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