1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
/* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/uaccess.h>
#include <linux/ctype.h>
#include "trace.h"
static DEFINE_PER_CPU(int, bpf_prog_active);
/**
* trace_call_bpf - invoke BPF program
* @prog: BPF program
* @ctx: opaque context pointer
*
* kprobe handlers execute BPF programs via this helper.
* Can be used from static tracepoints in the future.
*
* Return: BPF programs always return an integer which is interpreted by
* kprobe handler as:
* 0 - return from kprobe (event is filtered out)
* 1 - store kprobe event into ring buffer
* Other values are reserved and currently alias to 1
*/
unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
{
unsigned int ret;
if (in_nmi()) /* not supported yet */
return 1;
preempt_disable();
if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
/*
* since some bpf program is already running on this cpu,
* don't call into another bpf program (same or different)
* and don't send kprobe event into ring-buffer,
* so return zero here
*/
ret = 0;
goto out;
}
rcu_read_lock();
ret = BPF_PROG_RUN(prog, ctx);
rcu_read_unlock();
out:
__this_cpu_dec(bpf_prog_active);
preempt_enable();
return ret;
}
EXPORT_SYMBOL_GPL(trace_call_bpf);
static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
{
void *dst = (void *) (long) r1;
int size = (int) r2;
void *unsafe_ptr = (void *) (long) r3;
return probe_kernel_read(dst, unsafe_ptr, size);
}
static const struct bpf_func_proto bpf_probe_read_proto = {
.func = bpf_probe_read,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_STACK,
.arg2_type = ARG_CONST_STACK_SIZE,
.arg3_type = ARG_ANYTHING,
};
/*
* limited trace_printk()
* only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed
*/
static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
{
char *fmt = (char *) (long) r1;
int mod[3] = {};
int fmt_cnt = 0;
int i;
/*
* bpf_check()->check_func_arg()->check_stack_boundary()
* guarantees that fmt points to bpf program stack,
* fmt_size bytes of it were initialized and fmt_size > 0
*/
if (fmt[--fmt_size] != 0)
return -EINVAL;
/* check format string for allowed specifiers */
for (i = 0; i < fmt_size; i++) {
if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
return -EINVAL;
if (fmt[i] != '%')
continue;
if (fmt_cnt >= 3)
return -EINVAL;
/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
i++;
if (fmt[i] == 'l') {
mod[fmt_cnt]++;
i++;
} else if (fmt[i] == 'p') {
mod[fmt_cnt]++;
i++;
if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
return -EINVAL;
fmt_cnt++;
continue;
}
if (fmt[i] == 'l') {
mod[fmt_cnt]++;
i++;
}
if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
return -EINVAL;
fmt_cnt++;
}
return __trace_printk(1/* fake ip will not be printed */, fmt,
mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3,
mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4,
mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5);
}
static const struct bpf_func_proto bpf_trace_printk_proto = {
.func = bpf_trace_printk,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_STACK,
.arg2_type = ARG_CONST_STACK_SIZE,
};
const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
{
/*
* this program might be calling bpf_trace_printk,
* so allocate per-cpu printk buffers
*/
trace_printk_init_buffers();
return &bpf_trace_printk_proto;
}
static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
{
switch (func_id) {
case BPF_FUNC_map_lookup_elem:
return &bpf_map_lookup_elem_proto;
case BPF_FUNC_map_update_elem:
return &bpf_map_update_elem_proto;
case BPF_FUNC_map_delete_elem:
return &bpf_map_delete_elem_proto;
case BPF_FUNC_probe_read:
return &bpf_probe_read_proto;
case BPF_FUNC_ktime_get_ns:
return &bpf_ktime_get_ns_proto;
case BPF_FUNC_tail_call:
return &bpf_tail_call_proto;
case BPF_FUNC_get_current_pid_tgid:
return &bpf_get_current_pid_tgid_proto;
case BPF_FUNC_get_current_uid_gid:
return &bpf_get_current_uid_gid_proto;
case BPF_FUNC_get_current_comm:
return &bpf_get_current_comm_proto;
case BPF_FUNC_trace_printk:
return bpf_get_trace_printk_proto();
case BPF_FUNC_get_smp_processor_id:
return &bpf_get_smp_processor_id_proto;
default:
return NULL;
}
}
/* bpf+kprobe programs can access fields of 'struct pt_regs' */
static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type)
{
/* check bounds */
if (off < 0 || off >= sizeof(struct pt_regs))
return false;
/* only read is allowed */
if (type != BPF_READ)
return false;
/* disallow misaligned access */
if (off % size != 0)
return false;
return true;
}
static struct bpf_verifier_ops kprobe_prog_ops = {
.get_func_proto = kprobe_prog_func_proto,
.is_valid_access = kprobe_prog_is_valid_access,
};
static struct bpf_prog_type_list kprobe_tl = {
.ops = &kprobe_prog_ops,
.type = BPF_PROG_TYPE_KPROBE,
};
static int __init register_kprobe_prog_ops(void)
{
bpf_register_prog_type(&kprobe_tl);
return 0;
}
late_initcall(register_kprobe_prog_ops);
|
