From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-187.mta0.migadu.com (out-187.mta0.migadu.com [91.218.175.187]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B731C15C4 for ; Thu, 29 Feb 2024 00:25:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709166322; cv=none; b=RXpQlQ0bAt2Y8tlSr62YWcV0+JjZxGnYJopTjeEomuAiet8Iql+tXglhWg2GUiIUQOBGusqqdRs08vd9wvajbAd2cHgCf/o0wN5CytoArZP0g5B+uYxcuuZCSJ3MnrYRZwI+ujk5m2uxUrCVuJ+mGA1iBAGYC+6aypfrHPf0O6E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709166322; c=relaxed/simple; bh=09ZyQcc8vmp2J/NnUnJZEGeuQc2j16all3RRMUnPbfc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=frfmpHBpedT+bwVN6rub5dcBkQPHS/EHEAkpIb299OA4QD/vL4nJzAXMQA3QoznHiNvHBnzjl81Pw9R572ycUgnKigP4TjDccveVRuM+VrzrJEbVu0SpGKTGLrQyVhW4fi4mnCm5lvbtEt8AmK5tFoPFvFrECLAE0ZRO5dFfp7E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=CutVQ3x7; arc=none smtp.client-ip=91.218.175.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="CutVQ3x7" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1709166317; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=47VHirmAlpCNhGZCZtGQlr9g0StUrS/wARmnIszDyFc=; b=CutVQ3x7cXhZhiASqXfX4N95iQOteKVwyhTfPIWt7m9xPaIY3VT2fvYqA05oYndkvcwft4 vj7P33gHSDmilIwGOTdDo3XAq5Cplmp/BR/6IIqLQprBXFx5Jmwe36NdUqiW6YZYJNKFz/ dXsvMJt9L055EJG/QSNwuWKNImhZMVw= Date: Wed, 28 Feb 2024 16:25:08 -0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v1 7/8] libbpf: sync progs autoload with maps autocreate for struct_ops maps Content-Language: en-US To: Andrii Nakryiko , Eduard Zingerman Cc: andrii@kernel.org, daniel@iogearbox.net, kernel-team@fb.com, yonghong.song@linux.dev, void@manifault.com, bpf@vger.kernel.org, ast@kernel.org References: <20240227204556.17524-1-eddyz87@gmail.com> <20240227204556.17524-8-eddyz87@gmail.com> <1e95162a-a8d7-44e6-bc63-999df8cae987@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 2/28/24 3:55 PM, Andrii Nakryiko wrote: > On Tue, Feb 27, 2024 at 6:11 PM Martin KaFai Lau wrote: >> >> On 2/27/24 12:45 PM, Eduard Zingerman wrote: >>> Make bpf_map__set_autocreate() for struct_ops maps toggle autoload >>> state for referenced programs. >>> >>> E.g. for the BPF code below: >>> >>> SEC("struct_ops/test_1") int BPF_PROG(foo) { ... } >>> SEC("struct_ops/test_2") int BPF_PROG(bar) { ... } >>> >>> SEC(".struct_ops.link") >>> struct test_ops___v1 A = { >>> .foo = (void *)foo >>> }; >>> >>> SEC(".struct_ops.link") >>> struct test_ops___v2 B = { >>> .foo = (void *)foo, >>> .bar = (void *)bar, >>> }; >>> >>> And the following libbpf API calls: >>> >>> bpf_map__set_autocreate(skel->maps.A, true); >>> bpf_map__set_autocreate(skel->maps.B, false); >>> >>> The autoload would be enabled for program 'foo' and disabled for >>> program 'bar'. >>> >>> Do not apply such toggling if program autoload state is set by a call >>> to bpf_program__set_autoload(). >>> >>> Signed-off-by: Eduard Zingerman >>> --- >>> tools/lib/bpf/libbpf.c | 35 ++++++++++++++++++++++++++++++++++- >>> 1 file changed, 34 insertions(+), 1 deletion(-) >>> >>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c >>> index b39d3f2898a1..1ea3046724f8 100644 >>> --- a/tools/lib/bpf/libbpf.c >>> +++ b/tools/lib/bpf/libbpf.c >>> @@ -446,13 +446,18 @@ struct bpf_program { >>> struct bpf_object *obj; >>> >>> int fd; >>> - bool autoload; >>> + bool autoload:1; >>> + bool autoload_user_set:1; >>> bool autoattach; >>> bool sym_global; >>> bool mark_btf_static; >>> enum bpf_prog_type type; >>> enum bpf_attach_type expected_attach_type; >>> int exception_cb_idx; >>> + /* total number of struct_ops maps with autocreate == true >>> + * that reference this program >>> + */ >>> + __u32 struct_ops_refs; >> >> Instead of adding struct_ops_refs and autoload_user_set, >> >> for BPF_PROG_TYPE_STRUCT_OPS, how about deciding to load it or not by checking >> prog->attach_btf_id (non zero) alone. The prog->attach_btf_id is now decided at >> load time and is only set if it is used by at least one autocreate map, if I >> read patch 2 & 3 correctly. >> >> Meaning ignore prog->autoload*. Load the struct_ops prog as long as it is used >> by one struct_ops map with autocreate == true. >> >> If the struct_ops prog is not used in any struct_ops map, the bpf prog cannot be >> loaded even the autoload is set. If bpf prog is used in a struct_ops map and its >> autoload is set to false, the struct_ops map will be in broken state. Thus, > > We can easily detect this condition and report meaningful error. > >> prog->autoload does not fit very well with struct_ops prog and may as well >> depend on whether the struct_ops prog is used by a struct_ops map alone? > > I think it's probably fine from a usability standpoint to disable > loading the BPF program if its struct_ops map was explicitly set to > not auto-create. It's a bit of deviation from other program types, but > in practice this logic will make it easier for users. > > One question I have, though, is whether we should report as an error a > stand-alone struct_ops BPF program that is not used from any > struct_ops map? Or should we load it nevertheless? Or should we > silently not load it? I think the libbpf could report an error if the prog is not used in any struct_ops map at the source code level, not sure if it is useful. However, it probably should not report error if that struct_ops map (where the prog is resided) does not have autocreate set to true. If a BPF program is not used in any struct_ops map, it cannot be loaded anyway because the prog->attach_btf_id is not set. If libbpf tries to load the prog, the kernel will reject it also. I think it may be a question on whether it is the user intention of not loading the prog if the prog is not used in any struct_ops map. I tend to think it is the user intention of not loading it in this case. SEC("struct_ops/test1") int BPF_PROG(test1) { ... } SEC("struct_ops/test2") int BPF_PROG(test2) { ... } SEC("?.struct_ops.link") struct some_ops___v1 a = { .test1 = test1 } SEC("?.struct_ops.link") struct some_ops___v2 b = { .test1 = test1, .test2 = test2, } In the above, the userspace may try to load with a newer some_ops___v2 first, failed and then try a lower version some_ops___v1 and then succeeded. The test2 prog will not be used and not expected to be loaded. > > I feel like silently not loading is the worst behavior here. So either > loading it anyway or reporting an error would be my preference, > probably.