[RFC PATCH bpf-next v3 00/10] bpf: Extend bpf syscall with common attributes support

[RFC PATCH bpf-next v3 00/10] bpf: Extend bpf syscall with common attributes support

[Leon Hwang]

This proposal builds upon the discussion in
"[PATCH bpf-next v4 0/4] bpf: Improve error reporting for freplace attachment failure"[1].

This patch set introduces support for *common attributes* in the 'bpf()'
syscall, providing a unified mechanism for passing shared metadata across
all BPF commands.

The initial set of common attributes includes:

1. 'log_buf': User-provided buffer for storing log output.
2. 'log_size': Size of the provided log buffer.
3. 'log_level': Verbosity level for logging.
4. 'log_true_size': The size of log reported by kernel.

With this extension, the 'bpf()' syscall will be able to return meaningful
error messages (e.g., failures of creating map), improving debuggability
and user experience.

Changes:
RFC v2 -> RFC v3:
* Rename probe_sys_bpf_extended to probe_sys_bpf_ext.
* Refactor reporting 'log_true_size' for prog_load.
* Refactor reporting 'btf_log_true_size' for btf_load.
* Add warnings for internal bugs in map_create.
* Check log_true_size in test cases.
* Address comment from Alexei:
  * Change kvzalloc/kvfree to kzalloc/kfree.
* Address comments from Andrii:
  * Move BPF_COMMON_ATTRS to 'enum bpf_cmd' alongside brief comment.
  * Add bpf_check_uarg_tail_zero() for extra checks.
  * Rename sys_bpf_extended to sys_bpf_ext.
  * Rename sys_bpf_fd_extended to sys_bpf_ext_fd.
  * Probe the new feature using NULL and -EFAULT.
  * Move probe_sys_bpf_ext to libbpf_internal.h and drop LIBBPF_API.
  * Return -EUERS when log attrs are conflict between bpf_attr and
    bpf_common_attr.
  * Avoid touching bpf_vlog_init().
  * Update the reason messages in map_create.
  * Finalize the log using __cleanup().
  * Report log size to users.
  * Change type of log_buf from '__u64' to 'const char *' and cast type
    using ptr_to_u64() in bpf_map_create().
  * Do not return -EOPNOTSUPP when kernel doesn't support this feature
    in bpf_map_create().
  * Add log_level support for map creation for consistency.
* Address comment from Eduard:
  * Use common_attrs->log_level instead of BPF_LOG_FIXED.

RFC v1 -> RFC v2:
* Fix build error reported by test bot.
* Address comments from Alexei:
  * Drop new uapi for freplace.
  * Add common attributes support for prog_load and btf_load.
  * Add common attributes support for map_create.

Links:
[1] https://lore.kernel.org/bpf/20250224153352.64689-1-leon.hwang@linux.dev/

Leon Hwang (10):
  bpf: Extend bpf syscall with common attributes support
  libbpf: Add support for extended bpf syscall
  bpf: Refactor reporting log_true_size for prog_load
  bpf: Add common attr support for prog_load
  bpf: Refactor reporting btf_log_true_size for btf_load
  bpf: Add common attr support for btf_load
  bpf: Add warnings for internal bugs in map_create
  bpf: Add common attr support for map_create
  libbpf: Add common attr support for map_create
  selftests/bpf: Add cases to test map create failure log

 include/linux/bpf.h                           |   2 +-
 include/linux/btf.h                           |   2 +-
 include/linux/syscalls.h                      |   3 +-
 include/uapi/linux/bpf.h                      |   8 +
 kernel/bpf/btf.c                              |  25 +-
 kernel/bpf/syscall.c                          | 250 ++++++++++++++++--
 kernel/bpf/verifier.c                         |  12 +-
 tools/include/uapi/linux/bpf.h                |   8 +
 tools/lib/bpf/bpf.c                           |  50 +++-
 tools/lib/bpf/bpf.h                           |   9 +-
 tools/lib/bpf/features.c                      |   8 +
 tools/lib/bpf/libbpf_internal.h               |   3 +
 .../selftests/bpf/prog_tests/map_init.c       | 140 ++++++++++
 13 files changed, 461 insertions(+), 59 deletions(-)

--
2.51.0

[RFC PATCH bpf-next v3 01/10] bpf: Extend bpf syscall with common attributes support

[Leon Hwang]

Extend the 'bpf()' syscall to support a set of common attributes shared
across all BPF commands:

1. 'log_buf': User-provided buffer for storing logs.
2. 'log_size': Size of the log buffer.
3. 'log_level': Log verbosity level.
4. 'log_true_size': The size of log reported by kernel.

These common attributes are passed as the 4th argument to the 'bpf()'
syscall, with the 5th argument specifying the size of this structure.

To indicate the use of these common attributes from userspace, a new flag
'BPF_COMMON_ATTRS' ('1 << 16') is introduced. This flag is OR-ed into the
'cmd' field of the syscall.

When 'cmd & BPF_COMMON_ATTRS' is set, the kernel will copy the common
attributes from userspace into kernel space for use.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/syscalls.h       |  3 ++-
 include/uapi/linux/bpf.h       |  8 ++++++++
 kernel/bpf/syscall.c           | 23 +++++++++++++++++++----
 tools/include/uapi/linux/bpf.h |  8 ++++++++
 4 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 77f45e5d44139..94408575dc49b 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -933,7 +933,8 @@ asmlinkage long sys_seccomp(unsigned int op, unsigned int flags,
 asmlinkage long sys_getrandom(char __user *buf, size_t count,
 			      unsigned int flags);
 asmlinkage long sys_memfd_create(const char __user *uname_ptr, unsigned int flags);
-asmlinkage long sys_bpf(int cmd, union bpf_attr __user *attr, unsigned int size);
+asmlinkage long sys_bpf(int cmd, union bpf_attr __user *attr, unsigned int size,
+			struct bpf_common_attr __user *attr_common, unsigned int size_common);
 asmlinkage long sys_execveat(int dfd, const char __user *filename,
 			const char __user *const __user *argv,
 			const char __user *const __user *envp, int flags);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index ae83d8649ef1c..bb38afd265132 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -975,6 +975,7 @@ enum bpf_cmd {
 	BPF_TOKEN_CREATE,
 	BPF_PROG_STREAM_READ_BY_FD,
 	__MAX_BPF_CMD,
+	BPF_COMMON_ATTRS = 1 << 16, /* Indicate carrying bpf_common_attr. */
 };
 
 enum bpf_map_type {
@@ -1474,6 +1475,13 @@ struct bpf_stack_build_id {
 	};
 };
 
+struct bpf_common_attr {
+	__u64 log_buf;
+	__u32 log_size;
+	__u32 log_level;
+	__u32 log_true_size;
+};
+
 #define BPF_OBJ_NAME_LEN 16U
 
 enum {
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a48fa86f82a7f..8d97d67e6abaa 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -6092,8 +6092,10 @@ static int prog_stream_read(union bpf_attr *attr)
 	return ret;
 }
 
-static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size)
+static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
+		     bpfptr_t uattr_common, unsigned int size_common)
 {
+	struct bpf_common_attr common_attrs;
 	union bpf_attr attr;
 	int err;
 
@@ -6107,6 +6109,18 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size)
 	if (copy_from_bpfptr(&attr, uattr, size) != 0)
 		return -EFAULT;
 
+	memset(&common_attrs, 0, sizeof(common_attrs));
+	if (cmd & BPF_COMMON_ATTRS) {
+		err = bpf_check_uarg_tail_zero(uattr_common, sizeof(common_attrs), size_common);
+		if (err)
+			return err;
+
+		cmd &= ~BPF_COMMON_ATTRS;
+		size_common = min_t(u32, size_common, sizeof(common_attrs));
+		if (copy_from_bpfptr(&common_attrs, uattr_common, size_common) != 0)
+			return -EFAULT;
+	}
+
 	err = security_bpf(cmd, &attr, size, uattr.is_kernel);
 	if (err < 0)
 		return err;
@@ -6239,9 +6253,10 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size)
 	return err;
 }
 
-SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
+SYSCALL_DEFINE5(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size,
+		struct bpf_common_attr __user *, uattr_common, unsigned int, size_common)
 {
-	return __sys_bpf(cmd, USER_BPFPTR(uattr), size);
+	return __sys_bpf(cmd, USER_BPFPTR(uattr), size, USER_BPFPTR(uattr_common), size_common);
 }
 
 static bool syscall_prog_is_valid_access(int off, int size,
@@ -6272,7 +6287,7 @@ BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
 	default:
 		return -EINVAL;
 	}
-	return __sys_bpf(cmd, KERNEL_BPFPTR(attr), attr_size);
+	return __sys_bpf(cmd, KERNEL_BPFPTR(attr), attr_size, KERNEL_BPFPTR(NULL), 0);
 }
 
