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Date: Fri, 9 Jul 2021 10:47:52 +0800
From: Shuyi Cheng <chengshuyi@...ux.alibaba.com>
To: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
kafai@...com, songliubraving@...com, yhs@...com,
john.fastabend@...il.com, kpsingh@...nel.org
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org,
linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
Shuyi Cheng <chengshuyi@...ux.alibaba.com>
Subject: [PATCH bpf-next v3 1/2] libbpf: Introduce 'btf_custom_path' to 'bpf_obj_open_opts'
btf_custom_path allows developers to load custom BTF, and subsequent
CO-RE will use custom BTF for relocation.
Learn from Andrii's comments in [0], add the btf_custom_path parameter
to bpf_obj_open_opts, you can directly use the skeleton's
<objname>_bpf__open_opts function to pass in the btf_custom_path
parameter.
Prior to this, there was also a developer who provided a patch with
similar functions. It is a pity that the follow-up did not continue to
advance. See [1].
[0]https://lore.kernel.org/bpf/CAEf4BzbJZLjNoiK8_VfeVg_Vrg=9iYFv+po-38SMe=UzwDKJ=Q@mail.gmail.com/#t
[1]https://yhbt.net/lore/all/CAEf4Bzbgw49w2PtowsrzKQNcxD4fZRE6AKByX-5-dMo-+oWHHA@mail.gmail.com/
Signed-off-by: Shuyi Cheng <chengshuyi@...ux.alibaba.com>
---
tools/lib/bpf/libbpf.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
tools/lib/bpf/libbpf.h | 6 +++++-
2 files changed, 49 insertions(+), 3 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1e04ce7..6702b7f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -498,6 +498,10 @@ struct bpf_object {
* it at load time.
*/
struct btf *btf_vmlinux;
+ /* custom BTF is in addition to vmlinux BTF (i.e., Use the CO-RE
+ * feature in the old kernel).
+ */
+ char *btf_custom_path;
/* vmlinux BTF override for CO-RE relocations */
struct btf *btf_vmlinux_override;
/* Lazily initialized kernel module BTFs */
@@ -2668,6 +2672,27 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)
return false;
}
+static int bpf_object__load_override_btf(struct bpf_object *obj)
+{
+ int err;
+
+ if (obj->btf_vmlinux_override)
+ return 0;
+
+ if (!obj->btf_custom_path)
+ return 0;
+
+ obj->btf_vmlinux_override = btf__parse(obj->btf_custom_path, NULL);
+ err = libbpf_get_error(obj->btf_vmlinux_override);
+ pr_debug("loading custom BTF '%s': %d\n", obj->btf_custom_path, err);
+ if (err) {
+ pr_warn("failed to parse custom BTF\n");
+ obj->btf_vmlinux_override = NULL;
+ }
+
+ return err;
+}
+
static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)
{
int err;
@@ -7554,7 +7579,7 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
__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, *btf_tmp_path;
struct bpf_program *prog;
struct bpf_object *obj;
char tmp_name[64];
@@ -7584,6 +7609,19 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
obj = bpf_object__new(path, obj_buf, obj_buf_sz, obj_name);
if (IS_ERR(obj))
return obj;
+
+ btf_tmp_path = OPTS_GET(opts, btf_custom_path, NULL);
+ if (btf_tmp_path) {
+ if (strlen(btf_tmp_path) >= PATH_MAX) {
+ err = -ENAMETOOLONG;
+ goto out;
+ }
+ obj->btf_custom_path = strdup(btf_tmp_path);
+ if (!obj->btf_custom_path) {
+ err = -ENOMEM;
+ goto out;
+ }
+ }
kconfig = OPTS_GET(opts, kconfig, NULL);
if (kconfig) {
@@ -8049,6 +8087,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
bpf_gen__init(obj->gen_loader, attr->log_level);
err = bpf_object__probe_loading(obj);
+ err = err ? : bpf_object__load_override_btf(obj);
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);
@@ -8075,9 +8114,11 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
}
free(obj->btf_modules);
- /* clean up vmlinux BTF */
+ /* clean up vmlinux BTF and custom BTF*/
btf__free(obj->btf_vmlinux);
obj->btf_vmlinux = NULL;
+ btf__free(obj->btf_vmlinux_override);
+ obj->btf_vmlinux_override = NULL;
obj->loaded = true; /* doesn't matter if successfully or not */
@@ -8702,6 +8743,7 @@ void bpf_object__close(struct bpf_object *obj)
for (i = 0; i < obj->nr_maps; i++)
bpf_map__destroy(&obj->maps[i]);
+ zfree(&obj->btf_custom_path);
zfree(&obj->kconfig);
zfree(&obj->externs);
obj->nr_extern = 0;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 6e61342..5002d1f 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -94,8 +94,12 @@ struct bpf_object_open_opts {
* system Kconfig for CONFIG_xxx externs.
*/
const char *kconfig;
+ /* custom BTF is in addition to vmlinux BTF (i.e., Use the CO-RE
+ * feature in the old kernel).
+ */
+ char *btf_custom_path;
};
-#define bpf_object_open_opts__last_field kconfig
+#define bpf_object_open_opts__last_field btf_custom_path
LIBBPF_API struct bpf_object *bpf_object__open(const char *path);
LIBBPF_API struct bpf_object *
--
1.8.3.1
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