linux/mm/maccess.c

// 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>
#include <asm/tlb.h>

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

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

long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
{ … }
EXPORT_SYMBOL_GPL(…);

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

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

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

/**
 * 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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * 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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * 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)
{ … }

/**
 * 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)
{ … }

void __copy_overflow(int size, unsigned long count)
{ … }
EXPORT_SYMBOL(…);