From 1d0dd6ea2e38c18e1b31a8c3c59b6bdfe4f4efde Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 13 Dec 2023 11:08:38 -0800 Subject: libbpf: wire up BPF token support at BPF object level Add BPF token support to BPF object-level functionality. BPF token is supported by BPF object logic either as an explicitly provided BPF token from outside (through BPF FS path or explicit BPF token FD), or implicitly (unless prevented through bpf_object_open_opts). Implicit mode is assumed to be the most common one for user namespaced unprivileged workloads. The assumption is that privileged container manager sets up default BPF FS mount point at /sys/fs/bpf with BPF token delegation options (delegate_{cmds,maps,progs,attachs} mount options). BPF object during loading will attempt to create BPF token from /sys/fs/bpf location, and pass it for all relevant operations (currently, map creation, BTF load, and program load). In this implicit mode, if BPF token creation fails due to whatever reason (BPF FS is not mounted, or kernel doesn't support BPF token, etc), this is not considered an error. BPF object loading sequence will proceed with no BPF token. In explicit BPF token mode, user provides explicitly either custom BPF FS mount point path or creates BPF token on their own and just passes token FD directly. In such case, BPF object will either dup() token FD (to not require caller to hold onto it for entire duration of BPF object lifetime) or will attempt to create BPF token from provided BPF FS location. If BPF token creation fails, that is considered a critical error and BPF object load fails with an error. Libbpf provides a way to disable implicit BPF token creation, if it causes any troubles (BPF token is designed to be completely optional and shouldn't cause any problems even if provided, but in the world of BPF LSM, custom security logic can be installed that might change outcome dependin on the presence of BPF token). To disable libbpf's default BPF token creation behavior user should provide either invalid BPF token FD (negative), or empty bpf_token_path option. BPF token presence can influence libbpf's feature probing, so if BPF object has associated BPF token, feature probing is instructed to use BPF object-specific feature detection cache and token FD. Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20231213190842.3844987-7-andrii@kernel.org Signed-off-by: Alexei Starovoitov --- tools/lib/bpf/btf.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'tools/lib/bpf/btf.c') diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index ee95fd379d4d..63033c334320 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -1317,7 +1317,9 @@ struct btf *btf__parse_split(const char *path, struct btf *base_btf) static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endian); -int btf_load_into_kernel(struct btf *btf, char *log_buf, size_t log_sz, __u32 log_level) +int btf_load_into_kernel(struct btf *btf, + char *log_buf, size_t log_sz, __u32 log_level, + int token_fd) { LIBBPF_OPTS(bpf_btf_load_opts, opts); __u32 buf_sz = 0, raw_size; @@ -1367,6 +1369,7 @@ retry_load: opts.log_level = log_level; } + opts.token_fd = token_fd; btf->fd = bpf_btf_load(raw_data, raw_size, &opts); if (btf->fd < 0) { /* time to turn on verbose mode and try again */ @@ -1394,7 +1397,7 @@ done: int btf__load_into_kernel(struct btf *btf) { - return btf_load_into_kernel(btf, NULL, 0, 0); + return btf_load_into_kernel(btf, NULL, 0, 0, 0); } int btf__fd(const struct btf *btf) -- cgit