x86, mm: if kernel .text .data .bss are not marked as E820_RAM, complain and fix

There could be cases where user supplied memmap=exactmap memory
mappings do not mark the region where the kernel .text .data and
.bss reside as E820_RAM, as reported here:

https://lkml.org/lkml/2012/8/14/86

Handle it by complaining, and adding the range back into the e820.

Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Link: http://lkml.kernel.org/r/1353123563-3103-11-git-send-email-yinghai@kernel.org
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/kernel/setup.c

@@ -832,6 +832,20 @@ void __init setup_arch(char **cmdline_p)
 	insert_resource(&iomem_resource, &data_resource);
 	insert_resource(&iomem_resource, &bss_resource);
 
+	/*
+	 * Complain if .text .data and .bss are not marked as E820_RAM and
+	 * attempt to fix it by adding the range. We may have a confused BIOS,
+	 * or the user may have incorrectly supplied it via memmap=exactmap. If
+	 * we really are running on top non-RAM, we will crash later anyways.
+	 */
+	if (!e820_all_mapped(code_resource.start, __pa(__brk_limit), E820_RAM)) {
+		pr_warn(".text .data .bss are not marked as E820_RAM!\n");
+
+		e820_add_region(code_resource.start,
+				__pa(__brk_limit) - code_resource.start + 1,
+				E820_RAM);
+	}
+
 	trim_bios_range();
 #ifdef CONFIG_X86_32
 	if (ppro_with_ram_bug()) {