[RESEND PATCH bpf-next v4 2/9] libbpf: Add support for extended bpf syscall
From: Leon Hwang <hidden>
Date: 2026-01-06 17:21:08
Also in:
bpf, linux-kselftest, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [library] (libbpf), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
To support the extended BPF syscall introduced in the previous commit, introduce the following internal APIs: * 'sys_bpf_ext()' * 'sys_bpf_ext_fd()' They wrap the raw 'syscall()' interface to support passing extended attributes. * 'probe_sys_bpf_ext()' Check whether current kernel supports the extended attributes. Signed-off-by: Leon Hwang <redacted> --- tools/lib/bpf/bpf.c | 34 +++++++++++++++++++++++++++++++++ tools/lib/bpf/features.c | 8 ++++++++ tools/lib/bpf/libbpf_internal.h | 3 +++ 3 files changed, 45 insertions(+)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 21b57a629916..689ade4a822b 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c@@ -69,6 +69,40 @@ static inline __u64 ptr_to_u64(const void *ptr) return (__u64) (unsigned long) ptr; } +static inline int sys_bpf_ext(enum bpf_cmd cmd, union bpf_attr *attr, + unsigned int size, + struct bpf_common_attr *common_attrs, + unsigned int size_common) +{ + cmd = common_attrs ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS); + return syscall(__NR_bpf, cmd, attr, size, common_attrs, size_common); +} + +static inline int sys_bpf_ext_fd(enum bpf_cmd cmd, union bpf_attr *attr, + unsigned int size, + struct bpf_common_attr *common_attrs, + unsigned int size_common) +{ + int fd; + + fd = sys_bpf_ext(cmd, attr, size, common_attrs, size_common); + return ensure_good_fd(fd); +} + +int probe_sys_bpf_ext(void) +{ + const size_t attr_sz = offsetofend(union bpf_attr, prog_token_fd); + union bpf_attr attr; + int fd; + + memset(&attr, 0, attr_sz); + fd = syscall(__NR_bpf, BPF_PROG_LOAD | BPF_COMMON_ATTRS, &attr, attr_sz, NULL, + sizeof(struct bpf_common_attr)); + if (fd >= 0) + close(fd); + return errno == EFAULT; +} + static inline int sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr, unsigned int size) {
diff --git a/tools/lib/bpf/features.c b/tools/lib/bpf/features.c
index b842b83e2480..d786a815f1ae 100644
--- a/tools/lib/bpf/features.c
+++ b/tools/lib/bpf/features.c@@ -506,6 +506,11 @@ static int probe_kern_arg_ctx_tag(int token_fd) return probe_fd(prog_fd); } +static int probe_kern_extended_syscall(int token_fd) +{ + return probe_sys_bpf_ext(); +} + typedef int (*feature_probe_fn)(int /* token_fd */); static struct kern_feature_cache feature_cache;
@@ -581,6 +586,9 @@ static struct kern_feature_desc { [FEAT_BTF_QMARK_DATASEC] = { "BTF DATASEC names starting from '?'", probe_kern_btf_qmark_datasec, }, + [FEAT_EXTENDED_SYSCALL] = { + "Kernel supports extended syscall", probe_kern_extended_syscall, + }, }; bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id)
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index fc59b21b51b5..e2a6ef4b45ae 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h@@ -392,6 +392,8 @@ enum kern_feature_id { FEAT_ARG_CTX_TAG, /* Kernel supports '?' at the front of datasec names */ FEAT_BTF_QMARK_DATASEC, + /* Kernel supports extended syscall */ + FEAT_EXTENDED_SYSCALL, __FEAT_CNT, };
@@ -757,4 +759,5 @@ int probe_fd(int fd); #define SHA256_DWORD_SIZE SHA256_DIGEST_LENGTH / sizeof(__u64) void libbpf_sha256(const void *data, size_t len, __u8 out[SHA256_DIGEST_LENGTH]); +int probe_sys_bpf_ext(void); #endif /* __LIBBPF_LIBBPF_INTERNAL_H */
--
2.52.0