1 /* 2 * BTS PMU driver for perf 3 * Copyright (c) 2013-2014, Intel Corporation. 4 * 5 * This program is free software; you can redistribute it and/or modify it 6 * under the terms and conditions of the GNU General Public License, 7 * version 2, as published by the Free Software Foundation. 8 * 9 * This program is distributed in the hope it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for 12 * more details. 13 */ 14 15 #undef DEBUG 16 17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 18 19 #include <linux/bitops.h> 20 #include <linux/types.h> 21 #include <linux/slab.h> 22 #include <linux/debugfs.h> 23 #include <linux/device.h> 24 #include <linux/coredump.h> 25 26 #include <asm-generic/sizes.h> 27 #include <asm/perf_event.h> 28 29 #include "../perf_event.h" 30 31 struct bts_ctx { 32 struct perf_output_handle handle; 33 struct debug_store ds_back; 34 int started; 35 }; 36 37 static DEFINE_PER_CPU(struct bts_ctx, bts_ctx); 38 39 #define BTS_RECORD_SIZE 24 40 #define BTS_SAFETY_MARGIN 4080 41 42 struct bts_phys { 43 struct page *page; 44 unsigned long size; 45 unsigned long offset; 46 unsigned long displacement; 47 }; 48 49 struct bts_buffer { 50 size_t real_size; /* multiple of BTS_RECORD_SIZE */ 51 unsigned int nr_pages; 52 unsigned int nr_bufs; 53 unsigned int cur_buf; 54 bool snapshot; 55 local_t data_size; 56 local_t lost; 57 local_t head; 58 unsigned long end; 59 void **data_pages; 60 struct bts_phys buf[0]; 61 }; 62 63 struct pmu bts_pmu; 64 65 static size_t buf_size(struct page *page) 66 { 67 return 1 << (PAGE_SHIFT + page_private(page)); 68 } 69 70 static void * 71 bts_buffer_setup_aux(int cpu, void **pages, int nr_pages, bool overwrite) 72 { 73 struct bts_buffer *buf; 74 struct page *page; 75 int node = (cpu == -1) ? cpu : cpu_to_node(cpu); 76 unsigned long offset; 77 size_t size = nr_pages << PAGE_SHIFT; 78 int pg, nbuf, pad; 79 80 /* count all the high order buffers */ 81 for (pg = 0, nbuf = 0; pg < nr_pages;) { 82 page = virt_to_page(pages[pg]); 83 if (WARN_ON_ONCE(!PagePrivate(page) && nr_pages > 1)) 84 return NULL; 85 pg += 1 << page_private(page); 86 nbuf++; 87 } 88 89 /* 90 * to avoid interrupts in overwrite mode, only allow one physical 91 */ 92 if (overwrite && nbuf > 1) 93 return NULL; 94 95 buf = kzalloc_node(offsetof(struct bts_buffer, buf[nbuf]), GFP_KERNEL, node); 96 if (!buf) 97 return NULL; 98 99 buf->nr_pages = nr_pages; 100 buf->nr_bufs = nbuf; 101 buf->snapshot = overwrite; 102 buf->data_pages = pages; 103 buf->real_size = size - size % BTS_RECORD_SIZE; 104 105 for (pg = 0, nbuf = 0, offset = 0, pad = 0; nbuf < buf->nr_bufs; nbuf++) { 106 unsigned int __nr_pages; 107 108 page = virt_to_page(pages[pg]); 109 __nr_pages = PagePrivate(page) ? 1 << page_private(page) : 1; 110 buf->buf[nbuf].page = page; 111 buf->buf[nbuf].offset = offset; 112 buf->buf[nbuf].displacement = (pad ? BTS_RECORD_SIZE - pad : 0); 113 buf->buf[nbuf].size = buf_size(page) - buf->buf[nbuf].displacement; 114 pad = buf->buf[nbuf].size % BTS_RECORD_SIZE; 115 buf->buf[nbuf].size -= pad; 116 117 pg += __nr_pages; 118 offset += __nr_pages << PAGE_SHIFT; 119 } 120 121 return buf; 122 } 123 124 static void bts_buffer_free_aux(void *data) 125 { 126 kfree(data); 127 } 128 129 static unsigned long bts_buffer_offset(struct bts_buffer *buf, unsigned int idx) 130 { 131 return buf->buf[idx].offset + buf->buf[idx].displacement; 132 } 133 134 static void 135 bts_config_buffer(struct bts_buffer *buf) 136 { 137 int cpu = raw_smp_processor_id(); 138 struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds; 139 struct bts_phys *phys = &buf->buf[buf->cur_buf]; 