Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/mm/process_vm_access.c
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1 /* 2 * linux/mm/process_vm_access.c 3 * 4 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp. 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #include <linux/mm.h> 13 #include <linux/uio.h> 14 #include <linux/sched.h> 15 #include <linux/highmem.h> 16 #include <linux/ptrace.h> 17 #include <linux/slab.h> 18 #include <linux/syscalls.h> 19 20 #ifdef CONFIG_COMPAT 21 #include <linux/compat.h> 22 #endif 23 24 /** 25 * process_vm_rw_pages - read/write pages from task specified 26 * @task: task to read/write from 27 * @mm: mm for task 28 * @process_pages: struct pages area that can store at least 29 * nr_pages_to_copy struct page pointers 30 * @pa: address of page in task to start copying from/to 31 * @start_offset: offset in page to start copying from/to 32 * @len: number of bytes to copy 33 * @lvec: iovec array specifying where to copy to/from 34 * @lvec_cnt: number of elements in iovec array 35 * @lvec_current: index in iovec array we are up to 36 * @lvec_offset: offset in bytes from current iovec iov_base we are up to 37 * @vm_write: 0 means copy from, 1 means copy to 38 * @nr_pages_to_copy: number of pages to copy 39 * @bytes_copied: returns number of bytes successfully copied 40 * Returns 0 on success, error code otherwise 41 */ 42 static int process_vm_rw_pages(struct task_struct *task, 43 struct mm_struct *mm, 44 struct page **process_pages, 45 unsigned long pa, 46 unsigned long start_offset, 47 unsigned long len, 48 const struct iovec *lvec, 49 unsigned long lvec_cnt, 50 unsigned long *lvec_current, 51 size_t *lvec_offset, 52 int vm_write, 53 unsigned int nr_pages_to_copy, 54 ssize_t *bytes_copied) 55 { 56 int pages_pinned; 57 void *target_kaddr; 58 int pgs_copied = 0; 59 int j; 60 int ret; 61 ssize_t bytes_to_copy; 62 ssize_t rc = 0; 63 64 *bytes_copied = 0; 65 66 /* Get the pages we're interested in */ 67 down_read(&mm->mmap_sem); 68 pages_pinned = get_user_pages(task, mm, pa, 69 nr_pages_to_copy, 70 vm_write, 0, process_pages, NULL); 71 up_read(&mm->mmap_sem); 72 73 if (pages_pinned != nr_pages_to_copy) { 74 rc = -EFAULT; 75 goto end; 76 } 77 78 /* Do the copy for each page */ 79 for (pgs_copied = 0; 80 (pgs_copied < nr_pages_to_copy) && (*lvec_current < lvec_cnt); 81 pgs_copied++) { 82 /* Make sure we have a non zero length iovec */ 83 while (*lvec_current < lvec_cnt 84 && lvec[*lvec_current].iov_len == 0) 85 (*lvec_current)++; 86 if (*lvec_current == lvec_cnt) 87 break; 88 89 /* 90 * Will copy smallest of: 91 * - bytes remaining in page 92 * - bytes remaining in destination iovec 93 */ 94 bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset, 95 len - *bytes_copied); 96 bytes_to_copy = min_t(ssize_t, bytes_to_copy, 97 lvec[*lvec_current].iov_len 98 - *lvec_offset); 99 100 target_kaddr = kmap(process_pages[pgs_copied]) + start_offset; 101 102 if (vm_write) 103 ret = copy_from_user(target_kaddr, 104 lvec[*lvec_current].iov_base 105 + *lvec_offset, 106 bytes_to_copy); 107 else 108 ret = copy_to_user(lvec[*lvec_current].iov_base 109 + *lvec_offset, 110 target_kaddr, bytes_to_copy); 111 kunmap(process_pages[pgs_copied]); 112 if (ret) { 113 *bytes_copied += bytes_to_copy - ret; 114 pgs_copied++; 115 rc = -EFAULT; 116 goto end; 117 } 118 *bytes_copied += bytes_to_copy; 119 *lvec_offset += bytes_to_copy; 120 if (*lvec_offset == lvec[*lvec_current].iov_len) { 121 /* 122 * Need to copy remaining part of page into the 123 * next iovec if