xref: /openbmc/linux/kernel/bpf/task_iter.c (revision 0b26ca68)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (c) 2020 Facebook */
3 
4 #include <linux/init.h>
5 #include <linux/namei.h>
6 #include <linux/pid_namespace.h>
7 #include <linux/fs.h>
8 #include <linux/fdtable.h>
9 #include <linux/filter.h>
10 #include <linux/btf_ids.h>
11 
12 struct bpf_iter_seq_task_common {
13 	struct pid_namespace *ns;
14 };
15 
16 struct bpf_iter_seq_task_info {
17 	/* The first field must be struct bpf_iter_seq_task_common.
18 	 * this is assumed by {init, fini}_seq_pidns() callback functions.
19 	 */
20 	struct bpf_iter_seq_task_common common;
21 	u32 tid;
22 };
23 
24 static struct task_struct *task_seq_get_next(struct pid_namespace *ns,
25 					     u32 *tid,
26 					     bool skip_if_dup_files)
27 {
28 	struct task_struct *task = NULL;
29 	struct pid *pid;
30 
31 	rcu_read_lock();
32 retry:
33 	pid = find_ge_pid(*tid, ns);
34 	if (pid) {
35 		*tid = pid_nr_ns(pid, ns);
36 		task = get_pid_task(pid, PIDTYPE_PID);
37 		if (!task) {
38 			++*tid;
39 			goto retry;
40 		} else if (skip_if_dup_files && !thread_group_leader(task) &&
41 			   task->files == task->group_leader->files) {
42 			put_task_struct(task);
43 			task = NULL;
44 			++*tid;
45 			goto retry;
46 		}
47 	}
48 	rcu_read_unlock();
49 
50 	return task;
51 }
52 
53 static void *task_seq_start(struct seq_file *seq, loff_t *pos)
54 {
55 	struct bpf_iter_seq_task_info *info = seq->private;
56 	struct task_struct *task;
57 
58 	task = task_seq_get_next(info->common.ns, &info->tid, false);
59 	if (!task)
60 		return NULL;
61 
62 	if (*pos == 0)
63 		++*pos;
64 	return task;
65 }
66 
67 static void *task_seq_next(struct seq_file *seq, void *v, loff_t *pos)
68 {
69 	struct bpf_iter_seq_task_info *info = seq->private;
70 	struct task_struct *task;
71 
72 	++*pos;
73 	++info->tid;
74 	put_task_struct((struct task_struct *)v);
75 	task = task_seq_get_next(info->common.ns, &info->tid, false);
76 	if (!task)
77 		return NULL;
78 
79 	return task;
80 }
81 
82 struct bpf_iter__task {
83 	__bpf_md_ptr(struct bpf_iter_meta *, meta);
84 	__bpf_md_ptr(struct task_struct *, task);
85 };
86 
87 DEFINE_BPF_ITER_FUNC(task, struct bpf_iter_meta *meta, struct task_struct *task)
88 
89 static int __task_seq_show(struct seq_file *seq, struct task_struct *task,
90 			   bool in_stop)
91 {
92 	struct bpf_iter_meta meta;
93 	struct bpf_iter__task ctx;
94 	struct bpf_prog *prog;
95 
96 	meta.seq = seq;
97 	prog = bpf_iter_get_info(&meta, in_stop);
98 	if (!prog)
99 		return 0;
100 
101 	meta.seq = seq;
102 	ctx.meta = &meta;
103 	ctx.task = task;
104 	return bpf_iter_run_prog(prog, &ctx);
105 }
106 
107 static int task_seq_show(struct seq_file *seq, void *v)
108 {
109 	return __task_seq_show(seq, v, false);
110 }
111 
112 static void task_seq_stop(struct seq_file *seq, void *v)
113 {
114 	if (!v)
115 		(void)__task_seq_show(seq, v, true);
116 	else
117 		put_task_struct((struct task_struct *)v);
118 }
119 
120 static const struct seq_operations task_seq_ops = {
121 	.start	= task_seq_start,
122 	.next	= task_seq_next,
123 	.stop	= task_seq_stop,
124 	.show	= task_seq_show,
125 };
126 
127 struct bpf_iter_seq_task_file_info {
128 	/* The first field must be struct bpf_iter_seq_task_common.
