ARM: kexec: advertise location of bootable RAM

Advertise the location of bootable RAM to kexec-tools.  kexec needs to
know where it can place the kernel in RAM, and so be executable when the
system needs to jump into it.

Advertise these areas in /proc/iomem with a "System RAM (boot alias)"
tag.

Link: http://lkml.kernel.org/r/E1b8ko4-0004HA-GF@rmk-PC.armlinux.org.uk
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Reviewed-by: Pratyush Anand <panand@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Keerthy <j-keerthy@ti.com>
Cc: Vitaly Andrianov <vitalya@ti.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Simon Horman <horms@verge.net.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm/kernel/setup.c

@@ -848,10 +848,29 @@ static void __init request_standard_resources(const struct machine_desc *mdesc)
 	kernel_data.end     = virt_to_phys(_end - 1);
 
 	for_each_memblock(memory, region) {
+		phys_addr_t start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
+		phys_addr_t end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
+		unsigned long boot_alias_start;
+
+		/*
+		 * Some systems have a special memory alias which is only
+		 * used for booting.  We need to advertise this region to
+		 * kexec-tools so they know where bootable RAM is located.
+		 */
+		boot_alias_start = phys_to_idmap(start);
+		if (arm_has_idmap_alias() && boot_alias_start != IDMAP_INVALID_ADDR) {
+			res = memblock_virt_alloc(sizeof(*res), 0);
+			res->name = "System RAM (boot alias)";
+			res->start = boot_alias_start;
+			res->end = phys_to_idmap(end);
+			res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+			request_resource(&iomem_resource, res);
+		}
+
 		res = memblock_virt_alloc(sizeof(*res), 0);
 		res->name  = "System RAM";
-		res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
-		res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
+		res->start = start;
+		res->end = end;
 		res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
 		request_resource(&iomem_resource, res);