2 * linux/mm/process_vm_access.c
4 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
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.
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>
21 #include <linux/compat.h>
25 * process_vm_rw_pages - read/write pages from task specified
26 * @task: task to read/write from
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
42 static int process_vm_rw_pages(struct task_struct *task,
44 struct page **process_pages,
46 unsigned long start_offset,
48 const struct iovec *lvec,
49 unsigned long lvec_cnt,
50 unsigned long *lvec_current,
53 unsigned int nr_pages_to_copy,
54 ssize_t *bytes_copied)
61 ssize_t bytes_to_copy;
66 /* Get the pages we're interested in */
67 down_read(&mm->mmap_sem);
68 pages_pinned = get_user_pages(task, mm, pa,
70 vm_write, 0, process_pages, NULL);
71 up_read(&mm->mmap_sem);
73 if (pages_pinned != nr_pages_to_copy) {
78 /* Do the copy for each page */
80 (pgs_copied < nr_pages_to_copy) && (*lvec_current < lvec_cnt);
82 /* Make sure we have a non zero length iovec */
83 while (*lvec_current < lvec_cnt
84 && lvec[*lvec_current].iov_len == 0)
86 if (*lvec_current == lvec_cnt)
90 * Will copy smallest of:
91 * - bytes remaining in page
92 * - bytes remaining in destination iovec
94 bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset,
96 bytes_to_copy = min_t(ssize_t, bytes_to_copy,
97 lvec[*lvec_current].iov_len
100 target_kaddr = kmap(process_pages[pgs_copied]) + start_offset;
103 ret = copy_from_user(target_kaddr,
104 lvec[*lvec_current].iov_base
108 ret = copy_to_user(lvec[*lvec_current].iov_base
110 target_kaddr, bytes_to_copy);
111 kunmap(process_pages[pgs_copied]);
113 *bytes_copied += bytes_to_copy - ret;
118 *bytes_copied += bytes_to_copy;
119 *lvec_offset += bytes_to_copy;
120 if (*lvec_offset == lvec[*lvec_current].iov_len) {
122 * Need to copy remaining part of page into the
123 * next iovec if there are any bytes left in page
127 start_offset = (start_offset + bytes_to_copy)
138 for (j = 0; j < pages_pinned; j++) {
140 set_page_dirty_lock(process_pages[j]);
141 put_page(process_pages[j]);
144 for (j = 0; j < pages_pinned; j++)
145 put_page(process_pages[j]);
151 /* Maximum number of pages kmalloc'd to hold struct page's during copy */
152 #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
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
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
170 static int process_vm_rw_single_vec(unsigned long addr,
172 const struct iovec *lvec,
173 unsigned long lvec_cnt,
174 unsigned long *lvec_current,
176 struct page **process_pages,
177 struct mm_struct *mm,
178 struct task_struct *task,
180 ssize_t *bytes_copied)
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;
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 *);
194 /* Work out address and page range required */
197 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
199 while ((nr_pages_copied < nr_pages) && (*lvec_current < lvec_cnt)) {
200 nr_pages_to_copy = min(nr_pages - nr_pages_copied,
203 rc = process_vm_rw_pages(task, mm, process_pages, pa,
206 lvec_current, lvec_offset,
207 vm_write, nr_pages_to_copy,
210 *bytes_copied += bytes_copied_loop;
215 len -= bytes_copied_loop;
216 nr_pages_copied += nr_pages_to_copy;
217 pa += nr_pages_to_copy * PAGE_SIZE;
225 * process_vm_rw_core - core of reading/writing pages from task specified
226 * @pid: PID of process to read/write from/to
227 * @lvec: iovec array specifying where to copy to/from locally
228 * @liovcnt: size of lvec array
229 * @rvec: iovec array specifying where to copy to/from in the other process
230 * @riovcnt: size of rvec array
231 * @flags: currently unused
232 * @vm_write: 0 if reading from other process, 1 if writing to other process
233 * Returns the number of bytes read/written or error code. May
234 * return less bytes than expected if an error occurs during the copying
237 static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
238 unsigned long liovcnt,
239 const struct iovec *rvec,
240 unsigned long riovcnt,
241 unsigned long flags, int vm_write)
243 struct task_struct *task;
244 struct page **process_pages = NULL;
245 struct mm_struct *mm;
248 ssize_t bytes_copied_loop;
249 ssize_t bytes_copied = 0;
250 unsigned long nr_pages = 0;
251 unsigned long nr_pages_iov;
252 unsigned long iov_l_curr_idx = 0;
253 size_t iov_l_curr_offset = 0;
257 * Work out how many pages of struct pages we're going to need
