[PATCH] x86_64: Flexmap for 32bit and randomized mappings for 64bit

Another try at this.

For 32bit follow the 32bit implementation from Ingo -
mappings are growing down from the end of stack now
and vary randomly by 1GB.

Randomized mappings for 64bit just vary the normal mmap break
by 1TB. I didn't bother implementing full flex mmap for 64bit
because it shouldn't be needed there.

Cc: mingo@elte.hu
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/x86_64/ia32/Makefile

@@ -3,7 +3,8 @@
 #
 
 obj-$(CONFIG_IA32_EMULATION) := ia32entry.o sys_ia32.o ia32_signal.o tls32.o \
-	ia32_binfmt.o fpu32.o ptrace32.o syscall32.o syscall32_syscall.o
+	ia32_binfmt.o fpu32.o ptrace32.o syscall32.o syscall32_syscall.o \
+	mmap32.o
 
 sysv-$(CONFIG_SYSVIPC) := ipc32.o
 obj-$(CONFIG_IA32_EMULATION) += $(sysv-y)

arch/x86_64/ia32/mmap32.c

+/*
+ *  linux/arch/x86_64/ia32/mm/mmap.c
+ *
+ *  flexible mmap layout support
+ *
+ * Based on the i386 version which was
+ *
+ * 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>
+
+/*
+ * 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 = current->signal->rlim[RLIMIT_STACK].rlim_cur;
+	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 ia32_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 (sysctl_legacy_va_layout ||
+			(current->personality & ADDR_COMPAT_LAYOUT) ||
+			current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY) {
+		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);
+		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+		mm->unmap_area = arch_unmap_area_topdown;
+	}
+}

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_NUMA) += numa.o
 obj-$(CONFIG_K8_NUMA) += k8topology.o

arch/x86_64/mm/mmap.c

+/* Copyright 2005 Andi Kleen, SuSE Labs.
+ * Licensed under GPL, v.2
+ */
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/random.h>
+#include <asm/ia32.h>
+
+/* Notebook: move the mmap code from sys_x86_64.c over here. */
+
+void arch_pick_mmap_layout(struct mm_struct *mm)
+{
+#ifdef CONFIG_IA32_EMULATION
+	if (current_thread_info()->flags & _TIF_IA32)
+		return ia32_pick_mmap_layout(mm);
+#endif
+	mm->mmap_base = TASK_UNMAPPED_BASE;
+	if (current->flags & PF_RANDOMIZE) {
+		/* Add 28bit randomness which is about 40bits of address space
+		   because mmap base has to be page aligned.
+ 		   or ~1/128 of the total user VM
+	   	   (total user address space is 47bits) */
+		unsigned rnd = get_random_int() & 0xfffffff;
+		mm->mmap_base += ((unsigned long)rnd) << PAGE_SHIFT;
+	}
+	mm->get_unmapped_area = arch_get_unmapped_area;
+	mm->unmap_area = arch_unmap_area;
+}
+

include/asm-x86_64/ia32.h

@@ -169,6 +169,8 @@ int ia32_child_tls(struct task_struct *p, struct pt_regs *childregs);
 struct linux_binprm;
 extern int ia32_setup_arg_pages(struct linux_binprm *bprm,
 				unsigned long stack_top, int exec_stack);
+struct mm_struct;
+extern void ia32_pick_mmap_layout(struct mm_struct *mm);
 
 #endif
 

include/asm-x86_64/processor.h

@@ -477,4 +477,6 @@ extern unsigned long boot_option_idle_override;
 /* Boot loader type from the setup header */
 extern int bootloader_type;
 
+#define HAVE_ARCH_PICK_MMAP_LAYOUT 1
+
 #endif /* __ASM_X86_64_PROCESSOR_H */