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[PATCH 2/2] MIPS: Enable heap randomization.

To: linux-mips@linux-mips.org, ralf@linux-mips.org
Subject: [PATCH 2/2] MIPS: Enable heap randomization.
From: David Daney <ddaney@caviumnetworks.com>
Date: Mon, 19 Jul 2010 13:14:57 -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
Based somewhat on the PPC implementation.

32-bit processes have the heap randomized in an 8MB space, 256MB for
64-bit processes.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
---
 arch/mips/include/asm/elf.h |    5 +++++
 arch/mips/kernel/syscall.c  |   28 ++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index ea77a42..fd1d39e 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -372,4 +372,9 @@ extern const char *__elf_platform;
 struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
                                       int uses_interp);
+
+struct mm_struct;
+extern unsigned long arch_randomize_brk(struct mm_struct *mm);
+#define arch_randomize_brk arch_randomize_brk
+
 #endif /* _ASM_ELF_H */
diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index 9824a82..58bab2e 100644
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -30,6 +30,7 @@
 #include <linux/uaccess.h>
 #include <linux/slab.h>
 #include <linux/random.h>
+#include <linux/elf.h>
 
 #include <asm/asm.h>
 #include <asm/branch.h>
@@ -153,6 +154,33 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
        mm->unmap_area = arch_unmap_area;
 }
 
+static inline unsigned long brk_rnd(void)
+{
+       unsigned long rnd = get_random_int();
+
+       rnd = rnd << PAGE_SHIFT;
+       /* 8MB for 32bit, 256MB for 64bit */
+       if (TASK_IS_32BIT_ADDR)
+               rnd = rnd & 0x7ffffful;
+       else
+               rnd = rnd & 0xffffffful;
+
+       return rnd;
+}
+
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+       unsigned long base = mm->brk;
+       unsigned long ret;
+
+       ret = PAGE_ALIGN(base + brk_rnd());
+
+       if (ret < mm->brk)
+               return mm->brk;
+
+       return ret;
+}
+
 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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