On 2026/1/16 09:03, Andrii Nakryiko wrote:
> 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?
>
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_diuzgwakfsj...@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
>>
