Commit 7c8dce4b authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

bpftool: Make skeleton C code compilable with C++ compiler 



When auto-generated BPF skeleton C code is included from C++ application, it
triggers compilation error due to void * being implicitly casted to whatever
target pointer type. This is supported by C, but not C++. To solve this
problem, add explicit casts, where necessary.

To ensure issues like this are captured going forward, add skeleton usage in
test_cpp test.

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191226210253.3132060-1-andriin@fb.com
parent 1162f844

tools/bpf/bpftool/gen.c

+5 −5
Original line number Diff line number Diff line
@@ -397,7 +397,7 @@ static int do_skeleton(int argc, char **argv) 
		{							    \n\

			struct %1$s *obj;				    \n\

									    \n\

			obj = calloc(1, sizeof(*obj));			    \n\

			obj = (typeof(obj))calloc(1, sizeof(*obj));	    \n\

			if (!obj)					    \n\

				return NULL;				    \n\

			if (%1$s__create_skeleton(obj))			    \n\
@@ -461,7 +461,7 @@ static int do_skeleton(int argc, char **argv) 
		{							    \n\

			struct bpf_object_skeleton *s;			    \n\

									    \n\

			s = calloc(1, sizeof(*s));			    \n\

			s = (typeof(s))calloc(1, sizeof(*s));		    \n\

			if (!s)						    \n\

				return -1;				    \n\

			obj->skeleton = s;				    \n\
@@ -479,7 +479,7 @@ static int do_skeleton(int argc, char **argv) 
				/* maps */				    \n\

				s->map_cnt = %zu;			    \n\

				s->map_skel_sz = sizeof(*s->maps);	    \n\

				s->maps = calloc(s->map_cnt, s->map_skel_sz);\n\

				s->maps = (typeof(s->maps))calloc(s->map_cnt, s->map_skel_sz);\n\

				if (!s->maps)				    \n\

					goto err;			    \n\

			",
@@ -515,7 +515,7 @@ static int do_skeleton(int argc, char **argv) 
				/* programs */				    \n\

				s->prog_cnt = %zu;			    \n\

				s->prog_skel_sz = sizeof(*s->progs);	    \n\

				s->progs = calloc(s->prog_cnt, s->prog_skel_sz);\n\

				s->progs = (typeof(s->progs))calloc(s->prog_cnt, s->prog_skel_sz);\n\

				if (!s->progs)				    \n\

					goto err;			    \n\

			",
@@ -538,7 +538,7 @@ static int do_skeleton(int argc, char **argv) 
		\n\

									    \n\

			s->data_sz = %d;				    \n\

			s->data = \"\\					    \n\

			s->data = (void *)\"\\				    \n\

		",

		file_sz);

tools/testing/selftests/bpf/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -371,7 +371,7 @@ $(OUTPUT)/test_verifier: test_verifier.c verifier/tests.h $(BPFOBJ) | $(OUTPUT) 
	$(CC) $(CFLAGS) $(filter %.a %.o %.c,$^) $(LDLIBS) -o $@



# Make sure we are able to include and link libbpf against c++.

$(OUTPUT)/test_cpp: test_cpp.cpp $(BPFOBJ)

$(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)

	$(call msg,        CXX,,$@)

	$(CXX) $(CFLAGS) $^ $(LDLIBS) -o $@

tools/testing/selftests/bpf/test_cpp.cpp

+10 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */

#include <iostream>

#include "libbpf.h"

#include "bpf.h"

#include "btf.h"

#include "test_core_extern.skel.h"



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



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

{

	struct test_core_extern *skel;



	/* libbpf.h */

	libbpf_set_print(NULL);
@@ -16,5 +20,11 @@ int main(int argc, char *argv[]) 
	/* btf.h */

	btf__new(NULL, 0);



	/* BPF skeleton */

	skel = test_core_extern__open_and_load();

	test_core_extern__destroy(skel);



	std::cout << "DONE!" << std::endl;



	return 0;

}

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