1 /*===- GCDAProfiling.c - Support library for GCDA file emission -----------===*\
2 |*
3 |* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 |* See https://llvm.org/LICENSE.txt for license information.
5 |* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 |*
7 |*===----------------------------------------------------------------------===*|
8 |*
9 |* This file implements the call back routines for the gcov profiling
10 |* instrumentation pass. Link against this library when running code through
11 |* the -insert-gcov-profiling LLVM pass.
12 |*
13 |* We emit files in a corrupt version of GCOV's "gcda" file format. These files
14 |* are only close enough that LCOV will happily parse them. Anything that lcov
15 |* ignores is missing.
16 |*
17 |* TODO: gcov is multi-process safe by having each exit open the existing file
18 |* and append to it. We'd like to achieve that and be thread-safe too.
19 |*
20 \*===----------------------------------------------------------------------===*/
21
22 #if !defined(__Fuchsia__)
23
24 #include <errno.h>
25 #include <fcntl.h>
26 #include <stdint.h>
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <string.h>
30
31 #if defined(_WIN32)
32 #define WIN32_LEAN_AND_MEAN
33 #include <windows.h>
34 #include "WindowsMMap.h"
35 #else
36 #include <sys/file.h>
37 #include <sys/mman.h>
38 #include <sys/types.h>
39 #include <unistd.h>
40 #endif
41
42 #include "InstrProfiling.h"
43 #include "InstrProfilingUtil.h"
44
45 /* #define DEBUG_GCDAPROFILING */
46
47 enum {
48 GCOV_DATA_MAGIC = 0x67636461, // "gcda"
49
50 GCOV_TAG_FUNCTION = 0x01000000,
51 GCOV_TAG_COUNTER_ARCS = 0x01a10000,
52 // GCOV_TAG_OBJECT_SUMMARY superseded GCOV_TAG_PROGRAM_SUMMARY in GCC 9.
53 GCOV_TAG_OBJECT_SUMMARY = 0xa1000000,
54 GCOV_TAG_PROGRAM_SUMMARY = 0xa3000000,
55 };
56
57 /*
58 * --- GCOV file format I/O primitives ---
59 */
60
61 /*
62 * The current file name we're outputting. Used primarily for error logging.
63 */
64 static char *filename = NULL;
65
66 /*
67 * The current file we're outputting.
68 */
69 static FILE *output_file = NULL;
70
71 /*
72 * Buffer that we write things into.
73 */
74 #define WRITE_BUFFER_SIZE (128 * 1024)
75 static unsigned char *write_buffer = NULL;
76 static uint64_t cur_buffer_size = 0;
77 static uint64_t cur_pos = 0;
78 static uint64_t file_size = 0;
79 static int new_file = 0;
80 static int gcov_version;
81 #if defined(_WIN32)
82 static HANDLE mmap_handle = NULL;
83 #endif
84 static int fd = -1;
85
86 typedef void (*fn_ptr)();
87
88 typedef void* dynamic_object_id;
89 // The address of this variable identifies a given dynamic object.
90 static dynamic_object_id current_id;
91 #define CURRENT_ID (¤t_id)
92
93 struct fn_node {
94 dynamic_object_id id;
95 fn_ptr fn;
96 struct fn_node* next;
97 };
98
99 struct fn_list {
100 struct fn_node *head, *tail;
101 };
102
103 /*
104 * A list of functions to write out the data, shared between all dynamic objects.
105 */
106 struct fn_list writeout_fn_list;
107
108 /*
109 * A list of reset functions, shared between all dynamic objects.
