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-rw-r--r--arch/powerpc/kernel/process.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 0a321643305..1168c5f440a 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;