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Linux/kernel/gcov/clang.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (C) 2019 Google, Inc.
  4  * modified from kernel/gcov/gcc_4_7.c
  5  *
  6  * This software is licensed under the terms of the GNU General Public
  7  * License version 2, as published by the Free Software Foundation, and
  8  * may be copied, distributed, and modified under those terms.
  9  *
 10  * This program is distributed in the hope that it will be useful,
 11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 13  * GNU General Public License for more details.
 14  *
 15  *
 16  * LLVM uses profiling data that's deliberately similar to GCC, but has a
 17  * very different way of exporting that data.  LLVM calls llvm_gcov_init() once
 18  * per module, and provides a couple of callbacks that we can use to ask for
 19  * more data.
 20  *
 21  * We care about the "writeout" callback, which in turn calls back into
 22  * compiler-rt/this module to dump all the gathered coverage data to disk:
 23  *
 24  *    llvm_gcda_start_file()
 25  *      llvm_gcda_emit_function()
 26  *      llvm_gcda_emit_arcs()
 27  *      llvm_gcda_emit_function()
 28  *      llvm_gcda_emit_arcs()
 29  *      [... repeats for each function ...]
 30  *    llvm_gcda_summary_info()
 31  *    llvm_gcda_end_file()
 32  *
 33  * This design is much more stateless and unstructured than gcc's, and is
 34  * intended to run at process exit.  This forces us to keep some local state
 35  * about which module we're dealing with at the moment.  On the other hand, it
 36  * also means we don't depend as much on how LLVM represents profiling data
 37  * internally.
 38  *
 39  * See LLVM's lib/Transforms/Instrumentation/GCOVProfiling.cpp for more
 40  * details on how this works, particularly GCOVProfiler::emitProfileArcs(),
 41  * GCOVProfiler::insertCounterWriteout(), and
 42  * GCOVProfiler::insertFlush().
 43  */
 44 
 45 #define pr_fmt(fmt)     "gcov: " fmt
 46 
 47 #include <linux/kernel.h>
 48 #include <linux/list.h>
 49 #include <linux/printk.h>
 50 #include <linux/ratelimit.h>
 51 #include <linux/seq_file.h>
 52 #include <linux/slab.h>
 53 #include <linux/vmalloc.h>
 54 #include "gcov.h"
 55 
 56 typedef void (*llvm_gcov_callback)(void);
 57 
 58 struct gcov_info {
 59         struct list_head head;
 60 
 61         const char *filename;
 62         unsigned int version;
 63         u32 checksum;
 64 
 65         struct list_head functions;
 66 };
 67 
 68 struct gcov_fn_info {
 69         struct list_head head;
 70 
 71         u32 ident;
 72         u32 checksum;
 73         u8 use_extra_checksum;
 74         u32 cfg_checksum;
 75 
 76         u32 num_counters;
 77         u64 *counters;
 78         const char *function_name;
 79 };
 80 
 81 static struct gcov_info *current_info;
 82 
 83 static LIST_HEAD(clang_gcov_list);
 84 
 85 void llvm_gcov_init(llvm_gcov_callback writeout, llvm_gcov_callback flush)
 86 {
 87         struct gcov_info *info = kzalloc(sizeof(*info), GFP_KERNEL);
 88 
 89         if (!info)
 90                 return;
 91 
 92         INIT_LIST_HEAD(&info->head);
 93         INIT_LIST_HEAD(&info->functions);
 94 
 95         mutex_lock(&gcov_lock);
 96 
 97         list_add_tail(&info->head, &clang_gcov_list);
 98         current_info = info;
 99         writeout();
100         current_info = NULL;
101         if (gcov_events_enabled)
102                 gcov_event(GCOV_ADD, info);
103 
104         mutex_unlock(&gcov_lock);
105 }
106 EXPORT_SYMBOL(llvm_gcov_init);
107 
108 void llvm_gcda_start_file(const char *orig_filename, const char version[4],
109                 u32 checksum)
110 {
111         current_info->filename = orig_filename;
112         memcpy(&current_info->version, version, sizeof(current_info->version));
113         current_info->checksum = checksum;
114 }
115 EXPORT_SYMBOL(llvm_gcda_start_file);
116 
117 void llvm_gcda_emit_function(u32 ident, const char *function_name,
