kasan.c   [plain text]

/*
 * Copyright (c) 2016 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <vm/vm_map.h>
#include <kern/assert.h>
#include <kern/cpu_data.h>
#include <kern/backtrace.h>
#include <machine/machine_routines.h>
#include <kern/locks.h>
#include <kern/simple_lock.h>
#include <kern/debug.h>
#include <kern/kalloc.h>
#include <kern/zalloc.h>
#include <mach/mach_vm.h>
#include <mach/mach_types.h>
#include <mach/vm_param.h>
#include <mach/machine/vm_param.h>
#include <libkern/libkern.h>
#include <libkern/OSAtomic.h>
#include <libkern/kernel_mach_header.h>
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <kern/thread.h>
#include <machine/atomic.h>

#include <kasan.h>
#include <kasan_internal.h>
#include <memintrinsics.h>

#if !KASAN_DEBUG
# undef NOINLINE
# define NOINLINE
#endif

const uintptr_t __asan_shadow_memory_dynamic_address = KASAN_SHIFT;

static long kexts_loaded;

long shadow_pages_total;
long shadow_pages_used;

vm_offset_t kernel_vbase;
vm_offset_t kernel_vtop;

static bool kasan_initialized;
static int kasan_enabled;
static int quarantine_enabled = 1;

static void kasan_crash_report(uptr p, uptr width, unsigned access_type);
extern vm_offset_t ml_stack_base(void);
extern vm_size_t ml_stack_size(void);

#define ABI_UNSUPPORTED do { panic("KASan: unsupported ABI: %s\n", __func__); } while (0)

#define BACKTRACE_MAXFRAMES 16

decl_simple_lock_data(, kasan_vm_lock);

_Atomic int unsafe_count = 0;

void
kasan_unsafe_start(void)
{
	if (__c11_atomic_fetch_add(&unsafe_count, 1, memory_order_relaxed) == 128) {
		panic("kasan_unsafe_start overflow");
	}
}

void
kasan_unsafe_end(void)
{
	if (__c11_atomic_fetch_sub(&unsafe_count, 1, memory_order_relaxed) == 0) {
		panic("kasan_unsafe_end underflow");
	}
}

static bool
kasan_in_unsafe(void)
{
	return atomic_load_explicit(&unsafe_count, memory_order_relaxed) != 0;
}

/*
 * kasan is called from the interrupt path, so we need to disable interrupts to
 * ensure atomicity manipulating the global objects
 */
void
kasan_lock(boolean_t *b)
{
	*b = ml_set_interrupts_enabled(false);
	simple_lock(&kasan_vm_lock);
}

void
kasan_unlock(boolean_t b)
{
	simple_unlock(&kasan_vm_lock);
	ml_set_interrupts_enabled(b);
}

/*
 * poison redzones in the shadow map
 */
void NOINLINE
kasan_poison(vm_offset_t base, vm_size_t size, vm_size_t leftrz, vm_size_t rightrz, uint8_t flags)
{
	uint8_t *shadow = SHADOW_FOR_ADDRESS(base);
	uint8_t partial = size & 0x07;
	vm_size_t total = leftrz + size + rightrz;
	vm_size_t i = 0;

	/* base must be 8-byte aligned */
	/* any left redzone must be a multiple of 8 */
	/* total region must cover 8-byte multiple */
	assert((base & 0x07) == 0);
	assert((leftrz & 0x07) == 0);
	assert((total & 0x07) == 0);

	if (!kasan_enabled || !kasan_initialized) {
		return;
	}

	leftrz /= 8;
	size /= 8;
	total /= 8;

	uint8_t l_flags = flags;
	uint8_t r_flags = flags;

	if (flags == ASAN_STACK_RZ) {
		l_flags = ASAN_STACK_LEFT_RZ;
		r_flags = ASAN_STACK_RIGHT_RZ;
	} else if (flags == ASAN_HEAP_RZ) {
		l_flags = ASAN_HEAP_LEFT_RZ;
		r_flags = ASAN_HEAP_RIGHT_RZ;
	}

