[PATCH bpf-next v5 0/9] bpf: Extend BPF syscall with common attributes support

[PATCH bpf-next v5 0/9] bpf: Extend BPF syscall with common attributes support

[Leon Hwang]

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

This patch series 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.

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

Changes:
v4 -> v5:
* Rework reporting 'log_true_size' for prog_load, btf_load, and map_create
  (per Alexei).

RFC v3 -> v4:
* Drop RFC.
* Address comments from Andrii:
  * Add parentheses in 'sys_bpf_ext()'.
  * Avoid creating new fd in 'probe_sys_bpf_ext()'.
  * Add a new struct to wrap log fields in libbpf.
* Address comments from Alexei:
  * Do not skip writing to user space when log_true_size is zero.
  * Do not use 'bool' arguments.
  * Drop the adding WARN_ON_ONCE()'s.

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 -EUSERS 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.

Leon Hwang (9):
  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 syscall common attributes support for prog_load
  bpf: Refactor reporting btf_log_true_size for btf_load
  bpf: Add syscall common attributes support for btf_load
  bpf: Add syscall common attributes support for map_create
  libbpf: Add common attr support for map_create
  selftests/bpf: Add tests to verify map create failure log

 include/linux/bpf.h                           |  19 +-
 include/linux/bpf_verifier.h                  |  17 ++
 include/linux/btf.h                           |   3 +-
 include/linux/syscalls.h                      |   3 +-
 include/uapi/linux/bpf.h                      |   8 +
 kernel/bpf/btf.c                              |  32 +---
 kernel/bpf/log.c                              | 103 +++++++++++
 kernel/bpf/syscall.c                          | 122 ++++++++++---
 kernel/bpf/verifier.c                         |  19 +-
 tools/include/uapi/linux/bpf.h                |   8 +
 tools/lib/bpf/bpf.c                           |  49 ++++-
 tools/lib/bpf/bpf.h                           |  17 +-
 tools/lib/bpf/features.c                      |   8 +
 tools/lib/bpf/libbpf_internal.h               |   3 +
 .../selftests/bpf/prog_tests/map_init.c       | 168 ++++++++++++++++++
 15 files changed, 518 insertions(+), 61 deletions(-)

--
2.52.0

[PATCH bpf-next v5 1/9] 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           | 25 +++++++++++++++++++++----
 tools/include/uapi/linux/bpf.h |  8 ++++++++
 4 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index cf84d98964b2..729659202d77 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -937,7 +937,8 @@ 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 2a2ade4be60f..2f83eca0a357 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -986,6 +986,7 @@ enum bpf_cmd {
 	BPF_PROG_STREAM_READ_BY_FD,
 	BPF_PROG_ASSOC_STRUCT_OPS,
 	__MAX_BPF_CMD,
+	BPF_COMMON_ATTRS = 1 << 16, /* Indicate carrying bpf_common_attr. */
 };
 
 enum bpf_map_type {
@@ -1491,6 +1492,13 @@ 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 ecc0929ce462..af703f7ea58e 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -6163,8 +6163,10 @@ static int prog_assoc_struct_ops(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_attr;
 	union bpf_attr attr;
 	int err;
 
@@ -6178,6 +6180,20 @@ 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_attr, 0, sizeof(common_attr));
+	if (cmd & BPF_COMMON_ATTRS) {
+		err = bpf_check_uarg_tail_zero(uattr_common, sizeof(common_attr), size_common);
+		if (err)
+			return err;
+
+		cmd &= ~BPF_COMMON_ATTRS;
+		size_common = min_t(u32, size_common, sizeof(common_attr));
+		if (copy_from_bpfptr(&common_attr, uattr_common, size_common) != 0)
+			return -EFAULT;
+	} else {
+		size_common = 0;
+	}
+
 	err = security_bpf(cmd, &attr, size, uattr.is_kernel);
 	if (err < 0)
 		return err;
@@ -6313,9 +6329,10 @@ 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,
@@ -6346,7 +6363,7 @@ 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 b816bc53d2e1..2b05c689d51a 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -986,6 +986,7 @@ enum bpf_cmd {
 	BPF_PROG_STREAM_READ_BY_FD,
 	BPF_PROG_ASSOC_STRUCT_OPS,
 	__MAX_BPF_CMD,
+	BPF_COMMON_ATTRS = 1 << 16, /* Indicate carrying bpf_common_attr. */
 };
 
 enum bpf_map_type {
@@ -1491,6 +1492,13 @@ 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 {
-- 
2.52.0

[PATCH bpf-next v5 2/9] 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             | 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..d44e667aaf02 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_attr,
+			      unsigned int size_common)
+{
+	cmd = common_attr ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS);
+	return syscall(__NR_bpf, cmd, attr, size, common_attr, 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_attr,
+				 unsigned int size_common)
+{
+	int fd;
+
+	fd = sys_bpf_ext(cmd, attr, size, common_attr, 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

[PATCH bpf-next v5 3/9] bpf: Refactor reporting log_true_size for prog_load

[Leon Hwang]

The next commit will add support for reporting logs via extended common
attributes, including 'log_true_size'.

To prepare for that, refactor the 'log_true_size' reporting logic by
introducing a new struct bpf_log_attr to encapsulate log-related behavior:

 * bpf_prog_load_log_attr_init(): initialize the log fields, which will
   support extended common attributes in the next commit.
 * bpf_log_attr_finalize(): handle log finalization and write back
   'log_true_size' to userspace.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/bpf.h          | 19 ++++++++++++++++-
 include/linux/bpf_verifier.h | 11 ++++++++++
 kernel/bpf/log.c             | 40 ++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c         |  9 +++++++-
 kernel/bpf/verifier.c        | 19 ++++++-----------
 5 files changed, 83 insertions(+), 15 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5936f8e2996f..3a525a7e8747 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2867,8 +2867,25 @@ int bpf_get_file_flag(int flags);
 int bpf_check_uarg_tail_zero(bpfptr_t uaddr, size_t expected_size,
 			     size_t actual_size);
 
+struct bpf_attrs {
+	const void *attr;
+	bpfptr_t uattr;
+	u32 size;
+};
+
+static inline void bpf_attrs_init(struct bpf_attrs *attrs, const void *attr, bpfptr_t uattr,
+				  u32 size)
+{
+	memset(attrs, 0, sizeof(*attrs));
+	attrs->attr = attr;
+	attrs->uattr = uattr;
+	attrs->size = size;
+}
+
 /* verify correctness of eBPF program */
-int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size);
+struct bpf_log_attr;
+int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr,
+	      struct bpf_log_attr *log_attr);
 
 #ifndef CONFIG_BPF_JIT_ALWAYS_ON
 void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 130bcbd66f60..4c9632c40059 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -631,6 +631,17 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
 	return log && log->level;
 }
 