118                 u32 func_checksum, u8 use_extra_checksum, u32 cfg_checksum)
119 {
120         struct gcov_fn_info *info = kzalloc(sizeof(*info), GFP_KERNEL);
121 
122         if (!info)
123                 return;
124 
125         INIT_LIST_HEAD(&info->head);
126         info->ident = ident;
127         info->checksum = func_checksum;
128         info->use_extra_checksum = use_extra_checksum;
129         info->cfg_checksum = cfg_checksum;
130         if (function_name)
131                 info->function_name = kstrdup(function_name, GFP_KERNEL);
132 
133         list_add_tail(&info->head, &current_info->functions);
134 }
135 EXPORT_SYMBOL(llvm_gcda_emit_function);
136 
137 void llvm_gcda_emit_arcs(u32 num_counters, u64 *counters)
138 {
139         struct gcov_fn_info *info = list_last_entry(&current_info->functions,
140                         struct gcov_fn_info, head);
141 
142         info->num_counters = num_counters;
143         info->counters = counters;
144 }
145 EXPORT_SYMBOL(llvm_gcda_emit_arcs);
146 
147 void llvm_gcda_summary_info(void)
148 {
149 }
150 EXPORT_SYMBOL(llvm_gcda_summary_info);
151 
152 void llvm_gcda_end_file(void)
153 {
154 }
155 EXPORT_SYMBOL(llvm_gcda_end_file);
156 
157 /**
158  * gcov_info_filename - return info filename
159  * @info: profiling data set
160  */
161 const char *gcov_info_filename(struct gcov_info *info)
162 {
163         return info->filename;
164 }
165 
166 /**
167  * gcov_info_version - return info version
168  * @info: profiling data set
169  */
170 unsigned int gcov_info_version(struct gcov_info *info)
171 {
172         return info->version;
173 }
174 
175 /**
176  * gcov_info_next - return next profiling data set
177  * @info: profiling data set
178  *
179  * Returns next gcov_info following @info or first gcov_info in the chain if
180  * @info is %NULL.
181  */
182 struct gcov_info *gcov_info_next(struct gcov_info *info)
183 {
184         if (!info)
185                 return list_first_entry_or_null(&clang_gcov_list,
186                                 struct gcov_info, head);
187         if (list_is_last(&info->head, &clang_gcov_list))
188                 return NULL;
189         return list_next_entry(info, head);
190 }
191 
192 /**
193  * gcov_info_link - link/add profiling data set to the list
194  * @info: profiling data set
195  */
196 void gcov_info_link(struct gcov_info *info)
197 {
198         list_add_tail(&info->head, &clang_gcov_list);
199 }
200 
201 /**
202  * gcov_info_unlink - unlink/remove profiling data set from the list
203  * @prev: previous profiling data set
204  * @info: profiling data set
205  */
206 void gcov_info_unlink(struct gcov_info *prev, struct gcov_info *info)
207 {
208         /* Generic code unlinks while iterating. */
209         __list_del_entry(&info->head);
210 }
211 
212 /**
213  * gcov_info_within_module - check if a profiling data set belongs to a module
214  * @info: profiling data set
215  * @mod: module
216  *
217  * Returns true if profiling data belongs module, false otherwise.
218  */
219 bool gcov_info_within_module(struct gcov_info *info, struct module *mod)
220 {
221         return within_module((unsigned long)info->filename, mod);
222 }
223 
224 /* Symbolic links to be created for each profiling data file. */
225 const struct gcov_link gcov_link[] = {
226         { OBJ_TREE, "gcno" },   /* Link to .gcno file in $(objtree). */
227         { 0, NULL},
228 };
229 
230 /**
231  * gcov_info_reset - reset profiling data to zero
232  * @info: profiling data set
233  */
234 void gcov_info_reset(struct gcov_info *info)
235 {
236         struct gcov_fn_info *fn;
237 
238         list_for_each_entry(fn, &info->functions, head)
239                 memset(fn->counters, 0,
240                                 sizeof(fn->counters[0]) * fn->num_counters);
241 }
242 
243 /**
244  * gcov_info_is_compatible - check if profiling data can be added
245  * @info1: first profiling data set
246  * @info2: second profiling data set
247  *
248  * Returns non-zero if profiling data can be added, zero otherwise.
