1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2
3 /*
4 * BTF-to-C type converter.
5 *
6 * Copyright (c) 2019 Facebook
7 */
8
9 #include <stdbool.h>
10 #include <stddef.h>
11 #include <stdlib.h>
12 #include <string.h>
13 #include <errno.h>
14 #include <linux/err.h>
15 #include <linux/btf.h>
16 #include <linux/kernel.h>
17 #include "btf.h"
18 #include "hashmap.h"
19 #include "libbpf.h"
20 #include "libbpf_internal.h"
21
22 static const char PREFIXES[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t";
23 static const size_t PREFIX_CNT = sizeof(PREFIXES) - 1;
24
pfx(int lvl)25 static const char *pfx(int lvl)
26 {
27 return lvl >= PREFIX_CNT ? PREFIXES : &PREFIXES[PREFIX_CNT - lvl];
28 }
29
30 enum btf_dump_type_order_state {
31 NOT_ORDERED,
32 ORDERING,
33 ORDERED,
34 };
35
36 enum btf_dump_type_emit_state {
37 NOT_EMITTED,
38 EMITTING,
39 EMITTED,
40 };
41
42 /* per-type auxiliary state */
43 struct btf_dump_type_aux_state {
44 /* topological sorting state */
45 enum btf_dump_type_order_state order_state: 2;
46 /* emitting state used to determine the need for forward declaration */
47 enum btf_dump_type_emit_state emit_state: 2;
48 /* whether forward declaration was already emitted */
49 __u8 fwd_emitted: 1;
50 /* whether unique non-duplicate name was already assigned */
51 __u8 name_resolved: 1;
52 /* whether type is referenced from any other type */
53 __u8 referenced: 1;
54 };
55
56 struct btf_dump {
57 const struct btf *btf;
58 const struct btf_ext *btf_ext;
59 btf_dump_printf_fn_t printf_fn;
60 struct btf_dump_opts opts;
61 int ptr_sz;
62 bool strip_mods;
63 int last_id;
64
65 /* per-type auxiliary state */
66 struct btf_dump_type_aux_state *type_states;
67 size_t type_states_cap;
68 /* per-type optional cached unique name, must be freed, if present */
69 const char **cached_names;
70 size_t cached_names_cap;
71
72 /* topo-sorted list of dependent type definitions */
73 __u32 *emit_queue;
74 int emit_queue_cap;
75 int emit_queue_cnt;
76
77 /*
78 * stack of type declarations (e.g., chain of modifiers, arrays,
79 * funcs, etc)
80 */
81 __u32 *decl_stack;
82 int decl_stack_cap;
83 int decl_stack_cnt;
84
85 /* maps struct/union/enum name to a number of name occurrences */
86 struct hashmap *type_names;
87 /*
88 * maps typedef identifiers and enum value names to a number of such
89 * name occurrences
90 */
91 struct hashmap *ident_names;
92 };
93
str_hash_fn(const void * key,void * ctx)94 static size_t str_hash_fn(const void *key, void *ctx)
95 {
96 return str_hash(key);
97 }
98
str_equal_fn(const void * a,const void * b,void * ctx)99 static bool str_equal_fn(const void *a, const void *b, void *ctx)
100 {
101 return strcmp(a, b) == 0;
102 }
103
btf_name_of(const struct btf_dump * d,__u32 name_off)104 static const char *btf_name_of(const struct btf_dump *d, __u32 name_off)
105 {
106 return btf__name_by_offset(d->btf, name_off);
107 }
108
btf_dump_printf(const struct btf_dump * d,const char * fmt,...)109 static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...)
110 {
111 va_list args;
112
113 va_start(args, fmt);
114 d->printf_fn(d->opts.ctx, fmt, args);
115 va_end(args);
116 }
117
118 static int btf_dump_mark_referenced(struct btf_dump *d);
119 static int btf_dump_resize(struct btf_dump *d);
120
btf_dump__new(const struct btf * btf,const struct btf_ext * btf_ext,const struct btf_dump_opts * opts,btf_dump_printf_fn_t printf_fn)121 struct btf_dump *btf_dump__new(const struct btf *btf,
122 const struct btf_ext *btf_ext,
123 const struct btf_dump_opts *opts,
124 btf_dump_printf_fn_t printf_fn)
125 {
126 struct btf_dump *d;
127 int err;
128
129 d = calloc(1, sizeof(struct btf_dump));
130 if (!d)
131 return ERR_PTR(-ENOMEM);
132
133 d->btf = btf;
134 d->btf_ext = btf_ext;
135 d->printf_fn = printf_fn;
136 d->opts.ctx = opts ? opts->ctx : NULL;
137 d->ptr_sz = btf__pointer_size(btf) ? : sizeof(void *);
138
139 d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
140 if (IS_ERR(d->type_names)) {
141 err = PTR_ERR(d->type_names);
142 d->type_names = NULL;
143 goto err;
144 }
145 d->ident_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
146 if (IS_ERR(d->ident_names)) {
147 err = PTR_ERR(d->ident_names);
148 d->ident_names = NULL;
149 goto err;
150 }
151
152 err = btf_dump_resize(d);
153 if (err)
154 goto err;
155
156 return d;
157 err:
158 btf_dump__free(d);
159 return ERR_PTR(err);
160 }
161
btf_dump_resize(struct btf_dump * d)162 static int btf_dump_resize(struct btf_dump *d)
163 {
164 int err, last_id = btf__get_nr_types(d->btf);
165
166 if (last_id <= d->last_id)
167 return 0;
168
169 if (btf_ensure_mem((void **)&d->type_states, &d->type_states_cap,
170 sizeof(*d->type_states), last_id + 1))
171 return -ENOMEM;
172 if (btf_ensure_mem((void **)&d->cached_names, &d->cached_names_cap,
173 sizeof(*d->cached_names), last_id + 1))
174 return -ENOMEM;
175
176 if (d->last_id == 0) {
177 /* VOID is special */
178 d->type_states[0].order_state = ORDERED;
179 d->type_states[0].emit_state = EMITTED;
180 }
181
182 /* eagerly determine referenced types for anon enums */
183 err = btf_dump_mark_referenced(d);
184 if (err)
185 return err;
186
187 d->last_id = last_id;
188 return 0;
189 }
190
btf_dump_free_names(struct hashmap * map)191 static void btf_dump_free_names(struct hashmap *map)
192 {
193 size_t bkt;
194 struct hashmap_entry *cur;
195
196 hashmap__for_each_entry(map, cur, bkt)
197 free((void *)cur->key);
198
199 hashmap__free(map);
200 }
201
btf_dump__free(struct btf_dump * d)202 void btf_dump__free(struct btf_dump *d)
203 {
204 int i;
205
206 if (IS_ERR_OR_NULL(d))
207 return;
208
209 free(d->type_states);
210 if (d->cached_names) {
211 /* any set cached name is owned by us and should be freed */
212 for (i = 0; i <= d->last_id; i++) {
213 if (d->cached_names[i])
214 free((void *)d->cached_names[i]);
215 }
216 }
217 free(d->cached_names);
218 free(d->emit_queue);
219 free(d->decl_stack);
220 btf_dump_free_names(d->type_names);
221 btf_dump_free_names(d->ident_names);
222
223 free(d);
224 }
225
226 static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr);
227 static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id);
228
229 /*
230 * Dump BTF type in a compilable C syntax, including all the necessary
231 * dependent types, necessary for compilation. If some of the dependent types
232 * were already emitted as part of previous btf_dump__dump_type() invocation
233 * for another type, they won't be emitted again. This API allows callers to
234 * filter out BTF types according to user-defined criterias and emitted only
235 * minimal subset of types, necessary to compile everything. Full struct/union
236 * definitions will still be emitted, even if the only usage is through
237 * pointer and could be satisfied with just a forward declaration.
