linux_dsm_epyc7002/tools/lib/bpf/btf_dump.c
Andrii Nakryiko 39529a9948 libbpf: Teach btf_dumper to emit stand-alone anonymous enum definitions
BTF-to-C converter previously skipped anonymous enums in an assumption
that those are embedded in struct's field definitions. This is not
always the case and a lot of kernel constants are defined as part of
anonymous enums. This change fixes the logic by eagerly marking all
types as either referenced by any other type or not. This is enough to
distinguish two classes of anonymous enums and emit previously omitted
enum definitions.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20190925203745.3173184-1-andriin@fb.com
2019-09-26 14:38:29 +02:00

1370 lines
38 KiB
C

// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/*
* BTF-to-C type converter.
*
* Copyright (c) 2019 Facebook
*/
#include <stdbool.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <linux/err.h>
#include <linux/btf.h>
#include "btf.h"
#include "hashmap.h"
#include "libbpf.h"
#include "libbpf_internal.h"
static const char PREFIXES[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t";
static const size_t PREFIX_CNT = sizeof(PREFIXES) - 1;
static const char *pfx(int lvl)
{
return lvl >= PREFIX_CNT ? PREFIXES : &PREFIXES[PREFIX_CNT - lvl];
}
enum btf_dump_type_order_state {
NOT_ORDERED,
ORDERING,
ORDERED,
};
enum btf_dump_type_emit_state {
NOT_EMITTED,
EMITTING,
EMITTED,
};
/* per-type auxiliary state */
struct btf_dump_type_aux_state {
/* topological sorting state */
enum btf_dump_type_order_state order_state: 2;
/* emitting state used to determine the need for forward declaration */
enum btf_dump_type_emit_state emit_state: 2;
/* whether forward declaration was already emitted */
__u8 fwd_emitted: 1;
/* whether unique non-duplicate name was already assigned */
__u8 name_resolved: 1;
/* whether type is referenced from any other type */
__u8 referenced: 1;
};
struct btf_dump {
const struct btf *btf;
const struct btf_ext *btf_ext;
btf_dump_printf_fn_t printf_fn;
struct btf_dump_opts opts;
/* per-type auxiliary state */
struct btf_dump_type_aux_state *type_states;
/* per-type optional cached unique name, must be freed, if present */
const char **cached_names;
/* topo-sorted list of dependent type definitions */
__u32 *emit_queue;
int emit_queue_cap;
int emit_queue_cnt;
/*
* stack of type declarations (e.g., chain of modifiers, arrays,
* funcs, etc)
*/
__u32 *decl_stack;
int decl_stack_cap;
int decl_stack_cnt;
/* maps struct/union/enum name to a number of name occurrences */
struct hashmap *type_names;
/*
* maps typedef identifiers and enum value names to a number of such
* name occurrences
*/
struct hashmap *ident_names;
};
static size_t str_hash_fn(const void *key, void *ctx)
{
const char *s = key;
size_t h = 0;
while (*s) {
h = h * 31 + *s;
s++;
}
return h;
}
static bool str_equal_fn(const void *a, const void *b, void *ctx)
{
return strcmp(a, b) == 0;
}
static const char *btf_name_of(const struct btf_dump *d, __u32 name_off)
{
return btf__name_by_offset(d->btf, name_off);
}
static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...)
{
va_list args;
va_start(args, fmt);
d->printf_fn(d->opts.ctx, fmt, args);
va_end(args);
}
struct btf_dump *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)
{
struct btf_dump *d;
int err;
d = calloc(1, sizeof(struct btf_dump));
if (!d)
return ERR_PTR(-ENOMEM);
d->btf = btf;
d->btf_ext = btf_ext;
d->printf_fn = printf_fn;
d->opts.ctx = opts ? opts->ctx : NULL;
d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
if (IS_ERR(d->type_names)) {
err = PTR_ERR(d->type_names);
d->type_names = NULL;
btf_dump__free(d);
return ERR_PTR(err);
}
d->ident_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
if (IS_ERR(d->ident_names)) {
err = PTR_ERR(d->ident_names);
d->ident_names = NULL;
btf_dump__free(d);
return ERR_PTR(err);
}
return d;
}
void btf_dump__free(struct btf_dump *d)
{
int i, cnt;
if (!d)
return;
free(d->type_states);
if (d->cached_names) {
/* any set cached name is owned by us and should be freed */
for (i = 0, cnt = btf__get_nr_types(d->btf); i <= cnt; i++) {
if (d->cached_names[i])
free((void *)d->cached_names[i]);
}
}
free(d->cached_names);
free(d->emit_queue);
free(d->decl_stack);
hashmap__free(d->type_names);
hashmap__free(d->ident_names);
free(d);
}
static int btf_dump_mark_referenced(struct btf_dump *d);
static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr);
static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id);
/*
* Dump BTF type in a compilable C syntax, including all the necessary
* dependent types, necessary for compilation. If some of the dependent types
* were already emitted as part of previous btf_dump__dump_type() invocation
* for another type, they won't be emitted again. This API allows callers to
* filter out BTF types according to user-defined criterias and emitted only
* minimal subset of types, necessary to compile everything. Full struct/union
* definitions will still be emitted, even if the only usage is through
* pointer and could be satisfied with just a forward declaration.
