[linux-2.6-block.git] / arch / x86 / boot / compressed / aslr.c

#include "misc.h"

#ifdef CONFIG_RANDOMIZE_BASE
#include <asm/msr.h>
#include <asm/archrandom.h>
#include <asm/e820.h>

#include <generated/compile.h>
#include <linux/module.h>
#include <linux/uts.h>
#include <linux/utsname.h>
#include <generated/utsrelease.h>

/* Simplified build-specific string for starting entropy. */
static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
		LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;

#define I8254_PORT_CONTROL	0x43
#define I8254_PORT_COUNTER0	0x40
#define I8254_CMD_READBACK	0xC0
#define I8254_SELECT_COUNTER0	0x02
#define I8254_STATUS_NOTREADY	0x40
static inline u16 i8254(void)
{
	u16 status, timer;

	do {
		outb(I8254_PORT_CONTROL,
		     I8254_CMD_READBACK | I8254_SELECT_COUNTER0);
		status = inb(I8254_PORT_COUNTER0);
		timer  = inb(I8254_PORT_COUNTER0);
		timer |= inb(I8254_PORT_COUNTER0) << 8;
	} while (status & I8254_STATUS_NOTREADY);

	return timer;
}

static unsigned long rotate_xor(unsigned long hash, const void *area,
				size_t size)
{
	size_t i;
	unsigned long *ptr = (unsigned long *)area;

	for (i = 0; i < size / sizeof(hash); i++) {
		/* Rotate by odd number of bits and XOR. */
		hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
		hash ^= ptr[i];
	}

	return hash;
}

/* Attempt to create a simple but unpredictable starting entropy. */
static unsigned long get_random_boot(void)
{
	unsigned long hash = 0;

	hash = rotate_xor(hash, build_str, sizeof(build_str));
	hash = rotate_xor(hash, real_mode, sizeof(*real_mode));

	return hash;
}

static unsigned long get_random_long(void)
{
#ifdef CONFIG_X86_64
	const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
#else
	const unsigned long mix_const = 0x3f39e593UL;
#endif
	unsigned long raw, random = get_random_boot();
	bool use_i8254 = true;

	debug_putstr("KASLR using");

	if (has_cpuflag(X86_FEATURE_RDRAND)) {
		debug_putstr(" RDRAND");
		if (rdrand_long(&raw)) {
			random ^= raw;
			use_i8254 = false;
		}
	}

	if (has_cpuflag(X86_FEATURE_TSC)) {
		debug_putstr(" RDTSC");
		rdtscll(raw);

		random ^= raw;
		use_i8254 = false;
	}

	if (use_i8254) {
		debug_putstr(" i8254");
		random ^= i8254();
	}

	/* Circular multiply for better bit diffusion */
	asm("mul %3"
	    : "=a" (random), "=d" (raw)
	    : "a" (random), "rm" (mix_const));
	random += raw;

	debug_putstr("...\n");

	return random;
}

struct mem_vector {
	unsigned long start;
	unsigned long size;
};

#define MEM_AVOID_MAX 5
static struct mem_vector mem_avoid[MEM_AVOID_MAX];

static bool mem_contains(struct mem_vector *region, struct mem_vector *item)
{
	/* Item at least partially before region. */
	if (item->start < region->start)
		return false;
	/* Item at least partially after region. */
	if (item->start + item->size > region->start + region->size)
		return false;
	return true;
}

static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
{
	/* Item one is entirely before item two. */
	if (one->start + one->size <= two->start)
		return false;
	/* Item one is entirely after item two. */
	if (one->start >= two->start + two->size)
		return false;
	return true;
}

static void mem_avoid_init(unsigned long input, unsigned long input_size,
			   unsigned long output, unsigned long output_size)
{
	u64 initrd_start, initrd_size;
	u64 cmd_line, cmd_line_size;
	unsigned long unsafe, unsafe_len;
	char *ptr;

	/*
	 * Avoid the region that is unsafe to overlap during
	 * decompression (see calculations at top of misc.c).
	 */
	unsafe_len = (output_size >> 12) + 32768 + 18;
	unsafe = (unsigned long)input + input_size - unsafe_len;
	mem_avoid[0].start = unsafe;
	mem_avoid[0].size = unsafe_len;