238 *
239 * Dumping is done in two high-level passes:
240 * 1. Topologically sort type definitions to satisfy C rules of compilation.
241 * 2. Emit type definitions in C syntax.
242 *
243 * Returns 0 on success; <0, otherwise.
244 */
btf_dump__dump_type(struct btf_dump * d,__u32 id)245 int btf_dump__dump_type(struct btf_dump *d, __u32 id)
246 {
247 int err, i;
248
249 if (id > btf__get_nr_types(d->btf))
250 return -EINVAL;
251
252 err = btf_dump_resize(d);
253 if (err)
254 return err;
255
256 d->emit_queue_cnt = 0;
257 err = btf_dump_order_type(d, id, false);
258 if (err < 0)
259 return err;
260
261 for (i = 0; i < d->emit_queue_cnt; i++)
262 btf_dump_emit_type(d, d->emit_queue[i], 0 /*top-level*/);
263
264 return 0;
265 }
266
267 /*
268 * Mark all types that are referenced from any other type. This is used to
269 * determine top-level anonymous enums that need to be emitted as an
270 * independent type declarations.
271 * Anonymous enums come in two flavors: either embedded in a struct's field
272 * definition, in which case they have to be declared inline as part of field
273 * type declaration; or as a top-level anonymous enum, typically used for
274 * declaring global constants. It's impossible to distinguish between two
275 * without knowning whether given enum type was referenced from other type:
276 * top-level anonymous enum won't be referenced by anything, while embedded
277 * one will.
278 */
btf_dump_mark_referenced(struct btf_dump * d)279 static int btf_dump_mark_referenced(struct btf_dump *d)
280 {
281 int i, j, n = btf__get_nr_types(d->btf);
282 const struct btf_type *t;
283 __u16 vlen;
284
285 for (i = d->last_id + 1; i <= n; i++) {
286 t = btf__type_by_id(d->btf, i);
287 vlen = btf_vlen(t);
288
289 switch (btf_kind(t)) {
290 case BTF_KIND_INT:
291 case BTF_KIND_ENUM:
292 case BTF_KIND_FWD:
293 break;
294
295 case BTF_KIND_VOLATILE:
296 case BTF_KIND_CONST:
297 case BTF_KIND_RESTRICT:
298 case BTF_KIND_PTR:
299 case BTF_KIND_TYPEDEF:
300 case BTF_KIND_FUNC:
301 case BTF_KIND_VAR:
302 d->type_states[t->type].referenced = 1;
303 break;
304
305 case BTF_KIND_ARRAY: {
306 const struct btf_array *a = btf_array(t);
307
308 d->type_states[a->index_type].referenced = 1;
309 d->type_states[a->type].referenced = 1;
310 break;
311 }
312 case BTF_KIND_STRUCT:
313 case BTF_KIND_UNION: {
314 const struct btf_member *m = btf_members(t);
315
316 for (j = 0; j < vlen; j++, m++)
317 d->type_states[m->type].referenced = 1;
318 break;
319 }
320 case BTF_KIND_FUNC_PROTO: {
321 const struct btf_param *p = btf_params(t);
322
323 for (j = 0; j < vlen; j++, p++)
324 d->type_states[p->type].referenced = 1;
325 break;
326 }
327 case BTF_KIND_DATASEC: {
328 const struct btf_var_secinfo *v = btf_var_secinfos(t);
329
330 for (j = 0; j < vlen; j++, v++)
331 d->type_states[v->type].referenced = 1;
332 break;
333 }
334 default:
335 return -EINVAL;
336 }
337 }
338 return 0;
339 }
340
btf_dump_add_emit_queue_id(struct btf_dump * d,__u32 id)341 static int btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id)
342 {
343 __u32 *new_queue;
344 size_t new_cap;
345
346 if (d->emit_queue_cnt >= d->emit_queue_cap) {
347 new_cap = max(16, d->emit_queue_cap * 3 / 2);
348 new_queue = libbpf_reallocarray(d->emit_queue, new_cap, sizeof(new_queue[0]));
349 if (!new_queue)
350 return -ENOMEM;
351 d->emit_queue = new_queue;
352 d->emit_queue_cap = new_cap;
353 }
354
355 d->emit_queue[d->emit_queue_cnt++] = id;
356 return 0;
357 }
358
359 /*
360 * Determine order of emitting dependent types and specified type to satisfy
361 * C compilation rules. This is done through topological sorting with an
362 * additional complication which comes from C rules. The main idea for C is
363 * that if some type is "embedded" into a struct/union, it's size needs to be
364 * known at the time of definition of containing type. E.g., for:
365 *
366 * struct A {};
367 * struct B { struct A x; }
368 *
369 * struct A *HAS* to be defined before struct B, because it's "embedded",
370 * i.e., it is part of struct B layout. But in the following case:
371 *
372 * struct A;
373 * struct B { struct A *x; }
374 * struct A {};
375 *
376 * it's enough to just have a forward declaration of struct A at the time of
377 * struct B definition, as struct B has a pointer to struct A, so the size of
378 * field x is known without knowing struct A size: it's sizeof(void *).
379 *
380 * Unfortunately, there are some trickier cases we need to handle, e.g.:
381 *
382 * struct A {}; // if this was forward-declaration: compilation error
383 * struct B {
384 * struct { // anonymous struct
385 * struct A y;
386 * } *x;
387 * };
388 *
389 * In this case, struct B's field x is a pointer, so it's size is known
390 * regardless of the size of (anonymous) struct it points to. But because this
391 * struct is anonymous and thus defined inline inside struct B, *and* it
392 * embeds struct A, compiler requires full definition of struct A to be known
393 * before struct B can be defined. This creates a transitive dependency
394 * between struct A and struct B. If struct A was forward-declared before
395 * struct B definition and fully defined after struct B definition, that would
396 * trigger compilation error.