there are any bytes left in page 124 */ 125 (*lvec_current)++; 126 *lvec_offset = 0; 127 start_offset = (start_offset + bytes_to_copy) 128 % PAGE_SIZE; 129 if (start_offset) 130 pgs_copied--; 131 } else { 132 start_offset = 0; 133 } 134 } 135 136 end: 137 if (vm_write) { 138 for (j = 0; j < pages_pinned; j++) { 139 if (j < pgs_copied) 140 set_page_dirty_lock(process_pages[j]); 141 put_page(process_pages[j]); 142 } 143 } else { 144 for (j = 0; j < pages_pinned; j++) 145 put_page(process_pages[j]); 146 } 147 148 return rc; 149 } 150 151 /* Maximum number of pages kmalloc'd to hold struct page's during copy */ 152 #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2) 153 154 /** 155 * process_vm_rw_single_vec - read/write pages from task specified 156 * @addr: start memory address of target process 157 * @len: size of area to copy to/from 158 * @lvec: iovec array specifying where to copy to/from locally 159 * @lvec_cnt: number of elements in iovec array 160 * @lvec_current: index in iovec array we are up to 161 * @lvec_offset: offset in bytes from current iovec iov_base we are up to 162 * @process_pages: struct pages area that can store at least 163 * nr_pages_to_copy struct page pointers 164 * @mm: mm for task 165 * @task: task to read/write from 166 * @vm_write: 0 means copy from, 1 means copy to 167 * @bytes_copied: returns number of bytes successfully copied 168 * Returns 0 on success or on failure error code 169 */ 170 static int process_vm_rw_single_vec(unsigned long addr, 171 unsigned long len, 172 const struct iovec *lvec, 173 unsigned long lvec_cnt, 174 unsigned long *lvec_current, 175 size_t *lvec_offset, 176 struct page **process_pages, 177 struct mm_struct *mm, 178 struct task_struct *task, 179 int vm_write, 180 ssize_t *bytes_copied) 181 { 182 unsigned long pa = addr & PAGE_MASK; 183 unsigned long start_offset = addr - pa; 184 unsigned long nr_pages; 185 ssize_t bytes_copied_loop; 186 ssize_t rc = 0; 187 unsigned long nr_pages_copied = 0; 188 unsigned long nr_pages_to_copy; 189 unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES 190 / sizeof(struct pages *); 191 192 *bytes_copied = 0; 193 194 /* Work out address and page range required */ 195 if (len == 0) 196 return 0; 197 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; 198 199 while ((nr_pages_copied < nr_pages) && (*lvec_current < lvec_cnt)) { 200 nr_pages_to_copy = min(nr_pages - nr_pages_copied, 201 max_pages_per_loop); 202 203 rc = process_vm_rw_pages(task, mm, process_pages, pa, 204 start_offset, len, 205 lvec, lvec_cnt, 206 lvec_current, lvec_offset, 207 vm_write, nr_pages_to_copy, 208 &bytes_copied_loop); 209 start_offset = 0; 210 *bytes_copied += bytes_copied_loop; 211 212 if (rc < 0) { 213 return rc; 214 } else { 215 len -= bytes_copied_loop; 216 nr_pages_copied += nr_pages_to_copy; 217 pa += nr_pages_to_copy * PAGE_SIZE; 218 } 219 } 220 221 return rc; 222 } 223 224 /* Maximum number of entries for process pages array 225 which lives on stack */ 226 #define PVM_MAX_PP_ARRAY_COUNT 16 227 228 /** 229 * process_vm_rw_core - core of reading/writing pages from task specified 230 * @pid: PID of process to read/write from/to 231 * @lvec: iovec array specifying where to copy to/from locally 232 * @liovcnt: size of lvec array 233 * @rvec: iovec array specifying where to copy to/from in the other process 234 * @riovcnt: size of rvec array 235 * @flags: currently unused 236 * @vm_write: 0 if reading from other process, 1 if writing to other process 237 * Returns the number of bytes read/written or error code. May 238 * return less bytes than expected if an error occurs during the copying 239 * process. 