 
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index ae83d8649ef1c..bb38afd265132 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -975,6 +975,7 @@ enum bpf_cmd {
 	BPF_TOKEN_CREATE,
 	BPF_PROG_STREAM_READ_BY_FD,
 	__MAX_BPF_CMD,
+	BPF_COMMON_ATTRS = 1 << 16, /* Indicate carrying bpf_common_attr. */
 };
 
 enum bpf_map_type {
@@ -1474,6 +1475,13 @@ struct bpf_stack_build_id {
 	};
 };
 
+struct bpf_common_attr {
+	__u64 log_buf;
+	__u32 log_size;
+	__u32 log_level;
+	__u32 log_true_size;
+};
+
 #define BPF_OBJ_NAME_LEN 16U
 
 enum {
-- 
2.51.0

[RFC PATCH bpf-next v3 02/10] libbpf: Add support for extended bpf syscall

[Leon Hwang]

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 <leon.hwang@linux.dev>
---
 tools/lib/bpf/bpf.c             | 33 +++++++++++++++++++++++++++++++++
 tools/lib/bpf/features.c        |  8 ++++++++
 tools/lib/bpf/libbpf_internal.h |  3 +++
 3 files changed, 44 insertions(+)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 339b197972374..9cd79beb13a2d 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -69,6 +69,39 @@ 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));
+	fd = errno == EFAULT ? syscall(__NR_memfd_create, "fd", 0) : fd;
+	return ensure_good_fd(fd);
+}
+
 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 760657f5224c2..d01df62394f89 100644
--- a/tools/lib/bpf/features.c
+++ b/tools/lib/bpf/features.c
@@ -507,6 +507,11 @@ 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_fd(probe_sys_bpf_ext());
+}
+
 typedef int (*feature_probe_fn)(int /* token_fd */);
 
 static struct kern_feature_cache feature_cache;
@@ -582,6 +587,9 @@ 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 c93797dcaf5bc..af05df8d040ce 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -380,6 +380,8 @@ 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,
 };
 
@@ -740,4 +742,5 @@ 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 */
-- 
2.51.0

Re: [RFC PATCH bpf-next v3 02/10] libbpf: Add support for extended bpf syscall

[Andrii Nakryiko]

On Thu, Oct 2, 2025 at 8:49 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 extended attributes.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
>  tools/lib/bpf/bpf.c             | 33 +++++++++++++++++++++++++++++++++
>  tools/lib/bpf/features.c        |  8 ++++++++
>  tools/lib/bpf/libbpf_internal.h |  3 +++
>  3 files changed, 44 insertions(+)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 339b197972374..9cd79beb13a2d 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -69,6 +69,39 @@ 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;

nit: put those () two branches of ternary operator, there is no need
to rely on obscure C operator precedence order here

> +       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));
> +       fd = errno == EFAULT ? syscall(__NR_memfd_create, "fd", 0) : fd;
> +       return ensure_good_fd(fd);

why do we need to create FD?..

> +}
> +
>  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 760657f5224c2..d01df62394f89 100644
> --- a/tools/lib/bpf/features.c
> +++ b/tools/lib/bpf/features.c
> @@ -507,6 +507,11 @@ 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_fd(probe_sys_bpf_ext());
> +}
> +

just do that feature detection right here without creating any new
FDs... make sys_bpf_ext() exposed just like we do that with sys_bpf()
and use this here


>  typedef int (*feature_probe_fn)(int /* token_fd */);
>
>  static struct kern_feature_cache feature_cache;
> @@ -582,6 +587,9 @@ 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 c93797dcaf5bc..af05df8d040ce 100644
> --- a/tools/lib/bpf/libbpf_internal.h
> +++ b/tools/lib/bpf/libbpf_internal.h
> @@ -380,6 +380,8 @@ 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,
>  };
>
> @@ -740,4 +742,5 @@ 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 */
> --
> 2.51.0
>

Re: [RFC PATCH bpf-next v3 02/10] libbpf: Add support for extended bpf syscall

[Leon Hwang]

On 7/10/25 07:08, Andrii Nakryiko wrote:
> On Thu, Oct 2, 2025 at 8:49 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 extended attributes.
>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>> ---
>>  tools/lib/bpf/bpf.c             | 33 +++++++++++++++++++++++++++++++++
>>  tools/lib/bpf/features.c        |  8 ++++++++
>>  tools/lib/bpf/libbpf_internal.h |  3 +++
>>  3 files changed, 44 insertions(+)
>>
>> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
>> index 339b197972374..9cd79beb13a2d 100644
>> --- a/tools/lib/bpf/bpf.c
>> +++ b/tools/lib/bpf/bpf.c
>> @@ -69,6 +69,39 @@ 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;
>
> nit: put those () two branches of ternary operator, there is no need
> to rely on obscure C operator precedence order here
>

Ack.

>> +       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));
>> +       fd = errno == EFAULT ? syscall(__NR_memfd_create, "fd", 0) : fd;
>> +       return ensure_good_fd(fd);
>
> why do we need to create FD?..
>
>> +}
>> +
>>  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 760657f5224c2..d01df62394f89 100644
>> --- a/tools/lib/bpf/features.c
>> +++ b/tools/lib/bpf/features.c
>> @@ -507,6 +507,11 @@ 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_fd(probe_sys_bpf_ext());
>> +}
>> +
>
> just do that feature detection right here without creating any new
> FDs... make sys_bpf_ext() exposed just like we do that with sys_bpf()
> and use this here
>

Ack.

Then I'll expose sys_bpf_ext() directly without creating any new FDs.

Thanks,
Leon

[...]

[RFC PATCH bpf-next v3 03/10] bpf: Refactor reporting log_true_size for prog_load

[Leon Hwang]

In the next commit, it will be able to report logs via extended common
attributes, which will report 'log_true_size' via the extended common
attributes meanwhile.

Therefore, refactor the way of 'log_true_size' reporting in order to
report 'log_true_size' via the extended common attributes easily.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/bpf.h   |  2 +-
 kernel/bpf/syscall.c  | 24 ++++++++++++++++++++----
 kernel/bpf/verifier.c | 12 ++----------
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a98c833461347..4f595439943d7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2738,7 +2738,7 @@ int bpf_check_uarg_tail_zero(bpfptr_t uaddr, size_t expected_size,
 			     size_t actual_size);
 
 /* verify correctness of eBPF program */
-int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size);
+int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr);
 
 #ifndef CONFIG_BPF_JIT_ALWAYS_ON
 void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 8d97d67e6abaa..2bdc0b43ec832 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2841,7 +2841,7 @@ static int bpf_prog_verify_signature(struct bpf_prog *prog, union bpf_attr *attr
 /* last field in 'union bpf_attr' used by this command */
 #define BPF_PROG_LOAD_LAST_FIELD keyring_id
 
-static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
+static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
 {
 	enum bpf_prog_type type = attr->prog_type;
 	struct bpf_prog *prog, *dst_prog = NULL;
@@ -3059,7 +3059,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 		goto free_prog_sec;
 
 	/* run eBPF verifier */
-	err = bpf_check(&prog, attr, uattr, uattr_size);
+	err = bpf_check(&prog, attr, uattr);
 	if (err < 0)
 		goto free_used_maps;
 
@@ -6092,12 +6092,25 @@ static int prog_stream_read(union bpf_attr *attr)
 	return ret;
 }
 
+static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size)
+{
+	if (!attr->log_true_size)
+		return 0;
+
+	if (size >= offsetofend(union bpf_attr, log_true_size) &&
+	    copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, log_true_size),
+				  &attr->log_true_size, sizeof(attr->log_true_size)))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		     bpfptr_t uattr_common, unsigned int size_common)
 {
 	struct bpf_common_attr common_attrs;
 	union bpf_attr attr;
-	int err;
+	int err, ret;
 
 	err = bpf_check_uarg_tail_zero(uattr, sizeof(attr), size);
 	if (err)
@@ -6145,7 +6158,10 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		err = map_freeze(&attr);
 		break;
 	case BPF_PROG_LOAD:
-		err = bpf_prog_load(&attr, uattr, size);
+		attr.log_true_size = 0;
+		err = bpf_prog_load(&attr, uattr);
+		ret = copy_prog_load_log_true_size(&attr, uattr, size);
+		err = ret ? ret : err;
 		break;
 	case BPF_OBJ_PIN:
 		err = bpf_obj_pin(&attr);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e892df386eed7..d5089f026f578 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -24499,12 +24499,11 @@ static int compute_scc(struct bpf_verifier_env *env)
 	return err;
 }
 
-int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
+int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr)
 {
 	u64 start_time = ktime_get_ns();
 	struct bpf_verifier_env *env;
 	int i, len, ret = -EINVAL, err;
-	u32 log_true_size;
 	bool is_priv;
 
 	BTF_TYPE_EMIT(enum bpf_features);
@@ -24700,17 +24699,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	env->prog->aux->verified_insns = env->insn_processed;
 
 	/* preserve original error even if log finalization is successful */
-	err = bpf_vlog_finalize(&env->log, &log_true_size);
+	err = bpf_vlog_finalize(&env->log, &attr->log_true_size);
 	if (err)
 		ret = err;
 
-	if (uattr_size >= offsetofend(union bpf_attr, log_true_size) &&
-	    copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, log_true_size),
-				  &log_true_size, sizeof(log_true_size))) {
-		ret = -EFAULT;
-		goto err_release_maps;
-	}
-
 	if (ret)
 		goto err_release_maps;
 
-- 
2.51.0

Re: [RFC PATCH bpf-next v3 03/10] bpf: Refactor reporting log_true_size for prog_load

[Alexei Starovoitov]

On Thu, Oct 2, 2025 at 8:49 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
> In the next commit, it will be able to report logs via extended common
> attributes, which will report 'log_true_size' via the extended common
> attributes meanwhile.
>
> Therefore, refactor the way of 'log_true_size' reporting in order to
> report 'log_true_size' via the extended common attributes easily.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
>  include/linux/bpf.h   |  2 +-
>  kernel/bpf/syscall.c  | 24 ++++++++++++++++++++----
>  kernel/bpf/verifier.c | 12 ++----------
>  3 files changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index a98c833461347..4f595439943d7 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -2738,7 +2738,7 @@ int bpf_check_uarg_tail_zero(bpfptr_t uaddr, size_t expected_size,
>                              size_t actual_size);
>
>  /* verify correctness of eBPF program */
> -int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size);
> +int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr);
>
>  #ifndef CONFIG_BPF_JIT_ALWAYS_ON
>  void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 8d97d67e6abaa..2bdc0b43ec832 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2841,7 +2841,7 @@ static int bpf_prog_verify_signature(struct bpf_prog *prog, union bpf_attr *attr
>  /* last field in 'union bpf_attr' used by this command */
>  #define BPF_PROG_LOAD_LAST_FIELD keyring_id
>
> -static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
> +static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
>  {
>         enum bpf_prog_type type = attr->prog_type;
>         struct bpf_prog *prog, *dst_prog = NULL;
> @@ -3059,7 +3059,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
>                 goto free_prog_sec;
>
>         /* run eBPF verifier */
> -       err = bpf_check(&prog, attr, uattr, uattr_size);
> +       err = bpf_check(&prog, attr, uattr);
>         if (err < 0)
>                 goto free_used_maps;
>
> @@ -6092,12 +6092,25 @@ static int prog_stream_read(union bpf_attr *attr)
>         return ret;
>  }
>
> +static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size)
> +{
> +       if (!attr->log_true_size)
> +               return 0;

We've been through this many times :(
The commit log says that it's a refactoring patch, but
you introduce this new logic.
Do NOT do it.
If you want to add such additional check, do it in a separate patch
and explain why it's ok.

So why is it ok to skip writing to user space when it's zero?

> +       if (size >= offsetofend(union bpf_attr, log_true_size) &&
> +           copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, log_true_size),
> +                                 &attr->log_true_size, sizeof(attr->log_true_size)))
> +               return -EFAULT;
> +
> +       return 0;
> +}

Re: [RFC PATCH bpf-next v3 03/10] bpf: Refactor reporting log_true_size for prog_load

[Leon Hwang]

On 3/10/25 02:34, Alexei Starovoitov wrote:
> On Thu, Oct 2, 2025 at 8:49 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>
>> In the next commit, it will be able to report logs via extended common
>> attributes, which will report 'log_true_size' via the extended common
>> attributes meanwhile.
>>
>> Therefore, refactor the way of 'log_true_size' reporting in order to
>> report 'log_true_size' via the extended common attributes easily.
>>

[...]

>>
>> +static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size)
>> +{
>> +       if (!attr->log_true_size)
>> +               return 0;
> 
> We've been through this many times :(
> The commit log says that it's a refactoring patch, but
> you introduce this new logic.
> Do NOT do it.
> If you want to add such additional check, do it in a separate patch
> and explain why it's ok.
> 
> So why is it ok to skip writing to user space when it's zero?
> 

My mistake — I see now that introducing this extra check changes the
behavior and doesn't belong in a refactoring patch.

My original intention was just to avoid calling copy_to_user() when
there is no log, but as you pointed out, it's important to still report
log_true_size back to user space, even if it's zero. That way, users can
reliably check if a log is present.

I'll drop this new logic in the next revision and keep the patch
strictly as a refactoring.

Thanks,
Leon

[RFC PATCH bpf-next v3 04/10] bpf: Add common attr support for prog_load

[Leon Hwang]

The log buffer of common attributes would be confusing with the one in
'union bpf_attr' for BPF_PROG_LOAD.

In order to clarify the usage of these two log buffers, they both can be
used for logging if:

* They are same, including 'log_buf', 'log_level' and 'log_size'.
* One of them is missing, then another one will be used for logging.

If they both have 'log_buf' but they are not same totally, return -EUSERS.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 kernel/bpf/syscall.c | 55 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 53 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2bdc0b43ec832..698c30ff99486 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -6092,11 +6092,57 @@ static int prog_stream_read(union bpf_attr *attr)
 	return ret;
 }
 
-static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size)
+static int check_log_attrs(u64 log_buf, u32 log_size, u32 log_level,
+			   struct bpf_common_attr *common_attrs)
+{
+	if (log_buf && common_attrs->log_buf && (log_buf != common_attrs->log_buf ||
+						 log_size != common_attrs->log_size ||
+						 log_level != common_attrs->log_level))
+		return -EUSERS;
+
+	return 0;
+}
+
+static int check_prog_load_log_attrs(union bpf_attr *attr, struct bpf_common_attr *common_attrs,
+				     bool *log_common_attrs)
+{
+	int err;
+
+	err = check_log_attrs(attr->log_buf, attr->log_size, attr->log_level, common_attrs);
+	if (err)
+		return err;
+
+	if (!attr->log_buf && common_attrs->log_buf) {
+		*log_common_attrs = true;
+		attr->log_buf = common_attrs->log_buf;
+		attr->log_size = common_attrs->log_size;
+		attr->log_level = common_attrs->log_level;
+	}
+
+	return 0;
+}
+
+static int __copy_common_attr_log_true_size(bpfptr_t uattr, unsigned int size, u32 *log_true_size)
+{
+	if (size >= offsetofend(struct bpf_common_attr, log_true_size) &&
+	    copy_to_bpfptr_offset(uattr, offsetof(struct bpf_common_attr, log_true_size),
+				  log_true_size, sizeof(*log_true_size)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size,
+					struct bpf_common_attr *common_attrs, bpfptr_t uattr_common,
+					unsigned int size_common, bool log_common_attrs)
 {
 	if (!attr->log_true_size)
 		return 0;
 
+	if (log_common_attrs)
+		return __copy_common_attr_log_true_size(uattr_common, size_common,
+							&attr->log_true_size);
+
 	if (size >= offsetofend(union bpf_attr, log_true_size) &&
 	    copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, log_true_size),
 				  &attr->log_true_size, sizeof(attr->log_true_size)))
@@ -6109,6 +6155,7 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		     bpfptr_t uattr_common, unsigned int size_common)
 {
 	struct bpf_common_attr common_attrs;
+	bool log_common_attrs = false;
 	union bpf_attr attr;
 	int err, ret;
 
@@ -6158,9 +6205,13 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		err = map_freeze(&attr);
 		break;
 	case BPF_PROG_LOAD:
+		err = check_prog_load_log_attrs(&attr, &common_attrs, &log_common_attrs);
+		if (err)
+			break;
 		attr.log_true_size = 0;
 		err = bpf_prog_load(&attr, uattr);
-		ret = copy_prog_load_log_true_size(&attr, uattr, size);
+		ret = copy_prog_load_log_true_size(&attr, uattr, size, &common_attrs, uattr_common,
+						   size_common, log_common_attrs);
 		err = ret ? ret : err;
 		break;
 	case BPF_OBJ_PIN:
-- 
2.51.0

Re: [RFC PATCH bpf-next v3 04/10] bpf: Add common attr support for prog_load

[Alexei Starovoitov]

