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bpf: Add task and task/file iterator targets

Only the tasks belonging to "current" pid namespace are enumerated. For task/file target, the bpf program will have access to struct task_struct *task u32 fd struct file *file where fd/file is an open file for the task.

Yonghong Song committed 6 years ago

Commit eaaacd21 parent 138d0be2 files · +334 −1Browse files

Unified · Split

2 files
  1. kernel/bpf/Makefile +1 −1
  2. kernel/bpf/task_iter.c +333 −0
kernel/bpf/Makefile+1−1
@@ -2,7 +2,7 @@ · 1 unmodified line
2obj-y := core.o2obj-y := core.o
3CFLAGS_core.o += $(call cc-disable-warning, override-init)3CFLAGS_core.o += $(call cc-disable-warning, override-init)
4 4
5obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o5obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o
6obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o6obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
7obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o7obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o
8obj-$(CONFIG_BPF_SYSCALL) += disasm.o8obj-$(CONFIG_BPF_SYSCALL) += disasm.o
kernel/bpf/task_iter.c+333−0
@@ -0,0 +1,333 @@
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
11struct bpf_iter_seq_task_common {
12 struct pid_namespace *ns;
13};
14
15struct bpf_iter_seq_task_info {
16 /* The first field must be struct bpf_iter_seq_task_common.
17 * this is assumed by {init, fini}_seq_pidns() callback functions.
18 */
19 struct bpf_iter_seq_task_common common;
20 u32 tid;
21};
22
23static struct task_struct *task_seq_get_next(struct pid_namespace *ns,
24 u32 *tid)
25{
26 struct task_struct *task = NULL;
27 struct pid *pid;
28
29 rcu_read_lock();
30 pid = idr_get_next(&ns->idr, tid);
31 if (pid)
32 task = get_pid_task(pid, PIDTYPE_PID);
33 rcu_read_unlock();
34
35 return task;
36}
37
38static void *task_seq_start(struct seq_file *seq, loff_t *pos)
39{
40 struct bpf_iter_seq_task_info *info = seq->private;
41 struct task_struct *task;
42
43 task = task_seq_get_next(info->common.ns, &info->tid);
44 if (!task)
45 return NULL;
46
47 ++*pos;
48 return task;
49}
50
51static void *task_seq_next(struct seq_file *seq, void *v, loff_t *pos)
52{
53 struct bpf_iter_seq_task_info *info = seq->private;
54 struct task_struct *task;
55
56 ++*pos;
57 ++info->tid;
58 put_task_struct((struct task_struct *)v);
59 task = task_seq_get_next(info->common.ns, &info->tid);
60 if (!task)
61 return NULL;
62
63 return task;
64}
65
66struct bpf_iter__task {
67 __bpf_md_ptr(struct bpf_iter_meta *, meta);
68 __bpf_md_ptr(struct task_struct *, task);
69};
70
71DEFINE_BPF_ITER_FUNC(task, struct bpf_iter_meta *meta, struct task_struct *task)
72
73static int __task_seq_show(struct seq_file *seq, struct task_struct *task,
74 bool in_stop)
75{
76 struct bpf_iter_meta meta;
77 struct bpf_iter__task ctx;
78 struct bpf_prog *prog;
79
80 meta.seq = seq;
81 prog = bpf_iter_get_info(&meta, in_stop);
82 if (!prog)
83 return 0;
84
85 meta.seq = seq;
86 ctx.meta = &meta;
87 ctx.task = task;
88 return bpf_iter_run_prog(prog, &ctx);
89}
90
91static int task_seq_show(struct seq_file *seq, void *v)
92{
93 return __task_seq_show(seq, v, false);
94}
95
96static void task_seq_stop(struct seq_file *seq, void *v)
97{
98 if (!v)
99 (void)__task_seq_show(seq, v, true);
100 else
101 put_task_struct((struct task_struct *)v);
102}
103
104static const struct seq_operations task_seq_ops = {
105 .start = task_seq_start,
106 .next = task_seq_next,
107 .stop = task_seq_stop,
108 .show = task_seq_show,
109};
110
111struct bpf_iter_seq_task_file_info {
112 /* The first field must be struct bpf_iter_seq_task_common.
113 * this is assumed by {init, fini}_seq_pidns() callback functions.
114 */
115 struct bpf_iter_seq_task_common common;
116 struct task_struct *task;
117 struct files_struct *files;
118 u32 tid;
119 u32 fd;
120};
121
122static struct file *
123task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info,
124 struct task_struct **task, struct files_struct **fstruct)
125{
126 struct pid_namespace *ns = info->common.ns;
127 u32 curr_tid = info->tid, max_fds;
128 struct files_struct *curr_files;
129 struct task_struct *curr_task;
130 int curr_fd = info->fd;
131
132 /* If this function returns a non-NULL file object,
133 * it held a reference to the task/files_struct/file.
134 * Otherwise, it does not hold any reference.
135 */
136again:
137 if (*task) {
138 curr_task = *task;
139 curr_files = *fstruct;
140 curr_fd = info->fd;
141 } else {
142 curr_task = task_seq_get_next(ns, &curr_tid);
143 if (!curr_task)
144 return NULL;