+struct bpf_log_attr {
+	u64 log_buf;
+	u32 log_size;
+	u32 log_level;
+	struct bpf_attrs *attrs;
+	u32 offsetof_log_true_size;
+};
+
+int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
+int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
+
 #define BPF_MAX_SUBPROGS 256
 
 struct bpf_subprog_arg_info {
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index a0c3b35de2ce..457b724c4176 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -863,3 +863,43 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
 	}
 	print_verifier_state(env, vstate, frameno, false);
 }
+
+static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
+			     u32 log_size, u32 log_level, int offsetof_log_true_size)
+{
+	memset(log_attr, 0, sizeof(*log_attr));
+	log_attr->log_buf = log_buf;
+	log_attr->log_size = log_size;
+	log_attr->log_level = log_level;
+	log_attr->attrs = attrs;
+	log_attr->offsetof_log_true_size = offsetof_log_true_size;
+	return 0;
+}
+
+int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs)
+{
+	const union bpf_attr *attr = attrs->attr;
+
+	return bpf_log_attr_init(log_attr, attrs, attr->log_buf, attr->log_size, attr->log_level,
+				 offsetof(union bpf_attr, log_true_size));
+}
+
+int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log)
+{
+	u32 log_true_size, off;
+	size_t size;
+	int err;
+
+	if (!log)
+		return 0;
+
+	err = bpf_vlog_finalize(log, &log_true_size);
+
+	size = sizeof(log_true_size);
+	off = log_attr->offsetof_log_true_size;
+	if (log_attr->attrs && log_attr->attrs->size >= off + size &&
+	    copy_to_bpfptr_offset(log_attr->attrs->uattr, off, &log_true_size, size))
+		err = -EFAULT;
+
+	return err;
+}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index af703f7ea58e..0b389bc6add8 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2871,6 +2871,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	struct bpf_prog *prog, *dst_prog = NULL;
 	struct btf *attach_btf = NULL;
 	struct bpf_token *token = NULL;
+	struct bpf_log_attr log_attr;
+	struct bpf_attrs attrs;
 	bool bpf_cap;
 	int err;
 	char license[128];
@@ -3082,8 +3084,13 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	if (err)
 		goto free_prog_sec;
 
+	bpf_attrs_init(&attrs, attr, uattr, uattr_size);
+	err = bpf_prog_load_log_attr_init(&log_attr, &attrs);
+	if (err < 0)
+		goto free_used_maps;
+
 	/* run eBPF verifier */
-	err = bpf_check(&prog, attr, uattr, uattr_size);
+	err = bpf_check(&prog, attr, uattr, &log_attr);
 	if (err < 0)
 		goto free_used_maps;
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 53635ea2e41b..921a7b6a6686 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -25106,12 +25106,12 @@ 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,
+	      struct bpf_log_attr *log_attr)
 {
 	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);
@@ -25158,9 +25158,9 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	/* user could have requested verbose verifier output
 	 * and supplied buffer to store the verification trace
 	 */
-	ret = bpf_vlog_init(&env->log, attr->log_level,
-			    (char __user *) (unsigned long) attr->log_buf,
-			    attr->log_size);
+	ret = bpf_vlog_init(&env->log, log_attr->log_level,
+			    u64_to_user_ptr(log_attr->log_buf),
+			    log_attr->log_size);
 	if (ret)
 		goto err_unlock;
 
@@ -25310,17 +25310,10 @@ 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_log_attr_finalize(log_attr, &env->log);
 	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;
 
-- 
2.52.0

[PATCH bpf-next v5 4/9] bpf: Add syscall common attributes 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>
---
 include/linux/bpf_verifier.h |  4 +++-
 kernel/bpf/log.c             | 29 ++++++++++++++++++++++++++---
 kernel/bpf/syscall.c         |  9 ++++++---
 3 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 4c9632c40059..da2d37ca60e7 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -637,9 +637,11 @@ struct bpf_log_attr {
 	u32 log_level;
 	struct bpf_attrs *attrs;
 	u32 offsetof_log_true_size;
+	struct bpf_attrs *attrs_common;
 };
 
-int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
+int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
+				struct bpf_attrs *attrs_common);
 int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
 
 #define BPF_MAX_SUBPROGS 256
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 457b724c4176..eba60a13e244 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -865,23 +865,41 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
 }
 
 static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
-			     u32 log_size, u32 log_level, int offsetof_log_true_size)
+			     u32 log_size, u32 log_level, int offsetof_log_true_size,
+			     struct bpf_attrs *attrs_common)
 {
+	const struct bpf_common_attr *common_attr = attrs_common ? attrs_common->attr : NULL;
+
 	memset(log_attr, 0, sizeof(*log_attr));
 	log_attr->log_buf = log_buf;
 	log_attr->log_size = log_size;
 	log_attr->log_level = log_level;
 	log_attr->attrs = attrs;
 	log_attr->offsetof_log_true_size = offsetof_log_true_size;
+	log_attr->attrs_common = attrs_common;
+
+	if (log_buf && common_attr && common_attr->log_buf &&
+		(log_buf != common_attr->log_buf ||
+		 log_size != common_attr->log_size ||
+		 log_level != common_attr->log_level))
+		return -EUSERS;
+
+	if (!log_buf && common_attr && common_attr->log_buf) {
+		log_attr->log_buf = common_attr->log_buf;
+		log_attr->log_size = common_attr->log_size;
+		log_attr->log_level = common_attr->log_level;
+	}
+
 	return 0;
 }
 
-int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs)
+int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
+				struct bpf_attrs *attrs_common)
 {
 	const union bpf_attr *attr = attrs->attr;
 
 	return bpf_log_attr_init(log_attr, attrs, attr->log_buf, attr->log_size, attr->log_level,
-				 offsetof(union bpf_attr, log_true_size));
+				 offsetof(union bpf_attr, log_true_size), attrs_common);
 }
 
 int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log)
@@ -901,5 +919,10 @@ int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log
 	    copy_to_bpfptr_offset(log_attr->attrs->uattr, off, &log_true_size, size))
 		err = -EFAULT;
 
+	off = offsetof(struct bpf_common_attr, log_true_size);
+	if (log_attr->attrs_common && log_attr->attrs_common->size >= off + size &&
+	    copy_to_bpfptr_offset(log_attr->attrs_common->uattr, off, &log_true_size, size))
+		err = -EFAULT;
+
 	return err;
 }
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0b389bc6add8..f369b9ec9d60 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2865,7 +2865,8 @@ static int bpf_prog_mark_insn_arrays_ready(struct bpf_prog *prog)
 /* 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, u32 uattr_size,
+			 struct bpf_attrs *common_attrs)
 {
 	enum bpf_prog_type type = attr->prog_type;
 	struct bpf_prog *prog, *dst_prog = NULL;
@@ -3085,7 +3086,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 		goto free_prog_sec;
 
 	bpf_attrs_init(&attrs, attr, uattr, uattr_size);
-	err = bpf_prog_load_log_attr_init(&log_attr, &attrs);
+	err = bpf_prog_load_log_attr_init(&log_attr, &attrs, common_attrs);
 	if (err < 0)
 		goto free_used_maps;
 
@@ -6174,6 +6175,7 @@ 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_attr;
+	struct bpf_attrs common_attrs;
 	union bpf_attr attr;
 	int err;
 
@@ -6225,7 +6227,8 @@ 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);
+		bpf_attrs_init(&common_attrs, &common_attr, uattr_common, size_common);
+		err = bpf_prog_load(&attr, uattr, size, &common_attrs);
 		break;
 	case BPF_OBJ_PIN:
 		err = bpf_obj_pin(&attr);
-- 
2.52.0

