read : err;
452}
453
454
455static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
456				size_t count, loff_t *ppos)
457{
458	ssize_t written, sz;
459	unsigned long copied;
460
461	written = 0;
462#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
463	/* we don't have page 0 mapped on sparc and m68k.. */
464	if (p < PAGE_SIZE) {
465		sz = size_inside_page(p, count);
466		/* Hmm. Do something? */
467		buf += sz;
468		p += sz;
469		count -= sz;
470		written += sz;
471	}
472#endif
473
474	while (count > 0) {
475		void *ptr;
476
477		sz = size_inside_page(p, count);
478
479		/*
480		 * On ia64 if a page has been mapped somewhere as uncached, then
481		 * it must also be accessed uncached by the kernel or data
482		 * corruption may occur.
483		 */
484		ptr = xlate_dev_kmem_ptr((void *)p);
485
486		copied = copy_from_user(ptr, buf, sz);
487		if (copied) {
488			written += sz - copied;
489			if (written)
490				break;
491			return -EFAULT;
492		}
493		buf += sz;
494		p += sz;
495		count -= sz;
496		written += sz;
497	}
498
499	*ppos += written;
500	return written;
501}
502
503/*
504 * This function writes to the *virtual* memory as seen by the kernel.
505 */
506static ssize_t write_kmem(struct file *file, const char __user *buf,
507			  size_t count, loff_t *ppos)
508{
509	unsigned long p = *ppos;
510	ssize_t wrote = 0;
511	ssize_t virtr = 0;
512	char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
513	int err = 0;
514
515	if (p < (unsigned long) high_memory) {
516		unsigned long to_write = min_t(unsigned long, count,
517					       (unsigned long)high_memory - p);
518		wrote = do_write_kmem(p, buf, to_write, ppos);
519		if (wrote != to_write)
520			return wrote;
521		p += wrote;
522		buf += wrote;
523		count -= wrote;
524	}
525
526	if (count > 0) {
527		kbuf = (char *)__get_free_page(GFP_KERNEL);
528		if (!kbuf)
529			return wrote ? wrote : -ENOMEM;
530		while (count > 0) {
531			unsigned long sz = size_inside_page(p, count);
532			unsigned long n;
533
534			if (!is_vmalloc_or_module_addr((void *)p)) {
535				err = -ENXIO;
536				break;
537			}
538			n = copy_from_user(kbuf, buf, sz);
539			if (n) {
540				err = -EFAULT;
541				break;
542			}
543			vwrite(kbuf, (char *)p, sz);
544			count -= sz;
545			buf += sz;
546			virtr += sz;
547			p += sz;
548		}
549		free_page((unsigned long)kbuf);
550	}
551
552	*ppos = p;
553	return virtr + wrote ? : err;
554}
555
556static ssize_t read_port(struct file *file, char __user *buf,
557			 size_t count, loff_t *ppos)
558{
559	unsigned long i = *ppos;
560	char __user *tmp = buf;
561
562	if (!access_ok(VERIFY_WRITE, buf, count))
563		return -EFAULT;
564	while (count-- > 0 && i < 65536) {
565		if (__put_user(inb(i), tmp) < 0)
566			return -EFAULT;
567		i++;
568		tmp++;
569	}
570	*ppos = i;
571	return tmp-buf;
572}
573
574static ssize_t write_port(struct file *file, const char __user *buf,
575			  size_t count, loff_t *ppos)
576{
577	unsigned long i = *ppos;
578	const char __user *tmp = buf;
579
580	if (!access_ok(VERIFY_READ, buf, count))
581		return -EFAULT;
582	while (count-- > 0 && i < 65536) {
583		char c;
584
585		if (__get_user(c, tmp)) {
586			if (tmp > buf)
587				break;
588			return -EFAULT;
589		}
590		outb(c, i);
591		i++;
592		tmp++;
593	}
594	*ppos = i;
595	return tmp-buf;
596}
597
598static ssize_t read_null(struct file *file, char __user *buf,
599			 size_t count, loff_t *ppos)
600{
601	return 0;
602}
603
604static ssize_t write_null(struct file *file, const char __user *buf,
605			  size_t count, loff_t *ppos)
606{
607	return count;
608}
609
610static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)
611{
612	return 0;
613}
614
615static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
616{
617	size_t count = iov_iter_count(from);
618	iov_iter_advance(from, count);
619	return count;
620}
621
622static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
623			struct splice_desc *sd)
624{
625	return sd->len;
626}
627
628static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
629				 loff_t *ppos, size_t len, unsigned int flags)
630{
631	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
632}
633
 
