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

#include "misc.h"

#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");
		raw = rdtsc();

		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;
	struct setup_data *ptr;

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

	/* Avoid all entries in the setup_data linked list. */
	ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data;
	while (ptr) {
		struct mem_vector avoid;

		avoid.start = (unsigned long)ptr;
		avoid.size = sizeof(*ptr) + ptr->len;

		if (mem_overlaps(img, &avoid))
			return true;

		ptr = (struct setup_data *)(unsigned long)ptr->next;
	}

	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(struct boot_params *boot_params,
				      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

	boot_params->hdr.loadflags |= KASLR_FLAG;

	/* 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;
}
Commit	Line	Data
8ab3820f KC	1	#include "misc.h"
8ab3820f KC	2
5bfce5ef KC	3	#include <asm/msr.h>
5bfce5ef KC	4	#include <asm/archrandom.h>
82fa9637	5	#include <asm/e820.h>
5bfce5ef	6
a653f356 KC	7	#include <generated/compile.h>
	8	#include <linux/module.h>
	9	#include <linux/uts.h>
	10	#include <linux/utsname.h>
	11	#include <generated/utsrelease.h>
a653f356 KC	12
a653f356 KC	13	/* Simplified build-specific string for starting entropy. */
327f7d72	14	static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
a653f356 KC	15	LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;
a653f356 KC	16
5bfce5ef KC	17	#define I8254_PORT_CONTROL 0x43
	18	#define I8254_PORT_COUNTER0 0x40
	19	#define I8254_CMD_READBACK 0xC0
	20	#define I8254_SELECT_COUNTER0 0x02
	21	#define I8254_STATUS_NOTREADY 0x40
	22	static inline u16 i8254(void)
	23	{
	24	u16 status, timer;
	25
	26	do {
	27	outb(I8254_PORT_CONTROL,
	28	I8254_CMD_READBACK \| I8254_SELECT_COUNTER0);
	29	status = inb(I8254_PORT_COUNTER0);
	30	timer = inb(I8254_PORT_COUNTER0);
	31	timer \|= inb(I8254_PORT_COUNTER0) << 8;
	32	} while (status & I8254_STATUS_NOTREADY);
	33
	34	return timer;
	35	}
	36
a653f356 KC	37	static unsigned long rotate_xor(unsigned long hash, const void *area,
	38	size_t size)
	39	{
	40	size_t i;
	41	unsigned long ptr = (unsigned long )area;
	42
	43	for (i = 0; i < size / sizeof(hash); i++) {
	44	/* Rotate by odd number of bits and XOR. */
	45	hash = (hash << ((sizeof(hash) * 8) - 7)) \| (hash >> 7);
	46	hash ^= ptr[i];
	47	}
	48
	49	return hash;
	50	}
	51
	52	/* Attempt to create a simple but unpredictable starting entropy. */
	53	static unsigned long get_random_boot(void)
	54	{
	55	unsigned long hash = 0;
	56
	57	hash = rotate_xor(hash, build_str, sizeof(build_str));
	58	hash = rotate_xor(hash, real_mode, sizeof(*real_mode));
	59
	60	return hash;
	61	}
	62
5bfce5ef KC	63	static unsigned long get_random_long(void)
5bfce5ef KC	64	{
e8236c4d PA	65	#ifdef CONFIG_X86_64
	66	const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
	67	#else
	68	const unsigned long mix_const = 0x3f39e593UL;
	69	#endif
a653f356 KC	70	unsigned long raw, random = get_random_boot();
	71	bool use_i8254 = true;
	72
	73	debug_putstr("KASLR using");
5bfce5ef KC	74
5bfce5ef KC	75	if (has_cpuflag(X86_FEATURE_RDRAND)) {
a653f356 KC	76	debug_putstr(" RDRAND");
	77	if (rdrand_long(&raw)) {
	78	random ^= raw;
	79	use_i8254 = false;
	80	}
5bfce5ef KC	81	}
	82
	83	if (has_cpuflag(X86_FEATURE_TSC)) {
a653f356	84	debug_putstr(" RDTSC");
4ea1636b	85	raw = rdtsc();
5bfce5ef	86
a653f356 KC	87	random ^= raw;
	88	use_i8254 = false;
	89	}
5bfce5ef	90
a653f356 KC	91	if (use_i8254) {
	92	debug_putstr(" i8254");
	93	random ^= i8254();
5bfce5ef KC	94	}
5bfce5ef KC	95
e8236c4d PA	96	/* Circular multiply for better bit diffusion */
	97	asm("mul %3"
	98	: "=a" (random), "=d" (raw)