[PATCH bpf-next v5 5/9] 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/bpf_verifier.h |  1 +
 include/linux/btf.h          |  3 ++-
 kernel/bpf/btf.c             | 32 +++++++++-----------------------
 kernel/bpf/log.c             |  9 +++++++++
 kernel/bpf/syscall.c         | 10 +++++++++-
 5 files changed, 30 insertions(+), 25 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index da2d37ca60e7..44dd60de1966 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -642,6 +642,7 @@ struct bpf_log_attr {
 
 int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
 				struct bpf_attrs *attrs_common);
+int bpf_btf_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
 int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
 
 #define BPF_MAX_SUBPROGS 256
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 691f09784933..df04843a4635 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -144,7 +144,8 @@ 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);
+struct bpf_log_attr;
+int btf_new_fd(const union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_attr *log_attr);
 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 539c9fdea41d..f9973f12a482 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5745,25 +5745,11 @@ 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(const union bpf_attr *attr, bpfptr_t uattr,
+			     struct bpf_log_attr *log_attr)
 {
 	bpfptr_t btf_data = make_bpfptr(attr->btf, uattr.is_kernel);
-	char __user *log_ubuf = u64_to_user_ptr(attr->btf_log_buf);
+	char __user *log_ubuf = u64_to_user_ptr(log_attr->log_buf);
 	struct btf_struct_metas *struct_meta_tab;
 	struct btf_verifier_env *env = NULL;
 	struct btf *btf = NULL;
@@ -5780,8 +5766,8 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat
 	/* user could have requested verbose verifier output
 	 * and supplied buffer to store the verification trace
 	 */
-	err = bpf_vlog_init(&env->log, attr->btf_log_level,
-			    log_ubuf, attr->btf_log_size);
+	err = bpf_vlog_init(&env->log, log_attr->log_level,
+			    log_ubuf, log_attr->log_size);
 	if (err)
 		goto errout_free;
 
@@ -5841,7 +5827,7 @@ 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_log_attr_finalize(log_attr, &env->log);
 	if (err)
 		goto errout_free;
 
@@ -5853,7 +5839,7 @@ 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_log_attr_finalize(log_attr, &env->log);
 	if (ret)
 		err = ret;
 errout_free:
@@ -8017,12 +8003,12 @@ 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(const union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_attr *log_attr)
 {
 	struct btf *btf;
 	int ret;
 
-	btf = btf_parse(attr, uattr, uattr_size);
+	btf = btf_parse(attr, uattr, log_attr);
 	if (IS_ERR(btf))
 		return PTR_ERR(btf);
 
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index eba60a13e244..96df089a2c89 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -902,6 +902,15 @@ int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs
 				 offsetof(union bpf_attr, log_true_size), attrs_common);
 }
 
+int bpf_btf_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs)
+{
+	const union bpf_attr *attr = attrs->attr;
+
+	return bpf_log_attr_init(log_attr, attrs, attr->btf_log_buf, attr->btf_log_size,
+				 attr->btf_log_level, offsetof(union bpf_attr, btf_log_true_size),
+				 NULL);
+}
+
 int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log)
 {
 	u32 log_true_size, off;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index f369b9ec9d60..8382fafc8d17 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -5436,6 +5436,9 @@ static int bpf_obj_get_info_by_fd(const union bpf_attr *attr,
 static int bpf_btf_load(const union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
 {
 	struct bpf_token *token = NULL;
+	struct bpf_log_attr log_attr;
+	struct bpf_attrs attrs;
+	int err;
 
 	if (CHECK_ATTR(BPF_BTF_LOAD))
 		return -EINVAL;
@@ -5443,6 +5446,11 @@ static int bpf_btf_load(const union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_
 	if (attr->btf_flags & ~BPF_F_TOKEN_FD)
 		return -EINVAL;
 
+	bpf_attrs_init(&attrs, attr, uattr, uattr_size);
+	err = bpf_btf_load_log_attr_init(&log_attr, &attrs);
+	if (err)
+		return err;
+
 	if (attr->btf_flags & BPF_F_TOKEN_FD) {
 		token = bpf_token_get_from_fd(attr->btf_token_fd);
 		if (IS_ERR(token))
@@ -5460,7 +5468,7 @@ 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, &log_attr);
 }
 
 #define BPF_BTF_GET_FD_BY_ID_LAST_FIELD fd_by_id_token_fd
-- 
2.52.0

[PATCH bpf-next v5 6/9] bpf: Add syscall common attributes support for btf_load

[Leon Hwang]

Since bpf_log_attr_init() now supports struct bpf_common_attr, pass the
common attributes to it to enable syscall common attributes support for
BPF_BTF_LOAD.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/bpf_verifier.h | 3 ++-
 kernel/bpf/log.c             | 5 +++--
 kernel/bpf/syscall.c         | 8 +++++---
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 44dd60de1966..9022e4f515f9 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -642,7 +642,8 @@ struct bpf_log_attr {
 
 int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
 				struct bpf_attrs *attrs_common);
-int bpf_btf_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
+int bpf_btf_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
+			       struct bpf_attrs *attrs_common);
 int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
 
 #define BPF_MAX_SUBPROGS 256
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 96df089a2c89..0dba014ca055 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -902,13 +902,14 @@ int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs
 				 offsetof(union bpf_attr, log_true_size), attrs_common);
 }
 
-int bpf_btf_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs)
+int bpf_btf_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
+			       struct bpf_attrs *attrs_common)
 {
 	const union bpf_attr *attr = attrs->attr;
 
 	return bpf_log_attr_init(log_attr, attrs, attr->btf_log_buf, attr->btf_log_size,
 				 attr->btf_log_level, offsetof(union bpf_attr, btf_log_true_size),
-				 NULL);
+				 attrs_common);
 }
 
 int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 8382fafc8d17..d0440e640e40 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -5433,7 +5433,8 @@ 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(const union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size,
+			struct bpf_attrs *common_attrs)
 {
 	struct bpf_token *token = NULL;
 	struct bpf_log_attr log_attr;
@@ -5447,7 +5448,7 @@ static int bpf_btf_load(const union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_
 		return -EINVAL;
 
 	bpf_attrs_init(&attrs, attr, uattr, uattr_size);
-	err = bpf_btf_load_log_attr_init(&log_attr, &attrs);
+	err = bpf_btf_load_log_attr_init(&log_attr, &attrs, common_attrs);
 	if (err)
 		return err;
 
@@ -6281,7 +6282,8 @@ 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);
+		bpf_attrs_init(&common_attrs, &common_attr, uattr_common, size_common);
+		err = bpf_btf_load(&attr, uattr, size, &common_attrs);
 		break;
 	case BPF_BTF_GET_FD_BY_ID:
 		err = bpf_btf_get_fd_by_id(&attr);
-- 
2.52.0

[PATCH bpf-next v5 7/9] bpf: Add syscall common attributes support for map_create

[Leon Hwang]

Currently, many BPF_MAP_CREATE failures return -EINVAL without providing
any explanation to userspace.

