[SPARC64]: Add CONFIG_DEBUG_PAGEALLOC support.

The trick is that we do the kernel linear mapping TLB miss starting
with an instruction sequence like this:

	ba,pt		%xcc, kvmap_load
	 xor		%g2, %g4, %g5

succeeded by an instruction sequence which performs a full page table
walk starting at swapper_pg_dir.

We first take over the trap table from the firmware.  Then, using this
constant PTE generation for the linear mapping area above, we build
the kernel page tables for the linear mapping.

After this is setup, we patch that branch above into a "nop", which
will cause TLB misses to fall through to the full page table walk.

With this, the page unmapping for CONFIG_DEBUG_PAGEALLOC is trivial.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/Kconfig.debug

@@ -33,6 +33,14 @@ config DEBUG_BOOTMEM
 	depends on DEBUG_KERNEL
 	bool "Debug BOOTMEM initialization"
 
+config DEBUG_PAGEALLOC
+	bool "Page alloc debugging"
+	depends on DEBUG_KERNEL && !SOFTWARE_SUSPEND
+	help
+	  Unmap pages from the kernel linear mapping after free_pages().
+	  This results in a large slowdown, but helps to find certain types
+	  of memory corruptions.
+
 config MCOUNT
 	bool
 	depends on STACK_DEBUG

arch/sparc64/kernel/head.S

@@ -525,12 +525,6 @@ bootup_user_stack_end:
 
 #include "ttable.S"
 #include "systbls.S"
-
-	.align	1024
-	.globl	swapper_pg_dir
-swapper_pg_dir:
-	.word	0
-
 #include "ktlb.S"
 #include "etrap.S"
 #include "rtrap.S"

arch/sparc64/kernel/ktlb.S

@@ -132,9 +132,40 @@ kvmap_do_obp:
  */
 	.align		32
 kvmap:
-	brlz,pt		%g4, kvmap_load
+	brgez,pn	%g4, kvmap_nonlinear
+	 nop
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
+	.globl		kvmap_linear_patch
+kvmap_linear_patch:
+#endif
+	ba,pt		%xcc, kvmap_load
 	 xor		%g2, %g4, %g5
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+	sethi		%hi(swapper_pg_dir), %g5
+	or		%g5, %lo(swapper_pg_dir), %g5
+	sllx		%g4, 64 - (PGDIR_SHIFT + PGDIR_BITS), %g6
+	srlx		%g6, 64 - PAGE_SHIFT, %g6
+	andn		%g6, 0x3, %g6
+	lduw		[%g5 + %g6], %g5
+	brz,pn		%g5, longpath
+	 sllx		%g4, 64 - (PMD_SHIFT + PMD_BITS), %g6
+	srlx		%g6, 64 - PAGE_SHIFT, %g6
+	sllx		%g5, 11, %g5
+	andn		%g6, 0x3, %g6
+	lduwa		[%g5 + %g6] ASI_PHYS_USE_EC, %g5
+	brz,pn		%g5, longpath
+	 sllx		%g4, 64 - PMD_SHIFT, %g6
+	srlx		%g6, 64 - PAGE_SHIFT, %g6
+	sllx		%g5, 11, %g5
+	andn		%g6, 0x7, %g6
+	ldxa		[%g5 + %g6] ASI_PHYS_USE_EC, %g5
+	brz,pn		%g5, longpath
+	 nop
+	ba,a,pt		%xcc, kvmap_load
+#endif
+
 kvmap_nonlinear:
 	sethi		%hi(MODULES_VADDR), %g5
 	cmp		%g4, %g5

arch/sparc64/kernel/vmlinux.lds.S

@@ -9,8 +9,7 @@ ENTRY(_start)
 jiffies = jiffies_64;
 SECTIONS
 {
-  swapper_pmd_dir = 0x0000000000402000;
-  empty_pg_dir = 0x0000000000403000;
+  swapper_low_pmd_dir = 0x0000000000402000;
   . = 0x4000;
   .text 0x0000000000404000 :
   {