On Thu, Oct 2, 2025 at 8:49 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
> The log buffer of common attributes would be confusing with the one in
> 'union bpf_attr' for BPF_PROG_LOAD.
>
> In order to clarify the usage of these two log buffers, they both can be
> used for logging if:
>
> * They are same, including 'log_buf', 'log_level' and 'log_size'.
> * One of them is missing, then another one will be used for logging.
>
> If they both have 'log_buf' but they are not same totally, return -EUSERS.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
>  kernel/bpf/syscall.c | 55 ++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 53 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 2bdc0b43ec832..698c30ff99486 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -6092,11 +6092,57 @@ static int prog_stream_read(union bpf_attr *attr)
>         return ret;
>  }
>
> -static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size)
> +static int check_log_attrs(u64 log_buf, u32 log_size, u32 log_level,
> +                          struct bpf_common_attr *common_attrs)
> +{
> +       if (log_buf && common_attrs->log_buf && (log_buf != common_attrs->log_buf ||
> +                                                log_size != common_attrs->log_size ||
> +                                                log_level != common_attrs->log_level))
> +               return -EUSERS;
> +
> +       return 0;
> +}
> +
> +static int check_prog_load_log_attrs(union bpf_attr *attr, struct bpf_common_attr *common_attrs,
> +                                    bool *log_common_attrs)
> +{
> +       int err;
> +
> +       err = check_log_attrs(attr->log_buf, attr->log_size, attr->log_level, common_attrs);
> +       if (err)
> +               return err;
> +
> +       if (!attr->log_buf && common_attrs->log_buf) {
> +               *log_common_attrs = true;

I feel like a broken record.
Do not use 'bool' arguments. There is always a better option.
'bool *' is even worse.

Re: [RFC PATCH bpf-next v3 04/10] bpf: Add common attr support for prog_load

[Leon Hwang]

On 3/10/25 07:51, Alexei Starovoitov wrote:
> On Thu, Oct 2, 2025 at 8:49 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>

[...]

>> +
>> +       if (!attr->log_buf && common_attrs->log_buf) {
>> +               *log_common_attrs = true;
> 
> I feel like a broken record.
> Do not use 'bool' arguments. There is always a better option.
> 'bool *' is even worse.

Got it — I now understand that using 'bool' here (especially as a
pointer) is a code smell and generally discouraged.

I'll remove log_common_attrs and reimplement this part to avoid the
'bool' argument altogether. I'll look for a cleaner alternative in the
next revision.

Thanks,
Leon

[RFC PATCH bpf-next v3 05/10] bpf: Refactor reporting btf_log_true_size for btf_load

[Leon Hwang]

In the next commit, it will be able to report logs via extended common
attributes, which will report 'log_true_size' via the extended common
attributes meanwhile.

Therefore, refactor the way of 'btf_log_true_size' reporting in order to
report 'log_true_size' via the extended common attributes easily.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/btf.h  |  2 +-
 kernel/bpf/btf.c     | 25 +++++--------------------
 kernel/bpf/syscall.c | 22 +++++++++++++++++++---
 3 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index f06976ffb63f9..60e29d05a8a90 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -145,7 +145,7 @@ const char *btf_get_name(const struct btf *btf);
 void btf_get(struct btf *btf);
 void btf_put(struct btf *btf);
 const struct btf_header *btf_header(const struct btf *btf);
-int btf_new_fd(const union bpf_attr *attr, bpfptr_t uattr, u32 uattr_sz);
+int btf_new_fd(union bpf_attr *attr, bpfptr_t uattr);
 struct btf *btf_get_by_fd(int fd);
 int btf_get_info_by_fd(const struct btf *btf,
 		       const union bpf_attr *attr,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 0de8fc8a0e0b3..0d83ce16947d7 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5745,22 +5745,7 @@ static int btf_check_type_tags(struct btf_verifier_env *env,
 	return 0;
 }
 
-static int finalize_log(struct bpf_verifier_log *log, bpfptr_t uattr, u32 uattr_size)
-{
-	u32 log_true_size;
-	int err;
-
-	err = bpf_vlog_finalize(log, &log_true_size);
-
-	if (uattr_size >= offsetofend(union bpf_attr, btf_log_true_size) &&
-	    copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, btf_log_true_size),
-				  &log_true_size, sizeof(log_true_size)))
-		err = -EFAULT;
-
-	return err;
-}
-
-static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
+static struct btf *btf_parse(union bpf_attr *attr, bpfptr_t uattr)
 {
 	bpfptr_t btf_data = make_bpfptr(attr->btf, uattr.is_kernel);
 	char __user *log_ubuf = u64_to_user_ptr(attr->btf_log_buf);
@@ -5841,7 +5826,7 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat
 		}
 	}
 
-	err = finalize_log(&env->log, uattr, uattr_size);
+	err = bpf_vlog_finalize(&env->log, &attr->btf_log_true_size);
 	if (err)
 		goto errout_free;
 
@@ -5853,7 +5838,7 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat
 	btf_free_struct_meta_tab(btf);
 errout:
 	/* overwrite err with -ENOSPC or -EFAULT */
-	ret = finalize_log(&env->log, uattr, uattr_size);
+	ret = bpf_vlog_finalize(&env->log, &attr->btf_log_true_size);
 	if (ret)
 		err = ret;
 errout_free:
@@ -8017,12 +8002,12 @@ static int __btf_new_fd(struct btf *btf)
 	return anon_inode_getfd("btf", &btf_fops, btf, O_RDONLY | O_CLOEXEC);
 }
 
-int btf_new_fd(const union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
+int btf_new_fd(union bpf_attr *attr, bpfptr_t uattr)
 {
 	struct btf *btf;
 	int ret;
 
-	btf = btf_parse(attr, uattr, uattr_size);
+	btf = btf_parse(attr, uattr);
 	if (IS_ERR(btf))
 		return PTR_ERR(btf);
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 698c30ff99486..3bdcd6c065039 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -5397,7 +5397,7 @@ static int bpf_obj_get_info_by_fd(const union bpf_attr *attr,
 
 #define BPF_BTF_LOAD_LAST_FIELD btf_token_fd
 
-static int bpf_btf_load(const union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
+static int bpf_btf_load(union bpf_attr *attr, bpfptr_t uattr)
 {
 	struct bpf_token *token = NULL;
 
@@ -5424,7 +5424,7 @@ static int bpf_btf_load(const union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_
 
 	bpf_token_put(token);
 
-	return btf_new_fd(attr, uattr, uattr_size);
+	return btf_new_fd(attr, uattr);
 }
 
 #define BPF_BTF_GET_FD_BY_ID_LAST_FIELD fd_by_id_token_fd
@@ -6151,6 +6151,19 @@ static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, un
 	return 0;
 }
 
+static int copy_btf_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size)
+{
+	if (!attr->btf_log_true_size)
+		return 0;
+
+	if (size >= offsetofend(union bpf_attr, btf_log_true_size) &&
+	    copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, btf_log_true_size),
+				  &attr->btf_log_true_size, sizeof(attr->btf_log_true_size)))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		     bpfptr_t uattr_common, unsigned int size_common)
 {
@@ -6257,7 +6270,10 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		err = bpf_raw_tracepoint_open(&attr);
 		break;
 	case BPF_BTF_LOAD:
-		err = bpf_btf_load(&attr, uattr, size);
+		attr.btf_log_true_size = 0;
+		err = bpf_btf_load(&attr, uattr);
+		ret = copy_btf_load_log_true_size(&attr, uattr, size);
+		err = ret ? ret : err;
 		break;
 	case BPF_BTF_GET_FD_BY_ID:
 		err = bpf_btf_get_fd_by_id(&attr);
-- 
2.51.0

[RFC PATCH bpf-next v3 06/10] bpf: Add common attr support for btf_load

[Leon Hwang]

The log buffer of common attributes would be confusing with the one in
'union bpf_attr' for BPF_BTF_LOAD.

In order to clarify the usage of these two log buffers, they both can be
used for logging if:

* They are same, including 'log_buf', 'log_level' and 'log_size'.
* One of them is missing, then another one will be used for logging.

If they both have 'log_buf' but they are not same totally, return -EUSERS.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 kernel/bpf/syscall.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3bdcd6c065039..fc1b5c8c5e82f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -6151,11 +6151,37 @@ static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, un
 	return 0;
 }
 
-static int copy_btf_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size)
+static int check_btf_load_log_attrs(union bpf_attr *attr, struct bpf_common_attr *common_attrs,
+				    bool *log_common_attrs)
+{
+	int err;
+
+	err = check_log_attrs(attr->btf_log_buf, attr->btf_log_size, attr->btf_log_level,
+			      common_attrs);
+	if (err)
+		return err;
+
+	if (!attr->btf_log_buf && common_attrs->log_buf) {
+		*log_common_attrs = true;
+		attr->btf_log_buf = common_attrs->log_buf;
+		attr->btf_log_size = common_attrs->log_size;
+		attr->btf_log_level = common_attrs->log_level;
+	}
+
+	return 0;
+}
+
+static int copy_btf_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size,
+				       struct bpf_common_attr *common_attrs, bpfptr_t uattr_common,
+				       unsigned int size_common, bool log_common_attrs)
 {
 	if (!attr->btf_log_true_size)
 		return 0;
 
+	if (log_common_attrs)
+		return __copy_common_attr_log_true_size(uattr_common, size_common,
+							&attr->btf_log_true_size);
+
 	if (size >= offsetofend(union bpf_attr, btf_log_true_size) &&
 	    copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, btf_log_true_size),
 				  &attr->btf_log_true_size, sizeof(attr->btf_log_true_size)))
@@ -6270,9 +6296,13 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		err = bpf_raw_tracepoint_open(&attr);
 		break;
 	case BPF_BTF_LOAD:
+		err = check_btf_load_log_attrs(&attr, &common_attrs, &log_common_attrs);
+		if (err)
+			break;
 		attr.btf_log_true_size = 0;
 		err = bpf_btf_load(&attr, uattr);
-		ret = copy_btf_load_log_true_size(&attr, uattr, size);
+		ret = copy_btf_load_log_true_size(&attr, uattr, size, &common_attrs, uattr_common,
+						  size_common, log_common_attrs);
 		err = ret ? ret : err;
 		break;
 	case BPF_BTF_GET_FD_BY_ID:
-- 
2.51.0

[RFC PATCH bpf-next v3 07/10] bpf: Add warnings for internal bugs in map_create

[Leon Hwang]

In next commit, it will report users the reason of -EINVAL in
map_create.

However, as for the check of '!ops' and '!ops->map_mem_usage', it
shouldn't report the reason as they would be internal bugs.

Instead, add WARN_ON_ONCE to them. Then, it is able to check dmesg to get
the error details.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 kernel/bpf/syscall.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index fc1b5c8c5e82f..49db250a2f5da 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1406,7 +1406,7 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 		return -EINVAL;
 	map_type = array_index_nospec(map_type, ARRAY_SIZE(bpf_map_types));
 	ops = bpf_map_types[map_type];
-	if (!ops)
+	if (WARN_ON_ONCE(!ops))
 		return -EINVAL;
 
 	if (ops->map_alloc_check) {
@@ -1416,7 +1416,7 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 	}
 	if (attr->map_ifindex)
 		ops = &bpf_map_offload_ops;
-	if (!ops->map_mem_usage)
+	if (WARN_ON_ONCE(!ops->map_mem_usage))
 		return -EINVAL;
 
 	if (token_flag) {
-- 
2.51.0

Re: [RFC PATCH bpf-next v3 07/10] bpf: Add warnings for internal bugs in map_create

[Alexei Starovoitov]

On Thu, Oct 2, 2025 at 8:49 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
> In next commit, it will report users the reason of -EINVAL in
> map_create.
>
> However, as for the check of '!ops' and '!ops->map_mem_usage', it
> shouldn't report the reason as they would be internal bugs.
>
> Instead, add WARN_ON_ONCE to them. Then, it is able to check dmesg to get
> the error details.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
>  kernel/bpf/syscall.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index fc1b5c8c5e82f..49db250a2f5da 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -1406,7 +1406,7 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
>                 return -EINVAL;
>         map_type = array_index_nospec(map_type, ARRAY_SIZE(bpf_map_types));
>         ops = bpf_map_types[map_type];
> -       if (!ops)
> +       if (WARN_ON_ONCE(!ops))
>                 return -EINVAL;

It was a strong recommendation for a long time to avoid WARN*() at all cost.
In the verifier we removed majority of them and replaced with verifier_bug()
which WARNS only when DEBUG_KERNEL.

Here there is no reason to warn at all. Keep it as-is.

Re: [RFC PATCH bpf-next v3 07/10] bpf: Add warnings for internal bugs in map_create

[Leon Hwang]

On 3/10/25 08:06, Alexei Starovoitov wrote:
> On Thu, Oct 2, 2025 at 8:49 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>
>> In next commit, it will report users the reason of -EINVAL in
>> map_create.
>>
>> However, as for the check of '!ops' and '!ops->map_mem_usage', it
>> shouldn't report the reason as they would be internal bugs.
>>
>> Instead, add WARN_ON_ONCE to them. Then, it is able to check dmesg to get
>> the error details.
>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>> ---
>>  kernel/bpf/syscall.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>> index fc1b5c8c5e82f..49db250a2f5da 100644
>> --- a/kernel/bpf/syscall.c
>> +++ b/kernel/bpf/syscall.c
>> @@ -1406,7 +1406,7 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
>>                 return -EINVAL;
>>         map_type = array_index_nospec(map_type, ARRAY_SIZE(bpf_map_types));
>>         ops = bpf_map_types[map_type];
>> -       if (!ops)
>> +       if (WARN_ON_ONCE(!ops))
>>                 return -EINVAL;
> 
> It was a strong recommendation for a long time to avoid WARN*() at all cost.
> In the verifier we removed majority of them and replaced with verifier_bug()
> which WARNS only when DEBUG_KERNEL.
> 
> Here there is no reason to warn at all. Keep it as-is.

Got it, thanks for clarifying.

I understand now that WARN*() should generally be avoided, since they
add noise and aren't justified here. The existing 'return -EINVAL;' is
sufficient.

I'll keep it as-is in the next revision.

Thanks,
Leon

[RFC PATCH bpf-next v3 08/10] bpf: Add common attr support for map_create

[Leon Hwang]

Currently, many 'BPF_MAP_CREATE' failures return '-EINVAL' without
providing any explanation to user space.

With the extended BPF syscall support, detailed error messages can now be
reported. This allows users to understand the specific reason for a
failed map creation, rather than just receiving a generic '-EINVAL'.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 kernel/bpf/syscall.c | 96 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 87 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 49db250a2f5da..24f46cf451bec 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1355,23 +1355,72 @@ static bool bpf_net_capable(void)
 	return capable(CAP_NET_ADMIN) || capable(CAP_SYS_ADMIN);
 }
 
+struct bpf_vlog_wrapper {
+	struct bpf_common_attr *attr;
+	struct bpf_verifier_log *log;
+};
+
+static void bpf_vlog_wrapper_destructor(struct bpf_vlog_wrapper *w)
+{
+	if (!w->log)
+		return;
+
+	(void) bpf_vlog_finalize(w->log, &w->attr->log_true_size);
+	kfree(w->log);
+}
+
+#define DEFINE_BPF_VLOG_WRAPPER(name, common_attrs)				\
+	struct bpf_vlog_wrapper name __cleanup(bpf_vlog_wrapper_destructor) = {	\
+		.attr = common_attrs,						\
+	}
+
+static int bpf_vlog_wrapper_init(struct bpf_vlog_wrapper *w)
+{
+	struct bpf_common_attr *attr = w->attr;
+	struct bpf_verifier_log *log;
+	int err;
+
+	if (!attr->log_buf)
+		return 0;
+
+	log = kzalloc(sizeof(*log), GFP_KERNEL);
+	if (!log)
+		return -ENOMEM;
+
+	err = bpf_vlog_init(log, attr->log_level, u64_to_user_ptr(attr->log_buf), attr->log_size);
+	if (err) {
+		kfree(log);
+		return err;
+	}
+
+	w->log = log;
+	return 0;
+}
+
 #define BPF_MAP_CREATE_LAST_FIELD excl_prog_hash_size
 /* called via syscall */
-static int map_create(union bpf_attr *attr, bpfptr_t uattr)
+static int map_create(union bpf_attr *attr, bpfptr_t uattr, struct bpf_common_attr *common_attrs)
 {
 	const struct bpf_map_ops *ops;
 	struct bpf_token *token = NULL;
 	int numa_node = bpf_map_attr_numa_node(attr);
 	u32 map_type = attr->map_type;
+	struct bpf_verifier_log *log;
 	struct bpf_map *map;
 	bool token_flag;
 	int f_flags;
 	int err;
+	DEFINE_BPF_VLOG_WRAPPER(log_wrapper, common_attrs);
 
 	err = CHECK_ATTR(BPF_MAP_CREATE);
 	if (err)
 		return -EINVAL;
 
