Merge branch 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc:
  Fix build of cpm_uart due to core changes
  powerpc/8xx: Fix regression introduced by cache coherency rewrite
  powerpc/4xx: Fix erroneous xmon warning on PowerPC 4xx
  powerpc/mm: Fix 40x and 8xx vs. _PAGE_SPECIAL
  powerpc: Cleanup linker script using new linker script macros.
  powerpc: Fix ibm,client-architecture-support printout
  powerpc: Increase NODES_SHIFT on 64bit from 4 to 8
  powerpc/perf_counter: Fix vdso detection
  powerpc: Move 64bit heap above 1TB on machines with 1TB segments
  powerpc: Change archdata dma_data to a union
  powerpc: Rename get_dma_direct_offset get_dma_offset
  powerpc/mm: Remove duplicated #include
  powerpc/book3e-64: Remove duplicated #include
  powerpc: Check for unsupported relocs when using CONFIG_RELOCATABLE
  powerpc/pmc: Don't access lppaca on Book3E
  powerpc: kmalloc failure ignored in vio_build_iommu_table()
  hvc_console: Provide (un)locked version for hvc_resize()

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;