mem.c revision a11edb59a05d8d5195419bd1fc28d82752324158
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/bootmem.h> 26#include <linux/splice.h> 27#include <linux/pfn.h> 28#include <linux/export.h> 29#include <linux/io.h> 30#include <linux/aio.h> 31 32#include <asm/uaccess.h> 33 34#ifdef CONFIG_IA64 35# include <linux/efi.h> 36#endif 37 38#define DEVPORT_MINOR 4 39 40static inline unsigned long size_inside_page(unsigned long start, 41 unsigned long size) 42{ 43 unsigned long sz; 44 45 sz = PAGE_SIZE - (start & (PAGE_SIZE - 1)); 46 47 return min(sz, size); 48} 49 50#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE 51static inline int valid_phys_addr_range(phys_addr_t addr, size_t count) 52{ 53 return addr + count <= __pa(high_memory); 54} 55 56static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) 57{ 58 return 1; 59} 60#endif 61 62#ifdef CONFIG_STRICT_DEVMEM 63static inline int range_is_allowed(unsigned long pfn, unsigned long size) 64{ 65 u64 from = ((u64)pfn) << PAGE_SHIFT; 66 u64 to = from + size; 67 u64 cursor = from; 68 69 while (cursor < to) { 70 if (!devmem_is_allowed(pfn)) { 71 printk(KERN_INFO 72 "Program %s tried to access /dev/mem between %Lx->%Lx.\n", 73 current->comm, from, to); 74 return 0; 75 } 76 cursor += PAGE_SIZE; 77 pfn++; 78 } 79 return 1; 80} 81#else 82static inline int range_is_allowed(unsigned long pfn, unsigned long size) 83{ 84 return 1; 85} 86#endif 87 88void __weak unxlate_dev_mem_ptr(unsigned long phys, void *addr) 89{ 90} 91 92/* 93 * This funcion reads the *physical* memory. The f_pos points directly to the 94 * memory location. 95 */ 96static ssize_t read_mem(struct file *file, char __user *buf, 97 size_t count, loff_t *ppos) 98{ 99 phys_addr_t p = *ppos; 100 ssize_t read, sz; 101 char *ptr; 102 103 if (!valid_phys_addr_range(p, count)) 104 return -EFAULT; 105 read = 0; 106#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED 107 /* we don't have page 0 mapped on sparc and m68k.. */ 108 if (p < PAGE_SIZE) { 109 sz = size_inside_page(p, count); 110 if (sz > 0) { 111 if (clear_user(buf, sz)) 112 return -EFAULT; 113 buf += sz; 114 p += sz; 115 count -= sz; 116 read += sz; 117 } 118 } 119#endif 120 121 while (count > 0) { 122 unsigned long remaining; 123 124 sz = size_inside_page(p, count); 125 126 if (!range_is_allowed(p >> PAGE_SHIFT, count)) 127 return -EPERM; 128 129 /* 130 * On ia64 if a page has been mapped somewhere as uncached, then 131 * it must also be accessed uncached by the kernel or data 132 * corruption may occur. 133 */ 134 ptr = xlate_dev_mem_ptr(p); 135 if (!ptr) 136 return -EFAULT; 137 138 remaining = copy_to_user(buf, ptr, sz); 139 unxlate_dev_mem_ptr(p, ptr); 140 if (remaining) 141 return -EFAULT; 142 143 buf += sz; 144 p += sz; 145 count -= sz; 146 read += sz; 147 } 148 149 *ppos += read; 150 return read; 151} 152 153static ssize_t write_mem(struct file *file, const char __user *buf, 154 size_t count, loff_t *ppos) 155{ 156 phys_addr_t p = *ppos; 157 ssize_t written, sz; 158 unsigned long copied; 159 void *ptr; 160 161 if (!valid_phys_addr_range(p, count)) 162 return -EFAULT; 163 164 written = 0; 165 166#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED 167 /* we don't have page 0 mapped on sparc and m68k.. */ 168 if (p < PAGE_SIZE) { 169 sz = size_inside_page(p, count); 170 /* Hmm. Do something? */ 171 buf += sz; 172 p += sz; 173 count -= sz; 174 written += sz; 175 } 176#endif 177 178 while (count > 0) { 179 sz = size_inside_page(p, count); 180 181 if (!range_is_allowed(p >> PAGE_SHIFT, sz)) 182 return -EPERM; 183 184 /* 185 * On ia64 if a page has been mapped somewhere as uncached, then 186 * it must also be accessed uncached by the kernel or data 187 * corruption may occur. 