linux-kernel - Re: [PATCH bpf-next v2 14/18] libbpf: add btf type hash lookup support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <22e15dd2-8564-4e71-ab77-8b436870850d@linux.dev>
Date: Tue, 15 Jul 2025 12:40:55 +0800
From: Menglong Dong <menglong.dong@...ux.dev>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>,
 Menglong Dong <menglong8.dong@...il.com>
Cc: alexei.starovoitov@...il.com, rostedt@...dmis.org, jolsa@...nel.org,
 bpf@...r.kernel.org, Menglong Dong <dongml2@...natelecom.cn>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 14/18] libbpf: add btf type hash lookup
 support


On 7/15/25 06:07, Andrii Nakryiko wrote:
> On Thu, Jul 3, 2025 at 5:22 AM Menglong Dong <menglong8.dong@...il.com> wrote:
>> For now, the libbpf find the btf type id by loop all the btf types and
>> compare its name, which is inefficient if we have many functions to
>> lookup.
>>
>> We add the "use_hash" to the function args of find_kernel_btf_id() to
>> indicate if we should lookup the btf type id by hash. The hash table will
>> be initialized if it has not yet.
> Or we could build hashtable-based index outside of struct btf for a
> specific use case, because there is no one perfect hashtable-based
> indexing that can be done generically (e.g., just by name, or
> name+kind, or kind+name, or some more complicated lookup key) and
> cover all potential use cases. I'd prefer not to get into a problem of
> defining and building indexes and leave it to callers (even if the
> caller is other part of libbpf itself).


I think that works. We can define a global hash table in libbpf.c,
and add all the btf type to it. I'll redesign this part, and make it
separate with the btf.

Thanks!
Menglong Dong

>> Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
>> ---
>>   tools/lib/bpf/btf.c      | 102 +++++++++++++++++++++++++++++++++++++++
>>   tools/lib/bpf/btf.h      |   6 +++
>>   tools/lib/bpf/libbpf.c   |  37 +++++++++++---
>>   tools/lib/bpf/libbpf.map |   3 ++
>>   4 files changed, 140 insertions(+), 8 deletions(-)
>>
> [...]
>