x86, boot: make kernel_alignment adjustable; new bzImage fields

Make the kernel_alignment field adjustable; this allows us to set it
to a large value (intended to be 16 MB to avoid ZONE_DMA contention,
memory holes and other weirdness) while a smart bootloader can still
force a loading at a lesser alignment if absolutely necessary.

Also export pref_address (preferred loading address, corresponding to
the link-time address) and init_size, the total amount of linear
memory the kernel will require during initialization.

[ Impact: allows better kernel placement, gives bootloader more info ]

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 27285143adeb..a0b426978d55 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -116,7 +116,7 @@ _start:
         # Part 2 of the header, from the old setup.S
 
                 .ascii  "HdrS"          # header signature
-                .word   0x0209          # header version number (>= 0x0105)
+                .word   0x020a          # header version number (>= 0x0105)
                                         # or else old loadlin-1.5 will fail)
                 .globl realmode_swtch
 realmode_swtch: .word   0, 0            # default_switch, SETUPSEG
@@ -201,7 +201,7 @@ relocatable_kernel:    .byte 1
 #else
 relocatable_kernel:    .byte 0
 #endif
-pad2:                   .byte 0
+min_alignment:          .byte MIN_KERNEL_ALIGN_LG2      # minimum alignment
 pad3:                   .word 0
 
 cmdline_size:   .long   COMMAND_LINE_SIZE-1     #length of the command line,
@@ -220,6 +220,17 @@ setup_data:		.quad 0			# 64-bit physical pointer to
                                                 # single linked list of
                                                 # struct setup_data
 
+pref_address:           .quad LOAD_PHYSICAL_ADDR        # preferred load addr
+
+#define ZO_INIT_SIZE    (ZO__end - ZO_startup_32 + ZO_extract_offset)
+#define VO_INIT_SIZE    (VO__end - VO__text)
+#if ZO_INIT_SIZE > VO_INIT_SIZE
+#define INIT_SIZE ZO_INIT_SIZE
+#else
+#define INIT_SIZE VO_INIT_SIZE
+#endif
+init_size:              .long INIT_SIZE         # kernel initialization size
+
 # End of setup header #####################################################
 
         .section ".inittext", "ax"