@@ -249,6 +249,39 @@ LIBBPF_API void btf_dump__free(struct btf_dump *d);
LIBBPF_API int btf_dump__dump_type(struct btf_dump *d, __u32 id);
+/* Dumps C language definition or forward declaration for type **id**:
+ * - returns 1 if type is printable;
+ * - returns 0 if type is non-printable.
+ */
+LIBBPF_API int btf_dump__dump_one_type(struct btf_dump *d, __u32 id, bool fwd);
+
+/* **struct btf_dump** tracks a list of types that should be dumped,
+ * these types are sorted in the topological order satisfying C language semantics:
+ * - if type A includes type B (e.g. A is a struct with a field of type B),
+ * then B comes before A;
+ * - if type A references type B via a pointer
+ * (e.g. A is a struct with a field of type pointer to B),
+ * then B's forward declaration comes before A.
+ *
+ * **struct btf_dump_emit_queue_item** represents a single entry of the emit queue.
+ */
+struct btf_dump_emit_queue_item {
+ __u32 id:31;
+ __u32 fwd:1;
+};
+
+/* Adds type **id** and it's dependencies to the emit queue. */
+LIBBPF_API int btf_dump__order_type(struct btf_dump *d, __u32 id);
+
+/* Provides access to currently accumulated emit queue,
+ * returned pointer is owned by **struct btf_dump** and should not be
+ * freed explicitly.
+ */
+LIBBPF_API struct btf_dump_emit_queue_item *btf_dump__emit_queue(struct btf_dump *d);
+
+/* Returns the size of currently accumulated emit queue */
+LIBBPF_API __u32 btf_dump__emit_queue_cnt(struct btf_dump *d);
+
struct btf_dump_emit_type_decl_opts {
/* size of this struct, for forward/backward compatiblity */
size_t sz;
@@ -85,10 +85,7 @@ struct btf_dump {
size_t cached_names_cap;
/* topo-sorted list of dependent type definitions */
- struct {
- __u32 id:31;
- __u32 fwd:1;
- } *emit_queue;
+ struct btf_dump_emit_queue_item *emit_queue;
int emit_queue_cap;
int emit_queue_cnt;
@@ -250,7 +247,6 @@ void btf_dump__free(struct btf_dump *d)
}
static int btf_dump_order_type(struct btf_dump *d, __u32 id, __u32 cont_id, bool through_ptr);
-static void btf_dump_emit_type(struct btf_dump *d, __u32 id, bool fwd);
/*
* Dump BTF type in a compilable C syntax, including all the necessary
@@ -296,12 +292,32 @@ int btf_dump__dump_type(struct btf_dump *d, __u32 id)
break;
};
- for (i = 0; i < d->emit_queue_cnt; i++)
- btf_dump_emit_type(d, d->emit_queue[i].id, d->emit_queue[i].fwd);
+ for (i = 0; i < d->emit_queue_cnt; i++) {
+ err = btf_dump__dump_one_type(d, d->emit_queue[i].id, d->emit_queue[i].fwd);
+ if (err < 0)
+ return libbpf_err(err);
+ if (err > 0)
+ btf_dump_printf(d, ";\n\n");
+ }
return 0;
}
+int btf_dump__order_type(struct btf_dump *d, __u32 id)
+{
+ return btf_dump_order_type(d, id, id, false);
+}
+
+struct btf_dump_emit_queue_item *btf_dump__emit_queue(struct btf_dump *d)
+{
+ return d->emit_queue;
+}
+
+__u32 btf_dump__emit_queue_cnt(struct btf_dump *d)
+{
+ return d->emit_queue_cnt;
+}
+
/*
* 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
@@ -382,7 +398,7 @@ static int btf_dump_mark_referenced(struct btf_dump *d)
static int __btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id, bool fwd)
{
- typeof(d->emit_queue[0]) *new_queue = NULL;
+ struct btf_dump_emit_queue_item *new_queue = NULL;
size_t new_cap;
if (d->emit_queue_cnt >= d->emit_queue_cap) {
@@ -724,7 +740,7 @@ static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
* 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, bool fwd)
+int btf_dump__dump_one_type(struct btf_dump *d, __u32 id, bool fwd)
{
const struct btf_type *t;
__u16 kind;
@@ -737,8 +753,7 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, bool fwd)
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
btf_dump_emit_struct_fwd(d, id, t);
- btf_dump_printf(d, ";\n\n");
- break;
+ return 1;
case BTF_KIND_TYPEDEF:
/*
* for typedef fwd_emitted means typedef definition
@@ -746,29 +761,23 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, bool fwd)
* references through pointer only, not for embedding
*/
btf_dump_emit_typedef_def(d, id, t, 0);
- btf_dump_printf(d, ";\n\n");
- break;
+ return 1;
default:
- break;
+ return 0;
}
-
- return;
}
switch (kind) {
case BTF_KIND_INT:
/* Emit type alias definitions if necessary */
- btf_dump_emit_missing_aliases(d, id, false);
- break;
+ return btf_dump_emit_missing_aliases(d, id, false);
case BTF_KIND_ENUM:
case BTF_KIND_ENUM64:
btf_dump_emit_enum_def(d, id, t, 0);
- btf_dump_printf(d, ";\n\n");
- break;
+ return 1;
case BTF_KIND_FWD:
btf_dump_emit_fwd_def(d, id, t);
- btf_dump_printf(d, ";\n\n");
- break;
+ return 1;
case BTF_KIND_TYPEDEF:
/*
* typedef can server as both definition and forward
@@ -778,15 +787,13 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, bool fwd)
* emit typedef as a forward declaration
*/
btf_dump_emit_typedef_def(d, id, t, 0);
- btf_dump_printf(d, ";\n\n");
- break;
+ return 1;
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
btf_dump_emit_struct_def(d, id, t, 0);
- btf_dump_printf(d, ";\n\n");
- break;
+ return 1;
default:
- break;
+ return 0;
}
}
@@ -422,4 +422,8 @@ LIBBPF_1.5.0 {
bpf_program__attach_sockmap;
ring__consume_n;
ring_buffer__consume_n;
+ btf_dump__emit_queue;
+ btf_dump__emit_queue_cnt;
+ btf_dump__order_type;
+ btf_dump__dump_one_type;
} LIBBPF_1.4.0;
Add several API functions to allow more flexibility with btf dump: - int btf_dump__order_type(struct btf_dump *d, __u32 id); adds a type and all it's dependencies to the emit queue in topological order; - struct btf_dump_emit_queue_item *btf_dump__emit_queue(struct btf_dump *d); __u32 btf_dump__emit_queue_cnt(struct btf_dump *d); provide access to the emit queue owned by btf_dump object; - int btf_dump__dump_one_type(struct btf_dump *d, __u32 id, bool fwd); prints a given type in C format (skipping any dependencies). This API should allow to do the following on the libbpf client side: - filter printed types using arbitrary criteria; - add arbitrary type attributes or pre-processor statements for selected types. This is a follow-up to the following discussion: https://lore.kernel.org/bpf/20240503111836.25275-1-jose.marchesi@oracle.com/ Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> --- tools/lib/bpf/btf.h | 33 ++++++++++++++++++++++ tools/lib/bpf/btf_dump.c | 61 ++++++++++++++++++++++------------------ tools/lib/bpf/libbpf.map | 4 +++ 3 files changed, 71 insertions(+), 27 deletions(-)