129 	 * this is assumed by {init, fini}_seq_pidns() callback functions.
130 	 */
131 	struct bpf_iter_seq_task_common common;
132 	struct task_struct *task;
133 	u32 tid;
134 	u32 fd;
135 };
136 
137 static struct file *
138 task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info)
139 {
140 	struct pid_namespace *ns = info->common.ns;
141 	u32 curr_tid = info->tid;
142 	struct task_struct *curr_task;
143 	unsigned int curr_fd = info->fd;
144 
145 	/* If this function returns a non-NULL file object,
146 	 * it held a reference to the task/file.
147 	 * Otherwise, it does not hold any reference.
148 	 */
149 again:
150 	if (info->task) {
151 		curr_task = info->task;
152 		curr_fd = info->fd;
153 	} else {
154                 curr_task = task_seq_get_next(ns, &curr_tid, true);
155                 if (!curr_task) {
156                         info->task = NULL;
157                         info->tid = curr_tid;
158                         return NULL;
159                 }
160 
161                 /* set info->task and info->tid */
162 		info->task = curr_task;
163 		if (curr_tid == info->tid) {
164 			curr_fd = info->fd;
165 		} else {
166 			info->tid = curr_tid;
167 			curr_fd = 0;
168 		}
169 	}
170 
171 	rcu_read_lock();
172 	for (;; curr_fd++) {
173 		struct file *f;
174 		f = task_lookup_next_fd_rcu(curr_task, &curr_fd);
175 		if (!f)
176 			break;
177 		if (!get_file_rcu(f))
178 			continue;
179 
180 		/* set info->fd */
181 		info->fd = curr_fd;
182 		rcu_read_unlock();
183 		return f;
184 	}
185 
186 	/* the current task is done, go to the next task */
187 	rcu_read_unlock();
188 	put_task_struct(curr_task);
189 	info->task = NULL;
190 	info->fd = 0;
191 	curr_tid = ++(info->tid);
192 	goto again;
193 }
194 
195 static void *task_file_seq_start(struct seq_file *seq, loff_t *pos)
196 {
197 	struct bpf_iter_seq_task_file_info *info = seq->private;
198 	struct file *file;
199 
200 	info->task = NULL;
201 	file = task_file_seq_get_next(info);
202 	if (file && *pos == 0)
203 		++*pos;
204 
205 	return file;
206 }
207 
208 static void *task_file_seq_next(struct seq_file *seq, void *v, loff_t *pos)
209 {
210 	struct bpf_iter_seq_task_file_info *info = seq->private;
211 
212 	++*pos;
213 	++info->fd;
214 	fput((struct file *)v);
215 	return task_file_seq_get_next(info);
216 }
217 
218 struct bpf_iter__task_file {
219 	__bpf_md_ptr(struct bpf_iter_meta *, meta);
220 	__bpf_md_ptr(struct task_struct *, task);
221 	u32 fd __aligned(8);
222 	__bpf_md_ptr(struct file *, file);
223 };
224 
225 DEFINE_BPF_ITER_FUNC(task_file, struct bpf_iter_meta *meta,
226 		     struct task_struct *task, u32 fd,
227 		     struct file *file)
228 
229 static int __task_file_seq_show(struct seq_file *seq, struct file *file,
230 				bool in_stop)
231 {
232 	struct bpf_iter_seq_task_file_info *info = seq->private;
233 	struct bpf_iter__task_file ctx;
234 	struct bpf_iter_meta meta;
235 	struct bpf_prog *prog;
236 
237 	meta.seq = seq;
238 	prog = bpf_iter_get_info(&meta, in_stop);
