[deliverable/linux.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 **iovp,
			       unsigned long *left,
			       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;
	const struct iovec *iov = *iovp;

	*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) && *left;
	     pgs_copied++) {
		/* Make sure we have a non zero length iovec */
		while (*left && iov->iov_len == 0) {
			iov++;
			(*left)--;
		}
		if (!*left)
			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,
				      iov->iov_len
				      - *lvec_offset);

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

		if (vm_write)
			ret = copy_from_user(target_kaddr,
					     iov->iov_base
					     + *lvec_offset,
					     bytes_to_copy);
		else
			ret = copy_to_user(iov->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 == iov->iov_len) {
			/*
			 * Need to copy remaining part of page into the
			 * next iovec if there are any bytes left in page
			 */
			(*left)--;
			iov++;
			*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]);
	}

	*iovp = iov;
	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 **iovp,
				    unsigned long *left,
				    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) && *left) {
		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,
					 iovp, left,
					 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 left = liovcnt;
	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;
	}

	mm = mm_access(task, PTRACE_MODE_ATTACH);
	if (!mm || IS_ERR(mm)) {
		rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
		/*
		 * Explicitly map EACCES to EPERM as EPERM is a more a
		 * appropriate error code for process_vw_readv/writev
		 */
		if (rc == -EACCES)
			rc = -EPERM;
		goto put_task_struct;
	}

	for (i = 0; i < riovcnt && left; i++) {
		rc = process_vm_rw_single_vec(
			(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
			&lvec, &left, &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);
	else
		rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
					   iovstack_l, &iov_l);
	if (rc <= 0)
		goto free_iovecs;

