[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>
#include <linux/version.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
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? */
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;
}

unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET / CONFIG_PHYSICAL_ALIGN];
unsigned long slot_max = 0;

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;

	if (cmdline_find_option_bool("nokaslr")) {
		debug_putstr("KASLR disabled...\n");
		goto out;
	}

	/* 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>
	13	#include <linux/version.h>
	14
	15	/* Simplified build-specific string for starting entropy. */
	16	static const char *build_str = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
	17	LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;
	18
5bfce5ef KC	19	#define I8254_PORT_CONTROL 0x43
	20	#define I8254_PORT_COUNTER0 0x40
	21	#define I8254_CMD_READBACK 0xC0
	22	#define I8254_SELECT_COUNTER0 0x02
	23	#define I8254_STATUS_NOTREADY 0x40
	24	static inline u16 i8254(void)
	25	{
	26	u16 status, timer;
	27
	28	do {
	29	outb(I8254_PORT_CONTROL,
	30	I8254_CMD_READBACK \| I8254_SELECT_COUNTER0);
	31	status = inb(I8254_PORT_COUNTER0);
	32	timer = inb(I8254_PORT_COUNTER0);
	33	timer \|= inb(I8254_PORT_COUNTER0) << 8;
	34	} while (status & I8254_STATUS_NOTREADY);
	35
	36	return timer;
	37	}
	38
a653f356 KC	39	static unsigned long rotate_xor(unsigned long hash, const void *area,
	40	size_t size)
	41	{
	42	size_t i;
	43	unsigned long ptr = (unsigned long )area;
	44
	45	for (i = 0; i < size / sizeof(hash); i++) {
	46	/* Rotate by odd number of bits and XOR. */
	47	hash = (hash << ((sizeof(hash) * 8) - 7)) \| (hash >> 7);
	48	hash ^= ptr[i];
	49	}
	50
	51	return hash;
	52	}
	53
	54	/* Attempt to create a simple but unpredictable starting entropy. */
	55	static unsigned long get_random_boot(void)
	56	{
	57	unsigned long hash = 0;
	58
	59	hash = rotate_xor(hash, build_str, sizeof(build_str));
	60	hash = rotate_xor(hash, real_mode, sizeof(*real_mode));
	61
	62	return hash;
	63	}
	64
5bfce5ef KC	65	static unsigned long get_random_long(void)
5bfce5ef KC	66	{
e8236c4d PA	67	#ifdef CONFIG_X86_64
	68	const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
	69	#else
	70	const unsigned long mix_const = 0x3f39e593UL;
	71	#endif
a653f356 KC	72	unsigned long raw, random = get_random_boot();
	73	bool use_i8254 = true;
	74
	75	debug_putstr("KASLR using");
5bfce5ef KC	76
5bfce5ef KC	77	if (has_cpuflag(X86_FEATURE_RDRAND)) {
a653f356 KC	78	debug_putstr(" RDRAND");
	79	if (rdrand_long(&raw)) {
	80	random ^= raw;
	81	use_i8254 = false;
	82	}
5bfce5ef KC	83	}
	84
	85	if (has_cpuflag(X86_FEATURE_TSC)) {
a653f356 KC	86	debug_putstr(" RDTSC");
a653f356 KC	87	rdtscll(raw);
5bfce5ef	88
a653f356 KC	89	random ^= raw;
	90	use_i8254 = false;
	91	}
5bfce5ef	92
a653f356 KC	93	if (use_i8254) {
	94	debug_putstr(" i8254");
	95	random ^= i8254();
5bfce5ef KC	96	}
5bfce5ef KC	97
e8236c4d PA	98	/* Circular multiply for better bit diffusion */
	99	asm("mul %3"
	100	: "=a" (random), "=d" (raw)
	101	: "a" (random), "rm" (mix_const));
	102	random += raw;
	103
a653f356 KC	104	debug_putstr("...\n");
a653f356 KC	105
5bfce5ef KC	106	return random;
5bfce5ef KC	107	}
8ab3820f	108
82fa9637 KC	109	struct mem_vector {
	110	unsigned long start;
	111	unsigned long size;
	112	};
	113
	114	#define MEM_AVOID_MAX 5
	115	struct mem_vector mem_avoid[MEM_AVOID_MAX];
	116
