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@xxxxxxxxxxxxxxxxxx>
---
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