145
146 curr_files = get_files_struct(curr_task);
147 if (!curr_files) {
148 put_task_struct(curr_task);
149 curr_tid = ++(info->tid);
150 info->fd = 0;
151 goto again;
152 }
153
154 /* set *fstruct, *task and info->tid */
155 *fstruct = curr_files;
156 *task = curr_task;
157 if (curr_tid == info->tid) {
158 curr_fd = info->fd;
159 } else {
160 info->tid = curr_tid;
161 curr_fd = 0;
162 }
163 }
164
165 rcu_read_lock();
166 max_fds = files_fdtable(curr_files)->max_fds;
167 for (; curr_fd < max_fds; curr_fd++) {
168 struct file *f;
169
170 f = fcheck_files(curr_files, curr_fd);
171 if (!f)
172 continue;
173
174 /* set info->fd */
175 info->fd = curr_fd;
176 get_file(f);
177 rcu_read_unlock();
178 return f;
179 }
180
181 /* the current task is done, go to the next task */
182 rcu_read_unlock();
183 put_files_struct(curr_files);
184 put_task_struct(curr_task);
185 *task = NULL;
186 *fstruct = NULL;
187 info->fd = 0;
188 curr_tid = ++(info->tid);
189 goto again;
190}
191
192static void *task_file_seq_start(struct seq_file *seq, loff_t *pos)
193{
194 struct bpf_iter_seq_task_file_info *info = seq->private;
195 struct files_struct *files = NULL;
196 struct task_struct *task = NULL;
197 struct file *file;
198
199 file = task_file_seq_get_next(info, &task, &files);
200 if (!file) {
201 info->files = NULL;
202 info->task = NULL;
203 return NULL;
204 }
205
206 ++*pos;
207 info->task = task;
208 info->files = files;
209
210 return file;
211}
212
213static void *task_file_seq_next(struct seq_file *seq, void *v, loff_t *pos)
214{
215 struct bpf_iter_seq_task_file_info *info = seq->private;
216 struct files_struct *files = info->files;
217 struct task_struct *task = info->task;
218 struct file *file;
219
220 ++*pos;
221 ++info->fd;
222 fput((struct file *)v);
223 file = task_file_seq_get_next(info, &task, &files);
224 if (!file) {
225 info->files = NULL;
226 info->task = NULL;
227 return NULL;
228 }
229
230 info->task = task;
231 info->files = files;
232
233 return file;
234}
235
236struct bpf_iter__task_file {
237 __bpf_md_ptr(struct bpf_iter_meta *, meta);
238 __bpf_md_ptr(struct task_struct *, task);
239 u32 fd __aligned(8);
240 __bpf_md_ptr(struct file *, file);
241};
242
243DEFINE_BPF_ITER_FUNC(task_file, struct bpf_iter_meta *meta,
244 struct task_struct *task, u32 fd,
245 struct file *file)
246
247static int __task_file_seq_show(struct seq_file *seq, struct file *file,
248 bool in_stop)
249{
250 struct bpf_iter_seq_task_file_info *info = seq->private;
251 struct bpf_iter__task_file ctx;
252 struct bpf_iter_meta meta;
253 struct bpf_prog *prog;
254
255 meta.seq = seq;
256 prog = bpf_iter_get_info(&meta, in_stop);
257 if (!prog)
258 return 0;
259
260 ctx.meta = &meta;
261 ctx.task = info->task;
262 ctx.fd = info->fd;
263 ctx.file = file;
264 return bpf_iter_run_prog(prog, &ctx);
265}
266
267static int task_file_seq_show(struct seq_file *seq, void *v)
268{
269 return __task_file_seq_show(seq, v, false);
270}
271
272static void task_file_seq_stop(struct seq_file *seq, void *v)
273{
274 struct bpf_iter_seq_task_file_info *info = seq->private;
275
276 if (!v) {
277 (void)__task_file_seq_show(seq, v, true);
278 } else {
279 fput((struct file *)v);
280 put_files_struct(info->files);
281 put_task_struct(info->task);
282 info->files = NULL;
283 info->task = NULL;
284 }
285}
286
287static int init_seq_pidns(void *priv_data)
288{
289 struct bpf_iter_seq_task_common *common = priv_data;
290
291 common->ns = get_pid_ns(task_active_pid_ns(current));
292 return 0;
293}
294
295static void fini_seq_pidns(void *priv_data)
296{
297 struct bpf_iter_seq_task_common *common = priv_data;
298
299 put_pid_ns(common->ns);
300}
301
302static const struct seq_operations task_file_seq_ops = {
303 .start = task_file_seq_start,
304 .next = task_file_seq_next,
305 .stop = task_file_seq_stop,
306 .show = task_file_seq_show,
307};
308
309static int __init task_iter_init(void)
310{
311 struct bpf_iter_reg task_file_reg_info = {
312 .target = "task_file",
313 .seq_ops = &task_file_seq_ops,
314 .init_seq_private = init_seq_pidns,
315 .fini_seq_private = fini_seq_pidns,
316 .seq_priv_size = sizeof(struct bpf_iter_seq_task_file_info),
317 };
318 struct bpf_iter_reg task_reg_info = {
319 .target = "task",
320 .seq_ops = &task_seq_ops,
321 .init_seq_private = init_seq_pidns,
322 .fini_seq_private = fini_seq_pidns,
323 .seq_priv_size = sizeof(struct bpf_iter_seq_task_info),
324 };
325 int ret;
326
327 ret = bpf_iter_reg_target(&task_reg_info);
328 if (ret)
329 return ret;
330
331 return bpf_iter_reg_target(&task_file_reg_info);
332}
333late_initcall(task_iter_init);