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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
22static const char PREFIXES[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t";
23static const size_t PREFIX_CNT = sizeof(PREFIXES) - 1;
24
25static const char *pfx(int lvl)
26{
27 return lvl >= PREFIX_CNT ? PREFIXES : &PREFIXES[PREFIX_CNT - lvl];
28}
29
30enum btf_dump_type_order_state {
31 NOT_ORDERED,
32 ORDERING,
33 ORDERED,
34};
35
36enum btf_dump_type_emit_state {
37 NOT_EMITTED,
38 EMITTING,
39 EMITTED,
40};
41
42/* per-type auxiliary state */
43struct 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
56struct 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
94static size_t str_hash_fn(const void *key, void *ctx)
95{
96 return str_hash(key);
97}
98
99static bool str_equal_fn(const void *a, const void *b, void *ctx)
100{
101 return strcmp(a, b) == 0;
102}
103
104static 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
109static 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
118static int btf_dump_mark_referenced(struct btf_dump *d);
119static int btf_dump_resize(struct btf_dump *d);
120
121struct 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 libbpf_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;
157err:
158 btf_dump__free(d);
159 return libbpf_err_ptr(err);
160}
161
162static 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 (libbpf_ensure_mem((void **)&d->type_states, &d->type_states_cap,
170 sizeof(*d->type_states), last_id + 1))
171 return -ENOMEM;
172 if (libbpf_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
191void btf_dump__free(struct btf_dump *d)
192{
193 int i;
194
195 if (IS_ERR_OR_NULL(d))
196 return;
197
198 free(d->type_states);
199 if (d->cached_names) {
200 /* any set cached name is owned by us and should be freed */
201 for (i = 0; i <= d->last_id; i++) {
202 if (d->cached_names[i])
203 free((void *)d->cached_names[i]);
204 }
205 }
206 free(d->cached_names);
207 free(d->emit_queue);
208 free(d->decl_stack);
209 hashmap__free(d->type_names);
210 hashmap__free(d->ident_names);
211
212 free(d);
213}
214
215static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr);
216static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id);
217
218/*
219 * Dump BTF type in a compilable C syntax, including all the necessary
220 * dependent types, necessary for compilation. If some of the dependent types
221 * were already emitted as part of previous btf_dump__dump_type() invocation
222 * for another type, they won't be emitted again. This API allows callers to
223 * filter out BTF types according to user-defined criterias and emitted only
224 * minimal subset of types, necessary to compile everything. Full struct/union
225 * definitions will still be emitted, even if the only usage is through
226 * pointer and could be satisfied with just a forward declaration.
227 *
228 * Dumping is done in two high-level passes:
229 * 1. Topologically sort type definitions to satisfy C rules of compilation.
230 * 2. Emit type definitions in C syntax.
231 *
232 * Returns 0 on success; <0, otherwise.
233 */
234int btf_dump__dump_type(struct btf_dump *d, __u32 id)
235{
236 int err, i;
237
238 if (id > btf__get_nr_types(d->btf))
239 return libbpf_err(-EINVAL);
240
241 err = btf_dump_resize(d);
242 if (err)
243 return libbpf_err(err);
244
245 d->emit_queue_cnt = 0;
246 err = btf_dump_order_type(d, id, false);
247 if (err < 0)
248 return libbpf_err(err);
249
250 for (i = 0; i < d->emit_queue_cnt; i++)
251 btf_dump_emit_type(d, d->emit_queue[i], 0 /*top-level*/);
252
253 return 0;
254}
255
256/*
257 * Mark all types that are referenced from any other type. This is used to
258 * determine top-level anonymous enums that need to be emitted as an
259 * independent type declarations.
260 * Anonymous enums come in two flavors: either embedded in a struct's field
261 * definition, in which case they have to be declared inline as part of field
262 * type declaration; or as a top-level anonymous enum, typically used for
263 * declaring global constants. It's impossible to distinguish between two
264 * without knowning whether given enum type was referenced from other type:
265 * top-level anonymous enum won't be referenced by anything, while embedded
266 * one will.
267 */
268static int btf_dump_mark_referenced(struct btf_dump *d)
269{
270 int i, j, n = btf__get_nr_types(d->btf);
271 const struct btf_type *t;
272 __u16 vlen;
273
274 for (i = d->last_id + 1; i <= n; i++) {
275 t = btf__type_by_id(d->btf, i);
276 vlen = btf_vlen(t);
277
278 switch (btf_kind(t)) {
279 case BTF_KIND_INT:
280 case BTF_KIND_ENUM:
281 case BTF_KIND_FWD:
282 case BTF_KIND_FLOAT:
283 break;
284
285 case BTF_KIND_VOLATILE:
286 case BTF_KIND_CONST:
287 case BTF_KIND_RESTRICT:
288 case BTF_KIND_PTR:
289 case BTF_KIND_TYPEDEF:
290 case BTF_KIND_FUNC:
291 case BTF_KIND_VAR:
292 d->type_states[t->type].referenced = 1;
293 break;
294
295 case BTF_KIND_ARRAY: {
296 const struct btf_array *a = btf_array(t);
297
298 d->type_states[a->index_type].referenced = 1;
299 d->type_states[a->type].referenced = 1;
300 break;
301 }
302 case BTF_KIND_STRUCT:
303 case BTF_KIND_UNION: {
304 const struct btf_member *m = btf_members(t);
305
306 for (j = 0; j < vlen; j++, m++)
307 d->type_states[m->type].referenced = 1;
308 break;
309 }
310 case BTF_KIND_FUNC_PROTO: {
311 const struct btf_param *p = btf_params(t);
312
313 for (j = 0; j < vlen; j++, p++)
314 d->type_states[p->type].referenced = 1;
315 break;
316 }
317 case BTF_KIND_DATASEC: {
318 const struct btf_var_secinfo *v = btf_var_secinfos(t);
319
320 for (j = 0; j < vlen; j++, v++)
321 d->type_states[v->type].referenced = 1;
322 break;
323 }
324 default:
325 return -EINVAL;
326 }
327 }
328 return 0;
329}
330
331static int btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id)
332{
333 __u32 *new_queue;
334 size_t new_cap;
335
336 if (d->emit_queue_cnt >= d->emit_queue_cap) {
337 new_cap = max(16, d->emit_queue_cap * 3 / 2);
338 new_queue = libbpf_reallocarray(d->emit_queue, new_cap, sizeof(new_queue[0]));
339 if (!new_queue)
340 return -ENOMEM;
341 d->emit_queue = new_queue;
342 d->emit_queue_cap = new_cap;
343 }
344
345 d->emit_queue[d->emit_queue_cnt++] = id;
346 return 0;
347}
348
349/*
350 * Determine order of emitting dependent types and specified type to satisfy
351 * C compilation rules. This is done through topological sorting with an
352 * additional complication which comes from C rules. The main idea for C is
353 * that if some type is "embedded" into a struct/union, it's size needs to be
354 * known at the time of definition of containing type. E.g., for:
355 *
356 * struct A {};
357 * struct B { struct A x; }
358 *
359 * struct A *HAS* to be defined before struct B, because it's "embedded",
360 * i.e., it is part of struct B layout. But in the following case:
361 *
362 * struct A;
363 * struct B { struct A *x; }
364 * struct A {};
365 *
366 * it's enough to just have a forward declaration of struct A at the time of
367 * struct B definition, as struct B has a pointer to struct A, so the size of
368 * field x is known without knowing struct A size: it's sizeof(void *).
369 *
370 * Unfortunately, there are some trickier cases we need to handle, e.g.:
371 *
372 * struct A {}; // if this was forward-declaration: compilation error
373 * struct B {
374 * struct { // anonymous struct
375 * struct A y;
376 * } *x;
377 * };
378 *
379 * In this case, struct B's field x is a pointer, so it's size is known
380 * regardless of the size of (anonymous) struct it points to. But because this
381 * struct is anonymous and thus defined inline inside struct B, *and* it
382 * embeds struct A, compiler requires full definition of struct A to be known
383 * before struct B can be defined. This creates a transitive dependency
384 * between struct A and struct B. If struct A was forward-declared before
385 * struct B definition and fully defined after struct B definition, that would
386 * trigger compilation error.
387 *
388 * All this means that while we are doing topological sorting on BTF type
389 * graph, we need to determine relationships between different types (graph
390 * nodes):
391 * - weak link (relationship) between X and Y, if Y *CAN* be
392 * forward-declared at the point of X definition;
393 * - strong link, if Y *HAS* to be fully-defined before X can be defined.
394 *
395 * The rule is as follows. Given a chain of BTF types from X to Y, if there is
396 * BTF_KIND_PTR type in the chain and at least one non-anonymous type
397 * Z (excluding X, including Y), then link is weak. Otherwise, it's strong.
398 * Weak/strong relationship is determined recursively during DFS traversal and
399 * is returned as a result from btf_dump_order_type().
400 *
401 * btf_dump_order_type() is trying to avoid unnecessary forward declarations,
402 * but it is not guaranteeing that no extraneous forward declarations will be
403 * emitted.
404 *
405 * To avoid extra work, algorithm marks some of BTF types as ORDERED, when
406 * it's done with them, but not for all (e.g., VOLATILE, CONST, RESTRICT,
407 * ARRAY, FUNC_PROTO), as weak/strong semantics for those depends on the
408 * entire graph path, so depending where from one came to that BTF type, it
409 * might cause weak or strong ordering. For types like STRUCT/UNION/INT/ENUM,
410 * once they are processed, there is no need to do it again, so they are
411 * marked as ORDERED. We can mark PTR as ORDERED as well, as it semi-forces
412 * weak link, unless subsequent referenced STRUCT/UNION/ENUM is anonymous. But
413 * in any case, once those are processed, no need to do it again, as the
414 * result won't change.
415 *
416 * Returns:
417 * - 1, if type is part of strong link (so there is strong topological
418 * ordering requirements);
419 * - 0, if type is part of weak link (so can be satisfied through forward
420 * declaration);
421 * - <0, on error (e.g., unsatisfiable type loop detected).
422 */
423static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
424{
425 /*
426 * Order state is used to detect strong link cycles, but only for BTF
427 * kinds that are or could be an independent definition (i.e.,
428 * stand-alone fwd decl, enum, typedef, struct, union). Ptrs, arrays,
429 * func_protos, modifiers are just means to get to these definitions.
430 * Int/void don't need definitions, they are assumed to be always
431 * properly defined. We also ignore datasec, var, and funcs for now.
432 * So for all non-defining kinds, we never even set ordering state,
433 * for defining kinds we set ORDERING and subsequently ORDERED if it
434 * forms a strong link.
435 */
436 struct btf_dump_type_aux_state *tstate = &d->type_states[id];
437 const struct btf_type *t;
438 __u16 vlen;
439 int err, i;
440
441 /* return true, letting typedefs know that it's ok to be emitted */
442 if (tstate->order_state == ORDERED)
443 return 1;
444
445 t = btf__type_by_id(d->btf, id);
446
447 if (tstate->order_state == ORDERING) {
448 /* type loop, but resolvable through fwd declaration */
449 if (btf_is_composite(t) && through_ptr && t->name_off != 0)
450 return 0;
451 pr_warn("unsatisfiable type cycle, id:[%u]\n", id);
452 return -ELOOP;
453 }
454
455 switch (btf_kind(t)) {
456 case BTF_KIND_INT:
457 case BTF_KIND_FLOAT:
458 tstate->order_state = ORDERED;
459 return 0;
460
461 case BTF_KIND_PTR:
462 err = btf_dump_order_type(d, t->type, true);
463 tstate->order_state = ORDERED;
464 return err;
465
466 case BTF_KIND_ARRAY:
467 return btf_dump_order_type(d, btf_array(t)->type, false);
468
469 case BTF_KIND_STRUCT:
470 case BTF_KIND_UNION: {
471 const struct btf_member *m = btf_members(t);
472 /*
473 * struct/union is part of strong link, only if it's embedded
474 * (so no ptr in a path) or it's anonymous (so has to be
475 * defined inline, even if declared through ptr)
476 */
477 if (through_ptr && t->name_off != 0)
478 return 0;
479
480 tstate->order_state = ORDERING;
481
482 vlen = btf_vlen(t);
483 for (i = 0; i < vlen; i++, m++) {
484 err = btf_dump_order_type(d, m->type, false);
485 if (err < 0)
486 return err;
487 }
488
489 if (t->name_off != 0) {
490 err = btf_dump_add_emit_queue_id(d, id);
491 if (err < 0)
492 return err;
493 }
494
495 tstate->order_state = ORDERED;
496 return 1;
497 }
498 case BTF_KIND_ENUM:
499 case BTF_KIND_FWD:
500 /*
501 * non-anonymous or non-referenced enums are top-level
502 * declarations and should be emitted. Same logic can be
503 * applied to FWDs, it won't hurt anyways.