arch/sparc64/mm/init.c

@@ -1332,15 +1332,114 @@ unsigned long __init bootmem_init(unsigned long *pages_avail)
 	return end_pfn;
 }
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+static unsigned long kernel_map_range(unsigned long pstart, unsigned long pend, pgprot_t prot)
+{
+	unsigned long vstart = PAGE_OFFSET + pstart;
+	unsigned long vend = PAGE_OFFSET + pend;
+	unsigned long alloc_bytes = 0UL;
+
+	if ((vstart & ~PAGE_MASK) || (vend & ~PAGE_MASK)) {
+		prom_printf("kernel_map: Unaligned sp_banks[%lx:%lx]\n",
+			    vstart, vend);
+		prom_halt();
+	}
+
+	while (vstart < vend) {
+		unsigned long this_end, paddr = __pa(vstart);
+		pgd_t *pgd = pgd_offset_k(vstart);
+		pud_t *pud;
+		pmd_t *pmd;
+		pte_t *pte;
+
+		pud = pud_offset(pgd, vstart);
+		if (pud_none(*pud)) {
+			pmd_t *new;
+
+			new = __alloc_bootmem(PAGE_SIZE, PAGE_SIZE, PAGE_SIZE);
+			alloc_bytes += PAGE_SIZE;
+			pud_populate(&init_mm, pud, new);
+		}
+
+		pmd = pmd_offset(pud, vstart);
+		if (!pmd_present(*pmd)) {
+			pte_t *new;
+
+			new = __alloc_bootmem(PAGE_SIZE, PAGE_SIZE, PAGE_SIZE);
+			alloc_bytes += PAGE_SIZE;
+			pmd_populate_kernel(&init_mm, pmd, new);
+		}
+
+		pte = pte_offset_kernel(pmd, vstart);
+		this_end = (vstart + PMD_SIZE) & PMD_MASK;
+		if (this_end > vend)
+			this_end = vend;
+
+		while (vstart < this_end) {
+			pte_val(*pte) = (paddr | pgprot_val(prot));
+
+			vstart += PAGE_SIZE;
+			paddr += PAGE_SIZE;
+			pte++;
+		}
+	}
+
+	return alloc_bytes;
+}
+
+extern struct linux_mlist_p1275 *prom_ptot_ptr;
+extern unsigned int kvmap_linear_patch[1];
+
+static void __init kernel_physical_mapping_init(void)
+{
+	struct linux_mlist_p1275 *p = prom_ptot_ptr;
+	unsigned long mem_alloced = 0UL;
+
+	while (p) {
+		unsigned long phys_start, phys_end;
+
+		phys_start = p->start_adr;
+		phys_end = phys_start + p->num_bytes;
+		mem_alloced += kernel_map_range(phys_start, phys_end,
+						PAGE_KERNEL);
+
+		p = p->theres_more;
+	}
+
+	printk("Allocated %ld bytes for kernel page tables.\n",
+	       mem_alloced);
+
+	kvmap_linear_patch[0] = 0x01000000; /* nop */
+	flushi(&kvmap_linear_patch[0]);
+
+	__flush_tlb_all();
+}
+
+void kernel_map_pages(struct page *page, int numpages, int enable)
+{
+	unsigned long phys_start = page_to_pfn(page) << PAGE_SHIFT;
+	unsigned long phys_end = phys_start + (numpages * PAGE_SIZE);
+
+	kernel_map_range(phys_start, phys_end,
+			 (enable ? PAGE_KERNEL : __pgprot(0)));
+
+	/* we should perform an IPI and flush all tlbs,
+	 * but that can deadlock->flush only current cpu.
+	 */
+	__flush_tlb_kernel_range(PAGE_OFFSET + phys_start,
+				 PAGE_OFFSET + phys_end);
+}
+#endif
+
 /* paging_init() sets up the page tables */
 
 extern void cheetah_ecache_flush_init(void);
 
 static unsigned long last_valid_pfn;
+pgd_t swapper_pg_dir[2048];
 
 void __init paging_init(void)
 {
-	extern pmd_t swapper_pmd_dir[1024];
 	unsigned long end_pfn, pages_avail, shift;
 	unsigned long real_end;
 
@@ -1361,11 +1460,11 @@ void __init paging_init(void)
 	 */
 	init_mm.pgd += ((shift) / (sizeof(pgd_t)));
 
-	memset(swapper_pmd_dir, 0, sizeof(swapper_pmd_dir));
+	memset(swapper_low_pmd_dir, 0, sizeof(swapper_low_pmd_dir));
 
 	/* Now can init the kernel/bad page tables. */
 	pud_set(pud_offset(&swapper_pg_dir[0], 0),
-		swapper_pmd_dir + (shift / sizeof(pgd_t)));
+		swapper_low_pmd_dir + (shift / sizeof(pgd_t)));
 
 	swapper_pgd_zero = pgd_val(swapper_pg_dir[0]);
 
@@ -1390,6 +1489,10 @@ void __init paging_init(void)
 	pages_avail = 0;
 	last_valid_pfn = end_pfn = bootmem_init(&pages_avail);
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+	kernel_physical_mapping_init();
+#endif
+
 	{
 		unsigned long zones_size[MAX_NR_ZONES];
 		unsigned long zholes_size[MAX_NR_ZONES];

include/asm-sparc64/cacheflush.h

@@ -66,6 +66,11 @@ extern void flush_ptrace_access(struct vm_area_struct *, struct page *,
 #define flush_cache_vmap(start, end)		do { } while (0)
 #define flush_cache_vunmap(start, end)		do { } while (0)
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+/* internal debugging function */
+void kernel_map_pages(struct page *page, int numpages, int enable);
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* _SPARC64_CACHEFLUSH_H */

include/asm-sparc64/pgtable.h

@@ -60,13 +60,13 @@
  * table can map
  */
 #define PMD_SHIFT	(PAGE_SHIFT + (PAGE_SHIFT-3))
-#define PMD_SIZE	(1UL << PMD_SHIFT)
+#define PMD_SIZE	(_AC(1,UL) << PMD_SHIFT)
 #define PMD_MASK	(~(PMD_SIZE-1))
 #define PMD_BITS	(PAGE_SHIFT - 2)
 
 /* PGDIR_SHIFT determines what a third-level page table entry can map */
 #define PGDIR_SHIFT	(PAGE_SHIFT + (PAGE_SHIFT-3) + PMD_BITS)
-#define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
+#define PGDIR_SIZE	(_AC(1,UL) << PGDIR_SHIFT)
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))
 #define PGDIR_BITS	(PAGE_SHIFT - 2)
 
@@ -336,7 +336,8 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *p
 #define pte_clear(mm,addr,ptep)		\
 	set_pte_at((mm), (addr), (ptep), __pte(0UL))
 
-extern pgd_t swapper_pg_dir[1];
+extern pgd_t swapper_pg_dir[2048];
+extern pmd_t swapper_low_pmd_dir[2048];
 
 /* These do nothing with the way I have things setup. */
 #define mmu_lockarea(vaddr, len)		(vaddr)