powerpc/kmemleak: Do not scan the DART table

The DART table allocation is registered to kmemleak via the
memblock_alloc_base() call. However, the DART table is later unmapped
and dart_tablebase VA no longer accessible. This patch tells kmemleak
not to scan this block and avoid an unhandled paging request.

Signed-off-by: Catalin Marinas <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Signed-off-by: Benjamin Herrenschmidt <[e-mail]>

arch/powerpc/sysdev/dart_iommu.c

···
 	 */
 	dart_tablebase = (unsigned long)
 		__va(memblock_alloc_base(1UL<<24, 1UL<<24, 0x80000000L));
+	/*
+	 * The DART space is later unmapped from the kernel linear mapping and
+	 * accessing dart_tablebase during kmemleak scanning will fault.
+	 */
+	kmemleak_no_scan((void *)dart_tablebase);
 
 	printk(KERN_INFO "DART table allocated at: %lx\n", dart_tablebase);
 }