*
* Dumping is done in two high-level passes:
* 1. Topologically sort type definitions to satisfy C rules of compilation.
* 2. Emit type definitions in C syntax.
*
* Returns 0 on success; <0, otherwise.
*/
int btf_dump__dump_type(struct btf_dump *d, __u32 id)
{
int err, i;
if (id > btf__get_nr_types(d->btf))
return -EINVAL;
/* type states are lazily allocated, as they might not be needed */
if (!d->type_states) {
d->type_states = calloc(1 + btf__get_nr_types(d->btf),
sizeof(d->type_states[0]));
if (!d->type_states)
return -ENOMEM;
d->cached_names = calloc(1 + btf__get_nr_types(d->btf),
sizeof(d->cached_names[0]));
if (!d->cached_names)
return -ENOMEM;
/* VOID is special */
d->type_states[0].order_state = ORDERED;
d->type_states[0].emit_state = EMITTED;
/* eagerly determine referenced types for anon enums */
err = btf_dump_mark_referenced(d);
if (err)
return err;
}
d->emit_queue_cnt = 0;
err = btf_dump_order_type(d, id, false);
if (err < 0)
return err;
for (i = 0; i < d->emit_queue_cnt; i++)
btf_dump_emit_type(d, d->emit_queue[i], 0 /*top-level*/);
return 0;
}
/*
* Mark all types that are referenced from any other type. This is used to
* determine top-level anonymous enums that need to be emitted as an
* independent type declarations.
* Anonymous enums come in two flavors: either embedded in a struct's field
* definition, in which case they have to be declared inline as part of field
* type declaration; or as a top-level anonymous enum, typically used for
* declaring global constants. It's impossible to distinguish between two
* without knowning whether given enum type was referenced from other type:
* top-level anonymous enum won't be referenced by anything, while embedded
* one will.
*/
static int btf_dump_mark_referenced(struct btf_dump *d)
{
int i, j, n = btf__get_nr_types(d->btf);
const struct btf_type *t;
__u16 vlen;
for (i = 1; i <= n; i++) {
t = btf__type_by_id(d->btf, i);
vlen = btf_vlen(t);
switch (btf_kind(t)) {
case BTF_KIND_INT:
case BTF_KIND_ENUM:
case BTF_KIND_FWD:
break;
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_VAR:
d->type_states[t->type].referenced = 1;
break;
case BTF_KIND_ARRAY: {
const struct btf_array *a = btf_array(t);
d->type_states[a->index_type].referenced = 1;
d->type_states[a->type].referenced = 1;
break;
}
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
const struct btf_member *m = btf_members(t);
for (j = 0; j < vlen; j++, m++)
d->type_states[m->type].referenced = 1;
break;
}
case BTF_KIND_FUNC_PROTO: {
const struct btf_param *p = btf_params(t);
for (j = 0; j < vlen; j++, p++)
d->type_states[p->type].referenced = 1;
break;
}
case BTF_KIND_DATASEC: {
const struct btf_var_secinfo *v = btf_var_secinfos(t);
for (j = 0; j < vlen; j++, v++)
d->type_states[v->type].referenced = 1;
break;
}
default:
return -EINVAL;
}
}
return 0;
}
static int btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id)
{
__u32 *new_queue;
size_t new_cap;
if (d->emit_queue_cnt >= d->emit_queue_cap) {
new_cap = max(16, d->emit_queue_cap * 3 / 2);
new_queue = realloc(d->emit_queue,
new_cap * sizeof(new_queue[0]));
if (!new_queue)
return -ENOMEM;
d->emit_queue = new_queue;
d->emit_queue_cap = new_cap;
}
d->emit_queue[d->emit_queue_cnt++] = id;
return 0;
}
/*
* Determine order of emitting dependent types and specified type to satisfy
* C compilation rules. This is done through topological sorting with an
* additional complication which comes from C rules. The main idea for C is
* that if some type is "embedded" into a struct/union, it's size needs to be
* known at the time of definition of containing type. E.g., for:
*
* struct A {};
* struct B { struct A x; }
*
* struct A *HAS* to be defined before struct B, because it's "embedded",
* i.e., it is part of struct B layout. But in the following case:
*
* struct A;
* struct B { struct A *x; }
* struct A {};
*
* it's enough to just have a forward declaration of struct A at the time of
* struct B definition, as struct B has a pointer to struct A, so the size of
* field x is known without knowing struct A size: it's sizeof(void *).
