[mirror_ubuntu-zesty-kernel.git] / mm / process_vm_access.c

/*
 * linux/mm/process_vm_access.c
 *
 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/mm.h>
#include <linux/uio.h>
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/syscalls.h>

#ifdef CONFIG_COMPAT
#include <linux/compat.h>
#endif

/**
 * process_vm_rw_pages - read/write pages from task specified
 * @task: task to read/write from
 * @mm: mm for task
 * @process_pages: struct pages area that can store at least
 *  nr_pages_to_copy struct page pointers
 * @pa: address of page in task to start copying from/to
 * @start_offset: offset in page to start copying from/to
 * @len: number of bytes to copy
 * @lvec: iovec array specifying where to copy to/from
 * @lvec_cnt: number of elements in iovec array
 * @lvec_current: index in iovec array we are up to
 * @lvec_offset: offset in bytes from current iovec iov_base we are up to
 * @vm_write: 0 means copy from, 1 means copy to
 * @nr_pages_to_copy: number of pages to copy
 * @bytes_copied: returns number of bytes successfully copied
 * Returns 0 on success, error code otherwise
 */
static int process_vm_rw_pages(struct task_struct *task,
			       struct mm_struct *mm,
			       struct page **process_pages,
			       unsigned long pa,
			       unsigned long start_offset,
			       unsigned long len,
			       const struct iovec *lvec,
			       unsigned long lvec_cnt,
			       unsigned long *lvec_current,
			       size_t *lvec_offset,
			       int vm_write,
			       unsigned int nr_pages_to_copy,
			       ssize_t *bytes_copied)
{
	int pages_pinned;
	void *target_kaddr;
	int pgs_copied = 0;
	int j;
	int ret;
	ssize_t bytes_to_copy;
	ssize_t rc = 0;

	*bytes_copied = 0;

	/* Get the pages we're interested in */
	down_read(&mm->mmap_sem);
	pages_pinned = get_user_pages(task, mm, pa,
				      nr_pages_to_copy,
				      vm_write, 0, process_pages, NULL);
	up_read(&mm->mmap_sem);

	if (pages_pinned != nr_pages_to_copy) {
		rc = -EFAULT;
		goto end;
	}

	/* Do the copy for each page */
	for (pgs_copied = 0;
	     (pgs_copied < nr_pages_to_copy) && (*lvec_current < lvec_cnt);
	     pgs_copied++) {
		/* Make sure we have a non zero length iovec */
		while (*lvec_current < lvec_cnt
		       && lvec[*lvec_current].iov_len == 0)
			(*lvec_current)++;
		if (*lvec_current == lvec_cnt)
			break;

		/*
		 * Will copy smallest of:
		 * - bytes remaining in page
		 * - bytes remaining in destination iovec
		 */
		bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset,
				      len - *bytes_copied);
		bytes_to_copy = min_t(ssize_t, bytes_to_copy,
				      lvec[*lvec_current].iov_len
				      - *lvec_offset);

		target_kaddr = kmap(process_pages[pgs_copied]) + start_offset;

		if (vm_write)
			ret = copy_from_user(target_kaddr,
					     lvec[*lvec_current].iov_base
					     + *lvec_offset,
					     bytes_to_copy);
		else
			ret = copy_to_user(lvec[*lvec_current].iov_base
					   + *lvec_offset,
					   target_kaddr, bytes_to_copy);
		kunmap(process_pages[pgs_copied]);
		if (ret) {
			*bytes_copied += bytes_to_copy - ret;
			pgs_copied++;
			rc = -EFAULT;
			goto end;
		}
		*bytes_copied += bytes_to_copy;
		*lvec_offset += bytes_to_copy;
		if (*lvec_offset == lvec[*lvec_current].iov_len) {
			/*
			 * Need to copy remaining part of page into the
			 * next iovec if there are any bytes left in page
			 */
			(*lvec_current)++;
			*lvec_offset = 0;
			start_offset = (start_offset + bytes_to_copy)
				% PAGE_SIZE;
			if (start_offset)
				pgs_copied--;
		} else {
			start_offset = 0;
		}
	}

end:
	if (vm_write) {
		for (j = 0; j < pages_pinned; j++) {
			if (j < pgs_copied)
				set_page_dirty_lock(process_pages[j]);
			put_page(process_pages[j]);
		}
	} else {
		for (j = 0; j < pages_pinned; j++)
			put_page(process_pages[j]);
	}

	return rc;
}

/* Maximum number of pages kmalloc'd to hold struct page's during copy */
#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)

