tools: Allow specifying base BTF file in resolve_btfids

This commit allows specifying the base BTF for resolving btf id
lists/sets during link time in the resolve_btfids tool. The base BTF is
set to NULL if no path is passed. This allows resolving BTF ids for
module kernel objects.

Also, drop the --no-fail option, as it is only used in case .BTF_ids
section is not present, instead make no-fail the default mode. The long
option name is same as that of pahole.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211002011757.311265-5-memxor@gmail.com

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index de6365b..c6c3e61 100644 (file)
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -89,6 +89,7 @@ struct btf_id {
 struct object {
        const char *path;
        const char *btf;
+       const char *base_btf_path;
 
        struct {
                int              fd;
@@ -477,16 +478,27 @@ static int symbols_resolve(struct object *obj)
        int nr_structs  = obj->nr_structs;
        int nr_unions   = obj->nr_unions;
        int nr_funcs    = obj->nr_funcs;
+       struct btf *base_btf = NULL;
        int err, type_id;
        struct btf *btf;
        __u32 nr_types;
 
-       btf = btf__parse(obj->btf ?: obj->path, NULL);
+       if (obj->base_btf_path) {
+               base_btf = btf__parse(obj->base_btf_path, NULL);
+               err = libbpf_get_error(base_btf);
+               if (err) {
+                       pr_err("FAILED: load base BTF from %s: %s\n",
+                              obj->base_btf_path, strerror(-err));
+                       return -1;
+               }
+       }
+
+       btf = btf__parse_split(obj->btf ?: obj->path, base_btf);
        err = libbpf_get_error(btf);
        if (err) {
                pr_err("FAILED: load BTF from %s: %s\n",
                        obj->btf ?: obj->path, strerror(-err));
-               return -1;
+               goto out;
        }
 
        err = -1;
@@ -545,6 +557,7 @@ static int symbols_resolve(struct object *obj)
 
        err = 0;
 out:
+       btf__free(base_btf);
        btf__free(btf);
        return err;
 }
@@ -678,7 +691,6 @@ static const char * const resolve_btfids_usage[] = {
 
 int main(int argc, const char **argv)
 {
-       bool no_fail = false;
        struct object obj = {
                .efile = {
                        .idlist_shndx  = -1,
@@ -695,8 +707,8 @@ int main(int argc, const char **argv)
                         "be more verbose (show errors, etc)"),
                OPT_STRING(0, "btf", &obj.btf, "BTF data",
                           "BTF data"),
-               OPT_BOOLEAN(0, "no-fail", &no_fail,
-                          "do not fail if " BTF_IDS_SECTION " section is not found"),
+               OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
+                          "path of file providing base BTF"),
                OPT_END()
        };
        int err = -1;
@@ -717,10 +729,8 @@ int main(int argc, const char **argv)
         */
        if (obj.efile.idlist_shndx == -1 ||
            obj.efile.symbols_shndx == -1) {
-               if (no_fail)
-                       return 0;
-               pr_err("FAILED to find needed sections\n");
-               return -1;
+               pr_debug("Cannot find .BTF_ids or symbols sections, nothing to do\n");
+               return 0;
        }
 
        if (symbols_collect(&obj))

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index aa94739..5a94d09 100644 (file)
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -454,7 +454,7 @@ $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS)                   \
                             | $(TRUNNER_BINARY)-extras
        $$(call msg,BINARY,,$$@)
        $(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) -o $$@
-       $(Q)$(RESOLVE_BTFIDS) --no-fail --btf $(TRUNNER_OUTPUT)/btf_data.o $$@
+       $(Q)$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.o $$@
 
 endef