With extended BPF syscall support, detailed error messages can now be
reported via the log buffer, allowing users to understand the specific
reason for a failed map creation.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/bpf_verifier.h |  2 ++
 kernel/bpf/log.c             | 30 +++++++++++++++++
 kernel/bpf/syscall.c         | 65 ++++++++++++++++++++++++++++++------
 3 files changed, 87 insertions(+), 10 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 9022e4f515f9..280beca480ea 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -644,6 +644,8 @@ int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs
 				struct bpf_attrs *attrs_common);
 int bpf_btf_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
 			       struct bpf_attrs *attrs_common);
+struct bpf_verifier_log *bpf_log_attr_create_vlog(struct bpf_log_attr *log_attr,
+						  struct bpf_attrs *attrs_common);
 int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
 
 #define BPF_MAX_SUBPROGS 256
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 0dba014ca055..6586d752970f 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -912,6 +912,36 @@ int bpf_btf_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *
 				 attrs_common);
 }
 
+struct bpf_verifier_log *bpf_log_attr_create_vlog(struct bpf_log_attr *log_attr,
+						  struct bpf_attrs *attrs_common)
+{
+	const struct bpf_common_attr *common_attr = attrs_common->attr;
+	struct bpf_verifier_log *log;
+	int err;
+
+	memset(log_attr, 0, sizeof(*log_attr));
+	log_attr->log_buf = common_attr->log_buf;
+	log_attr->log_size = common_attr->log_size;
+	log_attr->log_level = common_attr->log_level;
+	log_attr->attrs_common = attrs_common;
+
+	if (!log_attr->log_buf)
+		return NULL;
+
+	log = kzalloc(sizeof(*log), GFP_KERNEL);
+	if (!log)
+		return ERR_PTR(-ENOMEM);
+
+	err = bpf_vlog_init(log, log_attr->log_level, u64_to_user_ptr(log_attr->log_buf),
+			    log_attr->log_size);
+	if (err) {
+		kfree(log);
+		return ERR_PTR(err);
+	}
+
+	return log;
+}
+
 int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log)
 {
 	u32 log_true_size, off;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index d0440e640e40..52e1ab142da9 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1370,7 +1370,7 @@ static bool bpf_net_capable(void)
 
 #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_verifier_log *log)
 {
 	const struct bpf_map_ops *ops;
 	struct bpf_token *token = NULL;
@@ -1382,8 +1382,10 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 	int err;
 
 	err = CHECK_ATTR(BPF_MAP_CREATE);
-	if (err)
+	if (err) {
+		bpf_log(log, "Invalid attr.\n");
 		return -EINVAL;
+	}
 
 	/* 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
@@ -1392,17 +1394,25 @@ 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)
@@ -1410,13 +1420,17 @@ 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 (!ops)
@@ -1434,8 +1448,10 @@ 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
@@ -1518,8 +1534,10 @@ 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);
@@ -1542,6 +1560,7 @@ 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;
 		}
@@ -1569,6 +1588,7 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 		bpfptr_t uprog_hash = make_bpfptr(attr->excl_prog_hash, uattr.is_kernel);
 
 		if (attr->excl_prog_hash_size != SHA256_DIGEST_SIZE) {
+			bpf_log(log, "Invalid excl_prog_hash_size.\n");
 			err = -EINVAL;
 			goto free_map;
 		}
@@ -1584,6 +1604,7 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 			goto free_map;
 		}
 	} else if (attr->excl_prog_hash_size) {
+		bpf_log(log, "Invalid excl_prog_hash_size.\n");
 		err = -EINVAL;
 		goto free_map;
 	}
@@ -1622,6 +1643,29 @@ static int map_create(union bpf_attr *attr, bpfptr_t uattr)
 	return err;
 }
 
+static int map_create(union bpf_attr *attr, bpfptr_t uattr, struct bpf_attrs *common_attrs)
+{
+	struct bpf_verifier_log *log;
+	struct bpf_log_attr log_attr;
+	int err, ret;
+
+	log = bpf_log_attr_create_vlog(&log_attr, common_attrs);
+	if (IS_ERR(log))
+		return PTR_ERR(log);
+
+	err = __map_create(attr, uattr, log);
+	if (err >= 0)
+		goto free;
+
+	ret = bpf_log_attr_finalize(&log_attr, log);
+	if (ret)
+		err = ret;
+
+free:
+	kfree(log);
+	return err;
+}
+
 void bpf_map_inc(struct bpf_map *map)
 {
 	atomic64_inc(&map->refcnt);
@@ -6218,7 +6262,8 @@ 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);
+		bpf_attrs_init(&common_attrs, &common_attr, uattr_common, size_common);
+		err = map_create(&attr, uattr, &common_attrs);
 		break;
 	case BPF_MAP_LOOKUP_ELEM:
 		err = map_lookup_elem(&attr);
-- 
2.52.0

[PATCH bpf-next v5 8/9] libbpf: Add common attr support for map_create

[Leon Hwang]

With the previous commit adding common attribute support for
BPF_MAP_CREATE, users can now retrieve detailed error messages when map
creation fails via the log_buf field.

Introduce struct bpf_syscall_common_attr_opts with the following fields:
log_buf, log_size, log_level, and log_true_size.

Extend bpf_map_create_opts with a new field common_attr_opts, allowing
users to capture and inspect log messages on map creation failures.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 tools/lib/bpf/bpf.c | 15 ++++++++++++++-
 tools/lib/bpf/bpf.h | 17 ++++++++++++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index d44e667aaf02..d65df1b7b2be 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -207,6 +207,9 @@ int bpf_map_create(enum bpf_map_type map_type,
 		   const struct bpf_map_create_opts *opts)
 {
 	const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size);
+	const size_t common_attr_sz = sizeof(struct bpf_common_attr);
+	struct bpf_syscall_common_attr_opts *common_attr_opts;
+	struct bpf_common_attr common_attr;
 	union bpf_attr attr;
 	int fd;
 
@@ -240,7 +243,17 @@ 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);
+	common_attr_opts = OPTS_GET(opts, common_attr_opts, NULL);
+	if (common_attr_opts && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
+		memset(&common_attr, 0, common_attr_sz);
+		common_attr.log_buf = ptr_to_u64(OPTS_GET(common_attr_opts, log_buf, NULL));
+		common_attr.log_size = OPTS_GET(common_attr_opts, log_size, 0);
+		common_attr.log_level = OPTS_GET(common_attr_opts, log_level, 0);
+		fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attr, common_attr_sz);
+		OPTS_SET(common_attr_opts, log_true_size, common_attr.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 2c8e88ddb674..c4a26e6b71ea 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -37,6 +37,18 @@ extern "C" {
 
 LIBBPF_API int libbpf_set_memlock_rlim(size_t memlock_bytes);
 
+struct bpf_syscall_common_attr_opts {
+	size_t sz; /* size of this struct for forward/backward compatibility */
+
+	char *log_buf;
+	__u32 log_size;
+	__u32 log_level;
+	__u32 log_true_size;
+
+	size_t :0;
+};
+#define bpf_syscall_common_attr_opts__last_field log_true_size
+
 struct bpf_map_create_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
 
