If the -R <base_btf> 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 <alan.maguire@xxxxxxxxxx>
---
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 2e8bd2c9f0a3..7df8a686fef7 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -639,6 +639,14 @@ 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;
@@ -1076,7 +1084,8 @@ 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, ...);
--
2.31.1
