1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) 2 // Copyright (c) 2022 Google 3 #include "vmlinux.h" 4 #include <bpf/bpf_helpers.h> 5 #include <bpf/bpf_tracing.h> 6 #include <bpf/bpf_core_read.h> 7 #include <asm-generic/errno-base.h> 8 9 #include "lock_data.h" 10 11 /* for collect_lock_syms(). 4096 was rejected by the verifier */ 12 #define MAX_CPUS 1024 13 14 /* lock contention flags from include/trace/events/lock.h */ 15 #define LCB_F_SPIN (1U << 0) 16 #define LCB_F_READ (1U << 1) 17 #define LCB_F_WRITE (1U << 2) 18 #define LCB_F_RT (1U << 3) 19 #define LCB_F_PERCPU (1U << 4) 20 #define LCB_F_MUTEX (1U << 5) 21 22 struct tstamp_data { 23 __u64 timestamp; 24 __u64 lock; 25 __u32 flags; 26 __s32 stack_id; 27 }; 28 29 /* callstack storage */ 30 struct { 31 __uint(type, BPF_MAP_TYPE_STACK_TRACE); 32 __uint(key_size, sizeof(__u32)); 33 __uint(value_size, sizeof(__u64)); 34 __uint(max_entries, MAX_ENTRIES); 35 } stacks SEC(".maps"); 36 37 /* maintain timestamp at the beginning of contention */ 38 struct { 39 __uint(type, BPF_MAP_TYPE_HASH); 40 __type(key, int); 41 __type(value, struct tstamp_data); 42 __uint(max_entries, MAX_ENTRIES); 43 } tstamp SEC(".maps"); 44 45 /* actual lock contention statistics */ 46 struct { 47 __uint(type, BPF_MAP_TYPE_HASH); 48 __uint(key_size, sizeof(struct contention_key)); 49 __uint(value_size, sizeof(struct contention_data)); 50 __uint(max_entries, MAX_ENTRIES); 51 } lock_stat SEC(".maps"); 52 53 struct { 54 __uint(type, BPF_MAP_TYPE_HASH); 55 __uint(key_size, sizeof(__u32)); 56 __uint(value_size, sizeof(struct contention_task_data)); 57 __uint(max_entries, MAX_ENTRIES); 58 } task_data SEC(".maps"); 59 60 struct { 61 __uint(type, BPF_MAP_TYPE_HASH); 62 __uint(key_size, sizeof(__u64)); 63 __uint(value_size, sizeof(__u32)); 64 __uint(max_entries, MAX_ENTRIES); 65 } lock_syms SEC(".maps"); 66 67 struct { 68 __uint(type, BPF_MAP_TYPE_HASH); 69 __uint(key_size, sizeof(__u32)); 70 __uint(value_size, sizeof(__u8)); 71 __uint(max_entries, 1); 72 } cpu_filter SEC(".maps"); 73 74 struct { 75 __uint(type, BPF_MAP_TYPE_HASH); 76 __uint(key_size, sizeof(__u32)); 77 __uint(value_size, sizeof(__u8)); 78 __uint(max_entries, 1); 79 } task_filter SEC(".maps"); 80 81 struct { 82 __uint(type, BPF_MAP_TYPE_HASH); 83 __uint(key_size, sizeof(__u32)); 84 __uint(value_size, sizeof(__u8)); 85 __uint(max_entries, 1); 86 } type_filter SEC(".maps"); 87 88 struct { 89 __uint(type, BPF_MAP_TYPE_HASH); 90 __uint(key_size, sizeof(__u64)); 91 __uint(value_size, sizeof(__u8)); 92 __uint(max_entries, 1); 93 } addr_filter SEC(".maps"); 94 95 struct rw_semaphore___old { 96 struct task_struct *owner; 97 } __attribute__((preserve_access_index)); 98 99 struct rw_semaphore___new { 100 atomic_long_t owner; 101 } __attribute__((preserve_access_index)); 102 103 struct mm_struct___old { 104 struct rw_semaphore mmap_sem; 105 } __attribute__((preserve_access_index)); 106 107 struct mm_struct___new { 108 struct rw_semaphore mmap_lock; 109 } __attribute__((preserve_access_index)); 110 111 /* control flags */ 112 int enabled; 113 int has_cpu; 114 int has_task; 115 int has_type; 116 int has_addr; 117 int needs_callstack; 118 int stack_skip; 119 int lock_owner; 120 121 /* determine the key of lock stat */ 122 int aggr_mode; 123 124 /* error stat */ 125 int task_fail; 126 int stack_fail; 127 int time_fail; 128 int data_fail; 129 130 int task_map_full; 131 int data_map_full; 132 133 static inline int can_record(u64 *ctx) 134 { 135 if (has_cpu) { 136 __u32 cpu = bpf_get_smp_processor_id(); 137 __u8 *ok; 138 139 ok = bpf_map_lookup_elem(&cpu_filter, &cpu); 140 if (!ok) 141 return 0; 142 } 143 144 if (has_task) { 145 __u8 *ok; 146 __u32 pid = bpf_get_current_pid_tgid(); 147 148 ok = bpf_map_lookup_elem(&task_filter, &pid); 