@@ -57,9 +69,12 @@ struct bpf_map_create_opts {
 
 	const void *excl_prog_hash;
 	__u32 excl_prog_hash_size;
+
+	struct bpf_syscall_common_attr_opts *common_attr_opts;
+
 	size_t :0;
 };
-#define bpf_map_create_opts__last_field excl_prog_hash_size
+#define bpf_map_create_opts__last_field common_attr_opts
 
 LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
 			      const char *map_name,
-- 
2.52.0

[PATCH bpf-next v5 9/9] selftests/bpf: Add tests to verify map create failure log

[Leon Hwang]

Add tests to verify that the kernel reports the expected error messages
when map creation fails.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 .../selftests/bpf/prog_tests/map_init.c       | 168 ++++++++++++++++++
 1 file changed, 168 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/map_init.c b/tools/testing/selftests/bpf/prog_tests/map_init.c
index 14a31109dd0e..824e2bea74bf 100644
--- a/tools/testing/selftests/bpf/prog_tests/map_init.c
+++ b/tools/testing/selftests/bpf/prog_tests/map_init.c
@@ -212,3 +212,171 @@ 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)
+{
+	const int key_size = 4, value_size = 4, max_entries = 1;
+	char log_buf[128];
+	int fd;
+	LIBBPF_OPTS(bpf_syscall_common_attr_opts, copts);
+
+	log_buf[0] = '\0';
+	copts.log_buf = log_buf;
+	copts.log_size = sizeof(log_buf);
+	copts.log_level = BPF_LOG_FIXED;
+	opts->common_attr_opts = &copts;
+	fd = bpf_map_create(map_type, map_name, key_size, value_size, max_entries, opts);
+	if (!ASSERT_LT(fd, 0, "bpf_map_create")) {
+		close(fd);
+		return;
+	}
+
+	ASSERT_STREQ(log_buf, exp_msg, "log_buf");
+	ASSERT_EQ(copts.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);
+}
+
+static void test_excl_prog_hash_size_1(void)
+{
+	const char *msg = "Invalid excl_prog_hash_size.\n";
+	const char *hash = "DEADCODE";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .excl_prog_hash = hash,
+	);
+
+	test_map_create_array(&opts, msg);
+}
+
+static void test_excl_prog_hash_size_2(void)
+{
+	const char *msg = "Invalid excl_prog_hash_size.\n";
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		    .excl_prog_hash_size = 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();
+	if (test__start_subtest("invalid_excl_prog_hash_size_1"))
+		test_excl_prog_hash_size_1();
+	if (test__start_subtest("invalid_excl_prog_hash_size_2"))
+		test_excl_prog_hash_size_2();
+}
-- 
2.52.0

Re: [PATCH bpf-next v5 2/9] libbpf: Add support for extended bpf syscall

[Andrii Nakryiko]

On Mon, Jan 12, 2026 at 6:58 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             | 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..d44e667aaf02 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_attr,

nit: kernel uses consistent attr_common/size_common pattern, but here
you are inverting attr_common -> common_attr, let's not?

> +                             unsigned int size_common)
> +{
> +       cmd = common_attr ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS);
> +       return syscall(__NR_bpf, cmd, attr, size, common_attr, 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_attr,
> +                                unsigned int size_common)
> +{
> +       int fd;
> +
> +       fd = sys_bpf_ext(cmd, attr, size, common_attr, 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);

hm... close can change errno, this is fragile. If fd >= 0, something
is wrong with our detection, just return error right away?

> +       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,

"extended syscall" is a bit vague... We specifically detect common
attrs support, maybe say that?

> +       },
>  };
>
>  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_BPF_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
>

Re: [PATCH bpf-next v5 4/9] bpf: Add syscall common attributes support for prog_load

[Andrii Nakryiko]

On Mon, Jan 12, 2026 at 6:59 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.

why use this special error code that we don't seem to use in BPF
subsystem at all? What's wrong with -EINVAL. This shouldn't be an easy
mistake to do, tbh.

>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
>  include/linux/bpf_verifier.h |  4 +++-
>  kernel/bpf/log.c             | 29 ++++++++++++++++++++++++++---
>  kernel/bpf/syscall.c         |  9 ++++++---
>  3 files changed, 35 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 4c9632c40059..da2d37ca60e7 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -637,9 +637,11 @@ struct bpf_log_attr {
>         u32 log_level;
>         struct bpf_attrs *attrs;
>         u32 offsetof_log_true_size;
> +       struct bpf_attrs *attrs_common;
>  };
>
> -int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
> +int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
> +                               struct bpf_attrs *attrs_common);
>  int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
>
>  #define BPF_MAX_SUBPROGS 256
> diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
> index 457b724c4176..eba60a13e244 100644
> --- a/kernel/bpf/log.c
> +++ b/kernel/bpf/log.c
> @@ -865,23 +865,41 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
>  }
>
>  static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
> -                            u32 log_size, u32 log_level, int offsetof_log_true_size)
> +                            u32 log_size, u32 log_level, int offsetof_log_true_size,
> +                            struct bpf_attrs *attrs_common)
>  {
> +       const struct bpf_common_attr *common_attr = attrs_common ? attrs_common->attr : NULL;
> +

There is something to be said about naming choices here :) it's easy
to get lost in attrs_common being actually bpf_attrs, which contains
attr field, which is actually of bpf_common_attr type... It's a bit
disorienting. :)

>         memset(log_attr, 0, sizeof(*log_attr));
>         log_attr->log_buf = log_buf;
>         log_attr->log_size = log_size;
>         log_attr->log_level = log_level;
>         log_attr->attrs = attrs;
>         log_attr->offsetof_log_true_size = offsetof_log_true_size;
> +       log_attr->attrs_common = attrs_common;
> +
> +       if (log_buf && common_attr && common_attr->log_buf &&
> +               (log_buf != common_attr->log_buf ||
> +                log_size != common_attr->log_size ||
> +                log_level != common_attr->log_level))
> +               return -EUSERS;
> +
> +       if (!log_buf && common_attr && common_attr->log_buf) {
> +               log_attr->log_buf = common_attr->log_buf;
> +               log_attr->log_size = common_attr->log_size;
> +               log_attr->log_level = common_attr->log_level;
> +       }
> +
>         return 0;
>  }
>

[...]