*
* Unfortunately, there are some trickier cases we need to handle, e.g.:
*
* struct A {}; // if this was forward-declaration: compilation error
* struct B {
* struct { // anonymous struct
* struct A y;
* } *x;
* };
*
* In this case, struct B's field x is a pointer, so it's size is known
* regardless of the size of (anonymous) struct it points to. But because this
* struct is anonymous and thus defined inline inside struct B, *and* it
* embeds struct A, compiler requires full definition of struct A to be known
* before struct B can be defined. This creates a transitive dependency
* between struct A and struct B. If struct A was forward-declared before
* struct B definition and fully defined after struct B definition, that would
* trigger compilation error.
*
* All this means that while we are doing topological sorting on BTF type
* graph, we need to determine relationships between different types (graph
* nodes):
* - weak link (relationship) between X and Y, if Y *CAN* be
* forward-declared at the point of X definition;
* - strong link, if Y *HAS* to be fully-defined before X can be defined.
*
* The rule is as follows. Given a chain of BTF types from X to Y, if there is
* BTF_KIND_PTR type in the chain and at least one non-anonymous type
* Z (excluding X, including Y), then link is weak. Otherwise, it's strong.
* Weak/strong relationship is determined recursively during DFS traversal and
* is returned as a result from btf_dump_order_type().
*
* btf_dump_order_type() is trying to avoid unnecessary forward declarations,
* but it is not guaranteeing that no extraneous forward declarations will be
* emitted.
*
* To avoid extra work, algorithm marks some of BTF types as ORDERED, when
* it's done with them, but not for all (e.g., VOLATILE, CONST, RESTRICT,
* ARRAY, FUNC_PROTO), as weak/strong semantics for those depends on the
* entire graph path, so depending where from one came to that BTF type, it
* might cause weak or strong ordering. For types like STRUCT/UNION/INT/ENUM,
* once they are processed, there is no need to do it again, so they are
* marked as ORDERED. We can mark PTR as ORDERED as well, as it semi-forces
* weak link, unless subsequent referenced STRUCT/UNION/ENUM is anonymous. But
* in any case, once those are processed, no need to do it again, as the
* result won't change.
*
* Returns:
* - 1, if type is part of strong link (so there is strong topological
* ordering requirements);
* - 0, if type is part of weak link (so can be satisfied through forward
* declaration);
* - <0, on error (e.g., unsatisfiable type loop detected).
*/
static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
{
/*
* Order state is used to detect strong link cycles, but only for BTF
* kinds that are or could be an independent definition (i.e.,
* stand-alone fwd decl, enum, typedef, struct, union). Ptrs, arrays,
* func_protos, modifiers are just means to get to these definitions.
* Int/void don't need definitions, they are assumed to be always
* properly defined. We also ignore datasec, var, and funcs for now.
* So for all non-defining kinds, we never even set ordering state,
* for defining kinds we set ORDERING and subsequently ORDERED if it
* forms a strong link.
*/
struct btf_dump_type_aux_state *tstate = &d->type_states[id];
const struct btf_type *t;
__u16 vlen;
int err, i;
/* return true, letting typedefs know that it's ok to be emitted */
if (tstate->order_state == ORDERED)
return 1;
t = btf__type_by_id(d->btf, id);
if (tstate->order_state == ORDERING) {
/* type loop, but resolvable through fwd declaration */
if (btf_is_composite(t) && through_ptr && t->name_off != 0)
return 0;
pr_warning("unsatisfiable type cycle, id:[%u]\n", id);
return -ELOOP;
}
switch (btf_kind(t)) {
case BTF_KIND_INT:
tstate->order_state = ORDERED;
return 0;
case BTF_KIND_PTR:
err = btf_dump_order_type(d, t->type, true);
tstate->order_state = ORDERED;
return err;
case BTF_KIND_ARRAY:
return btf_dump_order_type(d, btf_array(t)->type, through_ptr);
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
const struct btf_member *m = btf_members(t);
/*
* struct/union is part of strong link, only if it's embedded
* (so no ptr in a path) or it's anonymous (so has to be
* defined inline, even if declared through ptr)
*/
if (through_ptr && t->name_off != 0)
return 0;
tstate->order_state = ORDERING;
vlen = btf_vlen(t);
for (i = 0; i < vlen; i++, m++) {
err = btf_dump_order_type(d, m->type, false);
if (err < 0)
return err;
}
if (t->name_off != 0) {
err = btf_dump_add_emit_queue_id(d, id);
if (err < 0)
return err;
}
tstate->order_state = ORDERED;
return 1;
}
case BTF_KIND_ENUM:
case BTF_KIND_FWD:
/*
* non-anonymous or non-referenced enums are top-level
* declarations and should be emitted. Same logic can be
* applied to FWDs, it won't hurt anyways.
