[PATCH] x86: remove data-header and code overlap in boot/setup.S

The setup.S data and code is not cleanly separated.  The current space
reserved for setup header is not enough to fit the complete header.  As a
result, part of the header (EDDBUF) will overwrite the initial code.

I haven't seen any negative impact of this bug.  As, by the time the setup
code is overwritten, we would have finished executing it anyway.  But, I
think it is better to separate the header and code and prevent this
data_overwriting_the_code condition.

The atatched patch adds some space in the header to fit all the data listed
in Documentation/i386/zero-page.txt for both i386 and x86_64 (and updates
zero-page.txt).
Signed-off-by: : "Venkatesh Pallipadi" <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/i386/zero-page.txt

@@ -74,6 +74,10 @@ Offset	Type		Description
 0x21c	unsigned long	INITRD_SIZE, size in bytes of ramdisk image
 0x220	4 bytes		(setup.S)
 0x224	unsigned short	setup.S heap end pointer
+0x226   unsigned short	zero_pad
+0x228   unsigned long	cmd_line_ptr
+0x22c   unsigned long	ramdisk_max
+0x230   16 bytes 	trampoline
 0x290 - 0x2cf		EDD_MBR_SIG_BUFFER (edd.S)
 0x2d0 - 0x600		E820MAP
 0x600 - 0x7ff		EDDBUF (edd.S) for disk signature read sector

arch/i386/boot/setup.S

@@ -162,7 +162,9 @@ ramdisk_max:	.long (-__PAGE_OFFSET-(512 << 20)-1) & 0x7fffffff
 					# the contents of an initrd
 
 trampoline:	call	start_of_setup
-		.space	1024
+		.align 16
+					# The offset at this point is 0x240
+		.space	(0x7ff-0x240+1) # E820 & EDD space (ending at 0x7ff)
 # End of setup header #####################################################
 
 start_of_setup:

arch/x86_64/boot/setup.S

@@ -158,7 +158,9 @@ cmd_line_ptr:	.long 0			# (Header version 0x0202 or later)
 ramdisk_max:	.long 0xffffffff
 	
 trampoline:	call	start_of_setup
-		.space	1024
+		.align 16
+					# The offset at this point is 0x240
+		.space  (0x7ff-0x240+1)	# E820 & EDD space (ending at 0x7ff)
 # End of setup header #####################################################
 
 start_of_setup: