i386: handle an initrd in highmem (version 2)

The boot protocol has until now required that the initrd be located in
lowmem, which makes the lowmem/highmem boundary visible to the boot
loader.  This was exported to the bootloader via a compile-time
field.  Unfortunately, the vmalloc= command-line option breaks this
part of the protocol; instead of adding yet another hack that affects
the bootloader, have the kernel relocate the initrd down below the
lowmem boundary inside the kernel itself.

Note that this does not rely on HIGHMEM being enabled in the kernel.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 4cc5b0411db5..64ad9016585a 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -195,10 +195,13 @@ cmd_line_ptr:	.long	0		# (Header version 0x0202 or later)
                                         # can be located anywhere in
                                         # low memory 0x10000 or higher.
 
-ramdisk_max:    .long (-__PAGE_OFFSET-(512 << 20)-1) & 0x7fffffff
+ramdisk_max:    .long 0x7fffffff
                                         # (Header version 0x0203 or later)
                                         # The highest safe address for
                                         # the contents of an initrd
+                                        # The current kernel allows up to 4 GB,
+                                        # but leave it at 2 GB to avoid
+                                        # possible bootloader bugs.
 
 kernel_alignment:  .long CONFIG_PHYSICAL_ALIGN  #physical addr alignment
                                                 #required for protected mode