188 */ 189 ptr = xlate_dev_mem_ptr(p); 190 if (!ptr) { 191 if (written) 192 break; 193 return -EFAULT; 194 } 195 196 copied = copy_from_user(ptr, buf, sz); 197 unxlate_dev_mem_ptr(p, ptr); 198 if (copied) { 199 written += sz - copied; 200 if (written) 201 break; 202 return -EFAULT; 203 } 204 205 buf += sz; 206 p += sz; 207 count -= sz; 208 written += sz; 209 } 210 211 *ppos += written; 212 return written; 213} 214 215int __weak phys_mem_access_prot_allowed(struct file *file, 216 unsigned long pfn, unsigned long size, pgprot_t *vma_prot) 217{ 218 return 1; 219} 220 221#ifndef __HAVE_PHYS_MEM_ACCESS_PROT 222 223/* 224 * Architectures vary in how they handle caching for addresses 225 * outside of main memory. 226 * 227 */ 228#ifdef pgprot_noncached 229static int uncached_access(struct file *file, phys_addr_t addr) 230{ 231#if defined(CONFIG_IA64) 232 /* 233 * On ia64, we ignore O_DSYNC because we cannot tolerate memory 234 * attribute aliases. 235 */ 236 return !(efi_mem_attributes(addr) & EFI_MEMORY_WB); 237#elif defined(CONFIG_MIPS) 238 { 239 extern int __uncached_access(struct file *file, 240 unsigned long addr); 241 242 return __uncached_access(file, addr); 243 } 244#else 245 /* 246 * Accessing memory above the top the kernel knows about or through a 247 * file pointer 248 * that was marked O_DSYNC will be done non-cached. 249 */ 250 if (file->f_flags & O_DSYNC) 251 return 1; 252 return addr >= __pa(high_memory); 253#endif 254} 255#endif 256 257static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, 258 unsigned long size, pgprot_t vma_prot) 259{ 260#ifdef pgprot_noncached 261 phys_addr_t offset = pfn << PAGE_SHIFT; 262 263 if (uncached_access(file, offset)) 264 return pgprot_noncached(vma_prot); 265#endif 266 return vma_prot; 267} 268#endif 269 270#ifndef CONFIG_MMU 271static unsigned long get_unmapped_area_mem(struct file *file, 272 unsigned long addr, 273 unsigned long len, 274 unsigned long pgoff, 275 unsigned long flags) 276{ 277 if (!valid_mmap_phys_addr_range(pgoff, len)) 278 return (unsigned long) -EINVAL; 279 return pgoff << PAGE_SHIFT; 280} 281 282/* can't do an in-place private mapping if there's no MMU */ 283static inline int private_mapping_ok(struct vm_area_struct *vma) 284{ 285 return vma->vm_flags & VM_MAYSHARE; 286} 287#else 288#define get_unmapped_area_mem NULL 289 290static inline int private_mapping_ok(struct vm_area_struct *vma) 291{ 292 return 1; 293} 294#endif 295 296static const struct vm_operations_struct mmap_mem_ops = { 297#ifdef CONFIG_HAVE_IOREMAP_PROT 298 .access = generic_access_phys 299#endif 300}; 301 302static int mmap_mem(struct file *file, struct vm_area_struct *vma) 303{ 304 size_t size = vma->vm_end - vma->vm_start; 305 306 if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size)) 307 return -EINVAL; 308 309 if (!private_mapping_ok(vma)) 310 return -ENOSYS; 311 312 if (!range_is_allowed(vma->vm_pgoff, size)) 313 return -EPERM; 314 315 if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size, 316 &vma->vm_page_prot)) 317 return -EINVAL; 318 319 vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff, 320 size, 321 vma->vm_page_prot); 322 323 vma->vm_ops = &mmap_mem_ops; 324 325 /* Remap-pfn-range will mark the range VM_IO */ 326 if (remap_pfn_range(vma, 327 vma->vm_start, 328 vma->vm_pgoff, 329 size, 330 vma->vm_page_prot)) { 331 return -EAGAIN; 332 } 333 return 0; 334} 335 336#ifdef CONFIG_DEVKMEM 337static int mmap_kmem(struct file *file, struct vm_area_struct *vma) 338{ 339 unsigned long pfn; 340 341 /* Turn a kernel-virtual address into a physical page frame */ 342 pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT; 343 344 /* 345 * RED-PEN: on some architectures there is more mapped memory than 346 * available in mem_map which pfn_valid checks for. Perhaps should add a 347 * new macro here. 348 * 349 * RED-PEN: vmalloc is not supported right now. 350 */ 351 if (!pfn_valid(pfn)) 352 return -EIO; 353 354 vma->vm_pgoff = pfn; 355 return mmap_mem(file, vma); 356} 357#endif 358 359#ifdef CONFIG_DEVKMEM 360/* 361 * This function reads the *virtual* memory as seen by the kernel. 362 */ 363static ssize_t read_kmem(struct file *file, char __user *buf, 364 size_t count, loff_t *ppos) 365{ 366 unsigned long p = *ppos; 367 ssize_t low_count, read, sz; 368 char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */ 369 int err = 0; 370 371 read = 0; 372 if (p < (unsigned long) high_memory) { 373 low_count = count; 374 if (count > (unsigned long)high_memory - p) 375 low_count = (unsigned long)high_memory - p; 376 377#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED 378 /* we don't have page 0 mapped on sparc and m68k.. */ 379 if (p < PAGE_SIZE && low_count > 0) { 380 sz = size_inside_page(p, low_count); 381 if (clear_user(buf, sz)) 382 return -EFAULT; 383 buf += sz; 384 p += sz; 385 read += sz; 386 low_count -= sz; 387 count -= sz; 388 } 389#endif 390 while (low_count > 0) { 391 sz = size_inside_page(p, low_count); 392 393 /* 394 * On ia64 if a page has been mapped somewhere as 395 * uncached, then it must also be accessed uncached 396 * by the kernel or data corruption may occur 397 */ 398 kbuf = xlate_dev_kmem_ptr((char *)p); 399 400 if (copy_to_user(buf, kbuf, sz)) 401 return -EFAULT; 402 buf += sz; 403 p += sz; 404 read += sz; 405 low_count -= sz; 406 count -= sz; 407 } 408 } 409 410 if (count > 0) { 411 kbuf = (char *)__get_free_page(GFP_KERNEL); 412 if (!kbuf) 413 return -ENOMEM; 414 while (count > 0) { 415 sz = size_inside_page(p, count); 416 if (!is_vmalloc_or_module_addr((void *)p)) { 417 err = -ENXIO; 418 break; 419 } 420 sz = vread(kbuf, (char *)p, sz); 421 if (!sz) 422 break; 423 if (copy_to_user(buf, kbuf, sz)) { 424 err = -EFAULT; 425 break; 426 } 427 count -= sz; 428 buf += sz; 429 read += sz; 430 p += sz; 431 } 432 free_page((unsigned long)kbuf); 433 } 434 *ppos = p; 435 return read ? read : err; 436} 437 438 439static ssize_t do_write_kmem(unsigned long p, const char __user *buf, 440 size_t count, loff_t *ppos) 441{ 442 ssize_t written, sz; 443 unsigned long copied; 444 445 written = 0; 446#ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED 447 /* we don't have page 0 mapped on sparc and m68k.. */ 448 if (p < PAGE_SIZE) { 449 sz = size_inside_page(p, count); 450 /* Hmm. Do something? */ 451 buf += sz; 452 p += sz; 453 count -= sz; 454 written += sz; 455 } 456#endif 457 458 while (count > 0) { 459 char *ptr; 460 461 sz = size_inside_page(p, count); 462 463 /* 464 * On ia64 if a page has been mapped somewhere as uncached, then 465 * it must also be accessed uncached by the kernel or data 466 * corruption may occur. 