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 */ 30 unsigned 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 } 60 EXPORT_SYMBOL_GPL(trace_call_bpf); 61 62 static 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 71 static 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 */ 84 static 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 } 167 168 static 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 }; 175 176 const 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 } 186 187 static 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 } 215 216 static 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 }; 223 224 static 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 } 259 260 static 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 }; 270 271 static 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' */ 308 static 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 } 324 325 static 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 }; 329 330 static struct bpf_prog_type_list kprobe_tl = { 331 .ops = &kprobe_prog_ops, 332 .type = BPF_PROG_TYPE_KPROBE, 333 }; 334 335 static int __init register_kprobe_prog_ops(void) 336 { 337 bpf_register_prog_type(&kprobe_tl); 338 return 0; 339 } 340 late_initcall(register_kprobe_prog_ops); 341