Commit dd0ec16f authored by Vivek Goyal's avatar Vivek Goyal Committed by Linus Torvalds
Browse files

[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: default avatarVivek Goyal <vgoyal@in.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a75acf85

arch/i386/Kconfig

+41 −0
Original line number Diff line number Diff line
@@ -777,6 +777,47 @@ config CRASH_DUMP 
          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

include/asm-i386/boot.h

+2 −1
Original line number Diff line number Diff line
@@ -13,7 +13,8 @@ 
#define ASK_VGA		0xfffd		/* ask for it at bootup */



/* Physical address where kenrel should be loaded. */

#define LOAD_PHYSICAL_ADDR ((0x100000 + CONFIG_PHYSICAL_ALIGN - 1) \

#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \

				+ (CONFIG_PHYSICAL_ALIGN - 1)) \

				& ~(CONFIG_PHYSICAL_ALIGN - 1))



#endif /* _LINUX_BOOT_H */

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