linux/fs/kernel_read_file.c

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/fs.h>
#include <linux/fs_struct.h>
#include <linux/kernel_read_file.h>
#include <linux/security.h>
#include <linux/vmalloc.h>

/**
 * kernel_read_file() - read file contents into a kernel buffer
 *
 * @file:	file to read from
 * @offset:	where to start reading from (see below).
 * @buf:	pointer to a "void *" buffer for reading into (if
 *		*@buf is NULL, a buffer will be allocated, and
 *		@buf_size will be ignored)
 * @buf_size:	size of buf, if already allocated. If @buf not
 *		allocated, this is the largest size to allocate.
 * @file_size:	if non-NULL, the full size of @file will be
 *		written here.
 * @id:		the kernel_read_file_id identifying the type of
 *		file contents being read (for LSMs to examine)
 *
 * @offset must be 0 unless both @buf and @file_size are non-NULL
 * (i.e. the caller must be expecting to read partial file contents
 * via an already-allocated @buf, in at most @buf_size chunks, and
 * will be able to determine when the entire file was read by
 * checking @file_size). This isn't a recommended way to read a
 * file, though, since it is possible that the contents might
 * change between calls to kernel_read_file().
 *
 * Returns number of bytes read (no single read will be bigger
 * than SSIZE_MAX), or negative on error.
 *
 */
ssize_t kernel_read_file(struct file *file, loff_t offset, void **buf,
			 size_t buf_size, size_t *file_size,
			 enum kernel_read_file_id id)
{ … }
EXPORT_SYMBOL_GPL(…);

ssize_t kernel_read_file_from_path(const char *path, loff_t offset, void **buf,
				   size_t buf_size, size_t *file_size,
				   enum kernel_read_file_id id)
{ … }
EXPORT_SYMBOL_GPL(…);

ssize_t kernel_read_file_from_path_initns(const char *path, loff_t offset,
					  void **buf, size_t buf_size,
					  size_t *file_size,
					  enum kernel_read_file_id id)
{ … }
EXPORT_SYMBOL_GPL(…);

ssize_t kernel_read_file_from_fd(int fd, loff_t offset, void **buf,
				 size_t buf_size, size_t *file_size,
				 enum kernel_read_file_id id)
{ … }
EXPORT_SYMBOL_GPL(…);