[PATCH] i386: extend bzImage protocol for relocatable protected mode kernel

Extend bzImage protocol to enable bootloaders to load a completely relocatable
bzImage.  Now protected mode component of kernel is also relocatable and a
boot-loader can load the protected mode component at a differnt physical
address than 1MB.  (If kernel was built with CONFIG_RELOCATABLE)

Kexec can make use of it to load this kernel at a different physical address
to capture kernel crash dumps.

Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>

2 files changed, 16 insertions, 1 deletions

diff --git a/Documentation/i386/boot.txt b/Documentation/i386/boot.txt
index c51314b1a463..cb28254f1550 100644
--- a/Documentation/i386/boot.txt
+++ b/Documentation/i386/boot.txt
@@ -35,6 +35,8 @@ Protocol 2.03:	(Kernel 2.4.18-pre1) Explicitly makes the highest possible
                 initrd address available to the bootloader.
 
 Protocol 2.04:  (Kernel 2.6.14) Extend the syssize field to four bytes.
+Protocol 2.05:  (Kernel 2.6.20) Make protected mode kernel relocatable.
+                Introduce relocatable_kernel and kernel_alignment fields.
 
 
 **** MEMORY LAYOUT
@@ -129,6 +131,8 @@ Offset	Proto	Name		Meaning
 0226/2  N/A     pad1            Unused
 0228/4  2.02+   cmd_line_ptr    32-bit pointer to the kernel command line
 022C/4  2.03+   initrd_addr_max Highest legal initrd address
+0230/4  2.04+   kernel_alignment Physical addr alignment required for kernel
+0234/1  2.04+   relocatable_kernel Whether kernel is relocatable or not
 
 (1) For backwards compatibility, if the setup_sects field contains 0, the
     real value is 4.
diff --git a/arch/i386/boot/setup.S b/arch/i386/boot/setup.S
index 9aa8b0518184..06edf1c66242 100644
--- a/arch/i386/boot/setup.S
+++ b/arch/i386/boot/setup.S
@@ -81,7 +81,7 @@ start:
 # This is the setup header, and it must start at %cs:2 (old 0x9020:2)
 
                 .ascii  "HdrS"          # header signature
-                .word   0x0204          # header version number (>= 0x0105)
+                .word   0x0205          # header version number (>= 0x0105)
                                         # or else old loadlin-1.5 will fail)
 realmode_swtch: .word   0, 0            # default_switch, SETUPSEG
 start_sys_seg:  .word   SYSSEG
@@ -160,6 +160,17 @@ ramdisk_max:	.long (-__PAGE_OFFSET-(512 << 20)-1) & 0x7fffffff
                                         # The highest safe address for
                                         # the contents of an initrd
 
+kernel_alignment:  .long CONFIG_PHYSICAL_ALIGN  #physical addr alignment
+                                                #required for protected mode
+                                                #kernel
+#ifdef CONFIG_RELOCATABLE
+relocatable_kernel:    .byte 1
+#else
+relocatable_kernel:    .byte 0
+#endif
+pad2:                   .byte 0
+pad3:                   .word 0
+
 trampoline:     call    start_of_setup
                 .align 16
                                         # The offset at this point is 0x240