1// SPDX-License-Identifier: GPL-2.0
2// Author: Kirill Smelkov (kirr@nexedi.com)
3//
4// Search for stream-like files that are using nonseekable_open and convert
5// them to stream_open. A stream-like file is a file that does not use ppos in
6// its read and write. Rationale for the conversion is to avoid deadlock in
7// between read and write.
8
9virtual report
10virtual patch
11virtual explain  // explain decisions in the patch (SPFLAGS="-D explain")
12
13// stream-like reader & writer - ones that do not depend on f_pos.
14@ stream_reader @
15identifier readstream, ppos;
16identifier f, buf, len;
17type loff_t;
18@@
19  ssize_t readstream(struct file *f, char *buf, size_t len, loff_t *ppos)
20  {
21    ... when != ppos
22  }
23
24@ stream_writer @
25identifier writestream, ppos;
26identifier f, buf, len;
27type loff_t;
28@@
29  ssize_t writestream(struct file *f, const char *buf, size_t len, loff_t *ppos)
30  {
31    ... when != ppos
32  }
33
34
35// a function that blocks
36@ blocks @
37identifier block_f;
38identifier wait =~ "^wait_.*";
39@@
40  block_f(...) {
41    ... when exists
42    wait(...)
43    ... when exists
44  }
45
46// stream_reader that can block inside.
47//
48// XXX wait_* can be called not directly from current function (e.g. func -> f -> g -> wait())
49// XXX currently reader_blocks supports only direct and 1-level indirect cases.
50@ reader_blocks_direct @
51identifier stream_reader.readstream;
52identifier wait =~ "^wait_.*";
53@@
54  readstream(...)
55  {
56    ... when exists
57    wait(...)
58    ... when exists
59  }
60
61@ reader_blocks_1 @
62identifier stream_reader.readstream;
63identifier blocks.block_f;
64@@
65  readstream(...)
66  {
67    ... when exists
68    block_f(...)
69    ... when exists
70  }
71
72@ reader_blocks depends on reader_blocks_direct || reader_blocks_1 @
73identifier stream_reader.readstream;
74@@
75  readstream(...) {
76    ...
77  }
78
79
80// file_operations + whether they have _any_ .read, .write, .llseek ... at all.
81//
82// XXX add support for file_operations xxx[N] = ...	(sound/core/pcm_native.c)
83@ fops0 @
84identifier fops;
85@@
86  struct file_operations fops = {
87    ...
88  };
89
90@ has_read @
91identifier fops0.fops;
92identifier read_f;
93@@
94  struct file_operations fops = {
95    .read = read_f,
96  };
97
98@ has_read_iter @
99identifier fops0.fops;
100identifier read_iter_f;
101@@
102  struct file_operations fops = {
103    .read_iter = read_iter_f,
104  };
105
106@ has_write @
107identifier fops0.fops;
108identifier write_f;
109@@
110  struct file_operations fops = {
111    .write = write_f,
112  };
113
114@ has_write_iter @
115identifier fops0.fops;
116identifier write_iter_f;
117@@
118  struct file_operations fops = {
119    .write_iter = write_iter_f,
120  };
121
122@ has_llseek @
123identifier fops0.fops;
124identifier llseek_f;
125@@
126  struct file_operations fops = {
127    .llseek = llseek_f,
128  };
129
130@ has_no_llseek @
131identifier fops0.fops;
132@@
133  struct file_operations fops = {
134    .llseek = no_llseek,
135  };
136
137@ has_noop_llseek @
138identifier fops0.fops;
139@@
140  struct file_operations fops = {
141    .llseek = noop_llseek,
142  };
143
144@ has_mmap @
145identifier fops0.fops;
146identifier mmap_f;
147@@
148  struct file_operations fops = {
149    .mmap = mmap_f,
150  };
151
152@ has_copy_file_range @
153identifier fops0.fops;
154identifier copy_file_range_f;
155@@
156  struct file_operations fops = {
157    .copy_file_range = copy_file_range_f,
158  };
159
160@ has_remap_file_range @
161identifier fops0.fops;
162identifier remap_file_range_f;
163@@
164  struct file_operations fops = {
165    .remap_file_range = remap_file_range_f,
166  };
167
168@ has_splice_read @
169identifier fops0.fops;
170identifier splice_read_f;
171@@
172  struct file_operations fops = {
173    .splice_read = splice_read_f,
174  };
175
176@ has_splice_write @
177identifier fops0.fops;
178identifier splice_write_f;
179@@
180  struct file_operations fops = {
181    .splice_write = splice_write_f,
182  };
183
184
185// file_operations that is candidate for stream_open conversion - it does not
186// use mmap and other methods that assume @offset access to file.
187//
188// XXX for simplicity require no .{read/write}_iter and no .splice_{read/write} for now.
