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Commit be274eea authored by Vivek Goyal's avatar Vivek Goyal Committed by Andi Kleen
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[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: default avatarVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
parent e69f202d

Documentation/i386/boot.txt

+4 −0
Original line number Diff line number Diff line
@@ -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.

arch/i386/boot/setup.S

+12 −1
Original line number Diff line number Diff line
@@ -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