140 unsigned long index, thresh = 0, end = phys->size; 141 struct page *page = phys->page; 142 143 index = local_read(&buf->head); 144 145 if (!buf->snapshot) { 146 if (buf->end < phys->offset + buf_size(page)) 147 end = buf->end - phys->offset - phys->displacement; 148 149 index -= phys->offset + phys->displacement; 150 151 if (end - index > BTS_SAFETY_MARGIN) 152 thresh = end - BTS_SAFETY_MARGIN; 153 else if (end - index > BTS_RECORD_SIZE) 154 thresh = end - BTS_RECORD_SIZE; 155 else 156 thresh = end; 157 } 158 159 ds->bts_buffer_base = (u64)(long)page_address(page) + phys->displacement; 160 ds->bts_index = ds->bts_buffer_base + index; 161 ds->bts_absolute_maximum = ds->bts_buffer_base + end; 162 ds->bts_interrupt_threshold = !buf->snapshot 163 ? ds->bts_buffer_base + thresh 164 : ds->bts_absolute_maximum + BTS_RECORD_SIZE; 165 } 166 167 static void bts_buffer_pad_out(struct bts_phys *phys, unsigned long head) 168 { 169 unsigned long index = head - phys->offset; 170 171 memset(page_address(phys->page) + index, 0, phys->size - index); 172 } 173 174 static void bts_update(struct bts_ctx *bts) 175 { 176 int cpu = raw_smp_processor_id(); 177 struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds; 178 struct bts_buffer *buf = perf_get_aux(&bts->handle); 179 unsigned long index = ds->bts_index - ds->bts_buffer_base, old, head; 180 181 if (!buf) 182 return; 183 184 head = index + bts_buffer_offset(buf, buf->cur_buf); 185 old = local_xchg(&buf->head, head); 186 187 if (!buf->snapshot) { 188 if (old == head) 189 return; 190 191 if (ds->bts_index >= ds->bts_absolute_maximum) 192 local_inc(&buf->lost); 193 194 /* 195 * old and head are always in the same physical buffer, so we 196 * can subtract them to get the data size. 197 */ 198 local_add(head - old, &buf->data_size); 199 } else { 200 local_set(&buf->data_size, head); 201 } 202 } 203 204 static int 205 bts_buffer_reset(struct bts_buffer *buf, struct perf_output_handle *handle); 206 207 static void __bts_event_start(struct perf_event *event) 208 { 209 struct bts_ctx *bts = this_cpu_ptr(&bts_ctx); 210 struct bts_buffer *buf = perf_get_aux(&bts->handle); 211 u64 config = 0; 212 213 if (!buf->snapshot) 214 config |= ARCH_PERFMON_EVENTSEL_INT; 215 if (!event->attr.exclude_kernel) 216 config |= ARCH_PERFMON_EVENTSEL_OS; 217 if (!event->attr.exclude_user) 218 config |= ARCH_PERFMON_EVENTSEL_USR; 219 220 bts_config_buffer(buf); 221 222 /* 223 * local barrier to make sure that ds configuration made it 224 * before we enable BTS 225 */ 226 wmb(); 227 228 intel_pmu_enable_bts(config); 229 230 } 231 232 static void bts_event_start(struct perf_event *event, int flags) 233 { 234 struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); 235 struct bts_ctx *bts = this_cpu_ptr(&bts_ctx); 236 struct bts_buffer *buf; 237 238 buf = perf_aux_output_begin(&bts->handle, event); 239 if (!buf) 240 goto fail_stop; 241 242 if (bts_buffer_reset(buf, &bts->handle)) 243 goto fail_end_stop; 244 245 bts->ds_back.bts_buffer_base = cpuc->ds->bts_buffer_base; 246 bts->ds_back.bts_absolute_maximum = cpuc->ds->bts_absolute_maximum; 247 bts->ds_back.bts_interrupt_threshold = cpuc->ds->bts_interrupt_threshold; 248 249 event->hw.itrace_started = 1; 250 event->hw.state = 0; 251 252 __bts_event_start(event); 253 254 /* PMI handler: this counter is running and likely generating PMIs */ 255 ACCESS_ONCE(bts->started) = 1; 256 257 return; 258 259 fail_end_stop: 260 perf_aux_output_end(&bts->handle, 0, false); 261 262 fail_stop: 263 event->hw.state = PERF_HES_STOPPED; 264 } 265 266 static void __bts_event_stop(struct perf_event *event) 267 { 268 /* 269 * No extra synchronization is mandated by the documentation to have 270 * BTS data stores globally visible. 