	/*
	 * poison the redzones and unpoison the valid bytes
	 */
	for (; i < leftrz; i++) {
		shadow[i] = l_flags;
	}
	for (; i < leftrz + size; i++) {
		shadow[i] = ASAN_VALID; /* not strictly necessary */
	}
	if (partial && (i < total)) {
		shadow[i] = partial;
		i++;
	}
	for (; i < total; i++) {
		shadow[i] = r_flags;
	}

	asm volatile("" ::: "memory"); /* compiler barrier XXX: is this needed? */
}

void
kasan_poison_range(vm_offset_t base, vm_size_t size, uint8_t flags)
{
	/* base must be 8-byte aligned */
	/* total region must cover 8-byte multiple */
	assert((base & 0x07) == 0);
	assert((size & 0x07) == 0);
	kasan_poison(base, 0, 0, size, flags);
}

void NOINLINE
kasan_unpoison(void *base, vm_size_t size)
{
	kasan_poison((vm_offset_t)base, size, 0, 0, 0);
}

void NOINLINE
kasan_unpoison_stack(vm_offset_t base, vm_size_t size)
{
	assert(base);
	assert(size);
	kasan_unpoison((void *)base, size);
}

/*
 * write junk into the redzones
*/
static void NOINLINE
kasan_rz_clobber(vm_offset_t base, vm_size_t size, vm_size_t leftrz, vm_size_t rightrz)
{
#if KASAN_DEBUG
	vm_size_t i;
	const uint8_t deadbeef[] = { 0xde, 0xad, 0xbe, 0xef };
	const uint8_t c0ffee[] = { 0xc0, 0xff, 0xee, 0xc0 };
	uint8_t *buf = (uint8_t *)base;

	/* base must be 8-byte aligned */
	/* any left redzone must be a multiple of 8 */
	/* total region must cover 8-byte multiple */
	assert((base & 0x07) == 0);
	assert((leftrz & 0x07) == 0);
	assert(((size + leftrz + rightrz) & 0x07) == 0);

	for (i = 0; i < leftrz; i++) {
		buf[i] = deadbeef[i % 4];
	}

	for (i = 0; i < rightrz; i++) {
		buf[i + size + leftrz] = c0ffee[i % 4];
	}
#else
	(void)base;
	(void)size;
	(void)leftrz;
	(void)rightrz;
#endif
}

void NOINLINE
kasan_check_range(const void *x, size_t sz, unsigned access_type)
{
	vm_offset_t invalid;

	if (kasan_in_unsafe()) {
		return;
	}

	if (kasan_range_poisoned((vm_offset_t)x, sz, &invalid)) {
		if (kasan_is_blacklisted(access_type)) {
			return;
		}
		kasan_crash_report(invalid, sz, access_type);
		/* NOTREACHED */
	}
}

/*
 * Check that [base, base+sz) has shadow value `shadow'
 * If not, report a KASan-violation on `addr'
 */
static void
kasan_assert_shadow(vm_address_t base, vm_size_t sz, vm_address_t addr, uint8_t shadow)
{
	sz -= 8 - (base % 8);
	base += 8 - (base % 8);

	vm_address_t end = base + sz;

	while (base < end) {
		uint8_t *sh = SHADOW_FOR_ADDRESS(base);
		if (*sh != shadow) {
			__asan_report_load1(addr);
		}
		base += 8;
	}
}

/*
 *
 * KASAN violation reporting
 *
 */

static const char *
access_type_str(unsigned type)
{
	if (type & TYPE_LOAD_ALL) {
		return "load";
	} else if (type & TYPE_STORE_ALL) {
		return "store";
	} else if (type & TYPE_FREE) {
		return "free";
	} else {
		return "access";
	}
}

static const char *shadow_strings[] = {
	[ASAN_VALID] =          "VALID",
	[ASAN_PARTIAL1] =       "PARTIAL1",
	[ASAN_PARTIAL2] =       "PARTIAL2",
	[ASAN_PARTIAL3] =       "PARTIAL3",
	[ASAN_PARTIAL4] =       "PARTIAL4",
	[ASAN_PARTIAL5] =       "PARTIAL5",
	[ASAN_PARTIAL6] =       "PARTIAL6",
	[ASAN_PARTIAL7] =       "PARTIAL7",
	[ASAN_STACK_RZ] =       "<invalid>",
	[ASAN_STACK_LEFT_RZ] =  "STACK_LEFT_RZ",
	[ASAN_STACK_MID_RZ] =   "STACK_MID_RZ",
	[ASAN_STACK_RIGHT_RZ] = "STACK_RIGHT_RZ",
	[ASAN_STACK_FREED] =    "STACK_FREED",
	[ASAN_GLOBAL_RZ] =      "GLOBAL_RZ",
	[ASAN_HEAP_RZ] =        "<invalid>",
	[ASAN_HEAP_LEFT_RZ] =   "HEAP_LEFT_RZ",
	[ASAN_HEAP_RIGHT_RZ] =  "HEAP_RIGHT_RZ",
	[ASAN_HEAP_FREED] =     "HEAP_FREED",
	[0xff] =                "<invalid>",
};

