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bpftool: Cast pointers for shadow types explicitly.

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According to a report, skeletons fail to assign shadow pointers when being
compiled with C++ programs. Unlike C doing implicit casting for void
pointers, C++ requires an explicit casting.

To support C++, we do explicit casting for each shadow pointer.

Also add struct_ops_module.skel.h to test_cpp to validate C++
compilation as part of BPF selftests.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20240312013726.1780720-1-thinker.li@gmail.com
This commit is contained in:
Kui-Feng Lee 2024-03-11 18:37:26 -07:00 committed by Andrii Nakryiko
parent 9187210eee
commit c2a0257c1e
2 changed files with 7 additions and 1 deletions
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3
tools/bpf/bpftool/gen.c
View file

@ -1131,7 +1131,8 @@ static void gen_st_ops_shadow_init(struct btf *btf, struct bpf_object *obj)
continue;
codegen("\
\n\
obj->struct_ops.%1$s = bpf_map__initial_value(obj->maps.%1$s, NULL);\n\
obj->struct_ops.%1$s = (typeof(obj->struct_ops.%1$s))\n\
bpf_map__initial_value(obj->maps.%1$s, NULL);\n\
\n\
", ident);
}

5
tools/testing/selftests/bpf/test_cpp.cpp
View file

@ -7,6 +7,7 @@
#include <bpf/bpf.h>
#include <bpf/btf.h>
#include "test_core_extern.skel.h"
#include "struct_ops_module.skel.h"
template <typename T>
class Skeleton {
@ -98,6 +99,7 @@ int main(int argc, char *argv[])
{
struct btf_dump_opts opts = { };
struct test_core_extern *skel;
struct struct_ops_module *skel2;
struct btf *btf;
int fd;
@ -118,6 +120,9 @@ int main(int argc, char *argv[])
skel = test_core_extern__open_and_load();
test_core_extern__destroy(skel);
skel2 = struct_ops_module__open_and_load();
struct_ops_module__destroy(skel2);
fd = bpf_enable_stats(BPF_STATS_RUN_TIME);
if (fd < 0)
std::cout << "FAILED to enable stats: " << fd << std::endl;