149 if (!ok) 150 return 0; 151 } 152 153 if (has_type) { 154 __u8 *ok; 155 __u32 flags = (__u32)ctx[1]; 156 157 ok = bpf_map_lookup_elem(&type_filter, &flags); 158 if (!ok) 159 return 0; 160 } 161 162 if (has_addr) { 163 __u8 *ok; 164 __u64 addr = ctx[0]; 165 166 ok = bpf_map_lookup_elem(&addr_filter, &addr); 167 if (!ok) 168 return 0; 169 } 170 171 return 1; 172 } 173 174 static inline int update_task_data(struct task_struct *task) 175 { 176 struct contention_task_data *p; 177 int pid, err; 178 179 err = bpf_core_read(&pid, sizeof(pid), &task->pid); 180 if (err) 181 return -1; 182 183 p = bpf_map_lookup_elem(&task_data, &pid); 184 if (p == NULL && !task_map_full) { 185 struct contention_task_data data = {}; 186 187 BPF_CORE_READ_STR_INTO(&data.comm, task, comm); 188 if (bpf_map_update_elem(&task_data, &pid, &data, BPF_NOEXIST) == -E2BIG) 189 task_map_full = 1; 190 } 191 192 return 0; 193 } 194 195 #ifndef __has_builtin 196 # define __has_builtin(x) 0 197 #endif 198 199 static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags) 200 { 201 struct task_struct *task; 202 __u64 owner = 0; 203 204 if (flags & LCB_F_MUTEX) { 205 struct mutex *mutex = (void *)lock; 206 owner = BPF_CORE_READ(mutex, owner.counter); 207 } else if (flags == LCB_F_READ || flags == LCB_F_WRITE) { 208 /* 209 * Support for the BPF_TYPE_MATCHES argument to the 210 * __builtin_preserve_type_info builtin was added at some point during 211 * development of clang 15 and it's what is needed for 212 * bpf_core_type_matches. 213 */ 214 #if __has_builtin(__builtin_preserve_type_info) && __clang_major__ >= 15 215 if (bpf_core_type_matches(struct rw_semaphore___old)) { 216 struct rw_semaphore___old *rwsem = (void *)lock; 217 owner = (unsigned long)BPF_CORE_READ(rwsem, owner); 218 } else if (bpf_core_type_matches(struct rw_semaphore___new)) { 219 struct rw_semaphore___new *rwsem = (void *)lock; 220 owner = BPF_CORE_READ(rwsem, owner.counter); 221 } 222 #else 223 /* assume new struct */ 224 struct rw_semaphore *rwsem = (void *)lock; 225 owner = BPF_CORE_READ(rwsem, owner.counter); 226 #endif 227 } 228 229 if (!owner) 230 return NULL; 231 232 task = (void *)(owner & ~7UL); 233 return task; 234 } 235 236 static inline __u32 check_lock_type(__u64 lock, __u32 flags) 237 { 238 struct task_struct *curr; 239 struct mm_struct___old *mm_old; 240 struct mm_struct___new *mm_new; 241 242 switch (flags) { 243 case LCB_F_READ: /* rwsem */ 244 case LCB_F_WRITE: 245 curr = bpf_get_current_task_btf(); 246 if (curr->mm == NULL) 247 break; 248 mm_new = (void *)curr->mm; 249 if (bpf_core_field_exists(mm_new->mmap_lock)) { 250 if (&mm_new->mmap_lock == (void *)lock) 251 return LCD_F_MMAP_LOCK; 252 break; 253 } 254 mm_old = (void *)curr->mm; 255 if (bpf_core_field_exists(mm_old->mmap_sem)) { 256 if (&mm_old->mmap_sem == (void *)lock) 257 return LCD_F_MMAP_LOCK; 258 } 259 break; 260 case LCB_F_SPIN: /* spinlock */ 261 curr = bpf_get_current_task_btf(); 262 if (&curr->sighand->siglock == (void *)lock) 263 return LCD_F_SIGHAND_LOCK; 264 break; 265 default: 266 break; 267 } 268 return 0; 269 } 270 271 SEC("tp_btf/contention_begin") 272 int contention_begin(u64 *ctx) 273 { 274 __u32 pid; 275 struct tstamp_data *pelem; 276 277 if (!enabled || !can_record(ctx)) 278 return 0; 279 280 pid = bpf_get_current_pid_tgid(); 281 pelem = bpf_map_lookup_elem(&tstamp, &pid); 282 if (pelem && pelem->lock) 283 return 0; 284 285 if (pelem == NULL) { 286 struct tstamp_data zero = {}; 287 288 bpf_map_update_elem(&tstamp, &pid, &zero, BPF_ANY); 289 pelem = bpf_map_lookup_elem(&tstamp, &pid); 290 if (pelem == NULL) { 291 __sync_fetch_and_add(&task_fail, 1); 292 return 0; 293 } 294 } 295 296 pelem->timestamp = bpf_ktime_get_ns(); 297 pelem->lock = (__u64)ctx[0]; 298 pelem->flags = (__u32)ctx[1]; 299 300 if (needs_callstack) { 301 pelem->stack_id = bpf_get_stackid(ctx, &stacks, 302 BPF_F_FAST_STACK_CMP | stack_skip); 303 if (pelem->stack_id < 0) 304 __sync_fetch_and_add(&stack_fail, 1); 305 } else if (aggr_mode == LOCK_AGGR_TASK) { 306 struct task_struct *task; 307 308 if (lock_owner) { 309 task = get_lock_owner(pelem->lock, pelem->flags); 310 311 /* The flags is not used anymore. Pass the owner pid. */ 312 if (task) 313 pelem->flags = BPF_CORE_READ(task, pid); 314 else 315 pelem->flags = -1U; 316 317 } else { 318 task = bpf_get_current_task_btf(); 319 } 320 321 if (task) { 322 if (update_task_data(task) < 0 && lock_owner) 323 pelem->flags = -1U; 324 } 325 } 326 327 return 0; 328 } 329 330 SEC("tp_btf/contention_end") 331 int contention_end(u64 *ctx) 332 { 333 __u32 pid; 334 struct tstamp_data *pelem; 335 struct contention_key key = {}; 336 struct contention_data *data; 337 __u64 duration; 338 339 if (!enabled) 340 return 0; 341 342 pid = bpf_get_current_pid_tgid(); 343 pelem = bpf_map_lookup_elem(&tstamp, &pid); 344 if (!pelem || pelem->lock != ctx[0]) 345 return 0; 346 347 duration = bpf_ktime_get_ns() - pelem->timestamp; 348 if ((__s64)duration < 0) { 349 bpf_map_delete_elem(&tstamp, &pid); 350 __sync_fetch_and_add(&time_fail, 1); 351 return 0; 352 } 353 354 switch (aggr_mode) { 355 case LOCK_AGGR_CALLER: 356 key.stack_id = pelem->stack_id; 357 break; 358 case LOCK_AGGR_TASK: 359 if (lock_owner) 360 key.pid = pelem->flags; 361 else 362 key.pid = pid; 363 if (needs_callstack) 364 key.stack_id = pelem->stack_id; 365 break; 366 case LOCK_AGGR_ADDR: 367 key.lock_addr = pelem->lock; 368 if (needs_callstack) 369 key.stack_id = pelem->stack_id; 370 break; 371 default: 372 /* should not happen */ 373 return 0; 374 } 375 376 data = bpf_map_lookup_elem(&lock_stat, &key); 377 if (!data) { 378 if (data_map_full) { 379 bpf_map_delete_elem(&tstamp, &pid); 380 __sync_fetch_and_add(&data_fail, 1); 381 return 0; 382 } 383 384 struct contention_data first = { 385 .total_time = duration, 386 .max_time = duration, 387 .min_time = duration, 388 .count = 1, 389 .flags = pelem->flags, 390 }; 391 int err; 392 393 if (aggr_mode == LOCK_AGGR_ADDR) 394 first.flags |= check_lock_type(pelem->lock, pelem->flags); 395 396 err = bpf_map_update_elem(&lock_stat, &key, &first, BPF_NOEXIST); 397 if (err < 0) { 398 if (err == -E2BIG) 399 data_map_full = 1; 400 __sync_fetch_and_add(&data_fail, 1); 401 } 402 bpf_map_delete_elem(&tstamp, &pid); 403 return 0; 404 } 405 406 __sync_fetch_and_add(&data->total_time, duration); 407 __sync_fetch_and_add(&data->count, 1); 408 409 /* FIXME: need atomic operations */ 410 if (data->max_time < duration) 411 data->max_time = duration; 412 if (data->min_time > duration) 413 data->min_time = duration; 414 415 bpf_map_delete_elem(&tstamp, &pid); 416 return 0; 417 } 418 419 struct rq {}; 420 421 extern struct rq runqueues __ksym; 422 423 struct rq___old { 424 raw_spinlock_t lock; 425 } __attribute__((preserve_access_index)); 426 427 struct rq___new { 428 raw_spinlock_t __lock; 429 } __attribute__((preserve_access_index)); 430 431 SEC("raw_tp/bpf_test_finish") 432 int BPF_PROG(collect_lock_syms) 433 { 434 __u64 lock_addr, lock_off; 435 __u32 lock_flag; 436 437 if (bpf_core_field_exists(struct rq___new, __lock)) 438 lock_off = offsetof(struct rq___new, __lock); 439 else 440 lock_off = offsetof(struct rq___old, lock); 441 442 for (int i = 0; i < MAX_CPUS; i++) { 443 struct rq *rq = bpf_per_cpu_ptr(&runqueues, i); 444 445 if (rq == NULL) 446 break; 447 448 lock_addr = (__u64)(void *)rq + lock_off; 449 lock_flag = LOCK_CLASS_RQLOCK; 450 bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY); 451 } 452 return 0; 453 } 454 455 char LICENSE[] SEC("license") = "Dual BSD/GPL"; 456