diff options
Diffstat (limited to 'include/asm-powerpc/page.h')
| -rw-r--r-- | include/asm-powerpc/page.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/include/asm-powerpc/page.h b/include/asm-powerpc/page.h index 94905ba2cf41..4696bdbcc085 100644 --- a/include/asm-powerpc/page.h +++ b/include/asm-powerpc/page.h @@ -37,6 +37,20 @@ */ #define PAGE_MASK (~((1 << PAGE_SHIFT) - 1)) +/* + * KERNELBASE is the virtual address of the start of the kernel, it's often + * the same as PAGE_OFFSET, but _might not be_. + * + * The kdump dump kernel is one example where KERNELBASE != PAGE_OFFSET. + * + * To get a physical address from a virtual one you subtract PAGE_OFFSET, + * _not_ KERNELBASE. + * + * If you want to know something's offset from the start of the kernel you + * should subtract KERNELBASE. + * + * If you want to test if something's a kernel address, use is_kernel_addr(). + */ #define PAGE_OFFSET ASM_CONST(CONFIG_KERNEL_START) #define KERNELBASE PAGE_OFFSET @@ -56,7 +70,7 @@ #define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT) #define virt_addr_valid(kaddr) pfn_valid(__pa(kaddr) >> PAGE_SHIFT) -#define __va(x) ((void *)((unsigned long)(x) + KERNELBASE)) +#define __va(x) ((void *)((unsigned long)(x) + PAGE_OFFSET)) #define __pa(x) ((unsigned long)(x) - PAGE_OFFSET) /* |