+	err = bpf_vlog_wrapper_init(&log_wrapper);
+	if (err)
+		return err;
+	log = log_wrapper.log;
+
 	/* check BPF_F_TOKEN_FD flag, remember if it's set, and then clear it
 	 * to avoid per-map type checks tripping on unknown flag
 	 */
@@ -1379,17 +1428,25 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 	attr->map_flags &= ~BPF_F_TOKEN_FD;
 
 	if (attr->btf_vmlinux_value_type_id) {
-		if (attr->map_type != BPF_MAP_TYPE_STRUCT_OPS ||
-		    attr->btf_key_type_id || attr->btf_value_type_id)
+		if (attr->map_type != BPF_MAP_TYPE_STRUCT_OPS) {
+			bpf_log(log, "btf_vmlinux_value_type_id can only be used with struct_ops maps.\n");
+			return -EINVAL;
+		}
+		if (attr->btf_key_type_id || attr->btf_value_type_id) {
+			bpf_log(log, "btf_vmlinux_value_type_id is mutually exclusive with btf_key_type_id and btf_value_type_id.\n");
 			return -EINVAL;
+		}
 	} else if (attr->btf_key_type_id && !attr->btf_value_type_id) {
+		bpf_log(log, "Invalid btf_value_type_id.\n");
 		return -EINVAL;
 	}
 
 	if (attr->map_type != BPF_MAP_TYPE_BLOOM_FILTER &&
 	    attr->map_type != BPF_MAP_TYPE_ARENA &&
-	    attr->map_extra != 0)
+	    attr->map_extra != 0) {
+		bpf_log(log, "Invalid map_extra.\n");
 		return -EINVAL;
+	}
 
 	f_flags = bpf_get_file_flag(attr->map_flags);
 	if (f_flags < 0)
@@ -1397,13 +1454,17 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 
 	if (numa_node != NUMA_NO_NODE &&
 	    ((unsigned int)numa_node >= nr_node_ids ||
-	     !node_online(numa_node)))
+	     !node_online(numa_node))) {
+		bpf_log(log, "Invalid numa_node.\n");
 		return -EINVAL;
+	}
 
 	/* find map type and init map: hashtable vs rbtree vs bloom vs ... */
 	map_type = attr->map_type;
-	if (map_type >= ARRAY_SIZE(bpf_map_types))
+	if (map_type >= ARRAY_SIZE(bpf_map_types)) {
+		bpf_log(log, "Invalid map_type.\n");
 		return -EINVAL;
+	}
 	map_type = array_index_nospec(map_type, ARRAY_SIZE(bpf_map_types));
 	ops = bpf_map_types[map_type];
 	if (WARN_ON_ONCE(!ops))
@@ -1421,8 +1482,10 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 
 	if (token_flag) {
 		token = bpf_token_get_from_fd(attr->map_token_fd);
-		if (IS_ERR(token))
+		if (IS_ERR(token)) {
+			bpf_log(log, "Invalid map_token_fd.\n");
 			return PTR_ERR(token);
+		}
 
 		/* if current token doesn't grant map creation permissions,
 		 * then we can't use this token, so ignore it and rely on
@@ -1504,8 +1567,10 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 
 	err = bpf_obj_name_cpy(map->name, attr->map_name,
 			       sizeof(attr->map_name));
-	if (err < 0)
+	if (err < 0) {
+		bpf_log(log, "Invalid map_name.\n");
 		goto free_map;
+	}
 
 	preempt_disable();
 	map->cookie = gen_cookie_next(&bpf_map_cookie);
@@ -1528,6 +1593,7 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 
 		btf = btf_get_by_fd(attr->btf_fd);
 		if (IS_ERR(btf)) {
+			bpf_log(log, "Invalid btf_fd.\n");
 			err = PTR_ERR(btf);
 			goto free_map;
 		}
@@ -6132,6 +6198,15 @@ static int __copy_common_attr_log_true_size(bpfptr_t uattr, unsigned int size, u
 	return 0;
 }
 
+static int copy_common_attr_log_true_size(bpfptr_t uattr, unsigned int size,
+					  struct bpf_common_attr *attr)
+{
+	if (!attr->log_true_size)
+		return 0;
+
+	return __copy_common_attr_log_true_size(uattr, size, &attr->log_true_size);
+}
+
 static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size,
 					struct bpf_common_attr *common_attrs, bpfptr_t uattr_common,
 					unsigned int size_common, bool log_common_attrs)
@@ -6226,7 +6301,10 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 
 	switch (cmd) {
 	case BPF_MAP_CREATE:
-		err = map_create(&attr, uattr);
+		common_attrs.log_true_size = 0;
+		err = map_create(&attr, uattr, &common_attrs);
+		ret = copy_common_attr_log_true_size(uattr_common, size_common, &common_attrs);
+		err = ret ? ret : err;
 		break;
 	case BPF_MAP_LOOKUP_ELEM:
 		err = map_lookup_elem(&attr);
-- 
2.51.0

[RFC PATCH bpf-next v3 09/10] libbpf: Add common attr support for map_create

[Leon Hwang]

With the previous commit adding common attribute support for
BPF_MAP_CREATE, it is now possible to retrieve detailed error messages
when map creation fails by using the 'log_buf' field from the common
attributes.

Extend 'bpf_map_create_opts' with these new fields, 'log_buf', 'log_size'
, 'log_level' and 'log_true_size', allowing users to capture and inspect
those log messages.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 tools/lib/bpf/bpf.c | 17 +++++++++++++++--
 tools/lib/bpf/bpf.h |  9 +++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 9cd79beb13a2d..ca66fcdb3f49f 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -203,10 +203,13 @@ int bpf_map_create(enum bpf_map_type map_type,
 		   __u32 key_size,
 		   __u32 value_size,
 		   __u32 max_entries,
-		   const struct bpf_map_create_opts *opts)
+		   struct bpf_map_create_opts *opts)
 {
 	const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size);
+	const size_t common_attrs_sz = sizeof(struct bpf_common_attr);
+	struct bpf_common_attr common_attrs;
 	union bpf_attr attr;
+	const char *log_buf;
 	int fd;
 
 	bump_rlimit_memlock();
@@ -239,7 +242,17 @@ int bpf_map_create(enum bpf_map_type map_type,
 	attr.excl_prog_hash = ptr_to_u64(OPTS_GET(opts, excl_prog_hash, NULL));
 	attr.excl_prog_hash_size = OPTS_GET(opts, excl_prog_hash_size, 0);
 
-	fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
+	log_buf = OPTS_GET(opts, log_buf, NULL);
+	if (log_buf && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
+		memset(&common_attrs, 0, common_attrs_sz);
+		common_attrs.log_buf = ptr_to_u64(log_buf);
+		common_attrs.log_size = OPTS_GET(opts, log_size, 0);
+		common_attrs.log_level = OPTS_GET(opts, log_level, 0);
+		fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attrs, common_attrs_sz);
+		OPTS_SET(opts, log_true_size, common_attrs.log_true_size);
+	} else {
+		fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
+	}
 	return libbpf_err_errno(fd);
 }
 
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index e983a3e40d612..77d475e7274a0 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -57,16 +57,21 @@ struct bpf_map_create_opts {
 
 	const void *excl_prog_hash;
 	__u32 excl_prog_hash_size;
+
+	const char *log_buf;
+	__u32 log_size;
+	__u32 log_level;
+	__u32 log_true_size;
 	size_t :0;
 };
-#define bpf_map_create_opts__last_field excl_prog_hash_size
+#define bpf_map_create_opts__last_field log_true_size
 
 LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
 			      const char *map_name,
 			      __u32 key_size,
 			      __u32 value_size,
 			      __u32 max_entries,
-			      const struct bpf_map_create_opts *opts);
+			      struct bpf_map_create_opts *opts);
 
 struct bpf_prog_load_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
-- 
2.51.0

Re: [RFC PATCH bpf-next v3 09/10] libbpf: Add common attr support for map_create

[Andrii Nakryiko]