#define CRASH_CONTEXT_BEFORE 5
#define CRASH_CONTEXT_AFTER  5

static size_t
kasan_shadow_crashlog(uptr p, char *buf, size_t len)
{
	int i,j;
	size_t l = 0;
	int before = CRASH_CONTEXT_BEFORE;
	int after = CRASH_CONTEXT_AFTER;

	uptr shadow = (uptr)SHADOW_FOR_ADDRESS(p);
	uptr shadow_p = shadow;

	/* rewind to start of context block */
	shadow &= ~((uptr)0xf);
	shadow -= 16 * before;

	for (i = 0; i < 1 + before + after; i++, shadow += 16) {
		if (vm_map_round_page(shadow, PAGE_MASK) != vm_map_round_page(shadow_p, PAGE_MASK)) {
			/* don't cross a page boundary, in case the shadow is unmapped */
			/* XXX: ideally we check instead of ignore */
			continue;
		}

		l += snprintf(buf+l, len-l, " %#16lx: ", shadow);

		for (j = 0; j < 16; j++) {
			uint8_t *x = (uint8_t *)(shadow + j);
			l += snprintf(buf+l, len-l, "%02x ", (unsigned)*x);
		}
		l += snprintf(buf+l, len-l, "\n");
	}

	l += snprintf(buf+l, len-l, "\n");
	return l;
}

static void NOINLINE
kasan_crash_report(uptr p, uptr width, unsigned access_type)
{
	const size_t len = 4096;
	static char buf[len];
	size_t l = 0;

	uint8_t *shadow_ptr = SHADOW_FOR_ADDRESS(p);
	uint8_t shadow_type = *shadow_ptr;
	const char *shadow_str = shadow_strings[shadow_type];

	kasan_handle_test();

	buf[0] = '\0';
	l += snprintf(buf+l, len-l,
			"KASan: invalid %lu-byte %s @ %#lx [%s]\n"
			"Shadow %#02x @ %#lx\n\n",
			width, access_type_str(access_type), p, shadow_str,
			(unsigned)shadow_type, (unsigned long)shadow_ptr);

	l += kasan_shadow_crashlog(p, buf+l, len-l);

	panic("%s", buf);
}

#define REPORT_DECLARE(n) \
	void __asan_report_load##n(uptr p)  { kasan_crash_report(p, n, TYPE_LOAD); } \
	void __asan_report_store##n(uptr p) { kasan_crash_report(p, n, TYPE_STORE); } \
	void __asan_report_exp_load##n(uptr, int32_t); \
	void __asan_report_exp_store##n(uptr, int32_t); \
	void __asan_report_exp_load##n(uptr __unused p, int32_t __unused e) { ABI_UNSUPPORTED; } \
	void __asan_report_exp_store##n(uptr __unused p, int32_t __unused e) { ABI_UNSUPPORTED; }

REPORT_DECLARE(1)
REPORT_DECLARE(2)
REPORT_DECLARE(4)
REPORT_DECLARE(8)
REPORT_DECLARE(16)

void __asan_report_load_n(uptr p, unsigned long sz)  { kasan_crash_report(p, sz, TYPE_LOAD); }
void __asan_report_store_n(uptr p, unsigned long sz) { kasan_crash_report(p, sz, TYPE_STORE); }

/* unpoison the current stack */
/* XXX: as an optimization, we could unpoison only up to the current stack depth */
void NOINLINE
kasan_unpoison_curstack(void)
{
	kasan_unpoison_stack(ml_stack_base(), ml_stack_size());
}

void NOINLINE
__asan_handle_no_return(void)
{
	kasan_unpoison_curstack();
	kasan_unpoison_fakestack(current_thread());
}

bool NOINLINE
kasan_range_poisoned(vm_offset_t base, vm_size_t size, vm_offset_t *first_invalid)
{
	uint8_t *shadow;
	vm_size_t i;

	if (!kasan_initialized || !kasan_enabled) {
		return false;
	}

	size += base & 0x07;
	base &= ~(vm_offset_t)0x07;

	shadow = SHADOW_FOR_ADDRESS(base);
	vm_size_t limit = (size + 7) / 8;