	/* Avoid initrd. */
	initrd_start  = (u64)real_mode->ext_ramdisk_image << 32;
	initrd_start |= real_mode->hdr.ramdisk_image;
	initrd_size  = (u64)real_mode->ext_ramdisk_size << 32;
	initrd_size |= real_mode->hdr.ramdisk_size;
	mem_avoid[1].start = initrd_start;
	mem_avoid[1].size = initrd_size;

	/* Avoid kernel command line. */
	cmd_line  = (u64)real_mode->ext_cmd_line_ptr << 32;
	cmd_line |= real_mode->hdr.cmd_line_ptr;
	/* Calculate size of cmd_line. */
	ptr = (char *)(unsigned long)cmd_line;
	for (cmd_line_size = 0; ptr[cmd_line_size++]; )
		;
	mem_avoid[2].start = cmd_line;
	mem_avoid[2].size = cmd_line_size;

	/* Avoid heap memory. */
	mem_avoid[3].start = (unsigned long)free_mem_ptr;
	mem_avoid[3].size = BOOT_HEAP_SIZE;

	/* Avoid stack memory. */
	mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
	mem_avoid[4].size = BOOT_STACK_SIZE;
}

/* Does this memory vector overlap a known avoided area? */
static bool mem_avoid_overlap(struct mem_vector *img)
{
	int i;

	for (i = 0; i < MEM_AVOID_MAX; i++) {
		if (mem_overlaps(img, &mem_avoid[i]))
			return true;
	}

	return false;
}

static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
			   CONFIG_PHYSICAL_ALIGN];
static unsigned long slot_max;

static void slots_append(unsigned long addr)
{
	/* Overflowing the slots list should be impossible. */
	if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
			CONFIG_PHYSICAL_ALIGN)
		return;

	slots[slot_max++] = addr;
}

static unsigned long slots_fetch_random(void)
{
	/* Handle case of no slots stored. */
	if (slot_max == 0)
		return 0;

	return slots[get_random_long() % slot_max];
}

static void process_e820_entry(struct e820entry *entry,
			       unsigned long minimum,
			       unsigned long image_size)
{
	struct mem_vector region, img;

	/* Skip non-RAM entries. */
	if (entry->type != E820_RAM)
		return;

	/* Ignore entries entirely above our maximum. */
	if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
		return;

	/* Ignore entries entirely below our minimum. */
	if (entry->addr + entry->size < minimum)
		return;

	region.start = entry->addr;
	region.size = entry->size;

	/* Potentially raise address to minimum location. */
	if (region.start < minimum)
		region.start = minimum;

	/* Potentially raise address to meet alignment requirements. */
	region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);

	/* Did we raise the address above the bounds of this e820 region? */
	if (region.start > entry->addr + entry->size)
		return;

	/* Reduce size by any delta from the original address. */
	region.size -= region.start - entry->addr;

	/* Reduce maximum size to fit end of image within maximum limit. */
	if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
		region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;

	/* Walk each aligned slot and check for avoided areas. */
	for (img.start = region.start, img.size = image_size ;
	     mem_contains(&region, &img) ;
	     img.start += CONFIG_PHYSICAL_ALIGN) {
		if (mem_avoid_overlap(&img))
			continue;
		slots_append(img.start);
	}
}

static unsigned long find_random_addr(unsigned long minimum,
				      unsigned long size)
{
	int i;
	unsigned long addr;

	/* Make sure minimum is aligned. */
	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);

	/* Verify potential e820 positions, appending to slots list. */
	for (i = 0; i < real_mode->e820_entries; i++) {
		process_e820_entry(&real_mode->e820_map[i], minimum, size);
	}

	return slots_fetch_random();
}

unsigned char *choose_kernel_location(unsigned char *input,
				      unsigned long input_size,
				      unsigned char *output,
				      unsigned long output_size)
{
	unsigned long choice = (unsigned long)output;
	unsigned long random;

#ifdef CONFIG_HIBERNATION
	if (!cmdline_find_option_bool("kaslr")) {
		debug_putstr("KASLR disabled by default...\n");
		goto out;
	}
#else
	if (cmdline_find_option_bool("nokaslr")) {
		debug_putstr("KASLR disabled by cmdline...\n");
		goto out;
	}
#endif

