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 BPF syscall common attributes.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
tools/lib/bpf/bpf.c | 32 ++++++++++++++++++++++++++++++++
tools/lib/bpf/features.c | 8 ++++++++
tools/lib/bpf/libbpf_internal.h | 3 +++
3 files changed, 43 insertions(+)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 21b57a629916..ed9c6eaeb656 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -69,6 +69,38 @@ 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 *attr_common,
+ unsigned int size_common)
+{
+ cmd = attr_common ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS);
+ return syscall(__NR_bpf, cmd, attr, size, attr_common, size_common);
+}
+
+static inline int sys_bpf_ext_fd(enum bpf_cmd cmd, union bpf_attr *attr,
+ unsigned int size,
+ struct bpf_common_attr *attr_common,
+ unsigned int size_common)
+{
+ int fd;
+
+ fd = sys_bpf_ext(cmd, attr, size, attr_common, 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;
+
+ memset(&attr, 0, attr_sz);
+ /* This syscall() will return error always. */
+ (void) syscall(__NR_bpf, BPF_PROG_LOAD | BPF_COMMON_ATTRS, &attr, attr_sz, NULL,
+ sizeof(struct bpf_common_attr));
+ 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..e0d646a9e233 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_bpf_syscall_common_attrs(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_BPF_SYSCALL_COMMON_ATTRS] = {
+ "BPF syscall common attributes support", probe_bpf_syscall_common_attrs,
+ },
};
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..aa16be869c4f 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 BPF syscall common attributes */
+ FEAT_BPF_SYSCALL_COMMON_ATTRS,
__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 */
--
2.52.0On Tue, Jan 20, 2026 at 7:26 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
> 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 BPF syscall common attributes.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
> tools/lib/bpf/bpf.c | 32 ++++++++++++++++++++++++++++++++
> tools/lib/bpf/features.c | 8 ++++++++
> tools/lib/bpf/libbpf_internal.h | 3 +++
> 3 files changed, 43 insertions(+)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 21b57a629916..ed9c6eaeb656 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -69,6 +69,38 @@ 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 *attr_common,
> + unsigned int size_common)
> +{
> + cmd = attr_common ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS);
> + return syscall(__NR_bpf, cmd, attr, size, attr_common, size_common);
> +}
> +
> +static inline int sys_bpf_ext_fd(enum bpf_cmd cmd, union bpf_attr *attr,
> + unsigned int size,
> + struct bpf_common_attr *attr_common,
> + unsigned int size_common)
> +{
> + int fd;
> +
> + fd = sys_bpf_ext(cmd, attr, size, attr_common, 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;
> +
> + memset(&attr, 0, attr_sz);
> + /* This syscall() will return error always. */
I'll cite myself from the last review:
> But fd should really not be >= 0, and if it is -- it's some problem,
> so I'd return an error in that case to keep us aware, which is why I'm
> saying I'd just return inside if (fd >= 0) { }
I didn't say let's just ignore syscall return with (void) cast and
happily check errno no matter what, did I? Drop the comment, and
handle fd >= 0 case explicitly, please.
pw-bot: cr
> + (void) syscall(__NR_bpf, BPF_PROG_LOAD | BPF_COMMON_ATTRS, &attr, attr_sz, NULL,
> + sizeof(struct bpf_common_attr));
> + 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..e0d646a9e233 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_bpf_syscall_common_attrs(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_BPF_SYSCALL_COMMON_ATTRS] = {
> + "BPF syscall common attributes support", probe_bpf_syscall_common_attrs,
> + },
> };
>
> 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..aa16be869c4f 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 BPF syscall common attributes */
> + FEAT_BPF_SYSCALL_COMMON_ATTRS,
> __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
>
On 23/1/26 08:53, Andrii Nakryiko wrote:
> On Tue, Jan 20, 2026 at 7:26 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>
>> 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 BPF syscall common attributes.
>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>> ---
>> tools/lib/bpf/bpf.c | 32 ++++++++++++++++++++++++++++++++
>> tools/lib/bpf/features.c | 8 ++++++++
>> tools/lib/bpf/libbpf_internal.h | 3 +++
>> 3 files changed, 43 insertions(+)
>>
>> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
>> index 21b57a629916..ed9c6eaeb656 100644
>> --- a/tools/lib/bpf/bpf.c
>> +++ b/tools/lib/bpf/bpf.c
>> @@ -69,6 +69,38 @@ 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 *attr_common,
>> + unsigned int size_common)
>> +{
>> + cmd = attr_common ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS);
>> + return syscall(__NR_bpf, cmd, attr, size, attr_common, size_common);
>> +}
>> +
>> +static inline int sys_bpf_ext_fd(enum bpf_cmd cmd, union bpf_attr *attr,
>> + unsigned int size,
>> + struct bpf_common_attr *attr_common,
>> + unsigned int size_common)
>> +{
>> + int fd;
>> +
>> + fd = sys_bpf_ext(cmd, attr, size, attr_common, 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;
>> +
>> + memset(&attr, 0, attr_sz);
>> + /* This syscall() will return error always. */
>
> I'll cite myself from the last review:
>
>> But fd should really not be >= 0, and if it is -- it's some problem,
>> so I'd return an error in that case to keep us aware, which is why I'm
>> saying I'd just return inside if (fd >= 0) { }
>
> I didn't say let's just ignore syscall return with (void) cast and
> happily check errno no matter what, did I? Drop the comment, and
> handle fd >= 0 case explicitly, please.
>
My mistake — sorry for the misunderstanding.
You’re right; the return value should not be ignored. In the next
revision, I’ll handle the fd >= 0 case explicitly and drop the comment.
The logic will be updated along the lines of:
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 0;
}
return errno == EFAULT;
Thanks,
Leon
On Thu, Jan 22, 2026 at 5:41 PM Leon Hwang <leon.hwang@linux.dev> wrote:
>
>
>
> On 23/1/26 08:53, Andrii Nakryiko wrote:
> > On Tue, Jan 20, 2026 at 7:26 AM Leon Hwang <leon.hwang@linux.dev> wrote:
> >>
> >> 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 BPF syscall common attributes.
> >>
> >> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> >> ---
> >> tools/lib/bpf/bpf.c | 32 ++++++++++++++++++++++++++++++++
> >> tools/lib/bpf/features.c | 8 ++++++++
> >> tools/lib/bpf/libbpf_internal.h | 3 +++
> >> 3 files changed, 43 insertions(+)
> >>
> >> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> >> index 21b57a629916..ed9c6eaeb656 100644
> >> --- a/tools/lib/bpf/bpf.c
> >> +++ b/tools/lib/bpf/bpf.c
> >> @@ -69,6 +69,38 @@ 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 *attr_common,
> >> + unsigned int size_common)
> >> +{
> >> + cmd = attr_common ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS);
> >> + return syscall(__NR_bpf, cmd, attr, size, attr_common, size_common);
> >> +}
> >> +
> >> +static inline int sys_bpf_ext_fd(enum bpf_cmd cmd, union bpf_attr *attr,
> >> + unsigned int size,
> >> + struct bpf_common_attr *attr_common,
> >> + unsigned int size_common)
> >> +{
> >> + int fd;
> >> +
> >> + fd = sys_bpf_ext(cmd, attr, size, attr_common, 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;
> >> +
> >> + memset(&attr, 0, attr_sz);
> >> + /* This syscall() will return error always. */
> >
> > I'll cite myself from the last review:
> >
> >> But fd should really not be >= 0, and if it is -- it's some problem,
> >> so I'd return an error in that case to keep us aware, which is why I'm
> >> saying I'd just return inside if (fd >= 0) { }
> >
> > I didn't say let's just ignore syscall return with (void) cast and
> > happily check errno no matter what, did I? Drop the comment, and
> > handle fd >= 0 case explicitly, please.
> >
>
> My mistake — sorry for the misunderstanding.
>
> You’re right; the return value should not be ignored. In the next
> revision, I’ll handle the fd >= 0 case explicitly and drop the comment.
> The logic will be updated along the lines of:
>
> 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 0;
> }
> return errno == EFAULT;
>
well no, it should be
fd = syscall(...);
if (fd >= 0) {
close(fd);
return -EINVAL;
}
return errno == EFAULT ? 1 : 0;
> Thanks,
> Leon
>
>
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