	117	static bool mem_contains(struct mem_vector region, struct mem_vector item)
	118	{
	119	/* Item at least partially before region. */
	120	if (item->start < region->start)
	121	return false;
	122	/* Item at least partially after region. */
	123	if (item->start + item->size > region->start + region->size)
	124	return false;
	125	return true;
	126	}
	127
	128	static bool mem_overlaps(struct mem_vector one, struct mem_vector two)
	129	{
	130	/* Item one is entirely before item two. */
	131	if (one->start + one->size <= two->start)
	132	return false;
	133	/* Item one is entirely after item two. */
	134	if (one->start >= two->start + two->size)
	135	return false;
	136	return true;
	137	}
	138
	139	static void mem_avoid_init(unsigned long input, unsigned long input_size,
	140	unsigned long output, unsigned long output_size)
	141	{
	142	u64 initrd_start, initrd_size;
	143	u64 cmd_line, cmd_line_size;
	144	unsigned long unsafe, unsafe_len;
	145	char *ptr;
	146
	147	/*
	148	* Avoid the region that is unsafe to overlap during
	149	* decompression (see calculations at top of misc.c).
	150	*/
	151	unsafe_len = (output_size >> 12) + 32768 + 18;
	152	unsafe = (unsigned long)input + input_size - unsafe_len;
	153	mem_avoid[0].start = unsafe;
	154	mem_avoid[0].size = unsafe_len;
	155
	156	/* Avoid initrd. */
	157	initrd_start = (u64)real_mode->ext_ramdisk_image << 32;
	158	initrd_start \|= real_mode->hdr.ramdisk_image;
	159	initrd_size = (u64)real_mode->ext_ramdisk_size << 32;
	160	initrd_size \|= real_mode->hdr.ramdisk_size;
	161	mem_avoid[1].start = initrd_start;
	162	mem_avoid[1].size = initrd_size;
	163
	164	/* Avoid kernel command line. */
	165	cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32;
	166	cmd_line \|= real_mode->hdr.cmd_line_ptr;
	167	/* Calculate size of cmd_line. */
	168	ptr = (char *)(unsigned long)cmd_line;
	169	for (cmd_line_size = 0; ptr[cmd_line_size++]; )
	170	;
	171	mem_avoid[2].start = cmd_line;
	172	mem_avoid[2].size = cmd_line_size;
173
174	/* Avoid heap memory. */
175	mem_avoid[3].start = (unsigned long)free_mem_ptr;
176	mem_avoid[3].size = BOOT_HEAP_SIZE;
177
178	/* Avoid stack memory. */
179	mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
180	mem_avoid[4].size = BOOT_STACK_SIZE;
181	}
182
183	/* Does this memory vector overlap a known avoided area? */
184	bool mem_avoid_overlap(struct mem_vector *img)
185	{
186	int i;
187
188	for (i = 0; i < MEM_AVOID_MAX; i++) {
189	if (mem_overlaps(img, &mem_avoid[i]))
190	return true;
191	}
192
193	return false;
194	}
195
196	unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET / CONFIG_PHYSICAL_ALIGN];
197	unsigned long slot_max = 0;
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 KC	291
	292	if (cmdline_find_option_bool("nokaslr")) {
	293	debug_putstr("KASLR disabled...\n");
	294	goto out;
	295	}
	296
82fa9637 KC	297	/* Record the various known unsafe memory ranges. */
	298	mem_avoid_init((unsigned long)input, input_size,
	299	(unsigned long)output, output_size);
	300
	301	/* Walk e820 and find a random address. */
	302	random = find_random_addr(choice, output_size);
	303	if (!random) {
	304	debug_putstr("KASLR could not find suitable E820 region...\n");
	305	goto out;
	306	}
	307
	308	/* Always enforce the minimum. */
	309	if (random < choice)
	310	goto out;
8ab3820f	311
82fa9637	312	choice = random;
8ab3820f KC	313	out:
	314	return (unsigned char *)choice;
	315	}
	316
	317	#endif /* CONFIG_RANDOMIZE_BASE */