For old CPUs, map the 64 first MB of RAM as it used to be. Some ports

(XScale mainly) expects the memory located before the kernel to be mapped,
and use it to allocate the page tables, the various stacks, etc.
A better fix would probably be to rewrite the various bla_machdep.c to stop
using that RAM, but I'm not so inclined to do it, especially since I don't
have hardware for all of them.

sys/arm/arm/locore.S

@@ -166,9 +166,32 @@ Lunmapped:
 	ldr	r1, [r0, #4]
 	sub	r0, r1, r2
 
+#ifndef _ARM_ARCH_6
+	/*
+	 * Some of the older ports (the various XScale, mostly) assume
+	 * that the memory before the kernel is mapped, and use it for
+	 * the various stacks, page tables, etc. For those CPUs, map the 
+	 * 64 first MB of RAM, as it used to be. 
+	 */
 	/*
 	 * Map PA == VA
-	 */
+	 */    
+	ldr     r5, =PHYSADDR
+	mov     r1, r5
+	mov     r2, r5
+	/* Map 64MiB, preserved over calls to build_pagetables */
+	mov     r3, #64
+	bl      build_pagetables
+	
+	/* Create the kernel map to jump to */
+	mov     r1, r5
+	ldr     r2, =(KERNBASE)
+	bl      build_pagetables
+	ldr	r5, =(KERNPHYSADDR)
+#else
+	/*
+	 * Map PA == VA
+	 */    
 	/* Find the start kernels load address */
 	adr	r5, _start
 	ldr	r2, =(L1_S_OFFSET)
@@ -183,6 +206,7 @@ Lunmapped:
 	mov	r1, r5
 	ldr	r2, =(KERNVIRTADDR)
 	bl	build_pagetables
+#endif
 	
 #if defined(SOCDEV_PA) && defined(SOCDEV_VA)
 	/* Create the custom map */