/**
 * process_vm_rw_single_vec - read/write pages from task specified
 * @addr: start memory address of target process
 * @len: size of area to copy to/from
 * @lvec: iovec array specifying where to copy to/from locally
 * @lvec_cnt: number of elements in iovec array
 * @lvec_current: index in iovec array we are up to
 * @lvec_offset: offset in bytes from current iovec iov_base we are up to
 * @process_pages: struct pages area that can store at least
 *  nr_pages_to_copy struct page pointers
 * @mm: mm for task
 * @task: task to read/write from
 * @vm_write: 0 means copy from, 1 means copy to
 * @bytes_copied: returns number of bytes successfully copied
 * Returns 0 on success or on failure error code
 */
static int process_vm_rw_single_vec(unsigned long addr,
				    unsigned long len,
				    const struct iovec *lvec,
				    unsigned long lvec_cnt,
				    unsigned long *lvec_current,
				    size_t *lvec_offset,
				    struct page **process_pages,
				    struct mm_struct *mm,
				    struct task_struct *task,
				    int vm_write,
				    ssize_t *bytes_copied)
{
	unsigned long pa = addr & PAGE_MASK;
	unsigned long start_offset = addr - pa;
	unsigned long nr_pages;
	ssize_t bytes_copied_loop;
	ssize_t rc = 0;
	unsigned long nr_pages_copied = 0;
	unsigned long nr_pages_to_copy;
	unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
		/ sizeof(struct pages *);

	*bytes_copied = 0;

	/* Work out address and page range required */
	if (len == 0)
		return 0;
	nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;

	while ((nr_pages_copied < nr_pages) && (*lvec_current < lvec_cnt)) {
		nr_pages_to_copy = min(nr_pages - nr_pages_copied,
				       max_pages_per_loop);

		rc = process_vm_rw_pages(task, mm, process_pages, pa,
					 start_offset, len,
					 lvec, lvec_cnt,
					 lvec_current, lvec_offset,
					 vm_write, nr_pages_to_copy,
					 &bytes_copied_loop);
		start_offset = 0;
		*bytes_copied += bytes_copied_loop;

		if (rc < 0) {
			return rc;
		} else {
			len -= bytes_copied_loop;
			nr_pages_copied += nr_pages_to_copy;
			pa += nr_pages_to_copy * PAGE_SIZE;
		}
	}

	return rc;
}

/* Maximum number of entries for process pages array
   which lives on stack */
#define PVM_MAX_PP_ARRAY_COUNT 16

/**
 * process_vm_rw_core - core of reading/writing pages from task specified
 * @pid: PID of process to read/write from/to
 * @lvec: iovec array specifying where to copy to/from locally
 * @liovcnt: size of lvec array
 * @rvec: iovec array specifying where to copy to/from in the other process
 * @riovcnt: size of rvec array
 * @flags: currently unused
 * @vm_write: 0 if reading from other process, 1 if writing to other process
 * Returns the number of bytes read/written or error code. May
 *  return less bytes than expected if an error occurs during the copying
 *  process.
 */
static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
				  unsigned long liovcnt,
				  const struct iovec *rvec,
				  unsigned long riovcnt,
				  unsigned long flags, int vm_write)
{
	struct task_struct *task;
	struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
	struct page **process_pages = pp_stack;
	struct mm_struct *mm;
	unsigned long i;
	ssize_t rc = 0;
	ssize_t bytes_copied_loop;
	ssize_t bytes_copied = 0;
	unsigned long nr_pages = 0;
	unsigned long nr_pages_iov;
	unsigned long iov_l_curr_idx = 0;
	size_t iov_l_curr_offset = 0;
	ssize_t iov_len;

