ANDROID: debug_symbols: Add android_debug_for_each_module

Allow vendors to obtain a list of modules loaded at given time. Vendor
modules are able to register on part of notifier chain
(register_module_notifer), but a vendor module would never see modules
which are loaded before the one which registers on the notifier chain.
The kernel doesn't offer load order control, so a hook is necessary to
iterate through currently loaded kernel modules.

Bug: 193552324
Change-Id: I3b01cc1b90f8c0c7c21a37992cc7d607316efc7b
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>

include/linux/android_debug_symbols.h

@@ -50,6 +50,9 @@ enum android_debug_per_cpu_symbol {
 void *android_debug_symbol(enum android_debug_symbol symbol);
 void *android_debug_per_cpu_symbol(enum android_debug_per_cpu_symbol symbol);
 
+void android_debug_for_each_module(int (*fn)(const char *mod_name, void *mod_addr, void *data),
+	void *data);
+
 #else /* !CONFIG_ANDROID_DEBUG_SYMBOLS */
 
 static inline void *android_debug_symbol(enum android_debug_symbol symbol)
@@ -60,6 +63,9 @@ static inline void *android_debug_per_cpu_symbol(enum android_debug_per_cpu_symb
 {
 	return NULL;
 }
+
+static inline void android_debug_for_each_module(int (*fn)(const char *mod_name, void *mod_addr,
+	void *data), void *data) {}
 #endif /* CONFIG_ANDROID_DEBUG_SYMBOLS */
 
 #endif /* _ANDROID_DEBUG_SYMBOLS_H */

kernel/module.c

@@ -4788,6 +4788,23 @@ void print_modules(void)
 	pr_cont("\n");
 }
 
+#ifdef CONFIG_ANDROID_DEBUG_SYMBOLS
+void android_debug_for_each_module(int (*fn)(const char *mod_name, void *mod_addr, void *data),
+	void *data)
+{
+	struct module *module;
+
+	preempt_disable();
+	list_for_each_entry_rcu(module, &modules, list) {
+		if (fn(module->name, module->core_layout.base, data))
+			goto out;
+	}
+out:
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(android_debug_for_each_module);
+#endif
+
 #ifdef CONFIG_MODVERSIONS
 /* Generate the signature for all relevant module structures here.
  * If these change, we don't want to try to parse the module. */