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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Wrapper functions for accessing the file_struct fd array.
4 */
5
6#ifndef __LINUX_FILE_H
7#define __LINUX_FILE_H
8
9#include <linux/compiler.h>
10#include <linux/types.h>
11#include <linux/posix_types.h>
12#include <linux/errno.h>
13#include <linux/cleanup.h>
14#include <linux/err.h>
15
16struct file;
17
18extern void fput(struct file *);
19
20struct file_operations;
21struct task_struct;
22struct vfsmount;
23struct dentry;
24struct inode;
25struct path;
26extern struct file *alloc_file_pseudo(struct inode *, struct vfsmount *,
27 const char *, int flags, const struct file_operations *);
28extern struct file *alloc_file_pseudo_noaccount(struct inode *, struct vfsmount *,
29 const char *, int flags, const struct file_operations *);
30extern struct file *alloc_file_clone(struct file *, int flags,
31 const struct file_operations *);
32
33/* either a reference to struct file + flags
34 * (cloned vs. borrowed, pos locked), with
35 * flags stored in lower bits of value,
36 * or empty (represented by 0).
37 */
38struct fd {
39 unsigned long word;
40};
41#define FDPUT_FPUT 1
42#define FDPUT_POS_UNLOCK 2
43
44#define fd_file(f) ((struct file *)((f).word & ~(FDPUT_FPUT|FDPUT_POS_UNLOCK)))
45static inline bool fd_empty(struct fd f)
46{
47 return unlikely(!f.word);
48}
49
50#define EMPTY_FD (struct fd){0}
51static inline struct fd BORROWED_FD(struct file *f)
52{
53 return (struct fd){(unsigned long)f};
54}
55static inline struct fd CLONED_FD(struct file *f)
56{
57 return (struct fd){(unsigned long)f | FDPUT_FPUT};
58}
59
60static inline void fdput(struct fd fd)
61{
62 if (unlikely(fd.word & FDPUT_FPUT))
63 fput(fd_file(fd));
64}
65
66extern struct file *fget(unsigned int fd);
67extern struct file *fget_raw(unsigned int fd);
68extern struct file *fget_task(struct task_struct *task, unsigned int fd);
69extern struct file *fget_task_next(struct task_struct *task, unsigned int *fd);
70extern void __f_unlock_pos(struct file *);
71
72struct fd fdget(unsigned int fd);
73struct fd fdget_raw(unsigned int fd);
74struct fd fdget_pos(unsigned int fd);
75
76static inline void fdput_pos(struct fd f)
77{
78 if (f.word & FDPUT_POS_UNLOCK)
79 __f_unlock_pos(fd_file(f));
80 fdput(fd: f);
81}
82
83DEFINE_CLASS(fd, struct fd, fdput(_T), fdget(fd), int fd)
84DEFINE_CLASS(fd_raw, struct fd, fdput(_T), fdget_raw(fd), int fd)
85DEFINE_CLASS(fd_pos, struct fd, fdput_pos(_T), fdget_pos(fd), int fd)
86
87extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);
88extern int replace_fd(unsigned fd, struct file *file, unsigned flags);
89extern void set_close_on_exec(unsigned int fd, int flag);
90extern bool get_close_on_exec(unsigned int fd);
91extern int __get_unused_fd_flags(unsigned flags, unsigned long nofile);
92extern int get_unused_fd_flags(unsigned flags);
93extern void put_unused_fd(unsigned int fd);
94
95DEFINE_CLASS(get_unused_fd, int, if (_T >= 0) put_unused_fd(_T),
96 get_unused_fd_flags(flags), unsigned flags)
97DEFINE_FREE(fput, struct file *, if (!IS_ERR_OR_NULL(_T)) fput(_T))
98
99/*
100 * take_fd() will take care to set @fd to -EBADF ensuring that
101 * CLASS(get_unused_fd) won't call put_unused_fd(). This makes it
102 * easier to rely on CLASS(get_unused_fd):
103 *
104 * struct file *f;
105 *
106 * CLASS(get_unused_fd, fd)(O_CLOEXEC);
107 * if (fd < 0)
108 * return fd;
109 *
110 * f = dentry_open(&path, O_RDONLY, current_cred());
111 * if (IS_ERR(f))
112 * return PTR_ERR(f);
113 *
114 * fd_install(fd, f);
115 * return take_fd(fd);
116 */
117#define take_fd(fd) __get_and_null(fd, -EBADF)
118
119extern void fd_install(unsigned int fd, struct file *file);
120
121int receive_fd(struct file *file, int __user *ufd, unsigned int o_flags);
122
123int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags);
124
125extern void flush_delayed_fput(void);
126extern void __fput_sync(struct file *);
127
128extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max;
129
130/*
131 * fd_prepare: Combined fd + file allocation cleanup class.
132 * @err: Error code to indicate if allocation succeeded.