	/* XXX: to make debugging easier, catch unmapped shadow here */

	for (i = 0; i < limit; i++, size -= 8) {
		assert(size > 0);
		uint8_t s = shadow[i];
		if (s == 0 || (size < 8 && s >= size && s <= 7)) {
			/* valid */
		} else {
			goto fail;
		}
	}

	return false;

 fail:
	if (first_invalid) {
		/* XXX: calculate the exact first byte that failed */
		*first_invalid = base + i*8;
	}
	return true;
}

static void NOINLINE
kasan_init_globals(vm_offset_t base, vm_size_t size)
{
	struct asan_global *glob = (struct asan_global *)base;
	struct asan_global *glob_end = (struct asan_global *)(base + size);
	for (; glob < glob_end; glob++) {
		/* handle one global */
		kasan_poison(glob->addr, glob->size, 0, glob->size_with_redzone - glob->size, ASAN_GLOBAL_RZ);
	}
}

void NOINLINE
kasan_load_kext(vm_offset_t base, vm_size_t __unused size, const void *bundleid)
{
	unsigned long sectsz;
	void *sect;

	/* find the kasan globals segment/section */
	sect = getsectdatafromheader((void *)base, KASAN_GLOBAL_SEGNAME, KASAN_GLOBAL_SECTNAME, &sectsz);
	if (sect) {
		kasan_init_globals((vm_address_t)sect, (vm_size_t)sectsz);
		kexts_loaded++;
	}

#if KASAN_DYNAMIC_BLACKLIST
	kasan_dybl_load_kext(base, bundleid);
#endif
}

void NOINLINE
kasan_unload_kext(vm_offset_t base, vm_size_t size)
{
	unsigned long sectsz;
	void *sect;

	/* find the kasan globals segment/section */
	sect = getsectdatafromheader((void *)base, KASAN_GLOBAL_SEGNAME, KASAN_GLOBAL_SECTNAME, &sectsz);
	if (sect) {
		kasan_unpoison((void *)base, size);
		kexts_loaded--;
	}

#if KASAN_DYNAMIC_BLACKLIST
	kasan_dybl_unload_kext(base);
#endif
}

void NOINLINE
kasan_disable(void)
{
	__asan_option_detect_stack_use_after_return = 0;
	kasan_enabled = 0;
}

static void NOINLINE
kasan_init_xnu_globals(void)
{
	const char *seg = KASAN_GLOBAL_SEGNAME;
	const char *sect = KASAN_GLOBAL_SECTNAME;
	unsigned long _size;
	vm_offset_t globals;
	vm_size_t size;
	kernel_mach_header_t *header = (kernel_mach_header_t *)&_mh_execute_header;

	if (!header) {
		printf("KASAN: failed to find kernel mach header\n");
		printf("KASAN: redzones for globals not poisoned\n");
		return;
	}

	globals = (vm_offset_t)getsectdatafromheader(header, seg, sect, &_size);
	if (!globals) {
		printf("KASAN: failed to find segment %s section %s\n", seg, sect);
		printf("KASAN: redzones for globals not poisoned\n");
		return;
	}
	size = (vm_size_t)_size;

	printf("KASAN: found (%s,%s) at %#lx + %lu\n", seg, sect, globals, size);
	printf("KASAN: poisoning redzone for %lu globals\n", size / sizeof(struct asan_global));

	kasan_init_globals(globals, size);
}

void NOINLINE
kasan_late_init(void)
{
	kasan_init_fakestack();
	kasan_init_xnu_globals();

#if KASAN_DYNAMIC_BLACKLIST
	kasan_init_dybl();
#endif
}

void NOINLINE
kasan_notify_stolen(vm_offset_t top)
{
	kasan_map_shadow(kernel_vtop, top - kernel_vtop, false);
}

static void NOINLINE
kasan_debug_touch_mappings(vm_offset_t base, vm_size_t sz)
{
#if KASAN_DEBUG
	vm_size_t i;
	uint8_t tmp1, tmp2;

