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

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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: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191226210253.3132060-1-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2019-12-26 13:02:53 -08:00 committed by Daniel Borkmann
parent 1162f84403
commit 7c8dce4b16
3 changed files with 16 additions and 6 deletions
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10
tools/bpf/bpftool/gen.c
View File

@ -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);

2
tools/testing/selftests/bpf/Makefile
View File

@ -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 $@

10
tools/testing/selftests/bpf/test_cpp.cpp
View File

@ -1,12 +1,16 @@
/* 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;
}