[bpf-next,2/3] libbpf: pass BPF token from find_prog_btf_id to BPF_BTF_GET_FD_BY_ID

Commit Message

Mykyta Yatsenko March 4, 2025, 9:14 p.m. UTC

From: Mykyta Yatsenko <[e-mail]>

Pass BPF token from bpf_program__set_attach_target to
BPF_BTF_GET_FD_BY_ID bpf command.
When freplace program attaches to target program, it needs to look up
for BTF of the target, this may require BPF token, if, for example,
running from user namespace.

Signed-off-by: Mykyta Yatsenko <[e-mail]>
---
 tools/include/uapi/linux/bpf.h  |  1 +
 tools/lib/bpf/bpf.c             |  3 ++-
 tools/lib/bpf/bpf.h             |  4 +++-
 tools/lib/bpf/btf.c             | 10 ++++++++--
 tools/lib/bpf/libbpf.c          | 10 +++++-----
 tools/lib/bpf/libbpf_internal.h |  1 +
 6 files changed, 20 insertions(+), 9 deletions(-)

Comments

Andrii Nakryiko March 4, 2025, 10:21 p.m. UTC | #1

On Tue, Mar 4, 2025 at 1:15 PM Mykyta Yatsenko
<[e-mail]> wrote:
>
> From: Mykyta Yatsenko <[e-mail]>
>
> Pass BPF token from bpf_program__set_attach_target to
> BPF_BTF_GET_FD_BY_ID bpf command.
> When freplace program attaches to target program, it needs to look up
> for BTF of the target, this may require BPF token, if, for example,
> running from user namespace.
>
> Signed-off-by: Mykyta Yatsenko <[e-mail]>
> ---
>  tools/include/uapi/linux/bpf.h  |  1 +
>  tools/lib/bpf/bpf.c             |  3 ++-
>  tools/lib/bpf/bpf.h             |  4 +++-
>  tools/lib/bpf/btf.c             | 10 ++++++++--
>  tools/lib/bpf/libbpf.c          | 10 +++++-----
>  tools/lib/bpf/libbpf_internal.h |  1 +
>  6 files changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index bb37897c0393..73c23daacabf 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h

let's update tools/include/uapi/linux/bpf.h in the same patch as
include/uapi/linux/bpf.h itself

> @@ -1652,6 +1652,7 @@ union bpf_attr {
>                 };
>                 __u32           next_id;
>                 __u32           open_flags;
> +               __s32           token_fd;
>         };
>
>         struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 359f73ead613..783274172e56 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -1097,7 +1097,7 @@ int bpf_map_get_fd_by_id(__u32 id)
>  int bpf_btf_get_fd_by_id_opts(__u32 id,
>                               const struct bpf_get_fd_by_id_opts *opts)
>  {
> -       const size_t attr_sz = offsetofend(union bpf_attr, open_flags);
> +       const size_t attr_sz = offsetofend(union bpf_attr, token_fd);
>         union bpf_attr attr;
>         int fd;
>
> @@ -1107,6 +1107,7 @@ int bpf_btf_get_fd_by_id_opts(__u32 id,
>         memset(&attr, 0, attr_sz);
>         attr.btf_id = id;
>         attr.open_flags = OPTS_GET(opts, open_flags, 0);
> +       attr.token_fd = OPTS_GET(opts, token_fd, 0);
>
>         fd = sys_bpf_fd(BPF_BTF_GET_FD_BY_ID, &attr, attr_sz);
>         return libbpf_err_errno(fd);
> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> index 435da95d2058..544215d7137c 100644
> --- a/tools/lib/bpf/bpf.h
> +++ b/tools/lib/bpf/bpf.h
> @@ -487,9 +487,11 @@ LIBBPF_API int bpf_link_get_next_id(__u32 start_id, __u32 *next_id);
>  struct bpf_get_fd_by_id_opts {
>         size_t sz; /* size of this struct for forward/backward compatibility */
>         __u32 open_flags; /* permissions requested for the operation on fd */
> +       __u32 token_fd;
>         size_t :0;
>  };
> -#define bpf_get_fd_by_id_opts__last_field open_flags
> +
> +#define bpf_get_fd_by_id_opts__last_field token_fd
>
>  LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
>  LIBBPF_API int bpf_prog_get_fd_by_id_opts(__u32 id,
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index eea99c766a20..251071e1ce1d 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -1619,12 +1619,13 @@ struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf)
>         return btf;
>  }
>
> -struct btf *btf__load_from_kernel_by_id_split(__u32 id, struct btf *base_btf)
> +struct btf *btf_load_from_kernel_by_id_split(__u32 id, struct btf *base_btf, int token_fd)

that's quite a name we now have :) let's call it just "btf_load_from_kernel"

>  {
>         struct btf *btf;
>         int btf_fd;
> +       LIBBPF_OPTS(bpf_get_fd_by_id_opts, 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);
>

[...]

