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Subject[PATCH 11/11] i386: Extend bzImage protocol for relocatable protected mode kernel


o 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)

o 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>
---

Documentation/i386/boot.txt | 4 ++++
arch/i386/boot/setup.S | 13 ++++++++++++-
2 files changed, 16 insertions(+), 1 deletion(-)

diff -puN arch/i386/boot/setup.S~extend-bzImage-protocol-for-relocatable-protected-mode-kernel arch/i386/boot/setup.S
--- linux-2.6.19-rc2-git7-reloc/arch/i386/boot/setup.S~extend-bzImage-protocol-for-relocatable-protected-mode-kernel 2006-10-23 15:09:28.000000000 -0400
+++ linux-2.6.19-rc2-git7-reloc-root/arch/i386/boot/setup.S 2006-10-23 15:09:28.000000000 -0400
@@ -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
# 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
diff -puN Documentation/i386/boot.txt~extend-bzImage-protocol-for-relocatable-protected-mode-kernel Documentation/i386/boot.txt
--- linux-2.6.19-rc2-git7-reloc/Documentation/i386/boot.txt~extend-bzImage-protocol-for-relocatable-protected-mode-kernel 2006-10-23 15:09:28.000000000 -0400
+++ linux-2.6.19-rc2-git7-reloc-root/Documentation/i386/boot.txt 2006-10-23 15:09:28.000000000 -0400
@@ -35,6 +35,8 @@ Protocol 2.03: (Kernel 2.4.18-pre1) Expl
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.
_
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