[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>

arch/powerpc/kernel/btext.c

@@ -60,7 +60,7 @@ int force_printk_to_btext = 0;
  *
  * The display is mapped to virtual address 0xD0000000, rather
  * than 1:1, because some some CHRP machines put the frame buffer
- * in the region starting at 0xC0000000 (KERNELBASE).
+ * in the region starting at 0xC0000000 (PAGE_OFFSET).
  * This mapping is temporary and will disappear as soon as the
  * setup done by MMU_Init() is applied.
  *
@@ -71,7 +71,7 @@ int force_printk_to_btext = 0;
  */
 void __init btext_prepare_BAT(void)
 {
-	unsigned long vaddr = KERNELBASE + 0x10000000;
+	unsigned long vaddr = PAGE_OFFSET + 0x10000000;
 	unsigned long addr;
 	unsigned long lowbits;
 

arch/powerpc/kernel/entry_64.S

@@ -690,7 +690,7 @@ _GLOBAL(enter_rtas)
 
 	/* Setup our real return addr */	
 	SET_REG_TO_LABEL(r4,.rtas_return_loc)
-	SET_REG_TO_CONST(r9,KERNELBASE)
+	SET_REG_TO_CONST(r9,PAGE_OFFSET)
 	sub	r4,r4,r9
        	mtlr	r4
 
@@ -718,7 +718,7 @@ _GLOBAL(enter_rtas)
 _STATIC(rtas_return_loc)
 	/* relocation is off at this point */
 	mfspr	r4,SPRN_SPRG3	        /* Get PACA */
-	SET_REG_TO_CONST(r5, KERNELBASE)
+	SET_REG_TO_CONST(r5, PAGE_OFFSET)
         sub     r4,r4,r5                /* RELOC the PACA base pointer */
 
 	mfmsr   r6

arch/powerpc/kernel/lparmap.c

@@ -16,8 +16,8 @@ const struct LparMap __attribute__((__section__(".text"))) xLparMap = {
 	.xSegmentTableOffs = STAB0_PAGE,
 
 	.xEsids = {
-		{ .xKernelEsid = GET_ESID(KERNELBASE),
-		  .xKernelVsid = KERNEL_VSID(KERNELBASE), },
+		{ .xKernelEsid = GET_ESID(PAGE_OFFSET),
+		  .xKernelVsid = KERNEL_VSID(PAGE_OFFSET), },
 		{ .xKernelEsid = GET_ESID(VMALLOCBASE),
 		  .xKernelVsid = KERNEL_VSID(VMALLOCBASE), },
 	},
@@ -25,7 +25,7 @@ const struct LparMap __attribute__((__section__(".text"))) xLparMap = {
 	.xRanges = {
 		{ .xPages = HvPagesToMap,
 		  .xOffset = 0,
-		  .xVPN = KERNEL_VSID(KERNELBASE) << (SID_SHIFT - HW_PAGE_SHIFT),
+		  .xVPN = KERNEL_VSID(PAGE_OFFSET) << (SID_SHIFT - HW_PAGE_SHIFT),
 		},
 	},
 };

arch/powerpc/kernel/machine_kexec_64.c

@@ -153,9 +153,8 @@ void kexec_copy_flush(struct kimage *image)
 	 * including ones that were in place on the original copy
 	 */
 	for (i = 0; i < nr_segments; i++)
-		flush_icache_range(ranges[i].mem + KERNELBASE,
-				ranges[i].mem + KERNELBASE +
-				ranges[i].memsz);
+		flush_icache_range((unsigned long)__va(ranges[i].mem),
+			(unsigned long)__va(ranges[i].mem + ranges[i].memsz));
 }
 
 #ifdef CONFIG_SMP

arch/powerpc/mm/hash_utils_64.c

@@ -456,7 +456,7 @@ void __init htab_initialize(void)
 
 	/* create bolted the linear mapping in the hash table */
 	for (i=0; i < lmb.memory.cnt; i++) {
-		base = lmb.memory.region[i].base + KERNELBASE;
+		base = (unsigned long)__va(lmb.memory.region[i].base);
 		size = lmb.memory.region[i].size;
 