110 */
111 struct fn_list reset_fn_list;
112
fn_list_insert(struct fn_list * list,fn_ptr fn)113 static void fn_list_insert(struct fn_list* list, fn_ptr fn) {
114 struct fn_node* new_node = malloc(sizeof(struct fn_node));
115 new_node->fn = fn;
116 new_node->next = NULL;
117 new_node->id = CURRENT_ID;
118
119 if (!list->head) {
120 list->head = list->tail = new_node;
121 } else {
122 list->tail->next = new_node;
123 list->tail = new_node;
124 }
125 }
126
fn_list_remove(struct fn_list * list)127 static void fn_list_remove(struct fn_list* list) {
128 struct fn_node* curr = list->head;
129 struct fn_node* prev = NULL;
130 struct fn_node* next = NULL;
131
132 while (curr) {
133 next = curr->next;
134
135 if (curr->id == CURRENT_ID) {
136 if (curr == list->head) {
137 list->head = next;
138 }
139
140 if (curr == list->tail) {
141 list->tail = prev;
142 }
143
144 if (prev) {
145 prev->next = next;
146 }
147
148 free(curr);
149 } else {
150 prev = curr;
151 }
152
153 curr = next;
154 }
155 }
156
resize_write_buffer(uint64_t size)157 static void resize_write_buffer(uint64_t size) {
158 if (!new_file) return;
159 size += cur_pos;
160 if (size <= cur_buffer_size) return;
161 size = (size - 1) / WRITE_BUFFER_SIZE + 1;
162 size *= WRITE_BUFFER_SIZE;
163 write_buffer = realloc(write_buffer, size);
164 cur_buffer_size = size;
165 }
166
write_bytes(const char * s,size_t len)167 static void write_bytes(const char *s, size_t len) {
168 resize_write_buffer(len);
169 memcpy(&write_buffer[cur_pos], s, len);
170 cur_pos += len;
171 }
172
write_32bit_value(uint32_t i)173 static void write_32bit_value(uint32_t i) {
174 write_bytes((char*)&i, 4);
175 }
176
write_64bit_value(uint64_t i)177 static void write_64bit_value(uint64_t i) {
178 // GCOV uses a lo-/hi-word format even on big-endian systems.
179 // See also GCOVBuffer::readInt64 in LLVM.
180 uint32_t lo = (uint32_t) i;
181 uint32_t hi = (uint32_t) (i >> 32);
182 write_32bit_value(lo);
183 write_32bit_value(hi);
184 }
185
read_32bit_value()186 static uint32_t read_32bit_value() {
187 uint32_t val;
188
189 if (new_file)
190 return (uint32_t)-1;
191
192 val = *(uint32_t*)&write_buffer[cur_pos];
193 cur_pos += 4;
194 return val;
195 }
196
read_64bit_value()197 static uint64_t read_64bit_value() {
198 // GCOV uses a lo-/hi-word format even on big-endian systems.
199 // See also GCOVBuffer::readInt64 in LLVM.
200 uint32_t lo = read_32bit_value();
201 uint32_t hi = read_32bit_value();
202 return ((uint64_t)hi << 32) | ((uint64_t)lo);
203 }
204
mangle_filename(const char * orig_filename)205 static char *mangle_filename(const char *orig_filename) {
206 char *new_filename;
207 size_t prefix_len;
208 int prefix_strip;
209 const char *prefix = lprofGetPathPrefix(&prefix_strip, &prefix_len);
210
211 if (prefix == NULL)
212 return strdup(orig_filename);
213
214 new_filename = malloc(prefix_len + 1 + strlen(orig_filename) + 1);
215 lprofApplyPathPrefix(new_filename, orig_filename, prefix, prefix_len,
216 prefix_strip);
217
218 return new_filename;
219 }
220
map_file()221 static int map_file() {
222 fseek(output_file, 0L, SEEK_END);
223 file_size = ftell(output_file);
224
225 /* A size of 0 means the file has been created just now (possibly by another
226 * process in lock-after-open race condition). No need to mmap. */
227 if (file_size == 0)
228 return -1;
229
230 #if defined(_WIN32)
231 HANDLE mmap_fd;
232 if (fd == -1)
233 mmap_fd = INVALID_HANDLE_VALUE;
234 else
235 mmap_fd = (HANDLE)_get_osfhandle(fd);
236
237 mmap_handle = CreateFileMapping(mmap_fd, NULL, PAGE_READWRITE, DWORD_HI(file_size), DWORD_LO(file_size), NULL);
238 if (mmap_handle == NULL) {
239 fprintf(stderr, "profiling: %s: cannot create file mapping: %lu\n",
240 filename, GetLastError());
241 return -1;
242 }
243
244 write_buffer = MapViewOfFile(mmap_handle, FILE_MAP_WRITE, 0, 0, file_size);
245 if (write_buffer == NULL) {
246 fprintf(stderr, "profiling: %s: cannot map: %lu\n", filename,
247 GetLastError());
248 CloseHandle(mmap_handle);
249 return -1;
250 }
251 #else
252 write_buffer = mmap(0, file_size, PROT_READ | PROT_WRITE,
253 MAP_FILE | MAP_SHARED, fd, 0);
254 if (write_buffer == (void *)-1) {
255 int errnum = errno;
256 fprintf(stderr, "profiling: %s: cannot map: %s\n", filename,
257 strerror(errnum));
258 return -1;
259 }
260 #endif
261
262 return 0;
263 }
264
unmap_file()265 static void unmap_file() {
266 #if defined(_WIN32)
267 if (!FlushViewOfFile(write_buffer, file_size)) {
268 fprintf(stderr, "profiling: %s: cannot flush mapped view: %lu\n", filename,
269 GetLastError());
270 }
271
272 if (!UnmapViewOfFile(write_buffer)) {
273 fprintf(stderr, "profiling: %s: cannot unmap mapped view: %lu\n", filename,
274 GetLastError());
275 }
276
277 if (!CloseHandle(mmap_handle)) {
278 fprintf(stderr, "profiling: %s: cannot close file mapping handle: %lu\n",
279 filename, GetLastError());
280 }
281
282 mmap_handle = NULL;
283 #else
284 if (munmap(write_buffer, file_size) == -1) {
285 int errnum = errno;
286 fprintf(stderr, "profiling: %s: cannot munmap: %s\n", filename,
287 strerror(errnum));
288 }
289 #endif
290
291 write_buffer = NULL;
292 file_size = 0;
293 }
294
295 /*
296 * --- LLVM line counter API ---
297 */
298
299 /* A file in this case is a translation unit. Each .o file built with line
300 * profiling enabled will emit to a different file. Only one file may be
301 * started at a time.