240 */ 241 static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec, 242 unsigned long liovcnt, 243 const struct iovec *rvec, 244 unsigned long riovcnt, 245 unsigned long flags, int vm_write) 246 { 247 struct task_struct *task; 248 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; 249 struct page **process_pages = pp_stack; 250 struct mm_struct *mm; 251 unsigned long i; 252 ssize_t rc = 0; 253 ssize_t bytes_copied_loop; 254 ssize_t bytes_copied = 0; 255 unsigned long nr_pages = 0; 256 unsigned long nr_pages_iov; 257 unsigned long iov_l_curr_idx = 0; 258 size_t iov_l_curr_offset = 0; 259 ssize_t iov_len; 260 261 /* 262 * Work out how many pages of struct pages we're going to need 263 * when eventually calling get_user_pages 264 */ 265 for (i = 0; i < riovcnt; i++) { 266 iov_len = rvec[i].iov_len; 267 if (iov_len > 0) { 268 nr_pages_iov = ((unsigned long)rvec[i].iov_base 269 + iov_len) 270 / PAGE_SIZE - (unsigned long)rvec[i].iov_base 271 / PAGE_SIZE + 1; 272 nr_pages = max(nr_pages, nr_pages_iov); 273 } 274 } 275 276 if (nr_pages == 0) 277 return 0; 278 279 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { 280 /* For reliability don't try to kmalloc more than 281 2 pages worth */ 282 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, 283 sizeof(struct pages *)*nr_pages), 284 GFP_KERNEL); 285 286 if (!process_pages) 287 return -ENOMEM; 288 } 289 290 /* Get process information */ 291 rcu_read_lock(); 292 task = find_task_by_vpid(pid); 293 if (task) 294 get_task_struct(task); 295 rcu_read_unlock(); 296 if (!task) { 297 rc = -ESRCH; 298 goto free_proc_pages; 299 } 300 301 mm = mm_access(task, PTRACE_MODE_ATTACH); 302 if (!mm || IS_ERR(mm)) { 303 rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; 304 /* 305 * Explicitly map EACCES to EPERM as EPERM is a more a 306 * appropriate error code for process_vw_readv/writev 307 */ 308 if (rc == -EACCES) 309 rc = -EPERM; 310 goto put_task_struct; 311 } 312 313 for (i = 0; i < riovcnt && iov_l_curr_idx < liovcnt; i++) { 314 rc = process_vm_rw_single_vec( 315 (unsigned long)rvec[i].iov_base, rvec[i].iov_len, 316 lvec, liovcnt, &iov_l_curr_idx, &iov_l_curr_offset, 317 process_pages, mm, task, vm_write, &bytes_copied_loop); 318 bytes_copied += bytes_copied_loop; 319 if (rc != 0) { 320 /* If we have managed to copy any data at all then 321 we return the number of bytes copied. Otherwise 322 we return the error code */ 323 if (bytes_copied) 324 rc = bytes_copied; 325 goto put_mm; 326 } 327 } 328 329 rc = bytes_copied; 330 put_mm: 331 mmput(mm); 332 333 put_task_struct: 334 put_task_struct(task); 335 336 free_proc_pages: 337 if (process_pages != pp_stack) 338 kfree(process_pages); 339 return rc; 340 } 341 342 /** 343 * process_vm_rw - check iovecs before calling core routine 344 * @pid: PID of process to read/write from/to 345 * @lvec: iovec array specifying where to copy to/from locally 346 * @liovcnt: size of lvec array 347 * @rvec: iovec array specifying where to copy to/from in the other process 348 * @riovcnt: size of rvec array 349 * @flags: currently unused 350 * @vm_write: 0 if reading from other process, 1 if writing to other process 351 * Returns the number of bytes read/written or error code. May 352 * return less bytes than expected if an error occurs during the copying 353 * process. 