504 */
505 if (t->name_off != 0 || !tstate->referenced) {
506 err = btf_dump_add_emit_queue_id(d, id);
507 if (err)
508 return err;
509 }
510 tstate->order_state = ORDERED;
511 return 1;
512
513 case BTF_KIND_TYPEDEF: {
514 int is_strong;
515
516 is_strong = btf_dump_order_type(d, t->type, through_ptr);
517 if (is_strong < 0)
518 return is_strong;
519
520 /* typedef is similar to struct/union w.r.t. fwd-decls */
521 if (through_ptr && !is_strong)
522 return 0;
523
524 /* typedef is always a named definition */
525 err = btf_dump_add_emit_queue_id(d, id);
526 if (err)
527 return err;
528
529 d->type_states[id].order_state = ORDERED;
530 return 1;
531 }
532 case BTF_KIND_VOLATILE:
533 case BTF_KIND_CONST:
534 case BTF_KIND_RESTRICT:
535 return btf_dump_order_type(d, t->type, through_ptr);
536
537 case BTF_KIND_FUNC_PROTO: {
538 const struct btf_param *p = btf_params(t);
539 bool is_strong;
540
541 err = btf_dump_order_type(d, t->type, through_ptr);
542 if (err < 0)
543 return err;
544 is_strong = err > 0;
545
546 vlen = btf_vlen(t);
547 for (i = 0; i < vlen; i++, p++) {
548 err = btf_dump_order_type(d, p->type, through_ptr);
549 if (err < 0)
550 return err;
551 if (err > 0)
552 is_strong = true;
553 }
554 return is_strong;
555 }
556 case BTF_KIND_FUNC:
557 case BTF_KIND_VAR:
558 case BTF_KIND_DATASEC:
559 d->type_states[id].order_state = ORDERED;
560 return 0;
561
562 default:
563 return -EINVAL;
564 }
565}
566
567static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
568 const struct btf_type *t);
569
570static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
571 const struct btf_type *t);
572static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id,
573 const struct btf_type *t, int lvl);
574
575static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
576 const struct btf_type *t);
577static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
578 const struct btf_type *t, int lvl);
579
580static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
581 const struct btf_type *t);
582
583static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
584 const struct btf_type *t, int lvl);
585
586/* a local view into a shared stack */
587struct id_stack {
588 const __u32 *ids;
589 int cnt;
590};
591
592static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
593 const char *fname, int lvl);
594static void btf_dump_emit_type_chain(struct btf_dump *d,
595 struct id_stack *decl_stack,
596 const char *fname, int lvl);
597
598static const char *btf_dump_type_name(struct btf_dump *d, __u32 id);
599static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id);
600static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
601 const char *orig_name);
602
603static bool btf_dump_is_blacklisted(struct btf_dump *d, __u32 id)
604{
605 const struct btf_type *t = btf__type_by_id(d->btf, id);
606
607 /* __builtin_va_list is a compiler built-in, which causes compilation
608 * errors, when compiling w/ different compiler, then used to compile
609 * original code (e.g., GCC to compile kernel, Clang to use generated
610 * C header from BTF). As it is built-in, it should be already defined
611 * properly internally in compiler.
612 */
613 if (t->name_off == 0)
614 return false;
615 return strcmp(btf_name_of(d, t->name_off), "__builtin_va_list") == 0;
616}
617
618/*
619 * Emit C-syntax definitions of types from chains of BTF types.
620 *
621 * High-level handling of determining necessary forward declarations are handled
622 * by btf_dump_emit_type() itself, but all nitty-gritty details of emitting type
623 * declarations/definitions in C syntax are handled by a combo of
624 * btf_dump_emit_type_decl()/btf_dump_emit_type_chain() w/ delegation to
625 * corresponding btf_dump_emit_*_{def,fwd}() functions.
626 *
627 * We also keep track of "containing struct/union type ID" to determine when
628 * we reference it from inside and thus can avoid emitting unnecessary forward
629 * declaration.
630 *
631 * This algorithm is designed in such a way, that even if some error occurs
632 * (either technical, e.g., out of memory, or logical, i.e., malformed BTF
633 * that doesn't comply to C rules completely), algorithm will try to proceed
634 * and produce as much meaningful output as possible.
635 */
636static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
637{
638 struct btf_dump_type_aux_state *tstate = &d->type_states[id];
639 bool top_level_def = cont_id == 0;
640 const struct btf_type *t;
641 __u16 kind;
642
643 if (tstate->emit_state == EMITTED)
644 return;
645
646 t = btf__type_by_id(d->btf, id);
647 kind = btf_kind(t);
648
649 if (tstate->emit_state == EMITTING) {
650 if (tstate->fwd_emitted)
651 return;
652
653 switch (kind) {
654 case BTF_KIND_STRUCT:
655 case BTF_KIND_UNION:
656 /*
657 * if we are referencing a struct/union that we are
658 * part of - then no need for fwd declaration
659 */
660 if (id == cont_id)
661 return;
662 if (t->name_off == 0) {
663 pr_warn("anonymous struct/union loop, id:[%u]\n",
664 id);
665 return;
666 }
667 btf_dump_emit_struct_fwd(d, id, t);
668 btf_dump_printf(d, ";\n\n");
669 tstate->fwd_emitted = 1;
670 break;
671 case BTF_KIND_TYPEDEF:
672 /*
673 * for typedef fwd_emitted means typedef definition
674 * was emitted, but it can be used only for "weak"
675 * references through pointer only, not for embedding
676 */
677 if (!btf_dump_is_blacklisted(d, id)) {
678 btf_dump_emit_typedef_def(d, id, t, 0);
679 btf_dump_printf(d, ";\n\n");
680 }
681 tstate->fwd_emitted = 1;
682 break;
683 default:
684 break;
685 }
686
687 return;
688 }
689
690 switch (kind) {
691 case BTF_KIND_INT:
692 /* Emit type alias definitions if necessary */
693 btf_dump_emit_missing_aliases(d, id, t);
694
695 tstate->emit_state = EMITTED;
696 break;
697 case BTF_KIND_ENUM:
698 if (top_level_def) {
699 btf_dump_emit_enum_def(d, id, t, 0);
700 btf_dump_printf(d, ";\n\n");
701 }
702 tstate->emit_state = EMITTED;
703 break;
704 case BTF_KIND_PTR:
705 case BTF_KIND_VOLATILE:
706 case BTF_KIND_CONST:
707 case BTF_KIND_RESTRICT:
708 btf_dump_emit_type(d, t->type, cont_id);
709 break;
710 case BTF_KIND_ARRAY:
711 btf_dump_emit_type(d, btf_array(t)->type, cont_id);
712 break;
713 case BTF_KIND_FWD:
714 btf_dump_emit_fwd_def(d, id, t);
715 btf_dump_printf(d, ";\n\n");
716 tstate->emit_state = EMITTED;
717 break;
718 case BTF_KIND_TYPEDEF:
719 tstate->emit_state = EMITTING;
720 btf_dump_emit_type(d, t->type, id);
721 /*
722 * typedef can server as both definition and forward
723 * declaration; at this stage someone depends on
724 * typedef as a forward declaration (refers to it
725 * through pointer), so unless we already did it,
726 * emit typedef as a forward declaration
727 */
728 if (!tstate->fwd_emitted && !btf_dump_is_blacklisted(d, id)) {
729 btf_dump_emit_typedef_def(d, id, t, 0);
730 btf_dump_printf(d, ";\n\n");
731 }
732 tstate->emit_state = EMITTED;
733 break;
734 case BTF_KIND_STRUCT:
735 case BTF_KIND_UNION:
736 tstate->emit_state = EMITTING;
737 /* if it's a top-level struct/union definition or struct/union
738 * is anonymous, then in C we'll be emitting all fields and
739 * their types (as opposed to just `struct X`), so we need to
740 * make sure that all types, referenced from struct/union
741 * members have necessary forward-declarations, where
742 * applicable
743 */
744 if (top_level_def || t->name_off == 0) {
745 const struct btf_member *m = btf_members(t);
746 __u16 vlen = btf_vlen(t);
747 int i, new_cont_id;
748
749 new_cont_id = t->name_off == 0 ? cont_id : id;
750 for (i = 0; i < vlen; i++, m++)
751 btf_dump_emit_type(d, m->type, new_cont_id);
752 } else if (!tstate->fwd_emitted && id != cont_id) {
753 btf_dump_emit_struct_fwd(d, id, t);
754 btf_dump_printf(d, ";\n\n");
755 tstate->fwd_emitted = 1;
756 }
757
758 if (top_level_def) {
759 btf_dump_emit_struct_def(d, id, t, 0);
760 btf_dump_printf(d, ";\n\n");
761 tstate->emit_state = EMITTED;
762 } else {
763 tstate->emit_state = NOT_EMITTED;
764 }
765 break;
766 case BTF_KIND_FUNC_PROTO: {
767 const struct btf_param *p = btf_params(t);
768 __u16 vlen = btf_vlen(t);
769 int i;
770
771 btf_dump_emit_type(d, t->type, cont_id);
772 for (i = 0; i < vlen; i++, p++)
773 btf_dump_emit_type(d, p->type, cont_id);
774
775 break;
776 }
777 default:
778 break;
779 }
780}
781
782static bool btf_is_struct_packed(const struct btf *btf, __u32 id,
783 const struct btf_type *t)
784{
785 const struct btf_member *m;
786 int align, i, bit_sz;
787 __u16 vlen;
788
789 align = btf__align_of(btf, id);
790 /* size of a non-packed struct has to be a multiple of its alignment*/
791 if (align && t->size % align)
792 return true;
793
794 m = btf_members(t);
795 vlen = btf_vlen(t);
796 /* all non-bitfield fields have to be naturally aligned */
797 for (i = 0; i < vlen; i++, m++) {
798 align = btf__align_of(btf, m->type);
799 bit_sz = btf_member_bitfield_size(t, i);
800 if (align && bit_sz == 0 && m->offset % (8 * align) != 0)
801 return true;
802 }
803
804 /*
805 * if original struct was marked as packed, but its layout is
806 * naturally aligned, we'll detect that it's not packed
807 */
808 return false;
809}
810
811static int chip_away_bits(int total, int at_most)
812{
813 return total % at_most ? : at_most;
814}
815
816static void btf_dump_emit_bit_padding(const struct btf_dump *d,
817 int cur_off, int m_off, int m_bit_sz,
818 int align, int lvl)
819{
820 int off_diff = m_off - cur_off;
821 int ptr_bits = d->ptr_sz * 8;
822
823 if (off_diff <= 0)
824 /* no gap */
825 return;
826 if (m_bit_sz == 0 && off_diff < align * 8)
827 /* natural padding will take care of a gap */
828 return;
829
830 while (off_diff > 0) {
831 const char *pad_type;
832 int pad_bits;
833
834 if (ptr_bits > 32 && off_diff > 32) {
835 pad_type = "long";
836 pad_bits = chip_away_bits(off_diff, ptr_bits);
837 } else if (off_diff > 16) {
838 pad_type = "int";
839 pad_bits = chip_away_bits(off_diff, 32);
840 } else if (off_diff > 8) {
841 pad_type = "short";
842 pad_bits = chip_away_bits(off_diff, 16);
843 } else {
844 pad_type = "char";
845 pad_bits = chip_away_bits(off_diff, 8);
846 }
847 btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, pad_bits);
848 off_diff -= pad_bits;
849 }
850}
851
852static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
853 const struct btf_type *t)
854{
855 btf_dump_printf(d, "%s %s",
856 btf_is_struct(t) ? "struct" : "union",
857 btf_dump_type_name(d, id));
858}
859
860static void btf_dump_emit_struct_def(struct btf_dump *d,
861 __u32 id,
862 const struct btf_type *t,
863 int lvl)
864{
865 const struct btf_member *m = btf_members(t);
866 bool is_struct = btf_is_struct(t);
867 int align, i, packed, off = 0;
868 __u16 vlen = btf_vlen(t);
869
870 packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0;
871
872 btf_dump_printf(d, "%s%s%s {",
873 is_struct ? "struct" : "union",
874 t->name_off ? " " : "",
875 btf_dump_type_name(d, id));
876
877 for (i = 0; i < vlen; i++, m++) {
878 const char *fname;
879 int m_off, m_sz;
880
881 fname = btf_name_of(d, m->name_off);
882 m_sz = btf_member_bitfield_size(t, i);
883 m_off = btf_member_bit_offset(t, i);
884 align = packed ? 1 : btf__align_of(d->btf, m->type);
885
886 btf_dump_emit_bit_padding(d, off, m_off, m_sz, align, lvl + 1);
887 btf_dump_printf(d, "\n%s", pfx(lvl + 1));
888 btf_dump_emit_type_decl(d, m->type, fname, lvl + 1);
889
890 if (m_sz) {
891 btf_dump_printf(d, ": %d", m_sz);
892 off = m_off + m_sz;
893 } else {
894 m_sz = max((__s64)0, btf__resolve_size(d->btf, m->type));
895 off = m_off + m_sz * 8;
896 }
897 btf_dump_printf(d, ";");
898 }
899
900 /* pad at the end, if necessary */
901 if (is_struct) {
902 align = packed ? 1 : btf__align_of(d->btf, id);
903 btf_dump_emit_bit_padding(d, off, t->size * 8, 0, align,
904 lvl + 1);
905 }
906
907 if (vlen)
908 btf_dump_printf(d, "\n");
909 btf_dump_printf(d, "%s}", pfx(lvl));
910 if (packed)
911 btf_dump_printf(d, " __attribute__((packed))");
912}
913
914static const char *missing_base_types[][2] = {
915 /*
916 * GCC emits typedefs to its internal __PolyX_t types when compiling Arm
917 * SIMD intrinsics. Alias them to standard base types.
