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-rw-r--r--arch/tile/mm/mmap.c93
1 files changed, 93 insertions, 0 deletions
diff --git a/arch/tile/mm/mmap.c b/arch/tile/mm/mmap.c
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+++ b/arch/tile/mm/mmap.c
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+/*
+ * Copyright 2010 Tilera Corporation. 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, version 2.
+ *
+ * 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, GOOD TITLE or
+ * NON INFRINGEMENT. See the GNU General Public License for
+ * more details.
+ *
+ * Taken from the i386 architecture and simplified.
+ */
+
+#include <linux/mm.h>
+#include <linux/random.h>
+#include <linux/limits.h>
+#include <linux/sched.h>
+#include <linux/mman.h>
+#include <linux/compat.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 = rlimit(RLIMIT_STACK);
+ 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 arch_pick_mmap_layout(struct mm_struct *mm)
+{
+#if !defined(__tilegx__)
+ int is_32bit = 1;
+#elif defined(CONFIG_COMPAT)
+ int is_32bit = is_compat_task();
+#else
+ int is_32bit = 0;
+#endif
+ unsigned long random_factor = 0UL;
+
+ /*
+ * 8 bits of randomness in 32bit mmaps, 24 address space bits
+ * 12 bits of randomness in 64bit mmaps, 28 address space bits
+ */
+ if (current->flags & PF_RANDOMIZE) {
+ if (is_32bit)
+ random_factor = get_random_int() % (1<<8);
+ else
+ random_factor = get_random_int() % (1<<12);
+
+ random_factor <<= PAGE_SHIFT;
+ }
+
+ /*
+ * Use standard layout if the expected stack growth is unlimited
+ * or we are running native 64 bits.
+ */
+ if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) {
+ mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
+ mm->get_unmapped_area = arch_get_unmapped_area;
+ } else {
+ mm->mmap_base = mmap_base(mm);
+ mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+ }
+}
+
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+ unsigned long range_end = mm->brk + 0x02000000;
+ return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
+}