x86: Enable KASLR by default

KASLR is mature (and important) enough to be enabled by default on x86.

Also enable it by default in the defconfigs.
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: dan.j.williams@intel.com
Cc: dave.jiang@intel.com
Cc: dyoung@redhat.com
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

arch/x86/Kconfig

@@ -1966,7 +1966,7 @@ config RELOCATABLE
 config RANDOMIZE_BASE
 	bool "Randomize the address of the kernel image (KASLR)"
 	depends on RELOCATABLE
-	default n
+	default y
 	---help---
 	  In support of Kernel Address Space Layout Randomization (KASLR),
 	  this randomizes the physical address at which the kernel image
@@ -1996,7 +1996,7 @@ config RANDOMIZE_BASE
 	  theoretically possible, but the implementations are further
 	  limited due to memory layouts.
 
-	  If unsure, say N.
+	  If unsure, say Y.
 
 # Relocation on x86 needs some additional build support
 config X86_NEED_RELOCS
@@ -2045,7 +2045,7 @@ config RANDOMIZE_MEMORY
 	   configuration have in average 30,000 different possible virtual
 	   addresses for each memory section.
 
-	   If unsure, say N.
+	   If unsure, say Y.
 
 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
 	hex "Physical memory mapping padding" if EXPERT

arch/x86/configs/i386_defconfig

@@ -57,6 +57,8 @@ CONFIG_EFI=y
 CONFIG_HZ_1000=y
 CONFIG_KEXEC=y
 CONFIG_CRASH_DUMP=y
+CONFIG_RANDOMIZE_BASE=y
+CONFIG_RANDOMIZE_MEMORY=y
 # CONFIG_COMPAT_VDSO is not set
 CONFIG_HIBERNATION=y
 CONFIG_PM_DEBUG=y

arch/x86/configs/x86_64_defconfig

@@ -55,6 +55,8 @@ CONFIG_EFI=y
 CONFIG_HZ_1000=y
 CONFIG_KEXEC=y
 CONFIG_CRASH_DUMP=y
+CONFIG_RANDOMIZE_BASE=y
+CONFIG_RANDOMIZE_MEMORY=y
 # CONFIG_COMPAT_VDSO is not set
 CONFIG_HIBERNATION=y
 CONFIG_PM_DEBUG=y