On 5/2/26 03:48, Andrii Nakryiko wrote:

On Mon, Feb 2, 2026 at 6:43 AM Leon Hwang [off-list ref] wrote:

quoted

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_log_opts with the following fields:
log_buf, log_size, log_level, and log_true_size.

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

Signed-off-by: Leon Hwang <redacted>
---
 tools/lib/bpf/bpf.c | 16 +++++++++++++++-
 tools/lib/bpf/bpf.h | 17 ++++++++++++++++-
 2 files changed, 31 insertions(+), 2 deletions(-)

LGTM

Acked-by: Andrii Nakryiko <andrii@kernel.org>

Thanks for your review.

quoted

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 9d8740761b7a..0c3e40844d80 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c

@@ -209,6 +209,9 @@ 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 attr_common_sz = sizeof(struct bpf_common_attr);
+       struct bpf_common_attr attr_common;
+       struct bpf_log_opts *log_opts;
        union bpf_attr attr;
        int fd;

@@ -242,7 +245,18 @@ 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_opts = OPTS_GET(opts, log_opts, NULL);
+       if (log_opts && feat_supported(NULL, FEAT_BPF_SYSCALL_COMMON_ATTRS)) {
+               memset(&attr_common, 0, attr_common_sz);
+               attr_common.log_buf = ptr_to_u64(OPTS_GET(log_opts, log_buf, NULL));
+               attr_common.log_size = OPTS_GET(log_opts, log_size, 0);
+               attr_common.log_level = OPTS_GET(log_opts, log_level, 0);
+               fd = sys_bpf_ext_fd(BPF_MAP_CREATE, &attr, attr_sz, &attr_common, attr_common_sz);
+               OPTS_SET(log_opts, log_true_size, attr_common.log_true_size);
+       } else {
+               fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, attr_sz);
+               OPTS_SET(log_opts, log_true_size, 0);
+       }
        return libbpf_err_errno(fd);
 }

diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 2c8e88ddb674..59673f094f86 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_log_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;

please mention in the comment here that this is an out parameter set
by the kernel

Ack.

I'll add a comment in the next revision.

Thanks,
Leon

quoted

+
+       size_t :0;
+};
+#define bpf_log_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_log_opts *log_opts;
+
        size_t :0;
 };
-#define bpf_map_create_opts__last_field excl_prog_hash_size
+#define bpf_map_create_opts__last_field log_opts

 LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
                              const char *map_name,
--

2.52.0