Patch

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index bb37897c0393..73c23daacabf 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1652,6 +1652,7 @@  union bpf_attr {
 		};
 		__u32		next_id;
 		__u32		open_flags;
+		__s32		token_fd;
 	};
 
 	struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 359f73ead613..783274172e56 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -1097,7 +1097,7 @@  int bpf_map_get_fd_by_id(__u32 id)
 int bpf_btf_get_fd_by_id_opts(__u32 id,
 			      const struct bpf_get_fd_by_id_opts *opts)
 {
-	const size_t attr_sz = offsetofend(union bpf_attr, open_flags);
+	const size_t attr_sz = offsetofend(union bpf_attr, token_fd);
 	union bpf_attr attr;
 	int fd;
 
@@ -1107,6 +1107,7 @@  int bpf_btf_get_fd_by_id_opts(__u32 id,
 	memset(&attr, 0, attr_sz);
 	attr.btf_id = id;
 	attr.open_flags = OPTS_GET(opts, open_flags, 0);
+	attr.token_fd = OPTS_GET(opts, token_fd, 0);
 
 	fd = sys_bpf_fd(BPF_BTF_GET_FD_BY_ID, &attr, attr_sz);
 	return libbpf_err_errno(fd);
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 435da95d2058..544215d7137c 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -487,9 +487,11 @@  LIBBPF_API int bpf_link_get_next_id(__u32 start_id, __u32 *next_id);
 struct bpf_get_fd_by_id_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
 	__u32 open_flags; /* permissions requested for the operation on fd */
+	__u32 token_fd;
 	size_t :0;
 };
-#define bpf_get_fd_by_id_opts__last_field open_flags
+
+#define bpf_get_fd_by_id_opts__last_field token_fd
 
 LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_prog_get_fd_by_id_opts(__u32 id,
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index eea99c766a20..251071e1ce1d 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1619,12 +1619,13 @@  struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf)
 	return btf;
 }
 
-struct btf *btf__load_from_kernel_by_id_split(__u32 id, struct btf *base_btf)
+struct btf *btf_load_from_kernel_by_id_split(__u32 id, struct btf *base_btf, int token_fd)
 {
 	struct btf *btf;
 	int btf_fd;
+	LIBBPF_OPTS(bpf_get_fd_by_id_opts, 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 +1635,11 @@  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_by_id_split(id, base_btf, 0);
+}
+
 struct btf *btf__load_from_kernel_by_id(__u32 id)
 {
 	return btf__load_from_kernel_by_id_split(id, NULL);
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8e32286854ef..6b21086156a9 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10024,7 +10024,7 @@  int libbpf_find_vmlinux_btf_id(const char *name,
 	return libbpf_err(err);
 }
 
-static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
+static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd, int token_fd)
 {
 	struct bpf_prog_info info;
 	__u32 info_len = sizeof(info);
@@ -10044,7 +10044,7 @@  static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
 		pr_warn("The target program doesn't have BTF\n");
 		goto out;
 	}
-	btf = btf__load_from_kernel_by_id(info.btf_id);
+	btf = btf_load_from_kernel_by_id_split(info.btf_id, NULL, token_fd);
 	err = libbpf_get_error(btf);
 	if (err) {
 		pr_warn("Failed to get BTF %d of the program: %s\n", info.btf_id, errstr(err));
@@ -10127,7 +10127,7 @@  static int libbpf_find_attach_btf_id(struct bpf_program *prog, const char *attac
 			pr_warn("prog '%s': attach program FD is not set\n", prog->name);
 			return -EINVAL;
 		}
-		err = libbpf_find_prog_btf_id(attach_name, attach_prog_fd);
+		err = libbpf_find_prog_btf_id(attach_name, attach_prog_fd, prog->obj->token_fd);
 		if (err < 0) {
 			pr_warn("prog '%s': failed to find BPF program (FD %d) BTF ID for '%s': %s\n",
 				prog->name, attach_prog_fd, attach_name, errstr(err));
@@ -12923,7 +12923,7 @@  struct bpf_link *bpf_program__attach_freplace(const struct bpf_program *prog,
 	if (target_fd) {
 		LIBBPF_OPTS(bpf_link_create_opts, target_opts);
 
-		btf_id = libbpf_find_prog_btf_id(attach_func_name, target_fd);
+		btf_id = libbpf_find_prog_btf_id(attach_func_name, target_fd, prog->obj->token_fd);
 		if (btf_id < 0)
 			return libbpf_err_ptr(btf_id);
 
@@ -13744,7 +13744,7 @@  int bpf_program__set_attach_target(struct bpf_program *prog,
 
 	if (attach_prog_fd) {
 		btf_id = libbpf_find_prog_btf_id(attach_func_name,
-						 attach_prog_fd);
+						 attach_prog_fd, prog->obj->token_fd);
 		if (btf_id < 0)
 			return libbpf_err(btf_id);
 	} else {
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index de498e2dd6b0..fe99fc85617e 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -409,6 +409,7 @@  int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
 int btf_load_into_kernel(struct btf *btf,
 			 char *log_buf, size_t log_sz, __u32 log_level,
 			 int token_fd);
+struct btf *btf_load_from_kernel_by_id_split(__u32 id, struct btf *base_btf, int token_fd);
 
 struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf);
 void btf_get_kernel_prefix_kind(enum bpf_attach_type attach_type,