[PATCH] i386: Relocatable kernel support

This patch modifies the i386 kernel so that if CONFIG_RELOCATABLE is
selected it will be able to be loaded at any 4K aligned address below
1G.  The technique used is to compile the decompressor with -fPIC and
modify it so the decompressor is fully relocatable.  For the main
kernel relocations are generated.  Resulting in a kernel that is relocatable
with no runtime overhead and no need to modify the source code.

A reserved 32bit word in the parameters has been assigned
to serve as a stack so we figure out where are running.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 8ff1c6fb5aa1..d588ca874bb4 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -773,6 +773,18 @@ config CRASH_DUMP
           PHYSICAL_START.
           For more details see Documentation/kdump/kdump.txt
 
+config RELOCATABLE
+        bool "Build a relocatable kernel"
+        help
+          This build a kernel image that retains relocation information
+          so it can be loaded someplace besides the default 1MB.
+          The relocations tend to the kernel binary about 10% larger,
+          but are discarded at runtime.
+
+          One use is for the kexec on panic case where the recovery kernel
+          must live at a different physical address than the primary
+          kernel.
+
 config PHYSICAL_START
         hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP)