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1// SPDX-License-Identifier: GPL-2.02/*3 * linux/drivers/char/mem.c4 *5 * Copyright (C) 1991, 1992 Linus Torvalds6 *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#define DEVMEM_MINOR 135#define DEVPORT_MINOR 436 37static inline unsigned long size_inside_page(unsigned long start,38 unsigned long size)39{40 unsigned long sz;41 42 sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));43 44 return min(sz, size);45}46 47#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE48static inline int valid_phys_addr_range(phys_addr_t addr, size_t count)49{50 return addr + count <= __pa(high_memory);51}52 53static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)54{55 return 1;56}57#endif58 59#ifdef CONFIG_STRICT_DEVMEM60static inline int page_is_allowed(unsigned long pfn)61{62 return devmem_is_allowed(pfn);63}64static inline int range_is_allowed(unsigned long pfn, unsigned long size)65{66 u64 from = ((u64)pfn) << PAGE_SHIFT;67 u64 to = from + size;68 u64 cursor = from;69 70 while (cursor < to) {71 if (!devmem_is_allowed(pfn))72 return 0;73 cursor += PAGE_SIZE;74 pfn++;75 }76 return 1;77}78#else79static inline int page_is_allowed(unsigned long pfn)80{81 return 1;82}83static inline int range_is_allowed(unsigned long pfn, unsigned long size)84{85 return 1;86}87#endif88 89static inline bool should_stop_iteration(void)90{91 if (need_resched())92 cond_resched();93 return signal_pending(current);94}95 96/*97 * This funcion reads the *physical* memory. The f_pos points directly to the98 * memory location.99 */100static HWJS_SUSPENDS ssize_t read_mem(struct file *file, char __user *buf,101 size_t count, loff_t *ppos)102{103 phys_addr_t p = *ppos;104 ssize_t read, sz;105 void *ptr;106 char *bounce;107 int err;108 109 if (p != *ppos)110 return 0;111 112 if (!valid_phys_addr_range(p, count))113 return -EFAULT;114 read = 0;115#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED116 /* we don't have page 0 mapped on sparc and m68k.. */117 if (p < PAGE_SIZE) {118 sz = size_inside_page(p, count);119 if (sz > 0) {120 if (clear_user(buf, sz))121 return -EFAULT;122 buf += sz;123 p += sz;124 count -= sz;125 read += sz;126 }127 }128#endif129 130 bounce = kmalloc(PAGE_SIZE, GFP_KERNEL);131 if (!bounce)132 return -ENOMEM;133 134 while (count > 0) {135 unsigned long remaining;136 int allowed, probe;137 138 sz = size_inside_page(p, count);139 140 err = -EPERM;141 allowed = page_is_allowed(p >> PAGE_SHIFT);142 if (!allowed)143 goto failed;144 145 err = -EFAULT;146 if (allowed == 2) {147 /* Show zeros for restricted memory. */148 remaining = clear_user(buf, sz);149 } else {150 /*151 * On ia64 if a page has been mapped somewhere as152 * uncached, then it must also be accessed uncached153 * by the kernel or data corruption may occur.154 */155 ptr = xlate_dev_mem_ptr(p);156 if (!ptr)157 goto failed;158 159 probe = copy_from_kernel_nofault(bounce, ptr, sz);160 unxlate_dev_mem_ptr(p, ptr);161 if (probe)162 goto failed;163 164 remaining = copy_to_user(buf, bounce, sz);165 }166 167 if (remaining)168 goto failed;169 170 buf += sz;171 p += sz;172 count -= sz;173 read += sz;174 if (should_stop_iteration())175 break;176 }177 kfree(bounce);178 179 *ppos += read;180 return read;181 182failed:183 kfree(bounce);184 return err;185}186 187static HWJS_SUSPENDS ssize_t write_mem(struct file *file, const char __user *buf,188 size_t count, loff_t *ppos)189{190 phys_addr_t p = *ppos;191 ssize_t written, sz;192 