467 */ 468 ptr = xlate_dev_kmem_ptr((char *)p); 469 470 copied = copy_from_user(ptr, buf, sz); 471 if (copied) { 472 written += sz - copied; 473 if (written) 474 break; 475 return -EFAULT; 476 } 477 buf += sz; 478 p += sz; 479 count -= sz; 480 written += sz; 481 } 482 483 *ppos += written; 484 return written; 485} 486 487/* 488 * This function writes to the *virtual* memory as seen by the kernel. 489 */ 490static ssize_t write_kmem(struct file *file, const char __user *buf, 491 size_t count, loff_t *ppos) 492{ 493 unsigned long p = *ppos; 494 ssize_t wrote = 0; 495 ssize_t virtr = 0; 496 char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */ 497 int err = 0; 498 499 if (p < (unsigned long) high_memory) { 500 unsigned long to_write = min_t(unsigned long, count, 501 (unsigned long)high_memory - p); 502 wrote = do_write_kmem(p, buf, to_write, ppos); 503 if (wrote != to_write) 504 return wrote; 505 p += wrote; 506 buf += wrote; 507 count -= wrote; 508 } 509 510 if (count > 0) { 511 kbuf = (char *)__get_free_page(GFP_KERNEL); 512 if (!kbuf) 513 return wrote ? wrote : -ENOMEM; 514 while (count > 0) { 515 unsigned long sz = size_inside_page(p, count); 516 unsigned long n; 517 518 if (!is_vmalloc_or_module_addr((void *)p)) { 519 err = -ENXIO; 520 break; 521 } 522 n = copy_from_user(kbuf, buf, sz); 523 if (n) { 524 err = -EFAULT; 525 break; 526 } 527 vwrite(kbuf, (char *)p, sz); 528 count -= sz; 529 buf += sz; 530 virtr += sz; 531 p += sz; 532 } 533 free_page((unsigned long)kbuf); 534 } 535 536 *ppos = p; 537 return virtr + wrote ? : err; 538} 539#endif 540 541#ifdef CONFIG_DEVPORT 542static ssize_t read_port(struct file *file, char __user *buf, 543 size_t count, loff_t *ppos) 544{ 545 unsigned long i = *ppos; 546 char __user *tmp = buf; 547 548 if (!access_ok(VERIFY_WRITE, buf, count)) 549 return -EFAULT; 550 while (count-- > 0 && i < 65536) { 551 if (__put_user(inb(i), tmp) < 0) 552 return -EFAULT; 553 i++; 554 tmp++; 555 } 556 *ppos = i; 557 return tmp-buf; 558} 559 560static ssize_t write_port(struct file *file, const char __user *buf, 561 size_t count, loff_t *ppos) 562{ 563 unsigned long i = *ppos; 564 const char __user *tmp = buf; 565 566 if (!access_ok(VERIFY_READ, buf, count)) 567 return -EFAULT; 568 while (count-- > 0 && i < 65536) { 569 char c; 570 if (__get_user(c, tmp)) { 571 if (tmp > buf) 572 break; 573 return -EFAULT; 574 } 575 outb(c, i); 576 i++; 577 tmp++; 578 } 579 *ppos = i; 580 return tmp-buf; 581} 582#endif 583 584static ssize_t read_null(struct file *file, char __user *buf, 585 size_t count, loff_t *ppos) 586{ 587 return 0; 588} 589 590static ssize_t write_null(struct file *file, const char __user *buf, 591 size_t count, loff_t *ppos) 592{ 593 return count; 594} 595 596static ssize_t aio_read_null(struct kiocb *iocb, const struct iovec *iov, 597 unsigned long nr_segs, loff_t pos) 598{ 599 return 0; 600} 601 602static ssize_t aio_write_null(struct kiocb *iocb, const struct iovec *iov, 603 unsigned long nr_segs, loff_t pos) 604{ 605 return iov_length(iov, nr_segs); 606} 607 608static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf, 609 struct splice_desc *sd) 610{ 611 return sd->len; 612} 613 614static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out, 615 loff_t *ppos, size_t len, unsigned int flags) 616{ 617 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null); 618} 619 620static ssize_t read_zero(struct file *file, char __user *buf, 621 size_t count, loff_t *ppos) 622{ 623 size_t written; 624 625 if (!count) 626 return 0; 627 628 if (!access_ok(VERIFY_WRITE, buf, count)) 629 return -EFAULT; 630 631 written = 0; 632 while (count) { 633 unsigned long unwritten; 634 size_t chunk = count; 635 636 if (chunk > PAGE_SIZE) 637 chunk = PAGE_SIZE; /* Just for latency reasons */ 638 unwritten = __clear_user(buf, chunk); 639 written += chunk - unwritten; 640 if (unwritten) 641 break; 642 if (signal_pending(current)) 643 return written ? written : -ERESTARTSYS; 644 buf += chunk; 645 count -= chunk; 646 cond_resched(); 647 } 648 return written ? written : -EFAULT; 649} 650 651static ssize_t aio_read_zero(struct kiocb *iocb, const struct iovec *iov, 652 unsigned long nr_segs, loff_t pos) 653{ 654 size_t written = 0; 655 unsigned long i; 656 ssize_t ret; 657 658 for (i = 0; i < nr_segs; i++) { 659 ret = read_zero(iocb->ki_filp, iov[i].iov_base, iov[i].iov_len, 660 &pos); 661 if (ret < 0) 662 break; 663 written += ret; 664 } 665 666 return written ? written : -EFAULT; 667} 668 669static int mmap_zero(struct file *file, struct vm_area_struct *vma) 670{ 671#ifndef CONFIG_MMU 672 return -ENOSYS; 673#endif 674 if (vma->vm_flags & VM_SHARED) 675 return shmem_zero_setup(vma); 676 return 0; 677} 678 679static ssize_t write_full(struct file *file, const char __user *buf, 680 size_t count, loff_t *ppos) 681{ 682 return -ENOSPC; 683} 684 685/* 686 * Special lseek() function for /dev/null and /dev/zero. Most notably, you 687 * can fopen() both devices with "a" now. This was previously impossible. 688 * -- SRB. 689 */ 690static loff_t null_lseek(struct file *file, loff_t offset, int orig) 691{ 692 return file->f_pos = 0; 693} 694 695/* 696 * The memory devices use the full 32/64 bits of the offset, and so we cannot 697 * check against negative addresses: they are ok. The return value is weird, 698 * though, in that case (0). 699 * 700 * also note that seeking relative to the "end of file" isn't supported: 701 * it has no meaning, so it returns -EINVAL. 702 */ 703static loff_t memory_lseek(struct file *file, loff_t offset, int orig) 704{ 705 loff_t ret; 706 707 mutex_lock(&file_inode(file)->i_mutex); 708 switch (orig) { 709 case SEEK_CUR: 710 offset += file->f_pos; 711 case SEEK_SET: 712 /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */ 713 if (IS_ERR_VALUE((unsigned long long)offset)) { 714 ret = -EOVERFLOW; 715 break; 716 } 717 file->f_pos = offset; 718 ret = file->f_pos; 719 force_successful_syscall_return(); 720 break; 721 default: 722 ret = -EINVAL; 723 } 724 mutex_unlock(&file_inode(file)->i_mutex); 725 return ret; 726} 727 728static int open_port(struct inode *inode, struct file *filp) 729{ 730 return capable(CAP_SYS_RAWIO) ? 0 : -EPERM; 731} 732 733#define zero_lseek null_lseek 734#define full_lseek null_lseek 735#define write_zero write_null 736#define read_full read_zero 737#define aio_write_zero aio_write_null 738#define open_mem open_port 739#define open_kmem open_mem 740 741static const struct file_operations mem_fops = { 742 .llseek = memory_lseek, 743 .read = read_mem, 744 .write = write_mem, 745 .mmap = mmap_mem, 746 .open = open_mem, 747 .get_unmapped_area = get_unmapped_area_mem, 748}; 749 750#ifdef CONFIG_DEVKMEM 751static const struct file_operations kmem_fops = { 752 .llseek = memory_lseek, 753 .read = read_kmem, 754 .write = write_kmem, 755 .mmap = mmap_kmem, 756 .open = open_kmem, 757 .get_unmapped_area = get_unmapped_area_mem, 758}; 759#endif 760 761static const struct file_operations null_fops = { 762 .llseek = null_lseek, 763 .read = read_null, 764 .write = write_null, 765 .aio_read = aio_read_null, 