*/
if (t->name_off != 0 || !tstate->referenced) {
err = btf_dump_add_emit_queue_id(d, id);
if (err)
return err;
}
tstate->order_state = ORDERED;
return 1;
case BTF_KIND_TYPEDEF: {
int is_strong;
is_strong = btf_dump_order_type(d, t->type, through_ptr);
if (is_strong < 0)
return is_strong;
/* typedef is similar to struct/union w.r.t. fwd-decls */
if (through_ptr && !is_strong)
return 0;
/* typedef is always a named definition */
err = btf_dump_add_emit_queue_id(d, id);
if (err)
return err;
d->type_states[id].order_state = ORDERED;
return 1;
}
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
return btf_dump_order_type(d, t->type, through_ptr);
case BTF_KIND_FUNC_PROTO: {
const struct btf_param *p = btf_params(t);
bool is_strong;
err = btf_dump_order_type(d, t->type, through_ptr);
if (err < 0)
return err;
is_strong = err > 0;
vlen = btf_vlen(t);
for (i = 0; i < vlen; i++, p++) {
err = btf_dump_order_type(d, p->type, through_ptr);
if (err < 0)
return err;
if (err > 0)
is_strong = true;
}
return is_strong;
}
case BTF_KIND_FUNC:
case BTF_KIND_VAR:
case BTF_KIND_DATASEC:
d->type_states[id].order_state = ORDERED;
return 0;
default:
return -EINVAL;
}
}
static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
const struct btf_type *t);
static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id,
const struct btf_type *t, int lvl);
static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
const struct btf_type *t);
static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
const struct btf_type *t, int lvl);
static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
const struct btf_type *t);
static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
const struct btf_type *t, int lvl);
/* a local view into a shared stack */
struct id_stack {
const __u32 *ids;
int cnt;
};
static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
const char *fname, int lvl);
static void btf_dump_emit_type_chain(struct btf_dump *d,
struct id_stack *decl_stack,
const char *fname, int lvl);
static const char *btf_dump_type_name(struct btf_dump *d, __u32 id);
static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id);
static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
const char *orig_name);
static bool btf_dump_is_blacklisted(struct btf_dump *d, __u32 id)
{
const struct btf_type *t = btf__type_by_id(d->btf, id);
/* __builtin_va_list is a compiler built-in, which causes compilation
* errors, when compiling w/ different compiler, then used to compile
* original code (e.g., GCC to compile kernel, Clang to use generated
* C header from BTF). As it is built-in, it should be already defined
* properly internally in compiler.
*/
if (t->name_off == 0)
return false;
return strcmp(btf_name_of(d, t->name_off), "__builtin_va_list") == 0;
}
/*
* Emit C-syntax definitions of types from chains of BTF types.
*
* High-level handling of determining necessary forward declarations are handled
* by btf_dump_emit_type() itself, but all nitty-gritty details of emitting type
* declarations/definitions in C syntax are handled by a combo of
* btf_dump_emit_type_decl()/btf_dump_emit_type_chain() w/ delegation to
* corresponding btf_dump_emit_*_{def,fwd}() functions.
*
* We also keep track of "containing struct/union type ID" to determine when
* we reference it from inside and thus can avoid emitting unnecessary forward
* declaration.
*
* This algorithm is designed in such a way, that even if some error occurs
* (either technical, e.g., out of memory, or logical, i.e., malformed BTF
* that doesn't comply to C rules completely), algorithm will try to proceed
* and produce as much meaningful output as possible.
*/
static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
{
struct btf_dump_type_aux_state *tstate = &d->type_states[id];
bool top_level_def = cont_id == 0;
const struct btf_type *t;
__u16 kind;
if (tstate->emit_state == EMITTED)
return;
t = btf__type_by_id(d->btf, id);
kind = btf_kind(t);
if (tstate->emit_state == EMITTING) {
if (tstate->fwd_emitted)
return;
switch (kind) {
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
/*
* if we are referencing a struct/union that we are
* part of - then no need for fwd declaration
*/
if (id == cont_id)
return;
if (t->name_off == 0) {
pr_warning("anonymous struct/union loop, id:[%u]\n",
id);
return;
}
btf_dump_emit_struct_fwd(d, id, t);
btf_dump_printf(d, ";\n\n");
tstate->fwd_emitted = 1;
break;
case BTF_KIND_TYPEDEF:
/*
* for typedef fwd_emitted means typedef definition
* was emitted, but it can be used only for "weak"
* references through pointer only, not for embedding
*/
if (!btf_dump_is_blacklisted(d, id)) {
