[PATCH v3 4/8] Implement kernel modules' btf resolving

[Tao Liu]

Same as the previous patch, with kernel's kallsyms and btf ready,
we can locate and iterate all kernel modules' btf data.

Signed-off-by: Tao Liu <ltao at redhat.com>
---
 btf_info.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 btf_info.h |  2 ++
 2 files changed, 76 insertions(+)

diff --git a/btf_info.c b/btf_info.c
index e7f8d9a..752661c 100644
--- a/btf_info.c
+++ b/btf_info.c
@@ -184,3 +184,77 @@ out:
 		free(buf);
 	return ret;
 }
+
+#define MEMBER_OFF(S, M) \
+	GET_STRUCT_MEMBER_MOFF(S, M) / 8
+
+bool init_module_btf(void)
+{
+	struct btf *btf_mod;
+	uint64_t btf_modules, list;
+	struct struct_member_info smi;
+	uint64_t btf = 0, data = 0, module = 0;
+	int data_size = 0;
+	bool ret = false;
+	char *btf_buf = NULL;
+	char *modname = NULL;
+
+	btf_modules = get_kallsyms_value_by_name("btf_modules");
+	if (!btf_modules)
+		/* Maybe module is not enabled, this is not an error */
+		return true;
+
+	INIT_STRUCT_MEMBER(btf_module, list);
+	INIT_STRUCT_MEMBER(btf_module, btf);
+	INIT_STRUCT_MEMBER(btf_module, module);
+	INIT_STRUCT_MEMBER(module, name);
+	INIT_STRUCT_MEMBER(btf, data);
+	INIT_STRUCT_MEMBER(btf, data_size);
+	modname = (char *)malloc(GET_STRUCT_MEMBER_MSIZE(module, name));
+	if (!modname)
+		goto no_mem;
+
+	for (list = next_list(btf_modules); list != btf_modules; list = next_list(list)) {
+		readmem(VADDR, list - MEMBER_OFF(btf_module, list) +
+				MEMBER_OFF(btf_module, btf),
+			&btf, GET_STRUCT_MEMBER_MSIZE(btf_module, btf));
+		readmem(VADDR, list - MEMBER_OFF(btf_module, list) +
+				MEMBER_OFF(btf_module, module),
+			&module, GET_STRUCT_MEMBER_MSIZE(btf_module, module));
+		readmem(VADDR, module + MEMBER_OFF(module, name),
+			modname, GET_STRUCT_MEMBER_MSIZE(module, name));
+		readmem(VADDR, btf + MEMBER_OFF(btf, data),
+			&data, GET_STRUCT_MEMBER_MSIZE(btf, data));
+		readmem(VADDR, btf + MEMBER_OFF(btf, data_size),
+			&data_size, GET_STRUCT_MEMBER_MSIZE(btf, data_size));
+		btf_buf = (char *)malloc(data_size);
+		if (!btf_buf)
+			goto no_mem;
+		readmem(VADDR, data, btf_buf, data_size);
+		btf_mod = btf__new_split(btf_buf, data_size, btf_arr[0].btf);
+		free(btf_buf);
+		if (libbpf_get_error(btf_mod) != 0 ||
+		    add_to_btf_arr(btf_mod, strdup(modname)) == false) {
+			fprintf(stderr, "%s: init %s btf fail\n", __func__, modname);
+			goto out;
+		}
+	}
+	ret = true;
+	goto out;
+
+no_mem:
+	fprintf(stderr, "%s: Not enough memory!\n", __func__);
+out:
+	if (modname)
+		free(modname);
+	return ret;
+}
+
+void cleanup_btf(void)
+{
+	for (int i = 0; i < btf_arr_len; i++) {
+		free(btf_arr[i].module);
+		btf__free(btf_arr[i].btf);
+	}
+	free(btf_arr);
+}
diff --git a/btf_info.h b/btf_info.h
index 1fc6829..d4408c3 100644
--- a/btf_info.h
+++ b/btf_info.h
@@ -16,7 +16,9 @@ struct struct_member_info {
 };
 
 bool init_kernel_btf(void);
+bool init_module_btf(void);
 bool get_struct_member_by_name(struct struct_member_info *smi);
+void cleanup_btf(void);
 
 struct member_off_size {
 	int m_off;
-- 
2.47.0