 		DBG("creating mapping for region: %lx : %lx\n", base, size);
@@ -498,8 +498,8 @@ void __init htab_initialize(void)
 	 * for either 4K or 16MB pages.
 	 */
 	if (tce_alloc_start) {
-		tce_alloc_start += KERNELBASE;
-		tce_alloc_end += KERNELBASE;
+		tce_alloc_start = (unsigned long)__va(tce_alloc_start);
+		tce_alloc_end = (unsigned long)__va(tce_alloc_end);
 
 		if (base + size >= tce_alloc_start)
 			tce_alloc_start = base + size + 1;

arch/powerpc/mm/slb.c

@@ -75,7 +75,7 @@ static void slb_flush_and_rebolt(void)
 	vflags = SLB_VSID_KERNEL | virtual_llp;
 
 	ksp_esid_data = mk_esid_data(get_paca()->kstack, 2);
-	if ((ksp_esid_data & ESID_MASK) == KERNELBASE)
+	if ((ksp_esid_data & ESID_MASK) == PAGE_OFFSET)
 		ksp_esid_data &= ~SLB_ESID_V;
 
 	/* We need to do this all in asm, so we're sure we don't touch
@@ -213,7 +213,7 @@ void slb_initialize(void)
 	asm volatile("isync":::"memory");
 	asm volatile("slbmte  %0,%0"::"r" (0) : "memory");
 	asm volatile("isync; slbia; isync":::"memory");
-	create_slbe(KERNELBASE, lflags, 0);
+	create_slbe(PAGE_OFFSET, lflags, 0);
 
 	/* VMALLOC space has 4K pages always for now */
 	create_slbe(VMALLOCBASE, vflags, 1);

arch/powerpc/mm/slb_low.S

@@ -37,9 +37,9 @@ _GLOBAL(slb_allocate_realmode)
 
 	srdi	r9,r3,60		/* get region */
 	srdi	r10,r3,28		/* get esid */
-	cmpldi	cr7,r9,0xc		/* cmp KERNELBASE for later use */
+	cmpldi	cr7,r9,0xc		/* cmp PAGE_OFFSET for later use */
 
-	/* r3 = address, r10 = esid, cr7 = <>KERNELBASE */
+	/* r3 = address, r10 = esid, cr7 = <> PAGE_OFFSET */
 	blt	cr7,0f			/* user or kernel? */
 
 	/* kernel address: proto-VSID = ESID */
@@ -166,7 +166,7 @@ _GLOBAL(slb_allocate_user)
 /*
  * Finish loading of an SLB entry and return
  *
- * r3 = EA, r10 = proto-VSID, r11 = flags, clobbers r9, cr7 = <>KERNELBASE
+ * r3 = EA, r10 = proto-VSID, r11 = flags, clobbers r9, cr7 = <> PAGE_OFFSET
  */
 slb_finish_load:
 	ASM_VSID_SCRAMBLE(r10,r9)

arch/powerpc/mm/stab.c

@@ -40,7 +40,7 @@ static int make_ste(unsigned long stab, unsigned long esid, unsigned long vsid)
 	unsigned long entry, group, old_esid, castout_entry, i;
 	unsigned int global_entry;
 	struct stab_entry *ste, *castout_ste;
-	unsigned long kernel_segment = (esid << SID_SHIFT) >= KERNELBASE;
+	unsigned long kernel_segment = (esid << SID_SHIFT) >= PAGE_OFFSET;
 
 	vsid_data = vsid << STE_VSID_SHIFT;
 	esid_data = esid << SID_SHIFT | STE_ESID_KP | STE_ESID_V;
@@ -83,7 +83,7 @@ static int make_ste(unsigned long stab, unsigned long esid, unsigned long vsid)
 		}
 
 		/* Dont cast out the first kernel segment */
-		if ((castout_ste->esid_data & ESID_MASK) != KERNELBASE)
+		if ((castout_ste->esid_data & ESID_MASK) != PAGE_OFFSET)
 			break;
 
 		castout_entry = (castout_entry + 1) & 0xf;
@@ -251,7 +251,7 @@ void stabs_alloc(void)
 			panic("Unable to allocate segment table for CPU %d.\n",
 			      cpu);
 
-		newstab += KERNELBASE;
+		newstab = (unsigned long)__va(newstab);
 
 		memset((void *)newstab, 0, HW_PAGE_SIZE);
 
@@ -270,11 +270,11 @@ void stabs_alloc(void)
  */
 void stab_initialize(unsigned long stab)
 {
-	unsigned long vsid = get_kernel_vsid(KERNELBASE);
+	unsigned long vsid = get_kernel_vsid(PAGE_OFFSET);
 	unsigned long stabreal;
 
 	asm volatile("isync; slbia; isync":::"memory");
-	make_ste(stab, GET_ESID(KERNELBASE), vsid);
+	make_ste(stab, GET_ESID(PAGE_OFFSET), vsid);
 
 	/* Order update */
 	asm volatile("sync":::"memory");

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)
 
 /*