397 *
398 * All this means that while we are doing topological sorting on BTF type
399 * graph, we need to determine relationships between different types (graph
400 * nodes):
401 * - weak link (relationship) between X and Y, if Y *CAN* be
402 * forward-declared at the point of X definition;
403 * - strong link, if Y *HAS* to be fully-defined before X can be defined.
404 *
405 * The rule is as follows. Given a chain of BTF types from X to Y, if there is
406 * BTF_KIND_PTR type in the chain and at least one non-anonymous type
407 * Z (excluding X, including Y), then link is weak. Otherwise, it's strong.
408 * Weak/strong relationship is determined recursively during DFS traversal and
409 * is returned as a result from btf_dump_order_type().
410 *
411 * btf_dump_order_type() is trying to avoid unnecessary forward declarations,
412 * but it is not guaranteeing that no extraneous forward declarations will be
413 * emitted.
414 *
415 * To avoid extra work, algorithm marks some of BTF types as ORDERED, when
416 * it's done with them, but not for all (e.g., VOLATILE, CONST, RESTRICT,
417 * ARRAY, FUNC_PROTO), as weak/strong semantics for those depends on the
418 * entire graph path, so depending where from one came to that BTF type, it
419 * might cause weak or strong ordering. For types like STRUCT/UNION/INT/ENUM,
420 * once they are processed, there is no need to do it again, so they are
421 * marked as ORDERED. We can mark PTR as ORDERED as well, as it semi-forces
422 * weak link, unless subsequent referenced STRUCT/UNION/ENUM is anonymous. But
423 * in any case, once those are processed, no need to do it again, as the
424 * result won't change.
425 *
426 * Returns:
427 * - 1, if type is part of strong link (so there is strong topological
428 * ordering requirements);
429 * - 0, if type is part of weak link (so can be satisfied through forward
430 * declaration);
431 * - <0, on error (e.g., unsatisfiable type loop detected).
432 */
btf_dump_order_type(struct btf_dump * d,__u32 id,bool through_ptr)433 static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
434 {
435 /*
436 * Order state is used to detect strong link cycles, but only for BTF
437 * kinds that are or could be an independent definition (i.e.,
438 * stand-alone fwd decl, enum, typedef, struct, union). Ptrs, arrays,
439 * func_protos, modifiers are just means to get to these definitions.
440 * Int/void don't need definitions, they are assumed to be always
441 * properly defined. We also ignore datasec, var, and funcs for now.
442 * So for all non-defining kinds, we never even set ordering state,
443 * for defining kinds we set ORDERING and subsequently ORDERED if it
444 * forms a strong link.
445 */
446 struct btf_dump_type_aux_state *tstate = &d->type_states[id];
447 const struct btf_type *t;
448 __u16 vlen;
449 int err, i;
450
451 /* return true, letting typedefs know that it's ok to be emitted */
452 if (tstate->order_state == ORDERED)
453 return 1;
454
455 t = btf__type_by_id(d->btf, id);
456
457 if (tstate->order_state == ORDERING) {
458 /* type loop, but resolvable through fwd declaration */
459 if (btf_is_composite(t) && through_ptr && t->name_off != 0)
460 return 0;
461 pr_warn("unsatisfiable type cycle, id:[%u]\n", id);
462 return -ELOOP;
463 }
464
465 switch (btf_kind(t)) {
466 case BTF_KIND_INT:
467 tstate->order_state = ORDERED;
468 return 0;
469
470 case BTF_KIND_PTR:
471 err = btf_dump_order_type(d, t->type, true);
472 tstate->order_state = ORDERED;
473 return err;
474
475 case BTF_KIND_ARRAY:
476 return btf_dump_order_type(d, btf_array(t)->type, false);
477
478 case BTF_KIND_STRUCT:
479 case BTF_KIND_UNION: {
480 const struct btf_member *m = btf_members(t);
481 /*
482 * struct/union is part of strong link, only if it's embedded
483 * (so no ptr in a path) or it's anonymous (so has to be
484 * defined inline, even if declared through ptr)
485 */
486 if (through_ptr && t->name_off != 0)
487 return 0;
488
489 tstate->order_state = ORDERING;
490
491 vlen = btf_vlen(t);
492 for (i = 0; i < vlen; i++, m++) {
493 err = btf_dump_order_type(d, m->type, false);
494 if (err < 0)
495 return err;
496 }
497
498 if (t->name_off != 0) {
499 err = btf_dump_add_emit_queue_id(d, id);
500 if (err < 0)
501 return err;
502 }
503
504 tstate->order_state = ORDERED;
505 return 1;
506 }
507 case BTF_KIND_ENUM:
508 case BTF_KIND_FWD:
509 /*
510 * non-anonymous or non-referenced enums are top-level
511 * declarations and should be emitted. Same logic can be
512 * applied to FWDs, it won't hurt anyways.
513 */
514 if (t->name_off != 0 || !tstate->referenced) {
515 err = btf_dump_add_emit_queue_id(d, id);
516 if (err)
517 return err;
518 }
519 tstate->order_state = ORDERED;
520 return 1;
521
522 case BTF_KIND_TYPEDEF: {
523 int is_strong;
524
525 is_strong = btf_dump_order_type(d, t->type, through_ptr);
526 if (is_strong < 0)
527 return is_strong;
528
529 /* typedef is similar to struct/union w.r.t. fwd-decls */
530 if (through_ptr && !is_strong)
531 return 0;
532
533 /* typedef is always a named definition */
534 err = btf_dump_add_emit_queue_id(d, id);
535 if (err)
536 return err;
537
538 d->type_states[id].order_state = ORDERED;
539 return 1;
540 }
541 case BTF_KIND_VOLATILE:
542 case BTF_KIND_CONST:
543 case BTF_KIND_RESTRICT:
544 return btf_dump_order_type(d, t->type, through_ptr);
545
546 case BTF_KIND_FUNC_PROTO: {
547 const struct btf_param *p = btf_params(t);
548 bool is_strong;
549
550 err = btf_dump_order_type(d, t->type, through_ptr);
551 if (err < 0)
552 return err;
553 is_strong = err > 0;
554
555 vlen = btf_vlen(t);
556 for (i = 0; i < vlen; i++, p++) {
557 err = btf_dump_order_type(d, p->type, through_ptr);
558 if (err < 0)
559 return err;
560 if (err > 0)
561 is_strong = true;
562 }
563 return is_strong;
564 }
565 case BTF_KIND_FUNC:
566 case BTF_KIND_VAR:
567 case BTF_KIND_DATASEC:
568 d->type_states[id].order_state = ORDERED;
569 return 0;
570
571 default:
572 return -EINVAL;
573 }
574 }
575
576 static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
577 const struct btf_type *t);
578
579 static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
580 const struct btf_type *t);
581 static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id,
582 const struct btf_type *t, int lvl);
583
584 static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
585 const struct btf_type *t);
586 static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
587 const struct btf_type *t, int lvl);
588
589 static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
590 const struct btf_type *t);
591
592 static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
593 const struct btf_type *t, int lvl);
594
595 /* a local view into a shared stack */
596 struct id_stack {
597 const __u32 *ids;
598 int cnt;
599 };
600
601 static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
602 const char *fname, int lvl);
603 static void btf_dump_emit_type_chain(struct btf_dump *d,
604 struct id_stack *decl_stack,
605 const char *fname, int lvl);
606
607 static const char *btf_dump_type_name(struct btf_dump *d, __u32 id);
608 static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id);
609 static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
610 const char *orig_name);
611
btf_dump_is_blacklisted(struct btf_dump * d,__u32 id)612 static bool btf_dump_is_blacklisted(struct btf_dump *d, __u32 id)
613 {
614 const struct btf_type *t = btf__type_by_id(d->btf, id);
615
616 /* __builtin_va_list is a compiler built-in, which causes compilation
617 * errors, when compiling w/ different compiler, then used to compile
618 * original code (e.g., GCC to compile kernel, Clang to use generated
619 * C header from BTF). As it is built-in, it should be already defined
620 * properly internally in compiler.
