// SPDX-License-Identifier: GPL-2.0-only

  /*

   * Access kernel or user memory without faulting.

   */

  #include <linux/export.h>

  #include <linux/mm.h>

  #include <linux/uaccess.h>

  bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
  		size_t size)

  {
  	return true;
  }

  #ifdef HAVE_GET_KERNEL_NOFAULT

  #define copy_from_kernel_nofault_loop(dst, src, len, type, err_label)	\

  	while (len >= sizeof(type)) {					\
  		__get_kernel_nofault(dst, src, type, err_label);		\
  		dst += sizeof(type);					\
  		src += sizeof(type);					\
  		len -= sizeof(type);					\
  	}

  long copy_from_kernel_nofault(void *dst, const void *src, size_t size)

  {

  	if (!copy_from_kernel_nofault_allowed(src, size))

  		return -ERANGE;

  
  	pagefault_disable();

  	copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
  	copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
  	copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
  	copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);

  	pagefault_enable();
  	return 0;
  Efault:
  	pagefault_enable();
  	return -EFAULT;
  }

  EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);

  #define copy_to_kernel_nofault_loop(dst, src, len, type, err_label)	\

  	while (len >= sizeof(type)) {					\
  		__put_kernel_nofault(dst, src, type, err_label);		\
  		dst += sizeof(type);					\
  		src += sizeof(type);					\
  		len -= sizeof(type);					\
  	}

  long copy_to_kernel_nofault(void *dst, const void *src, size_t size)

  {
  	pagefault_disable();

  	copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
  	copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
  	copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
  	copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);

  	pagefault_enable();
  	return 0;
  Efault:
  	pagefault_enable();
  	return -EFAULT;
  }
  
  long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
  {
  	const void *src = unsafe_addr;
  
  	if (unlikely(count <= 0))
  		return 0;

  	if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))

  		return -ERANGE;

  
  	pagefault_disable();
  	do {
  		__get_kernel_nofault(dst, src, u8, Efault);
  		dst++;
  		src++;
  	} while (dst[-1] && src - unsafe_addr < count);
  	pagefault_enable();
  
  	dst[-1] = '\0';
  	return src - unsafe_addr;
  Efault:
  	pagefault_enable();
  	dst[-1] = '\0';
  	return -EFAULT;
  }
  #else /* HAVE_GET_KERNEL_NOFAULT */

  /**

   * copy_from_kernel_nofault(): safely attempt to read from kernel-space

   * @dst: pointer to the buffer that shall take the data
   * @src: address to read from
   * @size: size of the data chunk
   *
   * Safely read from kernel address @src to the buffer at @dst.  If a kernel

   * fault happens, handle that and return -EFAULT.  If @src is not a valid kernel
   * address, return -ERANGE.

   *
   * We ensure that the copy_from_user is executed in atomic context so that

   * do_page_fault() doesn't attempt to take mmap_lock.  This makes

   * copy_from_kernel_nofault() suitable for use within regions where the caller

   * already holds mmap_lock, or other locks which nest inside mmap_lock.

   */

  long copy_from_kernel_nofault(void *dst, const void *src, size_t size)

  {
  	long ret;

  	mm_segment_t old_fs = get_fs();

  	if (!copy_from_kernel_nofault_allowed(src, size))

  		return -ERANGE;

  	set_fs(KERNEL_DS);

  	pagefault_disable();
  	ret = __copy_from_user_inatomic(dst, (__force const void __user *)src,
  			size);
  	pagefault_enable();

  	set_fs(old_fs);

  	if (ret)
  		return -EFAULT;
  	return 0;

  }

  EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);

  
  /**

   * copy_to_kernel_nofault(): safely attempt to write to a location

   * @dst: address to write to
   * @src: pointer to the data that shall be written
   * @size: size of the data chunk
   *
   * Safely write to address @dst from the buffer at @src.  If a kernel fault
   * happens, handle that and return -EFAULT.
   */

  long copy_to_kernel_nofault(void *dst, const void *src, size_t size)

  {
  	long ret;

  	mm_segment_t old_fs = get_fs();

  	set_fs(KERNEL_DS);

  	pagefault_disable();
  	ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
  	pagefault_enable();

  	set_fs(old_fs);

  	if (ret)
  		return -EFAULT;
  	return 0;

  }

  /**

   * strncpy_from_kernel_nofault: - Copy a NUL terminated string from unsafe

   *				 address.
   * @dst:   Destination address, in kernel space.  This buffer must be at
   *         least @count bytes long.
   * @unsafe_addr: Unsafe address.
   * @count: Maximum number of bytes to copy, including the trailing NUL.
   *
   * Copies a NUL-terminated string from unsafe address to kernel buffer.
   *
   * On success, returns the length of the string INCLUDING the trailing NUL.
   *

   * If access fails, returns -EFAULT (some data may have been copied and the
   * trailing NUL added).  If @unsafe_addr is not a valid kernel address, return
   * -ERANGE.

