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@xxxxxxxxxxxxxx/#t [1]https://yhbt.net/lore/all/CAEf4Bzbgw49w2PtowsrzKQNcxD4fZRE6AKByX-5-dMo-+oWHHA@xxxxxxxxxxxxxx/ Signed-off-by: Shuyi Cheng <chengshuyi@xxxxxxxxxxxxxxxxx> --- 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