918 */
919 { "__Poly8_t", "unsigned char" },
920 { "__Poly16_t", "unsigned short" },
921 { "__Poly64_t", "unsigned long long" },
922 { "__Poly128_t", "unsigned __int128" },
923};
924
925static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
926 const struct btf_type *t)
927{
928 const char *name = btf_dump_type_name(d, id);
929 int i;
930
931 for (i = 0; i < ARRAY_SIZE(missing_base_types); i++) {
932 if (strcmp(name, missing_base_types[i][0]) == 0) {
933 btf_dump_printf(d, "typedef %s %s;\n\n",
934 missing_base_types[i][1], name);
935 break;
936 }
937 }
938}
939
940static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
941 const struct btf_type *t)
942{
943 btf_dump_printf(d, "enum %s", btf_dump_type_name(d, id));
944}
945
946static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
947 const struct btf_type *t,
948 int lvl)
949{
950 const struct btf_enum *v = btf_enum(t);
951 __u16 vlen = btf_vlen(t);
952 const char *name;
953 size_t dup_cnt;
954 int i;
955
956 btf_dump_printf(d, "enum%s%s",
957 t->name_off ? " " : "",
958 btf_dump_type_name(d, id));
959
960 if (vlen) {
961 btf_dump_printf(d, " {");
962 for (i = 0; i < vlen; i++, v++) {
963 name = btf_name_of(d, v->name_off);
964 /* enumerators share namespace with typedef idents */
965 dup_cnt = btf_dump_name_dups(d, d->ident_names, name);
966 if (dup_cnt > 1) {
967 btf_dump_printf(d, "\n%s%s___%zu = %u,",
968 pfx(lvl + 1), name, dup_cnt,
969 (__u32)v->val);
970 } else {
971 btf_dump_printf(d, "\n%s%s = %u,",
972 pfx(lvl + 1), name,
973 (__u32)v->val);
974 }
975 }
976 btf_dump_printf(d, "\n%s}", pfx(lvl));
977 }
978}
979
980static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
981 const struct btf_type *t)
982{
983 const char *name = btf_dump_type_name(d, id);
984
985 if (btf_kflag(t))
986 btf_dump_printf(d, "union %s", name);
987 else
988 btf_dump_printf(d, "struct %s", name);
989}
990
991static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
992 const struct btf_type *t, int lvl)
993{
994 const char *name = btf_dump_ident_name(d, id);
995
996 /*
997 * Old GCC versions are emitting invalid typedef for __gnuc_va_list
998 * pointing to VOID. This generates warnings from btf_dump() and
999 * results in uncompilable header file, so we are fixing it up here
1000 * with valid typedef into __builtin_va_list.
1001 */
1002 if (t->type == 0 && strcmp(name, "__gnuc_va_list") == 0) {
1003 btf_dump_printf(d, "typedef __builtin_va_list __gnuc_va_list");
1004 return;
1005 }
1006
1007 btf_dump_printf(d, "typedef ");
1008 btf_dump_emit_type_decl(d, t->type, name, lvl);
1009}
1010
1011static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id)
1012{
1013 __u32 *new_stack;
1014 size_t new_cap;
1015
1016 if (d->decl_stack_cnt >= d->decl_stack_cap) {
1017 new_cap = max(16, d->decl_stack_cap * 3 / 2);
1018 new_stack = libbpf_reallocarray(d->decl_stack, new_cap, sizeof(new_stack[0]));
1019 if (!new_stack)
1020 return -ENOMEM;
1021 d->decl_stack = new_stack;
1022 d->decl_stack_cap = new_cap;
1023 }
1024
1025 d->decl_stack[d->decl_stack_cnt++] = id;
1026
1027 return 0;
1028}
1029
1030/*
1031 * Emit type declaration (e.g., field type declaration in a struct or argument
1032 * declaration in function prototype) in correct C syntax.
1033 *
1034 * For most types it's trivial, but there are few quirky type declaration
1035 * cases worth mentioning:
1036 * - function prototypes (especially nesting of function prototypes);
1037 * - arrays;
1038 * - const/volatile/restrict for pointers vs other types.
1039 *
1040 * For a good discussion of *PARSING* C syntax (as a human), see
1041 * Peter van der Linden's "Expert C Programming: Deep C Secrets",
1042 * Ch.3 "Unscrambling Declarations in C".
1043 *
1044 * It won't help with BTF to C conversion much, though, as it's an opposite
1045 * problem. So we came up with this algorithm in reverse to van der Linden's
1046 * parsing algorithm. It goes from structured BTF representation of type
1047 * declaration to a valid compilable C syntax.
1048 *
1049 * For instance, consider this C typedef:
1050 * typedef const int * const * arr[10] arr_t;
1051 * It will be represented in BTF with this chain of BTF types:
1052 * [typedef] -> [array] -> [ptr] -> [const] -> [ptr] -> [const] -> [int]
1053 *
1054 * Notice how [const] modifier always goes before type it modifies in BTF type
1055 * graph, but in C syntax, const/volatile/restrict modifiers are written to
1056 * the right of pointers, but to the left of other types. There are also other
1057 * quirks, like function pointers, arrays of them, functions returning other
1058 * functions, etc.
1059 *
1060 * We handle that by pushing all the types to a stack, until we hit "terminal"
1061 * type (int/enum/struct/union/fwd). Then depending on the kind of a type on
1062 * top of a stack, modifiers are handled differently. Array/function pointers
1063 * have also wildly different syntax and how nesting of them are done. See
1064 * code for authoritative definition.
1065 *
1066 * To avoid allocating new stack for each independent chain of BTF types, we
1067 * share one bigger stack, with each chain working only on its own local view
1068 * of a stack frame. Some care is required to "pop" stack frames after
1069 * processing type declaration chain.
1070 */
1071int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
1072 const struct btf_dump_emit_type_decl_opts *opts)
1073{
1074 const char *fname;
1075 int lvl, err;
1076
1077 if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts))
1078 return libbpf_err(-EINVAL);
1079
1080 err = btf_dump_resize(d);
1081 if (err)
1082 return libbpf_err(err);
1083
1084 fname = OPTS_GET(opts, field_name, "");
1085 lvl = OPTS_GET(opts, indent_level, 0);
1086 d->strip_mods = OPTS_GET(opts, strip_mods, false);
1087 btf_dump_emit_type_decl(d, id, fname, lvl);
1088 d->strip_mods = false;
1089 return 0;
1090}
1091
1092static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
1093 const char *fname, int lvl)
1094{
1095 struct id_stack decl_stack;
1096 const struct btf_type *t;
1097 int err, stack_start;
1098
1099 stack_start = d->decl_stack_cnt;
1100 for (;;) {
1101 t = btf__type_by_id(d->btf, id);
1102 if (d->strip_mods && btf_is_mod(t))
1103 goto skip_mod;
1104
1105 err = btf_dump_push_decl_stack_id(d, id);
1106 if (err < 0) {
1107 /*
1108 * if we don't have enough memory for entire type decl
1109 * chain, restore stack, emit warning, and try to
1110 * proceed nevertheless
1111 */
1112 pr_warn("not enough memory for decl stack:%d", err);
1113 d->decl_stack_cnt = stack_start;
1114 return;
1115 }
1116skip_mod:
1117 /* VOID */
1118 if (id == 0)
1119 break;
1120
1121 switch (btf_kind(t)) {
1122 case BTF_KIND_PTR:
1123 case BTF_KIND_VOLATILE:
1124 case BTF_KIND_CONST:
1125 case BTF_KIND_RESTRICT:
1126 case BTF_KIND_FUNC_PROTO:
1127 id = t->type;
1128 break;
1129 case BTF_KIND_ARRAY:
1130 id = btf_array(t)->type;
1131 break;
1132 case BTF_KIND_INT:
1133 case BTF_KIND_ENUM:
1134 case BTF_KIND_FWD:
1135 case BTF_KIND_STRUCT:
1136 case BTF_KIND_UNION:
1137 case BTF_KIND_TYPEDEF:
1138 case BTF_KIND_FLOAT:
1139 goto done;
1140 default:
1141 pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
1142 btf_kind(t), id);
1143 goto done;
1144 }
1145 }
1146done:
1147 /*
1148 * We might be inside a chain of declarations (e.g., array of function
1149 * pointers returning anonymous (so inlined) structs, having another
1150 * array field). Each of those needs its own "stack frame" to handle
1151 * emitting of declarations. Those stack frames are non-overlapping
1152 * portions of shared btf_dump->decl_stack. To make it a bit nicer to
1153 * handle this set of nested stacks, we create a view corresponding to
1154 * our own "stack frame" and work with it as an independent stack.
