1 files changed, 30 insertions, 2 deletions

diff --git a/include/asm-powerpc/page.h b/include/asm-powerpc/page.h
index 18c1e5ee81a3..76d7cb4b4ffc 100644
--- a/include/asm-powerpc/page.h
+++ b/include/asm-powerpc/page.h
@@ -37,8 +37,30 @@
  */
 #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().
+ */
+
+#ifdef CONFIG_CRASH_DUMP
+/* Kdump kernel runs at 32 MB, change at your peril. */
+#define PHYSICAL_START  0x2000000
+#else
+#define PHYSICAL_START  0x0
+#endif
+
 #define PAGE_OFFSET     ASM_CONST(CONFIG_KERNEL_START)
-#define KERNELBASE      PAGE_OFFSET
+#define KERNELBASE      (PAGE_OFFSET + PHYSICAL_START)
 
 #ifdef CONFIG_DISCONTIGMEM
 #define page_to_pfn(page)       discontigmem_page_to_pfn(page)
@@ -56,7 +78,7 @@
 #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)
 
 /*
@@ -86,6 +108,12 @@
 /* to align the pointer to the (next) page boundary */
 #define PAGE_ALIGN(addr)        _ALIGN(addr, PAGE_SIZE)
 
+/*
+ * Don't compare things with KERNELBASE or PAGE_OFFSET to test for
+ * "kernelness", use is_kernel_addr() - it should do what you want.
+ */
+#define is_kernel_addr(x)       ((x) >= PAGE_OFFSET)
+
 #ifndef __ASSEMBLY__
 
 #undef STRICT_MM_TYPECHECKS