parisc: Enable KASLR

Add missing code for userspace executable address randomization, e.g.
applications compiled with the gcc -pie option.

Signed-off-by: Helge Deller <[e-mail]>

arch/parisc/Kconfig

···
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_SYSCALL_TRACEPOINTS
 	select ARCH_WANT_FRAME_POINTERS
+	select ARCH_HAS_ELF_RANDOMIZE
 	select RTC_CLASS
 	select RTC_DRV_GENERIC
 	select INIT_ALL_POSSIBLE

arch/parisc/include/asm/elf.h

···
 
 #define ELF_HWCAP	0
 
-#define STACK_RND_MASK	(is_32bit_task() ? \
-				0x7ff >> (PAGE_SHIFT - 12) : \
-				0x3ffff >> (PAGE_SHIFT - 12))
+/* Masks for stack and mmap randomization */
+#define BRK_RND_MASK	(is_32bit_task() ? 0x07ffUL : 0x3ffffUL)
+#define MMAP_RND_MASK	(is_32bit_task() ? 0x1fffUL : 0x3ffffUL)
+#define STACK_RND_MASK	MMAP_RND_MASK
 
 struct mm_struct;
 extern unsigned long arch_randomize_brk(struct mm_struct *);

arch/parisc/kernel/process.c

···
 
 static inline unsigned long brk_rnd(void)
 {
-	/* 8MB for 32bit, 1GB for 64bit */
-	if (is_32bit_task())
-		return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
-	else
-		return (get_random_int() & 0x3ffffUL) << PAGE_SHIFT;
+	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
 }
 
 unsigned long arch_randomize_brk(struct mm_struct *mm)

arch/parisc/kernel/sys_parisc.c

···
 {
 	unsigned long rnd = 0;
 
-	/*
-	*  8 bits of randomness in 32bit mmaps, 20 address space bits
-	* 28 bits of randomness in 64bit mmaps, 40 address space bits
-	*/
-	if (current->flags & PF_RANDOMIZE) {
-		if (is_32bit_task())
-			rnd = get_random_int() % (1<<8);
-		else
-			rnd = get_random_int() % (1<<28);
-	}
+	if (current->flags & PF_RANDOMIZE)
+		rnd = get_random_int() & MMAP_RND_MASK;
+
 	return rnd << PAGE_SHIFT;
+}
+
+unsigned long arch_mmap_rnd(void)
+{
+	return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
 }
 
 static unsigned long mmap_legacy_base(void)