1155 * We'll need to clean up after emit_type_chain() returns, though.
1156 */
1157 decl_stack.ids = d->decl_stack + stack_start;
1158 decl_stack.cnt = d->decl_stack_cnt - stack_start;
1159 btf_dump_emit_type_chain(d, &decl_stack, fname, lvl);
1160 /*
1161 * emit_type_chain() guarantees that it will pop its entire decl_stack
1162 * frame before returning. But it works with a read-only view into
1163 * decl_stack, so it doesn't actually pop anything from the
1164 * perspective of shared btf_dump->decl_stack, per se. We need to
1165 * reset decl_stack state to how it was before us to avoid it growing
1166 * all the time.
1167 */
1168 d->decl_stack_cnt = stack_start;
1169}
1170
1171static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack)
1172{
1173 const struct btf_type *t;
1174 __u32 id;
1175
1176 while (decl_stack->cnt) {
1177 id = decl_stack->ids[decl_stack->cnt - 1];
1178 t = btf__type_by_id(d->btf, id);
1179
1180 switch (btf_kind(t)) {
1181 case BTF_KIND_VOLATILE:
1182 btf_dump_printf(d, "volatile ");
1183 break;
1184 case BTF_KIND_CONST:
1185 btf_dump_printf(d, "const ");
1186 break;
1187 case BTF_KIND_RESTRICT:
1188 btf_dump_printf(d, "restrict ");
1189 break;
1190 default:
1191 return;
1192 }
1193 decl_stack->cnt--;
1194 }
1195}
1196
1197static void btf_dump_drop_mods(struct btf_dump *d, struct id_stack *decl_stack)
1198{
1199 const struct btf_type *t;
1200 __u32 id;
1201
1202 while (decl_stack->cnt) {
1203 id = decl_stack->ids[decl_stack->cnt - 1];
1204 t = btf__type_by_id(d->btf, id);
1205 if (!btf_is_mod(t))
1206 return;
1207 decl_stack->cnt--;
1208 }
1209}
1210
1211static void btf_dump_emit_name(const struct btf_dump *d,
1212 const char *name, bool last_was_ptr)
1213{
1214 bool separate = name[0] && !last_was_ptr;
1215
1216 btf_dump_printf(d, "%s%s", separate ? " " : "", name);
1217}
1218
1219static void btf_dump_emit_type_chain(struct btf_dump *d,
1220 struct id_stack *decls,
1221 const char *fname, int lvl)
1222{
1223 /*
1224 * last_was_ptr is used to determine if we need to separate pointer
1225 * asterisk (*) from previous part of type signature with space, so
1226 * that we get `int ***`, instead of `int * * *`. We default to true
1227 * for cases where we have single pointer in a chain. E.g., in ptr ->
1228 * func_proto case. func_proto will start a new emit_type_chain call
1229 * with just ptr, which should be emitted as (*) or (*<fname>), so we
1230 * don't want to prepend space for that last pointer.
1231 */
1232 bool last_was_ptr = true;
1233 const struct btf_type *t;
1234 const char *name;
1235 __u16 kind;
1236 __u32 id;
1237
1238 while (decls->cnt) {
1239 id = decls->ids[--decls->cnt];
1240 if (id == 0) {
1241 /* VOID is a special snowflake */
1242 btf_dump_emit_mods(d, decls);
1243 btf_dump_printf(d, "void");
1244 last_was_ptr = false;
1245 continue;
1246 }
1247
1248 t = btf__type_by_id(d->btf, id);
1249 kind = btf_kind(t);
1250
1251 switch (kind) {
1252 case BTF_KIND_INT:
1253 case BTF_KIND_FLOAT:
1254 btf_dump_emit_mods(d, decls);
1255 name = btf_name_of(d, t->name_off);
1256 btf_dump_printf(d, "%s", name);
1257 break;
1258 case BTF_KIND_STRUCT:
1259 case BTF_KIND_UNION:
1260 btf_dump_emit_mods(d, decls);
1261 /* inline anonymous struct/union */
1262 if (t->name_off == 0)
1263 btf_dump_emit_struct_def(d, id, t, lvl);
1264 else
1265 btf_dump_emit_struct_fwd(d, id, t);
1266 break;
1267 case BTF_KIND_ENUM:
1268 btf_dump_emit_mods(d, decls);
1269 /* inline anonymous enum */
1270 if (t->name_off == 0)
1271 btf_dump_emit_enum_def(d, id, t, lvl);
1272 else
1273 btf_dump_emit_enum_fwd(d, id, t);
1274 break;
1275 case BTF_KIND_FWD:
1276 btf_dump_emit_mods(d, decls);
1277 btf_dump_emit_fwd_def(d, id, t);
1278 break;
1279 case BTF_KIND_TYPEDEF:
1280 btf_dump_emit_mods(d, decls);
1281 btf_dump_printf(d, "%s", btf_dump_ident_name(d, id));
1282 break;
1283 case BTF_KIND_PTR:
1284 btf_dump_printf(d, "%s", last_was_ptr ? "*" : " *");
1285 break;
1286 case BTF_KIND_VOLATILE:
1287 btf_dump_printf(d, " volatile");
1288 break;
1289 case BTF_KIND_CONST:
1290 btf_dump_printf(d, " const");
1291 break;
1292 case BTF_KIND_RESTRICT:
1293 btf_dump_printf(d, " restrict");
1294 break;
1295 case BTF_KIND_ARRAY: {
1296 const struct btf_array *a = btf_array(t);
1297 const struct btf_type *next_t;
1298 __u32 next_id;
1299 bool multidim;
1300 /*
1301 * GCC has a bug
1302 * (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8354)
1303 * which causes it to emit extra const/volatile
1304 * modifiers for an array, if array's element type has
1305 * const/volatile modifiers. Clang doesn't do that.
1306 * In general, it doesn't seem very meaningful to have
1307 * a const/volatile modifier for array, so we are
1308 * going to silently skip them here.
1309 */
1310 btf_dump_drop_mods(d, decls);
1311
1312 if (decls->cnt == 0) {
1313 btf_dump_emit_name(d, fname, last_was_ptr);
1314 btf_dump_printf(d, "[%u]", a->nelems);
1315 return;
1316 }
1317
1318 next_id = decls->ids[decls->cnt - 1];
1319 next_t = btf__type_by_id(d->btf, next_id);
1320 multidim = btf_is_array(next_t);
1321 /* we need space if we have named non-pointer */
1322 if (fname[0] && !last_was_ptr)
1323 btf_dump_printf(d, " ");
1324 /* no parentheses for multi-dimensional array */
1325 if (!multidim)
1326 btf_dump_printf(d, "(");
1327 btf_dump_emit_type_chain(d, decls, fname, lvl);
1328 if (!multidim)
1329 btf_dump_printf(d, ")");
1330 btf_dump_printf(d, "[%u]", a->nelems);
1331 return;
1332 }
1333 case BTF_KIND_FUNC_PROTO: {
1334 const struct btf_param *p = btf_params(t);
1335 __u16 vlen = btf_vlen(t);
1336 int i;
1337
1338 /*
1339 * GCC emits extra volatile qualifier for
1340 * __attribute__((noreturn)) function pointers. Clang
1341 * doesn't do it. It's a GCC quirk for backwards
1342 * compatibility with code written for GCC <2.5. So,
1343 * similarly to extra qualifiers for array, just drop
1344 * them, instead of handling them.
1345 */
1346 btf_dump_drop_mods(d, decls);
1347 if (decls->cnt) {
1348 btf_dump_printf(d, " (");
1349 btf_dump_emit_type_chain(d, decls, fname, lvl);
1350 btf_dump_printf(d, ")");
1351 } else {
1352 btf_dump_emit_name(d, fname, last_was_ptr);
1353 }
1354 btf_dump_printf(d, "(");
1355 /*
1356 * Clang for BPF target generates func_proto with no
1357 * args as a func_proto with a single void arg (e.g.,
1358 * `int (*f)(void)` vs just `int (*f)()`). We are
1359 * going to pretend there are no args for such case.
1360 */
1361 if (vlen == 1 && p->type == 0) {
1362 btf_dump_printf(d, ")");
1363 return;
1364 }
1365
1366 for (i = 0; i < vlen; i++, p++) {
1367 if (i > 0)
1368 btf_dump_printf(d, ", ");
1369
1370 /* last arg of type void is vararg */
1371 if (i == vlen - 1 && p->type == 0) {
1372 btf_dump_printf(d, "...");
1373 break;
1374 }
1375
1376 name = btf_name_of(d, p->name_off);
1377 btf_dump_emit_type_decl(d, p->type, name, lvl);
1378 }
1379
1380 btf_dump_printf(d, ")");
1381 return;
1382 }
1383 default:
1384 pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
1385 kind, id);
1386 return;
1387 }
1388
1389 last_was_ptr = kind == BTF_KIND_PTR;
1390 }
1391
1392 btf_dump_emit_name(d, fname, last_was_ptr);
1393}
1394
1395/* return number of duplicates (occurrences) of a given name */
1396static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
1397 const char *orig_name)
1398{
1399 size_t dup_cnt = 0;
1400
1401 hashmap__find(name_map, orig_name, (void **)&dup_cnt);
1402 dup_cnt++;
1403 hashmap__set(name_map, orig_name, (void *)dup_cnt, NULL, NULL);
1404
1405 return dup_cnt;
1406}
1407
1408static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id,
1409 struct hashmap *name_map)
1410{
1411 struct btf_dump_type_aux_state *s = &d->type_states[id];
1412 const struct btf_type *t = btf__type_by_id(d->btf, id);
1413 const char *orig_name = btf_name_of(d, t->name_off);
1414 const char **cached_name = &d->cached_names[id];
1415 size_t dup_cnt;
1416
1417 if (t->name_off == 0)
1418 return "";
1419
1420 if (s->name_resolved)
1421 return *cached_name ? *cached_name : orig_name;
1422
1423 dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
1424 if (dup_cnt > 1) {
1425 const size_t max_len = 256;
1426 char new_name[max_len];
1427
1428 snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt);
1429 *cached_name = strdup(new_name);
1430 }
1431
1432 s->name_resolved = 1;
1433 return *cached_name ? *cached_name : orig_name;
1434}
1435
1436static const char *btf_dump_type_name(struct btf_dump *d, __u32 id)
1437{
1438 return btf_dump_resolve_name(d, id, d->type_names);
1439}
1440
1441static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id)
1442{
1443 return btf_dump_resolve_name(d, id, d->ident_names);
1444}
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/* make sure libbpf doesn't use kernel-only integer typedefs */
23#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
24
25static const char PREFIXES[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t";
26static const size_t PREFIX_CNT = sizeof(PREFIXES) - 1;
27
28static const char *pfx(int lvl)
29{
30 return lvl >= PREFIX_CNT ? PREFIXES : &PREFIXES[PREFIX_CNT - lvl];
31}
32
33enum btf_dump_type_order_state {
34 NOT_ORDERED,
35 ORDERING,
36 ORDERED,
37};
38
39enum btf_dump_type_emit_state {
40 NOT_EMITTED,
41 EMITTING,
42 EMITTED,
43};
44
45/* per-type auxiliary state */
46struct btf_dump_type_aux_state {
47 /* topological sorting state */
48 enum btf_dump_type_order_state order_state: 2;
49 /* emitting state used to determine the need for forward declaration */
50 enum btf_dump_type_emit_state emit_state: 2;
51 /* whether forward declaration was already emitted */
52 __u8 fwd_emitted: 1;
53 /* whether unique non-duplicate name was already assigned */
54 __u8 name_resolved: 1;
55 /* whether type is referenced from any other type */
56 __u8 referenced: 1;
57};
58
59struct btf_dump {
60 const struct btf *btf;
61 const struct btf_ext *btf_ext;
62 btf_dump_printf_fn_t printf_fn;
63 struct btf_dump_opts opts;
64 int ptr_sz;
65 bool strip_mods;
66
67 /* per-type auxiliary state */
68 struct btf_dump_type_aux_state *type_states;
69 /* per-type optional cached unique name, must be freed, if present */
70 const char **cached_names;
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
94static size_t str_hash_fn(const void *key, void *ctx)
95{
96 const char *s = key;
97 size_t h = 0;
98
99 while (*s) {
100 h = h * 31 + *s;
101 s++;
102 }
103 return h;
104}
105
106static bool str_equal_fn(const void *a, const void *b, void *ctx)
107{
108 return strcmp(a, b) == 0;
109}
110
111static const char *btf_name_of(const struct btf_dump *d, __u32 name_off)
112{
113 return btf__name_by_offset(d->btf, name_off);
114}
115
116static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...)