302 */
303 COMPILER_RT_VISIBILITY
llvm_gcda_start_file(const char * orig_filename,uint32_t version,uint32_t checksum)304 void llvm_gcda_start_file(const char *orig_filename, uint32_t version,
305 uint32_t checksum) {
306 const char *mode = "r+b";
307 filename = mangle_filename(orig_filename);
308
309 /* Try just opening the file. */
310 fd = open(filename, O_RDWR | O_BINARY);
311
312 if (fd == -1) {
313 /* Try creating the file. */
314 fd = open(filename, O_RDWR | O_CREAT | O_EXCL | O_BINARY, 0644);
315 if (fd != -1) {
316 mode = "w+b";
317 } else {
318 /* Try creating the directories first then opening the file. */
319 __llvm_profile_recursive_mkdir(filename);
320 fd = open(filename, O_RDWR | O_CREAT | O_EXCL | O_BINARY, 0644);
321 if (fd != -1) {
322 mode = "w+b";
323 } else {
324 /* Another process may have created the file just now.
325 * Try opening it without O_CREAT and O_EXCL. */
326 fd = open(filename, O_RDWR | O_BINARY);
327 if (fd == -1) {
328 /* Bah! It's hopeless. */
329 int errnum = errno;
330 fprintf(stderr, "profiling: %s: cannot open: %s\n", filename,
331 strerror(errnum));
332 return;
333 }
334 }
335 }
336 }
337
338 /* Try to flock the file to serialize concurrent processes writing out to the
339 * same GCDA. This can fail if the filesystem doesn't support it, but in that
340 * case we'll just carry on with the old racy behaviour and hope for the best.
341 */
342 lprofLockFd(fd);
343 output_file = fdopen(fd, mode);
344
345 /* Initialize the write buffer. */
346 new_file = 0;
347 write_buffer = NULL;
348 cur_buffer_size = 0;
349 cur_pos = 0;
350
351 if (map_file() == -1) {
352 /* The file has been created just now (file_size == 0) or mmap failed
353 * unexpectedly. In the latter case, try to recover by clobbering. */
354 new_file = 1;
355 write_buffer = NULL;
356 resize_write_buffer(WRITE_BUFFER_SIZE);
357 memset(write_buffer, 0, WRITE_BUFFER_SIZE);
358 }
359
360 /* gcda file, version, stamp checksum. */
361 {
362 uint8_t c3 = version >> 24;
363 uint8_t c2 = (version >> 16) & 255;
364 uint8_t c1 = (version >> 8) & 255;
365 gcov_version = c3 >= 'A' ? (c3 - 'A') * 100 + (c2 - '0') * 10 + c1 - '0'
366 : (c3 - '0') * 10 + c1 - '0';
367 }
368 write_32bit_value(GCOV_DATA_MAGIC);
369 write_32bit_value(version);
370 write_32bit_value(checksum);
371
372 #ifdef DEBUG_GCDAPROFILING
373 fprintf(stderr, "llvmgcda: [%s]\n", orig_filename);
374 #endif
375 }
376
377 COMPILER_RT_VISIBILITY
llvm_gcda_emit_function(uint32_t ident,uint32_t func_checksum,uint32_t cfg_checksum)378 void llvm_gcda_emit_function(uint32_t ident, uint32_t func_checksum,
379 uint32_t cfg_checksum) {
380 uint32_t len = 2;
381 int use_extra_checksum = gcov_version >= 47;
382
383 if (use_extra_checksum)
384 len++;
385 #ifdef DEBUG_GCDAPROFILING
386 fprintf(stderr, "llvmgcda: function id=0x%08x\n", ident);
387 #endif
388 if (!output_file) return;
389
390 /* function tag */
391 write_32bit_value(GCOV_TAG_FUNCTION);
392 write_32bit_value(len);
393 write_32bit_value(ident);
394 write_32bit_value(func_checksum);
395 if (use_extra_checksum)
396 write_32bit_value(cfg_checksum);
397 }
398
399 COMPILER_RT_VISIBILITY