621 */
622 if (t->name_off == 0)
623 return false;
624 return strcmp(btf_name_of(d, t->name_off), "__builtin_va_list") == 0;
625 }
626
627 /*
628 * Emit C-syntax definitions of types from chains of BTF types.
629 *
630 * High-level handling of determining necessary forward declarations are handled
631 * by btf_dump_emit_type() itself, but all nitty-gritty details of emitting type
632 * declarations/definitions in C syntax are handled by a combo of
633 * btf_dump_emit_type_decl()/btf_dump_emit_type_chain() w/ delegation to
634 * corresponding btf_dump_emit_*_{def,fwd}() functions.
635 *
636 * We also keep track of "containing struct/union type ID" to determine when
637 * we reference it from inside and thus can avoid emitting unnecessary forward
638 * declaration.
639 *
640 * This algorithm is designed in such a way, that even if some error occurs
641 * (either technical, e.g., out of memory, or logical, i.e., malformed BTF
642 * that doesn't comply to C rules completely), algorithm will try to proceed
643 * and produce as much meaningful output as possible.
644 */
btf_dump_emit_type(struct btf_dump * d,__u32 id,__u32 cont_id)645 static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
646 {
647 struct btf_dump_type_aux_state *tstate = &d->type_states[id];
648 bool top_level_def = cont_id == 0;
649 const struct btf_type *t;
650 __u16 kind;
651
652 if (tstate->emit_state == EMITTED)
653 return;
654
655 t = btf__type_by_id(d->btf, id);
656 kind = btf_kind(t);
657
658 if (tstate->emit_state == EMITTING) {
659 if (tstate->fwd_emitted)
660 return;
661
662 switch (kind) {
663 case BTF_KIND_STRUCT:
664 case BTF_KIND_UNION:
665 /*
666 * if we are referencing a struct/union that we are
667 * part of - then no need for fwd declaration
668 */
669 if (id == cont_id)
670 return;
671 if (t->name_off == 0) {
672 pr_warn("anonymous struct/union loop, id:[%u]\n",
673 id);
674 return;
675 }
676 btf_dump_emit_struct_fwd(d, id, t);
677 btf_dump_printf(d, ";\n\n");
678 tstate->fwd_emitted = 1;
679 break;
680 case BTF_KIND_TYPEDEF:
681 /*
682 * for typedef fwd_emitted means typedef definition
683 * was emitted, but it can be used only for "weak"
684 * references through pointer only, not for embedding
685 */
686 if (!btf_dump_is_blacklisted(d, id)) {
687 btf_dump_emit_typedef_def(d, id, t, 0);
688 btf_dump_printf(d, ";\n\n");
689 }
690 tstate->fwd_emitted = 1;
691 break;
692 default:
693 break;
694 }
695
696 return;
697 }
698
699 switch (kind) {
700 case BTF_KIND_INT:
701 /* Emit type alias definitions if necessary */
702 btf_dump_emit_missing_aliases(d, id, t);
703
704 tstate->emit_state = EMITTED;
705 break;
706 case BTF_KIND_ENUM:
707 if (top_level_def) {
708 btf_dump_emit_enum_def(d, id, t, 0);
709 btf_dump_printf(d, ";\n\n");
710 }
711 tstate->emit_state = EMITTED;
712 break;
713 case BTF_KIND_PTR:
714 case BTF_KIND_VOLATILE:
715 case BTF_KIND_CONST:
716 case BTF_KIND_RESTRICT:
717 btf_dump_emit_type(d, t->type, cont_id);
718 break;
719 case BTF_KIND_ARRAY:
720 btf_dump_emit_type(d, btf_array(t)->type, cont_id);
721 break;
722 case BTF_KIND_FWD:
723 btf_dump_emit_fwd_def(d, id, t);
724 btf_dump_printf(d, ";\n\n");
725 tstate->emit_state = EMITTED;
726 break;
727 case BTF_KIND_TYPEDEF:
728 tstate->emit_state = EMITTING;
729 btf_dump_emit_type(d, t->type, id);
730 /*
731 * typedef can server as both definition and forward
732 * declaration; at this stage someone depends on
733 * typedef as a forward declaration (refers to it
734 * through pointer), so unless we already did it,
735 * emit typedef as a forward declaration
736 */
737 if (!tstate->fwd_emitted && !btf_dump_is_blacklisted(d, id)) {
738 btf_dump_emit_typedef_def(d, id, t, 0);
739 btf_dump_printf(d, ";\n\n");
740 }
741 tstate->emit_state = EMITTED;
742 break;
743 case BTF_KIND_STRUCT:
744 case BTF_KIND_UNION:
745 tstate->emit_state = EMITTING;
746 /* if it's a top-level struct/union definition or struct/union
747 * is anonymous, then in C we'll be emitting all fields and
748 * their types (as opposed to just `struct X`), so we need to
749 * make sure that all types, referenced from struct/union
750 * members have necessary forward-declarations, where
751 * applicable
752 */
753 if (top_level_def || t->name_off == 0) {
754 const struct btf_member *m = btf_members(t);
755 __u16 vlen = btf_vlen(t);
756 int i, new_cont_id;
757
758 new_cont_id = t->name_off == 0 ? cont_id : id;
759 for (i = 0; i < vlen; i++, m++)
760 btf_dump_emit_type(d, m->type, new_cont_id);
761 } else if (!tstate->fwd_emitted && id != cont_id) {
762 btf_dump_emit_struct_fwd(d, id, t);
763 btf_dump_printf(d, ";\n\n");
764 tstate->fwd_emitted = 1;
765 }
766
767 if (top_level_def) {
768 btf_dump_emit_struct_def(d, id, t, 0);
769 btf_dump_printf(d, ";\n\n");
770 tstate->emit_state = EMITTED;
771 } else {
772 tstate->emit_state = NOT_EMITTED;
773 }
774 break;
775 case BTF_KIND_FUNC_PROTO: {
776 const struct btf_param *p = btf_params(t);
777 __u16 vlen = btf_vlen(t);
778 int i;
779
780 btf_dump_emit_type(d, t->type, cont_id);
781 for (i = 0; i < vlen; i++, p++)
782 btf_dump_emit_type(d, p->type, cont_id);
783
784 break;
785 }
786 default:
787 break;
788 }
789 }
790
btf_is_struct_packed(const struct btf * btf,__u32 id,const struct btf_type * t)791 static bool btf_is_struct_packed(const struct btf *btf, __u32 id,
792 const struct btf_type *t)
793 {
794 const struct btf_member *m;
795 int align, i, bit_sz;
796 __u16 vlen;
797
798 align = btf__align_of(btf, id);
799 /* size of a non-packed struct has to be a multiple of its alignment*/
800 if (align && t->size % align)
801 return true;
802
803 m = btf_members(t);
804 vlen = btf_vlen(t);
805 /* all non-bitfield fields have to be naturally aligned */
806 for (i = 0; i < vlen; i++, m++) {
807 align = btf__align_of(btf, m->type);
808 bit_sz = btf_member_bitfield_size(t, i);
809 if (align && bit_sz == 0 && m->offset % (8 * align) != 0)
810 return true;
811 }
812
813 /*
814 * if original struct was marked as packed, but its layout is
815 * naturally aligned, we'll detect that it's not packed
816 */
817 return false;
818 }
819
chip_away_bits(int total,int at_most)820 static int chip_away_bits(int total, int at_most)
821 {
822 return total % at_most ? : at_most;
823 }
824
btf_dump_emit_bit_padding(const struct btf_dump * d,int cur_off,int m_off,int m_bit_sz,int align,int lvl)825 static void btf_dump_emit_bit_padding(const struct btf_dump *d,
826 int cur_off, int m_off, int m_bit_sz,
827 int align, int lvl)
828 {
829 int off_diff = m_off - cur_off;
830 int ptr_bits = d->ptr_sz * 8;
831
832 if (off_diff <= 0)
833 /* no gap */
834 return;
835 if (m_bit_sz == 0 && off_diff < align * 8)
836 /* natural padding will take care of a gap */
837 return;
838
839 while (off_diff > 0) {
840 const char *pad_type;
841 int pad_bits;
842
843 if (ptr_bits > 32 && off_diff > 32) {
844 pad_type = "long";
845 pad_bits = chip_away_bits(off_diff, ptr_bits);
846 } else if (off_diff > 16) {
847 pad_type = "int";
848 pad_bits = chip_away_bits(off_diff, 32);
849 } else if (off_diff > 8) {
850 pad_type = "short";
851 pad_bits = chip_away_bits(off_diff, 16);
852 } else {
853 pad_type = "char";
854 pad_bits = chip_away_bits(off_diff, 8);
855 }
856 btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, pad_bits);
857 off_diff -= pad_bits;
858 }
859 }
860
btf_dump_emit_struct_fwd(struct btf_dump * d,__u32 id,const struct btf_type * t)861 static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
862 const struct btf_type *t)
863 {
864 btf_dump_printf(d, "%s %s",
865 btf_is_struct(t) ? "struct" : "union",
866 btf_dump_type_name(d, id));
867 }
868
btf_dump_emit_struct_def(struct btf_dump * d,__u32 id,const struct btf_type * t,int lvl)869 static void btf_dump_emit_struct_def(struct btf_dump *d,
870 __u32 id,
871 const struct btf_type *t,
872 int lvl)
873 {
874 const struct btf_member *m = btf_members(t);
875 bool is_struct = btf_is_struct(t);
876 int align, i, packed, off = 0;
877 __u16 vlen = btf_vlen(t);
878
879 packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0;
880
881 btf_dump_printf(d, "%s%s%s {",
882 is_struct ? "struct" : "union",
883 t->name_off ? " " : "",
884 btf_dump_type_name(d, id));
885
886 for (i = 0; i < vlen; i++, m++) {
887 const char *fname;
888 int m_off, m_sz;
889
890 fname = btf_name_of(d, m->name_off);
891 m_sz = btf_member_bitfield_size(t, i);
892 m_off = btf_member_bit_offset(t, i);
893 align = packed ? 1 : btf__align_of(d->btf, m->type);
894
895 btf_dump_emit_bit_padding(d, off, m_off, m_sz, align, lvl + 1);
896 btf_dump_printf(d, "\n%s", pfx(lvl + 1));
897 btf_dump_emit_type_decl(d, m->type, fname, lvl + 1);
898
899 if (m_sz) {
900 btf_dump_printf(d, ": %d", m_sz);
901 off = m_off + m_sz;
902 } else {
903 m_sz = max((__s64)0, btf__resolve_size(d->btf, m->type));
904 off = m_off + m_sz * 8;
905 }
906 btf_dump_printf(d, ";");
907 }
908
909 /* pad at the end, if necessary */
910 if (is_struct) {
911 align = packed ? 1 : btf__align_of(d->btf, id);
912 btf_dump_emit_bit_padding(d, off, t->size * 8, 0, align,
913 lvl + 1);
914 }
915
916 if (vlen)
917 btf_dump_printf(d, "\n");
918 btf_dump_printf(d, "%s}", pfx(lvl));
919 if (packed)
920 btf_dump_printf(d, " __attribute__((packed))");
921 }
922
923 static const char *missing_base_types[][2] = {
924 /*
925 * GCC emits typedefs to its internal __PolyX_t types when compiling Arm
926 * SIMD intrinsics. Alias them to standard base types.
