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

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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>
This commit is contained in:
Vivek Goyal 2006-12-07 02:14:04 +01:00 committed by Andi Kleen
parent e69f202d0a
commit be274eeaf2
2 changed files with 16 additions and 1 deletions
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4
Documentation/i386/boot.txt
View file

@ -35,6 +35,8 @@ Protocol 2.03: (Kernel 2.4.18-pre1) Explicitly makes the highest possible
initrd address available to the bootloader. initrd address available to the bootloader.
Protocol 2.04: (Kernel 2.6.14) Extend the syssize field to four bytes. 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 **** MEMORY LAYOUT
@ -129,6 +131,8 @@ Offset Proto Name Meaning
0226/2 N/A pad1 Unused 0226/2 N/A pad1 Unused
0228/4 2.02+ cmd_line_ptr 32-bit pointer to the kernel command line 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 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 (1) For backwards compatibility, if the setup_sects field contains 0, the
real value is 4. real value is 4.

13
arch/i386/boot/setup.S
View file

@ -81,7 +81,7 @@ start:
# This is the setup header, and it must start at %cs:2 (old 0x9020:2) # This is the setup header, and it must start at %cs:2 (old 0x9020:2)
.ascii "HdrS" # header signature .ascii "HdrS" # header signature
.word 0x0204 # header version number (>= 0x0105) .word 0x0205 # header version number (>= 0x0105)
# or else old loadlin-1.5 will fail) # or else old loadlin-1.5 will fail)
realmode_swtch: .word 0, 0 # default_switch, SETUPSEG realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
start_sys_seg: .word SYSSEG start_sys_seg: .word SYSSEG
@ -160,6 +160,17 @@ ramdisk_max: .long (-__PAGE_OFFSET-(512 << 20)-1) & 0x7fffffff
# The highest safe address for # The highest safe address for
# the contents of an initrd # 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 trampoline: call start_of_setup
.align 16 .align 16
# The offset at this point is 0x240 # The offset at this point is 0x240