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/raw.h>
20 #include <linux/tty.h>
21 #include <linux/capability.h>
22 #include <linux/ptrace.h>
23 #include <linux/device.h>
24 #include <linux/highmem.h>
25 #include <linux/backing-dev.h>
26 #include <linux/shmem_fs.h>
27 #include <linux/splice.h>
28 #include <linux/pfn.h>
29 #include <linux/export.h>
30 #include <linux/io.h>
31 #include <linux/uio.h>
32 
33 #include <linux/uaccess.h>
34 
35 #ifdef CONFIG_IA64
36 # include <linux/efi.h>
37 #endif
38 
39 #define DEVPORT_MINOR	4
40 
size_inside_page(unsigned long start,unsigned long size)41 static 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
valid_phys_addr_range(phys_addr_t addr,size_t count)52 static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)
53 {
54 	return addr + count <= __pa(high_memory);
55 }
56 
valid_mmap_phys_addr_range(unsigned long pfn,size_t size)57 static 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
page_is_allowed(unsigned long pfn)64 static inline int page_is_allowed(unsigned long pfn)
65 {
66 	return devmem_is_allowed(pfn);
67 }
range_is_allowed(unsigned long pfn,unsigned long size)68 static 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
page_is_allowed(unsigned long pfn)83 static inline int page_is_allowed(unsigned long pfn)
84 {
85 	return 1;
86 }
range_is_allowed(unsigned long pfn,unsigned long size)87 static 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
unxlate_dev_mem_ptr(phys_addr_t phys,void * addr)95 void __weak unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
96 {
97 }
98 #endif
99 
should_stop_iteration(void)100 static inline bool should_stop_iteration(void)
101 {
102 	if (need_resched())
103 		cond_resched();
104 	return fatal_signal_pending(current);
105 }
106 
107 /*
108  * This funcion reads the *physical* memory. The f_pos points directly to the
109  * memory location.
110  */
read_mem(struct file * file,char __user * buf,size_t count,loff_t * ppos)111 static 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 = probe_kernel_read(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 
193 failed:
194 	kfree(bounce);
195 	return err;
196 }
197 
write_mem(struct file * file,const char __user * buf,size_t count,loff_t * ppos)198 static 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 
phys_mem_access_prot_allowed(struct file * file,unsigned long pfn,unsigned long size,pgprot_t * vma_prot)271 int __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
uncached_access(struct file * file,phys_addr_t addr)285 static 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 #elif defined(CONFIG_MIPS)
294 	{
295 		extern int __uncached_access(struct file *file,
296 					     unsigned long addr);
297 
298 		return __uncached_access(file, addr);
299 	}
300 #else
301 	/*
302 	 * Accessing memory above the top the kernel knows about or through a
303 	 * file pointer
304 	 * that was marked O_DSYNC will be done non-cached.
305 	 */
306 	if (file->f_flags & O_DSYNC)
307 		return 1;
308 	return addr >= __pa(high_memory);
309 #endif
310 }
311 #endif
312 
phys_mem_access_prot(struct file * file,unsigned long pfn,unsigned long size,pgprot_t vma_prot)313 static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
314 				     unsigned long size, pgprot_t vma_prot)
315 {
316 #ifdef pgprot_noncached
317 	phys_addr_t offset = pfn << PAGE_SHIFT;
318 
319 	if (uncached_access(file, offset))
320 		return pgprot_noncached(vma_prot);
321 #endif
322 	return vma_prot;
323 }
324 #endif
325 
326 #ifndef CONFIG_MMU
get_unmapped_area_mem(struct file * file,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)327 static unsigned long get_unmapped_area_mem(struct file *file,
328 					   unsigned long addr,
329 					   unsigned long len,
330 					   unsigned long pgoff,
331 					   unsigned long flags)
332 {
333 	if (!valid_mmap_phys_addr_range(pgoff, len))
334 		return (unsigned long) -EINVAL;
335 	return pgoff << PAGE_SHIFT;
336 }
337 
338 /* permit direct mmap, for read, write or exec */
memory_mmap_capabilities(struct file * file)339 static unsigned memory_mmap_capabilities(struct file *file)
340 {
341 	return NOMMU_MAP_DIRECT |
342 		NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
343 }
344 
zero_mmap_capabilities(struct file * file)345 static unsigned zero_mmap_capabilities(struct file *file)
346 {
347 	return NOMMU_MAP_COPY;
348 }
349 
350 /* can't do an in-place private mapping if there's no MMU */
private_mapping_ok(struct vm_area_struct * vma)351 static inline int private_mapping_ok(struct vm_area_struct *vma)
352 {
353 	return vma->vm_flags & VM_MAYSHARE;
354 }
355 #else
356 
private_mapping_ok(struct vm_area_struct * vma)357 static inline int private_mapping_ok(struct vm_area_struct *vma)
358 {
359 	return 1;
360 }
361 #endif
362 
363 static const struct vm_operations_struct mmap_mem_ops = {
364 #ifdef CONFIG_HAVE_IOREMAP_PROT
365 	.access = generic_access_phys
366 #endif
367 };
368 
mmap_mem(struct file * file,struct vm_area_struct * vma)369 static int mmap_mem(struct file *file, struct vm_area_struct *vma)
370 {
371 	size_t size = vma->vm_end - vma->vm_start;
372 	phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
373 
374 	/* Does it even fit in phys_addr_t? */
375 	if (offset >> PAGE_SHIFT != vma->vm_pgoff)
376 		return -EINVAL;
377 
378 	/* It's illegal to wrap around the end of the physical address space. */
379 	if (offset + (phys_addr_t)size - 1 < offset)
380 		return -EINVAL;
381 
382 	if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
383 		return -EINVAL;
384 
385 	if (!private_mapping_ok(vma))
386 		return -ENOSYS;
387 
388 	if (!range_is_allowed(vma->vm_pgoff, size))
389 		return -EPERM;
390 
391 	if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,
392 						&vma->vm_page_prot))
393 		return -EINVAL;
394 
395 	vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
396 						 size,
397 						 vma->vm_page_prot);
398 
399 	vma->vm_ops = &mmap_mem_ops;
400 
401 	/* Remap-pfn-range will mark the range VM_IO */
402 	if (remap_pfn_range(vma,
403 			    vma->vm_start,
404 			    vma->vm_pgoff,
405 			    size,
406 			    vma->vm_page_prot)) {
407 		return -EAGAIN;
408 	}
409 	return 0;
410 }
411 
mmap_kmem(struct file * file,struct vm_area_struct * vma)412 static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
413 {
414 	unsigned long pfn;
415 
416 	/* Turn a kernel-virtual address into a physical page frame */
417 	pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
418 
419 	/*
420 	 * RED-PEN: on some architectures there is more mapped memory than
421 	 * available in mem_map which pfn_valid checks for. Perhaps should add a
422 	 * new macro here.
423 	 *
424 	 * RED-PEN: vmalloc is not supported right now.
425 	 */
426 	if (!pfn_valid(pfn))
427 		return -EIO;
428 
429 	vma->vm_pgoff = pfn;
430 	return mmap_mem(file, vma);
431 }
432 
433 /*
434  * This function reads the *virtual* memory as seen by the kernel.
