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 specific types by
providing a optional root_id argument(s).
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 <dxu@xxxxxxxxx>
---
.../bpf/bpftool/Documentation/bpftool-btf.rst | 9 ++++-
tools/bpf/bpftool/btf.c | 39 ++++++++++++++++++-
2 files changed, 44 insertions(+), 4 deletions(-)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-btf.rst b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
index 245569f43035..d47dddc2b4ee 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-btf.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
@@ -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* [format *FORMAT*]
+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* [format *FORMAT*]
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.
diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 3e995faf9efa..2636655ac180 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -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",
@@ -880,7 +882,8 @@ 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;
@@ -974,6 +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();
@@ -993,6 +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();
@@ -1403,7 +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"
--
2.46.0
