From dc21af99fadcfa0ae65b52fd0895f85824f0c288 Mon Sep 17 00:00:00 2001 From: Russell King Date: Tue, 4 Jan 2011 19:09:43 +0000 Subject: ARM: P2V: introduce phys_to_virt/virt_to_phys runtime patching This idea came from Nicolas, Eric Miao produced an initial version, which was then rewritten into this. Patch the physical to virtual translations at runtime. As we modify the code, this makes it incompatible with XIP kernels, but allows us to achieve this with minimal loss of performance. As many translations are of the form: physical = virtual + (PHYS_OFFSET - PAGE_OFFSET) virtual = physical - (PHYS_OFFSET - PAGE_OFFSET) we generate an 'add' instruction for __virt_to_phys(), and a 'sub' instruction for __phys_to_virt(). We calculate at run time (PHYS_OFFSET - PAGE_OFFSET) by comparing the address prior to MMU initialization with where it should be once the MMU has been initialized, and place this constant into the above add/sub instructions. Once we have (PHYS_OFFSET - PAGE_OFFSET), we can calculate the real PHYS_OFFSET as PAGE_OFFSET is a build-time constant, and save this for the C-mode PHYS_OFFSET variable definition to use. At present, we are unable to support Realview with Sparsemem enabled as this uses a complex mapping function, and MSM as this requires a constant which will not fit in our math instruction. Add a module version magic string for this feature to prevent incompatible modules being loaded. Tested-by: Tony Lindgren Reviewed-by: Nicolas Pitre Tested-by: Nicolas Pitre Signed-off-by: Russell King --- arch/arm/kernel/vmlinux.lds.S | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/arm/kernel/vmlinux.lds.S') diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index 86b66f3f2031..45b5651777ee 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -57,6 +57,10 @@ SECTIONS __smpalt_end = .; #endif + __pv_table_begin = .; + *(.pv_table) + __pv_table_end = .; + INIT_SETUP(16) INIT_CALLS -- cgit v1.2.3