btf_dump_emit_typedef_def(d, id, t, 0);
btf_dump_printf(d, ";\n\n");
};
tstate->fwd_emitted = 1;
break;
default:
break;
}
return;
}
switch (kind) {
case BTF_KIND_INT:
tstate->emit_state = EMITTED;
break;
case BTF_KIND_ENUM:
if (top_level_def) {
btf_dump_emit_enum_def(d, id, t, 0);
btf_dump_printf(d, ";\n\n");
}
tstate->emit_state = EMITTED;
break;
case BTF_KIND_PTR:
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
btf_dump_emit_type(d, t->type, cont_id);
break;
case BTF_KIND_ARRAY:
btf_dump_emit_type(d, btf_array(t)->type, cont_id);
break;
case BTF_KIND_FWD:
btf_dump_emit_fwd_def(d, id, t);
btf_dump_printf(d, ";\n\n");
tstate->emit_state = EMITTED;
break;
case BTF_KIND_TYPEDEF:
tstate->emit_state = EMITTING;
btf_dump_emit_type(d, t->type, id);
/*
* typedef can server as both definition and forward
* declaration; at this stage someone depends on
* typedef as a forward declaration (refers to it
* through pointer), so unless we already did it,
* emit typedef as a forward declaration
*/
if (!tstate->fwd_emitted && !btf_dump_is_blacklisted(d, id)) {
btf_dump_emit_typedef_def(d, id, t, 0);
btf_dump_printf(d, ";\n\n");
}
tstate->emit_state = EMITTED;
break;
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
tstate->emit_state = EMITTING;
/* if it's a top-level struct/union definition or struct/union
* is anonymous, then in C we'll be emitting all fields and
* their types (as opposed to just `struct X`), so we need to
* make sure that all types, referenced from struct/union
* members have necessary forward-declarations, where
* applicable
*/
if (top_level_def || t->name_off == 0) {
const struct btf_member *m = btf_members(t);
__u16 vlen = btf_vlen(t);
int i, new_cont_id;
new_cont_id = t->name_off == 0 ? cont_id : id;
for (i = 0; i < vlen; i++, m++)
btf_dump_emit_type(d, m->type, new_cont_id);
} else if (!tstate->fwd_emitted && id != cont_id) {
btf_dump_emit_struct_fwd(d, id, t);
btf_dump_printf(d, ";\n\n");
tstate->fwd_emitted = 1;
}
if (top_level_def) {
btf_dump_emit_struct_def(d, id, t, 0);
btf_dump_printf(d, ";\n\n");
tstate->emit_state = EMITTED;
} else {
tstate->emit_state = NOT_EMITTED;
}
break;
case BTF_KIND_FUNC_PROTO: {
const struct btf_param *p = btf_params(t);
__u16 vlen = btf_vlen(t);
int i;
btf_dump_emit_type(d, t->type, cont_id);
for (i = 0; i < vlen; i++, p++)
btf_dump_emit_type(d, p->type, cont_id);
break;
}
default:
break;
}
}
static int btf_align_of(const struct btf *btf, __u32 id)
{
const struct btf_type *t = btf__type_by_id(btf, id);
__u16 kind = btf_kind(t);
switch (kind) {
case BTF_KIND_INT:
case BTF_KIND_ENUM:
return min(sizeof(void *), t->size);
case BTF_KIND_PTR:
return sizeof(void *);
case BTF_KIND_TYPEDEF:
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
return btf_align_of(btf, t->type);
case BTF_KIND_ARRAY:
return btf_align_of(btf, btf_array(t)->type);
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
const struct btf_member *m = btf_members(t);
__u16 vlen = btf_vlen(t);
int i, align = 1;
for (i = 0; i < vlen; i++, m++)
align = max(align, btf_align_of(btf, m->type));
return align;
}
default:
pr_warning("unsupported BTF_KIND:%u\n", btf_kind(t));
return 1;
}
}
static bool btf_is_struct_packed(const struct btf *btf, __u32 id,
const struct btf_type *t)
{
const struct btf_member *m;
int align, i, bit_sz;
__u16 vlen;
align = btf_align_of(btf, id);
/* size of a non-packed struct has to be a multiple of its alignment*/
if (t->size % align)
return true;
m = btf_members(t);
vlen = btf_vlen(t);
/* all non-bitfield fields have to be naturally aligned */
for (i = 0; i < vlen; i++, m++) {
align = btf_align_of(btf, m->type);
bit_sz = btf_member_bitfield_size(t, i);
if (bit_sz == 0 && m->offset % (8 * align) != 0)
return true;
}
/*
* if original struct was marked as packed, but its layout is
* naturally aligned, we'll detect that it's not packed
*/
return false;
}
static int chip_away_bits(int total, int at_most)
{
return total % at_most ? : at_most;
}
static void btf_dump_emit_bit_padding(const struct btf_dump *d,
int cur_off, int m_off, int m_bit_sz,
int align, int lvl)
{
int off_diff = m_off - cur_off;
int ptr_bits = sizeof(void *) * 8;
if (off_diff <= 0)
/* no gap */
return;
if (m_bit_sz == 0 && off_diff < align * 8)
/* natural padding will take care of a gap */
return;
while (off_diff > 0) {
const char *pad_type;
int pad_bits;
if (ptr_bits > 32 && off_diff > 32) {
pad_type = "long";
pad_bits = chip_away_bits(off_diff, ptr_bits);
} else if (off_diff > 16) {
pad_type = "int";
pad_bits = chip_away_bits(off_diff, 32);
} else if (off_diff > 8) {
pad_type = "short";
pad_bits = chip_away_bits(off_diff, 16);
} else {