llvm_gcda_emit_arcs(uint32_t num_counters,uint64_t * counters)400 void llvm_gcda_emit_arcs(uint32_t num_counters, uint64_t *counters) {
401 uint32_t i;
402 uint64_t *old_ctrs = NULL;
403 uint32_t val = 0;
404 uint64_t save_cur_pos = cur_pos;
405
406 if (!output_file) return;
407
408 val = read_32bit_value();
409
410 if (val != (uint32_t)-1) {
411 /* There are counters present in the file. Merge them. */
412 if (val != GCOV_TAG_COUNTER_ARCS) {
413 fprintf(stderr, "profiling: %s: cannot merge previous GCDA file: "
414 "corrupt arc tag (0x%08x)\n",
415 filename, val);
416 return;
417 }
418
419 val = read_32bit_value();
420 if (val == (uint32_t)-1 || val / 2 != num_counters) {
421 fprintf(stderr, "profiling: %s: cannot merge previous GCDA file: "
422 "mismatched number of counters (%d)\n",
423 filename, val);
424 return;
425 }
426
427 old_ctrs = malloc(sizeof(uint64_t) * num_counters);
428 for (i = 0; i < num_counters; ++i)
429 old_ctrs[i] = read_64bit_value();
430 }
431
432 cur_pos = save_cur_pos;
433
434 /* Counter #1 (arcs) tag */
435 write_32bit_value(GCOV_TAG_COUNTER_ARCS);
436 write_32bit_value(num_counters * 2);
437 for (i = 0; i < num_counters; ++i) {
438 counters[i] += (old_ctrs ? old_ctrs[i] : 0);
439 write_64bit_value(counters[i]);
440 }
441
442 free(old_ctrs);
443
444 #ifdef DEBUG_GCDAPROFILING
445 fprintf(stderr, "llvmgcda: %u arcs\n", num_counters);
446 for (i = 0; i < num_counters; ++i)
447 fprintf(stderr, "llvmgcda: %llu\n", (unsigned long long)counters[i]);
448 #endif
449 }
450
451 COMPILER_RT_VISIBILITY
llvm_gcda_summary_info()452 void llvm_gcda_summary_info() {
453 uint32_t runs = 1;
454 static uint32_t run_counted = 0; // We only want to increase the run count once.
455 uint32_t val = 0;
456 uint64_t save_cur_pos = cur_pos;
457
458 if (!output_file) return;
459
460 val = read_32bit_value();
461
462 if (val != (uint32_t)-1) {
463 /* There are counters present in the file. Merge them. */
464 uint32_t gcov_tag =
465 gcov_version >= 90 ? GCOV_TAG_OBJECT_SUMMARY : GCOV_TAG_PROGRAM_SUMMARY;
466 if (val != gcov_tag) {
467 fprintf(stderr,
468 "profiling: %s: cannot merge previous run count: "
469 "corrupt object tag (0x%08x)\n",
470 filename, val);
471 return;
472 }
473
474 val = read_32bit_value(); /* length */
475 uint32_t prev_runs;
476 if (gcov_version < 90) {
477 read_32bit_value();
478 read_32bit_value();
479 prev_runs = read_32bit_value();
480 } else {
481 prev_runs = read_32bit_value();
482 read_32bit_value();
483 }
484 for (uint32_t i = gcov_version < 90 ? 3 : 2; i < val; ++i)
485 read_32bit_value();
486 /* Add previous run count to new counter, if not already counted before. */
487 runs = run_counted ? prev_runs : prev_runs + 1;
488 }
489
490 cur_pos = save_cur_pos;
491
492 if (gcov_version >= 90) {
493 write_32bit_value(GCOV_TAG_OBJECT_SUMMARY);
494 write_32bit_value(2);
495 write_32bit_value(runs);
496 write_32bit_value(0); // sum_max
497 } else {
498 // Before gcov 4.8 (r190952), GCOV_TAG_SUMMARY_LENGTH was 9. r190952 set
499 // GCOV_TAG_SUMMARY_LENGTH to 22. We simply use the smallest length which
500 // can make gcov read "Runs:".
