[SPARC64]: Do not allow mapping pages within 4GB of 64-bit VA hole.

The UltraSPARC T1 manual recommends this because the chip
could instruction prefetch into the VA hole, and this would
also make decoding  certain kinds of memory access traps
more difficult (because the chip sign extends certain pieces
of trap state).
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/kernel/sys_sparc.c

@@ -33,14 +33,55 @@
 
 /* #define DEBUG_UNIMP_SYSCALL */
 
-/* XXX Make this per-binary type, this way we can detect the type of
- * XXX a binary.  Every Sparc executable calls this very early on.
- */
 asmlinkage unsigned long sys_getpagesize(void)
 {
 	return PAGE_SIZE;
 }
 
+#define VA_EXCLUDE_START (0x0000080000000000UL - (1UL << 32UL))
+#define VA_EXCLUDE_END   (0xfffff80000000000UL + (1UL << 32UL))
+
+/* Does addr --> addr+len fall within 4GB of the VA-space hole or
+ * overflow past the end of the 64-bit address space?
+ */
+static inline int invalid_64bit_range(unsigned long addr, unsigned long len)
+{
+	unsigned long va_exclude_start, va_exclude_end;
+
+	va_exclude_start = VA_EXCLUDE_START;
+	va_exclude_end   = VA_EXCLUDE_END;
+
+	if (unlikely(len >= va_exclude_start))
+		return 1;
+
+	if (unlikely((addr + len) < addr))
+		return 1;
+
+	if (unlikely((addr >= va_exclude_start && addr < va_exclude_end) ||
+		     ((addr + len) >= va_exclude_start &&
+		      (addr + len) < va_exclude_end)))
+		return 1;
+
+	return 0;
+}
+
+/* Does start,end straddle the VA-space hole?  */
+static inline int straddles_64bit_va_hole(unsigned long start, unsigned long end)
+{
+	unsigned long va_exclude_start, va_exclude_end;
+
+	va_exclude_start = VA_EXCLUDE_START;
+	va_exclude_end   = VA_EXCLUDE_END;
+
+	if (likely(start < va_exclude_start && end < va_exclude_start))
+		return 0;
+
+	if (likely(start >= va_exclude_end && end >= va_exclude_end))
+		return 0;
+
+	return 1;
+}
+
 #define COLOUR_ALIGN(addr,pgoff)		\
 	((((addr)+SHMLBA-1)&~(SHMLBA-1)) +	\
 	 (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
@@ -65,7 +106,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsi
 
 	if (test_thread_flag(TIF_32BIT))
 		task_size = 0xf0000000UL;
-	if (len > task_size || len > -PAGE_OFFSET)
+	if (len > task_size || len >= VA_EXCLUDE_START)
 		return -ENOMEM;
 
 	do_color_align = 0;
@@ -100,9 +141,10 @@ full_search:
 
 	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
 		/* At this point:  (!vma || addr < vma->vm_end). */
-		if (addr < PAGE_OFFSET && -PAGE_OFFSET - len < addr) {
-			addr = PAGE_OFFSET;
-			vma = find_vma(mm, PAGE_OFFSET);
+		if (addr < VA_EXCLUDE_START &&
+		    (addr + len) >= VA_EXCLUDE_START) {
+			addr = VA_EXCLUDE_END;
+			vma = find_vma(mm, VA_EXCLUDE_END);
 		}
 		if (task_size < addr) {
 			if (start_addr != TASK_UNMAPPED_BASE) {
@@ -174,12 +216,12 @@ unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, u
 asmlinkage unsigned long sparc_brk(unsigned long brk)
 {
 	/* People could try to be nasty and use ta 0x6d in 32bit programs */
-	if (test_thread_flag(TIF_32BIT) &&
-	    brk >= 0xf0000000UL)
+	if (test_thread_flag(TIF_32BIT) && brk >= 0xf0000000UL)
 		return current->mm->brk;
 