	/* Record the various known unsafe memory ranges. */
	mem_avoid_init((unsigned long)input, input_size,
		       (unsigned long)output, output_size);

	/* Walk e820 and find a random address. */
	random = find_random_addr(choice, output_size);
	if (!random) {
		debug_putstr("KASLR could not find suitable E820 region...\n");
		goto out;
	}

	/* Always enforce the minimum. */
	if (random < choice)
		goto out;

	choice = random;
out:
	return (unsigned char *)choice;
}

#endif /* CONFIG_RANDOMIZE_BASE */
Commit	Line	Data
8ab3820f KC	1	#include "misc.h"
	2
	3	#ifdef CONFIG_RANDOMIZE_BASE
5bfce5ef KC	4	#include <asm/msr.h>
5bfce5ef KC	5	#include <asm/archrandom.h>
82fa9637	6	#include <asm/e820.h>
5bfce5ef	7
a653f356 KC	8	#include <generated/compile.h>
	9	#include <linux/module.h>
	10	#include <linux/uts.h>
	11	#include <linux/utsname.h>
	12	#include <generated/utsrelease.h>
a653f356 KC	13
a653f356 KC	14	/* Simplified build-specific string for starting entropy. */
327f7d72	15	static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
a653f356 KC	16	LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;
a653f356 KC	17
5bfce5ef KC	18	#define I8254_PORT_CONTROL 0x43
	19	#define I8254_PORT_COUNTER0 0x40
	20	#define I8254_CMD_READBACK 0xC0
	21	#define I8254_SELECT_COUNTER0 0x02
	22	#define I8254_STATUS_NOTREADY 0x40
	23	static inline u16 i8254(void)
	24	{
	25	u16 status, timer;
	26
	27	do {
	28	outb(I8254_PORT_CONTROL,
	29	I8254_CMD_READBACK \| I8254_SELECT_COUNTER0);
	30	status = inb(I8254_PORT_COUNTER0);
	31	timer = inb(I8254_PORT_COUNTER0);
	32	timer \|= inb(I8254_PORT_COUNTER0) << 8;
	33	} while (status & I8254_STATUS_NOTREADY);
	34
	35	return timer;
	36	}
	37
a653f356 KC	38	static unsigned long rotate_xor(unsigned long hash, const void *area,
	39	size_t size)
	40	{
	41	size_t i;
	42	unsigned long ptr = (unsigned long )area;
	43
	44	for (i = 0; i < size / sizeof(hash); i++) {
	45	/* Rotate by odd number of bits and XOR. */
	46	hash = (hash << ((sizeof(hash) * 8) - 7)) \| (hash >> 7);
	47	hash ^= ptr[i];
	48	}
	49
	50	return hash;
	51	}
	52
	53	/* Attempt to create a simple but unpredictable starting entropy. */
	54	static unsigned long get_random_boot(void)
	55	{
	56	unsigned long hash = 0;
	57
	58	hash = rotate_xor(hash, build_str, sizeof(build_str));
	59	hash = rotate_xor(hash, real_mode, sizeof(*real_mode));
	60
	61	return hash;
	62	}
	63
5bfce5ef KC	64	static unsigned long get_random_long(void)
5bfce5ef KC	65	{
e8236c4d PA	66	#ifdef CONFIG_X86_64
	67	const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
	68	#else
	69	const unsigned long mix_const = 0x3f39e593UL;
	70	#endif
a653f356 KC	71	unsigned long raw, random = get_random_boot();
	72	bool use_i8254 = true;
	73
	74	debug_putstr("KASLR using");
5bfce5ef KC	75
5bfce5ef KC	76	if (has_cpuflag(X86_FEATURE_RDRAND)) {
a653f356 KC	77	debug_putstr(" RDRAND");
	78	if (rdrand_long(&raw)) {
	79	random ^= raw;
	80	use_i8254 = false;
	81	}
5bfce5ef KC	82	}
	83
	84	if (has_cpuflag(X86_FEATURE_TSC)) {
a653f356 KC	85	debug_putstr(" RDTSC");
a653f356 KC	86	rdtscll(raw);
5bfce5ef	87
a653f356 KC	88	random ^= raw;
	89	use_i8254 = false;
	90	}
5bfce5ef	91
a653f356 KC	92	if (use_i8254) {
	93	debug_putstr(" i8254");
	94	random ^= i8254();
5bfce5ef KC	95	}
5bfce5ef KC	96
e8236c4d PA	97	/* Circular multiply for better bit diffusion */
	98	asm("mul %3"
	99	: "=a" (random), "=d" (raw)
	100	: "a" (random), "rm" (mix_const));
	101	random += raw;