   *
   * If @count is smaller than the length of the string, copies @count-1 bytes,
   * sets the last byte of @dst buffer to NUL and returns @count.
   */

  long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
  {

  	mm_segment_t old_fs = get_fs();
  	const void *src = unsafe_addr;
  	long ret;
  
  	if (unlikely(count <= 0))
  		return 0;

  	if (!copy_from_kernel_nofault_allowed(unsafe_addr, count))

  		return -ERANGE;

  
  	set_fs(KERNEL_DS);
  	pagefault_disable();
  
  	do {

  		ret = __get_user(*dst++, (const char __user __force *)src++);

  	} while (dst[-1] && ret == 0 && src - unsafe_addr < count);
  
  	dst[-1] = '\0';
  	pagefault_enable();
  	set_fs(old_fs);

  	return ret ? -EFAULT : src - unsafe_addr;

  }

  #endif /* HAVE_GET_KERNEL_NOFAULT */

  
  /**

   * copy_from_user_nofault(): safely attempt to read from a user-space location

   * @dst: pointer to the buffer that shall take the data
   * @src: address to read from. This must be a user address.
   * @size: size of the data chunk
   *
   * Safely read from user address @src to the buffer at @dst. If a kernel fault
   * happens, handle that and return -EFAULT.
   */

  long copy_from_user_nofault(void *dst, const void __user *src, size_t size)

  {
  	long ret = -EFAULT;

  	mm_segment_t old_fs = force_uaccess_begin();

  	if (access_ok(src, size)) {
  		pagefault_disable();
  		ret = __copy_from_user_inatomic(dst, src, size);
  		pagefault_enable();
  	}

  	force_uaccess_end(old_fs);

  
  	if (ret)
  		return -EFAULT;
  	return 0;
  }

  EXPORT_SYMBOL_GPL(copy_from_user_nofault);

  
  /**

   * copy_to_user_nofault(): safely attempt to write to a user-space location

   * @dst: address to write to
   * @src: pointer to the data that shall be written
   * @size: size of the data chunk
   *
   * Safely write to address @dst from the buffer at @src.  If a kernel fault
   * happens, handle that and return -EFAULT.
   */

  long copy_to_user_nofault(void __user *dst, const void *src, size_t size)

  {
  	long ret = -EFAULT;

  	mm_segment_t old_fs = force_uaccess_begin();

  	if (access_ok(dst, size)) {
  		pagefault_disable();
  		ret = __copy_to_user_inatomic(dst, src, size);
  		pagefault_enable();
  	}

  	force_uaccess_end(old_fs);

  
  	if (ret)
  		return -EFAULT;
  	return 0;
  }

  EXPORT_SYMBOL_GPL(copy_to_user_nofault);

  
  /**

   * strncpy_from_user_nofault: - Copy a NUL terminated string from unsafe user

   *				address.
   * @dst:   Destination address, in kernel space.  This buffer must be at
   *         least @count bytes long.
   * @unsafe_addr: Unsafe user address.
   * @count: Maximum number of bytes to copy, including the trailing NUL.
   *
   * Copies a NUL-terminated string from unsafe user address to kernel buffer.
   *
   * On success, returns the length of the string INCLUDING the trailing NUL.
   *
   * If access fails, returns -EFAULT (some data may have been copied
   * and the trailing NUL added).
   *
   * If @count is smaller than the length of the string, copies @count-1 bytes,
   * sets the last byte of @dst buffer to NUL and returns @count.
   */

  long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,

  			      long count)
  {

  	mm_segment_t old_fs;

  	long ret;
  
  	if (unlikely(count <= 0))
  		return 0;

  	old_fs = force_uaccess_begin();

  	pagefault_disable();
  	ret = strncpy_from_user(dst, unsafe_addr, count);
  	pagefault_enable();

  	force_uaccess_end(old_fs);

  
  	if (ret >= count) {
  		ret = count;
  		dst[ret - 1] = '\0';
  	} else if (ret > 0) {
  		ret++;
  	}
  
  	return ret;
  }
  
  /**

   * strnlen_user_nofault: - Get the size of a user string INCLUDING final NUL.

   * @unsafe_addr: The string to measure.
   * @count: Maximum count (including NUL)
   *
   * Get the size of a NUL-terminated string in user space without pagefault.
   *
   * Returns the size of the string INCLUDING the terminating NUL.
   *
   * If the string is too long, returns a number larger than @count. User
   * has to check the return value against "> count".
   * On exception (or invalid count), returns 0.
   *
   * Unlike strnlen_user, this can be used from IRQ handler etc. because
   * it disables pagefaults.
   */

  long strnlen_user_nofault(const void __user *unsafe_addr, long count)

  {

  	mm_segment_t old_fs;

  	int ret;

  	old_fs = force_uaccess_begin();

  	pagefault_disable();
  	ret = strnlen_user(unsafe_addr, count);
  	pagefault_enable();

  	force_uaccess_end(old_fs);

  
  	return ret;
  }