	99	: "a" (random), "rm" (mix_const));
	100	random += raw;
	101
a653f356 KC	102	debug_putstr("...\n");
a653f356 KC	103
5bfce5ef KC	104	return random;
5bfce5ef KC	105	}
8ab3820f	106
82fa9637 KC	107	struct mem_vector {
	108	unsigned long start;
	109	unsigned long size;
	110	};
	111
	112	#define MEM_AVOID_MAX 5
e290e8c5	113	static struct mem_vector mem_avoid[MEM_AVOID_MAX];
82fa9637 KC	114
	115	static bool mem_contains(struct mem_vector region, struct mem_vector item)
	116	{
	117	/* Item at least partially before region. */
	118	if (item->start < region->start)
	119	return false;
	120	/* Item at least partially after region. */
	121	if (item->start + item->size > region->start + region->size)
	122	return false;
	123	return true;
	124	}
	125
	126	static bool mem_overlaps(struct mem_vector one, struct mem_vector two)
	127	{
	128	/* Item one is entirely before item two. */
	129	if (one->start + one->size <= two->start)
	130	return false;
	131	/* Item one is entirely after item two. */
	132	if (one->start >= two->start + two->size)
	133	return false;
	134	return true;
	135	}
	136
	137	static void mem_avoid_init(unsigned long input, unsigned long input_size,
	138	unsigned long output, unsigned long output_size)
	139	{
	140	u64 initrd_start, initrd_size;
	141	u64 cmd_line, cmd_line_size;
	142	unsigned long unsafe, unsafe_len;
	143	char *ptr;
	144
	145	/*
	146	* Avoid the region that is unsafe to overlap during
	147	* decompression (see calculations at top of misc.c).
	148	*/
	149	unsafe_len = (output_size >> 12) + 32768 + 18;
	150	unsafe = (unsigned long)input + input_size - unsafe_len;
	151	mem_avoid[0].start = unsafe;
	152	mem_avoid[0].size = unsafe_len;
	153
	154	/* Avoid initrd. */
	155	initrd_start = (u64)real_mode->ext_ramdisk_image << 32;
	156	initrd_start \|= real_mode->hdr.ramdisk_image;
	157	initrd_size = (u64)real_mode->ext_ramdisk_size << 32;
	158	initrd_size \|= real_mode->hdr.ramdisk_size;
	159	mem_avoid[1].start = initrd_start;
	160	mem_avoid[1].size = initrd_size;
	161
	162	/* Avoid kernel command line. */
	163	cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32;
	164	cmd_line \|= real_mode->hdr.cmd_line_ptr;
	165	/* Calculate size of cmd_line. */
	166	ptr = (char *)(unsigned long)cmd_line;
	167	for (cmd_line_size = 0; ptr[cmd_line_size++]; )
	168	;
	169	mem_avoid[2].start = cmd_line;
	170	mem_avoid[2].size = cmd_line_size;
	171
	172	/* Avoid heap memory. */
	173	mem_avoid[3].start = (unsigned long)free_mem_ptr;
	174	mem_avoid[3].size = BOOT_HEAP_SIZE;
	175
	176	/* Avoid stack memory. */
	177	mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
178	mem_avoid[4].size = BOOT_STACK_SIZE;
179	}
180
181	/* Does this memory vector overlap a known avoided area? */
e290e8c5	182	static bool mem_avoid_overlap(struct mem_vector *img)
82fa9637 KC	183	{
82fa9637 KC	184	int i;
0cacbfbe	185	struct setup_data *ptr;
82fa9637 KC	186
	187	for (i = 0; i < MEM_AVOID_MAX; i++) {
	188	if (mem_overlaps(img, &mem_avoid[i]))
	189	return true;
	190	}
	191
0cacbfbe KC	192	/* Avoid all entries in the setup_data linked list. */
	193	ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data;
	194	while (ptr) {
	195	struct mem_vector avoid;
	196
20cc2888	197	avoid.start = (unsigned long)ptr;
0cacbfbe KC	198	avoid.size = sizeof(*ptr) + ptr->len;
	199
	200	if (mem_overlaps(img, &avoid))
	201	return true;
	202
	203	ptr = (struct setup_data *)(unsigned long)ptr->next;
	204	}
	205
82fa9637 KC	206	return false;
	207	}
	208
e290e8c5 KC	209	static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
	210	CONFIG_PHYSICAL_ALIGN];
	211	static unsigned long slot_max;
82fa9637 KC	212
	213	static void slots_append(unsigned long addr)
	214	{
	215	/* Overflowing the slots list should be impossible. */
