Merge branch 'support-freplace-prog-from-user-namespace'

Mykyta Yatsenko says:

====================
Support freplace prog from user namespace

From: Mykyta Yatsenko <yatsenko@meta.com>

Freplace programs can't be loaded from user namespace, as
bpf_program__set_attach_target() requires searching for target prog BTF,
which is locked under CAP_SYS_ADMIN.
This patch set enables this use case by:
1. Relaxing capable check in bpf's BPF_BTF_GET_FD_BY_ID, check for CAP_BPF
instead of CAP_SYS_ADMIN, support BPF token in attr argument.
2. Pass BPF token around libbpf from bpf_program__set_attach_target() to
bpf syscall where capable check is.
3. Validate positive/negative scenarios in selftests

This patch set is enabled by the recent libbpf change[1], that
introduced bpf_object__prepare() API. Calling bpf_object__prepare() for
freplace program before bpf_program__set_attach_target() initializes BPF
token, which is then passed to bpf syscall by libbpf.

[1] https://lore.kernel.org/all/20250303135752.158343-1-mykyta.yatsenko5@gmail.com/
====================

Link: https://patch.msgid.link/20250317174039.161275-1-mykyta.yatsenko5@gmail.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 13 insertions, 2 deletions

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index eea99c766a20..38bc6b14b066 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1619,12 +1619,18 @@ exit_free:
 	return btf;
 }
 
-struct btf *btf__load_from_kernel_by_id_split(__u32 id, struct btf *base_btf)
+struct btf *btf_load_from_kernel(__u32 id, struct btf *base_btf, int token_fd)
 {
 	struct btf *btf;
 	int btf_fd;
+	LIBBPF_OPTS(bpf_get_fd_by_id_opts, opts);
+
+	if (token_fd) {
+		opts.open_flags |= BPF_F_TOKEN_FD;
+		opts.token_fd = token_fd;
+	}
 
-	btf_fd = bpf_btf_get_fd_by_id(id);
+	btf_fd = bpf_btf_get_fd_by_id_opts(id, &opts);
 	if (btf_fd < 0)
 		return libbpf_err_ptr(-errno);
 
@@ -1634,6 +1640,11 @@ struct btf *btf__load_from_kernel_by_id_split(__u32 id, struct btf *base_btf)
 	return libbpf_ptr(btf);
 }
 
+struct btf *btf__load_from_kernel_by_id_split(__u32 id, struct btf *base_btf)
+{
+	return btf_load_from_kernel(id, base_btf, 0);
+}
+
 struct btf *btf__load_from_kernel_by_id(__u32 id)
 {
 	return btf__load_from_kernel_by_id_split(id, NULL);