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authorPaul Mackerras <paulus@samba.org>2008-08-29 21:43:47 -0400
committerPaul Mackerras <paulus@samba.org>2008-09-15 14:08:38 -0400
commit549e8152de8039506f69c677a4546e5427aa6ae7 (patch)
treee03a4f46143a23045e456f96fc08beba12e73073 /arch/powerpc/Kconfig
parente31aa453bbc4886a7bd33e5c2afa526d6f55bd7a (diff)
powerpc: Make the 64-bit kernel as a position-independent executable
This implements CONFIG_RELOCATABLE for 64-bit by making the kernel as a position-independent executable (PIE) when it is set. This involves processing the dynamic relocations in the image in the early stages of booting, even if the kernel is being run at the address it is linked at, since the linker does not necessarily fill in words in the image for which there are dynamic relocations. (In fact the linker does fill in such words for 64-bit executables, though not for 32-bit executables, so in principle we could avoid calling relocate() entirely when we're running a 64-bit kernel at the linked address.) The dynamic relocations are processed by a new function relocate(addr), where the addr parameter is the virtual address where the image will be run. In fact we call it twice; once before calling prom_init, and again when starting the main kernel. This means that reloc_offset() returns 0 in prom_init (since it has been relocated to the address it is running at), which necessitated a few adjustments. This also changes __va and __pa to use an equivalent definition that is simpler. With the relocatable kernel, PAGE_OFFSET and MEMORY_START are constants (for 64-bit) whereas PHYSICAL_START is a variable (and KERNELBASE ideally should be too, but isn't yet). With this, relocatable kernels still copy themselves down to physical address 0 and run there. Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/Kconfig')
-rw-r--r--arch/powerpc/Kconfig13
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 587da5e0990f..17c988b678d1 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -806,6 +806,19 @@ config PIN_TLB
806endmenu 806endmenu
807 807
808if PPC64 808if PPC64
809config RELOCATABLE
810 bool "Build a relocatable kernel"
811 help
812 This builds a kernel image that is capable of running anywhere
813 in the RMA (real memory area) at any 16k-aligned base address.
814 The kernel is linked as a position-independent executable (PIE)
815 and contains dynamic relocations which are processed early
816 in the bootup process.
817
818 One use is for the kexec on panic case where the recovery kernel
819 must live at a different physical address than the primary
820 kernel.
821
809config PAGE_OFFSET 822config PAGE_OFFSET
810 hex 823 hex
811 default "0xc000000000000000" 824 default "0xc000000000000000"