Andrii,
I have made the following changes as discussed to add an option to the `open_opts`
to take in the BTF.
Please do take a look. Also, I am not sure what the procedure is for submitting patches/reviews.
If anyone has any pointers to a webpage where this is described I can go through it. But, below are
the proposed changes.
Best Regards,
Vamsi.
---
src/libbpf.c | 56 +++++++++++++++++++++++++++++++++++++---------------
src/libbpf.h | 4 +++-
2 files changed, 43 insertions(+), 17 deletions(-)
diff --git a/src/libbpf.c b/src/libbpf.c
index 6ae748f..35d7254 100644
--- a/src/libbpf.c
+++ b/src/libbpf.c
@@ -2538,9 +2538,12 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)
struct bpf_program *prog;
int i;
- /* CO-RE relocations need kernel BTF */
+ /* CO-RE relocations need kernel BTF or an override BTF.
+ * If override BTF present CO-RE can use it.
+ */
if (obj->btf_ext && obj->btf_ext->core_relo_info.len)
- return true;
+ if (!obj->btf_vmlinux_override)
+ return true;
/* Support for typed ksyms needs kernel BTF */
for (i = 0; i < obj->nr_extern; i++) {
@@ -2561,6 +2564,27 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)
return false;
}
+static int bpf_object__load_override_btf(struct bpf_object *obj,
+ const char *targ_btf_path)
+{
+ /* Could have been be set via `bpf_object_open_opts` */
+ if (obj->btf_vmlinux_override)
+ return 0;
+
+ if (!targ_btf_path)
+ return 0;
+
+ obj->btf_vmlinux_override = btf__parse(targ_btf_path, NULL);
+ if (IS_ERR_OR_NULL(obj->btf_vmlinux_override)) {
+ int err = PTR_ERR(obj->btf_vmlinux_override);
+ obj->btf_vmlinux_override = NULL;
+ pr_warn("failed to parse target BTF: %d\n", err);
+ return err;
+ }
+
+ return 0;
+}
+
static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)
{
int err;
@@ -6031,7 +6055,7 @@ patch_insn:
}
static int
-bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
+bpf_object__relocate_core(struct bpf_object *obj)
{
const struct btf_ext_info_sec *sec;
const struct bpf_core_relo *rec;
@@ -6045,15 +6069,6 @@ bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
if (obj->btf_ext->core_relo_info.len == 0)
return 0;
- if (targ_btf_path) {
- obj->btf_vmlinux_override = btf__parse(targ_btf_path, NULL);
- if (IS_ERR_OR_NULL(obj->btf_vmlinux_override)) {
- err = PTR_ERR(obj->btf_vmlinux_override);
- pr_warn("failed to parse target BTF: %d\n", err);
- return err;
- }
- }
-
cand_cache = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, NULL);
if (IS_ERR(cand_cache)) {
err = PTR_ERR(cand_cache);
@@ -6556,14 +6571,14 @@ bpf_object__relocate_calls(struct bpf_object *obj, struct bpf_program *prog)
}
static int
-bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path)
+bpf_object__relocate(struct bpf_object *obj)
{
struct bpf_program *prog;
size_t i;
int err;
if (obj->btf_ext) {
- err = bpf_object__relocate_core(obj, targ_btf_path);
+ err = bpf_object__relocate_core(obj);
if (err) {
pr_warn("failed to perform CO-RE relocations: %d\n",
err);
@@ -7088,7 +7103,7 @@ static struct bpf_object *
__bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
const struct bpf_object_open_opts *opts)
{
- const char *obj_name, *kconfig;
+ const char *obj_name, *kconfig, *core_btf_path;
struct bpf_program *prog;
struct bpf_object *obj;
char tmp_name[64];
@@ -7126,6 +7141,14 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
return ERR_PTR(-ENOMEM);
}
+ core_btf_path = OPTS_GET(opts, core_btf_path, NULL);
+ if (core_btf_path) {
+ pr_debug("parse btf '%s' for CO-RE relocations\n", core_btf_path);
+ obj->btf_vmlinux_override = btf__parse(core_btf_path, NULL);
+ if (IS_ERR_OR_NULL(obj->btf_vmlinux_override))
+ pr_warn("can't parse btf at '%s'\n", core_btf_path);
+ }
+
err = bpf_object__elf_init(obj);
err = err ? : bpf_object__check_endianness(obj);
err = err ? : bpf_object__elf_collect(obj);
@@ -7481,13 +7504,14 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
}
err = bpf_object__probe_loading(obj);
+ err = err ? : bpf_object__load_override_btf(obj, attr->target_btf_path);
err = err ? : bpf_object__load_vmlinux_btf(obj, false);
err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
err = err ? : bpf_object__sanitize_and_load_btf(obj);
err = err ? : bpf_object__sanitize_maps(obj);
err = err ? : bpf_object__init_kern_struct_ops_maps(obj);
err = err ? : bpf_object__create_maps(obj);
- err = err ? : bpf_object__relocate(obj, attr->target_btf_path);
+ err = err ? : bpf_object__relocate(obj);
err = err ? : bpf_object__load_progs(obj, attr->log_level);
/* clean up module BTFs */
diff --git a/src/libbpf.h b/src/libbpf.h
index 3c35eb4..40c4ee9 100644
--- a/src/libbpf.h
+++ b/src/libbpf.h
@@ -93,8 +93,10 @@ struct bpf_object_open_opts {
* system Kconfig for CONFIG_xxx externs.
*/
const char *kconfig;
+ /* Path to ELF file with BTF section to be used for relocations. */
+ const char *core_btf_path;
};
-#define bpf_object_open_opts__last_field kconfig
+#define bpf_object_open_opts__last_field core_btf_path
LIBBPF_API struct bpf_object *bpf_object__open(const char *path);
LIBBPF_API struct bpf_object *
--
2.23.3