435  */
read_kmem(struct file * file,char __user * buf,size_t count,loff_t * ppos)436 static ssize_t read_kmem(struct file *file, char __user *buf,
437 			 size_t count, loff_t *ppos)
438 {
439 	unsigned long p = *ppos;
440 	ssize_t low_count, read, sz;
441 	char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
442 	int err = 0;
443 
444 	read = 0;
445 	if (p < (unsigned long) high_memory) {
446 		low_count = count;
447 		if (count > (unsigned long)high_memory - p)
448 			low_count = (unsigned long)high_memory - p;
449 
450 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
451 		/* we don't have page 0 mapped on sparc and m68k.. */
452 		if (p < PAGE_SIZE && low_count > 0) {
453 			sz = size_inside_page(p, low_count);
454 			if (clear_user(buf, sz))
455 				return -EFAULT;
456 			buf += sz;
457 			p += sz;
458 			read += sz;
459 			low_count -= sz;
460 			count -= sz;
461 		}
462 #endif
463 		while (low_count > 0) {
464 			sz = size_inside_page(p, low_count);
465 
466 			/*
467 			 * On ia64 if a page has been mapped somewhere as
468 			 * uncached, then it must also be accessed uncached
469 			 * by the kernel or data corruption may occur
470 			 */
471 			kbuf = xlate_dev_kmem_ptr((void *)p);
472 			if (!virt_addr_valid(kbuf))
473 				return -ENXIO;
474 
475 			if (copy_to_user(buf, kbuf, sz))
476 				return -EFAULT;
477 			buf += sz;
478 			p += sz;
479 			read += sz;
480 			low_count -= sz;
481 			count -= sz;
482 			if (should_stop_iteration()) {
483 				count = 0;
484 				break;
485 			}
486 		}
487 	}
488 
489 	if (count > 0) {
490 		kbuf = (char *)__get_free_page(GFP_KERNEL);
491 		if (!kbuf)
492 			return -ENOMEM;
493 		while (count > 0) {
494 			sz = size_inside_page(p, count);
495 			if (!is_vmalloc_or_module_addr((void *)p)) {
496 				err = -ENXIO;
497 				break;
498 			}
499 			sz = vread(kbuf, (char *)p, sz);
500 			if (!sz)
501 				break;
502 			if (copy_to_user(buf, kbuf, sz)) {
503 				err = -EFAULT;
504 				break;
505 			}
506 			count -= sz;
507 			buf += sz;
508 			read += sz;
509 			p += sz;
510 			if (should_stop_iteration())
511 				break;
512 		}
513 		free_page((unsigned long)kbuf);
514 	}
515 	*ppos = p;
516 	return read ? read : err;
517 }
518 
519 
do_write_kmem(unsigned long p,const char __user * buf,size_t count,loff_t * ppos)520 static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
521 				size_t count, loff_t *ppos)
522 {
523 	ssize_t written, sz;
524 	unsigned long copied;
525 
526 	written = 0;
527 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
528 	/* we don't have page 0 mapped on sparc and m68k.. */
529 	if (p < PAGE_SIZE) {
530 		sz = size_inside_page(p, count);
531 		/* Hmm. Do something? */
532 		buf += sz;
533 		p += sz;
534 		count -= sz;
535 		written += sz;
536 	}
537 #endif
538 
539 	while (count > 0) {
540 		void *ptr;
541 
542 		sz = size_inside_page(p, count);
543 
544 		/*
545 		 * On ia64 if a page has been mapped somewhere as uncached, then
546 		 * it must also be accessed uncached by the kernel or data
547 		 * corruption may occur.
548 		 */
549 		ptr = xlate_dev_kmem_ptr((void *)p);
550 		if (!virt_addr_valid(ptr))
551 			return -ENXIO;
552 
553 		copied = copy_from_user(ptr, buf, sz);
554 		if (copied) {
555 			written += sz - copied;
556 			if (written)
557 				break;
558 			return -EFAULT;
559 		}
560 		buf += sz;
561 		p += sz;
562 		count -= sz;
563 		written += sz;
564 		if (should_stop_iteration())
565 			break;
566 	}
567 
568 	*ppos += written;
569 	return written;
570 }
571 
572 /*
573  * This function writes to the *virtual* memory as seen by the kernel.