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

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,
c61c7038	48	const struct iovec **iovp,
1291afc1	49	unsigned long *left,
fcf63409 CY	50	size_t *lvec_offset,
	51	int vm_write,
	52	unsigned int nr_pages_to_copy,
	53	ssize_t *bytes_copied)
	54	{
	55	int pages_pinned;
	56	void *target_kaddr;
	57	int pgs_copied = 0;
	58	int j;
	59	int ret;
	60	ssize_t bytes_to_copy;
	61	ssize_t rc = 0;
c61c7038	62	const struct iovec iov = iovp;
fcf63409 CY	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;
1291afc1	80	(pgs_copied < nr_pages_to_copy) && *left;
fcf63409 CY	81	pgs_copied++) {
fcf63409 CY	82	/* Make sure we have a non zero length iovec */
1291afc1	83	while (*left && iov->iov_len == 0) {
480402e1	84	iov++;
1291afc1	85	(*left)--;
480402e1	86	}
1291afc1	87	if (!*left)
fcf63409 CY	88	break;
	89
	90	/*
	91	* Will copy smallest of:
	92	* - bytes remaining in page
	93	* - bytes remaining in destination iovec
	94	*/
	95	bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset,
	96	len - *bytes_copied);
	97	bytes_to_copy = min_t(ssize_t, bytes_to_copy,
480402e1	98	iov->iov_len
fcf63409 CY	99	- *lvec_offset);
	100
	101	target_kaddr = kmap(process_pages[pgs_copied]) + start_offset;
	102
	103	if (vm_write)
	104	ret = copy_from_user(target_kaddr,
480402e1	105	iov->iov_base
fcf63409 CY	106	+ *lvec_offset,
	107	bytes_to_copy);
	108	else
480402e1	109	ret = copy_to_user(iov->iov_base
fcf63409 CY	110	+ *lvec_offset,
	111	target_kaddr, bytes_to_copy);
	112	kunmap(process_pages[pgs_copied]);
	113	if (ret) {
	114	*bytes_copied += bytes_to_copy - ret;
	115	pgs_copied++;
	116	rc = -EFAULT;
	117	goto end;
	118	}
	119	*bytes_copied += bytes_to_copy;
	120	*lvec_offset += bytes_to_copy;
480402e1	121	if (*lvec_offset == iov->iov_len) {
fcf63409 CY	122	/*
	123	* Need to copy remaining part of page into the
	124	* next iovec if there are any bytes left in page
	125	*/
1291afc1	126	(*left)--;
480402e1	127	iov++;
fcf63409 CY	128	*lvec_offset = 0;
	129	start_offset = (start_offset + bytes_to_copy)
	130	% PAGE_SIZE;
	131	if (start_offset)
	132	pgs_copied--;
	133	} else {
	134	start_offset = 0;
	135	}
	136	}
	137
	138	end:
	139	if (vm_write) {
	140	for (j = 0; j < pages_pinned; j++) {
	141	if (j < pgs_copied)
	142	set_page_dirty_lock(process_pages[j]);
	143	put_page(process_pages[j]);
	144	}
	145	} else {
	146	for (j = 0; j < pages_pinned; j++)
	147	put_page(process_pages[j]);
	148	}
	149
c61c7038	150	*iovp = iov;
fcf63409 CY	151	return rc;
	152	}
	153
	154	/* Maximum number of pages kmalloc'd to hold struct page's during copy */
	155	#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
	156
	157	/**
	158	* process_vm_rw_single_vec - read/write pages from task specified
	159	* @addr: start memory address of target process
	160	* @len: size of area to copy to/from
	161	* @lvec: iovec array specifying where to copy to/from locally
	162	* @lvec_cnt: number of elements in iovec array
	163	* @lvec_current: index in iovec array we are up to
	164	* @lvec_offset: offset in bytes from current iovec iov_base we are up to
	165	* @process_pages: struct pages area that can store at least
	166	* nr_pages_to_copy struct page pointers
	167	* @mm: mm for task
	168	* @task: task to read/write from
	169	* @vm_write: 0 means copy from, 1 means copy to
	170	* @bytes_copied: returns number of bytes successfully copied
	171	* Returns 0 on success or on failure error code
	172	*/
	173	static int process_vm_rw_single_vec(unsigned long addr,
	174	unsigned long len,
12e3004e	175	const struct iovec **iovp,
1291afc1	176	unsigned long *left,
fcf63409 CY	177	size_t *lvec_offset,
	178	struct page **process_pages,
	179	struct mm_struct *mm,
	180	struct task_struct *task,
	181	int vm_write,
	182	ssize_t *bytes_copied)
	183	{
	184	unsigned long pa = addr & PAGE_MASK;
	185	unsigned long start_offset = addr - pa;
	186	unsigned long nr_pages;
	187	ssize_t bytes_copied_loop;
	188	ssize_t rc = 0;
	189	unsigned long nr_pages_copied = 0;
	190	unsigned long nr_pages_to_copy;
	191	unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
	192	/ sizeof(struct pages *);
	193
	194	*bytes_copied = 0;
	195
	196	/* Work out address and page range required */
	197	if (len == 0)
	198	return 0;
	199	nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
	200
