tile: support ASLR fully

With this change, tile Linux now supports address-space layout
randomization for shared objects, stack, heap and vdso.

Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Tony Lu <zlu@tilera.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

2 files changed, 26 insertions, 2 deletions

diff --git a/arch/tile/include/asm/elf.h b/arch/tile/include/asm/elf.h
index 31d854f1b83b..e1da88e8aa9f 100644
--- a/arch/tile/include/asm/elf.h
+++ b/arch/tile/include/asm/elf.h
@@ -137,6 +137,10 @@ do { \
         NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_BASE); \
 } while (0)
 
+struct mm_struct;
+extern unsigned long arch_randomize_brk(struct mm_struct *mm);
+#define arch_randomize_brk arch_randomize_brk
+
 #ifdef CONFIG_COMPAT
 
 #define COMPAT_ELF_PLATFORM "tilegx-m32"
diff --git a/arch/tile/mm/mmap.c b/arch/tile/mm/mmap.c
index d67d91ebf63e..851a94e6ae58 100644
--- a/arch/tile/mm/mmap.c
+++ b/arch/tile/mm/mmap.c
@@ -58,16 +58,36 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 #else
         int is_32bit = 0;
 #endif
+        unsigned long random_factor = 0UL;
+
+        /*
+         *  8 bits of randomness in 32bit mmaps, 24 address space bits
+         * 12 bits of randomness in 64bit mmaps, 28 address space bits
+         */
+        if (current->flags & PF_RANDOMIZE) {
+                if (is_32bit)
+                        random_factor = get_random_int() % (1<<8);
+                else
+                        random_factor = get_random_int() % (1<<12);
+
+                random_factor <<= PAGE_SHIFT;
+        }
 
         /*
          * Use standard layout if the expected stack growth is unlimited
          * or we are running native 64 bits.
          */
-        if (!is_32bit || rlimit(RLIMIT_STACK) == RLIM_INFINITY) {
-                mm->mmap_base = TASK_UNMAPPED_BASE;
+        if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) {
+                mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
                 mm->get_unmapped_area = arch_get_unmapped_area;
         } else {
                 mm->mmap_base = mmap_base(mm);
                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
         }
 }
+
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+        unsigned long range_end = mm->brk + 0x02000000;
+        return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
+}