diff options
| author | Michael Ellerman <michael@ellerman.id.au> | 2005-12-05 10:24:33 -0600 |
|---|---|---|
| committer | Paul Mackerras <paulus@samba.org> | 2006-01-09 14:51:54 +1100 |
| commit | b5666f70395016a55cc9d57826508b8a346398d0 (patch) | |
| tree | 39d74718c2bc3f2fcba6456fdc39a6a0de3d78bd /include/asm-powerpc/page.h | |
| parent | 51fae6de24da57bc6cdaa1b253595c3513ecbf2d (diff) | |
| download | linux-b5666f70395016a55cc9d57826508b8a346398d0.tar.bz2 | |
[PATCH] powerpc: Separate usage of KERNELBASE and PAGE_OFFSET
This patch separates usage of KERNELBASE and PAGE_OFFSET. I haven't
looked at any of the PPC32 code, if we ever want to support Kdump on
PPC we'll have to do another audit, ditto for iSeries.
This patch makes PAGE_OFFSET the constant, it'll always be 0xC * 1
gazillion for 64-bit.
To get a physical address from a virtual one you subtract PAGE_OFFSET,
_not_ KERNELBASE.
KERNELBASE is the virtual address of the start of the kernel, it's
often the same as PAGE_OFFSET, but _might not be_.
If you want to know something's offset from the start of the kernel
you should subtract KERNELBASE.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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) /* |