249  */
250 int gcov_info_is_compatible(struct gcov_info *info1, struct gcov_info *info2)
251 {
252         struct gcov_fn_info *fn_ptr1 = list_first_entry_or_null(
253                         &info1->functions, struct gcov_fn_info, head);
254         struct gcov_fn_info *fn_ptr2 = list_first_entry_or_null(
255                         &info2->functions, struct gcov_fn_info, head);
256 
257         if (info1->checksum != info2->checksum)
258                 return false;
259         if (!fn_ptr1)
260                 return fn_ptr1 == fn_ptr2;
261         while (!list_is_last(&fn_ptr1->head, &info1->functions) &&
262                 !list_is_last(&fn_ptr2->head, &info2->functions)) {
263                 if (fn_ptr1->checksum != fn_ptr2->checksum)
264                         return false;
265                 if (fn_ptr1->use_extra_checksum != fn_ptr2->use_extra_checksum)
266                         return false;
267                 if (fn_ptr1->use_extra_checksum &&
268                         fn_ptr1->cfg_checksum != fn_ptr2->cfg_checksum)
269                         return false;
270                 fn_ptr1 = list_next_entry(fn_ptr1, head);
271                 fn_ptr2 = list_next_entry(fn_ptr2, head);
272         }
273         return list_is_last(&fn_ptr1->head, &info1->functions) &&
274                 list_is_last(&fn_ptr2->head, &info2->functions);
275 }
276 
277 /**
278  * gcov_info_add - add up profiling data
279  * @dest: profiling data set to which data is added
280  * @source: profiling data set which is added
281  *
282  * Adds profiling counts of @source to @dest.
283  */
284 void gcov_info_add(struct gcov_info *dst, struct gcov_info *src)
285 {
286         struct gcov_fn_info *dfn_ptr;
287         struct gcov_fn_info *sfn_ptr = list_first_entry_or_null(&src->functions,
288                         struct gcov_fn_info, head);
289 
290         list_for_each_entry(dfn_ptr, &dst->functions, head) {
291                 u32 i;
292 
293                 for (i = 0; i < sfn_ptr->num_counters; i++)
294                         dfn_ptr->counters[i] += sfn_ptr->counters[i];
295         }
296 }
297 
298 static struct gcov_fn_info *gcov_fn_info_dup(struct gcov_fn_info *fn)
299 {
300         size_t cv_size; /* counter values size */
301         struct gcov_fn_info *fn_dup = kmemdup(fn, sizeof(*fn),
302                         GFP_KERNEL);
303         if (!fn_dup)
304                 return NULL;
305         INIT_LIST_HEAD(&fn_dup->head);
306 
307         fn_dup->function_name = kstrdup(fn->function_name, GFP_KERNEL);
308         if (!fn_dup->function_name)
309                 goto err_name;
310 
311         cv_size = fn->num_counters * sizeof(fn->counters[0]);
312         fn_dup->counters = vmalloc(cv_size);
313         if (!fn_dup->counters)
314                 goto err_counters;
315         memcpy(fn_dup->counters, fn->counters, cv_size);
316 
317         return fn_dup;
318 
319 err_counters:
320         kfree(fn_dup->function_name);
321 err_name:
322         kfree(fn_dup);
323         return NULL;
324 }
325 
326 /**
327  * gcov_info_dup - duplicate profiling data set
328  * @info: profiling data set to duplicate
329  *
330  * Return newly allocated duplicate on success, %NULL on error.
