powerpc/mm: Make mmap_64.c compile on 32bit powerpc

There appears to be no good reason to keep this as 64bit only. It works
on 32bit also, and has checks so that it can work correctly with 32bit
binaries on 64bit hardware which is why I think this works.

I tested this on qemu using the virtex-ml507 machine type.

Before,

/bin2 # ./test & cat /proc/${!}/maps
00100000-00103000 r-xp 00000000 00:00 0          [vdso]
10000000-10007000 r-xp 00000000 00:01 454        /bin2/test
10017000-10018000 rw-p 00007000 00:01 454        /bin2/test
48000000-48020000 r-xp 00000000 00:01 224        /lib/ld-2.11.3.so
48021000-48023000 rw-p 00021000 00:01 224        /lib/ld-2.11.3.so
bfd03000-bfd24000 rw-p 00000000 00:00 0          [stack]
/bin2 # ./test & cat /proc/${!}/maps
00100000-00103000 r-xp 00000000 00:00 0          [vdso]
0fe6e000-0ffd8000 r-xp 00000000 00:01 214        /lib/libc-2.11.3.so
0ffd8000-0ffe8000 ---p 0016a000 00:01 214        /lib/libc-2.11.3.so
0ffe8000-0ffed000 rw-p 0016a000 00:01 214        /lib/libc-2.11.3.so
0ffed000-0fff0000 rw-p 00000000 00:00 0
10000000-10007000 r-xp 00000000 00:01 454        /bin2/test
10017000-10018000 rw-p 00007000 00:01 454        /bin2/test
48000000-48020000 r-xp 00000000 00:01 224        /lib/ld-2.11.3.so
48020000-48021000 rw-p 00000000 00:00 0
48021000-48023000 rw-p 00021000 00:01 224        /lib/ld-2.11.3.so
bf98a000-bf9ab000 rw-p 00000000 00:00 0          [stack]
/bin2 # ./test & cat /proc/${!}/maps
00100000-00103000 r-xp 00000000 00:00 0          [vdso]
0fe6e000-0ffd8000 r-xp 00000000 00:01 214        /lib/libc-2.11.3.so
0ffd8000-0ffe8000 ---p 0016a000 00:01 214        /lib/libc-2.11.3.so
0ffe8000-0ffed000 rw-p 0016a000 00:01 214        /lib/libc-2.11.3.so
0ffed000-0fff0000 rw-p 00000000 00:00 0
10000000-10007000 r-xp 00000000 00:01 454        /bin2/test
10017000-10018000 rw-p 00007000 00:01 454        /bin2/test
48000000-48020000 r-xp 00000000 00:01 224        /lib/ld-2.11.3.so
48020000-48021000 rw-p 00000000 00:00 0
48021000-48023000 rw-p 00021000 00:01 224        /lib/ld-2.11.3.so
bfa54000-bfa75000 rw-p 00000000 00:00 0          [stack]

After,

bash-4.1# ./test & cat /proc/${!}/maps
[7] 803
00100000-00103000 r-xp 00000000 00:00 0          [vdso]
10000000-10007000 r-xp 00000000 00:01 454        /bin2/test
10017000-10018000 rw-p 00007000 00:01 454        /bin2/test
b7eb0000-b7ed0000 r-xp 00000000 00:01 224        /lib/ld-2.11.3.so
b7ed1000-b7ed3000 rw-p 00021000 00:01 224        /lib/ld-2.11.3.so
bfbc0000-bfbe1000 rw-p 00000000 00:00 0          [stack]
bash-4.1# ./test & cat /proc/${!}/maps
[8] 805
00100000-00103000 r-xp 00000000 00:00 0          [vdso]
10000000-10007000 r-xp 00000000 00:01 454        /bin2/test
10017000-10018000 rw-p 00007000 00:01 454        /bin2/test
b7b03000-b7b23000 r-xp 00000000 00:01 224        /lib/ld-2.11.3.so
b7b24000-b7b26000 rw-p 00021000 00:01 224        /lib/ld-2.11.3.so
bfc27000-bfc48000 rw-p 00000000 00:00 0          [stack]
bash-4.1# ./test & cat /proc/${!}/maps
[9] 807
00100000-00103000 r-xp 00000000 00:00 0          [vdso]
10000000-10007000 r-xp 00000000 00:01 454        /bin2/test
10017000-10018000 rw-p 00007000 00:01 454        /bin2/test
b7f37000-b7f57000 r-xp 00000000 00:01 224        /lib/ld-2.11.3.so
b7f58000-b7f5a000 rw-p 00021000 00:01 224        /lib/ld-2.11.3.so
bff96000-bffb7000 rw-p 00000000 00:00 0          [stack]

Signed-off-by: Daniel Walker <dwalker@fifo90.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 101 insertions, 0 deletions

diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
new file mode 100644
index 000000000000..67a42ed0d2fc
--- /dev/null
+++ b/arch/powerpc/mm/mmap.c
@@ -0,0 +1,101 @@
+/*
+ *  flexible mmap layout support
+ *
+ * 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>
+#include <linux/sched.h>
+
+/*
+ * Top of mmap area (just below the process stack).
+ *
+ * Leave at least a ~128 MB hole on 32bit applications.
+ *
+ * On 64bit applications we randomise the stack by 1GB so we need to
+ * space our mmap start address by a further 1GB, otherwise there is a
+ * chance the mmap area will end up closer to the stack than our ulimit
+ * requires.
+ */
+#define MIN_GAP32 (128*1024*1024)
+#define MIN_GAP64 ((128 + 1024)*1024*1024UL)
+#define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64)
+#define MAX_GAP (TASK_SIZE/6*5)
+
+static inline 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;
+}
+
+static unsigned long mmap_rnd(void)
+{
+	unsigned long rnd = 0;
+
+	if (current->flags & PF_RANDOMIZE) {
+		/* 8MB for 32bit, 1GB for 64bit */
+		if (is_32bit_task())
+			rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
+		else
+			rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
+	}
+	return rnd << PAGE_SHIFT;
+}
+
+static inline unsigned long mmap_base(void)
+{
+	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 - 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)
+{
+	/*
+	 * Fall back to the standard layout if the personality
+	 * bit is set, or if the expected stack growth is unlimited:
+	 */
+	if (mmap_is_legacy()) {
+		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->get_unmapped_area = arch_get_unmapped_area_topdown;
+		mm->unmap_area = arch_unmap_area_topdown;
+	}
+}