x86/its: Fix build errors when CONFIG_MODULES=n

commit 9f35e33144ae5377d6a8de86dd3bd4d995c6ac65 upstream.

Fix several build errors when CONFIG_MODULES=n, including the following:

../arch/x86/kernel/alternative.c:195:25: error: incomplete definition of type 'struct module'
  195 |         for (int i = 0; i < mod->its_num_pages; i++) {

Fixes: 872df34d7c51 ("x86/its: Use dynamic thunks for indirect branches")
Cc: [email protected]
Signed-off-by: Eric Biggers <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Tested-by: Steven Rostedt (Google) <[email protected]>
Reviewed-by: Alexandre Chartre <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
[ pawan: backport: Bring ITS dynamic thunk code under CONFIG_MODULES ]
Signed-off-by: Pawan Gupta <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: ebiggers

arch/x86/kernel/alternative.c

@@ -402,6 +402,7 @@ static int emit_indirect(int op, int reg, u8 *bytes)
 
 #ifdef CONFIG_MITIGATION_ITS
 
+#ifdef CONFIG_MODULES
 static struct module *its_mod;
 static void *its_page;
 static unsigned int its_offset;
@@ -518,6 +519,14 @@ static void *its_allocate_thunk(int reg)
 
 	return thunk;
 }
+#else /* CONFIG_MODULES */
+
+static void *its_allocate_thunk(int reg)
+{
+	return NULL;
+}
+
+#endif /* CONFIG_MODULES */
 
 static int __emit_trampoline(void *addr, struct insn *insn, u8 *bytes,
 			     void *call_dest, void *jmp_dest)