Detect whether a kernel supports any BTF at all, and if not, don't even
attempt loading BTF to avoid unnecessary log messages like:
libbpf: Error loading BTF: Invalid argument(22)
libbpf: Error loading .BTF into kernel: -22. BTF is optional, ignoring.
Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
---
tools/lib/bpf/libbpf.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 32c71a3b3aef..b4d2fd13ad42 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -170,6 +170,8 @@ enum kern_feature_id {
FEAT_PROG_NAME,
/* v5.2: kernel support for global data sections. */
FEAT_GLOBAL_DATA,
+ /* BTF support */
+ FEAT_BTF,
/* BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO support */
FEAT_BTF_FUNC,
/* BTF_KIND_VAR and BTF_KIND_DATASEC support */
@@ -2531,6 +2533,15 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
if (!obj->btf)
return 0;
+ if (!kernel_supports(FEAT_BTF)) {
+ if (kernel_needs_btf(obj)) {
+ err = -EOPNOTSUPP;
+ goto report;
+ }
+ pr_debug("Kernel doesn't support BTF, skipping uploading it.\n");
+ return 0;
+ }
+
sanitize = btf_needs_sanitization(obj);
if (sanitize) {
const void *raw_data;
@@ -2554,6 +2565,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
}
btf__free(kern_btf);
}
+report:
if (err) {
btf_mandatory = kernel_needs_btf(obj);
pr_warn("Error loading .BTF into kernel: %d. %s\n", err,
@@ -3497,6 +3509,18 @@ static int probe_kern_global_data(void)
return probe_fd(ret);
}
+static int probe_kern_btf(void)
+{
+ static const char strs[] = "\0int";
+ __u32 types[] = {
+ /* int */
+ BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
+ };
+
+ return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+ strs, sizeof(strs)));
+}
+
static int probe_kern_btf_func(void)
{
static const char strs[] = "\0int\0x\0a";
@@ -3628,6 +3652,9 @@ static struct kern_feature_desc {
[FEAT_GLOBAL_DATA] = {
"global variables", probe_kern_global_data,
},
+ [FEAT_BTF] = {
+ "minimal BTF", probe_kern_btf,
+ },
[FEAT_BTF_FUNC] = {
"BTF functions", probe_kern_btf_func,
},
--
2.24.1
