module: Add module_for_each_mod() function

The tracing system needs a way to save all the currently loaded modules
and their addresses into persistent memory so that it can evaluate the
addresses on a reboot from a crash. When the persistent memory trace
starts, it will load the module addresses and names into the persistent
memory. To do so, it will call the module_for_each_mod() function and pass
it a function and data structure to get called on each loaded module. Then
it can record the memory.

This only implements that function.

Cc: Luis Chamberlain <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Sami Tolvanen <[email protected]>
Cc: Daniel Gomez <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/[email protected]
Acked-by: Petr Pavlu <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

include/linux/module.h

@@ -782,6 +782,8 @@ static inline void *module_writable_address(struct module *mod, void *loc)
 	return __module_writable_address(mod, loc);
 }
 
+void module_for_each_mod(int(*func)(struct module *mod, void *data), void *data);
+
 #else /* !CONFIG_MODULES... */
 
 static inline struct module *__module_address(unsigned long addr)
@@ -894,6 +896,10 @@ static inline void *module_writable_address(struct module *mod, void *loc)
 {
 	return loc;
 }
+
+static inline void module_for_each_mod(int(*func)(struct module *mod, void *data), void *data)
+{
+}
 #endif /* CONFIG_MODULES */
 
 #ifdef CONFIG_SYSFS

kernel/module/main.c

@@ -3809,6 +3809,19 @@ bool is_module_text_address(unsigned long addr)
 	return ret;
 }
 
+void module_for_each_mod(int(*func)(struct module *mod, void *data), void *data)
+{
+	struct module *mod;
+
+	guard(rcu)();
+	list_for_each_entry_rcu(mod, &modules, list) {
+		if (mod->state == MODULE_STATE_UNFORMED)
+			continue;
+		if (func(mod, data))
+			break;
+	}
+}
+
 /**
  * __module_text_address() - get the module whose code contains an address.
  * @addr: the address.