	/* Hit every byte in the shadow map. Don't write due to the zero mappings. */
	for (i = 0; i < sz; i += sizeof(uint64_t)) {
		vm_offset_t addr = base + i;
		uint8_t *x = SHADOW_FOR_ADDRESS(addr);
		tmp1 = *x;
		asm volatile("" ::: "memory");
		tmp2 = *x;
		asm volatile("" ::: "memory");
		assert(tmp1 == tmp2);
	}
#else
	(void)base;
	(void)sz;
#endif
}

void NOINLINE
kasan_init(void)
{
	simple_lock_init(&kasan_vm_lock, 0);

	/* Map all of the kernel text and data */
	kasan_map_shadow(kernel_vbase, kernel_vtop - kernel_vbase, false);

	kasan_arch_init();

	kasan_initialized = 1;
	kasan_enabled = 1;
}

static void NOINLINE
kasan_notify_address_internal(vm_offset_t address, vm_size_t size, bool is_zero)
{
	assert(address < VM_MAX_KERNEL_ADDRESS);

	if (!kasan_initialized || !kasan_enabled) {
		return;
	}

	if (address < VM_MIN_KERNEL_AND_KEXT_ADDRESS) {
		/* only map kernel addresses */
		return;
	}

	if (!size) {
		/* nothing to map */
		return;
	}

	boolean_t flags;
	kasan_lock(&flags);
	kasan_map_shadow(address, size, is_zero);
	kasan_unlock(flags);
	kasan_debug_touch_mappings(address, size);
}

void
kasan_notify_address(vm_offset_t address, vm_size_t size)
{
	kasan_notify_address_internal(address, size, false);
}

/*
 * Allocate read-only, all-zeros shadow for memory that can never be poisoned
 */
void
kasan_notify_address_nopoison(vm_offset_t address, vm_size_t size)
{
	kasan_notify_address_internal(address, size, true);
}

/*
 *
 * allocator hooks
 *
 */

struct kasan_alloc_header {
	uint32_t magic;
	uint32_t alloc_size;
	uint32_t user_size;
	struct {
		uint32_t left_rz : 28;
		uint32_t frames  : 4;
	};
};
_Static_assert(sizeof(struct kasan_alloc_header) <= KASAN_GUARD_SIZE, "kasan alloc header exceeds guard size");

struct kasan_alloc_footer {
	uint32_t backtrace[0];
};
_Static_assert(sizeof(struct kasan_alloc_footer) <= KASAN_GUARD_SIZE, "kasan alloc footer exceeds guard size");

#define MAGIC_XOR ((uint32_t)0xA110C8ED)
static uint32_t
magic_for_addr(vm_offset_t addr)
{
	return (uint32_t)addr ^ MAGIC_XOR;
}

static struct kasan_alloc_header *
header_for_user_addr(vm_offset_t addr)
{
	return (void *)(addr - sizeof(struct kasan_alloc_header));
}

static struct kasan_alloc_footer *
footer_for_user_addr(vm_offset_t addr, vm_size_t *size)
{
	struct kasan_alloc_header *h = header_for_user_addr(addr);
	vm_size_t rightrz = h->alloc_size - h->user_size - h->left_rz;
	*size = rightrz;
	return (void *)(addr + h->user_size);
}

/*
 * size: user-requested allocation size
 * ret:  minimum size for the real allocation
 */
vm_size_t
kasan_alloc_resize(vm_size_t size)
{
	vm_size_t tmp;
	if (os_add_overflow(size, 4 * PAGE_SIZE, &tmp)) {
		panic("allocation size overflow (%lu)", size);
	}

	/* add left and right redzones */
	size += KASAN_GUARD_PAD;

	/* ensure the final allocation is an 8-byte multiple */
	size += 8 - (size % 8);

	return size;
}

extern vm_offset_t vm_kernel_slid_base;

static vm_size_t
kasan_alloc_bt(uint32_t *ptr, vm_size_t sz, vm_size_t skip)
{
	uintptr_t buf[BACKTRACE_MAXFRAMES];
	uintptr_t *bt = buf;

	sz /= sizeof(uint32_t);
	vm_size_t frames = sz;

	if (frames > 0) {
		frames = min(frames + skip, BACKTRACE_MAXFRAMES);
		frames = backtrace(bt, frames);

		while (frames > sz && skip > 0) {
			bt++;
			frames--;
			skip--;
		}

		/* only store the offset from kernel base, and cram that into 32
		 * bits */
		for (vm_size_t i = 0; i < frames; i++) {
			ptr[i] = (uint32_t)(bt[i] - vm_kernel_slid_base);
		}
	}
	return frames;
}