Re: [PATCH bpf-next v5 8/9] libbpf: Add common attr support for map_create

[Andrii Nakryiko]

On Mon, Jan 12, 2026 at 6:59 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
> With the previous commit adding common attribute support for
> BPF_MAP_CREATE, users can now retrieve detailed error messages when map
> creation fails via the log_buf field.
>
> Introduce struct bpf_syscall_common_attr_opts with the following fields:
> log_buf, log_size, log_level, and log_true_size.
>
> Extend bpf_map_create_opts with a new field common_attr_opts, allowing
> users to capture and inspect log messages on map creation failures.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
>  tools/lib/bpf/bpf.c | 15 ++++++++++++++-
>  tools/lib/bpf/bpf.h | 17 ++++++++++++++++-
>  2 files changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index d44e667aaf02..d65df1b7b2be 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -207,6 +207,9 @@ int bpf_map_create(enum bpf_map_type map_type,
>                    const struct bpf_map_create_opts *opts)
>  {
>         const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size);
> +       const size_t common_attr_sz = sizeof(struct bpf_common_attr);
> +       struct bpf_syscall_common_attr_opts *common_attr_opts;
> +       struct bpf_common_attr common_attr;
>         union bpf_attr attr;
>         int fd;
>
> @@ -240,7 +243,17 @@ 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);
> +       common_attr_opts = OPTS_GET(opts, common_attr_opts, NULL);
> +       if (common_attr_opts && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
> +               memset(&common_attr, 0, common_attr_sz);
> +               common_attr.log_buf = ptr_to_u64(OPTS_GET(common_attr_opts, log_buf, NULL));
> +               common_attr.log_size = OPTS_GET(common_attr_opts, log_size, 0);
> +               common_attr.log_level = OPTS_GET(common_attr_opts, log_level, 0);
> +               fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attr, common_attr_sz);
> +               OPTS_SET(common_attr_opts, log_true_size, common_attr.log_true_size);
> +       } else {
> +               fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);

OPTS_SET(log_true_size) to zero here, maybe?

> +       }
>         return libbpf_err_errno(fd);
>  }
>
> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> index 2c8e88ddb674..c4a26e6b71ea 100644
> --- a/tools/lib/bpf/bpf.h
> +++ b/tools/lib/bpf/bpf.h
> @@ -37,6 +37,18 @@ extern "C" {
>
>  LIBBPF_API int libbpf_set_memlock_rlim(size_t memlock_bytes);
>
> +struct bpf_syscall_common_attr_opts {
> +       size_t sz; /* size of this struct for forward/backward compatibility */
> +
> +       char *log_buf;
> +       __u32 log_size;
> +       __u32 log_level;
> +       __u32 log_true_size;
> +
> +       size_t :0;
> +};
> +#define bpf_syscall_common_attr_opts__last_field log_true_size

see below, let's drop this struct and just add these 4 fields directly
to bpf_map_create_opts

> +
>  struct bpf_map_create_opts {
>         size_t sz; /* size of this struct for forward/backward compatibility */
>
> @@ -57,9 +69,12 @@ struct bpf_map_create_opts {
>
>         const void *excl_prog_hash;
>         __u32 excl_prog_hash_size;
> +
> +       struct bpf_syscall_common_attr_opts *common_attr_opts;

maybe let's just add those log_xxx fields here directly? This whole
extra bpf_syscall_common_attr_opts pointer and struct seems like a
cumbersome API.

> +
>         size_t :0;
>  };
> -#define bpf_map_create_opts__last_field excl_prog_hash_size
> +#define bpf_map_create_opts__last_field common_attr_opts
>
>  LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
>                               const char *map_name,
> --
> 2.52.0
>

Re: [PATCH bpf-next v5 2/9] libbpf: Add support for extended bpf syscall

[Leon Hwang]

On 2026/1/16 08:42, Andrii Nakryiko wrote:
> On Mon, Jan 12, 2026 at 6:58 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             | 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..d44e667aaf02 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_attr,
> 
> nit: kernel uses consistent attr_common/size_common pattern, but here
> you are inverting attr_common -> common_attr, let's not?
> 

Ack.

I'll keep the same pattern.

>> +                             unsigned int size_common)
>> +{
>> +       cmd = common_attr ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS);
>> +       return syscall(__NR_bpf, cmd, attr, size, common_attr, 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_attr,
>> +                                unsigned int size_common)
>> +{
>> +       int fd;
>> +
>> +       fd = sys_bpf_ext(cmd, attr, size, common_attr, 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);
> 
> hm... close can change errno, this is fragile. If fd >= 0, something
> is wrong with our detection, just return error right away?
> 

How about capture errno before closing?

err = errno;
if (fd >= 0)
	close(fd);
return err = EFAULT;

Then, we can wrap all details in probe_sys_bpf_ext().

>> +       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,
> 
> "extended syscall" is a bit vague... We specifically detect common
> attrs support, maybe say that?
> 

Ack.

I'll update it to "BPF syscall common attributes support."

>> +       },
>>  };
>>
>>  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_BPF_COMMON_ATTRS ?
> 

FEAT_BPF_SYSCALL_COMMON_ATTRS seems more accurate.

Thanks,
Leon

>>         __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
>>

Re: [PATCH bpf-next v5 4/9] bpf: Add syscall common attributes support for prog_load

[Leon Hwang]

On 2026/1/16 08:54, Andrii Nakryiko wrote:
> On Mon, Jan 12, 2026 at 6:59 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.
> 
> why use this special error code that we don't seem to use in BPF
> subsystem at all? What's wrong with -EINVAL. This shouldn't be an easy
> mistake to do, tbh.
> 

-EUSERS was suggested by Alexei.

However, I agree with you that it is better to use -EINVAL here.

>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>> ---
>>  include/linux/bpf_verifier.h |  4 +++-
>>  kernel/bpf/log.c             | 29 ++++++++++++++++++++++++++---
>>  kernel/bpf/syscall.c         |  9 ++++++---
>>  3 files changed, 35 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
>> index 4c9632c40059..da2d37ca60e7 100644
>> --- a/include/linux/bpf_verifier.h
>> +++ b/include/linux/bpf_verifier.h
>> @@ -637,9 +637,11 @@ struct bpf_log_attr {
>>         u32 log_level;
>>         struct bpf_attrs *attrs;
>>         u32 offsetof_log_true_size;
>> +       struct bpf_attrs *attrs_common;
>>  };
>>
>> -int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
>> +int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
>> +                               struct bpf_attrs *attrs_common);
>>  int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
>>
>>  #define BPF_MAX_SUBPROGS 256
>> diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
>> index 457b724c4176..eba60a13e244 100644
>> --- a/kernel/bpf/log.c
>> +++ b/kernel/bpf/log.c
>> @@ -865,23 +865,41 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
>>  }
>>
>>  static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
>> -                            u32 log_size, u32 log_level, int offsetof_log_true_size)
>> +                            u32 log_size, u32 log_level, int offsetof_log_true_size,
>> +                            struct bpf_attrs *attrs_common)
>>  {
>> +       const struct bpf_common_attr *common_attr = attrs_common ? attrs_common->attr : NULL;
>> +
> 
> There is something to be said about naming choices here :) it's easy
> to get lost in attrs_common being actually bpf_attrs, which contains
> attr field, which is actually of bpf_common_attr type... It's a bit
> disorienting. :)
> 

I see your point about the naming being confusing.

The original intent of 'struct bpf_attrs' was to provide a shared
wrapper for both 'union bpf_attr' and 'struct bpf_common_attr'. However,
I agree that using 'attrs_common' here makes the layering harder to follow.

If that approach is undesirable, how about introducing a dedicated
structure instead, e.g.:

struct bpf_common_attrs {
	const struct bpf_common_attr *attr;
	bpfptr_t uattr;
	u32 size;
};

This should make the ownership and intent clearer.

Thanks,
Leon

[...]

