From 21b748e0100f78fe07e96ccb4fa5a2d285898f21 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Fri, 10 May 2024 11:30:52 +0100 Subject: [PATCH] bpftool: support displaying relocated-with-base split BTF If the -R option is used, we can display BTF that has been generated with distilled base BTF in its relocated form. For example for bpf_testmod.ko (which is built as an out-of-tree module, so has a distilled .BTF.base section: bpftool btf dump file bpf_testmod.ko Alternatively, we can display content relocated with (a possibly changed) base BTF via bpftool btf dump -R /sys/kernel/btf/vmlinux bpf_testmod.ko The latter mirrors how the kernel will handle such split BTF; it relocates its representation with the running kernel, and if successful, renumbers BTF ids to reference the current vmlinux BTF. Signed-off-by: Alan Maguire Acked-by: Eduard Zingerman --- tools/bpf/bpftool/Documentation/bpftool-btf.rst | 15 ++++++++++++++- tools/bpf/bpftool/bash-completion/bpftool | 7 ++++--- tools/bpf/bpftool/btf.c | 11 ++++++++++- tools/bpf/bpftool/main.c | 14 +++++++++++++- tools/bpf/bpftool/main.h | 2 ++ 5 files changed, 43 insertions(+), 6 deletions(-) diff --git a/tools/bpf/bpftool/Documentation/bpftool-btf.rst b/tools/bpf/bpftool/Documentation/bpftool-btf.rst index eaba24320fb2..fd6bb1280e7b 100644 --- a/tools/bpf/bpftool/Documentation/bpftool-btf.rst +++ b/tools/bpf/bpftool/Documentation/bpftool-btf.rst @@ -16,7 +16,7 @@ SYNOPSIS **bpftool** [*OPTIONS*] **btf** *COMMAND* -*OPTIONS* := { |COMMON_OPTIONS| | { **-B** | **--base-btf** } } +*OPTIONS* := { |COMMON_OPTIONS| | { **-B** | **--base-btf** } { **-R** | **relocate-base-btf** } } *COMMANDS* := { **dump** | **help** } @@ -85,6 +85,19 @@ OPTIONS BTF object is passed through other handles, this option becomes necessary. +-R, --relocate-base-btf *FILE* + When split BTF is generated with distilled base BTF for relocation, + the latter is stored in a .BTF.base section and allows us to later + relocate split BTF and a potentially-changed base BTF by using + information in the .BTF.base section about the base types referenced + from split BTF. Relocation is carried out against the split BTF + supplied via this parameter and the split BTF will then refer to + the base types supplied in *FILE*. + + If this option is not used, split BTF is shown relative to the + .BTF.base, which contains just enough information to support later + relocation. + EXAMPLES ======== **# bpftool btf dump id 1226** diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool index 04afe2ac2228..878cf3d49a76 100644 --- a/tools/bpf/bpftool/bash-completion/bpftool +++ b/tools/bpf/bpftool/bash-completion/bpftool @@ -262,7 +262,7 @@ _bpftool() # Deal with options if [[ ${words[cword]} == -* ]]; then local c='--version --json --pretty --bpffs --mapcompat --debug \ - --use-loader --base-btf' + --use-loader --base-btf --relocate-base-btf' COMPREPLY=( $( compgen -W "$c" -- "$cur" ) ) return 0 fi @@ -283,7 +283,7 @@ _bpftool() _sysfs_get_netdevs return 0 ;; - file|pinned|-B|--base-btf) + file|pinned|-B|-R|--base-btf|--relocate-base-btf) _filedir return 0 ;; @@ -297,7 +297,8 @@ _bpftool() local i pprev for (( i=1; i < ${#words[@]}; )); do if [[ ${words[i]::1} == - ]] && - [[ ${words[i]} != "-B" ]] && [[ ${words[i]} != "--base-btf" ]]; then + [[ ${words[i]} != "-B" ]] && [[ ${words[i]} != "--base-btf" ]] && + [[ ${words[i]} != "-R" ]] && [[ ${words[i]} != "--relocate-base-btf" ]]; then words=( "${words[@]:0:i}" "${words[@]:i+1}" ) [[ $i -le $cword ]] && cword=$(( cword - 1 )) else diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index 0ca1f2417801..34f60d9e433d 100644 --- a/tools/bpf/bpftool/btf.c +++ b/tools/bpf/bpftool/btf.c @@ -638,6 +638,14 @@ static int do_dump(int argc, char **argv) base_btf = btf__parse_opts(*argv, &optp); if (base_btf) btf = btf__parse_split(*argv, base_btf); + if (btf && relocate_base_btf) { + err = btf__relocate(btf, relocate_base_btf); + if (err) { + p_err("could not relocate BTF from '%s' with base BTF '%s': %s\n", + *argv, relocate_base_btf_path, strerror(-err)); + goto done; + } + } } if (!btf) { err = -errno; @@ -1075,7 +1083,8 @@ static int do_help(int argc, char **argv) " " HELP_SPEC_MAP "\n" " " HELP_SPEC_PROGRAM "\n" " " HELP_SPEC_OPTIONS " |\n" - " {-B|--base-btf} }\n" + " {-B|--base-btf} |\n" + " {-R|--relocate-base-btf} }\n" "", bin_name, "btf"); diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c index 08d0ac543c67..69d4906bec5c 100644 --- a/tools/bpf/bpftool/main.c +++ b/tools/bpf/bpftool/main.c @@ -32,6 +32,8 @@ bool verifier_logs; bool relaxed_maps; bool use_loader; struct btf *base_btf; +struct btf *relocate_base_btf; +const char *relocate_base_btf_path; struct hashmap *refs_table; static void __noreturn clean_and_exit(int i) @@ -448,6 +450,7 @@ int main(int argc, char **argv) { "debug", no_argument, NULL, 'd' }, { "use-loader", no_argument, NULL, 'L' }, { "base-btf", required_argument, NULL, 'B' }, + { "relocate-base-btf", required_argument, NULL, 'R' }, { 0 } }; bool version_requested = false; @@ -473,7 +476,7 @@ int main(int argc, char **argv) bin_name = "bpftool"; opterr = 0; - while ((opt = getopt_long(argc, argv, "VhpjfLmndB:l", + while ((opt = getopt_long(argc, argv, "VhpjfLmndB:lR:", options, NULL)) >= 0) { switch (opt) { case 'V': @@ -519,6 +522,15 @@ int main(int argc, char **argv) case 'L': use_loader = true; break; + case 'R': + relocate_base_btf_path = optarg; + relocate_base_btf = btf__parse(optarg, NULL); + if (!relocate_base_btf) { + p_err("failed to parse base BTF for relocation at '%s': %d\n", + optarg, -errno); + return -1; + } + break; default: p_err("unrecognized option '%s'", argv[optind - 1]); if (json_output) diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h index 9eb764fe4cc8..bbf8194a2d76 100644 --- a/tools/bpf/bpftool/main.h +++ b/tools/bpf/bpftool/main.h @@ -83,6 +83,8 @@ extern bool verifier_logs; extern bool relaxed_maps; extern bool use_loader; extern struct btf *base_btf; +extern struct btf *relocate_base_btf; +extern const char *relocate_base_btf_path; extern struct hashmap *refs_table; void __printf(1, 2) p_err(const char *fmt, ...);