/*
* 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;
}
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 && 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);
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
