From: Eduard Zingerman <eddyz87@gmail.com>
To: bpf@vger.kernel.org, ast@kernel.org
Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev,
kernel-team@fb.com, yonghong.song@linux.dev,
jose.marchesi@oracle.com, alan.maguire@oracle.com,
Eduard Zingerman <eddyz87@gmail.com>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>
Subject: [PATCH bpf-next 2/3] libbpf: API to access btf_dump emit queue and print single type
Date: Thu, 16 May 2024 16:04:42 -0700 [thread overview]
Message-ID: <20240516230443.3436233-3-eddyz87@gmail.com> (raw)
In-Reply-To: <20240516230443.3436233-1-eddyz87@gmail.com>
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(-)
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 8e6880d91c84..81d70ac35562 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -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;
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 1d0ec57d01a9..cb233f891582 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -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;
}
}
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index c1ce8aa3520b..137e4cbaa7a7 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -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;
--
2.34.1
next prev parent reply other threads:[~2024-05-16 23:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-16 23:04 [PATCH bpf-next 0/3] API to access btf_dump emit queue and print single type Eduard Zingerman
2024-05-16 23:04 ` [PATCH bpf-next 1/3] libbpf: put forward declarations to btf_dump->emit_queue Eduard Zingerman
2024-05-16 23:04 ` Eduard Zingerman [this message]
2024-05-16 23:04 ` [PATCH bpf-next 3/3] selftests/bpf: tests for btf_dump emit queue API Eduard Zingerman
2024-05-17 0:02 ` [PATCH bpf-next 0/3] API to access btf_dump emit queue and print single type Eduard Zingerman
2024-05-17 2:03 ` Eduard Zingerman
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