1/* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com
  2 *
  3 * This program is free software; you can redistribute it and/or
  4 * modify it under the terms of version 2 of the GNU General Public
  5 * License as published by the Free Software Foundation.
  6 */
  7#include <linux/kernel.h>
  8#include <linux/types.h>
  9#include <linux/slab.h>
 10#include <linux/bpf.h>
 11#include <linux/filter.h>
 12#include <linux/uaccess.h>
 13#include <linux/ctype.h>
 14#include "trace.h"
 15
 16/**
 17 * trace_call_bpf - invoke BPF program
 18 * @prog: BPF program
 19 * @ctx: opaque context pointer
 20 *
 21 * kprobe handlers execute BPF programs via this helper.
 22 * Can be used from static tracepoints in the future.
 23 *
 24 * Return: BPF programs always return an integer which is interpreted by
 25 * kprobe handler as:
 26 * 0 - return from kprobe (event is filtered out)
 27 * 1 - store kprobe event into ring buffer
 28 * Other values are reserved and currently alias to 1
 29 */
 30unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
 31{
 32	unsigned int ret;
 33
 34	if (in_nmi()) /* not supported yet */
 35		return 1;
 36
 37	preempt_disable();
 38
 39	if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
 40		/*
 41		 * since some bpf program is already running on this cpu,
 42		 * don't call into another bpf program (same or different)
 43		 * and don't send kprobe event into ring-buffer,
 44		 * so return zero here
 45		 */
 46		ret = 0;
 47		goto out;
 48	}
 49
 50	rcu_read_lock();
 51	ret = BPF_PROG_RUN(prog, ctx);
 52	rcu_read_unlock();
 53
 54 out:
 55	__this_cpu_dec(bpf_prog_active);
 56	preempt_enable();
 57
 58	return ret;
 59}
 60EXPORT_SYMBOL_GPL(trace_call_bpf);
 61
 62static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 63{
 64	void *dst = (void *) (long) r1;
 65	int size = (int) r2;
 66	void *unsafe_ptr = (void *) (long) r3;
 67
 68	return probe_kernel_read(dst, unsafe_ptr, size);
 69}
 70
 71static const struct bpf_func_proto bpf_probe_read_proto = {
 72	.func		= bpf_probe_read,
 73	.gpl_only	= true,
 74	.ret_type	= RET_INTEGER,
 75	.arg1_type	= ARG_PTR_TO_STACK,
 76	.arg2_type	= ARG_CONST_STACK_SIZE,
 77	.arg3_type	= ARG_ANYTHING,
 78};
 79
 80/*
 81 * limited trace_printk()
 82 * only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed
 83 */
 84static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
 85{
 86	char *fmt = (char *) (long) r1;
 87	bool str_seen = false;
 88	int mod[3] = {};
 89	int fmt_cnt = 0;
 90	u64 unsafe_addr;
 91	char buf[64];
 92	int i;
 93
 94	/*
 95	 * bpf_check()->check_func_arg()->check_stack_boundary()
 96	 * guarantees that fmt points to bpf program stack,
 97	 * fmt_size bytes of it were initialized and fmt_size > 0
 98	 */
 99	if (fmt[--fmt_size] != 0)
100		return -EINVAL;
101
102	/* check format string for allowed specifiers */
103	for (i = 0; i < fmt_size; i++) {
104		if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
105			return -EINVAL;
106
107		if (fmt[i] != '%')
108			continue;
109
110		if (fmt_cnt >= 3)
111			return -EINVAL;
112
113		/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
114		i++;
115		if (fmt[i] == 'l') {
116			mod[fmt_cnt]++;
117			i++;
118		} else if (fmt[i] == 'p' || fmt[i] == 's') {
119			mod[fmt_cnt]++;
120			i++;
121			if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
122				return -EINVAL;
123			fmt_cnt++;
124			if (fmt[i - 1] == 's') {
125				if (str_seen)
126					/* allow only one '%s' per fmt string */
127					return -EINVAL;
128				str_seen = true;
129
130				switch (fmt_cnt) {
131				case 1:
132					unsafe_addr = r3;
133					r3 = (long) buf;
134					break;
135				case 2:
136					unsafe_addr = r4;
137					r4 = (long) buf;
138					break;
139				case 3:
140					unsafe_addr = r5;
141					r5 = (long) buf;
142					break;
143				}
144				buf[0] = 0;
145				strncpy_from_unsafe(buf,
146						    (void *) (long) unsafe_addr,
147						    sizeof(buf));
148			}
149			continue;
150		}
151
152		if (fmt[i] == 'l') {
153			mod[fmt_cnt]++;
154			i++;
155		}
156
157		if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
158			return -EINVAL;
159		fmt_cnt++;
160	}
161
162	return __trace_printk(1/* fake ip will not be printed */, fmt,
163			      mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3,
164			      mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4,
165			      mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5);
166}
167
168static const struct bpf_func_proto bpf_trace_printk_proto = {
169	.func		= bpf_trace_printk,
170	.gpl_only	= true,
171	.ret_type	= RET_INTEGER,
172	.arg1_type	= ARG_PTR_TO_STACK,
173	.arg2_type	= ARG_CONST_STACK_SIZE,
174};
175
176const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
177{
178	/*
179	 * this program might be calling bpf_trace_printk,
180	 * so allocate per-cpu printk buffers
181	 */
182	trace_printk_init_buffers();
183
184	return &bpf_trace_printk_proto;
185}
186
187static u64 bpf_perf_event_read(u64 r1, u64 index, u64 r3, u64 r4, u64 r5)
188{
189	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
190	struct bpf_array *array = container_of(map, struct bpf_array, map);
191	struct perf_event *event;
192	struct file *file;
193
194	if (unlikely(index >= array->map.max_entries))
195		return -E2BIG;
196
197	file = (struct file *)array->ptrs[index];
198	if (unlikely(!file))
199		return -ENOENT;
200
201	event = file->private_data;
202
203	/* make sure event is local and doesn't have pmu::count */
204	if (event->oncpu != smp_processor_id() ||
205	    event->pmu->count)
206		return -EINVAL;
207
208	/*
209	 * we don't know if the function is run successfully by the
210	 * return value. It can be judged in other places, such as
211	 * eBPF programs.
