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 * @pages: array of pointers to pages we want to copy
27 * @start_offset: offset in page to start copying from/to
28 * @len: number of bytes to copy
29 * @iter: where to copy to/from locally
30 * @vm_write: 0 means copy from, 1 means copy to
31 * Returns 0 on success, error code otherwise
33 static int process_vm_rw_pages(struct page **pages,
36 struct iov_iter *iter,
39 /* Do the copy for each page */
40 while (len && iov_iter_count(iter)) {
41 struct page *page = *pages++;
42 size_t copy = PAGE_SIZE - offset;
49 copied = copy_page_from_iter(page, offset, copy, iter);
50 set_page_dirty_lock(page);
52 copied = copy_page_to_iter(page, offset, copy, iter);
55 if (copied < copy && iov_iter_count(iter))
62 /* Maximum number of pages kmalloc'd to hold struct page's during copy */
63 #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
66 * process_vm_rw_single_vec - read/write pages from task specified
67 * @addr: start memory address of target process
68 * @len: size of area to copy to/from
69 * @iter: where to copy to/from locally
70 * @process_pages: struct pages area that can store at least
71 * nr_pages_to_copy struct page pointers
73 * @task: task to read/write from
74 * @vm_write: 0 means copy from, 1 means copy to
75 * Returns 0 on success or on failure error code
77 static int process_vm_rw_single_vec(unsigned long addr,
79 struct iov_iter *iter,
80 struct page **process_pages,
82 struct task_struct *task,
85 unsigned long pa = addr & PAGE_MASK;
86 unsigned long start_offset = addr - pa;
87 unsigned long nr_pages;
89 unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
90 / sizeof(struct pages *);
91 unsigned int flags = FOLL_REMOTE;
93 /* Work out address and page range required */
96 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
101 while (!rc && nr_pages && iov_iter_count(iter)) {
102 int pages = min(nr_pages, max_pages_per_loop);
106 * Get the pages we're interested in. We must
107 * add FOLL_REMOTE because task/mm might not
108 * current/current->mm
110 pages = __get_user_pages_unlocked(task, mm, pa, pages,
111 process_pages, flags);
115 bytes = pages * PAGE_SIZE - start_offset;
119 rc = process_vm_rw_pages(process_pages,
120 start_offset, bytes, iter,
125 pa += pages * PAGE_SIZE;
127 put_page(process_pages[--pages]);
133 /* Maximum number of entries for process pages array
134 which lives on stack */
135 #define PVM_MAX_PP_ARRAY_COUNT 16
138 * process_vm_rw_core - core of reading/writing pages from task specified
139 * @pid: PID of process to read/write from/to
140 * @iter: where to copy to/from locally
141 * @rvec: iovec array specifying where to copy to/from in the other process
142 * @riovcnt: size of rvec array
143 * @flags: currently unused
144 * @vm_write: 0 if reading from other process, 1 if writing to other process
145 * Returns the number of bytes read/written or error code. May
146 * return less bytes than expected if an error occurs during the copying
149 static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
150 const struct iovec *rvec,
151 unsigned long riovcnt,
152 unsigned long flags, int vm_write)
154 struct task_struct *task;
155 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
156 struct page **process_pages = pp_stack;
157 struct mm_struct *mm;
160 unsigned long nr_pages = 0;
161 unsigned long nr_pages_iov;
163 size_t total_len = iov_iter_count(iter);
166 * Work out how many pages of struct pages we're going to need
167 * when eventually calling get_user_pages
169 for (i = 0; i < riovcnt; i++) {
170 iov_len = rvec[i].iov_len;
172 nr_pages_iov = ((unsigned long)rvec[i].iov_base
174 / PAGE_SIZE - (unsigned long)rvec[i].iov_base
176 nr_pages = max(nr_pages, nr_pages_iov);
183 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
184 /* For reliability don't try to kmalloc more than
186 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
187 sizeof(struct pages *)*nr_pages),
194 /* Get process information */
