[PATCH] ARM: cleanup vmalloc start/offset macros

VMALLOC_START and VMALLOC_OFFSET are common between all ARM
machine classes.  Move them into include/asm-arm/pgtable.h,
but allow a machine class to override them if required.

Signed-off-by: Russell King <rmk@arm.linux.org.uk>

include/asm-arm/pgtable.h

@@ -16,6 +16,23 @@
 #include <asm/proc-fns.h>
 #include <asm/arch/vmalloc.h>
 
+/*
+ * Just any arbitrary offset to the start of the vmalloc VM area: the
+ * current 8MB value just means that there will be a 8MB "hole" after the
+ * physical memory until the kernel virtual memory starts.  That means that
+ * any out-of-bounds memory accesses will hopefully be caught.
+ * The vmalloc() routines leaves a hole of 4kB between each vmalloced
+ * area for the same reason. ;)
+ *
+ * Note that platforms may override VMALLOC_START, but they must provide
+ * VMALLOC_END.  VMALLOC_END defines the (exclusive) limit of this space,
+ * which may not overlap IO space.
+ */
+#ifndef VMALLOC_START
+#define VMALLOC_OFFSET		(8*1024*1024)
+#define VMALLOC_START		(((unsigned long)high_memory + VMALLOC_OFFSET) & ~(VMALLOC_OFFSET-1))
+#endif
+
 /*
  * Hardware-wise, we have a two level page table structure, where the first
  * level has 4096 entries, and the second level has 256 entries.  Each entry