x86: boot protocol updates

[sfrench/cifs-2.6.git] / arch / x86 / boot / header.S

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 6ef5a060fa11085df5be8d4616acd5541b53d5d2..6d2df8d61c54089a553c0cdee879dde6f421130c 100644 (file)
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -22,6 +22,7 @@
 #include <asm/page.h>
 #include <asm/setup.h>
 #include "boot.h"
+#include "offsets.h"
 
 SETUPSECTS     = 4                     /* default nr of setup-sectors */
 BOOTSEG                = 0x07C0                /* original address of boot-sector */
@@ -119,7 +120,7 @@ _start:
        # Part 2 of the header, from the old setup.S
 
                .ascii  "HdrS"          # header signature
-               .word   0x0207          # header version number (>= 0x0105)
+               .word   0x0208          # header version number (>= 0x0105)
                                        # or else old loadlin-1.5 will fail)
                .globl realmode_swtch
 realmode_swtch:        .word   0, 0            # default_switch, SETUPSEG
@@ -195,10 +196,13 @@ 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
@@ -220,6 +224,9 @@ hardware_subarch:   .long 0                 # subarchitecture, added with 2.07
 
 hardware_subarch_data: .quad 0
 
+payload_offset:                .long input_data
+payload_length:                .long input_data_end-input_data
+
 # End of setup header #####################################################
 
        .section ".inittext", "ax"
@@ -236,39 +243,30 @@ start_of_setup:
        movw    %ax, %es
        cld
 
-# Apparently some ancient versions of LILO invoked the kernel
-# with %ss != %ds, which happened to work by accident for the
-# old code.  If the CAN_USE_HEAP flag is set in loadflags, or
-# %ss != %ds, then adjust the stack pointer.
-
-       # Smallest possible stack we can tolerate
-       movw    $(_end+STACK_SIZE), %cx
-
-       movw    heap_end_ptr, %dx
-       addw    $512, %dx
-       jnc     1f
-       xorw    %dx, %dx        # Wraparound - whole segment available
-1:     testb   $CAN_USE_HEAP, loadflags
-       jnz     2f
+# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
+# which happened to work by accident for the old code.  Recalculate the stack
+# pointer if %ss is invalid.  Otherwise leave it alone, LOADLIN sets up the
+# stack behind its own code, so we can't blindly put it directly past the heap.
 
-       # No CAN_USE_HEAP
        movw    %ss, %dx
        cmpw    %ax, %dx        # %ds == %ss?
        movw    %sp, %dx
-       # If so, assume %sp is reasonably set, otherwise use
-       # the smallest possible stack.
-       jne     4f              # -> Smallest possible stack...
+       je      2f              # -> assume %sp is reasonably set
+
+       # Invalid %ss, make up a new stack
+       movw    $_end, %dx
+       testb   $CAN_USE_HEAP, loadflags
+       jz      1f
+       movw    heap_end_ptr, %dx
+1:     addw    $STACK_SIZE, %dx
+       jnc     2f
+       xorw    %dx, %dx        # Prevent wraparound
 
-       # Make sure the stack is at least minimum size.  Take a value
-       # of zero to mean "full segment."
-2:
+2:     # Now %dx should point to the end of our stack space
        andw    $~3, %dx        # dword align (might as well...)
        jnz     3f
        movw    $0xfffc, %dx    # Make sure we're not zero
-3:     cmpw    %cx, %dx
-       jnb     5f
-4:     movw    %cx, %dx        # Minimum value we can possibly use
-5:     movw    %ax, %ss
+3:     movw    %ax, %ss
        movzwl  %dx, %esp       # Clear upper half of %esp
        sti                     # Now we should have a working stack