[PATCH] i386: Restore CONFIG_PHYSICAL_START option
o Relocatable bzImage support had got rid of CONFIG_PHYSICAL_START option
thinking that now this option is not required as people can build a
second kernel as relocatable and load it anywhere. So need of compiling
the kernel for a custom address was gone. But Magnus uses vmlinux images
for second kernel in Xen environment and he wants to continue to use
it.
o Restoring the CONFIG_PHYSICAL_START option for the time being. I think
down the line we can get rid of it.
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 0d67a0a..0dfee81 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -777,6 +777,47 @@
PHYSICAL_START.
For more details see Documentation/kdump/kdump.txt
+config PHYSICAL_START
+ hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP)
+ default "0x100000"
+ help
+ This gives the physical address where the kernel is loaded.
+
+ If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
+ bzImage will decompress itself to above physical address and
+ run from there. Otherwise, bzImage will run from the address where
+ it has been loaded by the boot loader and will ignore above physical
+ address.
+
+ In normal kdump cases one does not have to set/change this option
+ as now bzImage can be compiled as a completely relocatable image
+ (CONFIG_RELOCATABLE=y) and be used to load and run from a different
+ address. This option is mainly useful for the folks who don't want
+ to use a bzImage for capturing the crash dump and want to use a
+ vmlinux instead. vmlinux is not relocatable hence a kernel needs
+ to be specifically compiled to run from a specific memory area
+ (normally a reserved region) and this option comes handy.
+
+ So if you are using bzImage for capturing the crash dump, leave
+ the value here unchanged to 0x100000 and set CONFIG_RELOCATABLE=y.
+ Otherwise if you plan to use vmlinux for capturing the crash dump
+ change this value to start of the reserved region (Typically 16MB
+ 0x1000000). In other words, it can be set based on the "X" value as
+ specified in the "crashkernel=YM@XM" command line boot parameter
+ passed to the panic-ed kernel. Typically this parameter is set as
+ crashkernel=64M@16M. Please take a look at
+ Documentation/kdump/kdump.txt for more details about crash dumps.
+
+ Usage of bzImage for capturing the crash dump is recommended as
+ one does not have to build two kernels. Same kernel can be used
+ as production kernel and capture kernel. Above option should have
+ gone away after relocatable bzImage support is introduced. But it
+ is present because there are users out there who continue to use
+ vmlinux for dump capture. This option should go away down the
+ line.
+
+ Don't change this unless you know what you are doing.
+
config RELOCATABLE
bool "Build a relocatable kernel(EXPERIMENTAL)"
depends on EXPERIMENTAL