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Sat, 7 Dec 2024 18:24:28 -0500 (EST) From: Daniel Xu To: hawk@kernel.org, john.fastabend@gmail.com, kuba@kernel.org, ast@kernel.org, davem@davemloft.net, qmo@kernel.org, daniel@iogearbox.net, andrii@kernel.org 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, antony@phenome.org, toke@kernel.org Subject: [PATCH bpf-next v2] bpftool: btf: Support dumping a single type from file Date: Sat, 7 Dec 2024 16:24:17 -0700 Message-ID: X-Mailer: git-send-email 2.46.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net 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 Signed-off-by: Daniel Xu --- Changes in v2: * Add early error check for invalid BTF ID .../bpf/bpftool/Documentation/bpftool-btf.rst | 5 +++-- tools/bpf/bpftool/btf.c | 19 +++++++++++++++++++ 2 files changed, 22 insertions(+), 2 deletions(-) diff --git a/tools/bpf/bpftool/Documentation/bpftool-btf.rst b/tools/bpf/bpftool/Documentation/bpftool-btf.rst index 3f6bca03ad2e..5abd0e99022f 100644 --- a/tools/bpf/bpftool/Documentation/bpftool-btf.rst +++ b/tools/bpf/bpftool/Documentation/bpftool-btf.rst @@ -27,7 +27,7 @@ BTF COMMANDS | **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*] | **bpftool** **btf help** | -| *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* } +| *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* [**root_id** *ROOT_ID*] } | *FORMAT* := { **raw** | **c** [**unsorted**] } | *MAP* := { **id** *MAP_ID* | **pinned** *FILE* } | *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* | **name** *PROG_NAME* } @@ -60,7 +60,8 @@ bpftool btf dump *BTF_SRC* When specifying *FILE*, an ELF file is expected, containing .BTF section with well-defined BTF binary format data, typically produced by clang or - pahole. + pahole. You can choose to dump a single type and all its dependent types + by providing an optional *ROOT_ID*. **format** option can be used to override default (raw) output format. Raw (**raw**) or C-syntax (**c**) output formats are supported. With C-style diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index d005e4fd6128..a75e17efaf5e 100644 --- a/tools/bpf/bpftool/btf.c +++ b/tools/bpf/bpftool/btf.c @@ -953,6 +953,8 @@ static int do_dump(int argc, char **argv) NEXT_ARG(); } else if (is_prefix(src, "file")) { const char sysfs_prefix[] = "/sys/kernel/btf/"; + __u32 root_id; + char *end; if (!base_btf && strncmp(*argv, sysfs_prefix, sizeof(sysfs_prefix) - 1) == 0 && @@ -967,6 +969,23 @@ static int do_dump(int argc, char **argv) goto done; } NEXT_ARG(); + + if (argc && is_prefix(*argv, "root_id")) { + NEXT_ARG(); + root_id = strtoul(*argv, &end, 0); + if (*end) { + err = -1; + p_err("can't parse %s as root ID", *argv); + goto done; + } + if (root_id >= btf__type_cnt(btf)) { + err = -EINVAL; + p_err("invalid root ID: %u", root_id); + goto done; + } + root_type_ids[root_type_cnt++] = root_id; + NEXT_ARG(); + } } else { err = -1; p_err("unrecognized BTF source specifier: '%s'", src);