117{
118 va_list args;
119
120 va_start(args, fmt);
121 d->printf_fn(d->opts.ctx, fmt, args);
122 va_end(args);
123}
124
125static int btf_dump_mark_referenced(struct btf_dump *d);
126
127struct btf_dump *btf_dump__new(const struct btf *btf,
128 const struct btf_ext *btf_ext,
129 const struct btf_dump_opts *opts,
130 btf_dump_printf_fn_t printf_fn)
131{
132 struct btf_dump *d;
133 int err;
134
135 d = calloc(1, sizeof(struct btf_dump));
136 if (!d)
137 return ERR_PTR(-ENOMEM);
138
139 d->btf = btf;
140 d->btf_ext = btf_ext;
141 d->printf_fn = printf_fn;
142 d->opts.ctx = opts ? opts->ctx : NULL;
143 d->ptr_sz = btf__pointer_size(btf) ? : sizeof(void *);
144
145 d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
146 if (IS_ERR(d->type_names)) {
147 err = PTR_ERR(d->type_names);
148 d->type_names = NULL;
149 goto err;
150 }
151 d->ident_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
152 if (IS_ERR(d->ident_names)) {
153 err = PTR_ERR(d->ident_names);
154 d->ident_names = NULL;
155 goto err;
156 }
157 d->type_states = calloc(1 + btf__get_nr_types(d->btf),
158 sizeof(d->type_states[0]));
159 if (!d->type_states) {
160 err = -ENOMEM;
161 goto err;
162 }
163 d->cached_names = calloc(1 + btf__get_nr_types(d->btf),
164 sizeof(d->cached_names[0]));
165 if (!d->cached_names) {
166 err = -ENOMEM;
167 goto err;
168 }
169
170 /* VOID is special */
171 d->type_states[0].order_state = ORDERED;
172 d->type_states[0].emit_state = EMITTED;
173
174 /* eagerly determine referenced types for anon enums */
175 err = btf_dump_mark_referenced(d);
176 if (err)
177 goto err;
178
179 return d;
180err:
181 btf_dump__free(d);
182 return ERR_PTR(err);
183}
184
185void btf_dump__free(struct btf_dump *d)
186{
187 int i, cnt;
188
189 if (IS_ERR_OR_NULL(d))
190 return;
191
192 free(d->type_states);
193 if (d->cached_names) {
194 /* any set cached name is owned by us and should be freed */
195 for (i = 0, cnt = btf__get_nr_types(d->btf); i <= cnt; i++) {
196 if (d->cached_names[i])
197 free((void *)d->cached_names[i]);
198 }
199 }
200 free(d->cached_names);
201 free(d->emit_queue);
202 free(d->decl_stack);
203 hashmap__free(d->type_names);
204 hashmap__free(d->ident_names);
205
206 free(d);
207}
208
209static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr);
210static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id);
211
212/*
213 * Dump BTF type in a compilable C syntax, including all the necessary
214 * dependent types, necessary for compilation. If some of the dependent types
215 * were already emitted as part of previous btf_dump__dump_type() invocation
216 * for another type, they won't be emitted again. This API allows callers to
217 * filter out BTF types according to user-defined criterias and emitted only
218 * minimal subset of types, necessary to compile everything. Full struct/union
219 * definitions will still be emitted, even if the only usage is through
220 * pointer and could be satisfied with just a forward declaration.
221 *
222 * Dumping is done in two high-level passes:
223 * 1. Topologically sort type definitions to satisfy C rules of compilation.
224 * 2. Emit type definitions in C syntax.
225 *
226 * Returns 0 on success; <0, otherwise.
227 */
228int btf_dump__dump_type(struct btf_dump *d, __u32 id)
229{
230 int err, i;
231
232 if (id > btf__get_nr_types(d->btf))
233 return -EINVAL;
234
235 d->emit_queue_cnt = 0;
236 err = btf_dump_order_type(d, id, false);
237 if (err < 0)
238 return err;
239
240 for (i = 0; i < d->emit_queue_cnt; i++)
241 btf_dump_emit_type(d, d->emit_queue[i], 0 /*top-level*/);
242
243 return 0;
244}
245
246/*
247 * Mark all types that are referenced from any other type. This is used to
248 * determine top-level anonymous enums that need to be emitted as an
249 * independent type declarations.
250 * Anonymous enums come in two flavors: either embedded in a struct's field
251 * definition, in which case they have to be declared inline as part of field
252 * type declaration; or as a top-level anonymous enum, typically used for
253 * declaring global constants. It's impossible to distinguish between two
254 * without knowning whether given enum type was referenced from other type:
255 * top-level anonymous enum won't be referenced by anything, while embedded
256 * one will.
257 */
258static int btf_dump_mark_referenced(struct btf_dump *d)
259{
260 int i, j, n = btf__get_nr_types(d->btf);
261 const struct btf_type *t;
262 __u16 vlen;
263
264 for (i = 1; i <= n; i++) {
265 t = btf__type_by_id(d->btf, i);
266 vlen = btf_vlen(t);
267
268 switch (btf_kind(t)) {
269 case BTF_KIND_INT:
270 case BTF_KIND_ENUM:
271 case BTF_KIND_FWD:
272 break;
273
274 case BTF_KIND_VOLATILE:
275 case BTF_KIND_CONST:
276 case BTF_KIND_RESTRICT:
277 case BTF_KIND_PTR:
278 case BTF_KIND_TYPEDEF:
279 case BTF_KIND_FUNC:
280 case BTF_KIND_VAR:
281 d->type_states[t->type].referenced = 1;
282 break;
283
284 case BTF_KIND_ARRAY: {
285 const struct btf_array *a = btf_array(t);
286
287 d->type_states[a->index_type].referenced = 1;
288 d->type_states[a->type].referenced = 1;
289 break;
290 }
291 case BTF_KIND_STRUCT:
292 case BTF_KIND_UNION: {
293 const struct btf_member *m = btf_members(t);
294
295 for (j = 0; j < vlen; j++, m++)
296 d->type_states[m->type].referenced = 1;
297 break;
298 }
299 case BTF_KIND_FUNC_PROTO: {
300 const struct btf_param *p = btf_params(t);
301
302 for (j = 0; j < vlen; j++, p++)
303 d->type_states[p->type].referenced = 1;
304 break;
305 }
306 case BTF_KIND_DATASEC: {
307 const struct btf_var_secinfo *v = btf_var_secinfos(t);
308
309 for (j = 0; j < vlen; j++, v++)
310 d->type_states[v->type].referenced = 1;
311 break;
312 }
313 default:
314 return -EINVAL;
315 }
316 }
317 return 0;
318}
319static int btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id)
320{
321 __u32 *new_queue;
322 size_t new_cap;
323
324 if (d->emit_queue_cnt >= d->emit_queue_cap) {
325 new_cap = max(16, d->emit_queue_cap * 3 / 2);
326 new_queue = realloc(d->emit_queue,
327 new_cap * sizeof(new_queue[0]));
328 if (!new_queue)
329 return -ENOMEM;
330 d->emit_queue = new_queue;
331 d->emit_queue_cap = new_cap;
332 }
333
334 d->emit_queue[d->emit_queue_cnt++] = id;
335 return 0;
336}
337
338/*
339 * Determine order of emitting dependent types and specified type to satisfy
340 * C compilation rules. This is done through topological sorting with an
341 * additional complication which comes from C rules. The main idea for C is
342 * that if some type is "embedded" into a struct/union, it's size needs to be
343 * known at the time of definition of containing type. E.g., for:
344 *
345 * struct A {};
346 * struct B { struct A x; }
347 *
348 * struct A *HAS* to be defined before struct B, because it's "embedded",
349 * i.e., it is part of struct B layout. But in the following case:
350 *
351 * struct A;
352 * struct B { struct A *x; }
353 * struct A {};
354 *
355 * it's enough to just have a forward declaration of struct A at the time of
356 * struct B definition, as struct B has a pointer to struct A, so the size of
357 * field x is known without knowing struct A size: it's sizeof(void *).
358 *
359 * Unfortunately, there are some trickier cases we need to handle, e.g.:
360 *
361 * struct A {}; // if this was forward-declaration: compilation error
362 * struct B {
363 * struct { // anonymous struct
364 * struct A y;
365 * } *x;
366 * };
367 *
368 * In this case, struct B's field x is a pointer, so it's size is known
369 * regardless of the size of (anonymous) struct it points to. But because this
370 * struct is anonymous and thus defined inline inside struct B, *and* it
371 * embeds struct A, compiler requires full definition of struct A to be known
372 * before struct B can be defined. This creates a transitive dependency
373 * between struct A and struct B. If struct A was forward-declared before
374 * struct B definition and fully defined after struct B definition, that would
375 * trigger compilation error.
376 *
377 * All this means that while we are doing topological sorting on BTF type
378 * graph, we need to determine relationships between different types (graph
379 * nodes):
380 * - weak link (relationship) between X and Y, if Y *CAN* be
381 * forward-declared at the point of X definition;
382 * - strong link, if Y *HAS* to be fully-defined before X can be defined.
383 *
384 * The rule is as follows. Given a chain of BTF types from X to Y, if there is
385 * BTF_KIND_PTR type in the chain and at least one non-anonymous type
386 * Z (excluding X, including Y), then link is weak. Otherwise, it's strong.
387 * Weak/strong relationship is determined recursively during DFS traversal and
388 * is returned as a result from btf_dump_order_type().
389 *
390 * btf_dump_order_type() is trying to avoid unnecessary forward declarations,
391 * but it is not guaranteeing that no extraneous forward declarations will be
392 * emitted.
393 *
394 * To avoid extra work, algorithm marks some of BTF types as ORDERED, when
395 * it's done with them, but not for all (e.g., VOLATILE, CONST, RESTRICT,
396 * ARRAY, FUNC_PROTO), as weak/strong semantics for those depends on the
397 * entire graph path, so depending where from one came to that BTF type, it
398 * might cause weak or strong ordering. For types like STRUCT/UNION/INT/ENUM,
399 * once they are processed, there is no need to do it again, so they are
400 * marked as ORDERED. We can mark PTR as ORDERED as well, as it semi-forces
401 * weak link, unless subsequent referenced STRUCT/UNION/ENUM is anonymous. But
402 * in any case, once those are processed, no need to do it again, as the
403 * result won't change.
404 *
405 * Returns:
406 * - 1, if type is part of strong link (so there is strong topological
407 * ordering requirements);
408 * - 0, if type is part of weak link (so can be satisfied through forward
409 * declaration);
410 * - <0, on error (e.g., unsatisfiable type loop detected).
411 */
412static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
413{
414 /*
415 * Order state is used to detect strong link cycles, but only for BTF
416 * kinds that are or could be an independent definition (i.e.,
417 * stand-alone fwd decl, enum, typedef, struct, union). Ptrs, arrays,
418 * func_protos, modifiers are just means to get to these definitions.
