On Mon, Jan 12, 2026 at 6:59 AM Leon Hwang <[email protected]> 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 <[email protected]>
> ---
> 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
>
