[PATCH v4 08/10] s390: redefine randomize_et_dyn for ELF_ET_DYN_BASE

Kees Cook
2015-03-04T22:14:57Z

In preparation for moving ET_DYN randomization into the ELF loader (which
requires a static ELF_ET_DYN_BASE), this redefines s390's existing ET_DYN
randomization in a call to arch_mmap_rnd(). This refactoring results in
the same ET_DYN randomization on s390.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/s390/include/asm/elf.h | 8 +++++---
arch/s390/mm/mmap.c | 11 ++---------
2 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/arch/s390/include/asm/elf.h b/arch/s390/include/asm/elf.h
index c9df40b5c0ac..2e63de8aac7c 100644
--- a/arch/s390/include/asm/elf.h
+++ b/arch/s390/include/asm/elf.h
@@ -161,10 +161,12 @@ extern unsigned int vdso_enabled;
/* This is the location that an ET_DYN program is loaded if exec'ed. Typical
use of this is to invoke "./ld.so someprog" to test out a new version of
the loader. We need to make sure that it is out of the way of the program
- that it will "exec", and that there is sufficient room for the brk. */
-
+ that it will "exec", and that there is sufficient room for the brk. 64-bit
+ tasks are aligned to 4GB. */
extern unsigned long randomize_et_dyn(void);
-#define ELF_ET_DYN_BASE randomize_et_dyn()
+#define ELF_ET_DYN_BASE (randomize_et_dyn() + (is_32bit_task() ? \
+ (STACK_TOP / 3 * 2) : \
+ (STACK_TOP / 3 * 2) & ~((1UL << 32) - 1)))

/* This yields a mask that user programs can use to figure out what
instruction set this CPU supports. */
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index a94504d99c47..8c11536f972d 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -179,17 +179,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,

unsigned long randomize_et_dyn(void)
{
- unsigned long base;
-
- base = STACK_TOP / 3 * 2;
- if (!is_32bit_task())
- /* Align to 4GB */
- base &= ~((1UL << 32) - 1);
-
if (current->flags & PF_RANDOMIZE)
- base += arch_mmap_rnd();
+ return arch_mmap_rnd();

- return base;
+ return 0UL;
}

#ifndef CONFIG_64BIT
--
1.9.1