[PATCH] x86_64: flex mmap patch for x86-64

From: Arjan van de Ven <arjanv@redhat.com>

Do flex mmap for x86-64.  mmaps will grow down in the address space now
instead of up.

Patch has 2 parts; the generic strategy selection, and code to make a correct
TASK_SIZE .  the later may be fixed in your tree already in which case it's
redundant.  

Modified by AK to apply to 64bit processes too.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/mm/Makefile

@@ -2,7 +2,7 @@
 # Makefile for the linux x86_64-specific parts of the memory manager.
 #
 
-obj-y	 := init.o fault.o ioremap.o extable.o pageattr.o
+obj-y	 := init.o fault.o ioremap.o extable.o pageattr.o mmap.o
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
 obj-$(CONFIG_DISCONTIGMEM) += numa.o
 obj-$(CONFIG_K8_NUMA) += k8topology.o

arch/x86_64/mm/mmap.c

+/*
+ *  linux/arch/x86-64/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, 4GB for 64bit.
+ */
+#define MIN_GAP (test_thread_flag(TIF_IA32) ? 4UL*1024*1024*1024 : 128*1024*1024)
+#define MAX_GAP (TASK_SIZE/6*5)
+
+static inline unsigned long mmap_base(void)
+{
+	unsigned long gap = current->signal->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)
+{
+	if (current->personality & ADDR_COMPAT_LAYOUT)
+		return 1;
+
+	if (current->signal->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-x86_64/processor.h

@@ -164,10 +164,6 @@ static inline void clear_in_cr4 (unsigned long mask)
 #define MCA_bus__is_a_macro
 
 
-/*
- * User space process size: 512GB - 1GB (default).
- */
-#define TASK_SIZE	(0x0000007fc0000000UL)
 
 /* This decides where the kernel will search for a free chunk of vm
  * space during mmap's.
@@ -178,6 +174,14 @@ static inline void clear_in_cr4 (unsigned long mask)
 #define TASK_UNMAPPED_BASE	\
 	(test_thread_flag(TIF_IA32) ? TASK_UNMAPPED_32 : TASK_UNMAPPED_64)  
 
+
+/*
+ * User space process size: 512GB - 1GB (default).
+ */
+#define TASK_SIZE_64	(0x0000007fc0000000UL)
+
+#define TASK_SIZE (test_thread_flag(TIF_IA32) ? IA32_PAGE_OFFSET : TASK_SIZE_64)
+
 /*
  * Size of io_bitmap.
  */
@@ -461,4 +465,6 @@ static inline void __mwait(unsigned long eax, unsigned long ecx)
 
 #define cache_line_size() (boot_cpu_data.x86_cache_alignment)
 
+#define HAVE_ARCH_PICK_MMAP_LAYOUT
+
 #endif /* __ASM_X86_64_PROCESSOR_H */