196 task = find_task_by_vpid(pid);
198 get_task_struct(task);
202 goto free_proc_pages;
205 mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS);
206 if (!mm || IS_ERR(mm)) {
207 rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
209 * Explicitly map EACCES to EPERM as EPERM is a more a
210 * appropriate error code for process_vw_readv/writev
214 goto put_task_struct;
217 for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++)
218 rc = process_vm_rw_single_vec(
219 (unsigned long)rvec[i].iov_base, rvec[i].iov_len,
220 iter, process_pages, mm, task, vm_write);
222 /* copied = space before - space after */
223 total_len -= iov_iter_count(iter);
225 /* If we have managed to copy any data at all then
226 we return the number of bytes copied. Otherwise
227 we return the error code */
234 put_task_struct(task);
237 if (process_pages != pp_stack)
238 kfree(process_pages);
243 * process_vm_rw - check iovecs before calling core routine
244 * @pid: PID of process to read/write from/to
245 * @lvec: iovec array specifying where to copy to/from locally
246 * @liovcnt: size of lvec array
247 * @rvec: iovec array specifying where to copy to/from in the other process
248 * @riovcnt: size of rvec array
249 * @flags: currently unused
250 * @vm_write: 0 if reading from other process, 1 if writing to other process
251 * Returns the number of bytes read/written or error code. May
252 * return less bytes than expected if an error occurs during the copying
255 static ssize_t process_vm_rw(pid_t pid,
256 const struct iovec __user *lvec,
257 unsigned long liovcnt,
258 const struct iovec __user *rvec,
259 unsigned long riovcnt,
260 unsigned long flags, int vm_write)
262 struct iovec iovstack_l[UIO_FASTIOV];
263 struct iovec iovstack_r[UIO_FASTIOV];
264 struct iovec *iov_l = iovstack_l;
265 struct iovec *iov_r = iovstack_r;
266 struct iov_iter iter;
268 int dir = vm_write ? WRITE : READ;
274 rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
277 if (!iov_iter_count(&iter))
280 rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
285 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
288 if (iov_r != iovstack_r)
295 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
296 unsigned long, liovcnt, const struct iovec __user *, rvec,
297 unsigned long, riovcnt, unsigned long, flags)
299 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
302 SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
303 const struct iovec __user *, lvec,
304 unsigned long, liovcnt, const struct iovec __user *, rvec,
305 unsigned long, riovcnt, unsigned long, flags)
307 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
313 compat_process_vm_rw(compat_pid_t pid,
314 const struct compat_iovec __user *lvec,
315 unsigned long liovcnt,
316 const struct compat_iovec __user *rvec,
317 unsigned long riovcnt,
318 unsigned long flags, int vm_write)
320 struct iovec iovstack_l[UIO_FASTIOV];
321 struct iovec iovstack_r[UIO_FASTIOV];
322 struct iovec *iov_l = iovstack_l;
323 struct iovec *iov_r = iovstack_r;
324 struct iov_iter iter;
325 ssize_t rc = -EFAULT;
326 int dir = vm_write ? WRITE : READ;
331 rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
334 if (!iov_iter_count(&iter))
336 rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
337 UIO_FASTIOV, iovstack_r,
342 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
345 if (iov_r != iovstack_r)
351 COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid,
352 const struct compat_iovec __user *, lvec,
353 compat_ulong_t, liovcnt,
354 const struct compat_iovec __user *, rvec,
355 compat_ulong_t, riovcnt,
356 compat_ulong_t, flags)
358 return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
362 COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid,
363 const struct compat_iovec __user *, lvec,
364 compat_ulong_t, liovcnt,
365 const struct compat_iovec __user *, rvec,
366 compat_ulong_t, riovcnt,
367 compat_ulong_t, flags)
369 return compat_process_vm_rw(pid, lvec, liovcnt, rvec,