	/*
	 * Work out how many pages of struct pages we're going to need
	 * when eventually calling get_user_pages
	 */
	for (i = 0; i < riovcnt; i++) {
		iov_len = rvec[i].iov_len;
		if (iov_len > 0) {
			nr_pages_iov = ((unsigned long)rvec[i].iov_base
					+ iov_len)
				/ PAGE_SIZE - (unsigned long)rvec[i].iov_base
				/ PAGE_SIZE + 1;
			nr_pages = max(nr_pages, nr_pages_iov);
		}
	}

	if (nr_pages == 0)
		return 0;

	if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
		/* For reliability don't try to kmalloc more than
		   2 pages worth */
		process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
					      sizeof(struct pages *)*nr_pages),
					GFP_KERNEL);

		if (!process_pages)
			return -ENOMEM;
	}

	/* Get process information */
	rcu_read_lock();
	task = find_task_by_vpid(pid);
	if (task)
		get_task_struct(task);
	rcu_read_unlock();
	if (!task) {
		rc = -ESRCH;
		goto free_proc_pages;
	}

	task_lock(task);
	if (__ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
		task_unlock(task);
		rc = -EPERM;
		goto put_task_struct;
	}
	mm = task->mm;

	if (!mm || (task->flags & PF_KTHREAD)) {
		task_unlock(task);
		rc = -EINVAL;
		goto put_task_struct;
	}

	atomic_inc(&mm->mm_users);
	task_unlock(task);

	for (i = 0; i < riovcnt && iov_l_curr_idx < liovcnt; i++) {
		rc = process_vm_rw_single_vec(
			(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
			lvec, liovcnt, &iov_l_curr_idx, &iov_l_curr_offset,
			process_pages, mm, task, vm_write, &bytes_copied_loop);
		bytes_copied += bytes_copied_loop;
		if (rc != 0) {
			/* If we have managed to copy any data at all then
			   we return the number of bytes copied. Otherwise
			   we return the error code */
			if (bytes_copied)
				rc = bytes_copied;
			goto put_mm;
		}
	}

	rc = bytes_copied;
put_mm:
	mmput(mm);

put_task_struct:
	put_task_struct(task);

free_proc_pages:
	if (process_pages != pp_stack)
		kfree(process_pages);
	return rc;
}

/**
 * process_vm_rw - check iovecs before calling core routine
 * @pid: PID of process to read/write from/to
 * @lvec: iovec array specifying where to copy to/from locally
 * @liovcnt: size of lvec array
 * @rvec: iovec array specifying where to copy to/from in the other process
 * @riovcnt: size of rvec array
 * @flags: currently unused
 * @vm_write: 0 if reading from other process, 1 if writing to other process
 * Returns the number of bytes read/written or error code. May
 *  return less bytes than expected if an error occurs during the copying
 *  process.
 */
static ssize_t process_vm_rw(pid_t pid,
			     const struct iovec __user *lvec,
			     unsigned long liovcnt,
			     const struct iovec __user *rvec,
			     unsigned long riovcnt,
			     unsigned long flags, int vm_write)
{
	struct iovec iovstack_l[UIO_FASTIOV];
	struct iovec iovstack_r[UIO_FASTIOV];
	struct iovec *iov_l = iovstack_l;
	struct iovec *iov_r = iovstack_r;
	ssize_t rc;

	if (flags != 0)
		return -EINVAL;

	/* Check iovecs */
	if (vm_write)
		rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
					   iovstack_l, &iov_l, 1);
	else
		rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
					   iovstack_l, &iov_l, 1);
	if (rc <= 0)
		goto free_iovecs;

	rc = rw_copy_check_uvector(READ, rvec, riovcnt, UIO_FASTIOV,
				   iovstack_r, &iov_r, 0);
	if (rc <= 0)
		goto free_iovecs;

	rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
				vm_write);

free_iovecs:
	if (iov_r != iovstack_r)
		kfree(iov_r);
	if (iov_l != iovstack_l)
		kfree(iov_l);

	return rc;
}

SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
		unsigned long, liovcnt, const struct iovec __user *, rvec,
		unsigned long, riovcnt,	unsigned long, flags)
{
	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
}

SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
		const struct iovec __user *, lvec,
		unsigned long, liovcnt, const struct iovec __user *, rvec,
		unsigned long, riovcnt,	unsigned long, flags)
{
	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
}

#ifdef CONFIG_COMPAT

asmlinkage ssize_t
compat_process_vm_rw(compat_pid_t pid,
		     const struct compat_iovec __user *lvec,
		     unsigned long liovcnt,
		     const struct compat_iovec __user *rvec,
		     unsigned long riovcnt,
		     unsigned long flags, int vm_write)
{
	struct iovec iovstack_l[UIO_FASTIOV];
	struct iovec iovstack_r[UIO_FASTIOV];
	struct iovec *iov_l = iovstack_l;
	struct iovec *iov_r = iovstack_r;
	ssize_t rc = -EFAULT;

	if (flags != 0)
		return -EINVAL;

	if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec)))
		goto out;

	if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec)))
		goto out;

	if (vm_write)
		rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
						  UIO_FASTIOV, iovstack_l,
						  &iov_l, 1);
	else
		rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
						  UIO_FASTIOV, iovstack_l,
						  &iov_l, 1);
	if (rc <= 0)
		goto free_iovecs;
	rc = compat_rw_copy_check_uvector(READ, rvec, riovcnt,
					  UIO_FASTIOV, iovstack_r,
					  &iov_r, 0);
	if (rc <= 0)
		goto free_iovecs;

	rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
			   vm_write);

free_iovecs:
	if (iov_r != iovstack_r)
		kfree(iov_r);
	if (iov_l != iovstack_l)
		kfree(iov_l);

out:
	return rc;
}

asmlinkage ssize_t
compat_sys_process_vm_readv(compat_pid_t pid,
			    const struct compat_iovec __user *lvec,
			    unsigned long liovcnt,
			    const struct compat_iovec __user *rvec,
			    unsigned long riovcnt,
			    unsigned long flags)
{
	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
				    riovcnt, flags, 0);
}

asmlinkage ssize_t
compat_sys_process_vm_writev(compat_pid_t pid,
			     const struct compat_iovec __user *lvec,
			     unsigned long liovcnt,
			     const struct compat_iovec __user *rvec,
			     unsigned long riovcnt,
			     unsigned long flags)
{
	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
				    riovcnt, flags, 1);
}