331  */
332 struct gcov_info *gcov_info_dup(struct gcov_info *info)
333 {
334         struct gcov_info *dup;
335         struct gcov_fn_info *fn;
336 
337         dup = kmemdup(info, sizeof(*dup), GFP_KERNEL);
338         if (!dup)
339                 return NULL;
340         INIT_LIST_HEAD(&dup->head);
341         INIT_LIST_HEAD(&dup->functions);
342         dup->filename = kstrdup(info->filename, GFP_KERNEL);
343         if (!dup->filename)
344                 goto err;
345 
346         list_for_each_entry(fn, &info->functions, head) {
347                 struct gcov_fn_info *fn_dup = gcov_fn_info_dup(fn);
348 
349                 if (!fn_dup)
350                         goto err;
351                 list_add_tail(&fn_dup->head, &dup->functions);
352         }
353 
354         return dup;
355 
356 err:
357         gcov_info_free(dup);
358         return NULL;
359 }
360 
361 /**
362  * gcov_info_free - release memory for profiling data set duplicate
363  * @info: profiling data set duplicate to free
364  */
365 void gcov_info_free(struct gcov_info *info)
366 {
367         struct gcov_fn_info *fn, *tmp;
368 
369         list_for_each_entry_safe(fn, tmp, &info->functions, head) {
370                 kfree(fn->function_name);
371                 vfree(fn->counters);
372                 list_del(&fn->head);
373                 kfree(fn);
374         }
375         kfree(info->filename);
376         kfree(info);
377 }
378 
379 #define ITER_STRIDE     PAGE_SIZE
380 
381 /**
382  * struct gcov_iterator - specifies current file position in logical records
383  * @info: associated profiling data
384  * @buffer: buffer containing file data
385  * @size: size of buffer
386  * @pos: current position in file
387  */
388 struct gcov_iterator {
389         struct gcov_info *info;
390         void *buffer;
391         size_t size;
392         loff_t pos;
393 };
394 
395 /**
396  * store_gcov_u32 - store 32 bit number in gcov format to buffer
397  * @buffer: target buffer or NULL
398  * @off: offset into the buffer
399  * @v: value to be stored
400  *
401  * Number format defined by gcc: numbers are recorded in the 32 bit
402  * unsigned binary form of the endianness of the machine generating the
403  * file. Returns the number of bytes stored. If @buffer is %NULL, doesn't
404  * store anything.
405  */
406 static size_t store_gcov_u32(void *buffer, size_t off, u32 v)
407 {
408         u32 *data;
409 
410         if (buffer) {
411                 data = buffer + off;
412                 *data = v;
413         }
414 
415         return sizeof(*data);
416 }
417 
418 /**
419  * store_gcov_u64 - store 64 bit number in gcov format to buffer
420  * @buffer: target buffer or NULL
421  * @off: offset into the buffer
422  * @v: value to be stored
423  *
424  * Number format defined by gcc: numbers are recorded in the 32 bit
425  * unsigned binary form of the endianness of the machine generating the
426  * file. 64 bit numbers are stored as two 32 bit numbers, the low part
427  * first. Returns the number of bytes stored. If @buffer is %NULL, doesn't store
428  * anything.
429  */
430 static size_t store_gcov_u64(void *buffer, size_t off, u64 v)
431 {
432         u32 *data;
433 
434         if (buffer) {
435                 data = buffer + off;
436 
437                 data[0] = (v & 0xffffffffUL);
438                 data[1] = (v >> 32);
439         }
440 
441         return sizeof(*data) * 2;
442 }
443 
444 /**
445  * convert_to_gcda - convert profiling data set to gcda file format
446  * @buffer: the buffer to store file data or %NULL if no data should be stored
447  * @info: profiling data set to be converted
448  *
449  * Returns the number of bytes that were/would have been stored into the buffer.