unsigned long copied;193 void *ptr;194 195 if (p != *ppos)196 return -EFBIG;197 198 if (!valid_phys_addr_range(p, count))199 return -EFAULT;200 201 written = 0;202 203#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED204 /* we don't have page 0 mapped on sparc and m68k.. */205 if (p < PAGE_SIZE) {206 sz = size_inside_page(p, count);207 /* Hmm. Do something? */208 buf += sz;209 p += sz;210 count -= sz;211 written += sz;212 }213#endif214 215 while (count > 0) {216 int allowed;217 218 sz = size_inside_page(p, count);219 220 allowed = page_is_allowed(p >> PAGE_SHIFT);221 if (!allowed)222 return -EPERM;223 224 /* Skip actual writing when a page is marked as restricted. */225 if (allowed == 1) {226 /*227 * On ia64 if a page has been mapped somewhere as228 * uncached, then it must also be accessed uncached229 * by the kernel or data corruption may occur.230 */231 ptr = xlate_dev_mem_ptr(p);232 if (!ptr) {233 if (written)234 break;235 return -EFAULT;236 }237 238 copied = copy_from_user(ptr, buf, sz);239 unxlate_dev_mem_ptr(p, ptr);240 if (copied) {241 written += sz - copied;242 if (written)243 break;244 return -EFAULT;245 }246 }247 248 buf += sz;249 p += sz;250 count -= sz;251 written += sz;252 if (should_stop_iteration())253 break;254 }255 256 *ppos += written;257 return written;258}259 260int __weak phys_mem_access_prot_allowed(struct file *file,261 unsigned long pfn, unsigned long size, pgprot_t *vma_prot)262{263 return 1;264}265 266#ifndef __HAVE_PHYS_MEM_ACCESS_PROT267 268/*269 * Architectures vary in how they handle caching for addresses270 * outside of main memory.271 *272 */273#ifdef pgprot_noncached274static int uncached_access(struct file *file, phys_addr_t addr)275{276 /*277 * Accessing memory above the top the kernel knows about or through a278 * file pointer279 * that was marked O_DSYNC will be done non-cached.280 */281 if (file->f_flags & O_DSYNC)282 return 1;283 return addr >= __pa(high_memory);284}285#endif286 287static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,288 unsigned long size, pgprot_t vma_prot)289{290#ifdef pgprot_noncached291 phys_addr_t offset = pfn << PAGE_SHIFT;292 293 if (uncached_access(file, offset))294 return pgprot_noncached(vma_prot);295#endif296 return vma_prot;297}298#endif299 300#ifndef CONFIG_MMU301static unsigned long get_unmapped_area_mem(struct file *file,302 unsigned long addr,303 unsigned long len,304 unsigned long pgoff,305 unsigned long flags)306{307 if (!valid_mmap_phys_addr_range(pgoff, len))308 return (unsigned long) -EINVAL;309 return pgoff << PAGE_SHIFT;310}311 312/* permit direct mmap, for read, write or exec */313static unsigned memory_mmap_capabilities(struct file *file)314{315 return NOMMU_MAP_DIRECT |316 NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;317}318 319static unsigned zero_mmap_capabilities(struct file *file)320{321 return NOMMU_MAP_COPY;322}323 324/* can't do an in-place private mapping if there's no MMU */325static inline int private_mapping_ok(struct vm_area_struct *vma)326{327 return is_nommu_shared_mapping(vma->vm_flags);328}329#else330 331static inline int private_mapping_ok(struct vm_area_struct *vma)332{333 return 1;334}335#endif336 337static const struct vm_operations_struct mmap_mem_ops = {338#ifdef CONFIG_HAVE_IOREMAP_PROT339 .access = generic_access_phys340#endif341};342 343static HWJS_SUSPENDS int mmap_mem(struct file *file, struct vm_area_struct *vma)344{345 size_t size = vma->vm_end - vma->vm_start;346 phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;347 348 /* Does it even fit in phys_addr_t? */349 if (offset >> PAGE_SHIFT != vma->vm_pgoff)350 return -EINVAL;351 352 /* It's illegal to wrap around the end of the physical address space. */353 if (offset + (phys_addr_t)size - 1 < offset)354 return -EINVAL;355 356 if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))357 return -EINVAL;358 359 if (!private_mapping_ok(vma))360 return -ENOSYS;361 362 if (!range_is_allowed(vma->vm_pgoff, size))363 return -EPERM;364 365 if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size,366 &vma->vm_page_prot))367 return -EINVAL;368 369 vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,370 size,371 vma->vm_page_prot);372 373 vma->vm_ops = &mmap_mem_ops;374 375 /* Remap-pfn-range will mark the range VM_IO */376 if (remap_pfn_range(vma,377 vma->vm_start,378 vma->vm_pgoff,379 size,380 vma->vm_page_prot)) {381 return -EAGAIN;382 }383 return 0;384}385 386#ifdef CONFIG_DEVPORT387static ssize_t read_port(struct file *file, char __user *buf,388 size_t count, loff_t *ppos)389{390 unsigned long i = *ppos;391 char __user *tmp = buf;392 393 if (!access_ok(buf, count))394 return -EFAULT;395 while (count-- > 0 && i < 65536) {396 if (__put_user(inb(i), tmp) < 0)397 return -EFAULT;398 i++;399 tmp++;400 }401 *ppos = i;402 return tmp-buf;403}404 405static ssize_t write_port(struct file *file, const char __user *buf,406 size_t count, loff_t *ppos)407{408 unsigned long i = *ppos;409 const char __user *tmp = buf;410 411 if (!access_ok(buf, count))412 return -EFAULT;413 while (count-- > 0 && i < 65536) {414 char c;415 416 if (__get_user(c, tmp)) {417 if (tmp > buf)418 break;419 return -EFAULT;420 }421 outb(c, i);422 i++;423 tmp++;424 }425 *ppos = i;426 return tmp-buf;427}428#endif429 430static ssize_t read_null(struct file *file, char __user *buf,431 size_t count, loff_t *ppos)432{433 return 0;434}435 436static ssize_t write_null(struct file *file, const char __user *buf,437 size_t count, loff_t *ppos)438{439 return count;440}441 442static ssize_t read_iter_null(struct kiocb *iocb, struct iov_iter *to)443{444 return 0;445}446 447static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)448{449 size_t count = iov_iter_count(from);450 iov_iter_advance(from, count);451 return count;452}453 454static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,455 struct splice_desc *sd)456{457 return sd->len;458}459 460static HWJS_SUSPENDS ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,461 loff_t *ppos, size_t len, unsigned int flags)462{463 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);464}465 466static int uring_cmd_null(struct io_uring_cmd *ioucmd, unsigned int issue_flags)467{468 return 0;469}470 471static HWJS_SUSPENDS ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)472{473 size_t written = 0;474 475 while (iov_iter_count(iter)) {476 size_t chunk = iov_iter_count(iter), n;477 478 if (chunk > PAGE_SIZE)479 chunk = PAGE_SIZE; /* Just for latency reasons */480 n = iov_iter_zero(chunk, iter);481 if (!n && iov_iter_count(iter))482 return written ? written : -EFAULT;483 written += n;484 if (signal_pending(current))485 return written ? written : -ERESTARTSYS;486 if (!need_resched())487 continue;488 if (iocb->ki_flags & IOCB_NOWAIT)489 return written ? written : -EAGAIN;490 cond_resched();491 }492 return written;493}494 495static HWJS_SUSPENDS ssize_t read_zero(struct file *file, char __user *buf,496 size_t count, loff_t *ppos)497{498 