419 * Int/void don't need definitions, they are assumed to be always
420 * properly defined. We also ignore datasec, var, and funcs for now.
421 * So for all non-defining kinds, we never even set ordering state,
422 * for defining kinds we set ORDERING and subsequently ORDERED if it
423 * forms a strong link.
424 */
425 struct btf_dump_type_aux_state *tstate = &d->type_states[id];
426 const struct btf_type *t;
427 __u16 vlen;
428 int err, i;
429
430 /* return true, letting typedefs know that it's ok to be emitted */
431 if (tstate->order_state == ORDERED)
432 return 1;
433
434 t = btf__type_by_id(d->btf, id);
435
436 if (tstate->order_state == ORDERING) {
437 /* type loop, but resolvable through fwd declaration */
438 if (btf_is_composite(t) && through_ptr && t->name_off != 0)
439 return 0;
440 pr_warn("unsatisfiable type cycle, id:[%u]\n", id);
441 return -ELOOP;
442 }
443
444 switch (btf_kind(t)) {
445 case BTF_KIND_INT:
446 tstate->order_state = ORDERED;
447 return 0;
448
449 case BTF_KIND_PTR:
450 err = btf_dump_order_type(d, t->type, true);
451 tstate->order_state = ORDERED;
452 return err;
453
454 case BTF_KIND_ARRAY:
455 return btf_dump_order_type(d, btf_array(t)->type, through_ptr);
456
457 case BTF_KIND_STRUCT:
458 case BTF_KIND_UNION: {
459 const struct btf_member *m = btf_members(t);
460 /*
461 * struct/union is part of strong link, only if it's embedded
462 * (so no ptr in a path) or it's anonymous (so has to be
463 * defined inline, even if declared through ptr)
464 */
465 if (through_ptr && t->name_off != 0)
466 return 0;
467
468 tstate->order_state = ORDERING;
469
470 vlen = btf_vlen(t);
471 for (i = 0; i < vlen; i++, m++) {
472 err = btf_dump_order_type(d, m->type, false);
473 if (err < 0)
474 return err;
475 }
476
477 if (t->name_off != 0) {
478 err = btf_dump_add_emit_queue_id(d, id);
479 if (err < 0)
480 return err;
481 }
482
483 tstate->order_state = ORDERED;
484 return 1;
485 }
486 case BTF_KIND_ENUM:
487 case BTF_KIND_FWD:
488 /*
489 * non-anonymous or non-referenced enums are top-level
490 * declarations and should be emitted. Same logic can be
491 * applied to FWDs, it won't hurt anyways.
492 */
493 if (t->name_off != 0 || !tstate->referenced) {
494 err = btf_dump_add_emit_queue_id(d, id);
495 if (err)
496 return err;
497 }
498 tstate->order_state = ORDERED;
499 return 1;
500
501 case BTF_KIND_TYPEDEF: {
502 int is_strong;
503
504 is_strong = btf_dump_order_type(d, t->type, through_ptr);
505 if (is_strong < 0)
506 return is_strong;
507
508 /* typedef is similar to struct/union w.r.t. fwd-decls */
509 if (through_ptr && !is_strong)
510 return 0;
511
512 /* typedef is always a named definition */
513 err = btf_dump_add_emit_queue_id(d, id);
514 if (err)
515 return err;
516
517 d->type_states[id].order_state = ORDERED;
518 return 1;
519 }
520 case BTF_KIND_VOLATILE:
521 case BTF_KIND_CONST:
522 case BTF_KIND_RESTRICT:
523 return btf_dump_order_type(d, t->type, through_ptr);
524
525 case BTF_KIND_FUNC_PROTO: {
526 const struct btf_param *p = btf_params(t);
527 bool is_strong;
528
529 err = btf_dump_order_type(d, t->type, through_ptr);
530 if (err < 0)
531 return err;
532 is_strong = err > 0;
533
534 vlen = btf_vlen(t);
535 for (i = 0; i < vlen; i++, p++) {
536 err = btf_dump_order_type(d, p->type, through_ptr);
537 if (err < 0)
538 return err;
539 if (err > 0)
540 is_strong = true;
541 }
542 return is_strong;
543 }
544 case BTF_KIND_FUNC:
545 case BTF_KIND_VAR:
546 case BTF_KIND_DATASEC:
547 d->type_states[id].order_state = ORDERED;
548 return 0;
549
550 default:
551 return -EINVAL;
552 }
553}
554
555static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
556 const struct btf_type *t);
557
558static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
559 const struct btf_type *t);
560static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id,
561 const struct btf_type *t, int lvl);
562
563static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
564 const struct btf_type *t);
565static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
566 const struct btf_type *t, int lvl);
567
568static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
569 const struct btf_type *t);
570
571static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
572 const struct btf_type *t, int lvl);
573
574/* a local view into a shared stack */
575struct id_stack {
576 const __u32 *ids;
577 int cnt;
578};
579
580static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
581 const char *fname, int lvl);
582static void btf_dump_emit_type_chain(struct btf_dump *d,
583 struct id_stack *decl_stack,
584 const char *fname, int lvl);
585
586static const char *btf_dump_type_name(struct btf_dump *d, __u32 id);
587static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id);
588static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
589 const char *orig_name);
590
591static bool btf_dump_is_blacklisted(struct btf_dump *d, __u32 id)
592{
593 const struct btf_type *t = btf__type_by_id(d->btf, id);
594
595 /* __builtin_va_list is a compiler built-in, which causes compilation
596 * errors, when compiling w/ different compiler, then used to compile
597 * original code (e.g., GCC to compile kernel, Clang to use generated
598 * C header from BTF). As it is built-in, it should be already defined
599 * properly internally in compiler.
600 */
601 if (t->name_off == 0)
602 return false;
603 return strcmp(btf_name_of(d, t->name_off), "__builtin_va_list") == 0;
604}
605
606/*
607 * Emit C-syntax definitions of types from chains of BTF types.
608 *
609 * High-level handling of determining necessary forward declarations are handled
610 * by btf_dump_emit_type() itself, but all nitty-gritty details of emitting type
611 * declarations/definitions in C syntax are handled by a combo of
612 * btf_dump_emit_type_decl()/btf_dump_emit_type_chain() w/ delegation to
613 * corresponding btf_dump_emit_*_{def,fwd}() functions.
614 *
615 * We also keep track of "containing struct/union type ID" to determine when
616 * we reference it from inside and thus can avoid emitting unnecessary forward
617 * declaration.
618 *
619 * This algorithm is designed in such a way, that even if some error occurs
620 * (either technical, e.g., out of memory, or logical, i.e., malformed BTF
621 * that doesn't comply to C rules completely), algorithm will try to proceed
622 * and produce as much meaningful output as possible.
623 */
624static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
625{
626 struct btf_dump_type_aux_state *tstate = &d->type_states[id];
627 bool top_level_def = cont_id == 0;
628 const struct btf_type *t;
629 __u16 kind;
630
631 if (tstate->emit_state == EMITTED)
632 return;
633
634 t = btf__type_by_id(d->btf, id);
635 kind = btf_kind(t);
636
637 if (tstate->emit_state == EMITTING) {
638 if (tstate->fwd_emitted)
639 return;
640
641 switch (kind) {
642 case BTF_KIND_STRUCT:
643 case BTF_KIND_UNION:
644 /*
645 * if we are referencing a struct/union that we are
646 * part of - then no need for fwd declaration
647 */
648 if (id == cont_id)
649 return;
650 if (t->name_off == 0) {
651 pr_warn("anonymous struct/union loop, id:[%u]\n",
652 id);
653 return;
654 }
655 btf_dump_emit_struct_fwd(d, id, t);
656 btf_dump_printf(d, ";\n\n");
657 tstate->fwd_emitted = 1;
658 break;
659 case BTF_KIND_TYPEDEF:
660 /*
661 * for typedef fwd_emitted means typedef definition
662 * was emitted, but it can be used only for "weak"
663 * references through pointer only, not for embedding
664 */
665 if (!btf_dump_is_blacklisted(d, id)) {
666 btf_dump_emit_typedef_def(d, id, t, 0);
667 btf_dump_printf(d, ";\n\n");
668 }
669 tstate->fwd_emitted = 1;
670 break;
671 default:
672 break;
673 }
674
675 return;
676 }
677
678 switch (kind) {
679 case BTF_KIND_INT:
680 /* Emit type alias definitions if necessary */
681 btf_dump_emit_missing_aliases(d, id, t);
682
683 tstate->emit_state = EMITTED;
684 break;
685 case BTF_KIND_ENUM:
686 if (top_level_def) {
687 btf_dump_emit_enum_def(d, id, t, 0);
688 btf_dump_printf(d, ";\n\n");
689 }
690 tstate->emit_state = EMITTED;
691 break;
692 case BTF_KIND_PTR:
693 case BTF_KIND_VOLATILE:
694 case BTF_KIND_CONST:
695 case BTF_KIND_RESTRICT:
696 btf_dump_emit_type(d, t->type, cont_id);
697 break;
698 case BTF_KIND_ARRAY:
699 btf_dump_emit_type(d, btf_array(t)->type, cont_id);
700 break;
701 case BTF_KIND_FWD:
702 btf_dump_emit_fwd_def(d, id, t);
703 btf_dump_printf(d, ";\n\n");
704 tstate->emit_state = EMITTED;
705 break;
706 case BTF_KIND_TYPEDEF:
707 tstate->emit_state = EMITTING;
708 btf_dump_emit_type(d, t->type, id);
709 /*
710 * typedef can server as both definition and forward
711 * declaration; at this stage someone depends on
712 * typedef as a forward declaration (refers to it
713 * through pointer), so unless we already did it,
714 * emit typedef as a forward declaration
715 */
716 if (!tstate->fwd_emitted && !btf_dump_is_blacklisted(d, id)) {
717 btf_dump_emit_typedef_def(d, id, t, 0);
718 btf_dump_printf(d, ";\n\n");
719 }
720 tstate->emit_state = EMITTED;
721 break;
722 case BTF_KIND_STRUCT:
723 case BTF_KIND_UNION:
724 tstate->emit_state = EMITTING;
725 /* if it's a top-level struct/union definition or struct/union
726 * is anonymous, then in C we'll be emitting all fields and
727 * their types (as opposed to just `struct X`), so we need to
728 * make sure that all types, referenced from struct/union
729 * members have necessary forward-declarations, where
730 * applicable
731 */
732 if (top_level_def || t->name_off == 0) {
733 const struct btf_member *m = btf_members(t);
734 __u16 vlen = btf_vlen(t);
735 int i, new_cont_id;
736
737 new_cont_id = t->name_off == 0 ? cont_id : id;
738 for (i = 0; i < vlen; i++, m++)
739 btf_dump_emit_type(d, m->type, new_cont_id);
740 } else if (!tstate->fwd_emitted && id != cont_id) {
741 btf_dump_emit_struct_fwd(d, id, t);
742 btf_dump_printf(d, ";\n\n");
743 tstate->fwd_emitted = 1;
744 }
745
746 if (top_level_def) {
747 btf_dump_emit_struct_def(d, id, t, 0);
748 btf_dump_printf(d, ";\n\n");
749 tstate->emit_state = EMITTED;
750 } else {
751 tstate->emit_state = NOT_EMITTED;
752 }
753 break;
754 case BTF_KIND_FUNC_PROTO: {
755 const struct btf_param *p = btf_params(t);
756 __u16 vlen = btf_vlen(t);
757 int i;
758
759 btf_dump_emit_type(d, t->type, cont_id);
760 for (i = 0; i < vlen; i++, p++)
761 btf_dump_emit_type(d, p->type, cont_id);
762
763 break;
764 }
765 default:
766 break;
767 }
768}
769
770static bool btf_is_struct_packed(const struct btf *btf, __u32 id,
771 const struct btf_type *t)
772{
773 const struct btf_member *m;
774 int align, i, bit_sz;
775 __u16 vlen;
776
777 align = btf__align_of(btf, id);
778 /* size of a non-packed struct has to be a multiple of its alignment*/
779 if (align && t->size % align)
780 return true;
781
782 m = btf_members(t);
783 vlen = btf_vlen(t);
784 /* all non-bitfield fields have to be naturally aligned */
785 for (i = 0; i < vlen; i++, m++) {
