powerpc: Use MODULES_VADDR if defined

In order to allow allocation of modules outside of vmalloc space,
use MODULES_VADDR and MODULES_END when MODULES_VADDR is defined.

Redefine module_alloc() when MODULES_VADDR defined.
Unmap corresponding KASAN shadow memory.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7ecf5fff1eef67d450e73fc412b6ec3818483d75.1593428200.git.christophe.leroy@csgroup.eu

arch/powerpc/mm/kasan/kasan_init_32.c

@@ -115,6 +115,12 @@ static void __init kasan_unmap_early_shadow_vmalloc(void)
 	unsigned long k_end = (unsigned long)kasan_mem_to_shadow((void *)VMALLOC_END);
 
 	kasan_update_early_region(k_start, k_end, __pte(0));
+
+#ifdef MODULES_VADDR
+	k_start = (unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR);
+	k_end = (unsigned long)kasan_mem_to_shadow((void *)MODULES_END);
+	kasan_update_early_region(k_start, k_end, __pte(0));
+#endif
 }
 
 void __init kasan_mmu_init(void)