[deliverable/linux.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)
{
	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();
	}

	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	{
a653f356 KC	67	unsigned long raw, random = get_random_boot();
	68	bool use_i8254 = true;
	69
	70	debug_putstr("KASLR using");
5bfce5ef KC	71
5bfce5ef KC	72	if (has_cpuflag(X86_FEATURE_RDRAND)) {
a653f356 KC	73	debug_putstr(" RDRAND");
	74	if (rdrand_long(&raw)) {
	75	random ^= raw;
	76	use_i8254 = false;
	77	}
5bfce5ef KC	78	}
	79
	80	if (has_cpuflag(X86_FEATURE_TSC)) {
a653f356 KC	81	debug_putstr(" RDTSC");
a653f356 KC	82	rdtscll(raw);
5bfce5ef	83
a653f356 KC	84	random ^= raw;
	85	use_i8254 = false;
	86	}
5bfce5ef	87
a653f356 KC	88	if (use_i8254) {
	89	debug_putstr(" i8254");
	90	random ^= i8254();
5bfce5ef KC	91	}
5bfce5ef KC	92
a653f356 KC	93	debug_putstr("...\n");
a653f356 KC	94
5bfce5ef KC	95	return random;
5bfce5ef KC	96	}
8ab3820f	97
82fa9637 KC	98	struct mem_vector {
	99	unsigned long start;
	100	unsigned long size;
	101	};
	102
	103	#define MEM_AVOID_MAX 5
	104	struct mem_vector mem_avoid[MEM_AVOID_MAX];
	105
	106	static bool mem_contains(struct mem_vector region, struct mem_vector item)
	107	{
	108	/* Item at least partially before region. */
	109	if (item->start < region->start)
	110	return false;
	111	/* Item at least partially after region. */
	112	if (item->start + item->size > region->start + region->size)
	113	return false;
	114	return true;
	115	}
	116
	117	static bool mem_overlaps(struct mem_vector one, struct mem_vector two)
	118	{
	119	/* Item one is entirely before item two. */
	120	if (one->start + one->size <= two->start)
	121	return false;
	122	/* Item one is entirely after item two. */
	123	if (one->start >= two->start + two->size)
	124	return false;
	125	return true;
	126	}
	127
	128	static void mem_avoid_init(unsigned long input, unsigned long input_size,
	129	unsigned long output, unsigned long output_size)
	130	{
	131	u64 initrd_start, initrd_size;
	132	u64 cmd_line, cmd_line_size;
	133	unsigned long unsafe, unsafe_len;
	134	char *ptr;
	135
	136	/*
	137	* Avoid the region that is unsafe to overlap during
	138	* decompression (see calculations at top of misc.c).
	139	*/
	140	unsafe_len = (output_size >> 12) + 32768 + 18;
	141	unsafe = (unsigned long)input + input_size - unsafe_len;
	142	mem_avoid[0].start = unsafe;
	143	mem_avoid[0].size = unsafe_len;
	144
	145	/* Avoid initrd. */
	146	initrd_start = (u64)real_mode->ext_ramdisk_image << 32;
	147	initrd_start \|= real_mode->hdr.ramdisk_image;
	148	initrd_size = (u64)real_mode->ext_ramdisk_size << 32;
	149	initrd_size \|= real_mode->hdr.ramdisk_size;
	150	mem_avoid[1].start = initrd_start;
	151	mem_avoid[1].size = initrd_size;
	152
	153	/* Avoid kernel command line. */
	154	cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32;
	155	cmd_line \|= real_mode->hdr.cmd_line_ptr;
	156	/* Calculate size of cmd_line. */
	157	ptr = (char *)(unsigned long)cmd_line;
	158	for (cmd_line_size = 0; ptr[cmd_line_size++]; )
	159	;
	160	mem_avoid[2].start = cmd_line;
	161	mem_avoid[2].size = cmd_line_size;
162
163	/* Avoid heap memory. */
164	mem_avoid[3].start = (unsigned long)free_mem_ptr;
165	mem_avoid[3].size = BOOT_HEAP_SIZE;
166
167	/* Avoid stack memory. */
168	mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
169	mem_avoid[4].size = BOOT_STACK_SIZE;
170	}
171
172	/* Does this memory vector overlap a known avoided area? */
173	bool mem_avoid_overlap(struct mem_vector *img)
174	{
175	int i;
176
177	for (i = 0; i < MEM_AVOID_MAX; i++) {
178	if (mem_overlaps(img, &mem_avoid[i]))
179	return true;
180	}
181
