1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Stress userfaultfd syscall. 4 * 5 * Copyright (C) 2015 Red Hat, Inc. 6 * 7 * This test allocates two virtual areas and bounces the physical 8 * memory across the two virtual areas (from area_src to area_dst) 9 * using userfaultfd. 10 * 11 * There are three threads running per CPU: 12 * 13 * 1) one per-CPU thread takes a per-page pthread_mutex in a random 14 * page of the area_dst (while the physical page may still be in 15 * area_src), and increments a per-page counter in the same page, 16 * and checks its value against a verification region. 17 * 18 * 2) another per-CPU thread handles the userfaults generated by 19 * thread 1 above. userfaultfd blocking reads or poll() modes are 20 * exercised interleaved. 21 * 22 * 3) one last per-CPU thread transfers the memory in the background 23 * at maximum bandwidth (if not already transferred by thread 24 * 2). Each cpu thread takes cares of transferring a portion of the 25 * area. 26 * 27 * When all threads of type 3 completed the transfer, one bounce is 28 * complete. area_src and area_dst are then swapped. All threads are 29 * respawned and so the bounce is immediately restarted in the 30 * opposite direction. 31 * 32 * per-CPU threads 1 by triggering userfaults inside 33 * pthread_mutex_lock will also verify the atomicity of the memory 34 * transfer (UFFDIO_COPY). 35 */ 36 37 #include "uffd-common.h" 38 39 uint64_t features; 40 #ifdef __NR_userfaultfd 41 42 #define BOUNCE_RANDOM (1<<0) 43 #define BOUNCE_RACINGFAULTS (1<<1) 44 #define BOUNCE_VERIFY (1<<2) 45 #define BOUNCE_POLL (1<<3) 46 static int bounces; 47 48 /* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */ 49 #define ALARM_INTERVAL_SECS 10 50 static char *zeropage; 51 pthread_attr_t attr; 52 53 #define swap(a, b) \ 54 do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0) 55 56 const char *examples = 57 "# Run anonymous memory test on 100MiB region with 99999 bounces:\n" 58 "./uffd-stress anon 100 99999\n\n" 59 "# Run share memory test on 1GiB region with 99 bounces:\n" 60 "./uffd-stress shmem 1000 99\n\n" 61 "# Run hugetlb memory test on 256MiB region with 50 bounces:\n" 62 "./uffd-stress hugetlb 256 50\n\n" 63 "# Run the same hugetlb test but using private file:\n" 64 "./uffd-stress hugetlb-private 256 50\n\n" 65 "# 10MiB-~6GiB 999 bounces anonymous test, " 66 "continue forever unless an error triggers\n" 67 "while ./uffd-stress anon $[RANDOM % 6000 + 10] 999; do true; done\n\n"; 68 69 static void usage(void) 70 { 71 fprintf(stderr, "\nUsage: ./uffd-stress <test type> <MiB> <bounces>\n\n"); 72 fprintf(stderr, "Supported <test type>: anon, hugetlb, " 73 "hugetlb-private, shmem, shmem-private\n\n"); 74 fprintf(stderr, "Examples:\n\n"); 75 fprintf(stderr, "%s", examples); 76 exit(1); 77 } 78 79 static void uffd_stats_reset(struct uffd_args *args, unsigned long n_cpus) 80 { 81 int i; 82 83 for (i = 0; i < n_cpus; i++) { 84 args[i].cpu = i; 85 args[i].apply_wp = test_uffdio_wp; 86 args[i].missing_faults = 0; 87 args[i].wp_faults = 0; 88 args[i].minor_faults = 0; 89 } 90 } 91 92 static void *locking_thread(void *arg) 93 { 94 unsigned long cpu = (unsigned long) arg; 95 unsigned long page_nr; 96 unsigned long long count; 97 98 if (!(bounces & BOUNCE_RANDOM)) { 99 page_nr = -bounces; 100 if (!(bounces & BOUNCE_RACINGFAULTS)) 101 page_nr += cpu * nr_pages_per_cpu; 102 } 103 104 while (!finished) { 105 if (bounces & BOUNCE_RANDOM) { 106 if (getrandom(&page_nr, sizeof(page_nr), 0) != sizeof(page_nr)) 107 err("getrandom failed"); 108 } else 109 page_nr += 1; 110 page_nr %= nr_pages; 111 pthread_mutex_lock(area_mutex(area_dst, page_nr)); 112 count = *area_count(area_dst, page_nr); 113 if (count != count_verify[page_nr]) 114 err("page_nr %lu memory corruption %llu %llu", 115 page_nr, count, count_verify[page_nr]); 116 count++; 117 *area_count(area_dst, page_nr) = count_verify[page_nr] = count; 118 pthread_mutex_unlock(area_mutex(area_dst, page_nr)); 119 } 120 121 return NULL; 122 } 123 124 static int copy_page_retry(int ufd, unsigned long offset) 125 { 126 return __copy_page(ufd, offset, true, test_uffdio_wp); 127 } 128 129 pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER; 130 131 static void *uffd_read_thread(void *arg) 132 { 133 struct uffd_args *args = (struct uffd_args *)arg; 134 struct uffd_msg msg; 135 136 pthread_mutex_unlock(&uffd_read_mutex); 137 /* from here cancellation is ok */ 138 139 for (;;) { 140 if (uffd_read_msg(uffd, &msg)) 141 continue; 142 uffd_handle_page_fault(&msg, args); 143 } 144 145 return NULL; 146 } 147 148 static void *background_thread(void *arg) 149 { 150 unsigned long cpu = (unsigned long) arg; 151 unsigned long page_nr, start_nr, mid_nr, end_nr; 152 153 start_nr = cpu * nr_pages_per_cpu; 154 end_nr = (cpu+1) * nr_pages_per_cpu; 155 mid_nr = (start_nr + end_nr) / 2; 156 157 /* Copy the first half of the pages */ 158 for (page_nr = start_nr; page_nr < mid_nr; page_nr++) 159 copy_page_retry(uffd, page_nr * page_size); 160 161 /* 162 * If we need to test uffd-wp, set it up now. Then we'll have 163 * at least the first half of the pages mapped already which 164 * can be write-protected for testing 165 */ 166 if (test_uffdio_wp) 167 wp_range(uffd, (unsigned long)area_dst + start_nr * page_size, 168 nr_pages_per_cpu * page_size, true); 169 170 /* 171 * Continue the 2nd half of the page copying, handling write 172 * protection faults if any 173 */ 174 for (page_nr = mid_nr; page_nr < end_nr; page_nr++) 175 copy_page_retry(uffd, page_nr * page_size); 176 177 return NULL; 178 } 179 180 static int stress(struct uffd_args *args) 181 { 182 unsigned long cpu; 183 pthread_t locking_threads[nr_parallel]; 184 pthread_t uffd_threads[nr_parallel]; 185 pthread_t background_threads[nr_parallel]; 186 187 finished = 0; 188 for (cpu = 0; cpu < nr_parallel; cpu++) { 189 if (pthread_create(&locking_threads[cpu], &attr, 190 locking_thread, (void *)cpu)) 191 return 1; 192 if (bounces & BOUNCE_POLL) { 193 if (pthread_create(&uffd_threads[cpu], &attr, uffd_poll_thread, &args[cpu])) 194 err("uffd_poll_thread create"); 195 } else { 196 if (pthread_create(&uffd_threads[cpu], &attr, 197 uffd_read_thread, 198 (void *)&args[cpu])) 199 return 1; 200 pthread_mutex_lock(&uffd_read_mutex); 201 } 202 if (pthread_create(&background_threads[cpu], &attr, 203 background_thread, (void *)cpu)) 204 return 1; 205 } 206 for (cpu = 0; cpu < nr_parallel; cpu++) 207 if (pthread_join(background_threads[cpu], NULL)) 208 return 1; 209 210 /* 211 * Be strict and immediately zap area_src, the whole area has 212 * been transferred already by the background treads. The 213 * area_src could then be faulted in a racy way by still 214 * running uffdio_threads reading zeropages after we zapped 215 * area_src (but they're guaranteed to get -EEXIST from 216 * UFFDIO_COPY without writing zero pages into area_dst 217 * because the background threads already completed). 218 */ 219 uffd_test_ops->release_pages(area_src); 220 221 finished = 1; 222 for (cpu = 0; cpu < nr_parallel; cpu++) 223 if (pthread_join(locking_threads[cpu], NULL)) 224 return 1; 225 226 for (cpu = 0; cpu < nr_parallel; cpu++) { 227 char c; 228 if (bounces & BOUNCE_POLL) { 229 if (write(pipefd[cpu*2+1], &c, 1) != 1) 230 err("pipefd write error"); 231 if (pthread_join(uffd_threads[cpu], 232 (void *)&args[cpu])) 233 return 1; 234 } else { 235 if (pthread_cancel(uffd_threads[cpu])) 236 return 1; 237 if (pthread_join(uffd_threads[cpu], NULL)) 238 return 1; 239 } 240 } 241 242 return 0; 243 } 244 245 static int userfaultfd_stress(void) 246 { 247 void *area; 248 unsigned long nr; 249 struct uffd_args args[nr_parallel]; 250 uint64_t mem_size = nr_pages * page_size; 251 int flags = 0; 252 253 memset(args, 0, sizeof(struct uffd_args) * nr_parallel); 254 255 if (features & UFFD_FEATURE_WP_UNPOPULATED && test_type == TEST_ANON) 256 flags = UFFD_FEATURE_WP_UNPOPULATED; 257 258 if (uffd_test_ctx_init(flags, NULL)) 259 err("context init failed"); 260 261 if (posix_memalign(&area, page_size, page_size)) 262 err("out of memory"); 263 zeropage = area; 264 bzero(zeropage, page_size); 265 266 pthread_mutex_lock(&uffd_read_mutex); 267 268 pthread_attr_init(&attr); 269 pthread_attr_setstacksize(&attr, 16*1024*1024); 270 271 while (bounces--) { 272 printf("bounces: %d, mode:", bounces); 273 if (bounces & BOUNCE_RANDOM) 274 printf(" rnd"); 275 if (bounces & BOUNCE_RACINGFAULTS) 276 printf(" racing"); 277 if (bounces & BOUNCE_VERIFY) 278 printf(" ver"); 279 if (bounces & BOUNCE_POLL) 280 printf(" poll"); 281 else 282 printf(" read"); 283 printf(", "); 284 fflush(stdout); 285 286 if (bounces & BOUNCE_POLL) 287 fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); 288 else 289 fcntl(uffd, F_SETFL, uffd_flags & ~O_NONBLOCK); 290 291 /* register */ 292 if (uffd_register(uffd, area_dst, mem_size, 293 true, test_uffdio_wp, false)) 294 err("register failure"); 295 296 if (area_dst_alias) { 297 if (uffd_register(uffd, area_dst_alias, mem_size, 298 true, test_uffdio_wp, false)) 299 err("register failure alias"); 300 } 301 302 /* 303 * The madvise done previously isn't enough: some 304 * uffd_thread could have read userfaults (one of 305 * those already resolved by the background thread) 306 * and it may be in the process of calling 307 * UFFDIO_COPY. UFFDIO_COPY will read the zapped 308 * area_src and it would map a zero page in it (of 309 * course such a UFFDIO_COPY is perfectly safe as it'd 310 * return -EEXIST). The problem comes at the next 311 * bounce though: that racing UFFDIO_COPY would 312 * generate zeropages in the area_src, so invalidating 313 * the previous MADV_DONTNEED. Without this additional 314 * MADV_DONTNEED those zeropages leftovers in the 315 * area_src would lead to -EEXIST failure during the 316 * next bounce, effectively leaving a zeropage in the 317 * area_dst. 318 * 319 * Try to comment this out madvise to see the memory 320 * corruption being caught pretty quick. 321 * 322 * khugepaged is also inhibited to collapse THP after 323 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's 324 * required to MADV_DONTNEED here. 325 */ 326 uffd_test_ops->release_pages(area_dst); 327 328 uffd_stats_reset(args, nr_parallel); 329 330 /* bounce pass */ 331 if (stress(args)) { 332 uffd_test_ctx_clear(); 333 return 1; 334 } 335 336 /* Clear all the write protections if there is any */ 337 if (test_uffdio_wp) 338 wp_range(uffd, (unsigned long)area_dst, 339 nr_pages * page_size, false); 340 341 /* unregister */ 342 if (uffd_unregister(uffd, area_dst, mem_size)) 343 err("unregister failure"); 344 if (area_dst_alias) { 345 if (uffd_unregister(uffd, area_dst_alias, mem_size)) 346 err("unregister failure alias"); 347 } 348 349 /* verification */ 350 if (bounces & BOUNCE_VERIFY) 351 for (nr = 0; nr < nr_pages; nr++) 352 if (*area_count(area_dst, nr) != count_verify[nr]) 353 err("error area_count %llu %llu %lu\n", 354 *area_count(area_src, nr), 355 count_verify[nr], nr); 356 357 /* prepare next bounce */ 358 swap(area_src, area_dst); 359 360 swap(area_src_alias, area_dst_alias); 361 362 uffd_stats_report(args, nr_parallel); 363 } 364 uffd_test_ctx_clear(); 365 366 return 0; 367 } 368 369 static void set_test_type(const char *type) 370 { 371 if (!strcmp(type, "anon")) { 372 test_type = TEST_ANON; 373 uffd_test_ops = &anon_uffd_test_ops; 374 } else if (!strcmp(type, "hugetlb")) { 375 test_type = TEST_HUGETLB; 376 uffd_test_ops = &hugetlb_uffd_test_ops; 377 map_shared = true; 378 } else if (!strcmp(type, "hugetlb-private")) { 379 test_type = TEST_HUGETLB; 380 uffd_test_ops = &hugetlb_uffd_test_ops; 381 } else if (!strcmp(type, "shmem")) { 382 map_shared = true; 383 test_type = TEST_SHMEM; 384 uffd_test_ops = &shmem_uffd_test_ops; 385 } else if (!strcmp(type, "shmem-private")) { 386 test_type = TEST_SHMEM; 387 uffd_test_ops = &shmem_uffd_test_ops; 388 } 389 } 390 391 static void parse_test_type_arg(const char *raw_type) 392 { 393 set_test_type(raw_type); 394 395 if (!test_type) 396 err("failed to parse test type argument: '%s'", raw_type); 397 398 if (test_type == TEST_HUGETLB) 399 page_size = default_huge_page_size(); 400 else 401 page_size = sysconf(_SC_PAGE_SIZE); 402 403 if (!page_size) 404 err("Unable to determine page size"); 405 if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2 406 > page_size) 407 err("Impossible to run this test"); 408 409 /* 410 * Whether we can test certain features depends not just on test type, 411 * but also on whether or not this particular kernel supports the 412 * feature. 413 */ 414 415 if (uffd_get_features(&features) && errno == ENOENT) 416 ksft_exit_skip("failed to get available features (%d)\n", errno); 417 418 test_uffdio_wp = test_uffdio_wp && 419 (features & UFFD_FEATURE_PAGEFAULT_FLAG_WP); 420 421 if (test_type != TEST_ANON && !(features & UFFD_FEATURE_WP_HUGETLBFS_SHMEM)) 422 test_uffdio_wp = false; 423 424 close(uffd); 425 uffd = -1; 426 } 427 428 static void sigalrm(int sig) 429 { 430 if (sig != SIGALRM) 431 abort(); 432 test_uffdio_copy_eexist = true; 433 alarm(ALARM_INTERVAL_SECS); 434 } 435 436 int main(int argc, char **argv) 437 { 438 unsigned long nr_cpus; 439 size_t bytes; 440 441 if (argc < 4) 442 usage(); 443 444 if (signal(SIGALRM, sigalrm) == SIG_ERR) 445 err("failed to arm SIGALRM"); 446 alarm(ALARM_INTERVAL_SECS); 447 448 parse_test_type_arg(argv[1]); 449 bytes = atol(argv[2]) * 1024 * 1024; 450 451 if (test_type == TEST_HUGETLB && 452 get_free_hugepages() < bytes / page_size) { 453 printf("skip: Skipping userfaultfd... not enough hugepages\n"); 454 return KSFT_SKIP; 455 } 456 457 nr_cpus = sysconf(_SC_NPROCESSORS_ONLN); 458 if (nr_cpus > 32) { 459 /* Don't let calculation below go to zero. */ 460 ksft_print_msg("_SC_NPROCESSORS_ONLN (%lu) too large, capping nr_threads to 32\n", 461 nr_cpus); 462 nr_parallel = 32; 463 } else { 464 nr_parallel = nr_cpus; 465 } 466 467 nr_pages_per_cpu = bytes / page_size / nr_parallel; 468 if (!nr_pages_per_cpu) { 469 _err("pages_per_cpu = 0, cannot test (%lu / %lu / %lu)", 470 bytes, page_size, nr_parallel); 471 usage(); 472 } 473 474 bounces = atoi(argv[3]); 475 if (bounces <= 0) { 476 _err("invalid bounces"); 477 usage(); 478 } 479 nr_pages = nr_pages_per_cpu * nr_parallel; 480 481 printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n", 482 nr_pages, nr_pages_per_cpu); 483 return userfaultfd_stress(); 484 } 485 486 #else /* __NR_userfaultfd */ 487 488 #warning "missing __NR_userfaultfd definition" 489 490 int main(void) 491 { 492 printf("skip: Skipping userfaultfd test (missing __NR_userfaultfd)\n"); 493 return KSFT_SKIP; 494 } 495 496 #endif /* __NR_userfaultfd */ 497