ANDROID: BACKPORT: x86/extable: Do not mark exception callback as CFI

The exception table entries are constructed out of a relative offset
and point to the actual function, not the CFI table entry. For now,
just mark the caller as not checking CFI. The failure is most visible
at boot with CONFIG_DEBUG_RODATA_TEST=y.

Bug: 145297900
Change-Id: Ia5e9da358c41b8e8a08e253926ed31775817a4e6
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

arch/x86/mm/extable.c

@@ -170,6 +170,7 @@ __visible bool ex_has_fault_handler(unsigned long ip)
 	return handler == ex_handler_fault;
 }
 
+__nocfi
 int fixup_exception(struct pt_regs *regs, int trapnr)
 {
 	const struct exception_table_entry *e;