786 align = btf__align_of(btf, m->type);
787 bit_sz = btf_member_bitfield_size(t, i);
788 if (align && bit_sz == 0 && m->offset % (8 * align) != 0)
789 return true;
790 }
791
792 /*
793 * if original struct was marked as packed, but its layout is
794 * naturally aligned, we'll detect that it's not packed
795 */
796 return false;
797}
798
799static int chip_away_bits(int total, int at_most)
800{
801 return total % at_most ? : at_most;
802}
803
804static void btf_dump_emit_bit_padding(const struct btf_dump *d,
805 int cur_off, int m_off, int m_bit_sz,
806 int align, int lvl)
807{
808 int off_diff = m_off - cur_off;
809 int ptr_bits = d->ptr_sz * 8;
810
811 if (off_diff <= 0)
812 /* no gap */
813 return;
814 if (m_bit_sz == 0 && off_diff < align * 8)
815 /* natural padding will take care of a gap */
816 return;
817
818 while (off_diff > 0) {
819 const char *pad_type;
820 int pad_bits;
821
822 if (ptr_bits > 32 && off_diff > 32) {
823 pad_type = "long";
824 pad_bits = chip_away_bits(off_diff, ptr_bits);
825 } else if (off_diff > 16) {
826 pad_type = "int";
827 pad_bits = chip_away_bits(off_diff, 32);
828 } else if (off_diff > 8) {
829 pad_type = "short";
830 pad_bits = chip_away_bits(off_diff, 16);
831 } else {
832 pad_type = "char";
833 pad_bits = chip_away_bits(off_diff, 8);
834 }
835 btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, pad_bits);
836 off_diff -= pad_bits;
837 }
838}
839
840static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
841 const struct btf_type *t)
842{
843 btf_dump_printf(d, "%s %s",
844 btf_is_struct(t) ? "struct" : "union",
845 btf_dump_type_name(d, id));
846}
847
848static void btf_dump_emit_struct_def(struct btf_dump *d,
849 __u32 id,
850 const struct btf_type *t,
851 int lvl)
852{
853 const struct btf_member *m = btf_members(t);
854 bool is_struct = btf_is_struct(t);
855 int align, i, packed, off = 0;
856 __u16 vlen = btf_vlen(t);
857
858 packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0;
859
860 btf_dump_printf(d, "%s%s%s {",
861 is_struct ? "struct" : "union",
862 t->name_off ? " " : "",
863 btf_dump_type_name(d, id));
864
865 for (i = 0; i < vlen; i++, m++) {
866 const char *fname;
867 int m_off, m_sz;
868
869 fname = btf_name_of(d, m->name_off);
870 m_sz = btf_member_bitfield_size(t, i);
871 m_off = btf_member_bit_offset(t, i);
872 align = packed ? 1 : btf__align_of(d->btf, m->type);
873
874 btf_dump_emit_bit_padding(d, off, m_off, m_sz, align, lvl + 1);
875 btf_dump_printf(d, "\n%s", pfx(lvl + 1));
876 btf_dump_emit_type_decl(d, m->type, fname, lvl + 1);
877
878 if (m_sz) {
879 btf_dump_printf(d, ": %d", m_sz);
880 off = m_off + m_sz;
881 } else {
882 m_sz = max((__s64)0, btf__resolve_size(d->btf, m->type));
883 off = m_off + m_sz * 8;
884 }
885 btf_dump_printf(d, ";");
886 }
887
888 /* pad at the end, if necessary */
889 if (is_struct) {
890 align = packed ? 1 : btf__align_of(d->btf, id);
891 btf_dump_emit_bit_padding(d, off, t->size * 8, 0, align,
892 lvl + 1);
893 }
894
895 if (vlen)
896 btf_dump_printf(d, "\n");
897 btf_dump_printf(d, "%s}", pfx(lvl));
898 if (packed)
899 btf_dump_printf(d, " __attribute__((packed))");
900}
901
902static const char *missing_base_types[][2] = {
903 /*
904 * GCC emits typedefs to its internal __PolyX_t types when compiling Arm
905 * SIMD intrinsics. Alias them to standard base types.
906 */
907 { "__Poly8_t", "unsigned char" },
908 { "__Poly16_t", "unsigned short" },
909 { "__Poly64_t", "unsigned long long" },
910 { "__Poly128_t", "unsigned __int128" },
911};
912
913static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
914 const struct btf_type *t)
915{
916 const char *name = btf_dump_type_name(d, id);
917 int i;
918
919 for (i = 0; i < ARRAY_SIZE(missing_base_types); i++) {
920 if (strcmp(name, missing_base_types[i][0]) == 0) {
921 btf_dump_printf(d, "typedef %s %s;\n\n",
922 missing_base_types[i][1], name);
923 break;
924 }
925 }
926}
927
928static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
929 const struct btf_type *t)
930{
931 btf_dump_printf(d, "enum %s", btf_dump_type_name(d, id));
932}
933
934static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
935 const struct btf_type *t,
936 int lvl)
937{
938 const struct btf_enum *v = btf_enum(t);
939 __u16 vlen = btf_vlen(t);
940 const char *name;
941 size_t dup_cnt;
942 int i;
943
944 btf_dump_printf(d, "enum%s%s",
945 t->name_off ? " " : "",
946 btf_dump_type_name(d, id));
947
948 if (vlen) {
949 btf_dump_printf(d, " {");
950 for (i = 0; i < vlen; i++, v++) {
951 name = btf_name_of(d, v->name_off);
952 /* enumerators share namespace with typedef idents */
953 dup_cnt = btf_dump_name_dups(d, d->ident_names, name);
954 if (dup_cnt > 1) {
955 btf_dump_printf(d, "\n%s%s___%zu = %u,",
956 pfx(lvl + 1), name, dup_cnt,
957 (__u32)v->val);
958 } else {
959 btf_dump_printf(d, "\n%s%s = %u,",
960 pfx(lvl + 1), name,
961 (__u32)v->val);
962 }
963 }
964 btf_dump_printf(d, "\n%s}", pfx(lvl));
965 }
966}
967
968static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
969 const struct btf_type *t)
970{
971 const char *name = btf_dump_type_name(d, id);
972
973 if (btf_kflag(t))
974 btf_dump_printf(d, "union %s", name);
975 else
976 btf_dump_printf(d, "struct %s", name);
977}
978
979static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
980 const struct btf_type *t, int lvl)
981{
982 const char *name = btf_dump_ident_name(d, id);
983
984 /*
985 * Old GCC versions are emitting invalid typedef for __gnuc_va_list
986 * pointing to VOID. This generates warnings from btf_dump() and
987 * results in uncompilable header file, so we are fixing it up here
988 * with valid typedef into __builtin_va_list.
989 */
990 if (t->type == 0 && strcmp(name, "__gnuc_va_list") == 0) {
991 btf_dump_printf(d, "typedef __builtin_va_list __gnuc_va_list");
992 return;
993 }
994
995 btf_dump_printf(d, "typedef ");
996 btf_dump_emit_type_decl(d, t->type, name, lvl);
997}
998
999static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id)
1000{
1001 __u32 *new_stack;
1002 size_t new_cap;
1003
1004 if (d->decl_stack_cnt >= d->decl_stack_cap) {
1005 new_cap = max(16, d->decl_stack_cap * 3 / 2);
1006 new_stack = realloc(d->decl_stack,
1007 new_cap * sizeof(new_stack[0]));
1008 if (!new_stack)
1009 return -ENOMEM;
1010 d->decl_stack = new_stack;
1011 d->decl_stack_cap = new_cap;
1012 }
1013
1014 d->decl_stack[d->decl_stack_cnt++] = id;
1015
1016 return 0;
1017}
1018
1019/*
1020 * Emit type declaration (e.g., field type declaration in a struct or argument
1021 * declaration in function prototype) in correct C syntax.
1022 *
1023 * For most types it's trivial, but there are few quirky type declaration
1024 * cases worth mentioning:
1025 * - function prototypes (especially nesting of function prototypes);
1026 * - arrays;
1027 * - const/volatile/restrict for pointers vs other types.
1028 *
1029 * For a good discussion of *PARSING* C syntax (as a human), see
1030 * Peter van der Linden's "Expert C Programming: Deep C Secrets",
1031 * Ch.3 "Unscrambling Declarations in C".
1032 *
1033 * It won't help with BTF to C conversion much, though, as it's an opposite
1034 * problem. So we came up with this algorithm in reverse to van der Linden's
1035 * parsing algorithm. It goes from structured BTF representation of type
1036 * declaration to a valid compilable C syntax.
1037 *
1038 * For instance, consider this C typedef:
1039 * typedef const int * const * arr[10] arr_t;
1040 * It will be represented in BTF with this chain of BTF types:
1041 * [typedef] -> [array] -> [ptr] -> [const] -> [ptr] -> [const] -> [int]
1042 *
1043 * Notice how [const] modifier always goes before type it modifies in BTF type
1044 * graph, but in C syntax, const/volatile/restrict modifiers are written to
1045 * the right of pointers, but to the left of other types. There are also other
1046 * quirks, like function pointers, arrays of them, functions returning other
1047 * functions, etc.
1048 *
1049 * We handle that by pushing all the types to a stack, until we hit "terminal"
1050 * type (int/enum/struct/union/fwd). Then depending on the kind of a type on
1051 * top of a stack, modifiers are handled differently. Array/function pointers
1052 * have also wildly different syntax and how nesting of them are done. See
1053 * code for authoritative definition.
1054 *
1055 * To avoid allocating new stack for each independent chain of BTF types, we
1056 * share one bigger stack, with each chain working only on its own local view
1057 * of a stack frame. Some care is required to "pop" stack frames after
1058 * processing type declaration chain.
1059 */
1060int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
1061 const struct btf_dump_emit_type_decl_opts *opts)
1062{
1063 const char *fname;
1064 int lvl;
1065
1066 if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts))
1067 return -EINVAL;
1068
1069 fname = OPTS_GET(opts, field_name, "");
1070 lvl = OPTS_GET(opts, indent_level, 0);
1071 d->strip_mods = OPTS_GET(opts, strip_mods, false);
1072 btf_dump_emit_type_decl(d, id, fname, lvl);
1073 d->strip_mods = false;
1074 return 0;
1075}
1076
1077static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
1078 const char *fname, int lvl)
1079{
1080 struct id_stack decl_stack;
1081 const struct btf_type *t;
1082 int err, stack_start;
1083
1084 stack_start = d->decl_stack_cnt;
1085 for (;;) {
1086 t = btf__type_by_id(d->btf, id);
1087 if (d->strip_mods && btf_is_mod(t))
1088 goto skip_mod;
1089
1090 err = btf_dump_push_decl_stack_id(d, id);
1091 if (err < 0) {
1092 /*
1093 * if we don't have enough memory for entire type decl
1094 * chain, restore stack, emit warning, and try to
1095 * proceed nevertheless
1096 */
1097 pr_warn("not enough memory for decl stack:%d", err);
1098 d->decl_stack_cnt = stack_start;
1099 return;
1100 }
1101skip_mod:
1102 /* VOID */
1103 if (id == 0)
1104 break;
1105
1106 switch (btf_kind(t)) {
1107 case BTF_KIND_PTR:
1108 case BTF_KIND_VOLATILE:
1109 case BTF_KIND_CONST:
1110 case BTF_KIND_RESTRICT:
1111 case BTF_KIND_FUNC_PROTO:
1112 id = t->type;
1113 break;
1114 case BTF_KIND_ARRAY:
1115 id = btf_array(t)->type;
1116 break;
1117 case BTF_KIND_INT:
1118 case BTF_KIND_ENUM:
1119 case BTF_KIND_FWD:
1120 case BTF_KIND_STRUCT:
1121 case BTF_KIND_UNION:
1122 case BTF_KIND_TYPEDEF:
1123 goto done;
1124 default:
1125 pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
1126 btf_kind(t), id);
1127 goto done;
1128 }
1129 }
1130done:
1131 /*
1132 * We might be inside a chain of declarations (e.g., array of function
1133 * pointers returning anonymous (so inlined) structs, having another
1134 * array field). Each of those needs its own "stack frame" to handle
1135 * emitting of declarations. Those stack frames are non-overlapping
1136 * portions of shared btf_dump->decl_stack. To make it a bit nicer to
1137 * handle this set of nested stacks, we create a view corresponding to
1138 * our own "stack frame" and work with it as an independent stack.