133 * @__fd: Allocated fd (may not be accessed directly)
134 * @__file: Allocated struct file pointer (may not be accessed directly)
135 *
136 * Allocates an fd and a file together. On error paths, automatically cleans
137 * up whichever resource was successfully allocated. Allows flexible file
138 * allocation with different functions per usage.
139 *
140 * Do not use directly.
141 */
142struct fd_prepare {
143 s32 err;
144 s32 __fd; /* do not access directly */
145 struct file *__file; /* do not access directly */
146};
147
148/* Typedef for fd_prepare cleanup guards. */
149typedef struct fd_prepare class_fd_prepare_t;
150
151/*
152 * Accessors for fd_prepare class members.
153 * _Generic() is used for zero-cost type safety.
154 */
155#define fd_prepare_fd(_fdf) \
156 (_Generic((_fdf), struct fd_prepare: (_fdf).__fd))
157
158#define fd_prepare_file(_fdf) \
159 (_Generic((_fdf), struct fd_prepare: (_fdf).__file))
160
161/* Do not use directly. */
162static inline void class_fd_prepare_destructor(const struct fd_prepare *fdf)
163{
164 if (unlikely(fdf->__fd >= 0))
165 put_unused_fd(fd: fdf->__fd);
166 if (unlikely(!IS_ERR_OR_NULL(fdf->__file)))
167 fput(fdf->__file);
168}
169
170/* Do not use directly. */
171static inline int class_fd_prepare_lock_err(const struct fd_prepare *fdf)
172{
173 if (unlikely(fdf->err))
174 return fdf->err;
175 if (unlikely(fdf->__fd < 0))
176 return fdf->__fd;
177 if (unlikely(IS_ERR(fdf->__file)))
178 return PTR_ERR(ptr: fdf->__file);
179 if (unlikely(!fdf->__file))
180 return -ENOMEM;
181 return 0;
182}
183
184/*
185 * __FD_PREPARE_INIT - Helper to initialize fd_prepare class.
186 * @_fd_flags: flags for get_unused_fd_flags()
187 * @_file_owned: expression that returns struct file *
188 *
189 * Returns a struct fd_prepare with fd, file, and err set.
190 * If fd allocation fails, fd will be negative and err will be set. If
191 * fd succeeds but file_init_expr fails, file will be ERR_PTR and err
192 * will be set. The err field is the single source of truth for error
193 * checking.
194 */
195#define __FD_PREPARE_INIT(_fd_flags, _file_owned) \
196 ({ \
197 struct fd_prepare fdf = { \
198 .__fd = get_unused_fd_flags((_fd_flags)), \
199 }; \
200 if (likely(fdf.__fd >= 0)) \
201 fdf.__file = (_file_owned); \
202 fdf.err = ACQUIRE_ERR(fd_prepare, &fdf); \
203 fdf; \
204 })
205
206/*
207 * FD_PREPARE - Macro to declare and initialize an fd_prepare variable.
208 *
209 * Declares and initializes an fd_prepare variable with automatic
210 * cleanup. No separate scope required - cleanup happens when variable
211 * goes out of scope.
212 *
213 * @_fdf: name of struct fd_prepare variable to define
214 * @_fd_flags: flags for get_unused_fd_flags()
215 * @_file_owned: struct file to take ownership of (can be expression)
216 */
217#define FD_PREPARE(_fdf, _fd_flags, _file_owned) \
218 CLASS_INIT(fd_prepare, _fdf, __FD_PREPARE_INIT(_fd_flags, _file_owned))
219
220/*
221 * fd_publish - Publish prepared fd and file to the fd table.
222 * @_fdf: struct fd_prepare variable
223 */
224#define fd_publish(_fdf) \
225 ({ \
226 struct fd_prepare *fdp = &(_fdf); \
227 VFS_WARN_ON_ONCE(fdp->err); \
228 VFS_WARN_ON_ONCE(fdp->__fd < 0); \
229 VFS_WARN_ON_ONCE(IS_ERR_OR_NULL(fdp->__file)); \
230 fd_install(fdp->__fd, fdp->__file); \
231 retain_and_null_ptr(fdp->__file); \
232 take_fd(fdp->__fd); \
233 })
234
235/* Do not use directly. */
236#define __FD_ADD(_fdf, _fd_flags, _file_owned) \
237 ({ \
238 FD_PREPARE(_fdf, _fd_flags, _file_owned); \
239 s32 ret = _fdf.err; \
240 if (likely(!ret)) \
241 ret = fd_publish(_fdf); \
242 ret; \
243 })
244
245/*
246 * FD_ADD - Allocate and install an fd and file in one step.
247 * @_fd_flags: flags for get_unused_fd_flags()
248 * @_file_owned: struct file to take ownership of
249 *
250 * Returns the allocated fd number, or negative error code on failure.
251 */
252#define FD_ADD(_fd_flags, _file_owned) \
253 __FD_ADD(__UNIQUE_ID(fd_prepare), _fd_flags, _file_owned)
254
255#endif /* __LINUX_FILE_H */
256

source code of linux/include/linux/file.h