From 81372e121802fd57892a0b44d93cc747d9568627 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Tue, 7 Jul 2020 18:53:14 -0700 Subject: [PATCH] libbpf: Add btf__set_fd() for more control over loaded BTF FD Add setter for BTF FD to allow application more fine-grained control in more advanced scenarios. Storing BTF FD inside `struct btf` provides little benefit and probably would be better done differently (e.g., btf__load() could just return FD on success), but we are stuck with this due to backwards compatibility. The main problem is that it's impossible to load BTF and than free user-space memory, but keep FD intact, because `struct btf` assumes ownership of that FD upon successful load and will attempt to close it during btf__free(). To allow callers (e.g., libbpf itself for BTF sanitization) to have more control over this, add btf__set_fd() to allow to reset FD arbitrarily, if necessary. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20200708015318.3827358-3-andriin@fb.com --- tools/lib/bpf/btf.c | 7 ++++++- tools/lib/bpf/btf.h | 1 + tools/lib/bpf/libbpf.map | 1 + 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index bfef3d606b54e..c8861c9e3635f 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -389,7 +389,7 @@ void btf__free(struct btf *btf) if (!btf) return; - if (btf->fd != -1) + if (btf->fd >= 0) close(btf->fd); free(btf->data); @@ -700,6 +700,11 @@ int btf__fd(const struct btf *btf) return btf->fd; } +void btf__set_fd(struct btf *btf, int fd) +{ + btf->fd = fd; +} + const void *btf__get_raw_data(const struct btf *btf, __u32 *size) { *size = btf->data_size; diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index 06cd1731c1547..173eff23c4721 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -79,6 +79,7 @@ LIBBPF_API __s64 btf__resolve_size(const struct btf *btf, __u32 type_id); LIBBPF_API int btf__resolve_type(const struct btf *btf, __u32 type_id); LIBBPF_API int btf__align_of(const struct btf *btf, __u32 id); LIBBPF_API int btf__fd(const struct btf *btf); +LIBBPF_API void btf__set_fd(struct btf *btf, int fd); LIBBPF_API const void *btf__get_raw_data(const struct btf *btf, __u32 *size); LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset); LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 6544d2cd1ed63..c5d5c7664c3b7 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -288,4 +288,5 @@ LIBBPF_0.1.0 { bpf_map__value_size; bpf_program__autoload; bpf_program__set_autoload; + btf__set_fd; } LIBBPF_0.0.9;