239 	if (!prog)
240 		return 0;
241 
242 	ctx.meta = &meta;
243 	ctx.task = info->task;
244 	ctx.fd = info->fd;
245 	ctx.file = file;
246 	return bpf_iter_run_prog(prog, &ctx);
247 }
248 
249 static int task_file_seq_show(struct seq_file *seq, void *v)
250 {
251 	return __task_file_seq_show(seq, v, false);
252 }
253 
254 static void task_file_seq_stop(struct seq_file *seq, void *v)
255 {
256 	struct bpf_iter_seq_task_file_info *info = seq->private;
257 
258 	if (!v) {
259 		(void)__task_file_seq_show(seq, v, true);
260 	} else {
261 		fput((struct file *)v);
262 		put_task_struct(info->task);
263 		info->task = NULL;
264 	}
265 }
266 
267 static int init_seq_pidns(void *priv_data, struct bpf_iter_aux_info *aux)
268 {
269 	struct bpf_iter_seq_task_common *common = priv_data;
270 
271 	common->ns = get_pid_ns(task_active_pid_ns(current));
272 	return 0;
273 }
274 
275 static void fini_seq_pidns(void *priv_data)
276 {
277 	struct bpf_iter_seq_task_common *common = priv_data;
278 
279 	put_pid_ns(common->ns);
280 }
281 
282 static const struct seq_operations task_file_seq_ops = {
283 	.start	= task_file_seq_start,
284 	.next	= task_file_seq_next,
285 	.stop	= task_file_seq_stop,
286 	.show	= task_file_seq_show,
287 };
288 
289 BTF_ID_LIST(btf_task_file_ids)
290 BTF_ID(struct, task_struct)
291 BTF_ID(struct, file)
292 
293 static const struct bpf_iter_seq_info task_seq_info = {
294 	.seq_ops		= &task_seq_ops,
295 	.init_seq_private	= init_seq_pidns,
296 	.fini_seq_private	= fini_seq_pidns,
297 	.seq_priv_size		= sizeof(struct bpf_iter_seq_task_info),
298 };
299 
300 static struct bpf_iter_reg task_reg_info = {
301 	.target			= "task",
302 	.feature		= BPF_ITER_RESCHED,
303 	.ctx_arg_info_size	= 1,
304 	.ctx_arg_info		= {
305 		{ offsetof(struct bpf_iter__task, task),
306 		  PTR_TO_BTF_ID_OR_NULL },
307 	},
308 	.seq_info		= &task_seq_info,
309 };
310 
311 static const struct bpf_iter_seq_info task_file_seq_info = {
312 	.seq_ops		= &task_file_seq_ops,
313 	.init_seq_private	= init_seq_pidns,
314 	.fini_seq_private	= fini_seq_pidns,
315 	.seq_priv_size		= sizeof(struct bpf_iter_seq_task_file_info),
316 };
317 
318 static struct bpf_iter_reg task_file_reg_info = {
319 	.target			= "task_file",
320 	.feature		= BPF_ITER_RESCHED,
321 	.ctx_arg_info_size	= 2,
322 	.ctx_arg_info		= {
323 		{ offsetof(struct bpf_iter__task_file, task),
324 		  PTR_TO_BTF_ID_OR_NULL },
325 		{ offsetof(struct bpf_iter__task_file, file),
326 		  PTR_TO_BTF_ID_OR_NULL },
327 	},
328 	.seq_info		= &task_file_seq_info,
329 };
330 
331 static int __init task_iter_init(void)
332 {
333 	int ret;
334 
335 	task_reg_info.ctx_arg_info[0].btf_id = btf_task_file_ids[0];
336 	ret = bpf_iter_reg_target(&task_reg_info);
337 	if (ret)
338 		return ret;
339 
340 	task_file_reg_info.ctx_arg_info[0].btf_id = btf_task_file_ids[0];
341 	task_file_reg_info.ctx_arg_info[1].btf_id = btf_task_file_ids[1];
342 	return bpf_iter_reg_target(&task_file_reg_info);
343 }
344 late_initcall(task_iter_init);
345