258 * when eventually calling get_user_pages
260 for (i = 0; i < riovcnt; i++) {
261 iov_len = rvec[i].iov_len;
263 nr_pages_iov = ((unsigned long)rvec[i].iov_base
265 / PAGE_SIZE - (unsigned long)rvec[i].iov_base
267 nr_pages = max(nr_pages, nr_pages_iov);
274 /* For reliability don't try to kmalloc more than 2 pages worth */
275 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
276 sizeof(struct pages *)*nr_pages),
282 /* Get process information */
284 task = find_task_by_vpid(pid);
286 get_task_struct(task);
290 goto free_proc_pages;
294 if (__ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
297 goto put_task_struct;
301 if (!mm || (task->flags & PF_KTHREAD)) {
304 goto put_task_struct;
307 atomic_inc(&mm->mm_users);
310 for (i = 0; i < riovcnt && iov_l_curr_idx < liovcnt; i++) {
311 rc = process_vm_rw_single_vec(
312 (unsigned long)rvec[i].iov_base, rvec[i].iov_len,
313 lvec, liovcnt, &iov_l_curr_idx, &iov_l_curr_offset,
314 process_pages, mm, task, vm_write, &bytes_copied_loop);
315 bytes_copied += bytes_copied_loop;
317 /* If we have managed to copy any data at all then
318 we return the number of bytes copied. Otherwise
319 we return the error code */
331 put_task_struct(task);
334 kfree(process_pages);
339 * process_vm_rw - check iovecs before calling core routine
340 * @pid: PID of process to read/write from/to
341 * @lvec: iovec array specifying where to copy to/from locally
342 * @liovcnt: size of lvec array
343 * @rvec: iovec array specifying where to copy to/from in the other process
344 * @riovcnt: size of rvec array
345 * @flags: currently unused
346 * @vm_write: 0 if reading from other process, 1 if writing to other process
347 * Returns the number of bytes read/written or error code. May
348 * return less bytes than expected if an error occurs during the copying
351 static ssize_t process_vm_rw(pid_t pid,
352 const struct iovec __user *lvec,
353 unsigned long liovcnt,
354 const struct iovec __user *rvec,
355 unsigned long riovcnt,
356 unsigned long flags, int vm_write)
358 struct iovec iovstack_l[UIO_FASTIOV];
359 struct iovec iovstack_r[UIO_FASTIOV];
360 struct iovec *iov_l = iovstack_l;
361 struct iovec *iov_r = iovstack_r;
369 rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
370 iovstack_l, &iov_l, 1);
372 rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
373 iovstack_l, &iov_l, 1);
377 rc = rw_copy_check_uvector(READ, rvec, riovcnt, UIO_FASTIOV,
378 iovstack_r, &iov_r, 0);
382 rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
386 if (iov_r != iovstack_r)
388 if (iov_l != iovstack_l)
394 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
395 unsigned long, liovcnt, const struct iovec __user *, rvec,
396 unsigned long, riovcnt, unsigned long, flags)
398 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
401 SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
402 const struct iovec __user *, lvec,
403 unsigned long, liovcnt, const struct iovec __user *, rvec,
404 unsigned long, riovcnt, unsigned long, flags)
406 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
412 compat_process_vm_rw(compat_pid_t pid,
413 const struct compat_iovec __user *lvec,
414 unsigned long liovcnt,
415 const struct compat_iovec __user *rvec,
416 unsigned long riovcnt,
417 unsigned long flags, int vm_write)
419 struct iovec iovstack_l[UIO_FASTIOV];
420 struct iovec iovstack_r[UIO_FASTIOV];
421 struct iovec *iov_l = iovstack_l;
422 struct iovec *iov_r = iovstack_r;
423 ssize_t rc = -EFAULT;
428 if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec)))
431 if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec)))
435 rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
436 UIO_FASTIOV, iovstack_l,
439 rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
440 UIO_FASTIOV, iovstack_l,
444 rc = compat_rw_copy_check_uvector(READ, rvec, riovcnt,
445 UIO_FASTIOV, iovstack_r,
450 rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
454 if (iov_r != iovstack_r)
456 if (iov_l != iovstack_l)
464 compat_sys_process_vm_readv(compat_pid_t pid,
465 const struct compat_iovec __user *lvec,
466 unsigned long liovcnt,
467 const struct compat_iovec __user *rvec,
468 unsigned long riovcnt,
471 return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
476 compat_sys_process_vm_writev(compat_pid_t pid,
477 const struct compat_iovec __user *lvec,
478 unsigned long liovcnt,
479 const struct compat_iovec __user *rvec,
480 unsigned long riovcnt,
483 return compat_process_vm_rw(pid, lvec, liovcnt, rvec,