#endif
Commit	Line	Data
fcf63409 CY	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	task_lock(task);
302	if (__ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
303	task_unlock(task);
304	rc = -EPERM;
305	goto put_task_struct;
306	}
307	mm = task->mm;
308
309	if (!mm \|\| (task->flags & PF_KTHREAD)) {
310	task_unlock(task);
311	rc = -EINVAL;
312	goto put_task_struct;
313	}
314
315	atomic_inc(&mm->mm_users);
316	task_unlock(task);
317
318	for (i = 0; i < riovcnt && iov_l_curr_idx < liovcnt; i++) {
319	rc = process_vm_rw_single_vec(
320	(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
321	lvec, liovcnt, &iov_l_curr_idx, &iov_l_curr_offset,
322	process_pages, mm, task, vm_write, &bytes_copied_loop);
323	bytes_copied += bytes_copied_loop;
324	if (rc != 0) {
325	/* If we have managed to copy any data at all then
326	we return the number of bytes copied. Otherwise
327	we return the error code */
328	if (bytes_copied)
329	rc = bytes_copied;
330	goto put_mm;
331	}
332	}
333
334	rc = bytes_copied;
335	put_mm:
336	mmput(mm);
337
338	put_task_struct:
339	put_task_struct(task);
340
341	free_proc_pages:
342	if (process_pages != pp_stack)
343	kfree(process_pages);
344	return rc;
345	}
346
347	/**
348	* process_vm_rw - check iovecs before calling core routine
349	* @pid: PID of process to read/write from/to
350	* @lvec: iovec array specifying where to copy to/from locally
351	* @liovcnt: size of lvec array
352	* @rvec: iovec array specifying where to copy to/from in the other process
353	* @riovcnt: size of rvec array
354	* @flags: currently unused
355	* @vm_write: 0 if reading from other process, 1 if writing to other process
356	* Returns the number of bytes read/written or error code. May
357	* return less bytes than expected if an error occurs during the copying
358	* process.
359	*/
360	static ssize_t process_vm_rw(pid_t pid,
361	const struct iovec __user *lvec,
362	unsigned long liovcnt,
363	const struct iovec __user *rvec,
364	unsigned long riovcnt,
365	unsigned long flags, int vm_write)
366	{
367	struct iovec iovstack_l[UIO_FASTIOV];
368	struct iovec iovstack_r[UIO_FASTIOV];
369	struct iovec *iov_l = iovstack_l;
370	struct iovec *iov_r = iovstack_r;
371	ssize_t rc;
372
373	if (flags != 0)
374	return -EINVAL;
375
376	/* Check iovecs */
377	if (vm_write)
378	rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
379	iovstack_l, &iov_l, 1);
380	else
381	rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
382	iovstack_l, &iov_l, 1);
383	if (rc <= 0)
384	goto free_iovecs;
385
386	rc = rw_copy_check_uvector(READ, rvec, riovcnt, UIO_FASTIOV,
387	iovstack_r, &iov_r, 0);
388	if (rc <= 0)
389	goto free_iovecs;
390
391	rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
392	vm_write);
393
394	free_iovecs:
395	if (iov_r != iovstack_r)
396	kfree(iov_r);
397	if (iov_l != iovstack_l)
398	kfree(iov_l);
399
400	return rc;
401	}
402
403	SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
404	unsigned long, liovcnt, const struct iovec __user *, rvec,
405	unsigned long, riovcnt, unsigned long, flags)
406	{
407	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
408	}
409
410	SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
411	const struct iovec __user *, lvec,
412	unsigned long, liovcnt, const struct iovec __user *, rvec,
413	unsigned long, riovcnt, unsigned long, flags)
414	{
415	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
416	}
417
418	#ifdef CONFIG_COMPAT
419
420	asmlinkage ssize_t
421	compat_process_vm_rw(compat_pid_t pid,
422	const struct compat_iovec __user *lvec,
423	unsigned long liovcnt,
424	const struct compat_iovec __user *rvec,
425	unsigned long riovcnt,
426	unsigned long flags, int vm_write)
427	{
428	struct iovec iovstack_l[UIO_FASTIOV];
429	struct iovec iovstack_r[UIO_FASTIOV];
430	struct iovec *iov_l = iovstack_l;
431	struct iovec *iov_r = iovstack_r;
432	ssize_t rc = -EFAULT;
433
434	if (flags != 0)
435	return -EINVAL;
436
437	if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec)))
438	goto out;
439
440	if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec)))
441	goto out;
442
443	if (vm_write)
444	rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
445	UIO_FASTIOV, iovstack_l,
446	&iov_l, 1);
447	else
448	rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
449	UIO_FASTIOV, iovstack_l,
450	&iov_l, 1);
451	if (rc <= 0)
452	goto free_iovecs;
453	rc = compat_rw_copy_check_uvector(READ, rvec, riovcnt,
454	UIO_FASTIOV, iovstack_r,
455	&iov_r, 0);
456	if (rc <= 0)
457	goto free_iovecs;
458
459	rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
460	vm_write);
461
462	free_iovecs:
463	if (iov_r != iovstack_r)
464	kfree(iov_r);
465	if (iov_l != iovstack_l)
466	kfree(iov_l);
467
468	out:
469	return rc;
470	}
471
472	asmlinkage ssize_t
473	compat_sys_process_vm_readv(compat_pid_t pid,
474	const struct compat_iovec __user *lvec,
475	unsigned long liovcnt,
476	const struct compat_iovec __user *rvec,
477	unsigned long riovcnt,
478	unsigned long flags)
479	{
480	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
481	riovcnt, flags, 0);
482	}
483
484	asmlinkage ssize_t
485	compat_sys_process_vm_writev(compat_pid_t pid,
486	const struct compat_iovec __user *lvec,
487	unsigned long liovcnt,
488	const struct compat_iovec __user *rvec,
489	unsigned long riovcnt,
490	unsigned long flags)
491	{
492	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
493	riovcnt, flags, 1);
494	}
495
496	#endif