From 1ab60e0f72f71ec54831e525a3e1154f1c092408 Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Wed, 2 May 2007 19:27:07 +0200 Subject: [PATCH] x86-64: Relocatable Kernel Support This patch modifies the x86_64 kernel so that it can be loaded and run at any 2M aligned address, below 512G. The technique used is to compile the decompressor with -fPIC and modify it so the decompressor is fully relocatable. For the main kernel the page tables are modified so the kernel remains at the same virtual address. In addition a variable phys_base is kept that holds the physical address the kernel is loaded at. __pa_symbol is modified to add that when we take the address of a kernel symbol. When loaded with a normal bootloader the decompressor will decompress the kernel to 2M and it will run there. This both ensures the relocation code is always working, and makes it easier to use 2M pages for the kernel and the cpu. AK: changed to not make RELOCATABLE default in Kconfig Signed-off-by: Eric W. Biederman Signed-off-by: Vivek Goyal Signed-off-by: Andi Kleen --- include/asm-x86_64/page.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/asm-x86_64/page.h b/include/asm-x86_64/page.h index 4974433bbf34..40a24d0df090 100644 --- a/include/asm-x86_64/page.h +++ b/include/asm-x86_64/page.h @@ -61,6 +61,8 @@ typedef struct { unsigned long pgd; } pgd_t; typedef struct { unsigned long pgprot; } pgprot_t; +extern unsigned long phys_base; + #define pte_val(x) ((x).pte) #define pmd_val(x) ((x).pmd) #define pud_val(x) ((x).pud) @@ -101,14 +103,14 @@ typedef struct { unsigned long pgprot; } pgprot_t; #define PAGE_OFFSET __PAGE_OFFSET /* Note: __pa(&symbol_visible_to_c) should be always replaced with __pa_symbol. - Otherwise you risk miscompilation. */ + Otherwise you risk miscompilation. */ #define __pa(x) ((unsigned long)(x) - PAGE_OFFSET) /* __pa_symbol should be used for C visible symbols. This seems to be the official gcc blessed way to do such arithmetic. */ #define __pa_symbol(x) \ ({unsigned long v; \ asm("" : "=r" (v) : "0" (x)); \ - (v - __START_KERNEL_map); }) + ((v - __START_KERNEL_map) + phys_base); }) #define __va(x) ((void *)((unsigned long)(x)+PAGE_OFFSET)) #ifdef CONFIG_FLATMEM -- cgit v1.2.2