+#ifdef HAVE_ACCESS_PROCESS_VM
+ return access_process_vm(tsk, addr, buf, len, write);
+#else
+ /* Just copied from kernel for the kernels which doesn't
+ * have access_process_vm() exported */
+ struct mm_struct *mm;
+ struct vm_area_struct *vma;
+ struct page *page;
+ void *old_buf = buf;
+
+ mm = get_task_mm(tsk);
+ if (!mm)
+ return 0;
+
+ down_read(&mm->mmap_sem);
+ /* ignore errors, just check how much was sucessfully transfered */
+ while (len) {
+ int bytes, rc, offset;
+ void *maddr;
+
+ rc = get_user_pages(tsk, mm, addr, 1,
+ write, 1, &page, &vma);
+ if (rc <= 0)
+ break;
+
+ bytes = len;
+ offset = addr & (PAGE_SIZE-1);
+ if (bytes > PAGE_SIZE-offset)
+ bytes = PAGE_SIZE-offset;
+
+ maddr = kmap(page);
+ if (write) {
+ copy_to_user_page(vma, page, addr,
+ maddr + offset, buf, bytes);
+ set_page_dirty_lock(page);
+ } else {
+ copy_from_user_page(vma, page, addr,
+ buf, maddr + offset, bytes);
+ }
+ kunmap(page);
+ page_cache_release(page);
+ len -= bytes;
+ buf += bytes;
+ addr += bytes;
+ }
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+
+ return buf - old_buf;
+#endif /* HAVE_ACCESS_PROCESS_VM */
+}
+
+/* Read the environment variable of current process specified by @key. */
+int cfs_get_environ(const char *key, char *value, int *val_len)
+{
+ struct mm_struct *mm;
+ char *buffer, *tmp_buf = NULL;
+ int buf_len = CFS_PAGE_SIZE;
+ int key_len = strlen(key);
+ unsigned long addr;
+ int rc;
+ ENTRY;
+
+ buffer = cfs_alloc(buf_len, CFS_ALLOC_USER);
+ if (!buffer)
+ RETURN(-ENOMEM);
+
+ mm = get_task_mm(current);
+ if (!mm) {
+ cfs_free(buffer);
+ RETURN(-EINVAL);
+ }
+
+ /* Avoid deadlocks on mmap_sem if called from sys_mmap_pgoff(),
+ * which is already holding mmap_sem for writes. If some other
+ * thread gets the write lock in the meantime, this thread will
+ * block, but at least it won't deadlock on itself. LU-1735 */
+ if (down_read_trylock(&mm->mmap_sem) == 0)
+ return -EDEADLK;
+ up_read(&mm->mmap_sem);
+
+ addr = mm->env_start;
+ while (addr < mm->env_end) {
+ int this_len, retval, scan_len;
+ char *env_start, *env_end;
+
+ memset(buffer, 0, buf_len);
+
+ this_len = min_t(int, mm->env_end - addr, buf_len);
+ retval = cfs_access_process_vm(current, addr, buffer,
+ this_len, 0);
+ if (retval != this_len)
+ break;
+
+ addr += retval;
+
+ /* Parse the buffer to find out the specified key/value pair.
+ * The "key=value" entries are separated by '\0'. */
+ env_start = buffer;
+ scan_len = this_len;
+ while (scan_len) {
+ char *entry;
+ int entry_len;
+
+ env_end = memscan(env_start, '\0', scan_len);
+ LASSERT(env_end >= env_start &&
+ env_end <= env_start + scan_len);
+
+ /* The last entry of this buffer cross the buffer
+ * boundary, reread it in next cycle. */
+ if (unlikely(env_end - env_start == scan_len)) {
+ /* This entry is too large to fit in buffer */
+ if (unlikely(scan_len == this_len)) {
+ CERROR("Too long env variable.\n");
+ GOTO(out, rc = -EINVAL);
+ }
+ addr -= scan_len;
+ break;
+ }
+
+ entry = env_start;
+ entry_len = env_end - env_start;
+
+ /* Key length + length of '=' */
+ if (entry_len > key_len + 1 &&
+ !memcmp(entry, key, key_len)) {
+ entry += key_len + 1;
+ entry_len -= key_len + 1;
+ /* The 'value' buffer passed in is too small.*/
+ if (entry_len >= *val_len)
+ GOTO(out, rc = -EOVERFLOW);
+
+ memcpy(value, entry, entry_len);
+ *val_len = entry_len;
+ GOTO(out, rc = 0);
+ }
+
+ scan_len -= (env_end - env_start + 1);
+ env_start = env_end + 1;
+ }
+ }
+ GOTO(out, rc = -ENOENT);
+
+out:
+ mmput(mm);
+ cfs_free((void *)buffer);
+ if (tmp_buf)
+ cfs_free((void *)tmp_buf);
+ return rc;