diff options
Diffstat (limited to 'arch/x86_64/Kconfig')
| -rw-r--r-- | arch/x86_64/Kconfig | 49 |
1 files changed, 41 insertions, 8 deletions
diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig index b3dbf11eb82c..715632026073 100644 --- a/arch/x86_64/Kconfig +++ b/arch/x86_64/Kconfig @@ -565,23 +565,56 @@ config CRASH_DUMP PHYSICAL_START. For more details see Documentation/kdump/kdump.txt +config RELOCATABLE + bool "Build a relocatable kernel(EXPERIMENTAL)" + depends on EXPERIMENTAL + help + Builds a relocatable kernel. This enables loading and running + a kernel binary from a different physical address than it has + been compiled for. + + One use is for the kexec on panic case where the recovery kernel + must live at a different physical address than the primary + kernel. + + Note: If CONFIG_RELOCATABLE=y, then kernel run from the address + it has been loaded at and compile time physical address + (CONFIG_PHYSICAL_START) is ignored. + config PHYSICAL_START hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP) - default "0x1000000" if CRASH_DUMP default "0x200000" help - This gives the physical address where the kernel is loaded. Normally - for regular kernels this value is 0x200000 (2MB). But in the case - of kexec on panic the fail safe kernel needs to run at a different - address than the panic-ed kernel. This option is used to set the load - address for kernels used to capture crash dump on being kexec'ed - after panic. The default value for crash dump kernels is - 0x1000000 (16MB). This can also be set based on the "X" value as + This gives the physical address where the kernel is loaded. It + should be aligned to 2MB boundary. + + 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. + + So if you are using bzImage for capturing the crash dump, leave + the value here unchanged to 0x200000 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 advantageous as + one does not have to build two kernels. Same kernel can be used + as production kernel and capture kernel. + Don't change this unless you know what you are doing. config SECCOMP |