On Thu, Oct 2, 2025 at 8:49 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
> With the previous commit adding common attribute support for
> BPF_MAP_CREATE, it is now possible to retrieve detailed error messages
> when map creation fails by using the 'log_buf' field from the common
> attributes.
>
> Extend 'bpf_map_create_opts' with these new fields, 'log_buf', 'log_size'
> , 'log_level' and 'log_true_size', allowing users to capture and inspect

comma

> those log messages.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
>  tools/lib/bpf/bpf.c | 17 +++++++++++++++--
>  tools/lib/bpf/bpf.h |  9 +++++++--
>  2 files changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 9cd79beb13a2d..ca66fcdb3f49f 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -203,10 +203,13 @@ int bpf_map_create(enum bpf_map_type map_type,
>                    __u32 key_size,
>                    __u32 value_size,
>                    __u32 max_entries,
> -                  const struct bpf_map_create_opts *opts)
> +                  struct bpf_map_create_opts *opts)

this is a breaking change, see below

>  {
>         const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size);
> +       const size_t common_attrs_sz = sizeof(struct bpf_common_attr);
> +       struct bpf_common_attr common_attrs;
>         union bpf_attr attr;
> +       const char *log_buf;
>         int fd;
>
>         bump_rlimit_memlock();
> @@ -239,7 +242,17 @@ int bpf_map_create(enum bpf_map_type map_type,
>         attr.excl_prog_hash = ptr_to_u64(OPTS_GET(opts, excl_prog_hash, NULL));
>         attr.excl_prog_hash_size = OPTS_GET(opts, excl_prog_hash_size, 0);
>
> -       fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
> +       log_buf = OPTS_GET(opts, log_buf, NULL);
> +       if (log_buf && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
> +               memset(&common_attrs, 0, common_attrs_sz);
> +               common_attrs.log_buf = ptr_to_u64(log_buf);
> +               common_attrs.log_size = OPTS_GET(opts, log_size, 0);
> +               common_attrs.log_level = OPTS_GET(opts, log_level, 0);
> +               fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attrs, common_attrs_sz);
> +               OPTS_SET(opts, log_true_size, common_attrs.log_true_size);
> +       } else {
> +               fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
> +       }
>         return libbpf_err_errno(fd);
>  }
>
> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> index e983a3e40d612..77d475e7274a0 100644
> --- a/tools/lib/bpf/bpf.h
> +++ b/tools/lib/bpf/bpf.h
> @@ -57,16 +57,21 @@ struct bpf_map_create_opts {
>
>         const void *excl_prog_hash;
>         __u32 excl_prog_hash_size;
> +
> +       const char *log_buf;
> +       __u32 log_size;
> +       __u32 log_level;
> +       __u32 log_true_size;

I'm thinking that maybe we should have a separate struct that will
have these 4 fields, and pass a pointer to it. That way
bpf_map_create_opts can still be passed as const pointer, but libbpf
will still be able to write out log_true_size without violating
constness

and then we can reuse the same type (struct bpf_log? struct
bpf_log_buf? struct bpf_log_info? not sure, let's bikeshed) across
different commands that support passing log info through
bpf_common_attrs

>         size_t :0;
>  };
> -#define bpf_map_create_opts__last_field excl_prog_hash_size
> +#define bpf_map_create_opts__last_field log_true_size
>
>  LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
>                               const char *map_name,
>                               __u32 key_size,
>                               __u32 value_size,
>                               __u32 max_entries,
> -                             const struct bpf_map_create_opts *opts);
> +                             struct bpf_map_create_opts *opts);
>
>  struct bpf_prog_load_opts {
>         size_t sz; /* size of this struct for forward/backward compatibility */
> --
> 2.51.0
>

Re: [RFC PATCH bpf-next v3 09/10] libbpf: Add common attr support for map_create

[Leon Hwang]

On 7/10/25 07:08, Andrii Nakryiko wrote:
> On Thu, Oct 2, 2025 at 8:49 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>
>> With the previous commit adding common attribute support for
>> BPF_MAP_CREATE, it is now possible to retrieve detailed error messages
>> when map creation fails by using the 'log_buf' field from the common
>> attributes.
>>
>> Extend 'bpf_map_create_opts' with these new fields, 'log_buf', 'log_size'
>> , 'log_level' and 'log_true_size', allowing users to capture and inspect
>
> comma
>

Ack.

>> those log messages.
>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>> ---
>>  tools/lib/bpf/bpf.c | 17 +++++++++++++++--
>>  tools/lib/bpf/bpf.h |  9 +++++++--
>>  2 files changed, 22 insertions(+), 4 deletions(-)
>>
>> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
>> index 9cd79beb13a2d..ca66fcdb3f49f 100644
>> --- a/tools/lib/bpf/bpf.c
>> +++ b/tools/lib/bpf/bpf.c
>> @@ -203,10 +203,13 @@ int bpf_map_create(enum bpf_map_type map_type,
>>                    __u32 key_size,
>>                    __u32 value_size,
>>                    __u32 max_entries,
>> -                  const struct bpf_map_create_opts *opts)
>> +                  struct bpf_map_create_opts *opts)
>
> this is a breaking change, see below
>
>>  {
>>         const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size);
>> +       const size_t common_attrs_sz = sizeof(struct bpf_common_attr);
>> +       struct bpf_common_attr common_attrs;
>>         union bpf_attr attr;
>> +       const char *log_buf;
>>         int fd;
>>
>>         bump_rlimit_memlock();
>> @@ -239,7 +242,17 @@ int bpf_map_create(enum bpf_map_type map_type,
>>         attr.excl_prog_hash = ptr_to_u64(OPTS_GET(opts, excl_prog_hash, NULL));
>>         attr.excl_prog_hash_size = OPTS_GET(opts, excl_prog_hash_size, 0);
>>
>> -       fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
>> +       log_buf = OPTS_GET(opts, log_buf, NULL);
>> +       if (log_buf && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
>> +               memset(&common_attrs, 0, common_attrs_sz);
>> +               common_attrs.log_buf = ptr_to_u64(log_buf);
>> +               common_attrs.log_size = OPTS_GET(opts, log_size, 0);
>> +               common_attrs.log_level = OPTS_GET(opts, log_level, 0);
>> +               fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attrs, common_attrs_sz);
>> +               OPTS_SET(opts, log_true_size, common_attrs.log_true_size);
>> +       } else {
>> +               fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
>> +       }
>>         return libbpf_err_errno(fd);
>>  }
>>
>> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
>> index e983a3e40d612..77d475e7274a0 100644
>> --- a/tools/lib/bpf/bpf.h
>> +++ b/tools/lib/bpf/bpf.h
>> @@ -57,16 +57,21 @@ struct bpf_map_create_opts {
>>
>>         const void *excl_prog_hash;
>>         __u32 excl_prog_hash_size;
>> +
>> +       const char *log_buf;
>> +       __u32 log_size;
>> +       __u32 log_level;
>> +       __u32 log_true_size;
>
> I'm thinking that maybe we should have a separate struct that will
> have these 4 fields, and pass a pointer to it. That way
> bpf_map_create_opts can still be passed as const pointer, but libbpf
> will still be able to write out log_true_size without violating
> constness
>
> and then we can reuse the same type (struct bpf_log? struct
> bpf_log_buf? struct bpf_log_info? not sure, let's bikeshed) across
> different commands that support passing log info through
> bpf_common_attrs
>

Sure, that makes sense.

I add a new 'struct bpf_log_attr' to encapsulate these four fields, and
it works well in my local testing.

This also keeps bpf_map_create_opts const-safe while making it easier to
reuse the same structure for other commands using bpf_common_attrs.

Thanks,
Leon

[...]

[RFC PATCH bpf-next v3 10/10] selftests/bpf: Add cases to test map create failure log

[Leon Hwang]

