s390/vdso: map vdso above stack

In the current code vdso is mapped below the stack. This is
problematic when programs mapped to the top of the address space
are allocating a lot of memory, because the heap will clash with
the vdso. To avoid this map the vdso above the stack and move
STACK_TOP so that it all fits into three level paging.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index a3ab8cb..add764a 100644 (file)
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -95,9 +95,10 @@ unsigned long vdso_size(void);
                                        (_REGION3_SIZE >> 1) : (_REGION2_SIZE >> 1))
 #define TASK_SIZE_MAX          (-PAGE_SIZE)
 
-#define STACK_TOP              (test_thread_flag(TIF_31BIT) ? \
-                                       _REGION3_SIZE : _REGION2_SIZE)
-#define STACK_TOP_MAX          _REGION2_SIZE
+#define VDSO_BASE              (STACK_TOP + PAGE_SIZE)
+#define VDSO_LIMIT             (test_thread_flag(TIF_31BIT) ? _REGION3_SIZE : _REGION2_SIZE)
+#define STACK_TOP              (VDSO_LIMIT - vdso_size() - PAGE_SIZE)
+#define STACK_TOP_MAX          (_REGION2_SIZE - vdso_size() - PAGE_SIZE)
 
 #define HAVE_ARCH_PICK_MMAP_LAYOUT
 

diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index 22cb727..7ba84a8 100644 (file)
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -221,7 +221,7 @@ unsigned long vdso_size(void)
 
 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
-       return map_vdso(0, vdso_size());
+       return map_vdso(VDSO_BASE, vdso_size());
 }
 
 static struct page ** __init vdso_setup_pages(void *start, void *end)