 
 
 
 
634static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
635{
636	size_t written = 0;
637
638	while (iov_iter_count(iter)) {
639		size_t chunk = iov_iter_count(iter), n;
640
641		if (chunk > PAGE_SIZE)
642			chunk = PAGE_SIZE;	/* Just for latency reasons */
643		n = iov_iter_zero(chunk, iter);
644		if (!n && iov_iter_count(iter))
645			return written ? written : -EFAULT;
646		written += n;
647		if (signal_pending(current))
648			return written ? written : -ERESTARTSYS;
 
 
 
 
649		cond_resched();
650	}
651	return written;
652}
653
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
654static int mmap_zero(struct file *file, struct vm_area_struct *vma)
655{
656#ifndef CONFIG_MMU
657	return -ENOSYS;
658#endif
659	if (vma->vm_flags & VM_SHARED)
660		return shmem_zero_setup(vma);
 
661	return 0;
662}
663
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
664static ssize_t write_full(struct file *file, const char __user *buf,
665			  size_t count, loff_t *ppos)
666{
667	return -ENOSPC;
668}
669
670/*
671 * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
672 * can fopen() both devices with "a" now.  This was previously impossible.
673 * -- SRB.
674 */
675static loff_t null_lseek(struct file *file, loff_t offset, int orig)
676{
677	return file->f_pos = 0;
678}
679
680/*
681 * The memory devices use the full 32/64 bits of the offset, and so we cannot
682 * check against negative addresses: they are ok. The return value is weird,
683 * though, in that case (0).
684 *
685 * also note that seeking relative to the "end of file" isn't supported:
686 * it has no meaning, so it returns -EINVAL.
687 */
688static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
689{
690	loff_t ret;
691
692	inode_lock(file_inode(file));
693	switch (orig) {
694	case SEEK_CUR:
695		offset += file->f_pos;
 
696	case SEEK_SET:
697		/* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
698		if ((unsigned long long)offset >= -MAX_ERRNO) {
699			ret = -EOVERFLOW;
700			break;
701		}
702		file->f_pos = offset;
703		ret = file->f_pos;
704		force_successful_syscall_return();
705		break;
706	default:
707		ret = -EINVAL;
708	}
709	inode_unlock(file_inode(file));
710	return ret;
711}
712
713static int open_port(struct inode *inode, struct file *filp)
714{
715	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
716}
717
718#define zero_lseek	null_lseek
719#define full_lseek      null_lseek
720#define write_zero	write_null
721#define write_iter_zero	write_iter_null
722#define open_mem	open_port
723#define open_kmem	open_mem
724
725static const struct file_operations __maybe_unused mem_fops = {
726	.llseek		= memory_lseek,
727	.read		= read_mem,
728	.write		= write_mem,
729	.mmap		= mmap_mem,
730	.open		= open_mem,
731#ifndef CONFIG_MMU
732	.get_unmapped_area = get_unmapped_area_mem,
733	.mmap_capabilities = memory_mmap_capabilities,
734#endif
735};
736
737static const struct file_operations __maybe_unused kmem_fops = {
738	.llseek		= memory_lseek,
739	.read		= read_kmem,
740	.write		= write_kmem,
741	.mmap		= mmap_kmem,
742	.open		= open_kmem,
743#ifndef CONFIG_MMU
744	.get_unmapped_area = get_unmapped_area_mem,
745	.mmap_capabilities = memory_mmap_capabilities,
746#endif
747};
748
749static const struct file_operations null_fops = {
750	.llseek		= null_lseek,
751	.read		= read_null,
752	.write		= write_null,
753	.read_iter	= read_iter_null,
754	.write_iter	= write_iter_null,
755	.splice_write	= splice_write_null,
 