1291afc1	201	while ((nr_pages_copied < nr_pages) && *left) {
fcf63409 CY	202	nr_pages_to_copy = min(nr_pages - nr_pages_copied,
	203	max_pages_per_loop);
	204
	205	rc = process_vm_rw_pages(task, mm, process_pages, pa,
	206	start_offset, len,
1291afc1 AV	207	iovp, left,
1291afc1 AV	208	lvec_offset,
fcf63409 CY	209	vm_write, nr_pages_to_copy,
	210	&bytes_copied_loop);
	211	start_offset = 0;
	212	*bytes_copied += bytes_copied_loop;
	213
	214	if (rc < 0) {
	215	return rc;
	216	} else {
	217	len -= bytes_copied_loop;
	218	nr_pages_copied += nr_pages_to_copy;
	219	pa += nr_pages_to_copy * PAGE_SIZE;
	220	}
	221	}
	222
	223	return rc;
	224	}
	225
	226	/* Maximum number of entries for process pages array
	227	which lives on stack */
	228	#define PVM_MAX_PP_ARRAY_COUNT 16
	229
	230	/**
	231	* process_vm_rw_core - core of reading/writing pages from task specified
	232	* @pid: PID of process to read/write from/to
	233	* @lvec: iovec array specifying where to copy to/from locally
	234	* @liovcnt: size of lvec array
	235	* @rvec: iovec array specifying where to copy to/from in the other process
	236	* @riovcnt: size of rvec array
	237	* @flags: currently unused
	238	* @vm_write: 0 if reading from other process, 1 if writing to other process
	239	* Returns the number of bytes read/written or error code. May
	240	* return less bytes than expected if an error occurs during the copying
	241	* process.
	242	*/
	243	static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
	244	unsigned long liovcnt,
	245	const struct iovec *rvec,
	246	unsigned long riovcnt,
	247	unsigned long flags, int vm_write)
	248	{
	249	struct task_struct *task;
	250	struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
	251	struct page **process_pages = pp_stack;
	252	struct mm_struct *mm;
	253	unsigned long i;
	254	ssize_t rc = 0;
	255	ssize_t bytes_copied_loop;
	256	ssize_t bytes_copied = 0;
	257	unsigned long nr_pages = 0;
	258	unsigned long nr_pages_iov;
1291afc1	259	unsigned long left = liovcnt;
fcf63409 CY	260	size_t iov_l_curr_offset = 0;
	261	ssize_t iov_len;
	262
	263	/*
	264	* Work out how many pages of struct pages we're going to need
	265	* when eventually calling get_user_pages
	266	*/
	267	for (i = 0; i < riovcnt; i++) {
	268	iov_len = rvec[i].iov_len;
	269	if (iov_len > 0) {
	270	nr_pages_iov = ((unsigned long)rvec[i].iov_base
	271	+ iov_len)
	272	/ PAGE_SIZE - (unsigned long)rvec[i].iov_base
	273	/ PAGE_SIZE + 1;
	274	nr_pages = max(nr_pages, nr_pages_iov);
	275	}
	276	}
	277
	278	if (nr_pages == 0)
	279	return 0;
	280
	281	if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
	282	/* For reliability don't try to kmalloc more than
	283	2 pages worth */
	284	process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
	285	sizeof(struct pages )nr_pages),
	286	GFP_KERNEL);
	287
	288	if (!process_pages)
	289	return -ENOMEM;
	290	}
	291
	292	/* Get process information */
	293	rcu_read_lock();
	294	task = find_task_by_vpid(pid);
	295	if (task)
	296	get_task_struct(task);
	297	rcu_read_unlock();
	298	if (!task) {
	299	rc = -ESRCH;
	300	goto free_proc_pages;
	301	}
	302
8cdb878d CY	303	mm = mm_access(task, PTRACE_MODE_ATTACH);
	304	if (!mm \|\| IS_ERR(mm)) {
	305	rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
	306	/*
	307	* Explicitly map EACCES to EPERM as EPERM is a more a
	308	* appropriate error code for process_vw_readv/writev
	309	*/
	310	if (rc == -EACCES)
	311	rc = -EPERM;
fcf63409 CY	312	goto put_task_struct;
	313	}
	314
1291afc1	315	for (i = 0; i < riovcnt && left; i++) {
fcf63409 CY	316	rc = process_vm_rw_single_vec(
fcf63409 CY	317	(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
1291afc1	318	&lvec, &left, &iov_l_curr_offset,
fcf63409 CY	319	process_pages, mm, task, vm_write, &bytes_copied_loop);
	320	bytes_copied += bytes_copied_loop;
	321	if (rc != 0) {
	322	/* If we have managed to copy any data at all then
	323	we return the number of bytes copied. Otherwise
	324	we return the error code */
	325	if (bytes_copied)
	326	rc = bytes_copied;
	327	goto put_mm;
	328	}
	329	}
	330
	331	rc = bytes_copied;
	332	put_mm:
	333	mmput(mm);
	334
	335	put_task_struct:
	336	put_task_struct(task);
	337
	338	free_proc_pages:
	339	if (process_pages != pp_stack)
	340	kfree(process_pages);
	341	return rc;
	342	}
	343
	344	/**
	345	* process_vm_rw - check iovecs before calling core routine
	346	* @pid: PID of process to read/write from/to
	347	* @lvec: iovec array specifying where to copy to/from locally
	348	* @liovcnt: size of lvec array
	349	* @rvec: iovec array specifying where to copy to/from in the other process
	350	* @riovcnt: size of rvec array
	351	* @flags: currently unused
	352	* @vm_write: 0 if reading from other process, 1 if writing to other process
	353	* Returns the number of bytes read/written or error code. May
	354	* return less bytes than expected if an error occurs during the copying
	355	* process.
	356	*/
	357	static ssize_t process_vm_rw(pid_t pid,
	358	const struct iovec __user *lvec,
	359	unsigned long liovcnt,
	360	const struct iovec __user *rvec,
	361	unsigned long riovcnt,
	362	unsigned long flags, int vm_write)
	363	{
	364	struct iovec iovstack_l[UIO_FASTIOV];
	365	struct iovec iovstack_r[UIO_FASTIOV];
	366	struct iovec *iov_l = iovstack_l;
	367	struct iovec *iov_r = iovstack_r;
	368	ssize_t rc;
	369
	370	if (flags != 0)
	371	return -EINVAL;
	372
	373	/* Check iovecs */
	374	if (vm_write)
	375	rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
ac34ebb3	376	iovstack_l, &iov_l);
fcf63409 CY	377	else
fcf63409 CY	378	rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
ac34ebb3	379	iovstack_l, &iov_l);
fcf63409 CY	380	if (rc <= 0)
	381	goto free_iovecs;
	382
ac34ebb3 CY	383	rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
ac34ebb3 CY	384	iovstack_r, &iov_r);
fcf63409 CY	385	if (rc <= 0)
	386	goto free_iovecs;
	387
	388	rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
	389	vm_write);
	390
	391	free_iovecs:
	392	if (iov_r != iovstack_r)
	393	kfree(iov_r);
	394	if (iov_l != iovstack_l)
	395	kfree(iov_l);
	396
	397	return rc;
	398	}
	399
	400	SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
	401	unsigned long, liovcnt, const struct iovec __user *, rvec,
	402	unsigned long, riovcnt, unsigned long, flags)
	403	{
	404	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
	405	}
	406
	407	SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
	408	const struct iovec __user *, lvec,
	409	unsigned long, liovcnt, const struct iovec __user *, rvec,
	410	unsigned long, riovcnt, unsigned long, flags)
	411	{
	412	return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
	413	}
	414
	415	#ifdef CONFIG_COMPAT
	416
	417	asmlinkage ssize_t
	418	compat_process_vm_rw(compat_pid_t pid,
	419	const struct compat_iovec __user *lvec,
	420	unsigned long liovcnt,
	421	const struct compat_iovec __user *rvec,
	422	unsigned long riovcnt,
	423	unsigned long flags, int vm_write)
	424	{
	425	struct iovec iovstack_l[UIO_FASTIOV];
	426	struct iovec iovstack_r[UIO_FASTIOV];
	427	struct iovec *iov_l = iovstack_l;
	428	struct iovec *iov_r = iovstack_r;
	429	ssize_t rc = -EFAULT;
	430
	431	if (flags != 0)
	432	return -EINVAL;
	433
fcf63409 CY	434	if (vm_write)
	435	rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
	436	UIO_FASTIOV, iovstack_l,
ac34ebb3	437	&iov_l);
fcf63409 CY	438	else
	439	rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
	440	UIO_FASTIOV, iovstack_l,
ac34ebb3	441	&iov_l);
fcf63409 CY	442	if (rc <= 0)
fcf63409 CY	443	goto free_iovecs;
ac34ebb3	444	rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
fcf63409	445	UIO_FASTIOV, iovstack_r,
ac34ebb3	446	&iov_r);
fcf63409 CY	447	if (rc <= 0)
	448	goto free_iovecs;
	449
	450	rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
	451	vm_write);
	452
	453	free_iovecs:
	454	if (iov_r != iovstack_r)
	455	kfree(iov_r);
	456	if (iov_l != iovstack_l)
	457	kfree(iov_l);
fcf63409 CY	458	return rc;
	459	}
	460
	461	asmlinkage ssize_t
	462	compat_sys_process_vm_readv(compat_pid_t pid,
	463	const struct compat_iovec __user *lvec,
	464	unsigned long liovcnt,
	465	const struct compat_iovec __user *rvec,
	466	unsigned long riovcnt,
	467	unsigned long flags)
	468	{
	469	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
	470	riovcnt, flags, 0);
	471	}
	472
	473	asmlinkage ssize_t
	474	compat_sys_process_vm_writev(compat_pid_t pid,
	475	const struct compat_iovec __user *lvec,
	476	unsigned long liovcnt,
	477	const struct compat_iovec __user *rvec,
	478	unsigned long riovcnt,
	479	unsigned long flags)
	480	{
	481	return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
	482	riovcnt, flags, 1);
	483	}
	484
	485	#endif