	102
a653f356 KC	103	debug_putstr("...\n");
a653f356 KC	104
5bfce5ef KC	105	return random;
5bfce5ef KC	106	}
8ab3820f	107
82fa9637 KC	108	struct mem_vector {
	109	unsigned long start;
	110	unsigned long size;
	111	};
	112
	113	#define MEM_AVOID_MAX 5
e290e8c5	114	static struct mem_vector mem_avoid[MEM_AVOID_MAX];
82fa9637 KC	115
	116	static bool mem_contains(struct mem_vector region, struct mem_vector item)
	117	{
	118	/* Item at least partially before region. */
	119	if (item->start < region->start)
	120	return false;
	121	/* Item at least partially after region. */
	122	if (item->start + item->size > region->start + region->size)
	123	return false;
	124	return true;
	125	}
	126
	127	static bool mem_overlaps(struct mem_vector one, struct mem_vector two)
	128	{
	129	/* Item one is entirely before item two. */
	130	if (one->start + one->size <= two->start)
	131	return false;
	132	/* Item one is entirely after item two. */
	133	if (one->start >= two->start + two->size)
	134	return false;
	135	return true;
	136	}
	137
	138	static void mem_avoid_init(unsigned long input, unsigned long input_size,
	139	unsigned long output, unsigned long output_size)
	140	{
	141	u64 initrd_start, initrd_size;
	142	u64 cmd_line, cmd_line_size;
	143	unsigned long unsafe, unsafe_len;
	144	char *ptr;
	145
	146	/*
	147	* Avoid the region that is unsafe to overlap during
	148	* decompression (see calculations at top of misc.c).
	149	*/
	150	unsafe_len = (output_size >> 12) + 32768 + 18;
	151	unsafe = (unsigned long)input + input_size - unsafe_len;
	152	mem_avoid[0].start = unsafe;
	153	mem_avoid[0].size = unsafe_len;
	154
	155	/* Avoid initrd. */
	156	initrd_start = (u64)real_mode->ext_ramdisk_image << 32;
	157	initrd_start \|= real_mode->hdr.ramdisk_image;
	158	initrd_size = (u64)real_mode->ext_ramdisk_size << 32;
	159	initrd_size \|= real_mode->hdr.ramdisk_size;
	160	mem_avoid[1].start = initrd_start;
	161	mem_avoid[1].size = initrd_size;
	162
	163	/* Avoid kernel command line. */
	164	cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32;
	165	cmd_line \|= real_mode->hdr.cmd_line_ptr;
	166	/* Calculate size of cmd_line. */
	167	ptr = (char *)(unsigned long)cmd_line;
	168	for (cmd_line_size = 0; ptr[cmd_line_size++]; )
	169	;
	170	mem_avoid[2].start = cmd_line;
	171	mem_avoid[2].size = cmd_line_size;
	172
	173	/* Avoid heap memory. */
	174	mem_avoid[3].start = (unsigned long)free_mem_ptr;
	175	mem_avoid[3].size = BOOT_HEAP_SIZE;
	176
	177	/* Avoid stack memory. */
	178	mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
179	mem_avoid[4].size = BOOT_STACK_SIZE;
180	}
181
182	/* Does this memory vector overlap a known avoided area? */
e290e8c5	183	static bool mem_avoid_overlap(struct mem_vector *img)
82fa9637 KC	184	{
	185	int i;
	186
	187	for (i = 0; i < MEM_AVOID_MAX; i++) {
	188	if (mem_overlaps(img, &mem_avoid[i]))
	189	return true;
	190	}
	191
	192	return false;
	193	}
	194
e290e8c5 KC	195	static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
	196	CONFIG_PHYSICAL_ALIGN];
	197	static unsigned long slot_max;
82fa9637 KC	198
	199	static void slots_append(unsigned long addr)
	200	{
	201	/* Overflowing the slots list should be impossible. */
	202	if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
	203	CONFIG_PHYSICAL_ALIGN)
	204	return;
	205
	206	slots[slot_max++] = addr;
	207	}
	208
	209	static unsigned long slots_fetch_random(void)
	210	{
	211	/* Handle case of no slots stored. */