182	return false;
183	}
184
185	unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET / CONFIG_PHYSICAL_ALIGN];
186	unsigned long slot_max = 0;
187
188	static void slots_append(unsigned long addr)
189	{
190	/* Overflowing the slots list should be impossible. */
191	if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
192	CONFIG_PHYSICAL_ALIGN)
193	return;
194
195	slots[slot_max++] = addr;
196	}
197
198	static unsigned long slots_fetch_random(void)
199	{
200	/* Handle case of no slots stored. */
201	if (slot_max == 0)
202	return 0;
203
204	return slots[get_random_long() % slot_max];
205	}
206
207	static void process_e820_entry(struct e820entry *entry,
208	unsigned long minimum,
209	unsigned long image_size)
210	{
211	struct mem_vector region, img;
212
213	/* Skip non-RAM entries. */
214	if (entry->type != E820_RAM)
215	return;
216
217	/* Ignore entries entirely above our maximum. */
218	if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
219	return;
220
221	/* Ignore entries entirely below our minimum. */
222	if (entry->addr + entry->size < minimum)
223	return;
224
225	region.start = entry->addr;
226	region.size = entry->size;
227
228	/* Potentially raise address to minimum location. */
229	if (region.start < minimum)
230	region.start = minimum;
231
232	/* Potentially raise address to meet alignment requirements. */
233	region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
234
235	/* Did we raise the address above the bounds of this e820 region? */
236	if (region.start > entry->addr + entry->size)
237	return;
238
239	/* Reduce size by any delta from the original address. */
240	region.size -= region.start - entry->addr;
241
242	/* Reduce maximum size to fit end of image within maximum limit. */
243	if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
244	region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;
245
246	/* Walk each aligned slot and check for avoided areas. */
247	for (img.start = region.start, img.size = image_size ;
248	mem_contains(&region, &img) ;
249	img.start += CONFIG_PHYSICAL_ALIGN) {
250	if (mem_avoid_overlap(&img))
251	continue;
252	slots_append(img.start);
253	}
254	}
255
256	static unsigned long find_random_addr(unsigned long minimum,
257	unsigned long size)
258	{
259	int i;
260	unsigned long addr;
261
262	/* Make sure minimum is aligned. */
263	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
264
265	/* Verify potential e820 positions, appending to slots list. */
266	for (i = 0; i < real_mode->e820_entries; i++) {
267	process_e820_entry(&real_mode->e820_map[i], minimum, size);
268	}
269
270	return slots_fetch_random();
271	}
272
8ab3820f KC	273	unsigned char choose_kernel_location(unsigned char input,
	274	unsigned long input_size,
	275	unsigned char *output,
	276	unsigned long output_size)
	277	{
	278	unsigned long choice = (unsigned long)output;
82fa9637	279	unsigned long random;
8ab3820f KC	280
	281	if (cmdline_find_option_bool("nokaslr")) {
	282	debug_putstr("KASLR disabled...\n");
	283	goto out;
	284	}
	285
82fa9637 KC	286	/* Record the various known unsafe memory ranges. */
	287	mem_avoid_init((unsigned long)input, input_size,
	288	(unsigned long)output, output_size);
	289
	290	/* Walk e820 and find a random address. */
	291	random = find_random_addr(choice, output_size);
	292	if (!random) {
	293	debug_putstr("KASLR could not find suitable E820 region...\n");
	294	goto out;
	295	}
	296
	297	/* Always enforce the minimum. */
	298	if (random < choice)
	299	goto out;
8ab3820f	300
82fa9637	301	choice = random;
8ab3820f KC	302	out:
	303	return (unsigned char *)choice;
	304	}
	305
	306	#endif /* CONFIG_RANDOMIZE_BASE */