[PATCH RESEND bpf-next 11/18] libbpf: add BPF token support to bpf_btf_load() API

From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>
Cc: <linux-security-module@vger.kernel.org>, <keescook@chromium.org>,
	<brauner@kernel.org>, <lennart@poettering.net>,
	<cyphar@cyphar.com>, <luto@kernel.org>
Subject: [PATCH RESEND bpf-next 11/18] libbpf: add BPF token support to bpf_btf_load() API
Date: Fri, 2 Jun 2023 08:00:04 -0700	[thread overview]
Message-ID: <20230602150011.1657856-12-andrii@kernel.org> (raw)
In-Reply-To: <20230602150011.1657856-1-andrii@kernel.org>

Allow user to specify token_fd for bpf_btf_load() API that wraps
kernel's BPF_BTF_LOAD command. This allows loading BTF from unprivileged
process as long as it has BPF token allowing BPF_BTF_LOAD command, which
can be created and delegated by privileged process.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/bpf.c | 4 +++-
 tools/lib/bpf/bpf.h | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 0318538d43eb..193993dbbdc4 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -1098,7 +1098,7 @@ int bpf_raw_tracepoint_open(const char *name, int prog_fd)
 
 int bpf_btf_load(const void *btf_data, size_t btf_size, struct bpf_btf_load_opts *opts)
 {
-	const size_t attr_sz = offsetofend(union bpf_attr, btf_log_true_size);
+	const size_t attr_sz = offsetofend(union bpf_attr, btf_token_fd);
 	union bpf_attr attr;
 	char *log_buf;
 	size_t log_size;
@@ -1123,6 +1123,8 @@ int bpf_btf_load(const void *btf_data, size_t btf_size, struct bpf_btf_load_opts
 
 	attr.btf = ptr_to_u64(btf_data);
 	attr.btf_size = btf_size;
+	attr.btf_token_fd = OPTS_GET(opts, token_fd, 0);
+
 	/* log_level == 0 and log_buf != NULL means "try loading without
 	 * log_buf, but retry with log_buf and log_level=1 on error", which is
 	 * consistent across low-level and high-level BTF and program loading
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 19a43201d1af..3153a9e697e2 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -132,9 +132,10 @@ struct bpf_btf_load_opts {
 	 * If kernel doesn't support this feature, log_size is left unchanged.
 	 */
 	__u32 log_true_size;
+	__u32 token_fd;
 	size_t :0;
 };
-#define bpf_btf_load_opts__last_field log_true_size
+#define bpf_btf_load_opts__last_field token_fd
 
 LIBBPF_API int bpf_btf_load(const void *btf_data, size_t btf_size,
 			    struct bpf_btf_load_opts *opts);
-- 
2.34.1