	212	if (slot_max == 0)
	213	return 0;
	214
	215	return slots[get_random_long() % slot_max];
	216	}
	217
	218	static void process_e820_entry(struct e820entry *entry,
	219	unsigned long minimum,
	220	unsigned long image_size)
	221	{
	222	struct mem_vector region, img;
	223
	224	/* Skip non-RAM entries. */
	225	if (entry->type != E820_RAM)
	226	return;
	227
	228	/* Ignore entries entirely above our maximum. */
	229	if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
	230	return;
	231
	232	/* Ignore entries entirely below our minimum. */
	233	if (entry->addr + entry->size < minimum)
	234	return;
	235
	236	region.start = entry->addr;
	237	region.size = entry->size;
	238
	239	/* Potentially raise address to minimum location. */
	240	if (region.start < minimum)
	241	region.start = minimum;
	242
	243	/* Potentially raise address to meet alignment requirements. */
	244	region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
	245
	246	/* Did we raise the address above the bounds of this e820 region? */
	247	if (region.start > entry->addr + entry->size)
	248	return;
	249
	250	/* Reduce size by any delta from the original address. */
	251	region.size -= region.start - entry->addr;
	252
	253	/* Reduce maximum size to fit end of image within maximum limit. */
	254	if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
	255	region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;
	256
	257	/* Walk each aligned slot and check for avoided areas. */
	258	for (img.start = region.start, img.size = image_size ;
	259	mem_contains(&region, &img) ;
	260	img.start += CONFIG_PHYSICAL_ALIGN) {
	261	if (mem_avoid_overlap(&img))
262	continue;
263	slots_append(img.start);
264	}
265	}
266
267	static unsigned long find_random_addr(unsigned long minimum,
268	unsigned long size)
269	{
270	int i;
271	unsigned long addr;
272
273	/* Make sure minimum is aligned. */
274	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
275
276	/* Verify potential e820 positions, appending to slots list. */
277	for (i = 0; i < real_mode->e820_entries; i++) {
278	process_e820_entry(&real_mode->e820_map[i], minimum, size);
279	}
280
281	return slots_fetch_random();
282	}
283
8ab3820f KC	284	unsigned char choose_kernel_location(unsigned char input,
	285	unsigned long input_size,
	286	unsigned char *output,
	287	unsigned long output_size)
	288	{
	289	unsigned long choice = (unsigned long)output;
82fa9637	290	unsigned long random;
8ab3820f	291
24f2e027 KC	292	#ifdef CONFIG_HIBERNATION
	293	if (!cmdline_find_option_bool("kaslr")) {
	294	debug_putstr("KASLR disabled by default...\n");
	295	goto out;
	296	}
	297	#else
8ab3820f	298	if (cmdline_find_option_bool("nokaslr")) {
24f2e027	299	debug_putstr("KASLR disabled by cmdline...\n");
8ab3820f KC	300	goto out;
8ab3820f KC	301	}
24f2e027	302	#endif
8ab3820f	303
82fa9637 KC	304	/* Record the various known unsafe memory ranges. */
	305	mem_avoid_init((unsigned long)input, input_size,
	306	(unsigned long)output, output_size);
	307
	308	/* Walk e820 and find a random address. */
	309	random = find_random_addr(choice, output_size);
	310	if (!random) {
	311	debug_putstr("KASLR could not find suitable E820 region...\n");
	312	goto out;
	313	}
	314
	315	/* Always enforce the minimum. */
	316	if (random < choice)
	317	goto out;
8ab3820f	318
82fa9637	319	choice = random;
8ab3820f KC	320	out:
	321	return (unsigned char *)choice;
	322	}
	323
	324	#endif /* CONFIG_RANDOMIZE_BASE */