501 write_32bit_value(GCOV_TAG_PROGRAM_SUMMARY);
502 write_32bit_value(3);
503 write_32bit_value(0);
504 write_32bit_value(0);
505 write_32bit_value(runs);
506 }
507
508 run_counted = 1;
509
510 #ifdef DEBUG_GCDAPROFILING
511 fprintf(stderr, "llvmgcda: %u runs\n", runs);
512 #endif
513 }
514
515 COMPILER_RT_VISIBILITY
llvm_gcda_end_file()516 void llvm_gcda_end_file() {
517 /* Write out EOF record. */
518 if (output_file) {
519 write_bytes("\0\0\0\0\0\0\0\0", 8);
520
521 if (new_file) {
522 fwrite(write_buffer, cur_pos, 1, output_file);
523 free(write_buffer);
524 } else {
525 unmap_file();
526 }
527
528 fflush(output_file);
529 lprofUnlockFd(fd);
530 fclose(output_file);
531 output_file = NULL;
532 write_buffer = NULL;
533 }
534 free(filename);
535
536 #ifdef DEBUG_GCDAPROFILING
537 fprintf(stderr, "llvmgcda: -----\n");
538 #endif
539 }
540
541 COMPILER_RT_VISIBILITY
llvm_register_writeout_function(fn_ptr fn)542 void llvm_register_writeout_function(fn_ptr fn) {
543 fn_list_insert(&writeout_fn_list, fn);
544 }
545
546 COMPILER_RT_VISIBILITY
llvm_writeout_files(void)547 void llvm_writeout_files(void) {
548 struct fn_node *curr = writeout_fn_list.head;
549
550 while (curr) {
551 if (curr->id == CURRENT_ID) {
552 curr->fn();
553 }
554 curr = curr->next;
555 }
556 }
557
558 #ifndef _WIN32
559 // __attribute__((destructor)) and destructors whose priorities are greater than
560 // 100 run before this function and can thus be tracked. The priority is
561 // compatible with GCC 7 onwards.
562 #if __GNUC__ >= 9
563 #pragma GCC diagnostic ignored "-Wprio-ctor-dtor"
564 #endif
565 __attribute__((destructor(100)))
566 #endif
llvm_writeout_and_clear(void)567 static void llvm_writeout_and_clear(void) {
568 llvm_writeout_files();
569 fn_list_remove(&writeout_fn_list);
570 }
571
572 COMPILER_RT_VISIBILITY
llvm_register_reset_function(fn_ptr fn)573 void llvm_register_reset_function(fn_ptr fn) {
574 fn_list_insert(&reset_fn_list, fn);
575 }
576
577 COMPILER_RT_VISIBILITY
llvm_delete_reset_function_list(void)578 void llvm_delete_reset_function_list(void) { fn_list_remove(&reset_fn_list); }
579
580 COMPILER_RT_VISIBILITY
llvm_reset_counters(void)581 void llvm_reset_counters(void) {
582 struct fn_node *curr = reset_fn_list.head;
583
584 while (curr) {
585 if (curr->id == CURRENT_ID) {
586 curr->fn();
587 }
588 curr = curr->next;
589 }
590 }
591
592 #if !defined(_WIN32)
593 COMPILER_RT_VISIBILITY
__gcov_fork()594 pid_t __gcov_fork() {
595 pid_t parent_pid = getpid();
596 pid_t pid = fork();
597
598 if (pid == 0) {
599 pid_t child_pid = getpid();
600 if (child_pid != parent_pid) {
601 // The pid changed so we've a fork (one could have its own fork function)
602 // Just reset the counters for this child process
603 // threads.
604 llvm_reset_counters();
605 }
606 }
607 return pid;
608 }
609 #endif
610
611 COMPILER_RT_VISIBILITY
llvm_gcov_init(fn_ptr wfn,fn_ptr rfn)612 void llvm_gcov_init(fn_ptr wfn, fn_ptr rfn) {
613 static int atexit_ran = 0;
614
615 if (wfn)
616 llvm_register_writeout_function(wfn);
617
618 if (rfn)
619 llvm_register_reset_function(rfn);
620
621 if (atexit_ran == 0) {
622 atexit_ran = 1;
623
624 /* Make sure we write out the data and delete the data structures. */
625 atexit(llvm_delete_reset_function_list);
626 #ifdef _WIN32
627 atexit(llvm_writeout_and_clear);
628 #endif
629 }
630 }
631
__gcov_dump(void)632 void __gcov_dump(void) {
633 for (struct fn_node *f = writeout_fn_list.head; f; f = f->next)
634 f->fn();
635 }
636
__gcov_reset(void)637 void __gcov_reset(void) {
638 for (struct fn_node *f = reset_fn_list.head; f; f = f->next)
639 f->fn();
640 }
641
642 #endif
643