927 */
928 { "__Poly8_t", "unsigned char" },
929 { "__Poly16_t", "unsigned short" },
930 { "__Poly64_t", "unsigned long long" },
931 { "__Poly128_t", "unsigned __int128" },
932 };
933
btf_dump_emit_missing_aliases(struct btf_dump * d,__u32 id,const struct btf_type * t)934 static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
935 const struct btf_type *t)
936 {
937 const char *name = btf_dump_type_name(d, id);
938 int i;
939
940 for (i = 0; i < ARRAY_SIZE(missing_base_types); i++) {
941 if (strcmp(name, missing_base_types[i][0]) == 0) {
942 btf_dump_printf(d, "typedef %s %s;\n\n",
943 missing_base_types[i][1], name);
944 break;
945 }
946 }
947 }
948
btf_dump_emit_enum_fwd(struct btf_dump * d,__u32 id,const struct btf_type * t)949 static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
950 const struct btf_type *t)
951 {
952 btf_dump_printf(d, "enum %s", btf_dump_type_name(d, id));
953 }
954
btf_dump_emit_enum_def(struct btf_dump * d,__u32 id,const struct btf_type * t,int lvl)955 static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
956 const struct btf_type *t,
957 int lvl)
958 {
959 const struct btf_enum *v = btf_enum(t);
960 __u16 vlen = btf_vlen(t);
961 const char *name;
962 size_t dup_cnt;
963 int i;
964
965 btf_dump_printf(d, "enum%s%s",
966 t->name_off ? " " : "",
967 btf_dump_type_name(d, id));
968
969 if (vlen) {
970 btf_dump_printf(d, " {");
971 for (i = 0; i < vlen; i++, v++) {
972 name = btf_name_of(d, v->name_off);
973 /* enumerators share namespace with typedef idents */
974 dup_cnt = btf_dump_name_dups(d, d->ident_names, name);
975 if (dup_cnt > 1) {
976 btf_dump_printf(d, "\n%s%s___%zu = %u,",
977 pfx(lvl + 1), name, dup_cnt,
978 (__u32)v->val);
979 } else {
980 btf_dump_printf(d, "\n%s%s = %u,",
981 pfx(lvl + 1), name,
982 (__u32)v->val);
983 }
984 }
985 btf_dump_printf(d, "\n%s}", pfx(lvl));
986 }
987 }
988
btf_dump_emit_fwd_def(struct btf_dump * d,__u32 id,const struct btf_type * t)989 static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
990 const struct btf_type *t)
991 {
992 const char *name = btf_dump_type_name(d, id);
993
994 if (btf_kflag(t))
995 btf_dump_printf(d, "union %s", name);
996 else
997 btf_dump_printf(d, "struct %s", name);
998 }
999
btf_dump_emit_typedef_def(struct btf_dump * d,__u32 id,const struct btf_type * t,int lvl)1000 static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
1001 const struct btf_type *t, int lvl)
1002 {
1003 const char *name = btf_dump_ident_name(d, id);
1004
1005 /*
1006 * Old GCC versions are emitting invalid typedef for __gnuc_va_list
1007 * pointing to VOID. This generates warnings from btf_dump() and
1008 * results in uncompilable header file, so we are fixing it up here
1009 * with valid typedef into __builtin_va_list.
1010 */
1011 if (t->type == 0 && strcmp(name, "__gnuc_va_list") == 0) {
1012 btf_dump_printf(d, "typedef __builtin_va_list __gnuc_va_list");
1013 return;
1014 }
1015
1016 btf_dump_printf(d, "typedef ");
1017 btf_dump_emit_type_decl(d, t->type, name, lvl);
1018 }
1019
btf_dump_push_decl_stack_id(struct btf_dump * d,__u32 id)1020 static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id)
1021 {
1022 __u32 *new_stack;
1023 size_t new_cap;
1024
1025 if (d->decl_stack_cnt >= d->decl_stack_cap) {
1026 new_cap = max(16, d->decl_stack_cap * 3 / 2);
1027 new_stack = libbpf_reallocarray(d->decl_stack, new_cap, sizeof(new_stack[0]));
1028 if (!new_stack)
1029 return -ENOMEM;
1030 d->decl_stack = new_stack;
1031 d->decl_stack_cap = new_cap;
1032 }
1033
1034 d->decl_stack[d->decl_stack_cnt++] = id;
1035
1036 return 0;
1037 }
1038
1039 /*
1040 * Emit type declaration (e.g., field type declaration in a struct or argument
1041 * declaration in function prototype) in correct C syntax.
1042 *
1043 * For most types it's trivial, but there are few quirky type declaration
1044 * cases worth mentioning:
1045 * - function prototypes (especially nesting of function prototypes);
1046 * - arrays;
1047 * - const/volatile/restrict for pointers vs other types.
1048 *
1049 * For a good discussion of *PARSING* C syntax (as a human), see
1050 * Peter van der Linden's "Expert C Programming: Deep C Secrets",
1051 * Ch.3 "Unscrambling Declarations in C".
1052 *
1053 * It won't help with BTF to C conversion much, though, as it's an opposite
1054 * problem. So we came up with this algorithm in reverse to van der Linden's
1055 * parsing algorithm. It goes from structured BTF representation of type
1056 * declaration to a valid compilable C syntax.
1057 *
1058 * For instance, consider this C typedef:
1059 * typedef const int * const * arr[10] arr_t;
1060 * It will be represented in BTF with this chain of BTF types:
1061 * [typedef] -> [array] -> [ptr] -> [const] -> [ptr] -> [const] -> [int]
1062 *
1063 * Notice how [const] modifier always goes before type it modifies in BTF type
1064 * graph, but in C syntax, const/volatile/restrict modifiers are written to
1065 * the right of pointers, but to the left of other types. There are also other
1066 * quirks, like function pointers, arrays of them, functions returning other
1067 * functions, etc.
1068 *
1069 * We handle that by pushing all the types to a stack, until we hit "terminal"
1070 * type (int/enum/struct/union/fwd). Then depending on the kind of a type on
1071 * top of a stack, modifiers are handled differently. Array/function pointers
1072 * have also wildly different syntax and how nesting of them are done. See
1073 * code for authoritative definition.
1074 *
1075 * To avoid allocating new stack for each independent chain of BTF types, we
1076 * share one bigger stack, with each chain working only on its own local view
1077 * of a stack frame. Some care is required to "pop" stack frames after
1078 * processing type declaration chain.
