On Mon, Mar 11, 2024 at 2:35 AM Menglong Dong dongmenglong.8@bytedance.com wrote:
By default, the kernel btf that we load during loading program will be freed after the programs are loaded in bpf_object_load(). However, we still need to use these btf for tracing of multi-link during attaching. Therefore, we don't free the btfs until the bpf object is closed if any bpf programs of the type multi-link tracing exist.
Meanwhile, introduce the new api bpf_object__free_btf() to manually free the btfs after attaching.
Signed-off-by: Menglong Dong dongmenglong.8@bytedance.com
tools/lib/bpf/libbpf.c | 47 ++++++++++++++++++++++++++++++---------- tools/lib/bpf/libbpf.h | 2 ++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 38 insertions(+), 12 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 567ad367e7aa..fd5428494a7e 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -8267,6 +8267,39 @@ static int bpf_object_prepare_struct_ops(struct bpf_object *obj) return 0; }
+void bpf_object__free_btfs(struct bpf_object *obj) +{
int i;/* clean up module BTFs */for (i = 0; i < obj->btf_module_cnt; i++) {close(obj->btf_modules[i].fd);btf__free(obj->btf_modules[i].btf);free(obj->btf_modules[i].name);}free(obj->btf_modules);obj->btf_modules = NULL;obj->btf_module_cnt = 0;/* clean up vmlinux BTF */btf__free(obj->btf_vmlinux);obj->btf_vmlinux = NULL;+}
+static void bpf_object_early_free_btf(struct bpf_object *obj) +{
struct bpf_program *prog;bpf_object__for_each_program(prog, obj) {if (prog->expected_attach_type == BPF_TRACE_FENTRY_MULTI ||prog->expected_attach_type == BPF_TRACE_FEXIT_MULTI ||prog->expected_attach_type == BPF_MODIFY_RETURN_MULTI)return;}bpf_object__free_btfs(obj);+}
static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const char *target_btf_path) { int err, i; @@ -8307,18 +8340,7 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch /* clean up fd_array */ zfree(&obj->fd_array);
/* clean up module BTFs */for (i = 0; i < obj->btf_module_cnt; i++) {close(obj->btf_modules[i].fd);btf__free(obj->btf_modules[i].btf);free(obj->btf_modules[i].name);}free(obj->btf_modules);/* clean up vmlinux BTF */btf__free(obj->btf_vmlinux);obj->btf_vmlinux = NULL;
bpf_object_early_free_btf(obj); obj->loaded = true; /* doesn't matter if successfully or not */ if (err)@@ -8791,6 +8813,7 @@ void bpf_object__close(struct bpf_object *obj) usdt_manager_free(obj->usdt_man); obj->usdt_man = NULL;
bpf_object__free_btfs(obj); bpf_gen__free(obj->gen_loader); bpf_object__elf_finish(obj); bpf_object_unload(obj);diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 5723cbbfcc41..c41a909ea4c1 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -299,6 +299,8 @@ LIBBPF_API struct bpf_program * bpf_object__find_program_by_name(const struct bpf_object *obj, const char *name);
+LIBBPF_API void bpf_object__free_btfs(struct bpf_object *obj);
It shouldn't be exported. libbpf should clean it up when bpf_object is freed.