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: Thomas Gleixner <[e-mail]>
Cc: Baoquan He <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Yinghai Lu <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: "H. Peter Anvin" <[e-mail]>
Cc: [e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/Kconfig

···
 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
···
 	  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
···
 	   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

···
 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

···
 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