271 */ 272 intel_pmu_disable_bts(); 273 274 if (event->hw.state & PERF_HES_STOPPED) 275 return; 276 277 ACCESS_ONCE(event->hw.state) |= PERF_HES_STOPPED; 278 } 279 280 static void bts_event_stop(struct perf_event *event, int flags) 281 { 282 struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); 283 struct bts_ctx *bts = this_cpu_ptr(&bts_ctx); 284 struct bts_buffer *buf = perf_get_aux(&bts->handle); 285 286 /* PMI handler: don't restart this counter */ 287 ACCESS_ONCE(bts->started) = 0; 288 289 __bts_event_stop(event); 290 291 if (flags & PERF_EF_UPDATE) { 292 bts_update(bts); 293 294 if (buf) { 295 if (buf->snapshot) 296 bts->handle.head = 297 local_xchg(&buf->data_size, 298 buf->nr_pages << PAGE_SHIFT); 299 perf_aux_output_end(&bts->handle, local_xchg(&buf->data_size, 0), 300 !!local_xchg(&buf->lost, 0)); 301 } 302 303 cpuc->ds->bts_index = bts->ds_back.bts_buffer_base; 304 cpuc->ds->bts_buffer_base = bts->ds_back.bts_buffer_base; 305 cpuc->ds->bts_absolute_maximum = bts->ds_back.bts_absolute_maximum; 306 cpuc->ds->bts_interrupt_threshold = bts->ds_back.bts_interrupt_threshold; 307 } 308 } 309 310 void intel_bts_enable_local(void) 311 { 312 struct bts_ctx *bts = this_cpu_ptr(&bts_ctx); 313 314 if (bts->handle.event && bts->started) 315 __bts_event_start(bts->handle.event); 316 } 317 318 void intel_bts_disable_local(void) 319 { 320 struct bts_ctx *bts = this_cpu_ptr(&bts_ctx); 321 322 if (bts->handle.event) 323 __bts_event_stop(bts->handle.event); 324 } 325 326 static int 327 bts_buffer_reset(struct bts_buffer *buf, struct perf_output_handle *handle) 328 { 329 unsigned long head, space, next_space, pad, gap, skip, wakeup; 330 unsigned int next_buf; 331 struct bts_phys *phys, *next_phys; 332 int ret; 333 334 if (buf->snapshot) 335 return 0; 336 337 head = handle->head & ((buf->nr_pages << PAGE_SHIFT) - 1); 338 if (WARN_ON_ONCE(head != local_read(&buf->head))) 339 return -EINVAL; 340 341 phys = &buf->buf[buf->cur_buf]; 342 space = phys->offset + phys->displacement + phys->size - head; 343 pad = space; 344 if (space > handle->size) { 345 space = handle->size; 346 space -= space % BTS_RECORD_SIZE; 347 } 348 if (space <= BTS_SAFETY_MARGIN) { 349 /* See if next phys buffer has more space */ 350 next_buf = buf->cur_buf + 1; 351 if (next_buf >= buf->nr_bufs) 352 next_buf = 0; 353 next_phys = &buf->buf[next_buf]; 354 gap = buf_size(phys->page) - phys->displacement - phys->size + 355 next_phys->displacement; 356 skip = pad + gap; 357 if (handle->size >= skip) { 358 next_space = next_phys->size; 359 if (next_space + skip > handle->size) { 360 next_space = handle->size - skip; 361 next_space -= next_space % BTS_RECORD_SIZE; 362 } 363 if (next_space > space || !space) { 364 if (pad) 365 bts_buffer_pad_out(phys, head); 366 ret = perf_aux_output_skip(handle, skip); 367 if (ret) 368 return ret; 369 /* Advance to next phys buffer */ 370 phys = next_phys; 371 space = next_space; 372 head = phys->offset + phys->displacement; 373 /* 374 * After this, cur_buf and head won't match ds 375 * anymore, so we must not be racing with 376 * bts_update(). 