pad_type = "char";
pad_bits = chip_away_bits(off_diff, 8);
}
btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, pad_bits);
off_diff -= pad_bits;
}
}
static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
const struct btf_type *t)
{
btf_dump_printf(d, "%s %s",
btf_is_struct(t) ? "struct" : "union",
btf_dump_type_name(d, id));
}
static void btf_dump_emit_struct_def(struct btf_dump *d,
__u32 id,
const struct btf_type *t,
int lvl)
{
const struct btf_member *m = btf_members(t);
bool is_struct = btf_is_struct(t);
int align, i, packed, off = 0;
__u16 vlen = btf_vlen(t);
packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0;
align = packed ? 1 : btf_align_of(d->btf, id);
btf_dump_printf(d, "%s%s%s {",
is_struct ? "struct" : "union",
t->name_off ? " " : "",
btf_dump_type_name(d, id));
for (i = 0; i < vlen; i++, m++) {
const char *fname;
int m_off, m_sz;
fname = btf_name_of(d, m->name_off);
m_sz = btf_member_bitfield_size(t, i);
m_off = btf_member_bit_offset(t, i);
align = packed ? 1 : btf_align_of(d->btf, m->type);
btf_dump_emit_bit_padding(d, off, m_off, m_sz, align, lvl + 1);
btf_dump_printf(d, "\n%s", pfx(lvl + 1));
btf_dump_emit_type_decl(d, m->type, fname, lvl + 1);
if (m_sz) {
btf_dump_printf(d, ": %d", m_sz);
off = m_off + m_sz;
} else {
m_sz = max(0, btf__resolve_size(d->btf, m->type));
off = m_off + m_sz * 8;
}
btf_dump_printf(d, ";");
}
if (vlen)
btf_dump_printf(d, "\n");
btf_dump_printf(d, "%s}", pfx(lvl));
if (packed)
btf_dump_printf(d, " __attribute__((packed))");
}
static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
const struct btf_type *t)
{
btf_dump_printf(d, "enum %s", btf_dump_type_name(d, id));
}
static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
const struct btf_type *t,
int lvl)
{
const struct btf_enum *v = btf_enum(t);
__u16 vlen = btf_vlen(t);
const char *name;
size_t dup_cnt;
int i;
btf_dump_printf(d, "enum%s%s",
t->name_off ? " " : "",
btf_dump_type_name(d, id));
if (vlen) {
btf_dump_printf(d, " {");
for (i = 0; i < vlen; i++, v++) {
name = btf_name_of(d, v->name_off);
/* enumerators share namespace with typedef idents */
dup_cnt = btf_dump_name_dups(d, d->ident_names, name);
if (dup_cnt > 1) {
btf_dump_printf(d, "\n%s%s___%zu = %d,",
pfx(lvl + 1), name, dup_cnt,
(__s32)v->val);
} else {
btf_dump_printf(d, "\n%s%s = %d,",
pfx(lvl + 1), name,
(__s32)v->val);
}
}
btf_dump_printf(d, "\n%s}", pfx(lvl));
}
}
static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
const struct btf_type *t)
{
const char *name = btf_dump_type_name(d, id);
if (btf_kflag(t))
btf_dump_printf(d, "union %s", name);
else
btf_dump_printf(d, "struct %s", name);
}
static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
const struct btf_type *t, int lvl)
{
const char *name = btf_dump_ident_name(d, id);
btf_dump_printf(d, "typedef ");
btf_dump_emit_type_decl(d, t->type, name, lvl);
}
static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id)
{
__u32 *new_stack;
size_t new_cap;
if (d->decl_stack_cnt >= d->decl_stack_cap) {
new_cap = max(16, d->decl_stack_cap * 3 / 2);
new_stack = realloc(d->decl_stack,
new_cap * sizeof(new_stack[0]));
if (!new_stack)
return -ENOMEM;
d->decl_stack = new_stack;
d->decl_stack_cap = new_cap;
}
d->decl_stack[d->decl_stack_cnt++] = id;
return 0;
}
/*
* Emit type declaration (e.g., field type declaration in a struct or argument
* declaration in function prototype) in correct C syntax.
*
* For most types it's trivial, but there are few quirky type declaration
* cases worth mentioning:
* - function prototypes (especially nesting of function prototypes);
* - arrays;
* - const/volatile/restrict for pointers vs other types.
*
* For a good discussion of *PARSING* C syntax (as a human), see
* Peter van der Linden's "Expert C Programming: Deep C Secrets",
* Ch.3 "Unscrambling Declarations in C".
*
* It won't help with BTF to C conversion much, though, as it's an opposite
* problem. So we came up with this algorithm in reverse to van der Linden's
* parsing algorithm. It goes from structured BTF representation of type
* declaration to a valid compilable C syntax.
*
* For instance, consider this C typedef:
* typedef const int * const * arr[10] arr_t;
* It will be represented in BTF with this chain of BTF types:
* [typedef] -> [array] -> [ptr] -> [const] -> [ptr] -> [const] -> [int]
*
* Notice how [const] modifier always goes before type it modifies in BTF type
* graph, but in C syntax, const/volatile/restrict modifiers are written to
* the right of pointers, but to the left of other types. There are also other
* quirks, like function pointers, arrays of them, functions returning other
* functions, etc.
