Commit 6a10d2d3 authored by Andrii Nakryiko's avatar Andrii Nakryiko
Browse files

Merge branch 'bpftool-btf-support-dumping-a-single-type-from-file' 

Daniel Xu says:

====================
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 v5:
* Update bash-completion to support repeating root_id
* Update man page to mention root_id NAND map key/value/kv/all

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
====================

Link: https://patch.msgid.link/cover.1734119028.git.dxu@dxuuu.xyz


Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parents 5506b7d7 9d294f69

tools/bpf/bpftool/Documentation/bpftool-btf.rst

+7 −2
Original line number Diff line number Diff line
@@ -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*

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 +67,11 @@ bpftool btf dump *BTF_SRC* 
    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

    (such as the "key", "value", or "kv" arguments when dumping BTF for a map).

    It can be passed multiple times to dump multiple types.



bpftool btf help

    Print short help message.

tools/bpf/bpftool/bash-completion/bpftool

+6 −1
Original line number Diff line number Diff line
@@ -930,19 +930,24 @@ _bpftool() 
                        format)

                            COMPREPLY=( $( compgen -W "c raw" -- "$cur" ) )

                            ;;

                        root_id)

                            return 0;

                            ;;

                        c)

                            COMPREPLY=( $( compgen -W "unsorted" -- "$cur" ) )

                            COMPREPLY=( $( compgen -W "unsorted root_id" -- "$cur" ) )

                            ;;

                        *)

                            # emit extra options

                            case ${words[3]} in

                                id|file)

                                    COMPREPLY=( $( compgen -W "root_id" -- "$cur" ) )

                                    _bpftool_once_attr 'format'

                                    ;;

                                map|prog)

                                    if [[ ${words[3]} == "map" ]] && [[ $cword == 6 ]]; then

                                        COMPREPLY+=( $( compgen -W "key value kv all" -- "$cur" ) )

                                    fi

                                    COMPREPLY=( $( compgen -W "root_id" -- "$cur" ) )

                                    _bpftool_once_attr 'format'

                                    ;;

                                *)

tools/bpf/bpftool/btf.c

+49 −2
Original line number Diff line number Diff line
@@ -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",
@@ -880,12 +882,14 @@ 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;

	int fd = -1;

	int err = 0;

	int i;



	if (!REQ_ARGS(2)) {

		usage();
@@ -973,6 +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();
@@ -992,6 +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);

				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();
@@ -1017,6 +1053,17 @@ static int do_dump(int argc, char **argv) 
		}

	}



	/* Invalid root IDs causes half emitted boilerplate and then unclean

	 * exit. It's an ugly user experience, so handle common error here.

	 */

	for (i = 0; i < root_type_cnt; i++) {

		if (root_type_ids[i] >= btf__type_cnt(btf)) {

			err = -EINVAL;

			p_err("invalid root ID: %u", root_type_ids[i]);

			goto done;

		}

	}



	if (dump_c) {

		if (json_output) {

			p_err("JSON output for C-syntax dump is not supported");
@@ -1391,7 +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"