377 */ 378 buf->cur_buf = next_buf; 379 local_set(&buf->head, head); 380 } 381 } 382 } 383 384 /* Don't go far beyond wakeup watermark */ 385 wakeup = BTS_SAFETY_MARGIN + BTS_RECORD_SIZE + handle->wakeup - 386 handle->head; 387 if (space > wakeup) { 388 space = wakeup; 389 space -= space % BTS_RECORD_SIZE; 390 } 391 392 buf->end = head + space; 393 394 /* 395 * If we have no space, the lost notification would have been sent when 396 * we hit absolute_maximum - see bts_update() 397 */ 398 if (!space) 399 return -ENOSPC; 400 401 return 0; 402 } 403 404 int intel_bts_interrupt(void) 405 { 406 struct bts_ctx *bts = this_cpu_ptr(&bts_ctx); 407 struct perf_event *event = bts->handle.event; 408 struct bts_buffer *buf; 409 s64 old_head; 410 int err; 411 412 if (!event || !bts->started) 413 return 0; 414 415 buf = perf_get_aux(&bts->handle); 416 /* 417 * Skip snapshot counters: they don't use the interrupt, but 418 * there's no other way of telling, because the pointer will 419 * keep moving 420 */ 421 if (!buf || buf->snapshot) 422 return 0; 423 424 old_head = local_read(&buf->head); 425 bts_update(bts); 426 427 /* no new data */ 428 if (old_head == local_read(&buf->head)) 429 return 0; 430 431 perf_aux_output_end(&bts->handle, local_xchg(&buf->data_size, 0), 432 !!local_xchg(&buf->lost, 0)); 433 434 buf = perf_aux_output_begin(&bts->handle, event); 435 if (!buf) 436 return 1; 437 438 err = bts_buffer_reset(buf, &bts->handle); 439 if (err) 440 perf_aux_output_end(&bts->handle, 0, false); 441 442 return 1; 443 } 444 445 static void bts_event_del(struct perf_event *event, int mode) 446 { 447 bts_event_stop(event, PERF_EF_UPDATE); 448 } 449 450 static int bts_event_add(struct perf_event *event, int mode) 451 { 452 struct bts_ctx *bts = this_cpu_ptr(&bts_ctx); 453 struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); 454 struct hw_perf_event *hwc = &event->hw; 455 456 event->hw.state = PERF_HES_STOPPED; 457 458 if (test_bit(INTEL_PMC_IDX_FIXED_BTS, cpuc->active_mask)) 459 return -EBUSY; 460 461 if (bts->handle.event) 462 return -EBUSY; 463 464 if (mode & PERF_EF_START) { 465 bts_event_start(event, 0); 466 if (hwc->state & PERF_HES_STOPPED) 467 return -EINVAL; 468 } 469 470 return 0; 471 } 472 473 static void bts_event_destroy(struct perf_event *event) 474 { 475 x86_release_hardware(); 476 x86_del_exclusive(x86_lbr_exclusive_bts); 477 } 478 479 static int bts_event_init(struct perf_event *event) 480 { 481 int ret; 482 483 if (event->attr.type != bts_pmu.type) 484 return -ENOENT; 485 486 if (x86_add_exclusive(x86_lbr_exclusive_bts)) 487 return -EBUSY; 488 489 /* 490 * BTS leaks kernel addresses even when CPL0 tracing is 491 * disabled, so disallow intel_bts driver for unprivileged 492 * users on paranoid systems since it provides trace data 493 * to the user in a zero-copy fashion. 494 * 495 * Note that the default paranoia setting permits unprivileged 496 * users to profile the kernel. 497 */ 498 if (event->attr.exclude_kernel && perf_paranoid_kernel() && 499 !capable(CAP_SYS_ADMIN)) 500 return -EACCES; 501 502 ret = x86_reserve_hardware(); 503 if (ret) { 504 x86_del_exclusive(x86_lbr_exclusive_bts); 505 return ret; 506 } 507 508 event->destroy = bts_event_destroy; 509 510 return 0; 511 } 512 513 static void bts_event_read(struct perf_event *event) 514 { 515 } 516 517 static __init int bts_init(void) 518 { 519 if (!boot_cpu_has(X86_FEATURE_DTES64) || !x86_pmu.bts) 520 return -ENODEV; 521 522 bts_pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG | PERF_PMU_CAP_ITRACE; 523 bts_pmu.task_ctx_nr = perf_sw_context; 524 bts_pmu.event_init = bts_event_init; 525 bts_pmu.add = bts_event_add; 526 bts_pmu.del = bts_event_del; 527 bts_pmu.start = bts_event_start; 528 bts_pmu.stop = bts_event_stop; 529 bts_pmu.read = bts_event_read; 530 bts_pmu.setup_aux = bts_buffer_setup_aux; 531 bts_pmu.free_aux = bts_buffer_free_aux; 532 533 return perf_pmu_register(&bts_pmu, "intel_bts", -1); 534 } 535 arch_initcall(bts_init); 536