Initial import

1 files changed, 135 insertions, 0 deletions

diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
new file mode 100644
index 000000000..844b06d67
--- /dev/null
+++ b/arch/x86/mm/mmap.c
@@ -0,0 +1,135 @@
+/*
+ * Flexible mmap layout support
+ *
+ * Based on code by Ingo Molnar and Andi Kleen, copyrighted
+ * as follows:
+ *
+ * Copyright 2003-2009 Red Hat Inc.
+ * All Rights Reserved.
+ * Copyright 2005 Andi Kleen, SUSE Labs.
+ * Copyright 2007 Jiri Kosina, SUSE Labs.
+ *
+ * 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
+ */
+
+#include <linux/personality.h>
+#include <linux/mm.h>
+#include <linux/random.h>
+#include <linux/limits.h>
+#include <linux/sched.h>
+#include <asm/elf.h>
+
+struct va_alignment __read_mostly va_align = {
+	.flags = -1,
+};
+
+static unsigned long stack_maxrandom_size(void)
+{
+	unsigned long max = 0;
+	if ((current->flags & PF_RANDOMIZE) &&
+		!(current->personality & ADDR_NO_RANDOMIZE)) {
+		max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT;
+	}
+
+	return max;
+}
+
+/*
+ * Top of mmap area (just below the process stack).
+ *
+ * Leave an at least ~128 MB hole with possible stack randomization.
+ */
+#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
+#define MAX_GAP (TASK_SIZE/6*5)
+
+static int mmap_is_legacy(void)
+{
+	if (current->personality & ADDR_COMPAT_LAYOUT)
+		return 1;
+
+	if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
+		return 1;
+
+	return sysctl_legacy_va_layout;
+}
+
+unsigned long arch_mmap_rnd(void)
+{
+	unsigned long rnd;
+
+	/*
+	 *  8 bits of randomness in 32bit mmaps, 20 address space bits
+	 * 28 bits of randomness in 64bit mmaps, 40 address space bits
+	 */
+	if (mmap_is_ia32())
+		rnd = (unsigned long)get_random_int() % (1<<8);
+	else
+		rnd = (unsigned long)get_random_int() % (1<<28);
+
+	return rnd << PAGE_SHIFT;
+}
+
+static unsigned long mmap_base(unsigned long rnd)
+{
+	unsigned long gap = rlimit(RLIMIT_STACK);
+
+	if (gap < MIN_GAP)
+		gap = MIN_GAP;
+	else if (gap > MAX_GAP)
+		gap = MAX_GAP;
+
+	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+}
+
+/*
+ * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
+ * does, but not when emulating X86_32
+ */
+static unsigned long mmap_legacy_base(unsigned long rnd)
+{
+	if (mmap_is_ia32())
+		return TASK_UNMAPPED_BASE;
+	else
+		return TASK_UNMAPPED_BASE + 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)
+{
+	unsigned long random_factor = 0UL;
+
+	if (current->flags & PF_RANDOMIZE)
+		random_factor = arch_mmap_rnd();
+
+	mm->mmap_legacy_base = mmap_legacy_base(random_factor);
+
+	if (mmap_is_legacy()) {
+		mm->mmap_base = mm->mmap_legacy_base;
+		mm->get_unmapped_area = arch_get_unmapped_area;
+	} else {
+		mm->mmap_base = mmap_base(random_factor);
+		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+	}
+}
+
+const char *arch_vma_name(struct vm_area_struct *vma)
+{
+	if (vma->vm_flags & VM_MPX)
+		return "[mpx]";
+	return NULL;
+}