From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9B5351DFE08; Fri, 13 Dec 2024 15:17:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734103062; cv=none; b=RoK6+3rXXHxX+JGg7nuYISxLmHFmczxCq9wLZkOnVnCkVSg+U9eAgDeyfhFP/rYMpcHOeD/8/W8PuJ3fJFtUvUA8eyGa4dHSa28oYZB85BFNQUaW05KyPLMHu6SeU+/7Pt91BFSpOAm9Ly+GTyhgQlcTodohBS+//yjbjkEYdQU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734103062; c=relaxed/simple; bh=NiDfmXtW+uz6UI4KoebVo4W4iFF81SHUU7f57O7/WlI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=G3G4Vu1AReyfKgsyJxsu/tbZGrEEnmfgO8u/7fMdvh9DSu3sRRVjtt4SnrGOX0+dwvbu2Wprf9yYKPHoWqajvPn1ORj9my3JtD3eQQu9LE4FeA7Y74S+XEGAXMZwxinxgXYsYaUkwrzCx0UwDY0kXyKGLO5BCEyucmlR6VKn3bY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CyPk+qYP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CyPk+qYP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5340FC4CED0; Fri, 13 Dec 2024 15:17:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1734103062; bh=NiDfmXtW+uz6UI4KoebVo4W4iFF81SHUU7f57O7/WlI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=CyPk+qYPhrrRkKRa8SO1JC2T0u/u4WMi3valxYwWnbohsJJGc67pRQvnRAkPEVudV pHzsNRpbUmpLXyp5uPBOPMk84vf97JaR7sZ0RWcXjU2Nn388hzqVE3qrqrGGBQs56t LGAtaWgdBltGsAPDrMh9QO5Nv9gH/ENWQIj4cK4yQ0v8gKVw/iaqEh7MbdgVPHNZ7Q /Q8sbY5PVubIk080Ba2+pyv0l83Uf9+RnI0qdCtv6/pVzB6eGxd/tbtT1ByitPqjiE VmVd0Ymqqxw4A/MNCiQr8d1OzGYeEym7PsSNG4WC7NCcXqwJ/rnZESHHTykVnWn8SA BIRIBr5GgBTlA== Message-ID: <7fa902e5-0916-4bc9-b1e0-2729903d3de0@kernel.org> Date: Fri, 13 Dec 2024 15:17:36 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v4 3/4] bpftool: btf: Support dumping a specific types from file To: Daniel Xu , hawk@kernel.org, kuba@kernel.org, andrii@kernel.org, john.fastabend@gmail.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net Cc: martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, andrii.nakryiko@gmail.com, antony@phenome.org, toke@kernel.org References: <5ec7617fd9c28ff721947aceb80937dc10fca770.1734052995.git.dxu@dxuuu.xyz> From: Quentin Monnet Content-Language: en-GB In-Reply-To: <5ec7617fd9c28ff721947aceb80937dc10fca770.1734052995.git.dxu@dxuuu.xyz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 2024-12-12 18:24 UTC-0700 ~ Daniel Xu > Some projects, for example xdp-tools [0], prefer to check in a minimized > vmlinux.h rather than the complete file which can get rather large. > > However, when you try to add a minimized version of a complex struct (eg > struct xfrm_state), things can get quite complex if you're trying to > manually untangle and deduplicate the dependencies. > > This commit teaches bpftool to do a minimized dump of a specific types by > providing a optional root_id argument(s). > > Example usage: > > $ ./bpftool btf dump file ~/dev/linux/vmlinux | rg "STRUCT 'xfrm_state'" > [12643] STRUCT 'xfrm_state' size=912 vlen=58 > > $ ./bpftool btf dump file ~/dev/linux/vmlinux root_id 12643 format c > #ifndef __VMLINUX_H__ > #define __VMLINUX_H__ > > [..] > > struct xfrm_type_offload; > > struct xfrm_sec_ctx; > > struct xfrm_state { > possible_net_t xs_net; > union { > struct hlist_node gclist; > struct hlist_node bydst; > }; > union { > struct hlist_node dev_gclist; > struct hlist_node bysrc; > }; > struct hlist_node byspi; > [..] > > [0]: https://github.com/xdp-project/xdp-tools/blob/master/headers/bpf/vmlinux.h > > Signed-off-by: Daniel Xu > --- > .../bpf/bpftool/Documentation/bpftool-btf.rst | 8 +++- > tools/bpf/bpftool/btf.c | 39 ++++++++++++++++++- > 2 files changed, 43 insertions(+), 4 deletions(-) > > diff --git a/tools/bpf/bpftool/Documentation/bpftool-btf.rst b/tools/bpf/bpftool/Documentation/bpftool-btf.rst > index 245569f43035..dbe6d6d94e4c 100644 > --- a/tools/bpf/bpftool/Documentation/bpftool-btf.rst > +++ b/tools/bpf/bpftool/Documentation/bpftool-btf.rst > @@ -24,7 +24,7 @@ BTF COMMANDS > ============= > > | **bpftool** **btf** { **show** | **list** } [**id** *BTF_ID*] > -| **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*] > +| **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*] [**root_id** *ROOT_ID*] > | **bpftool** **btf help** > | > | *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* } > @@ -43,7 +43,7 @@ bpftool btf { show | list } [id *BTF_ID*] > that hold open file descriptors (FDs) against BTF objects. On such kernels > bpftool will automatically emit this information as well. > > -bpftool btf dump *BTF_SRC* [format *FORMAT*] > +bpftool btf dump *BTF_SRC* [format *FORMAT*] [root_id *ROOT_ID*] > Dump BTF entries from a given *BTF_SRC*. > > When **id** is specified, BTF object with that ID will be loaded and all > @@ -67,6 +67,10 @@ bpftool btf dump *BTF_SRC* [format *FORMAT*] > formatting, the output is sorted by default. Use the **unsorted** option > to avoid sorting the output. > > + **root_id** option can be used to filter a dump to a single type and all > + its dependent types. It cannot be used with any other types of filtering. > + It can be passed multiple times to dump multiple types. > + > bpftool btf help > Print short help message. > > diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c > index 3e995faf9efa..2636655ac180 100644 > --- a/tools/bpf/bpftool/btf.c > +++ b/tools/bpf/bpftool/btf.c > @@ -27,6 +27,8 @@ > #define KFUNC_DECL_TAG "bpf_kfunc" > #define FASTCALL_DECL_TAG "bpf_fastcall" > > +#define MAX_ROOT_IDS 16 > + > static const char * const btf_kind_str[NR_BTF_KINDS] = { > [BTF_KIND_UNKN] = "UNKNOWN", > [BTF_KIND_INT] = "INT", > @@ -880,7 +882,8 @@ static int do_dump(int argc, char **argv) > { > bool dump_c = false, sort_dump_c = true; > struct btf *btf = NULL, *base = NULL; > - __u32 root_type_ids[2]; > + __u32 root_type_ids[MAX_ROOT_IDS]; > + bool have_id_filtering; > int root_type_cnt = 0; > __u32 btf_id = -1; > const char *src; > @@ -974,6 +977,8 @@ static int do_dump(int argc, char **argv) > goto done; > } > > + have_id_filtering = !!root_type_cnt; > + > while (argc) { > if (is_prefix(*argv, "format")) { > NEXT_ARG(); > @@ -993,6 +998,36 @@ static int do_dump(int argc, char **argv) > goto done; > } > NEXT_ARG(); > + } else if (is_prefix(*argv, "root_id")) { > + __u32 root_id; > + char *end; > + > + if (have_id_filtering) { > + p_err("cannot use root_id with other type filtering"); > + err = -EINVAL; > + goto done; > + } else if (root_type_cnt == MAX_ROOT_IDS) { > + p_err("only %d root_id are supported", MAX_ROOT_IDS); I doubt users will often reach this limit, but if they do, the message can be confusing, because MAX_ROOT_IDS also accounts for root_type_ids[] cells used when we pass map arguments ("key" or "value" or "kv"), so you could pass 15 "root_id" on the command line and get a message telling only 16 are supported. Maybe add a counter to tell how many were defined from the rest of the command line, and adjust the value in the error message? > + err = -E2BIG; > + goto done; > + } > + > + NEXT_ARG(); > + root_id = strtoul(*argv, &end, 0); > + if (*end) { > + err = -1; > + p_err("can't parse %s as root ID", *argv); > + goto done; > + } > + for (i = 0; i < root_type_cnt; i++) { > + if (root_type_ids[i] == root_id) { > + err = -EINVAL; > + p_err("duplicate root_id %d supplied", root_id); > + goto done; > + } > + } > + root_type_ids[root_type_cnt++] = root_id; > + NEXT_ARG(); > } else if (is_prefix(*argv, "unsorted")) { > sort_dump_c = false; > NEXT_ARG(); > @@ -1403,7 +1438,7 @@ static int do_help(int argc, char **argv) > > fprintf(stderr, > "Usage: %1$s %2$s { show | list } [id BTF_ID]\n" > - " %1$s %2$s dump BTF_SRC [format FORMAT]\n" > + " %1$s %2$s dump BTF_SRC [format FORMAT] [root_id ROOT_ID]\n" > " %1$s %2$s help\n" > "\n" > " BTF_SRC := { id BTF_ID | prog PROG | map MAP [{key | value | kv | all}] | file FILE }\n"