1 files changed, 16 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 0a3216433051..1168c5f440ab 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1165,7 +1165,22 @@ static inline unsigned long brk_rnd(void)
 
 unsigned long arch_randomize_brk(struct mm_struct *mm)
 {
-        unsigned long ret = PAGE_ALIGN(mm->brk + brk_rnd());
+        unsigned long base = mm->brk;
+        unsigned long ret;
+
+#ifdef CONFIG_PPC64
+        /*
+         * If we are using 1TB segments and we are allowed to randomise
+         * the heap, we can put it above 1TB so it is backed by a 1TB
+         * segment. Otherwise the heap will be in the bottom 1TB
+         * which always uses 256MB segments and this may result in a
+         * performance penalty.
+         */
+        if (!is_32bit_task() && (mmu_highuser_ssize == MMU_SEGSIZE_1T))
+                base = max_t(unsigned long, mm->brk, 1UL << SID_SHIFT_1T);
+#endif
+
+        ret = PAGE_ALIGN(base + brk_rnd());
 
         if (ret < mm->brk)
                 return mm->brk;