766 .aio_write = aio_write_null, 767 .splice_write = splice_write_null, 768}; 769 770#ifdef CONFIG_DEVPORT 771static const struct file_operations port_fops = { 772 .llseek = memory_lseek, 773 .read = read_port, 774 .write = write_port, 775 .open = open_port, 776}; 777#endif 778 779static const struct file_operations zero_fops = { 780 .llseek = zero_lseek, 781 .read = read_zero, 782 .write = write_zero, 783 .aio_read = aio_read_zero, 784 .aio_write = aio_write_zero, 785 .mmap = mmap_zero, 786}; 787 788/* 789 * capabilities for /dev/zero 790 * - permits private mappings, "copies" are taken of the source of zeros 791 * - no writeback happens 792 */ 793static struct backing_dev_info zero_bdi = { 794 .name = "char/mem", 795 .capabilities = BDI_CAP_MAP_COPY | BDI_CAP_NO_ACCT_AND_WRITEBACK, 796}; 797 798static const struct file_operations full_fops = { 799 .llseek = full_lseek, 800 .read = read_full, 801 .write = write_full, 802}; 803 804static const struct memdev { 805 const char *name; 806 umode_t mode; 807 const struct file_operations *fops; 808 struct backing_dev_info *dev_info; 809} devlist[] = { 810 [1] = { "mem", 0, &mem_fops, &directly_mappable_cdev_bdi }, 811#ifdef CONFIG_DEVKMEM 812 [2] = { "kmem", 0, &kmem_fops, &directly_mappable_cdev_bdi }, 813#endif 814 [3] = { "null", 0666, &null_fops, NULL }, 815#ifdef CONFIG_DEVPORT 816 [4] = { "port", 0, &port_fops, NULL }, 817#endif 818 [5] = { "zero", 0666, &zero_fops, &zero_bdi }, 819 [7] = { "full", 0666, &full_fops, NULL }, 820 [8] = { "random", 0666, &random_fops, NULL }, 821 [9] = { "urandom", 0666, &urandom_fops, NULL }, 822#ifdef CONFIG_PRINTK 823 [11] = { "kmsg", 0644, &kmsg_fops, NULL }, 824#endif 825}; 826 827static int memory_open(struct inode *inode, struct file *filp) 828{ 829 int minor; 830 const struct memdev *dev; 831 832 minor = iminor(inode); 833 if (minor >= ARRAY_SIZE(devlist)) 834 return -ENXIO; 835 836 dev = &devlist[minor]; 837 if (!dev->fops) 838 return -ENXIO; 839 840 filp->f_op = dev->fops; 841 if (dev->dev_info) 842 filp->f_mapping->backing_dev_info = dev->dev_info; 843 844 /* Is /dev/mem or /dev/kmem ? */ 845 if (dev->dev_info == &directly_mappable_cdev_bdi) 846 filp->f_mode |= FMODE_UNSIGNED_OFFSET; 847 848 if (dev->fops->open) 849 return dev->fops->open(inode, filp); 850 851 return 0; 852} 853 854static const struct file_operations memory_fops = { 855 .open = memory_open, 856 .llseek = noop_llseek, 857}; 858 859static char *mem_devnode(struct device *dev, umode_t *mode) 860{ 861 if (mode && devlist[MINOR(dev->devt)].mode) 862 *mode = devlist[MINOR(dev->devt)].mode; 863 return NULL; 864} 865 866static struct class *mem_class; 867 868static int __init chr_dev_init(void) 869{ 870 int minor; 871 int err; 872 873 err = bdi_init(&zero_bdi); 874 if (err) 875 return err; 876 877 if (register_chrdev(MEM_MAJOR, "mem", &memory_fops)) 878 printk("unable to get major %d for memory devs\n", MEM_MAJOR); 879 880 mem_class = class_create(THIS_MODULE, "mem"); 881 if (IS_ERR(mem_class)) 882 return PTR_ERR(mem_class); 883 884 mem_class->devnode = mem_devnode; 885 for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) { 886 if (!devlist[minor].name) 887 continue; 888 889 /* 890 * Create /dev/port? 891 */ 892 if ((minor == DEVPORT_MINOR) && !arch_has_dev_port()) 893 continue; 894 895 device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor), 896 NULL, devlist[minor].name); 897 } 898 899 return tty_init(); 900} 901 902fs_initcall(chr_dev_init); 903