Re: [PATCH] ftrace/module: Allow ftrace to make only loaded module text read-write

From: Jessica Yu
Date: Mon Oct 14 2019 - 08:31:27 EST


+++ Steven Rostedt [10/10/19 08:58 -0400]:
On Wed, 9 Oct 2019 22:36:38 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2029,6 +2029,37 @@ static void module_enable_nx(const struct module *mod)
frob_writable_data(&mod->init_layout, set_memory_nx);
}


Also, if you are worried about these being used anywhere else, we can
add:

+void set_module_text_rw(const struct module *mod)
+{
+ if (!rodata_enabled)
+ return;
+
+ mutex_lock(&module_mutex);
+ if (mod->state == MODULE_STATE_UNFORMED)

if (mod->state == MODULE_STATE_UNFORMED ||
mod->state == MODULE_STATE_LIVE)

As this will keep it from being used on modules that are executing.

Yeah, that'd be good. Aside from the big ftrace_module_init/enable
debate, I'm fine with this patch itself (with the change above), feel
free to include my Ack in case you want to include it with the rest of
the ftrace text_poke stuff.

Acked-by: Jessica Yu <jeyu@xxxxxxxxxx>

Thanks,

Jessica

+ goto out;
+
+ frob_text(&mod->core_layout, set_memory_rw);
+ frob_text(&mod->init_layout, set_memory_rw);
+out:
+ mutex_unlock(&module_mutex);
+}
+
+void set_module_text_ro(const struct module *mod)
+{
+ if (!rodata_enabled)
+ return;
+
+ mutex_lock(&module_mutex);
+ if (mod->state == MODULE_STATE_UNFORMED ||
+ mod->state == MODULE_STATE_GOING)
+ goto out;
+
+ frob_text(&mod->core_layout, set_memory_ro);
+ frob_text(&mod->init_layout, set_memory_ro);
+out:
+ mutex_unlock(&module_mutex);
+}
+