1 /* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com
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.
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>
16 static DEFINE_PER_CPU(int, bpf_prog_active);
19 * trace_call_bpf - invoke BPF program
21 * @ctx: opaque context pointer
23 * kprobe handlers execute BPF programs via this helper.
24 * Can be used from static tracepoints in the future.
26 * Return: BPF programs always return an integer which is interpreted by
28 * 0 - return from kprobe (event is filtered out)
29 * 1 - store kprobe event into ring buffer
30 * Other values are reserved and currently alias to 1
32 unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
36 if (in_nmi()) /* not supported yet */
41 if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
43 * since some bpf program is already running on this cpu,
44 * don't call into another bpf program (same or different)
45 * and don't send kprobe event into ring-buffer,
53 ret = BPF_PROG_RUN(prog, ctx);
57 __this_cpu_dec(bpf_prog_active);
62 EXPORT_SYMBOL_GPL(trace_call_bpf);
64 static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
66 void *dst = (void *) (long) r1;
68 void *unsafe_ptr = (void *) (long) r3;
70 return probe_kernel_read(dst, unsafe_ptr, size);
73 static const struct bpf_func_proto bpf_probe_read_proto = {
74 .func = bpf_probe_read,
76 .ret_type = RET_INTEGER,
77 .arg1_type = ARG_PTR_TO_STACK,
78 .arg2_type = ARG_CONST_STACK_SIZE,
79 .arg3_type = ARG_ANYTHING,
83 * limited trace_printk()
84 * only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed
86 static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
88 char *fmt = (char *) (long) r1;
94 * bpf_check()->check_func_arg()->check_stack_boundary()
95 * guarantees that fmt points to bpf program stack,
96 * fmt_size bytes of it were initialized and fmt_size > 0
98 if (fmt[--fmt_size] != 0)
101 /* check format string for allowed specifiers */
102 for (i = 0; i < fmt_size; i++) {
103 if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
112 /* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
117 } else if (fmt[i] == 'p') {
120 if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
131 if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
136 return __trace_printk(1/* fake ip will not be printed */, fmt,
137 mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3,
138 mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4,
139 mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5);
142 static const struct bpf_func_proto bpf_trace_printk_proto = {
143 .func = bpf_trace_printk,
145 .ret_type = RET_INTEGER,
146 .arg1_type = ARG_PTR_TO_STACK,
147 .arg2_type = ARG_CONST_STACK_SIZE,
150 static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
153 case BPF_FUNC_map_lookup_elem:
154 return &bpf_map_lookup_elem_proto;
155 case BPF_FUNC_map_update_elem:
156 return &bpf_map_update_elem_proto;
157 case BPF_FUNC_map_delete_elem:
158 return &bpf_map_delete_elem_proto;
159 case BPF_FUNC_probe_read:
160 return &bpf_probe_read_proto;
161 case BPF_FUNC_ktime_get_ns:
162 return &bpf_ktime_get_ns_proto;
163 case BPF_FUNC_tail_call:
164 return &bpf_tail_call_proto;
166 case BPF_FUNC_trace_printk:
168 * this program might be calling bpf_trace_printk,
169 * so allocate per-cpu printk buffers
171 trace_printk_init_buffers();
173 return &bpf_trace_printk_proto;
179 /* bpf+kprobe programs can access fields of 'struct pt_regs' */
180 static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type)
183 if (off < 0 || off >= sizeof(struct pt_regs))
186 /* only read is allowed */
187 if (type != BPF_READ)
190 /* disallow misaligned access */
197 static struct bpf_verifier_ops kprobe_prog_ops = {
198 .get_func_proto = kprobe_prog_func_proto,
199 .is_valid_access = kprobe_prog_is_valid_access,
202 static struct bpf_prog_type_list kprobe_tl = {
203 .ops = &kprobe_prog_ops,
204 .type = BPF_PROG_TYPE_KPROBE,
207 static int __init register_kprobe_prog_ops(void)
209 bpf_register_prog_type(&kprobe_tl);
212 late_initcall(register_kprobe_prog_ops);