1139 * We'll need to clean up after emit_type_chain() returns, though.
1140 */
1141 decl_stack.ids = d->decl_stack + stack_start;
1142 decl_stack.cnt = d->decl_stack_cnt - stack_start;
1143 btf_dump_emit_type_chain(d, &decl_stack, fname, lvl);
1144 /*
1145 * emit_type_chain() guarantees that it will pop its entire decl_stack
1146 * frame before returning. But it works with a read-only view into
1147 * decl_stack, so it doesn't actually pop anything from the
1148 * perspective of shared btf_dump->decl_stack, per se. We need to
1149 * reset decl_stack state to how it was before us to avoid it growing
1150 * all the time.
1151 */
1152 d->decl_stack_cnt = stack_start;
1153}
1154
1155static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack)
1156{
1157 const struct btf_type *t;
1158 __u32 id;
1159
1160 while (decl_stack->cnt) {
1161 id = decl_stack->ids[decl_stack->cnt - 1];
1162 t = btf__type_by_id(d->btf, id);
1163
1164 switch (btf_kind(t)) {
1165 case BTF_KIND_VOLATILE:
1166 btf_dump_printf(d, "volatile ");
1167 break;
1168 case BTF_KIND_CONST:
1169 btf_dump_printf(d, "const ");
1170 break;
1171 case BTF_KIND_RESTRICT:
1172 btf_dump_printf(d, "restrict ");
1173 break;
1174 default:
1175 return;
1176 }
1177 decl_stack->cnt--;
1178 }
1179}
1180
1181static void btf_dump_drop_mods(struct btf_dump *d, struct id_stack *decl_stack)
1182{
1183 const struct btf_type *t;
1184 __u32 id;
1185
1186 while (decl_stack->cnt) {
1187 id = decl_stack->ids[decl_stack->cnt - 1];
1188 t = btf__type_by_id(d->btf, id);
1189 if (!btf_is_mod(t))
1190 return;
1191 decl_stack->cnt--;
1192 }
1193}
1194
1195static void btf_dump_emit_name(const struct btf_dump *d,
1196 const char *name, bool last_was_ptr)
1197{
1198 bool separate = name[0] && !last_was_ptr;
1199
1200 btf_dump_printf(d, "%s%s", separate ? " " : "", name);
1201}
1202
1203static void btf_dump_emit_type_chain(struct btf_dump *d,
1204 struct id_stack *decls,
1205 const char *fname, int lvl)
1206{
1207 /*
1208 * last_was_ptr is used to determine if we need to separate pointer
1209 * asterisk (*) from previous part of type signature with space, so
1210 * that we get `int ***`, instead of `int * * *`. We default to true
1211 * for cases where we have single pointer in a chain. E.g., in ptr ->
1212 * func_proto case. func_proto will start a new emit_type_chain call
1213 * with just ptr, which should be emitted as (*) or (*<fname>), so we
1214 * don't want to prepend space for that last pointer.
1215 */
1216 bool last_was_ptr = true;
1217 const struct btf_type *t;
1218 const char *name;
1219 __u16 kind;
1220 __u32 id;
1221
1222 while (decls->cnt) {
1223 id = decls->ids[--decls->cnt];
1224 if (id == 0) {
1225 /* VOID is a special snowflake */
1226 btf_dump_emit_mods(d, decls);
1227 btf_dump_printf(d, "void");
1228 last_was_ptr = false;
1229 continue;
1230 }
1231
1232 t = btf__type_by_id(d->btf, id);
1233 kind = btf_kind(t);
1234
1235 switch (kind) {
1236 case BTF_KIND_INT:
1237 btf_dump_emit_mods(d, decls);
1238 name = btf_name_of(d, t->name_off);
1239 btf_dump_printf(d, "%s", name);
1240 break;
1241 case BTF_KIND_STRUCT:
1242 case BTF_KIND_UNION:
1243 btf_dump_emit_mods(d, decls);
1244 /* inline anonymous struct/union */
1245 if (t->name_off == 0)
1246 btf_dump_emit_struct_def(d, id, t, lvl);
1247 else
1248 btf_dump_emit_struct_fwd(d, id, t);
1249 break;
1250 case BTF_KIND_ENUM:
1251 btf_dump_emit_mods(d, decls);
1252 /* inline anonymous enum */
1253 if (t->name_off == 0)
1254 btf_dump_emit_enum_def(d, id, t, lvl);
1255 else
1256 btf_dump_emit_enum_fwd(d, id, t);
1257 break;
1258 case BTF_KIND_FWD:
1259 btf_dump_emit_mods(d, decls);
1260 btf_dump_emit_fwd_def(d, id, t);
1261 break;
1262 case BTF_KIND_TYPEDEF:
1263 btf_dump_emit_mods(d, decls);
1264 btf_dump_printf(d, "%s", btf_dump_ident_name(d, id));
1265 break;
1266 case BTF_KIND_PTR:
1267 btf_dump_printf(d, "%s", last_was_ptr ? "*" : " *");
1268 break;
1269 case BTF_KIND_VOLATILE:
1270 btf_dump_printf(d, " volatile");
1271 break;
1272 case BTF_KIND_CONST:
1273 btf_dump_printf(d, " const");
1274 break;
1275 case BTF_KIND_RESTRICT:
1276 btf_dump_printf(d, " restrict");
1277 break;
1278 case BTF_KIND_ARRAY: {
1279 const struct btf_array *a = btf_array(t);
1280 const struct btf_type *next_t;
1281 __u32 next_id;
1282 bool multidim;
1283 /*
1284 * GCC has a bug
1285 * (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8354)
1286 * which causes it to emit extra const/volatile
1287 * modifiers for an array, if array's element type has
1288 * const/volatile modifiers. Clang doesn't do that.
1289 * In general, it doesn't seem very meaningful to have
1290 * a const/volatile modifier for array, so we are
1291 * going to silently skip them here.
1292 */
1293 btf_dump_drop_mods(d, decls);
1294
1295 if (decls->cnt == 0) {
1296 btf_dump_emit_name(d, fname, last_was_ptr);
1297 btf_dump_printf(d, "[%u]", a->nelems);
1298 return;
1299 }
1300
1301 next_id = decls->ids[decls->cnt - 1];
1302 next_t = btf__type_by_id(d->btf, next_id);
1303 multidim = btf_is_array(next_t);
1304 /* we need space if we have named non-pointer */
1305 if (fname[0] && !last_was_ptr)
1306 btf_dump_printf(d, " ");
1307 /* no parentheses for multi-dimensional array */
1308 if (!multidim)
1309 btf_dump_printf(d, "(");
1310 btf_dump_emit_type_chain(d, decls, fname, lvl);
1311 if (!multidim)
1312 btf_dump_printf(d, ")");
1313 btf_dump_printf(d, "[%u]", a->nelems);
1314 return;
1315 }
1316 case BTF_KIND_FUNC_PROTO: {
1317 const struct btf_param *p = btf_params(t);
1318 __u16 vlen = btf_vlen(t);
1319 int i;
1320
1321 /*
1322 * GCC emits extra volatile qualifier for
1323 * __attribute__((noreturn)) function pointers. Clang
1324 * doesn't do it. It's a GCC quirk for backwards
1325 * compatibility with code written for GCC <2.5. So,
1326 * similarly to extra qualifiers for array, just drop
1327 * them, instead of handling them.
1328 */
1329 btf_dump_drop_mods(d, decls);
1330 if (decls->cnt) {
1331 btf_dump_printf(d, " (");
1332 btf_dump_emit_type_chain(d, decls, fname, lvl);
1333 btf_dump_printf(d, ")");
1334 } else {
1335 btf_dump_emit_name(d, fname, last_was_ptr);
1336 }
1337 btf_dump_printf(d, "(");
1338 /*
1339 * Clang for BPF target generates func_proto with no
1340 * args as a func_proto with a single void arg (e.g.,
1341 * `int (*f)(void)` vs just `int (*f)()`). We are
1342 * going to pretend there are no args for such case.
1343 */
1344 if (vlen == 1 && p->type == 0) {
1345 btf_dump_printf(d, ")");
1346 return;
1347 }
1348
1349 for (i = 0; i < vlen; i++, p++) {
1350 if (i > 0)
1351 btf_dump_printf(d, ", ");
1352
1353 /* last arg of type void is vararg */
1354 if (i == vlen - 1 && p->type == 0) {
1355 btf_dump_printf(d, "...");
1356 break;
1357 }
1358
1359 name = btf_name_of(d, p->name_off);
1360 btf_dump_emit_type_decl(d, p->type, name, lvl);
1361 }
1362
1363 btf_dump_printf(d, ")");
1364 return;
1365 }
1366 default:
1367 pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
1368 kind, id);
1369 return;
1370 }
1371
1372 last_was_ptr = kind == BTF_KIND_PTR;
1373 }
1374
1375 btf_dump_emit_name(d, fname, last_was_ptr);
1376}
1377
1378/* return number of duplicates (occurrences) of a given name */
1379static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
1380 const char *orig_name)
1381{
1382 size_t dup_cnt = 0;
1383
1384 hashmap__find(name_map, orig_name, (void **)&dup_cnt);
1385 dup_cnt++;
1386 hashmap__set(name_map, orig_name, (void *)dup_cnt, NULL, NULL);
1387
1388 return dup_cnt;
1389}
1390
1391static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id,
1392 struct hashmap *name_map)
1393{
1394 struct btf_dump_type_aux_state *s = &d->type_states[id];
1395 const struct btf_type *t = btf__type_by_id(d->btf, id);
1396 const char *orig_name = btf_name_of(d, t->name_off);
1397 const char **cached_name = &d->cached_names[id];
1398 size_t dup_cnt;
1399
1400 if (t->name_off == 0)
1401 return "";
1402
1403 if (s->name_resolved)
1404 return *cached_name ? *cached_name : orig_name;
1405
1406 dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
1407 if (dup_cnt > 1) {
1408 const size_t max_len = 256;
1409 char new_name[max_len];
1410
1411 snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt);
1412 *cached_name = strdup(new_name);
1413 }
1414
1415 s->name_resolved = 1;
1416 return *cached_name ? *cached_name : orig_name;
1417}
1418
1419static const char *btf_dump_type_name(struct btf_dump *d, __u32 id)
1420{
1421 return btf_dump_resolve_name(d, id, d->type_names);
1422}
1423
1424static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id)
1425{
1426 return btf_dump_resolve_name(d, id, d->ident_names);
1427}