354 */ 355 static ssize_t process_vm_rw(pid_t pid, 356 const struct iovec __user *lvec, 357 unsigned long liovcnt, 358 const struct iovec __user *rvec, 359 unsigned long riovcnt, 360 unsigned long flags, int vm_write) 361 { 362 struct iovec iovstack_l[UIO_FASTIOV]; 363 struct iovec iovstack_r[UIO_FASTIOV]; 364 struct iovec *iov_l = iovstack_l; 365 struct iovec *iov_r = iovstack_r; 366 ssize_t rc; 367 368 if (flags != 0) 369 return -EINVAL; 370 371 /* Check iovecs */ 372 if (vm_write) 373 rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV, 374 iovstack_l, &iov_l); 375 else 376 rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV, 377 iovstack_l, &iov_l); 378 if (rc <= 0) 379 goto free_iovecs; 380 381 rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV, 382 iovstack_r, &iov_r); 383 if (rc <= 0) 384 goto free_iovecs; 385 386 rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags, 387 vm_write); 388 389 free_iovecs: 390 if (iov_r != iovstack_r) 391 kfree(iov_r); 392 if (iov_l != iovstack_l) 393 kfree(iov_l); 394 395 return rc; 396 } 397 398 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec, 399 unsigned long, liovcnt, const struct iovec __user *, rvec, 400 unsigned long, riovcnt, unsigned long, flags) 401 { 402 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0); 403 } 404 405 SYSCALL_DEFINE6(process_vm_writev, pid_t, pid, 406 const struct iovec __user *, lvec, 407 unsigned long, liovcnt, const struct iovec __user *, rvec, 408 unsigned long, riovcnt, unsigned long, flags) 409 { 410 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1); 411 } 412 413 #ifdef CONFIG_COMPAT 414 415 asmlinkage ssize_t 416 compat_process_vm_rw(compat_pid_t pid, 417 const struct compat_iovec __user *lvec, 418 unsigned long liovcnt, 419 const struct compat_iovec __user *rvec, 420 unsigned long riovcnt, 421 unsigned long flags, int vm_write) 422 { 423 struct iovec iovstack_l[UIO_FASTIOV]; 424 struct iovec iovstack_r[UIO_FASTIOV]; 425 struct iovec *iov_l = iovstack_l; 426 struct iovec *iov_r = iovstack_r; 427 ssize_t rc = -EFAULT; 428 429 if (flags != 0) 430 return -EINVAL; 431 432 if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec))) 433 goto out; 434 435 if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec))) 436 goto out; 437 438 if (vm_write) 439 rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt, 440 UIO_FASTIOV, iovstack_l, 441 &iov_l); 442 else 443 rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt, 444 UIO_FASTIOV, iovstack_l, 445 &iov_l); 446 if (rc <= 0) 447 goto free_iovecs; 448 rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, 449 UIO_FASTIOV, iovstack_r, 450 &iov_r); 451 if (rc <= 0) 452 goto free_iovecs; 453 454 rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags, 455 vm_write); 456 457 free_iovecs: 458 if (iov_r != iovstack_r) 459 kfree(iov_r); 460 if (iov_l != iovstack_l) 461 kfree(iov_l); 462 463 out: 464 return rc; 465 } 466 467 asmlinkage ssize_t 468 compat_sys_process_vm_readv(compat_pid_t pid, 469 const struct compat_iovec __user *lvec, 470 unsigned long liovcnt, 471 const struct compat_iovec __user *rvec, 472 unsigned long riovcnt, 473 unsigned long flags) 474 { 475 return compat_process_vm_rw(pid, lvec, liovcnt, rvec, 476 riovcnt, flags, 0); 477 } 478 479 asmlinkage ssize_t 480 compat_sys_process_vm_writev(compat_pid_t pid, 481 const struct compat_iovec __user *lvec, 482 unsigned long liovcnt, 483 const struct compat_iovec __user *rvec, 484 unsigned long riovcnt, 485 unsigned long flags) 486 { 487 return compat_process_vm_rw(pid, lvec, liovcnt, rvec, 488 riovcnt, flags, 1); 489 } 490 491 #endif
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