Re: [PATCH bpf-next v5 8/9] libbpf: Add common attr support for map_create

[Leon Hwang]

On 2026/1/16 09:03, Andrii Nakryiko wrote:
> On Mon, Jan 12, 2026 at 6:59 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>
>> With the previous commit adding common attribute support for
>> BPF_MAP_CREATE, users can now retrieve detailed error messages when map
>> creation fails via the log_buf field.
>>
>> Introduce struct bpf_syscall_common_attr_opts with the following fields:
>> log_buf, log_size, log_level, and log_true_size.
>>
>> Extend bpf_map_create_opts with a new field common_attr_opts, allowing
>> users to capture and inspect log messages on map creation failures.
>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>> ---
>>  tools/lib/bpf/bpf.c | 15 ++++++++++++++-
>>  tools/lib/bpf/bpf.h | 17 ++++++++++++++++-
>>  2 files changed, 30 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
>> index d44e667aaf02..d65df1b7b2be 100644
>> --- a/tools/lib/bpf/bpf.c
>> +++ b/tools/lib/bpf/bpf.c
>> @@ -207,6 +207,9 @@ int bpf_map_create(enum bpf_map_type map_type,
>>                    const struct bpf_map_create_opts *opts)
>>  {
>>         const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size);
>> +       const size_t common_attr_sz = sizeof(struct bpf_common_attr);
>> +       struct bpf_syscall_common_attr_opts *common_attr_opts;
>> +       struct bpf_common_attr common_attr;
>>         union bpf_attr attr;
>>         int fd;
>>
>> @@ -240,7 +243,17 @@ 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);
>> +       common_attr_opts = OPTS_GET(opts, common_attr_opts, NULL);
>> +       if (common_attr_opts && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
>> +               memset(&common_attr, 0, common_attr_sz);
>> +               common_attr.log_buf = ptr_to_u64(OPTS_GET(common_attr_opts, log_buf, NULL));
>> +               common_attr.log_size = OPTS_GET(common_attr_opts, log_size, 0);
>> +               common_attr.log_level = OPTS_GET(common_attr_opts, log_level, 0);
>> +               fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attr, common_attr_sz);
>> +               OPTS_SET(common_attr_opts, log_true_size, common_attr.log_true_size);
>> +       } else {
>> +               fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
> 
> OPTS_SET(log_true_size) to zero here, maybe?
> 

Unnecessary, but ok to do it.

>> +       }
>>         return libbpf_err_errno(fd);
>>  }
>>
>> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
>> index 2c8e88ddb674..c4a26e6b71ea 100644
>> --- a/tools/lib/bpf/bpf.h
>> +++ b/tools/lib/bpf/bpf.h
>> @@ -37,6 +37,18 @@ extern "C" {
>>
>>  LIBBPF_API int libbpf_set_memlock_rlim(size_t memlock_bytes);
>>
>> +struct bpf_syscall_common_attr_opts {
>> +       size_t sz; /* size of this struct for forward/backward compatibility */
>> +
>> +       char *log_buf;
>> +       __u32 log_size;
>> +       __u32 log_level;
>> +       __u32 log_true_size;
>> +
>> +       size_t :0;
>> +};
>> +#define bpf_syscall_common_attr_opts__last_field log_true_size
> 
> see below, let's drop this struct and just add these 4 fields directly
> to bpf_map_create_opts
> 
>> +
>>  struct bpf_map_create_opts {
>>         size_t sz; /* size of this struct for forward/backward compatibility */
>>
>> @@ -57,9 +69,12 @@ struct bpf_map_create_opts {
>>
>>         const void *excl_prog_hash;
>>         __u32 excl_prog_hash_size;
>> +
>> +       struct bpf_syscall_common_attr_opts *common_attr_opts;
> 
> maybe let's just add those log_xxx fields here directly? This whole
> extra bpf_syscall_common_attr_opts pointer and struct seems like a
> cumbersome API.
> 

Oops... This struct was suggested by the v3 discussion [1].

This struct was used to report 'log_true_size' without changing
'bpf_map_create()' API.

Links
[1]
https://lore.kernel.org/bpf/CAEf4Bzaw9cboFSf1OXmD84S7pKaeyj=bcQg_diUzGwAkFsjUgg@mail.gmail.com/

Thanks,
Leon

>> +
>>         size_t :0;
>>  };
>> -#define bpf_map_create_opts__last_field excl_prog_hash_size
>> +#define bpf_map_create_opts__last_field common_attr_opts
>>
>>  LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
>>                               const char *map_name,
>> --
>> 2.52.0
>>

Re: [PATCH bpf-next v5 2/9] libbpf: Add support for extended bpf syscall

[Andrii Nakryiko]

On Fri, Jan 16, 2026 at 5:58 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
>
>
> On 2026/1/16 08:42, Andrii Nakryiko wrote:
> > On Mon, Jan 12, 2026 at 6:58 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             | 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..d44e667aaf02 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_attr,
> >
> > nit: kernel uses consistent attr_common/size_common pattern, but here
> > you are inverting attr_common -> common_attr, let's not?
> >
>
> Ack.
>
> I'll keep the same pattern.
>
> >> +                             unsigned int size_common)
> >> +{
> >> +       cmd = common_attr ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS);
> >> +       return syscall(__NR_bpf, cmd, attr, size, common_attr, 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_attr,
> >> +                                unsigned int size_common)
> >> +{
> >> +       int fd;
> >> +
> >> +       fd = sys_bpf_ext(cmd, attr, size, common_attr, 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);
> >
> > hm... close can change errno, this is fragile. If fd >= 0, something
> > is wrong with our detection, just return error right away?
> >
>
> How about capture errno before closing?
>
> err = errno;
> if (fd >= 0)
>         close(fd);
> return err = EFAULT;

not sure what this code is trying to do, but yes, preserving errno is
one way to fix an immediate problem.

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) { }

>
> Then, we can wrap all details in probe_sys_bpf_ext().
>
> >> +       return errno == EFAULT;
> >> +}
> >> +

[...]

Re: [PATCH bpf-next v5 4/9] bpf: Add syscall common attributes support for prog_load

[Andrii Nakryiko]

On Fri, Jan 16, 2026 at 6:10 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
>
>
> On 2026/1/16 08:54, Andrii Nakryiko wrote:
> > On Mon, Jan 12, 2026 at 6:59 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.
> >
> > why use this special error code that we don't seem to use in BPF
> > subsystem at all? What's wrong with -EINVAL. This shouldn't be an easy
> > mistake to do, tbh.
> >
>
> -EUSERS was suggested by Alexei.
>
> However, I agree with you that it is better to use -EINVAL here.

I don't know what the context was, if you can find it that would be
great. Maybe special error makes sense for what Alexei had in mind.

