x86: put initial_pg_tables into .bss

Impact: makes vmlinux section information more useful

Don't use ram after _end blindly for pagetables. aka init pages is before _end
put those pg table into .bss

[Adapted to use brk segment - Jeremy]

v2: keep initial page table up to 512M only.
v4: put initial page tables just before _end

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/kernel/vmlinux_32.lds.S b/arch/x86/kernel/vmlinux_32.lds.S
index a1f28b8..98424f3 100644
--- a/arch/x86/kernel/vmlinux_32.lds.S
+++ b/arch/x86/kernel/vmlinux_32.lds.S
@@ -210,6 +210,12 @@
   DWARF_DEBUG
 }
 
+/*
+ * Build-time check on the image size:
+ */
+ASSERT((_end - LOAD_OFFSET <= KERNEL_IMAGE_SIZE),
+	"kernel image bigger than KERNEL_IMAGE_SIZE")
+
 #ifdef CONFIG_KEXEC
 /* Link time checks */
 #include <asm/kexec.h>