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libbpf: Expose BTF-to-C type declaration emitting API

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Expose API that allows to emit type declaration and field/variable definition
(if optional field name is specified) in valid C syntax for any provided BTF
type. This is going to be used by bpftool when emitting data section layout as
a struct. As part of making this API useful in a stand-alone fashion, move
initialization of some of the internal btf_dump state to earlier phase.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191214014341.3442258-8-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2019-12-13 17:43:31 -08:00 committed by Alexei Starovoitov
parent 3d208f4ca1
commit 9f81654eeb
3 changed files with 65 additions and 26 deletions
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22
tools/lib/bpf/btf.h
View File

@ -126,6 +126,28 @@ LIBBPF_API void btf_dump__free(struct btf_dump *d);
LIBBPF_API int btf_dump__dump_type(struct btf_dump *d, __u32 id);
struct btf_dump_emit_type_decl_opts {
/* size of this struct, for forward/backward compatiblity */
size_t sz;
/* optional field name for type declaration, e.g.:
* - struct my_struct <FNAME>
* - void (*<FNAME>)(int)
* - char (*<FNAME>)[123]
*/
const char *field_name;
/* extra indentation level (in number of tabs) to emit for multi-line
* type declarations (e.g., anonymous struct); applies for lines
* starting from the second one (first line is assumed to have
* necessary indentation already
*/
int indent_level;
};
#define btf_dump_emit_type_decl_opts__last_field indent_level
LIBBPF_API int
btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
const struct btf_dump_emit_type_decl_opts *opts);
/*
* A set of helpers for easier BTF types handling
*/

68
tools/lib/bpf/btf_dump.c
View File

@ -116,6 +116,8 @@ static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...)
va_end(args);
}
static int btf_dump_mark_referenced(struct btf_dump *d);
struct btf_dump *btf_dump__new(const struct btf *btf,
const struct btf_ext *btf_ext,
const struct btf_dump_opts *opts,
@ -137,18 +139,39 @@ struct btf_dump *btf_dump__new(const struct btf *btf,
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);
goto err;
}
d->type_states = calloc(1 + btf__get_nr_types(d->btf),
sizeof(d->type_states[0]));
if (!d->type_states) {
err = -ENOMEM;
goto err;
}
d->cached_names = calloc(1 + btf__get_nr_types(d->btf),
sizeof(d->cached_names[0]));
if (!d->cached_names) {
err = -ENOMEM;
goto err;
}
/* 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)
goto err;
return d;
err:
btf_dump__free(d);
return ERR_PTR(err);
}
void btf_dump__free(struct btf_dump *d)
@ -175,7 +198,6 @@ void btf_dump__free(struct btf_dump *d)
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);
@ -202,27 +224,6 @@ int btf_dump__dump_type(struct btf_dump *d, __u32 id)
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)
@ -1016,6 +1017,21 @@ static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id)
* of a stack frame. Some care is required to "pop" stack frames after
* processing type declaration chain.
*/
int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
const struct btf_dump_emit_type_decl_opts *opts)
{
const char *fname;
int lvl;
if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts))
return -EINVAL;
fname = OPTS_GET(opts, field_name, NULL);
lvl = OPTS_GET(opts, indent_level, 0);
btf_dump_emit_type_decl(d, id, fname, lvl);
return 0;
}
static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
const char *fname, int lvl)
{

1
tools/lib/bpf/libbpf.map
View File

@ -211,6 +211,7 @@ LIBBPF_0.0.6 {
LIBBPF_0.0.7 {
global:
btf_dump__emit_type_decl;
bpf_program__attach;
btf__align_of;
} LIBBPF_0.0.6;