fs: binfmt_elf: create Kconfig variable for PIE randomization

Randomization of PIE load address is hard coded in binfmt_elf.c for X86
and ARM.  Create a new Kconfig variable
(CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE) for this and use it instead.  Thus
architecture specific policy is pushed out of the generic binfmt_elf.c and
into the architecture Kconfig files.

X86 and ARM Kconfigs are modified to select the new variable so there is
no change in behavior.  A follow on patch will select it for MIPS too.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 6 insertions, 1 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 9d66dfc33a5a..98a6459cd398 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -16,6 +16,7 @@ config ARM
         select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL)
         select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL)
         select HAVE_FUNCTION_GRAPH_TRACER if (!THUMB2_KERNEL)
+        select ARCH_BINFMT_ELF_RANDOMIZE_PIE
         select HAVE_GENERIC_DMA_COHERENT
         select HAVE_KERNEL_GZIP
         select HAVE_KERNEL_LZO
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1d2a69dd36d8..d6ddc0bfe36a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -62,6 +62,7 @@ config X86
         select ANON_INODES
         select HAVE_ARCH_KMEMCHECK
         select HAVE_USER_RETURN_NOTIFIER
+        select ARCH_BINFMT_ELF_RANDOMIZE_PIE
         select HAVE_ARCH_JUMP_LABEL
         select HAVE_TEXT_POKE_SMP
         select HAVE_GENERIC_HARDIRQS
diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index 79e2ca7973b7..e95d1b64082c 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -27,6 +27,9 @@ config COMPAT_BINFMT_ELF
         bool
         depends on COMPAT && BINFMT_ELF
 
+config ARCH_BINFMT_ELF_RANDOMIZE_PIE
+        bool
+
 config BINFMT_ELF_FDPIC
         bool "Kernel support for FDPIC ELF binaries"
         default y
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 21ac5ee4b43f..bcb884e2d613 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -794,7 +794,7 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
                          * default mmap base, as well as whatever program they
                          * might try to exec.  This is because the brk will
                          * follow the loader, and is not movable.  */
-#if defined(CONFIG_X86) || defined(CONFIG_ARM)
+#ifdef CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE
                         /* Memory randomization might have been switched off
                          * in runtime via sysctl.
                          * If that is the case, retain the original non-zero