>
> >>
> >> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> >> ---
> >>  include/linux/bpf_verifier.h |  4 +++-
> >>  kernel/bpf/log.c             | 29 ++++++++++++++++++++++++++---
> >>  kernel/bpf/syscall.c         |  9 ++++++---
> >>  3 files changed, 35 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> >> index 4c9632c40059..da2d37ca60e7 100644
> >> --- a/include/linux/bpf_verifier.h
> >> +++ b/include/linux/bpf_verifier.h
> >> @@ -637,9 +637,11 @@ struct bpf_log_attr {
> >>         u32 log_level;
> >>         struct bpf_attrs *attrs;
> >>         u32 offsetof_log_true_size;
> >> +       struct bpf_attrs *attrs_common;
> >>  };
> >>
> >> -int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
> >> +int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
> >> +                               struct bpf_attrs *attrs_common);
> >>  int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
> >>
> >>  #define BPF_MAX_SUBPROGS 256
> >> diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
> >> index 457b724c4176..eba60a13e244 100644
> >> --- a/kernel/bpf/log.c
> >> +++ b/kernel/bpf/log.c
> >> @@ -865,23 +865,41 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
> >>  }
> >>
> >>  static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
> >> -                            u32 log_size, u32 log_level, int offsetof_log_true_size)
> >> +                            u32 log_size, u32 log_level, int offsetof_log_true_size,
> >> +                            struct bpf_attrs *attrs_common)
> >>  {
> >> +       const struct bpf_common_attr *common_attr = attrs_common ? attrs_common->attr : NULL;
> >> +
> >
> > There is something to be said about naming choices here :) it's easy
> > to get lost in attrs_common being actually bpf_attrs, which contains
> > attr field, which is actually of bpf_common_attr type... It's a bit
> > disorienting. :)
> >
>
> I see your point about the naming being confusing.
>
> The original intent of 'struct bpf_attrs' was to provide a shared
> wrapper for both 'union bpf_attr' and 'struct bpf_common_attr'. However,
> I agree that using 'attrs_common' here makes the layering harder to follow.
>
> If that approach is undesirable, how about introducing a dedicated
> structure instead, e.g.:
>
> struct bpf_common_attrs {
>         const struct bpf_common_attr *attr;
>         bpfptr_t uattr;
>         u32 size;
> };
>
> This should make the ownership and intent clearer.

I don't know and it's not that important, as it's pretty content. But
I'd just try to shorten some names, maybe just "common" for internal
helpers would make sense. common->log_buf, seems to work.

>
> Thanks,
> Leon
>
> [...]
>

Re: [PATCH bpf-next v5 8/9] libbpf: Add common attr support for map_create

[Andrii Nakryiko]

On Fri, Jan 16, 2026 at 6:17 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
>
>
> On 2026/1/16 09:03, Andrii Nakryiko wrote:
> > On Mon, Jan 12, 2026 at 6:59 AM Leon Hwang <leon.hwang@linux.dev> wrote:
> >>
> >> With the previous commit adding common attribute support for
> >> BPF_MAP_CREATE, users can now retrieve detailed error messages when map
> >> creation fails via the log_buf field.
> >>
> >> Introduce struct bpf_syscall_common_attr_opts with the following fields:
> >> log_buf, log_size, log_level, and log_true_size.
> >>
> >> Extend bpf_map_create_opts with a new field common_attr_opts, allowing
> >> users to capture and inspect log messages on map creation failures.
> >>
> >> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> >> ---
> >>  tools/lib/bpf/bpf.c | 15 ++++++++++++++-
> >>  tools/lib/bpf/bpf.h | 17 ++++++++++++++++-
> >>  2 files changed, 30 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> >> index d44e667aaf02..d65df1b7b2be 100644
> >> --- a/tools/lib/bpf/bpf.c
> >> +++ b/tools/lib/bpf/bpf.c
> >> @@ -207,6 +207,9 @@ int bpf_map_create(enum bpf_map_type map_type,
> >>                    const struct bpf_map_create_opts *opts)
> >>  {
> >>         const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash_size);
> >> +       const size_t common_attr_sz = sizeof(struct bpf_common_attr);
> >> +       struct bpf_syscall_common_attr_opts *common_attr_opts;
> >> +       struct bpf_common_attr common_attr;
> >>         union bpf_attr attr;
> >>         int fd;
> >>
> >> @@ -240,7 +243,17 @@ 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);
> >> +       common_attr_opts = OPTS_GET(opts, common_attr_opts, NULL);
> >> +       if (common_attr_opts && feat_supported(NULL, FEAT_EXTENDED_SYSCALL)) {
> >> +               memset(&common_attr, 0, common_attr_sz);
> >> +               common_attr.log_buf = ptr_to_u64(OPTS_GET(common_attr_opts, log_buf, NULL));
> >> +               common_attr.log_size = OPTS_GET(common_attr_opts, log_size, 0);
> >> +               common_attr.log_level = OPTS_GET(common_attr_opts, log_level, 0);
> >> +               fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &common_attr, common_attr_sz);
> >> +               OPTS_SET(common_attr_opts, log_true_size, common_attr.log_true_size);
> >> +       } else {
> >> +               fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
> >
> > OPTS_SET(log_true_size) to zero here, maybe?
> >
>
> Unnecessary, but ok to do it.
>
> >> +       }
> >>         return libbpf_err_errno(fd);
> >>  }
> >>
> >> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> >> index 2c8e88ddb674..c4a26e6b71ea 100644
> >> --- a/tools/lib/bpf/bpf.h
> >> +++ b/tools/lib/bpf/bpf.h
> >> @@ -37,6 +37,18 @@ extern "C" {
> >>
> >>  LIBBPF_API int libbpf_set_memlock_rlim(size_t memlock_bytes);
> >>
> >> +struct bpf_syscall_common_attr_opts {
> >> +       size_t sz; /* size of this struct for forward/backward compatibility */
> >> +
> >> +       char *log_buf;
> >> +       __u32 log_size;
> >> +       __u32 log_level;
> >> +       __u32 log_true_size;
> >> +
> >> +       size_t :0;
> >> +};
> >> +#define bpf_syscall_common_attr_opts__last_field log_true_size
> >
> > see below, let's drop this struct and just add these 4 fields directly
> > to bpf_map_create_opts
> >
> >> +
> >>  struct bpf_map_create_opts {
> >>         size_t sz; /* size of this struct for forward/backward compatibility */
> >>
> >> @@ -57,9 +69,12 @@ struct bpf_map_create_opts {
> >>
> >>         const void *excl_prog_hash;
> >>         __u32 excl_prog_hash_size;
> >> +
> >> +       struct bpf_syscall_common_attr_opts *common_attr_opts;
> >
> > maybe let's just add those log_xxx fields here directly? This whole
> > extra bpf_syscall_common_attr_opts pointer and struct seems like a
> > cumbersome API.
> >
>
> Oops... This struct was suggested by the v3 discussion [1].
>
> This struct was used to report 'log_true_size' without changing
> 'bpf_map_create()' API.
>

Ah, I already forgot. log_true_size being an output parameter here...
Sigh. I don't like the verboseness of bpf_syscall_common_attr_opts and
"common_attr_opts" and all that stuff...

What if we make it struct bpf_log_opts {} and keep it log-specific?

> Links
> [1]
> https://lore.kernel.org/bpf/CAEf4Bzaw9cboFSf1OXmD84S7pKaeyj=bcQg_diUzGwAkFsjUgg@mail.gmail.com/
>
> Thanks,
> Leon
>
> >> +
> >>         size_t :0;
> >>  };
> >> -#define bpf_map_create_opts__last_field excl_prog_hash_size
> >> +#define bpf_map_create_opts__last_field common_attr_opts
> >>
> >>  LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
> >>                               const char *map_name,
> >> --
> >> 2.52.0
> >>
>