size_t cleared = 0;499 500 while (count) {501 size_t chunk = min_t(size_t, count, PAGE_SIZE);502 size_t left;503 504 left = clear_user(buf + cleared, chunk);505 if (unlikely(left)) {506 cleared += (chunk - left);507 if (!cleared)508 return -EFAULT;509 break;510 }511 cleared += chunk;512 count -= chunk;513 514 if (signal_pending(current))515 break;516 cond_resched();517 }518 519 return cleared;520}521 522static int mmap_zero(struct file *file, struct vm_area_struct *vma)523{524#ifndef CONFIG_MMU525 return -ENOSYS;526#endif527 if (vma->vm_flags & VM_SHARED)528 return shmem_zero_setup(vma);529 vma_set_anonymous(vma);530 return 0;531}532 533static unsigned long get_unmapped_area_zero(struct file *file,534 unsigned long addr, unsigned long len,535 unsigned long pgoff, unsigned long flags)536{537#ifdef CONFIG_MMU538 if (flags & MAP_SHARED) {539 /*540 * mmap_zero() will call shmem_zero_setup() to create a file,541 * so use shmem's get_unmapped_area in case it can be huge;542 * and pass NULL for file as in mmap.c's get_unmapped_area(),543 * so as not to confuse shmem with our handle on "/dev/zero".544 */545 return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags);546 }547 548 /* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */549 return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);550#else551 return -ENOSYS;552#endif553}554 555static ssize_t write_full(struct file *file, const char __user *buf,556 size_t count, loff_t *ppos)557{558 return -ENOSPC;559}560 561/*562 * Special lseek() function for /dev/null and /dev/zero. Most notably, you563 * can fopen() both devices with "a" now. This was previously impossible.564 * -- SRB.565 */566static loff_t null_lseek(struct file *file, loff_t offset, int orig)567{568 return file->f_pos = 0;569}570 571/*572 * The memory devices use the full 32/64 bits of the offset, and so we cannot573 * check against negative addresses: they are ok. The return value is weird,574 * though, in that case (0).575 *576 * also note that seeking relative to the "end of file" isn't supported:577 * it has no meaning, so it returns -EINVAL.578 */579static HWJS_SUSPENDS loff_t memory_lseek(struct file *file, loff_t offset, int orig)580{581 loff_t ret;582 583 inode_lock(file_inode(file));584 switch (orig) {585 case SEEK_CUR:586 offset += file->f_pos;587 fallthrough;588 case SEEK_SET:589 /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */590 if ((unsigned long long)offset >= -MAX_ERRNO) {591 ret = -EOVERFLOW;592 break;593 }594 file->f_pos = offset;595 ret = file->f_pos;596 force_successful_syscall_return();597 break;598 default:599 ret = -EINVAL;600 }601 inode_unlock(file_inode(file));602 return ret;603}604 605static int open_port(struct inode *inode, struct file *filp)606{607 int rc;608 609 if (!capable(CAP_SYS_RAWIO))610 return -EPERM;611 612 rc = security_locked_down(LOCKDOWN_DEV_MEM);613 if (rc)614 return rc;615 616 if (iminor(inode) != DEVMEM_MINOR)617 return 0;618 619 /*620 * Use a unified address space to have a single point to manage621 * revocations when drivers want to take over a /dev/mem mapped622 * range.623 */624 filp->f_mapping = iomem_get_mapping();625 626 return 0;627}628 629#define zero_lseek null_lseek630#define full_lseek null_lseek631#define write_zero write_null632#define write_iter_zero write_iter_null633#define splice_write_zero splice_write_null634#define open_mem open_port635 636static const struct file_operations __maybe_unused mem_fops = {637 .llseek = memory_lseek,638 .read = read_mem,639 .write = write_mem,640 .mmap = mmap_mem,641 .open = open_mem,642#ifndef CONFIG_MMU643 .get_unmapped_area = get_unmapped_area_mem,644 .mmap_capabilities = memory_mmap_capabilities,645#endif646 .fop_flags = FOP_UNSIGNED_OFFSET,647};648 649static const struct file_operations null_fops = {650 .llseek = null_lseek,651 .read = read_null,652 .write = write_null,653 .read_iter = read_iter_null,654 .write_iter = write_iter_null,655 .splice_write = splice_write_null,656 .uring_cmd = uring_cmd_null,657};658 659#ifdef CONFIG_DEVPORT660static const struct file_operations port_fops = {661 .llseek = memory_lseek,662 .read = read_port,663 .write = write_port,664 .open = open_port,665};666#endif667 668static const struct file_operations zero_fops = {669 .llseek = zero_lseek,670 .write = write_zero,671 .read_iter = read_iter_zero,672 .read = read_zero,673 .write_iter = write_iter_zero,674 .splice_read = copy_splice_read,675 .splice_write = splice_write_zero,676 .mmap = mmap_zero,677 .get_unmapped_area = get_unmapped_area_zero,678#ifndef CONFIG_MMU679 .mmap_capabilities = zero_mmap_capabilities,680#endif681};682 683static const struct file_operations full_fops = {684 .llseek = full_lseek,685 .read_iter = read_iter_zero,686 .write = write_full,687 .splice_read = copy_splice_read,688};689 690static const struct memdev {691 const char *name;692 const struct file_operations *fops;693 fmode_t fmode;694 umode_t mode;695} devlist[] = {696#ifdef CONFIG_DEVMEM697 [DEVMEM_MINOR] = { "mem", &mem_fops, 0, 0 },698#endif699 [3] = { "null", &null_fops, FMODE_NOWAIT, 0666 },700#ifdef CONFIG_DEVPORT701 [4] = { "port", &port_fops, 0, 0 },702#endif703 [5] = { "zero", &zero_fops, FMODE_NOWAIT, 0666 },704 [7] = { "full", &full_fops, 0, 0666 },705 [8] = { "random", &random_fops, FMODE_NOWAIT, 0666 },706 [9] = { "urandom", &urandom_fops, FMODE_NOWAIT, 0666 },707#ifdef CONFIG_PRINTK708 [11] = { "kmsg", &kmsg_fops, 0, 0644 },709#endif710};711 712static HWJS_SUSPENDS int memory_open(struct inode *inode, struct file *filp)713{714 int minor;715 const struct memdev *dev;716 717 minor = iminor(inode);718 if (minor >= ARRAY_SIZE(devlist))719 return -ENXIO;720 721 dev = &devlist[minor];722 if (!dev->fops)723 return -ENXIO;724 725 filp->f_op = dev->fops;726 filp->f_mode |= dev->fmode;727 728 if (dev->fops->open)729 return dev->fops->open(inode, filp);730 731 return 0;732}733 734static const struct file_operations memory_fops = {735 .open = memory_open,736 .llseek = noop_llseek,737};738 739static char *mem_devnode(const struct device *dev, umode_t *mode)740{741 if (mode && devlist[MINOR(dev->devt)].mode)742 *mode = devlist[MINOR(dev->devt)].mode;743 return NULL;744}745 746static const struct class mem_class = {747 .name = "mem",748 .devnode = mem_devnode,749};750 751static HWJS_SUSPENDS int __init chr_dev_init(void)752{753 int retval;754 int minor;755 756 if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))757 printk("unable to get major %d for memory devs\n", MEM_MAJOR);758 759 retval = class_register(&mem_class);760 if (retval)761 return retval;762 763 for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {764 if (!devlist[minor].name)765 continue;766 767 /*768 * Create /dev/port?769 */770 if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())771 continue;772 773 device_create(&mem_class, NULL, MKDEV(MEM_MAJOR, minor),774 NULL, devlist[minor].name);775 }776 777 return tty_init();778}779 780fs_initcall(chr_dev_init);781