parisc: Use generic mmap top-down layout and brk randomization

parisc uses a top-down layout by default that exactly fits the generic
functions, so get rid of arch specific code and use the generic version
by selecting ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT.

Note that on parisc the stack always grows up and a "unlimited stack"
simply means that the value as defined in CONFIG_STACK_MAX_DEFAULT_SIZE_MB
should be used. So RLIM_INFINITY is not an indicator to use the legacy
memory layout.
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/Kconfig

@@ -49,6 +49,9 @@ config PARISC
 	select TTY # Needed for pdc_cons.c
 	select HAS_IOPORT if PCI || EISA
 	select HAVE_DEBUG_STACKOVERFLOW
+	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
+	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
+	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_HASH
 	select HAVE_ARCH_JUMP_LABEL
@@ -124,6 +127,20 @@ config TIME_LOW_RES
 	depends on SMP
 	default y
 
+config ARCH_MMAP_RND_BITS_MIN
+	default 18 if 64BIT
+	default 8
+
+config ARCH_MMAP_RND_COMPAT_BITS_MIN
+	default 8
+
+config ARCH_MMAP_RND_BITS_MAX
+	default 24 if 64BIT
+	default 17
+
+config ARCH_MMAP_RND_COMPAT_BITS_MAX
+	default 17
+
 # unless you want to implement ACPI on PA-RISC ... ;-)
 config PM
 	bool

arch/parisc/kernel/process.c

@@ -278,17 +278,3 @@ __get_wchan(struct task_struct *p)
 	} while (count++ < MAX_UNWIND_ENTRIES);
 	return 0;
 }
-
-static inline unsigned long brk_rnd(void)
-{
-	return (get_random_u32() & BRK_RND_MASK) << PAGE_SHIFT;
-}
-
-unsigned long arch_randomize_brk(struct mm_struct *mm)
-{
-	unsigned long ret = PAGE_ALIGN(mm->brk + brk_rnd());
-
-	if (ret < mm->brk)
-		return mm->brk;
-	return ret;
-}

arch/parisc/kernel/sys_parisc.c

@@ -161,7 +161,7 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
 	}
 
 	info.flags = 0;
-	info.low_limit = mm->mmap_legacy_base;
+	info.low_limit = mm->mmap_base;
 	info.high_limit = mmap_upper_limit(NULL);
 	return vm_unmapped_area(&info);
 }
@@ -181,58 +181,6 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 			addr, len, pgoff, flags, DOWN);
 }
 
-static int mmap_is_legacy(void)
-{
-	if (current->personality & ADDR_COMPAT_LAYOUT)
-		return 1;
-
-	/* parisc stack always grows up - so a unlimited stack should
-	 * not be an indicator to use the legacy memory layout.
-	 * if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
-	 *	return 1;
-	 */
-
-	return sysctl_legacy_va_layout;
-}
-
-static unsigned long mmap_rnd(void)
-{
-	unsigned long rnd = 0;
-
-	if (current->flags & PF_RANDOMIZE)
-		rnd = get_random_u32() & MMAP_RND_MASK;
-
-	return rnd << PAGE_SHIFT;
-}
-
-unsigned long arch_mmap_rnd(void)
-{
-	return (get_random_u32() & MMAP_RND_MASK) << PAGE_SHIFT;
-}
-
-static unsigned long mmap_legacy_base(void)
-{
-	return TASK_UNMAPPED_BASE + mmap_rnd();
-}
-
-/*
- * This function, called very early during the creation of a new
- * process VM image, sets up which VM layout function to use:
- */
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
-{
-	mm->mmap_legacy_base = mmap_legacy_base();
-	mm->mmap_base = mmap_upper_limit(rlim_stack);
-
-	if (mmap_is_legacy()) {
-		mm->mmap_base = mm->mmap_legacy_base;
-		mm->get_unmapped_area = arch_get_unmapped_area;
-	} else {
-		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
-	}
-}
-
-
 asmlinkage unsigned long sys_mmap2(unsigned long addr, unsigned long len,
 	unsigned long prot, unsigned long flags, unsigned long fd,
 	unsigned long pgoff)

mm/util.c

@@ -396,7 +396,10 @@ static int mmap_is_legacy(struct rlimit *rlim_stack)
 	if (current->personality & ADDR_COMPAT_LAYOUT)
 		return 1;
 
-	if (rlim_stack->rlim_cur == RLIM_INFINITY)
+	/* On parisc the stack always grows up - so a unlimited stack should
+	 * not be an indicator to use the legacy memory layout. */
+	if (rlim_stack->rlim_cur == RLIM_INFINITY &&
+		!IS_ENABLED(CONFIG_STACK_GROWSUP))
 		return 1;
 
 	return sysctl_legacy_va_layout;