On 5/2/26 03:48, Andrii Nakryiko wrote:
> On Mon, Feb 2, 2026 at 6:43 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_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 <[email protected]>
>> ---
>> tools/lib/bpf/bpf.c | 16 +++++++++++++++-
>> tools/lib/bpf/bpf.h | 17 ++++++++++++++++-
>> 2 files changed, 31 insertions(+), 2 deletions(-)
>>
>
> LGTM
>
> Acked-by: Andrii Nakryiko <[email protected]>
>
Thanks for your review.
>> 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
>> +
>> + 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
>>