756};
757
758static const struct file_operations __maybe_unused port_fops = {
759	.llseek		= memory_lseek,
760	.read		= read_port,
761	.write		= write_port,
762	.open		= open_port,
763};
764
765static const struct file_operations zero_fops = {
766	.llseek		= zero_lseek,
767	.write		= write_zero,
768	.read_iter	= read_iter_zero,
 
769	.write_iter	= write_iter_zero,
770	.mmap		= mmap_zero,
 
771#ifndef CONFIG_MMU
772	.mmap_capabilities = zero_mmap_capabilities,
773#endif
774};
775
776static const struct file_operations full_fops = {
777	.llseek		= full_lseek,
778	.read_iter	= read_iter_zero,
779	.write		= write_full,
780};
781
782static const struct memdev {
783	const char *name;
784	umode_t mode;
785	const struct file_operations *fops;
786	fmode_t fmode;
787} devlist[] = {
788#ifdef CONFIG_DEVMEM
789	 [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },
790#endif
791#ifdef CONFIG_DEVKMEM
792	 [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET },
793#endif
794	 [3] = { "null", 0666, &null_fops, 0 },
795#ifdef CONFIG_DEVPORT
796	 [4] = { "port", 0, &port_fops, 0 },
797#endif
798	 [5] = { "zero", 0666, &zero_fops, 0 },
799	 [7] = { "full", 0666, &full_fops, 0 },
800	 [8] = { "random", 0666, &random_fops, 0 },
801	 [9] = { "urandom", 0666, &urandom_fops, 0 },
802#ifdef CONFIG_PRINTK
803	[11] = { "kmsg", 0644, &kmsg_fops, 0 },
804#endif
805};
806
807static int memory_open(struct inode *inode, struct file *filp)
808{
809	int minor;
810	const struct memdev *dev;
811
812	minor = iminor(inode);
813	if (minor >= ARRAY_SIZE(devlist))
814		return -ENXIO;
815
816	dev = &devlist[minor];
817	if (!dev->fops)
818		return -ENXIO;
819
820	filp->f_op = dev->fops;
821	filp->f_mode |= dev->fmode;
822
823	if (dev->fops->open)
824		return dev->fops->open(inode, filp);
825
826	return 0;
827}
828
829static const struct file_operations memory_fops = {
830	.open = memory_open,
831	.llseek = noop_llseek,
832};
833
834static char *mem_devnode(struct device *dev, umode_t *mode)
835{
836	if (mode && devlist[MINOR(dev->devt)].mode)
837		*mode = devlist[MINOR(dev->devt)].mode;
838	return NULL;
839}
840
841static struct class *mem_class;
842
843static int __init chr_dev_init(void)
844{
845	int minor;
846
847	if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
848		printk("unable to get major %d for memory devs\n", MEM_MAJOR);
849
850	mem_class = class_create(THIS_MODULE, "mem");
851	if (IS_ERR(mem_class))
852		return PTR_ERR(mem_class);
853
854	mem_class->devnode = mem_devnode;
855	for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
856		if (!devlist[minor].name)
857			continue;
858
859		/*
860		 * Create /dev/port?
861		 */
862		if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
863			continue;
864
865		device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
866			      NULL, devlist[minor].name);
867	}
868
869	return tty_init();
870}
871
872fs_initcall(chr_dev_init);