1079 */
btf_dump__emit_type_decl(struct btf_dump * d,__u32 id,const struct btf_dump_emit_type_decl_opts * opts)1080 int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
1081 const struct btf_dump_emit_type_decl_opts *opts)
1082 {
1083 const char *fname;
1084 int lvl, err;
1085
1086 if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts))
1087 return -EINVAL;
1088
1089 err = btf_dump_resize(d);
1090 if (err)
1091 return -EINVAL;
1092
1093 fname = OPTS_GET(opts, field_name, "");
1094 lvl = OPTS_GET(opts, indent_level, 0);
1095 d->strip_mods = OPTS_GET(opts, strip_mods, false);
1096 btf_dump_emit_type_decl(d, id, fname, lvl);
1097 d->strip_mods = false;
1098 return 0;
1099 }
1100
btf_dump_emit_type_decl(struct btf_dump * d,__u32 id,const char * fname,int lvl)1101 static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
1102 const char *fname, int lvl)
1103 {
1104 struct id_stack decl_stack;
1105 const struct btf_type *t;
1106 int err, stack_start;
1107
1108 stack_start = d->decl_stack_cnt;
1109 for (;;) {
1110 t = btf__type_by_id(d->btf, id);
1111 if (d->strip_mods && btf_is_mod(t))
1112 goto skip_mod;
1113
1114 err = btf_dump_push_decl_stack_id(d, id);
1115 if (err < 0) {
1116 /*
1117 * if we don't have enough memory for entire type decl
1118 * chain, restore stack, emit warning, and try to
1119 * proceed nevertheless
1120 */
1121 pr_warn("not enough memory for decl stack:%d", err);
1122 d->decl_stack_cnt = stack_start;
1123 return;
1124 }
1125 skip_mod:
1126 /* VOID */
1127 if (id == 0)
1128 break;
1129
1130 switch (btf_kind(t)) {
1131 case BTF_KIND_PTR:
1132 case BTF_KIND_VOLATILE:
1133 case BTF_KIND_CONST:
1134 case BTF_KIND_RESTRICT:
1135 case BTF_KIND_FUNC_PROTO:
1136 id = t->type;
1137 break;
1138 case BTF_KIND_ARRAY:
1139 id = btf_array(t)->type;
1140 break;
1141 case BTF_KIND_INT:
1142 case BTF_KIND_ENUM:
1143 case BTF_KIND_FWD:
1144 case BTF_KIND_STRUCT:
1145 case BTF_KIND_UNION:
1146 case BTF_KIND_TYPEDEF:
1147 goto done;
1148 default:
1149 pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
1150 btf_kind(t), id);
1151 goto done;
1152 }
1153 }
1154 done:
1155 /*
1156 * We might be inside a chain of declarations (e.g., array of function
1157 * pointers returning anonymous (so inlined) structs, having another
1158 * array field). Each of those needs its own "stack frame" to handle
1159 * emitting of declarations. Those stack frames are non-overlapping
1160 * portions of shared btf_dump->decl_stack. To make it a bit nicer to
1161 * handle this set of nested stacks, we create a view corresponding to
1162 * our own "stack frame" and work with it as an independent stack.
1163 * We'll need to clean up after emit_type_chain() returns, though.
1164 */
1165 decl_stack.ids = d->decl_stack + stack_start;
1166 decl_stack.cnt = d->decl_stack_cnt - stack_start;
1167 btf_dump_emit_type_chain(d, &decl_stack, fname, lvl);
1168 /*
1169 * emit_type_chain() guarantees that it will pop its entire decl_stack
1170 * frame before returning. But it works with a read-only view into
1171 * decl_stack, so it doesn't actually pop anything from the
1172 * perspective of shared btf_dump->decl_stack, per se. We need to
1173 * reset decl_stack state to how it was before us to avoid it growing
1174 * all the time.
1175 */
1176 d->decl_stack_cnt = stack_start;
1177 }
1178
btf_dump_emit_mods(struct btf_dump * d,struct id_stack * decl_stack)1179 static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack)
1180 {
1181 const struct btf_type *t;
1182 __u32 id;
1183
1184 while (decl_stack->cnt) {
1185 id = decl_stack->ids[decl_stack->cnt - 1];
1186 t = btf__type_by_id(d->btf, id);
1187
1188 switch (btf_kind(t)) {
1189 case BTF_KIND_VOLATILE:
1190 btf_dump_printf(d, "volatile ");
1191 break;
1192 case BTF_KIND_CONST:
1193 btf_dump_printf(d, "const ");
1194 break;
1195 case BTF_KIND_RESTRICT:
1196 btf_dump_printf(d, "restrict ");
1197 break;
1198 default:
1199 return;
1200 }
1201 decl_stack->cnt--;
1202 }
1203 }
1204
btf_dump_drop_mods(struct btf_dump * d,struct id_stack * decl_stack)1205 static void btf_dump_drop_mods(struct btf_dump *d, struct id_stack *decl_stack)
1206 {
1207 const struct btf_type *t;
1208 __u32 id;
1209
1210 while (decl_stack->cnt) {
1211 id = decl_stack->ids[decl_stack->cnt - 1];
1212 t = btf__type_by_id(d->btf, id);
1213 if (!btf_is_mod(t))
1214 return;
1215 decl_stack->cnt--;
1216 }
1217 }
1218
btf_dump_emit_name(const struct btf_dump * d,const char * name,bool last_was_ptr)1219 static void btf_dump_emit_name(const struct btf_dump *d,
1220 const char *name, bool last_was_ptr)
1221 {
1222 bool separate = name[0] && !last_was_ptr;
1223
1224 btf_dump_printf(d, "%s%s", separate ? " " : "", name);
1225 }
1226
btf_dump_emit_type_chain(struct btf_dump * d,struct id_stack * decls,const char * fname,int lvl)1227 static void btf_dump_emit_type_chain(struct btf_dump *d,
1228 struct id_stack *decls,
1229 const char *fname, int lvl)
1230 {
1231 /*
1232 * last_was_ptr is used to determine if we need to separate pointer
1233 * asterisk (*) from previous part of type signature with space, so
1234 * that we get `int ***`, instead of `int * * *`. We default to true
1235 * for cases where we have single pointer in a chain. E.g., in ptr ->
1236 * func_proto case. func_proto will start a new emit_type_chain call
1237 * with just ptr, which should be emitted as (*) or (*<fname>), so we
1238 * don't want to prepend space for that last pointer.
1239 */
1240 bool last_was_ptr = true;
1241 const struct btf_type *t;
1242 const char *name;
1243 __u16 kind;
1244 __u32 id;
1245
1246 while (decls->cnt) {
1247 id = decls->ids[--decls->cnt];
1248 if (id == 0) {
1249 /* VOID is a special snowflake */
1250 btf_dump_emit_mods(d, decls);
1251 btf_dump_printf(d, "void");
1252 last_was_ptr = false;
1253 continue;
1254 }
1255
1256 t = btf__type_by_id(d->btf, id);
1257 kind = btf_kind(t);
1258
1259 switch (kind) {
1260 case BTF_KIND_INT:
1261 btf_dump_emit_mods(d, decls);
1262 name = btf_name_of(d, t->name_off);
1263 btf_dump_printf(d, "%s", name);
1264 break;
1265 case BTF_KIND_STRUCT:
1266 case BTF_KIND_UNION:
1267 btf_dump_emit_mods(d, decls);
1268 /* inline anonymous struct/union */
1269 if (t->name_off == 0)
1270 btf_dump_emit_struct_def(d, id, t, lvl);
1271 else
1272 btf_dump_emit_struct_fwd(d, id, t);
1273 break;
1274 case BTF_KIND_ENUM:
1275 btf_dump_emit_mods(d, decls);
1276 /* inline anonymous enum */
1277 if (t->name_off == 0)
1278 btf_dump_emit_enum_def(d, id, t, lvl);
1279 else
1280 btf_dump_emit_enum_fwd(d, id, t);
1281 break;
1282 case BTF_KIND_FWD:
1283 btf_dump_emit_mods(d, decls);
1284 btf_dump_emit_fwd_def(d, id, t);
1285 break;
1286 case BTF_KIND_TYPEDEF:
1287 btf_dump_emit_mods(d, decls);
1288 btf_dump_printf(d, "%s", btf_dump_ident_name(d, id));
1289 break;
1290 case BTF_KIND_PTR:
1291 btf_dump_printf(d, "%s", last_was_ptr ? "*" : " *");
1292 break;
1293 case BTF_KIND_VOLATILE:
1294 btf_dump_printf(d, " volatile");
1295 break;
1296 case BTF_KIND_CONST:
1297 btf_dump_printf(d, " const");
1298 break;
1299 case BTF_KIND_RESTRICT:
1300 btf_dump_printf(d, " restrict");
1301 break;
1302 case BTF_KIND_ARRAY: {
1303 const struct btf_array *a = btf_array(t);
1304 const struct btf_type *next_t;
1305 __u32 next_id;
1306 bool multidim;
1307 /*
1308 * GCC has a bug
1309 * (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8354)
1310 * which causes it to emit extra const/volatile
1311 * modifiers for an array, if array's element type has
1312 * const/volatile modifiers. Clang doesn't do that.
