[PATCH] flexible-mmap for ppc64

From: <arjanv@redhat.com>

Implement the new address space layout for 32-bit apps running on ppc64.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ppc64/mm/Makefile

@@ -5,6 +5,6 @@
 EXTRA_CFLAGS += -mno-minimal-toc
 
 obj-y := fault.o init.o imalloc.o hash_utils.o hash_low.o tlb.o \
-	slb_low.o slb.o stab.o
+	slb_low.o slb.o stab.o mmap.o
 obj-$(CONFIG_DISCONTIGMEM) += numa.o
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o

arch/ppc64/mm/mmap.c

+/*
+ *  linux/arch/ppc64/mm/mmap.c
+ *
+ *  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>
+
+/*
+ * 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(void)
+{
+	unsigned long gap = current->rlim[RLIMIT_STACK].rlim_cur;
+
+	if (gap < MIN_GAP)
+		gap = MIN_GAP;
+	else if (gap > MAX_GAP)
+		gap = MAX_GAP;
+
+	return TASK_SIZE - (gap & PAGE_MASK);
+}
+
+static inline int mmap_is_legacy(void)
+{
+	/*
+	 * Force standard allocation for 64 bit programs.
+	 */
+	if (!test_thread_flag(TIF_32BIT))
+		return 1;
+
+	if (current->personality & ADDR_COMPAT_LAYOUT)
+		return 1;
+
+	if (current->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
+		return 1;
+
+	return sysctl_legacy_va_layout;
+}
+
+/*
+ * 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;
+	}
+}

include/asm-ppc64/processor.h

@@ -628,6 +628,8 @@ static inline void prefetchw(const void *x)
 
 #endif /* ASSEMBLY */
 
+#define HAVE_ARCH_PICK_MMAP_LAYOUT
+
 /*
  * Number of entries in the SLB. If this ever changes we should handle
  * it with a use a cpu feature fixup.