Add C++-specific static methods for code-generated BPF skeleton for each
skeleton operation: open, open_opts, open_and_load, load, attach,
detach, destroy, and elf_bytes. This is to facilitate easier C++
templating on top of pure C BPF skeleton.
In C, open/load/destroy/etc "methods" are of the form
<skeleton_name>__<method>() to avoid name collision with similar
"methods" of other skeletons withint the same application. This works
well, but is very inconvenient for C++ applications that would like to
write generic (templated) wrappers around BPF skeleton to fit in with
C++ code base and take advantage of destructors and other convenient C++
constructs.
This patch makes it easier to build such generic templated wrappers by
additionally defining C++ static methods for skeleton's struct with
fixed names. This allows to refer to, say, open method as `T::open()`
instead of having to somehow generate `T__open()` function call.
Next patch adds an example template to test_cpp selftest to demonstrate
how it's possible to have all the operations wrapped in a generic
Skeleton<my_skeleton> type without explicitly passing function references.
An example of generated declaration section without %1$s placeholders:
#ifdef __cplusplus
static struct test_attach_probe *open(const struct bpf_object_open_opts *opts = nullptr);
static struct test_attach_probe *open_and_load();
static int load(struct test_attach_probe *skel);
static int attach(struct test_attach_probe *skel);
static void detach(struct test_attach_probe *skel);
static void destroy(struct test_attach_probe *skel);
static const void *elf_bytes(size_t *sz);
#endif /* __cplusplus */
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
tools/bpf/bpftool/gen.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 6f2e20be0c62..022f30490567 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -831,6 +831,16 @@ static int do_skeleton(int argc, char **argv)
codegen("\
\n\
+ \n\
+ #ifdef __cplusplus \n\
+ static struct %1$s *open(const struct bpf_object_open_opts *opts = nullptr);\n\
+ static struct %1$s *open_and_load(); \n\
+ static int load(struct %1$s *skel); \n\
+ static int attach(struct %1$s *skel); \n\
+ static void detach(struct %1$s *skel); \n\
+ static void destroy(struct %1$s *skel); \n\
+ static const void *elf_bytes(size_t *sz); \n\
+ #endif /* __cplusplus */ \n\
}; \n\
\n\
static void \n\
@@ -1025,9 +1035,19 @@ static int do_skeleton(int argc, char **argv)
\"; \n\
} \n\
\n\
- #endif /* %s */ \n\
+ #ifdef __cplusplus \n\
+ struct %1$s *%1$s::open(const struct bpf_object_open_opts *opts) { return %1$s__open_opts(opts); }\n\
+ struct %1$s *%1$s::open_and_load() { return %1$s__open_and_load(); } \n\
+ int %1$s::load(struct %1$s *skel) { return %1$s__load(skel); } \n\
+ int %1$s::attach(struct %1$s *skel) { return %1$s__attach(skel); } \n\
+ void %1$s::detach(struct %1$s *skel) { %1$s__detach(skel); } \n\
+ void %1$s::destroy(struct %1$s *skel) { %1$s__destroy(skel); } \n\
+ const void *%1$s::elf_bytes(size_t *sz) { return %1$s__elf_bytes(sz); } \n\
+ #endif /* __cplusplus */ \n\
+ \n\
+ #endif /* %2$s */ \n\
",
- header_guard);
+ obj_name, header_guard);
err = 0;
out:
bpf_object__close(obj);
--
2.30.2