As kernel is able to report log when fail to create map, add test cases
to check those logs.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 .../selftests/bpf/prog_tests/map_init.c       | 140 ++++++++++++++++++
 1 file changed, 140 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/map_init.c b/tools/testing/selftests/bpf/prog_tests/map_init.c
index 14a31109dd0e0..97a632ae7688f 100644
--- a/tools/testing/selftests/bpf/prog_tests/map_init.c
+++ b/tools/testing/selftests/bpf/prog_tests/map_init.c
@@ -212,3 +212,143 @@ void test_map_init(void)
 	if (test__start_subtest("pcpu_lru_map_init"))
 		test_pcpu_lru_map_init();
 }
+
+#define BPF_LOG_FIXED	8
+
+static void test_map_create(enum bpf_map_type map_type, const char *map_name,
+			    struct bpf_map_create_opts *opts, const char *exp_msg)
+{
+	char log_buf[128];
+	int fd;
+
+	log_buf[0] = '\0';
+	opts->log_buf = log_buf;
+	opts->log_size = sizeof(log_buf);
+	opts->log_level = BPF_LOG_FIXED;
+	fd = bpf_map_create(map_type, map_name, 4, 4, 1, opts);
+	if (!ASSERT_LT(fd, 0, "bpf_map_create")) {
+		close(fd);
+		return;
+	}
+
+	ASSERT_STREQ(log_buf, exp_msg, "log_buf");
+	ASSERT_EQ(opts->log_true_size, strlen(exp_msg) + 1, "log_true_size");
+}
+
+static void test_map_create_array(struct bpf_map_create_opts *opts, const char *exp_msg)
+{
+	test_map_create(BPF_MAP_TYPE_ARRAY, "test_map_create", opts, exp_msg);
+}
+
+static void test_invalid_vmlinux_value_type_id_struct_ops(void)
+{
+	const char *msg = "btf_vmlinux_value_type_id can only be used with struct_ops maps.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .btf_vmlinux_value_type_id = 1,
+	);
+
+	test_map_create_array(&opts, msg);
+}
+
+static void test_invalid_vmlinux_value_type_id_kv_type_id(void)
+{
+	const char *msg = "btf_vmlinux_value_type_id is mutually exclusive with btf_key_type_id and btf_value_type_id.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .btf_vmlinux_value_type_id = 1,
+		    .btf_key_type_id = 1,
+	);
+
+	test_map_create(BPF_MAP_TYPE_STRUCT_OPS, "test_map_create", &opts, msg);
+}
+
+static void test_invalid_value_type_id(void)
+{
+	const char *msg = "Invalid btf_value_type_id.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .btf_key_type_id = 1,
+	);
+
+	test_map_create_array(&opts, msg);
+}
+
+static void test_invalid_map_extra(void)
+{
+	const char *msg = "Invalid map_extra.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .map_extra = 1,
+	);
+
+	test_map_create_array(&opts, msg);
+}
+
+static void test_invalid_numa_node(void)
+{
+	const char *msg = "Invalid numa_node.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .map_flags = BPF_F_NUMA_NODE,
+		    .numa_node = 0xFF,
+	);
+
+	test_map_create_array(&opts, msg);
+}
+
+static void test_invalid_map_type(void)
+{
+	const char *msg = "Invalid map_type.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts);
+
+	test_map_create(__MAX_BPF_MAP_TYPE, "test_map_create", &opts, msg);
+}
+
+static void test_invalid_token_fd(void)
+{
+	const char *msg = "Invalid map_token_fd.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .map_flags = BPF_F_TOKEN_FD,
+		    .token_fd = 0xFF,
+	);
+
+	test_map_create_array(&opts, msg);
+}
+
+static void test_invalid_map_name(void)
+{
+	const char *msg = "Invalid map_name.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts);
+
+	test_map_create(BPF_MAP_TYPE_ARRAY, "test-!@#", &opts, msg);
+}
+
+static void test_invalid_btf_fd(void)
+{
+	const char *msg = "Invalid btf_fd.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .btf_fd = -1,
+		    .btf_key_type_id = 1,
+		    .btf_value_type_id = 1,
+	);
+
+	test_map_create_array(&opts, msg);
+}
+
+void test_map_create_failure(void)
+{
+	if (test__start_subtest("invalid_vmlinux_value_type_id_struct_ops"))
+		test_invalid_vmlinux_value_type_id_struct_ops();
+	if (test__start_subtest("invalid_vmlinux_value_type_id_kv_type_id"))
+		test_invalid_vmlinux_value_type_id_kv_type_id();
+	if (test__start_subtest("invalid_value_type_id"))
+		test_invalid_value_type_id();
+	if (test__start_subtest("invalid_map_extra"))
+		test_invalid_map_extra();
+	if (test__start_subtest("invalid_numa_node"))
+		test_invalid_numa_node();
+	if (test__start_subtest("invalid_map_type"))
+		test_invalid_map_type();
+	if (test__start_subtest("invalid_token_fd"))
+		test_invalid_token_fd();
+	if (test__start_subtest("invalid_map_name"))
+		test_invalid_map_name();
+	if (test__start_subtest("invalid_btf_fd"))
+		test_invalid_btf_fd();
+}
-- 
2.51.0

[syzbot ci] Re: bpf: Extend bpf syscall with common attributes support

[syzbot ci]

syzbot ci has tested the following series

[v3] bpf: Extend bpf syscall with common attributes support
https://lore.kernel.org/all/20251002154841.99348-1-leon.hwang@linux.dev
* [RFC PATCH bpf-next v3 01/10] bpf: Extend bpf syscall with common attributes support
* [RFC PATCH bpf-next v3 02/10] libbpf: Add support for extended bpf syscall
* [RFC PATCH bpf-next v3 03/10] bpf: Refactor reporting log_true_size for prog_load
* [RFC PATCH bpf-next v3 04/10] bpf: Add common attr support for prog_load
* [RFC PATCH bpf-next v3 05/10] bpf: Refactor reporting btf_log_true_size for btf_load
* [RFC PATCH bpf-next v3 06/10] bpf: Add common attr support for btf_load
* [RFC PATCH bpf-next v3 07/10] bpf: Add warnings for internal bugs in map_create
* [RFC PATCH bpf-next v3 08/10] bpf: Add common attr support for map_create
* [RFC PATCH bpf-next v3 09/10] libbpf: Add common attr support for map_create
* [RFC PATCH bpf-next v3 10/10] selftests/bpf: Add cases to test map create failure log

and found the following issue:
WARNING in map_create

Full report is available here:
https://ci.syzbot.org/series/71cc3485-c0bb-4e81-ab58-5a3a9b5a785c

***

WARNING in map_create

tree:      bpf-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/bpf/bpf-next.git
base:      4ef77dd584cfd915526328f516fec59e3a54d66e
arch:      amd64
compiler:  Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config:    https://ci.syzbot.org/builds/f37ac003-a816-47bc-ba46-fe604a617a93/config
C repro:   https://ci.syzbot.org/findings/bbf6cd34-205b-4dba-a0c6-10559caa70de/c_repro
syz repro: https://ci.syzbot.org/findings/bbf6cd34-205b-4dba-a0c6-10559caa70de/syz_repro

------------[ cut here ]------------
WARNING: CPU: 1 PID: 5987 at kernel/bpf/syscall.c:1470 map_create+0x12b3/0x17a0 kernel/bpf/syscall.c:1470
Modules linked in:
CPU: 1 UID: 0 PID: 5987 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:map_create+0x12b3/0x17a0 kernel/bpf/syscall.c:1470
Code: e8 82 26 ef ff 85 ed 74 29 e8 39 22 ef ff 48 8b 1c 24 48 89 df e8 5d c7 ab 02 4c 8b 64 24 08 e9 7b ff ff ff e8 1e 22 ef ff 90 <0f> 0b 90 e9 d4 f3 ff ff 48 8b 1c 24 48 89 df e8 d9 db 00 00 48 8b
RSP: 0018:ffffc90002d2fc20 EFLAGS: 00010293
RAX: ffffffff81d0a382 RBX: 0000000000000001 RCX: ffff888020e55640
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff888020e55640 R09: 0000000000000002
R10: 0000000000000021 R11: 0000000000000000 R12: 0000000000000000
R13: ffffc90002d2fd00 R14: 0000000000000000 R15: ffffc90002d2fd40
FS:  0000555569a59500(0000) GS:ffff8881a3c0f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8bbc12acf0 CR3: 000000010cfb0000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 __sys_bpf+0x966/0xe00 kernel/bpf/syscall.c:6305
 __do_sys_bpf kernel/bpf/syscall.c:6450 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6447 [inline]
 __x64_sys_bpf+0xba/0xd0 kernel/bpf/syscall.c:6447
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8bbc18eec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe6b9b55a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f8bbc3e5fa0 RCX: 00007f8bbc18eec9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f8bbc211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8bbc3e5fa0 R14: 00007f8bbc3e5fa0 R15: 0000000000000003
 </TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@syzkaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.

Re: [syzbot ci] Re: bpf: Extend bpf syscall with common attributes support

[Leon Hwang]

On 3/10/25 14:38, syzbot ci wrote:
> syzbot ci has tested the following series
> 
> [v3] bpf: Extend bpf syscall with common attributes support
> https://lore.kernel.org/all/20251002154841.99348-1-leon.hwang@linux.dev
> * [RFC PATCH bpf-next v3 01/10] bpf: Extend bpf syscall with common attributes support
> * [RFC PATCH bpf-next v3 02/10] libbpf: Add support for extended bpf syscall
> * [RFC PATCH bpf-next v3 03/10] bpf: Refactor reporting log_true_size for prog_load
> * [RFC PATCH bpf-next v3 04/10] bpf: Add common attr support for prog_load
> * [RFC PATCH bpf-next v3 05/10] bpf: Refactor reporting btf_log_true_size for btf_load
> * [RFC PATCH bpf-next v3 06/10] bpf: Add common attr support for btf_load
> * [RFC PATCH bpf-next v3 07/10] bpf: Add warnings for internal bugs in map_create
> * [RFC PATCH bpf-next v3 08/10] bpf: Add common attr support for map_create
> * [RFC PATCH bpf-next v3 09/10] libbpf: Add common attr support for map_create
> * [RFC PATCH bpf-next v3 10/10] selftests/bpf: Add cases to test map create failure log
> 
> and found the following issue:
> WARNING in map_create
> 
The added WARNINGs in map_create will be dropped in the next revision.

Thanks,
Leon

[...]