574  */
write_kmem(struct file * file,const char __user * buf,size_t count,loff_t * ppos)575 static ssize_t write_kmem(struct file *file, const char __user *buf,
576 			  size_t count, loff_t *ppos)
577 {
578 	unsigned long p = *ppos;
579 	ssize_t wrote = 0;
580 	ssize_t virtr = 0;
581 	char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
582 	int err = 0;
583 
584 	if (p < (unsigned long) high_memory) {
585 		unsigned long to_write = min_t(unsigned long, count,
586 					       (unsigned long)high_memory - p);
587 		wrote = do_write_kmem(p, buf, to_write, ppos);
588 		if (wrote != to_write)
589 			return wrote;
590 		p += wrote;
591 		buf += wrote;
592 		count -= wrote;
593 	}
594 
595 	if (count > 0) {
596 		kbuf = (char *)__get_free_page(GFP_KERNEL);
597 		if (!kbuf)
598 			return wrote ? wrote : -ENOMEM;
599 		while (count > 0) {
600 			unsigned long sz = size_inside_page(p, count);
601 			unsigned long n;
602 
603 			if (!is_vmalloc_or_module_addr((void *)p)) {
604 				err = -ENXIO;
605 				break;
606 			}
607 			n = copy_from_user(kbuf, buf, sz);
608 			if (n) {
609 				err = -EFAULT;
610 				break;
611 			}
612 			vwrite(kbuf, (char *)p, sz);
613 			count -= sz;
614 			buf += sz;
615 			virtr += sz;
616 			p += sz;
617 			if (should_stop_iteration())
618 				break;
619 		}
620 		free_page((unsigned long)kbuf);
621 	}
622 
623 	*ppos = p;
624 	return virtr + wrote ? : err;
625 }
626 
read_port(struct file * file,char __user * buf,size_t count,loff_t * ppos)627 static ssize_t read_port(struct file *file, char __user *buf,
628 			 size_t count, loff_t *ppos)
629 {
630 	unsigned long i = *ppos;
631 	char __user *tmp = buf;
632 
633 	if (!access_ok(VERIFY_WRITE, buf, count))
634 		return -EFAULT;
635 	while (count-- > 0 && i < 65536) {
636 		if (__put_user(inb(i), tmp) < 0)
637 			return -EFAULT;
638 		i++;
639 		tmp++;
640 	}
641 	*ppos = i;
642 	return tmp-buf;
643 }
644 
write_port(struct file * file,const char __user * buf,size_t count,loff_t * ppos)645 static ssize_t write_port(struct file *file, const char __user *buf,
646 			  size_t count, loff_t *ppos)
647 {
648 	unsigned long i = *ppos;
649 	const char __user *tmp = buf;
650 
651 	if (!access_ok(VERIFY_READ, buf, count))
652 		return -EFAULT;
653 	while (count-- > 0 && i < 65536) {
654 		char c;
655 
656 		if (__get_user(c, tmp)) {
657 			if (tmp > buf)
658 				break;
659 			return -EFAULT;
660 		}
661 		outb(c, i);
662 		i++;
663 		tmp++;
664 	}
665 	*ppos = i;
666 	return tmp-buf;
667 }
668 
read_null(struct file * file,char __user * buf,size_t count,loff_t * ppos)669 static ssize_t read_null(struct file *file, char __user *buf,
670 			 size_t count, loff_t *ppos)
671 {
672 	return 0;
673 }
674 
write_null(struct file * file,const char __user * buf,size_t count,loff_t * ppos)675 static ssize_t write_null(struct file *file, const char __user *buf,
676 			  size_t count, loff_t *ppos)
677 {
678 	return count;
679 }
680 
read_iter_null(struct kiocb * iocb,struct iov_iter * to)681 static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)
682 {
683 	return 0;
684 }
685 
write_iter_null(struct kiocb * iocb,struct iov_iter * from)686 static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
687 {
688 	size_t count = iov_iter_count(from);
689 	iov_iter_advance(from, count);
690 	return count;
691 }
692 
pipe_to_null(struct pipe_inode_info * info,struct pipe_buffer * buf,struct splice_desc * sd)693 static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
694 			struct splice_desc *sd)
695 {
696 	return sd->len;
697 }
698 
splice_write_null(struct pipe_inode_info * pipe,struct file * out,loff_t * ppos,size_t len,unsigned int flags)699 static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
700 				 loff_t *ppos, size_t len, unsigned int flags)
701 {
702 	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
703 }
704 
read_iter_zero(struct kiocb * iocb,struct iov_iter * iter)705 static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
706 {
707 	size_t written = 0;
708 
709 	while (iov_iter_count(iter)) {
710 		size_t chunk = iov_iter_count(iter), n;
711 
712 		if (chunk > PAGE_SIZE)
713 			chunk = PAGE_SIZE;	/* Just for latency reasons */
714 		n = iov_iter_zero(chunk, iter);
715 		if (!n && iov_iter_count(iter))
716 			return written ? written : -EFAULT;
717 		written += n;
718 		if (signal_pending(current))
719 			return written ? written : -ERESTARTSYS;
720 		cond_resched();
721 	}
722 	return written;
723 }
724 
mmap_zero(struct file * file,struct vm_area_struct * vma)725 static int mmap_zero(struct file *file, struct vm_area_struct *vma)
726 {
727 #ifndef CONFIG_MMU
728 	return -ENOSYS;
729 #endif
730 	if (vma->vm_flags & VM_SHARED)
731 		return shmem_zero_setup(vma);
732 	vma_set_anonymous(vma);
733 	return 0;
734 }
735 
get_unmapped_area_zero(struct file * file,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)736 static unsigned long get_unmapped_area_zero(struct file *file,
737 				unsigned long addr, unsigned long len,
738 				unsigned long pgoff, unsigned long flags)
739 {
740 #ifdef CONFIG_MMU
741 	if (flags & MAP_SHARED) {
742 		/*
743 		 * mmap_zero() will call shmem_zero_setup() to create a file,
744 		 * so use shmem's get_unmapped_area in case it can be huge;
745 		 * and pass NULL for file as in mmap.c's get_unmapped_area(),
746 		 * so as not to confuse shmem with our handle on "/dev/zero".
747 		 */
748 		return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags);
749 	}
750 
751 	/* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */
752 	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
753 #else
754 	return -ENOSYS;
755 #endif
756 }
757 
write_full(struct file * file,const char __user * buf,size_t count,loff_t * ppos)758 static ssize_t write_full(struct file *file, const char __user *buf,
759 			  size_t count, loff_t *ppos)
760 {
761 	return -ENOSPC;
762 }
763 
764 /*
765  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
766  * can fopen() both devices with "a" now.  This was previously impossible.
767  * -- SRB.
768  */
null_lseek(struct file * file,loff_t offset,int orig)769 static loff_t null_lseek(struct file *file, loff_t offset, int orig)
770 {
771 	return file->f_pos = 0;
772 }
773 
774 /*
775  * The memory devices use the full 32/64 bits of the offset, and so we cannot
776  * check against negative addresses: they are ok. The return value is weird,
777  * though, in that case (0).
778  *
779  * also note that seeking relative to the "end of file" isn't supported:
780  * it has no meaning, so it returns -EINVAL.
781  */
memory_lseek(struct file * file,loff_t offset,int orig)782 static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
783 {
784 	loff_t ret;
785 
786 	inode_lock(file_inode(file));
787 	switch (orig) {
788 	case SEEK_CUR:
789 		offset += file->f_pos;
790 		/* fall through */
791 	case SEEK_SET:
792 		/* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
793 		if ((unsigned long long)offset >= -MAX_ERRNO) {
794 			ret = -EOVERFLOW;
795 			break;
796 		}
797 		file->f_pos = offset;
798 		ret = file->f_pos;
799 		force_successful_syscall_return();
800 		break;
801 	default:
802 		ret = -EINVAL;
803 	}
804 	inode_unlock(file_inode(file));
805 	return ret;
806 }
807 
open_port(struct inode * inode,struct file * filp)808 static int open_port(struct inode *inode, struct file *filp)
809 {
810 	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
811 }
812 
813 #define zero_lseek	null_lseek
814 #define full_lseek      null_lseek
815 #define write_zero	write_null
816 #define write_iter_zero	write_iter_null
817 #define open_mem	open_port
818 #define open_kmem	open_mem
819 
820 static const struct file_operations __maybe_unused mem_fops = {
821 	.llseek		= memory_lseek,
822 	.read		= read_mem,
823 	.write		= write_mem,
824 	.mmap		= mmap_mem,
825 	.open		= open_mem,
826 #ifndef CONFIG_MMU
827 	.get_unmapped_area = get_unmapped_area_mem,
828 	.mmap_capabilities = memory_mmap_capabilities,
829 #endif
830 };
831 
832 static const struct file_operations __maybe_unused kmem_fops = {
833 	.llseek		= memory_lseek,
834 	.read		= read_kmem,
835 	.write		= write_kmem,
836 	.mmap		= mmap_kmem,
837 	.open		= open_kmem,
838 #ifndef CONFIG_MMU
839 	.get_unmapped_area = get_unmapped_area_mem,
840 	.mmap_capabilities = memory_mmap_capabilities,
841 #endif
842 };
843 
844 static const struct file_operations null_fops = {
845 	.llseek		= null_lseek,
846 	.read		= read_null,
847 	.write		= write_null,
848 	.read_iter	= read_iter_null,
849 	.write_iter	= write_iter_null,
850 	.splice_write	= splice_write_null,
851 };
852 