212	 */
213	return perf_event_read_local(event);
214}
215
216static const struct bpf_func_proto bpf_perf_event_read_proto = {
217	.func		= bpf_perf_event_read,
218	.gpl_only	= true,
219	.ret_type	= RET_INTEGER,
220	.arg1_type	= ARG_CONST_MAP_PTR,
221	.arg2_type	= ARG_ANYTHING,
222};
223
224static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 index, u64 r4, u64 size)
225{
226	struct pt_regs *regs = (struct pt_regs *) (long) r1;
227	struct bpf_map *map = (struct bpf_map *) (long) r2;
228	struct bpf_array *array = container_of(map, struct bpf_array, map);
229	void *data = (void *) (long) r4;
230	struct perf_sample_data sample_data;
231	struct perf_event *event;
232	struct file *file;
233	struct perf_raw_record raw = {
234		.size = size,
235		.data = data,
236	};
237
238	if (unlikely(index >= array->map.max_entries))
239		return -E2BIG;
240
241	file = (struct file *)array->ptrs[index];
242	if (unlikely(!file))
243		return -ENOENT;
244
245	event = file->private_data;
246
247	if (unlikely(event->attr.type != PERF_TYPE_SOFTWARE ||
248		     event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
249		return -EINVAL;
250
251	if (unlikely(event->oncpu != smp_processor_id()))
252		return -EOPNOTSUPP;
253
254	perf_sample_data_init(&sample_data, 0, 0);
255	sample_data.raw = &raw;
256	perf_event_output(event, &sample_data, regs);
257	return 0;
258}
259
260static const struct bpf_func_proto bpf_perf_event_output_proto = {
261	.func		= bpf_perf_event_output,
262	.gpl_only	= true,
263	.ret_type	= RET_INTEGER,
264	.arg1_type	= ARG_PTR_TO_CTX,
265	.arg2_type	= ARG_CONST_MAP_PTR,
266	.arg3_type	= ARG_ANYTHING,
267	.arg4_type	= ARG_PTR_TO_STACK,
268	.arg5_type	= ARG_CONST_STACK_SIZE,
269};
270
271static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
272{
273	switch (func_id) {
274	case BPF_FUNC_map_lookup_elem:
275		return &bpf_map_lookup_elem_proto;
276	case BPF_FUNC_map_update_elem:
277		return &bpf_map_update_elem_proto;
278	case BPF_FUNC_map_delete_elem:
279		return &bpf_map_delete_elem_proto;
280	case BPF_FUNC_probe_read:
281		return &bpf_probe_read_proto;
282	case BPF_FUNC_ktime_get_ns:
283		return &bpf_ktime_get_ns_proto;
284	case BPF_FUNC_tail_call:
285		return &bpf_tail_call_proto;
286	case BPF_FUNC_get_current_pid_tgid:
287		return &bpf_get_current_pid_tgid_proto;
288	case BPF_FUNC_get_current_uid_gid:
289		return &bpf_get_current_uid_gid_proto;
290	case BPF_FUNC_get_current_comm:
291		return &bpf_get_current_comm_proto;
292	case BPF_FUNC_trace_printk:
293		return bpf_get_trace_printk_proto();
294	case BPF_FUNC_get_smp_processor_id:
295		return &bpf_get_smp_processor_id_proto;
296	case BPF_FUNC_perf_event_read:
297		return &bpf_perf_event_read_proto;
298	case BPF_FUNC_perf_event_output:
299		return &bpf_perf_event_output_proto;
300	case BPF_FUNC_get_stackid:
301		return &bpf_get_stackid_proto;
302	default:
303		return NULL;
304	}
305}
306
307/* bpf+kprobe programs can access fields of 'struct pt_regs' */
308static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type)
309{
310	/* check bounds */
311	if (off < 0 || off >= sizeof(struct pt_regs))
312		return false;
313
314	/* only read is allowed */
315	if (type != BPF_READ)
316		return false;
317
318	/* disallow misaligned access */
319	if (off % size != 0)
320		return false;
321
322	return true;
323}
324
325static const struct bpf_verifier_ops kprobe_prog_ops = {
326	.get_func_proto  = kprobe_prog_func_proto,
327	.is_valid_access = kprobe_prog_is_valid_access,
328};
329
330static struct bpf_prog_type_list kprobe_tl = {
331	.ops	= &kprobe_prog_ops,
332	.type	= BPF_PROG_TYPE_KPROBE,
333};
334
335static int __init register_kprobe_prog_ops(void)
336{
337	bpf_register_prog_type(&kprobe_tl);
338	return 0;
339}
340late_initcall(register_kprobe_prog_ops);