*
* We handle that by pushing all the types to a stack, until we hit "terminal"
* type (int/enum/struct/union/fwd). Then depending on the kind of a type on
* top of a stack, modifiers are handled differently. Array/function pointers
* have also wildly different syntax and how nesting of them are done. See
* code for authoritative definition.
*
* To avoid allocating new stack for each independent chain of BTF types, we
* share one bigger stack, with each chain working only on its own local view
* of a stack frame. Some care is required to "pop" stack frames after
* processing type declaration chain.
*/
static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
const char *fname, int lvl)
{
struct id_stack decl_stack;
const struct btf_type *t;
int err, stack_start;
stack_start = d->decl_stack_cnt;
for (;;) {
err = btf_dump_push_decl_stack_id(d, id);
if (err < 0) {
/*
* if we don't have enough memory for entire type decl
* chain, restore stack, emit warning, and try to
* proceed nevertheless
*/
pr_warning("not enough memory for decl stack:%d", err);
d->decl_stack_cnt = stack_start;
return;
}
/* VOID */
if (id == 0)
break;
t = btf__type_by_id(d->btf, id);
switch (btf_kind(t)) {
case BTF_KIND_PTR:
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
case BTF_KIND_FUNC_PROTO:
id = t->type;
break;
case BTF_KIND_ARRAY:
id = btf_array(t)->type;
break;
case BTF_KIND_INT:
case BTF_KIND_ENUM:
case BTF_KIND_FWD:
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
case BTF_KIND_TYPEDEF:
goto done;
default:
pr_warning("unexpected type in decl chain, kind:%u, id:[%u]\n",
btf_kind(t), id);
goto done;
}
}
done:
/*
* We might be inside a chain of declarations (e.g., array of function
* pointers returning anonymous (so inlined) structs, having another
* array field). Each of those needs its own "stack frame" to handle
* emitting of declarations. Those stack frames are non-overlapping
* portions of shared btf_dump->decl_stack. To make it a bit nicer to
* handle this set of nested stacks, we create a view corresponding to
* our own "stack frame" and work with it as an independent stack.
* We'll need to clean up after emit_type_chain() returns, though.
*/
decl_stack.ids = d->decl_stack + stack_start;
decl_stack.cnt = d->decl_stack_cnt - stack_start;
btf_dump_emit_type_chain(d, &decl_stack, fname, lvl);
/*
* emit_type_chain() guarantees that it will pop its entire decl_stack
* frame before returning. But it works with a read-only view into
* decl_stack, so it doesn't actually pop anything from the
* perspective of shared btf_dump->decl_stack, per se. We need to
* reset decl_stack state to how it was before us to avoid it growing
* all the time.
*/
d->decl_stack_cnt = stack_start;
}
static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack)
{
const struct btf_type *t;
__u32 id;
while (decl_stack->cnt) {
id = decl_stack->ids[decl_stack->cnt - 1];
t = btf__type_by_id(d->btf, id);
switch (btf_kind(t)) {
case BTF_KIND_VOLATILE:
btf_dump_printf(d, "volatile ");
break;
case BTF_KIND_CONST:
btf_dump_printf(d, "const ");
break;
case BTF_KIND_RESTRICT:
btf_dump_printf(d, "restrict ");
break;
default:
return;
}
decl_stack->cnt--;
}
}
static void btf_dump_emit_name(const struct btf_dump *d,
const char *name, bool last_was_ptr)
{
bool separate = name[0] && !last_was_ptr;
btf_dump_printf(d, "%s%s", separate ? " " : "", name);
}
static void btf_dump_emit_type_chain(struct btf_dump *d,
struct id_stack *decls,
const char *fname, int lvl)
{
/*
* last_was_ptr is used to determine if we need to separate pointer
* asterisk (*) from previous part of type signature with space, so
* that we get `int ***`, instead of `int * * *`. We default to true
* for cases where we have single pointer in a chain. E.g., in ptr ->
* func_proto case. func_proto will start a new emit_type_chain call
* with just ptr, which should be emitted as (*) or (*<fname>), so we
* don't want to prepend space for that last pointer.
*/
bool last_was_ptr = true;
const struct btf_type *t;
const char *name;
__u16 kind;
__u32 id;
while (decls->cnt) {
id = decls->ids[--decls->cnt];
if (id == 0) {
/* VOID is a special snowflake */
btf_dump_emit_mods(d, decls);
btf_dump_printf(d, "void");
last_was_ptr = false;
continue;
}
t = btf__type_by_id(d->btf, id);
kind = btf_kind(t);
switch (kind) {
case BTF_KIND_INT:
btf_dump_emit_mods(d, decls);
name = btf_name_of(d, t->name_off);
btf_dump_printf(d, "%s", name);
break;
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
btf_dump_emit_mods(d, decls);
/* inline anonymous struct/union */
if (t->name_off == 0)
btf_dump_emit_struct_def(d, id, t, lvl);
else
btf_dump_emit_struct_fwd(d, id, t);
break;
case BTF_KIND_ENUM:
btf_dump_emit_mods(d, decls);
/* inline anonymous enum */
if (t->name_off == 0)
btf_dump_emit_enum_def(d, id, t, lvl);
else
btf_dump_emit_enum_fwd(d, id, t);
break;
case BTF_KIND_FWD:
btf_dump_emit_mods(d, decls);
btf_dump_emit_fwd_def(d, id, t);
break;
case BTF_KIND_TYPEDEF:
btf_dump_emit_mods(d, decls);
btf_dump_printf(d, "%s", btf_dump_ident_name(d, id));
break;
case BTF_KIND_PTR:
btf_dump_printf(d, "%s", last_was_ptr ? "*" : " *");
break;
case BTF_KIND_VOLATILE:
btf_dump_printf(d, " volatile");
break;
case BTF_KIND_CONST:
btf_dump_printf(d, " const");
break;
case BTF_KIND_RESTRICT:
btf_dump_printf(d, " restrict");
break;
case BTF_KIND_ARRAY: {
const struct btf_array *a = btf_array(t);
const struct btf_type *next_t;
__u32 next_id;
bool multidim;
/*
* GCC has a bug
* (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8354)
* which causes it to emit extra const/volatile
* modifiers for an array, if array's element type has
* const/volatile modifiers. Clang doesn't do that.
* In general, it doesn't seem very meaningful to have
* a const/volatile modifier for array, so we are
* going to silently skip them here.
*/
while (decls->cnt) {
next_id = decls->ids[decls->cnt - 1];
next_t = btf__type_by_id(d->btf, next_id);
if (btf_is_mod(next_t))
decls->cnt--;
else
break;
}
if (decls->cnt == 0) {
btf_dump_emit_name(d, fname, last_was_ptr);
btf_dump_printf(d, "[%u]", a->nelems);
return;
}
next_id = decls->ids[decls->cnt - 1];
next_t = btf__type_by_id(d->btf, next_id);
multidim = btf_is_array(next_t);
/* we need space if we have named non-pointer */
if (fname[0] && !last_was_ptr)
btf_dump_printf(d, " ");
/* no parentheses for multi-dimensional array */
if (!multidim)
btf_dump_printf(d, "(");
btf_dump_emit_type_chain(d, decls, fname, lvl);
if (!multidim)
btf_dump_printf(d, ")");
btf_dump_printf(d, "[%u]", a->nelems);
return;
}
case BTF_KIND_FUNC_PROTO: {
const struct btf_param *p = btf_params(t);
__u16 vlen = btf_vlen(t);
int i;
btf_dump_emit_mods(d, decls);
if (decls->cnt) {
btf_dump_printf(d, " (");
btf_dump_emit_type_chain(d, decls, fname, lvl);
btf_dump_printf(d, ")");
} else {
btf_dump_emit_name(d, fname, last_was_ptr);
}
btf_dump_printf(d, "(");
/*
* Clang for BPF target generates func_proto with no
* args as a func_proto with a single void arg (e.g.,
* `int (*f)(void)` vs just `int (*f)()`). We are
* going to pretend there are no args for such case.
*/
if (vlen == 1 && p->type == 0) {
btf_dump_printf(d, ")");
return;
}
for (i = 0; i < vlen; i++, p++) {
if (i > 0)
btf_dump_printf(d, ", ");
/* last arg of type void is vararg */
if (i == vlen - 1 && p->type == 0) {
btf_dump_printf(d, "...");
break;
}
name = btf_name_of(d, p->name_off);
btf_dump_emit_type_decl(d, p->type, name, lvl);
}
btf_dump_printf(d, ")");
return;
}
default:
pr_warning("unexpected type in decl chain, kind:%u, id:[%u]\n",
kind, id);
return;
}
last_was_ptr = kind == BTF_KIND_PTR;
}
btf_dump_emit_name(d, fname, last_was_ptr);
}
/* return number of duplicates (occurrences) of a given name */
static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
const char *orig_name)
{
size_t dup_cnt = 0;
hashmap__find(name_map, orig_name, (void **)&dup_cnt);
dup_cnt++;
hashmap__set(name_map, orig_name, (void *)dup_cnt, NULL, NULL);
return dup_cnt;
}
static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id,
struct hashmap *name_map)
{
struct btf_dump_type_aux_state *s = &d->type_states[id];
const struct btf_type *t = btf__type_by_id(d->btf, id);
const char *orig_name = btf_name_of(d, t->name_off);
const char **cached_name = &d->cached_names[id];
size_t dup_cnt;
if (t->name_off == 0)
return "";
if (s->name_resolved)
return *cached_name ? *cached_name : orig_name;
dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
if (dup_cnt > 1) {
const size_t max_len = 256;
char new_name[max_len];
snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt);
*cached_name = strdup(new_name);
}
s->name_resolved = 1;
return *cached_name ? *cached_name : orig_name;
}
static const char *btf_dump_type_name(struct btf_dump *d, __u32 id)
{
return btf_dump_resolve_name(d, id, d->type_names);
}
static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id)
{
return btf_dump_resolve_name(d, id, d->ident_names);
}