linux-kernel - [PATCH bpf-next v4 0/4] bpftool: btf: Support dumping a single type from file

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Message-ID: <cover.1734052995.git.dxu@dxuuu.xyz>
Date: Thu, 12 Dec 2024 18:24:12 -0700
From: Daniel Xu <dxu@...uu.xyz>
To: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	qmo@...nel.org
Cc: andrii.nakryiko@...il.com,
	antony@...nome.org,
	toke@...nel.org,
	martin.lau@...ux.dev
Subject: [PATCH bpf-next v4 0/4] bpftool: btf: Support dumping a single type from file

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 single type by
providing an optional root_id argument.

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

=== Changelog ===
Changes in v4:
* Support multiple instances of root_id

Changes in v3:
* Make `root_id` a top level btf-dump argument rather than attached to `file`
* Update bash completion script
* Refactor root_type_ids checking to after btf handle creation
* Update help messages and fix existing man page inconsistency

Changes in v2:
* Add early error check for invalid BTF ID

Daniel Xu (4):
  bpftool: man: Add missing format argument to command description
  bpftool: btf: Validate root_type_ids early
  bpftool: btf: Support dumping a specific types from file
  bpftool: bash: Add bash completion for root_id argument

 .../bpf/bpftool/Documentation/bpftool-btf.rst |  8 ++-
 tools/bpf/bpftool/bash-completion/bpftool     |  7 ++-
 tools/bpf/bpftool/btf.c                       | 51 ++++++++++++++++++-
 3 files changed, 60 insertions(+), 6 deletions(-)

-- 
2.46.0