1313 * In general, it doesn't seem very meaningful to have
1314 * a const/volatile modifier for array, so we are
1315 * going to silently skip them here.
1316 */
1317 btf_dump_drop_mods(d, decls);
1318
1319 if (decls->cnt == 0) {
1320 btf_dump_emit_name(d, fname, last_was_ptr);
1321 btf_dump_printf(d, "[%u]", a->nelems);
1322 return;
1323 }
1324
1325 next_id = decls->ids[decls->cnt - 1];
1326 next_t = btf__type_by_id(d->btf, next_id);
1327 multidim = btf_is_array(next_t);
1328 /* we need space if we have named non-pointer */
1329 if (fname[0] && !last_was_ptr)
1330 btf_dump_printf(d, " ");
1331 /* no parentheses for multi-dimensional array */
1332 if (!multidim)
1333 btf_dump_printf(d, "(");
1334 btf_dump_emit_type_chain(d, decls, fname, lvl);
1335 if (!multidim)
1336 btf_dump_printf(d, ")");
1337 btf_dump_printf(d, "[%u]", a->nelems);
1338 return;
1339 }
1340 case BTF_KIND_FUNC_PROTO: {
1341 const struct btf_param *p = btf_params(t);
1342 __u16 vlen = btf_vlen(t);
1343 int i;
1344
1345 /*
1346 * GCC emits extra volatile qualifier for
1347 * __attribute__((noreturn)) function pointers. Clang
1348 * doesn't do it. It's a GCC quirk for backwards
1349 * compatibility with code written for GCC <2.5. So,
1350 * similarly to extra qualifiers for array, just drop
1351 * them, instead of handling them.
1352 */
1353 btf_dump_drop_mods(d, decls);
1354 if (decls->cnt) {
1355 btf_dump_printf(d, " (");
1356 btf_dump_emit_type_chain(d, decls, fname, lvl);
1357 btf_dump_printf(d, ")");
1358 } else {
1359 btf_dump_emit_name(d, fname, last_was_ptr);
1360 }
1361 btf_dump_printf(d, "(");
1362 /*
1363 * Clang for BPF target generates func_proto with no
1364 * args as a func_proto with a single void arg (e.g.,
1365 * `int (*f)(void)` vs just `int (*f)()`). We are
1366 * going to pretend there are no args for such case.
1367 */
1368 if (vlen == 1 && p->type == 0) {
1369 btf_dump_printf(d, ")");
1370 return;
1371 }
1372
1373 for (i = 0; i < vlen; i++, p++) {
1374 if (i > 0)
1375 btf_dump_printf(d, ", ");
1376
1377 /* last arg of type void is vararg */
1378 if (i == vlen - 1 && p->type == 0) {
1379 btf_dump_printf(d, "...");
1380 break;
1381 }
1382
1383 name = btf_name_of(d, p->name_off);
1384 btf_dump_emit_type_decl(d, p->type, name, lvl);
1385 }
1386
1387 btf_dump_printf(d, ")");
1388 return;
1389 }
1390 default:
1391 pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
1392 kind, id);
1393 return;
1394 }
1395
1396 last_was_ptr = kind == BTF_KIND_PTR;
1397 }
1398
1399 btf_dump_emit_name(d, fname, last_was_ptr);
1400 }
1401
1402 /* return number of duplicates (occurrences) of a given name */
btf_dump_name_dups(struct btf_dump * d,struct hashmap * name_map,const char * orig_name)1403 static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
1404 const char *orig_name)
1405 {
1406 char *old_name, *new_name;
1407 size_t dup_cnt = 0;
1408 int err;
1409
1410 new_name = strdup(orig_name);
1411 if (!new_name)
1412 return 1;
1413
1414 hashmap__find(name_map, orig_name, (void **)&dup_cnt);
1415 dup_cnt++;
1416
1417 err = hashmap__set(name_map, new_name, (void *)dup_cnt,
1418 (const void **)&old_name, NULL);
1419 if (err)
1420 free(new_name);
1421
1422 free(old_name);
1423
1424 return dup_cnt;
1425 }
1426
btf_dump_resolve_name(struct btf_dump * d,__u32 id,struct hashmap * name_map)1427 static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id,
1428 struct hashmap *name_map)
1429 {
1430 struct btf_dump_type_aux_state *s = &d->type_states[id];
1431 const struct btf_type *t = btf__type_by_id(d->btf, id);
1432 const char *orig_name = btf_name_of(d, t->name_off);
1433 const char **cached_name = &d->cached_names[id];
1434 size_t dup_cnt;
1435
1436 if (t->name_off == 0)
1437 return "";
1438
1439 if (s->name_resolved)
1440 return *cached_name ? *cached_name : orig_name;
1441
1442 dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
1443 if (dup_cnt > 1) {
1444 const size_t max_len = 256;
1445 char new_name[max_len];
1446
1447 snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt);
1448 *cached_name = strdup(new_name);
1449 }
1450
1451 s->name_resolved = 1;
1452 return *cached_name ? *cached_name : orig_name;
1453 }
1454
btf_dump_type_name(struct btf_dump * d,__u32 id)1455 static const char *btf_dump_type_name(struct btf_dump *d, __u32 id)
1456 {
1457 return btf_dump_resolve_name(d, id, d->type_names);
1458 }
1459
btf_dump_ident_name(struct btf_dump * d,__u32 id)1460 static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id)
1461 {
1462 return btf_dump_resolve_name(d, id, d->ident_names);
1463 }
1464