450  */
451 static size_t convert_to_gcda(char *buffer, struct gcov_info *info)
452 {
453         struct gcov_fn_info *fi_ptr;
454         size_t pos = 0;
455 
456         /* File header. */
457         pos += store_gcov_u32(buffer, pos, GCOV_DATA_MAGIC);
458         pos += store_gcov_u32(buffer, pos, info->version);
459         pos += store_gcov_u32(buffer, pos, info->checksum);
460 
461         list_for_each_entry(fi_ptr, &info->functions, head) {
462                 u32 i;
463                 u32 len = 2;
464 
465                 if (fi_ptr->use_extra_checksum)
466                         len++;
467 
468                 pos += store_gcov_u32(buffer, pos, GCOV_TAG_FUNCTION);
469                 pos += store_gcov_u32(buffer, pos, len);
470                 pos += store_gcov_u32(buffer, pos, fi_ptr->ident);
471                 pos += store_gcov_u32(buffer, pos, fi_ptr->checksum);
472                 if (fi_ptr->use_extra_checksum)
473                         pos += store_gcov_u32(buffer, pos, fi_ptr->cfg_checksum);
474 
475                 pos += store_gcov_u32(buffer, pos, GCOV_TAG_COUNTER_BASE);
476                 pos += store_gcov_u32(buffer, pos, fi_ptr->num_counters * 2);
477                 for (i = 0; i < fi_ptr->num_counters; i++)
478                         pos += store_gcov_u64(buffer, pos, fi_ptr->counters[i]);
479         }
480 
481         return pos;
482 }
483 
484 /**
485  * gcov_iter_new - allocate and initialize profiling data iterator
486  * @info: profiling data set to be iterated
487  *
488  * Return file iterator on success, %NULL otherwise.
489  */
490 struct gcov_iterator *gcov_iter_new(struct gcov_info *info)
491 {
492         struct gcov_iterator *iter;
493 
494         iter = kzalloc(sizeof(struct gcov_iterator), GFP_KERNEL);
495         if (!iter)
496                 goto err_free;
497 
498         iter->info = info;
499         /* Dry-run to get the actual buffer size. */
500         iter->size = convert_to_gcda(NULL, info);
501         iter->buffer = vmalloc(iter->size);
502         if (!iter->buffer)
503                 goto err_free;
504 
505         convert_to_gcda(iter->buffer, info);
506 
507         return iter;
508 
509 err_free:
510         kfree(iter);
511         return NULL;
512 }
513 
514 
515 /**
516  * gcov_iter_get_info - return profiling data set for given file iterator
517  * @iter: file iterator
518  */
519 void gcov_iter_free(struct gcov_iterator *iter)
520 {
521         vfree(iter->buffer);
522         kfree(iter);
523 }
524 
525 /**
526  * gcov_iter_get_info - return profiling data set for given file iterator
527  * @iter: file iterator
528  */
529 struct gcov_info *gcov_iter_get_info(struct gcov_iterator *iter)
530 {
531         return iter->info;
532 }
533 
534 /**
535  * gcov_iter_start - reset file iterator to starting position
536  * @iter: file iterator
537  */
538 void gcov_iter_start(struct gcov_iterator *iter)
539 {
540         iter->pos = 0;
541 }
542 
543 /**
544  * gcov_iter_next - advance file iterator to next logical record
545  * @iter: file iterator
546  *
547  * Return zero if new position is valid, non-zero if iterator has reached end.
548  */
549 int gcov_iter_next(struct gcov_iterator *iter)
550 {
551         if (iter->pos < iter->size)
552                 iter->pos += ITER_STRIDE;
553 
554         if (iter->pos >= iter->size)
555                 return -EINVAL;
556 
557         return 0;
558 }
559 
560 /**
561  * gcov_iter_write - write data for current pos to seq_file
562  * @iter: file iterator
563  * @seq: seq_file handle
564  *
565  * Return zero on success, non-zero otherwise.
566  */
567 int gcov_iter_write(struct gcov_iterator *iter, struct seq_file *seq)
568 {
569         size_t len;
570 
571         if (iter->pos >= iter->size)
572                 return -EINVAL;
573 
574         len = ITER_STRIDE;
575         if (iter->pos + len > iter->size)
576                 len = iter->size - iter->pos;
577 
578         seq_write(seq, iter->buffer + iter->pos, len);
579 
580         return 0;
581 }
582 

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