init, allow blacklisting of module_init functions

At some point I was 100% sure this worked. I do remember testing it against just a loadable module and had positive testing results. I went back to the time that it was commited (3.15-ish) and blacklisting a module init function didn't work there either, so something went wrong somewhere. In any case this is a trivial patch to add the functionality...

P.

---8<---

sprint_symbol_no_offset() returns the string "function_name [module_name]" where [module_name] is not printed for built in kernel functions. This means that the blacklisting code will fail when comparing module function names with the extended string. This patch adds the functionality to block a module's module_init() function by finding the space in the string and truncating the comparison to that length.

---
 init/main.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

index 4c17fda5c2ff..730d6a846216 100644
@@ -708,14 +708,25 @@ static bool __init_or_module initcall_blacklisted(initcall_t fn)
 {
 	struct blacklist_entry *entry;
 	char fn_name[KSYM_SYMBOL_LEN];
+	char *space;
+	int length;
 
 	if (list_empty(&blacklisted_initcalls))
 		return false;
 
 	sprint_symbol_no_offset(fn_name, (unsigned long)fn);
+	/*
+	 * fn will be "function_name [module_name]" where [module_name] is not
+	 * displayed for built-in init functions.  Strip off the [module_name].
+	 */
+	space = strchrnul(fn_name, ' ');
+	if (!space)
+		length = strlen(fn_name);
+	else
+		length = space - fn_name;
 
 	list_for_each_entry(entry, &blacklisted_initcalls, next) {
-		if (!strcmp(fn_name, entry->buf)) {
+		if (!strncmp(fn_name, entry->buf, length)) {
 			pr_debug("initcall %s blacklisted\n", fn_name);
 			return true;
 		}

1.7.9.3

I think the current %ps/%pf behaviour was introduced in 4796dd200db9 (way back in 2012).

Which I still think is broken and needlessly complicated. Please read my first reply again.

Rasmus

Yeah, I'm scratching my head on that. I *know* I tested it and it worked.

Oops -- I completely missed the 2nd half of your reply. Sorry 'bout that.

I'll do a v3 in a bit

P.