Merge branch 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/li…

…nux/kernel/git/tip/tip

Pull x86 kernel address space randomization support from Peter Anvin:
 "This enables kernel address space randomization for x86"

* 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, kaslr: Clarify RANDOMIZE_BASE_MAX_OFFSET
  x86, kaslr: Remove unused including <linux/version.h>
  x86, kaslr: Use char array to gain sizeof sanity
  x86, kaslr: Add a circular multiply for better bit diffusion
  x86, kaslr: Mix entropy sources together as needed
  x86/relocs: Add percpu fixup for GNU ld 2.23
  x86, boot: Rename get_flags() and check_flags() to *_cpuflags()
  x86, kaslr: Raise the maximum virtual address to -1 GiB on x86_64
  x86, kaslr: Report kernel offset on panic
  x86, kaslr: Select random position from e820 maps
  x86, kaslr: Provide randomness functions
  x86, kaslr: Return location from decompress_kernel
  x86, boot: Move CPU flags out of cpucheck
  x86, relocs: Add more per-cpu gold special cases

Documentation/kernel-parameters.txt

@@ -2017,6 +2017,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	noapic		[SMP,APIC] Tells the kernel to not make use of any
 			IOAPICs that may be present in the system.
 
+	nokaslr		[X86]
+			Disable kernel base offset ASLR (Address Space
+			Layout Randomization) if built into the kernel.
+
 	noautogroup	Disable scheduler automatic task group creation.
 
 	nobats		[PPC] Do not use BATs for mapping kernel lowmem

arch/x86/Kconfig

@@ -1693,16 +1693,67 @@ config RELOCATABLE
 
 	  Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
 	  it has been loaded at and the compile time physical address
-	  (CONFIG_PHYSICAL_START) is ignored.
+	  (CONFIG_PHYSICAL_START) is used as the minimum location.
 
-# Relocation on x86-32 needs some additional build support
+config RANDOMIZE_BASE
+	bool "Randomize the address of the kernel image"
+	depends on RELOCATABLE
+	depends on !HIBERNATION
+	default n
+	---help---
+	   Randomizes the physical and virtual address at which the
+	   kernel image is decompressed, as a security feature that
+	   deters exploit attempts relying on knowledge of the location
+	   of kernel internals.
+
+	   Entropy is generated using the RDRAND instruction if it is
+	   supported. If RDTSC is supported, it is used as well. If
+	   neither RDRAND nor RDTSC are supported, then randomness is
+	   read from the i8254 timer.
+
+	   The kernel will be offset by up to RANDOMIZE_BASE_MAX_OFFSET,
+	   and aligned according to PHYSICAL_ALIGN. Since the kernel is
+	   built using 2GiB addressing, and PHYSICAL_ALGIN must be at a
+	   minimum of 2MiB, only 10 bits of entropy is theoretically
+	   possible. At best, due to page table layouts, 64-bit can use
+	   9 bits of entropy and 32-bit uses 8 bits.
+
+	   If unsure, say N.
+
+config RANDOMIZE_BASE_MAX_OFFSET
+	hex "Maximum kASLR offset allowed" if EXPERT
+	depends on RANDOMIZE_BASE
+	range 0x0 0x20000000 if X86_32
+	default "0x20000000" if X86_32
+	range 0x0 0x40000000 if X86_64
+	default "0x40000000" if X86_64
+	---help---
+	  The lesser of RANDOMIZE_BASE_MAX_OFFSET and available physical
+	  memory is used to determine the maximal offset in bytes that will
+	  be applied to the kernel when kernel Address Space Layout
+	  Randomization (kASLR) is active. This must be a multiple of
+	  PHYSICAL_ALIGN.
+
+	  On 32-bit this is limited to 512MiB by page table layouts. The
+	  default is 512MiB.
+
+	  On 64-bit this is limited by how the kernel fixmap page table is
+	  positioned, so this cannot be larger than 1GiB currently. Without
+	  RANDOMIZE_BASE, there is a 512MiB to 1.5GiB split between kernel
+	  and modules. When RANDOMIZE_BASE_MAX_OFFSET is above 512MiB, the
+	  modules area will shrink to compensate, up to the current maximum
+	  1GiB to 1GiB split. The default is 1GiB.
+
+	  If unsure, leave at the default value.
+
+# Relocation on x86 needs some additional build support
 config X86_NEED_RELOCS
 	def_bool y
-	depends on X86_32 && RELOCATABLE
+	depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
 
 config PHYSICAL_ALIGN
 	hex "Alignment value to which kernel should be aligned"
-	default "0x1000000"
+	default "0x200000"
 	range 0x2000 0x1000000 if X86_32
 	range 0x200000 0x1000000 if X86_64
 	---help---

arch/x86/boot/Makefile

@@ -20,7 +20,7 @@ targets		:= vmlinux.bin setup.bin setup.elf bzImage
 targets		+= fdimage fdimage144 fdimage288 image.iso mtools.conf
 subdir-		:= compressed
 
-setup-y		+= a20.o bioscall.o cmdline.o copy.o cpu.o cpucheck.o
+setup-y		+= a20.o bioscall.o cmdline.o copy.o cpu.o cpuflags.o cpucheck.o
 setup-y		+= early_serial_console.o edd.o header.o main.o mca.o memory.o
 setup-y		+= pm.o pmjump.o printf.o regs.o string.o tty.o video.o
 setup-y		+= video-mode.o version.o

arch/x86/boot/boot.h

@@ -26,9 +26,8 @@
 #include <asm/boot.h>
 #include <asm/setup.h>
 #include "bitops.h"
-#include <asm/cpufeature.h>
-#include <asm/processor-flags.h>
 #include "ctype.h"
+#include "cpuflags.h"
 
 /* Useful macros */
 #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
@@ -307,14 +306,7 @@ static inline int cmdline_find_option_bool(const char *option)
 	return __cmdline_find_option_bool(cmd_line_ptr, option);
 }
 
-
 /* cpu.c, cpucheck.c */
-struct cpu_features {
-	int level;		/* Family, or 64 for x86-64 */
-	int model;
-	u32 flags[NCAPINTS];
-};
-extern struct cpu_features cpu;
 int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr);
 int validate_cpu(void);
 

arch/x86/boot/compressed/Makefile

@@ -28,7 +28,7 @@ HOST_EXTRACFLAGS += -I$(srctree)/tools/include
 
 VMLINUX_OBJS = $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
 	$(obj)/string.o $(obj)/cmdline.o $(obj)/early_serial_console.o \
-	$(obj)/piggy.o
+	$(obj)/piggy.o $(obj)/cpuflags.o $(obj)/aslr.o
 
 $(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone