[PATCH] x86_64: Flexmap for 32bit and randomized mappings for 64bit

Another try at this.

For 32bit follow the 32bit implementation from Ingo -
mappings are growing down from the end of stack now
and vary randomly by 1GB.

Randomized mappings for 64bit just vary the normal mmap break
by 1TB. I didn't bother implementing full flex mmap for 64bit
because it shouldn't be needed there.

Cc: mingo@elte.hu

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 78 insertions, 0 deletions

diff --git a/arch/x86_64/ia32/mmap32.c b/arch/x86_64/ia32/mmap32.c
new file mode 100644
index 000000000000..079f4132575c
--- /dev/null
+++ b/arch/x86_64/ia32/mmap32.c
@@ -0,0 +1,78 @@
+/*
+ *  linux/arch/x86_64/ia32/mm/mmap.c
+ *
+ *  flexible mmap layout support
+ *
+ * Based on the i386 version which was
+ *
+ * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *
+ * Started by Ingo Molnar <mingo@elte.hu>
+ */
+
+#include <linux/personality.h>
+#include <linux/mm.h>
+#include <linux/random.h>
+
+/*
+ * Top of mmap area (just below the process stack).
+ *
+ * Leave an at least ~128 MB hole.
+ */
+#define MIN_GAP (128*1024*1024)
+#define MAX_GAP (TASK_SIZE/6*5)
+
+static inline unsigned long mmap_base(struct mm_struct *mm)
+{
+        unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
+        unsigned long random_factor = 0;
+
+        if (current->flags & PF_RANDOMIZE)
+                random_factor = get_random_int() % (1024*1024);
+
+        if (gap < MIN_GAP)
+                gap = MIN_GAP;
+        else if (gap > MAX_GAP)
+                gap = MAX_GAP;
+
+        return PAGE_ALIGN(TASK_SIZE - gap - random_factor);
+}
+
+/*
+ * This function, called very early during the creation of a new
+ * process VM image, sets up which VM layout function to use:
+ */
+void ia32_pick_mmap_layout(struct mm_struct *mm)
+{
+        /*
+         * Fall back to the standard layout if the personality
+         * bit is set, or if the expected stack growth is unlimited:
+         */
+        if (sysctl_legacy_va_layout ||
+                        (current->personality & ADDR_COMPAT_LAYOUT) ||
+                        current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY) {
+                mm->mmap_base = TASK_UNMAPPED_BASE;
+                mm->get_unmapped_area = arch_get_unmapped_area;
+                mm->unmap_area = arch_unmap_area;
+        } else {
+                mm->mmap_base = mmap_base(mm);
+                mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+                mm->unmap_area = arch_unmap_area_topdown;
+        }
+}