189// XXX maybe_steam.fops cannot be used in other rules - it gives "bad rule maybe_stream or bad variable fops".
190@ maybe_stream depends on (!has_llseek || has_no_llseek || has_noop_llseek) && !has_mmap && !has_copy_file_range && !has_remap_file_range && !has_read_iter && !has_write_iter && !has_splice_read && !has_splice_write @
191identifier fops0.fops;
192@@
193  struct file_operations fops = {
194  };
195
196
197// ---- conversions ----
198
199// XXX .open = nonseekable_open -> .open = stream_open
200// XXX .open = func -> openfunc -> nonseekable_open
201
202// read & write
203//
204// if both are used in the same file_operations together with an opener -
205// under that conditions we can use stream_open instead of nonseekable_open.
206@ fops_rw depends on maybe_stream @
207identifier fops0.fops, openfunc;
208identifier stream_reader.readstream;
209identifier stream_writer.writestream;
210@@
211  struct file_operations fops = {
212      .open  = openfunc,
213      .read  = readstream,
214      .write = writestream,
215  };
216
217@ report_rw depends on report @
218identifier fops_rw.openfunc;
219position p1;
220@@
221  openfunc(...) {
222    <...
223     nonseekable_open@p1
224    ...>
225  }
226
227@ script:python depends on report && reader_blocks @
228fops << fops0.fops;
229p << report_rw.p1;
230@@
231coccilib.report.print_report(p[0],
232  "ERROR: %s: .read() can deadlock .write(); change nonseekable_open -> stream_open to fix." % (fops,))
233
234@ script:python depends on report && !reader_blocks @
235fops << fops0.fops;
236p << report_rw.p1;
237@@
238coccilib.report.print_report(p[0],
239  "WARNING: %s: .read() and .write() have stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
240
241
242@ explain_rw_deadlocked depends on explain && reader_blocks @
243identifier fops_rw.openfunc;
244@@
245  openfunc(...) {
246    <...
247-    nonseekable_open
248+    nonseekable_open /* read & write (was deadlock) */
249    ...>
250  }
251
252
253@ explain_rw_nodeadlock depends on explain && !reader_blocks @
254identifier fops_rw.openfunc;
255@@
256  openfunc(...) {
257    <...
258-    nonseekable_open
259+    nonseekable_open /* read & write (no direct deadlock) */
260    ...>
261  }
262
263@ patch_rw depends on patch @
264identifier fops_rw.openfunc;
265@@
266  openfunc(...) {
267    <...
268-   nonseekable_open
269+   stream_open
270    ...>
271  }
272
273
274// read, but not write
275@ fops_r depends on maybe_stream && !has_write @
276identifier fops0.fops, openfunc;
277identifier stream_reader.readstream;
278@@
279  struct file_operations fops = {
280      .open  = openfunc,
281      .read  = readstream,
282  };
283
284@ report_r depends on report @
285identifier fops_r.openfunc;
286position p1;
287@@
288  openfunc(...) {
289    <...
290    nonseekable_open@p1
291    ...>
292  }
293
294@ script:python depends on report @
295fops << fops0.fops;
296p << report_r.p1;
297@@
298coccilib.report.print_report(p[0],
299  "WARNING: %s: .read() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
300
301@ explain_r depends on explain @
302identifier fops_r.openfunc;
303@@
304  openfunc(...) {
305    <...
306-   nonseekable_open
307+   nonseekable_open /* read only */
308    ...>
309  }
310
311@ patch_r depends on patch @
312identifier fops_r.openfunc;
313@@
314  openfunc(...) {
315    <...
316-   nonseekable_open
317+   stream_open
318    ...>
319  }
320
321
322// write, but not read
323@ fops_w depends on maybe_stream && !has_read @
324identifier fops0.fops, openfunc;
325identifier stream_writer.writestream;
326@@
327  struct file_operations fops = {
328      .open  = openfunc,
329      .write = writestream,
330  };
331
332@ report_w depends on report @
333identifier fops_w.openfunc;
334position p1;
335@@
336  openfunc(...) {
337    <...
338    nonseekable_open@p1
339    ...>
340  }
341
342@ script:python depends on report @
343fops << fops0.fops;
344p << report_w.p1;
345@@
346coccilib.report.print_report(p[0],
347  "WARNING: %s: .write() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
348
349@ explain_w depends on explain @
350identifier fops_w.openfunc;
351@@
352  openfunc(...) {
353    <...
354-   nonseekable_open
355+   nonseekable_open /* write only */
356    ...>
357  }
358
359@ patch_w depends on patch @
360identifier fops_w.openfunc;
361@@
362  openfunc(...) {
363    <...
364-   nonseekable_open
365+   stream_open
366    ...>
367  }
368
369
370// no read, no write - don't change anything
371