853 static const struct file_operations __maybe_unused port_fops = {
854 	.llseek		= memory_lseek,
855 	.read		= read_port,
856 	.write		= write_port,
857 	.open		= open_port,
858 };
859 
860 static const struct file_operations zero_fops = {
861 	.llseek		= zero_lseek,
862 	.write		= write_zero,
863 	.read_iter	= read_iter_zero,
864 	.write_iter	= write_iter_zero,
865 	.mmap		= mmap_zero,
866 	.get_unmapped_area = get_unmapped_area_zero,
867 #ifndef CONFIG_MMU
868 	.mmap_capabilities = zero_mmap_capabilities,
869 #endif
870 };
871 
872 static const struct file_operations full_fops = {
873 	.llseek		= full_lseek,
874 	.read_iter	= read_iter_zero,
875 	.write		= write_full,
876 };
877 
878 static const struct memdev {
879 	const char *name;
880 	umode_t mode;
881 	const struct file_operations *fops;
882 	fmode_t fmode;
883 } devlist[] = {
884 #ifdef CONFIG_DEVMEM
885 	 [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET },
886 #endif
887 #ifdef CONFIG_DEVKMEM
888 	 [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET },
889 #endif
890 	 [3] = { "null", 0666, &null_fops, 0 },
891 #ifdef CONFIG_DEVPORT
892 	 [4] = { "port", 0, &port_fops, 0 },
893 #endif
894 	 [5] = { "zero", 0666, &zero_fops, 0 },
895 	 [7] = { "full", 0666, &full_fops, 0 },
896 	 [8] = { "random", 0666, &random_fops, FMODE_NOWAIT },
897 	 [9] = { "urandom", 0666, &urandom_fops, FMODE_NOWAIT },
898 #ifdef CONFIG_PRINTK
899 	[11] = { "kmsg", 0644, &kmsg_fops, 0 },
900 #endif
901 };
902 
memory_open(struct inode * inode,struct file * filp)903 static int memory_open(struct inode *inode, struct file *filp)
904 {
905 	int minor;
906 	const struct memdev *dev;
907 
908 	minor = iminor(inode);
909 	if (minor >= ARRAY_SIZE(devlist))
910 		return -ENXIO;
911 
912 	dev = &devlist[minor];
913 	if (!dev->fops)
914 		return -ENXIO;
915 
916 	filp->f_op = dev->fops;
917 	filp->f_mode |= dev->fmode;
918 
919 	if (dev->fops->open)
920 		return dev->fops->open(inode, filp);
921 
922 	return 0;
923 }
924 
925 static const struct file_operations memory_fops = {
926 	.open = memory_open,
927 	.llseek = noop_llseek,
928 };
929 
mem_devnode(struct device * dev,umode_t * mode)930 static char *mem_devnode(struct device *dev, umode_t *mode)
931 {
932 	if (mode && devlist[MINOR(dev->devt)].mode)
933 		*mode = devlist[MINOR(dev->devt)].mode;
934 	return NULL;
935 }
936 
937 static struct class *mem_class;
938 
chr_dev_init(void)939 static int __init chr_dev_init(void)
940 {
941 	int minor;
942 
943 	if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
944 		printk("unable to get major %d for memory devs\n", MEM_MAJOR);
945 
946 	mem_class = class_create(THIS_MODULE, "mem");
947 	if (IS_ERR(mem_class))
948 		return PTR_ERR(mem_class);
949 
950 	mem_class->devnode = mem_devnode;
951 	for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
952 		if (!devlist[minor].name)
953 			continue;
954 
955 		/*
956 		 * Create /dev/port?
957 		 */
958 		if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
959 			continue;
960 
961 		device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
962 			      NULL, devlist[minor].name);
963 	}
964 
965 	return tty_init();
966 }
967 
968 fs_initcall(chr_dev_init);
969