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[PATCH 1/2] MIPS: Randomize mmap if randomize_va_space is set

To: linux-mips@linux-mips.org, ralf@linux-mips.org
Subject: [PATCH 1/2] MIPS: Randomize mmap if randomize_va_space is set
From: David Daney <ddaney@caviumnetworks.com>
Date: Mon, 19 Jul 2010 13:14:56 -0700
Cc: David Daney <ddaney@caviumnetworks.com>
In-reply-to: <1279570497-11060-1-git-send-email-ddaney@caviumnetworks.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1279570497-11060-1-git-send-email-ddaney@caviumnetworks.com>
Sender: linux-mips-bounce@linux-mips.org
Fairly straight forward: For 32-bit address spaces randomize within a
16MB space, for 64-bit within a 256MB space.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
---
 arch/mips/include/asm/processor.h |   11 +++++++++++
 arch/mips/kernel/syscall.c        |   21 ++++++++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletions(-)

diff --git a/arch/mips/include/asm/processor.h 
b/arch/mips/include/asm/processor.h
index 5d33b72..24d91f8 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -34,6 +34,11 @@ extern void (*cpu_wait)(void);
 extern unsigned int vced_count, vcei_count;
 
 /*
+ * MIPS does have an arch_pick_mmap_layout()
+ */
+#define HAVE_ARCH_PICK_MMAP_LAYOUT 1
+
+/*
  * A special page (the vdso) is mapped into all processes at the very
  * top of the virtual memory space.
  */
@@ -52,6 +57,9 @@ extern unsigned int vced_count, vcei_count;
  * space during mmap's.
  */
 #define TASK_UNMAPPED_BASE     ((TASK_SIZE / 3) & ~(PAGE_SIZE))
+
+#define TASK_IS_32BIT_ADDR 1
+
 #endif
 
 #ifdef CONFIG_64BIT
@@ -77,6 +85,9 @@ extern unsigned int vced_count, vcei_count;
                PAGE_ALIGN(TASK_SIZE32 / 3) : PAGE_ALIGN(TASK_SIZE / 3))
 #define TASK_SIZE_OF(tsk)                                              \
        (test_tsk_thread_flag(tsk, TIF_32BIT_ADDR) ? TASK_SIZE32 : TASK_SIZE)
+
+#define TASK_IS_32BIT_ADDR test_thread_flag(TIF_32BIT_ADDR)
+
 #endif
 
 #ifdef __KERNEL__
diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index dd81b0f..9824a82 100644
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -29,6 +29,7 @@
 #include <linux/ipc.h>
 #include <linux/uaccess.h>
 #include <linux/slab.h>
+#include <linux/random.h>
 
 #include <asm/asm.h>
 #include <asm/branch.h>
@@ -116,7 +117,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, 
unsigned long addr,
                    (!vmm || addr + len <= vmm->vm_start))
                        return addr;
        }
-       addr = TASK_UNMAPPED_BASE;
+       addr = current->mm->mmap_base;
        if (do_color_align)
                addr = COLOUR_ALIGN(addr, pgoff);
        else
@@ -134,6 +135,24 @@ unsigned long arch_get_unmapped_area(struct file *filp, 
unsigned long addr,
        }
 }
 
+void arch_pick_mmap_layout(struct mm_struct *mm)
+{
+       unsigned long random_factor = 0UL;
+
+       if (current->flags & PF_RANDOMIZE) {
+               random_factor = get_random_int();
+               random_factor = random_factor << PAGE_SHIFT;
+               if (TASK_IS_32BIT_ADDR)
+                       random_factor &= 0xfffffful;
+               else
+                       random_factor &= 0xffffffful;
+       }
+
+       mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
+       mm->get_unmapped_area = arch_get_unmapped_area;
+       mm->unmap_area = arch_unmap_area;
+}
+
 SYSCALL_DEFINE6(mips_mmap, unsigned long, addr, unsigned long, len,
        unsigned long, prot, unsigned long, flags, unsigned long,
        fd, off_t, offset)
-- 
1.7.1.1


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