	216	if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
	217	CONFIG_PHYSICAL_ALIGN)
	218	return;
	219
	220	slots[slot_max++] = addr;
	221	}
	222
	223	static unsigned long slots_fetch_random(void)
	224	{
	225	/* Handle case of no slots stored. */
	226	if (slot_max == 0)
	227	return 0;
	228
	229	return slots[get_random_long() % slot_max];
	230	}
	231
	232	static void process_e820_entry(struct e820entry *entry,
	233	unsigned long minimum,
	234	unsigned long image_size)
	235	{
	236	struct mem_vector region, img;
	237
	238	/* Skip non-RAM entries. */
	239	if (entry->type != E820_RAM)
	240	return;
	241
	242	/* Ignore entries entirely above our maximum. */
	243	if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
	244	return;
	245
	246	/* Ignore entries entirely below our minimum. */
	247	if (entry->addr + entry->size < minimum)
	248	return;
	249
	250	region.start = entry->addr;
	251	region.size = entry->size;
	252
	253	/* Potentially raise address to minimum location. */
	254	if (region.start < minimum)
	255	region.start = minimum;
	256
	257	/* Potentially raise address to meet alignment requirements. */
	258	region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
	259
	260	/* Did we raise the address above the bounds of this e820 region? */
	261	if (region.start > entry->addr + entry->size)
	262	return;
	263
	264	/* Reduce size by any delta from the original address. */
	265	region.size -= region.start - entry->addr;
	266
	267	/* Reduce maximum size to fit end of image within maximum limit. */
	268	if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
	269	region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;
	270
	271	/* Walk each aligned slot and check for avoided areas. */
	272	for (img.start = region.start, img.size = image_size ;
	273	mem_contains(&region, &img) ;
	274	img.start += CONFIG_PHYSICAL_ALIGN) {
	275	if (mem_avoid_overlap(&img))
276	continue;
277	slots_append(img.start);
278	}
279	}
280
281	static unsigned long find_random_addr(unsigned long minimum,
282	unsigned long size)
283	{
284	int i;
285	unsigned long addr;
286
287	/* Make sure minimum is aligned. */
288	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
289
290	/* Verify potential e820 positions, appending to slots list. */
291	for (i = 0; i < real_mode->e820_entries; i++) {
292	process_e820_entry(&real_mode->e820_map[i], minimum, size);
293	}
294
295	return slots_fetch_random();
296	}
297
78cac48c BP	298	unsigned char choose_kernel_location(struct boot_params boot_params,
78cac48c BP	299	unsigned char *input,
8ab3820f KC	300	unsigned long input_size,
	301	unsigned char *output,
	302	unsigned long output_size)
	303	{
	304	unsigned long choice = (unsigned long)output;
82fa9637	305	unsigned long random;
8ab3820f	306
24f2e027 KC	307	#ifdef CONFIG_HIBERNATION
	308	if (!cmdline_find_option_bool("kaslr")) {
	309	debug_putstr("KASLR disabled by default...\n");
	310	goto out;
	311	}
	312	#else
8ab3820f	313	if (cmdline_find_option_bool("nokaslr")) {
24f2e027	314	debug_putstr("KASLR disabled by cmdline...\n");
8ab3820f KC	315	goto out;
8ab3820f KC	316	}
24f2e027	317	#endif
8ab3820f	318
78cac48c BP	319	boot_params->hdr.loadflags \|= KASLR_FLAG;
78cac48c BP	320
82fa9637 KC	321	/* Record the various known unsafe memory ranges. */
	322	mem_avoid_init((unsigned long)input, input_size,
	323	(unsigned long)output, output_size);
	324
	325	/* Walk e820 and find a random address. */
	326	random = find_random_addr(choice, output_size);
	327	if (!random) {
	328	debug_putstr("KASLR could not find suitable E820 region...\n");
	329	goto out;
	330	}
	331
	332	/* Always enforce the minimum. */
	333	if (random < choice)
	334	goto out;
8ab3820f	335
82fa9637	336	choice = random;
8ab3820f KC	337	out:
	338	return (unsigned char *)choice;
	339	}