Commit d2b94f33 authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

Merge branch 'Make BPF skeleton easier to use from C++ code' 



Andrii Nakryiko says:

====================

Add minimal C++-specific additions to BPF skeleton codegen to facilitate
easier use of C skeletons in C++ applications. These additions don't add any
extra ongoing maintenance and allows C++ users to fit pure C skeleton better
into their C++ code base. All that without the need to design, implement and
support a separate C++ BPF skeleton implementation.

v1->v2:
  - use default argument values in T::open() (Alexei).
====================

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parents d3b0b800 189e0eca

tools/bpf/bpftool/gen.c

+22 −2
Original line number Diff line number Diff line
@@ -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);

tools/testing/selftests/bpf/test_cpp.cpp

+85 −2
Original line number Diff line number Diff line
@@ -5,18 +5,100 @@ 
#include <bpf/btf.h>

#include "test_core_extern.skel.h"



/* do nothing, just make sure we can link successfully */

template <typename T>

class Skeleton {

private:

	T *skel;

public:

	Skeleton(): skel(nullptr) { }



	~Skeleton() { if (skel) T::destroy(skel); }



	int open(const struct bpf_object_open_opts *opts = nullptr)

	{

		int err;



		if (skel)

			return -EBUSY;



		skel = T::open(opts);

		err = libbpf_get_error(skel);

		if (err) {

			skel = nullptr;

			return err;

		}



		return 0;

	}



	int load() { return T::load(skel); }



	int attach() { return T::attach(skel); }



	void detach() { return T::detach(skel); }



	const T* operator->() const { return skel; }



	T* operator->() { return skel; }



	const T *get() const { return skel; }

};



static void dump_printf(void *ctx, const char *fmt, va_list args)

{

}



static void try_skeleton_template()

{

	Skeleton<test_core_extern> skel;

	std::string prog_name;

	int err;

	LIBBPF_OPTS(bpf_object_open_opts, opts);



	err = skel.open(&opts);

	if (err) {

		fprintf(stderr, "Skeleton open failed: %d\n", err);

		return;

	}



	skel->data->kern_ver = 123;

	skel->data->int_val = skel->data->ushort_val;



	err = skel.load();

	if (err) {

		fprintf(stderr, "Skeleton load failed: %d\n", err);

		return;

	}



	if (!skel->kconfig->CONFIG_BPF_SYSCALL)

		fprintf(stderr, "Seems like CONFIG_BPF_SYSCALL isn't set?!\n");



	err = skel.attach();

	if (err) {

		fprintf(stderr, "Skeleton attach failed: %d\n", err);

		return;

	}



	prog_name = bpf_program__name(skel->progs.handle_sys_enter);

	if (prog_name != "handle_sys_enter")

		fprintf(stderr, "Unexpected program name: %s\n", prog_name.c_str());



	bpf_link__destroy(skel->links.handle_sys_enter);

	skel->links.handle_sys_enter = bpf_program__attach(skel->progs.handle_sys_enter);



	skel.detach();



	/* destructor will destory underlying skeleton */

}



int main(int argc, char *argv[])

{

	struct btf_dump_opts opts = { };

	struct test_core_extern *skel;

	struct btf *btf;



	try_skeleton_template();



	/* libbpf.h */

	libbpf_set_print(NULL);
@@ -25,6 +107,7 @@ int main(int argc, char *argv[]) 


	/* btf.h */

	btf = btf__new(NULL, 0);

	if (!libbpf_get_error(btf))

		btf_dump__new(btf, dump_printf, nullptr, &opts);



	/* BPF skeleton */