-	if ((current->mm->brk & PAGE_OFFSET) != (brk & PAGE_OFFSET))
+	if (unlikely(straddles_64bit_va_hole(current->mm->brk, brk)))
 		return current->mm->brk;
+
 	return sys_brk(brk);
 }
                                                                 
@@ -340,13 +382,16 @@ asmlinkage unsigned long sys_mmap(unsigned long addr, unsigned long len,
 	retval = -EINVAL;
 
 	if (test_thread_flag(TIF_32BIT)) {
-		if (len > 0xf0000000UL ||
-		    ((flags & MAP_FIXED) && addr > 0xf0000000UL - len))
+		if (len >= 0xf0000000UL)
+			goto out_putf;
+
+		if ((flags & MAP_FIXED) && addr > 0xf0000000UL - len)
 			goto out_putf;
 	} else {
-		if (len > -PAGE_OFFSET ||
-		    ((flags & MAP_FIXED) &&
-		     addr < PAGE_OFFSET && addr + len > -PAGE_OFFSET))
+		if (len >= VA_EXCLUDE_START)
+			goto out_putf;
+
+		if ((flags & MAP_FIXED) && invalid_64bit_range(addr, len))
 			goto out_putf;
 	}
 
@@ -365,9 +410,9 @@ asmlinkage long sys64_munmap(unsigned long addr, size_t len)
 {
 	long ret;
 
-	if (len > -PAGE_OFFSET ||
-	    (addr < PAGE_OFFSET && addr + len > -PAGE_OFFSET))
+	if (invalid_64bit_range(addr, len))
 		return -EINVAL;
+
 	down_write(&current->mm->mmap_sem);
 	ret = do_munmap(current->mm, addr, len);
 	up_write(&current->mm->mmap_sem);
@@ -384,18 +429,19 @@ asmlinkage unsigned long sys64_mremap(unsigned long addr,
 {
 	struct vm_area_struct *vma;
 	unsigned long ret = -EINVAL;
+
 	if (test_thread_flag(TIF_32BIT))
 		goto out;
-	if (old_len > -PAGE_OFFSET || new_len > -PAGE_OFFSET)
+	if (unlikely(new_len >= VA_EXCLUDE_START))
 		goto out;
-	if (addr < PAGE_OFFSET && addr + old_len > -PAGE_OFFSET)
+	if (unlikely(invalid_64bit_range(addr, old_len)))
 		goto out;
+
 	down_write(&current->mm->mmap_sem);
 	if (flags & MREMAP_FIXED) {
-		if (new_addr < PAGE_OFFSET &&
-		    new_addr + new_len > -PAGE_OFFSET)
+		if (invalid_64bit_range(new_addr, new_len))
 			goto out_sem;
-	} else if (addr < PAGE_OFFSET && addr + new_len > -PAGE_OFFSET) {
+	} else if (invalid_64bit_range(addr, new_len)) {
 		unsigned long map_flags = 0;
 		struct file *file = NULL;
 

include/asm-sparc64/a.out.h

@@ -95,7 +95,9 @@ struct relocation_info /* used when header.a_machtype == M_SPARC */
 
 #ifdef __KERNEL__
 
-#define STACK_TOP (test_thread_flag(TIF_32BIT) ? 0xf0000000 : 0x80000000000L)
+#define STACK_TOP (test_thread_flag(TIF_32BIT) ? \
+		   0xf0000000 : \
+		   (0x0000080000000000UL - (1UL << 32UL)))
 
 #endif
 

include/asm-sparc64/page.h

@@ -107,7 +107,8 @@ typedef unsigned long pgprot_t;
 #endif
 
 #define TASK_UNMAPPED_BASE	(test_thread_flag(TIF_32BIT) ? \
-				 (_AC(0x0000000070000000,UL)) : (PAGE_OFFSET))
+				 (_AC(0x0000000070000000,UL)) : \
+				 (_AC(0xfffff80000000000,UL) + (1UL << 32UL)))
 
 #endif /* !(__ASSEMBLY__) */