/*
 * addr: base address of full allocation (including redzones)
 * size: total size of allocation (include redzones)
 * req:  user-requested allocation size
 * lrz:  size of the left redzone in bytes
 * ret:  address of usable allocation
 */
vm_address_t
kasan_alloc(vm_offset_t addr, vm_size_t size, vm_size_t req, vm_size_t leftrz)
{
	if (!addr) {
		return 0;
	}
	assert(size > 0);
	assert((addr % 8) == 0);
	assert((size % 8) == 0);

	vm_size_t rightrz = size - req - leftrz;

	kasan_poison(addr, req, leftrz, rightrz, ASAN_HEAP_RZ);
	kasan_rz_clobber(addr, req, leftrz, rightrz);

	addr += leftrz;

	/* stash the allocation sizes in the left redzone */
	struct kasan_alloc_header *h = header_for_user_addr(addr);
	h->magic = magic_for_addr(addr);
	h->left_rz = leftrz;
	h->alloc_size = size;
	h->user_size = req;

	/* ... and a backtrace in the right redzone */
	vm_size_t fsize;
	struct kasan_alloc_footer *f = footer_for_user_addr(addr, &fsize);
	h->frames = kasan_alloc_bt(f->backtrace, fsize, 2);

	return addr;
}

/*
 * addr: user pointer
 * size: returns full original allocation size
 * ret:  original allocation ptr
 */
vm_address_t
kasan_dealloc(vm_offset_t addr, vm_size_t *size)
{
	assert(size && addr);
	struct kasan_alloc_header *h = header_for_user_addr(addr);
	if (h->magic != magic_for_addr(addr)) {
		/* no point blacklisting here - this is fatal */
		kasan_crash_report(addr, *size, TYPE_FREE);
	}
	*size = h->alloc_size;
	return addr - h->left_rz;
}

/*
 * return the original user-requested allocation size
 * addr: user alloc pointer
 */
vm_size_t
kasan_user_size(vm_offset_t addr)
{
	struct kasan_alloc_header *h = header_for_user_addr(addr);
	assert(h->magic == magic_for_addr(addr));
	return h->user_size;
}

/*
 * Verify that `addr' (user pointer) is a valid allocation of `type'
 */
void
kasan_check_free(vm_offset_t addr, vm_size_t size, unsigned heap_type)
{
	struct kasan_alloc_header *h = header_for_user_addr(addr);

	/* map heap type to an internal access type */
	unsigned type;
	if (heap_type == KASAN_HEAP_KALLOC) {
		type = TYPE_KFREE;
	} else if (heap_type == KASAN_HEAP_ZALLOC) {
		type = TYPE_ZFREE;
	} else if (heap_type == KASAN_HEAP_FAKESTACK) {
		type = TYPE_FSFREE;
	}

	/* check the magic matches */
	if (h->magic != magic_for_addr(addr)) {
		if (kasan_is_blacklisted(type)) {
			return;
		}
		kasan_crash_report(addr, size, type);
	}

	/* check the freed size matches what we recorded at alloc time */
	if (h->user_size != size) {
		if (kasan_is_blacklisted(type)) {
			return;
		}
		kasan_crash_report(addr, size, type);
	}

	vm_size_t rightrz_sz = h->alloc_size - h->left_rz - h->user_size;

	/* Check that the redzones are valid */
	kasan_assert_shadow(addr - h->left_rz, h->left_rz, addr, ASAN_HEAP_LEFT_RZ);
	kasan_assert_shadow(addr + h->user_size, rightrz_sz, addr, ASAN_HEAP_RIGHT_RZ);

	/* Check the allocated range is not poisoned */
	kasan_check_range((void *)addr, size, type);
}

/*
 *
 * Quarantine
 *
 */

struct freelist_entry {
	uint32_t magic;
	uint32_t checksum;
	STAILQ_ENTRY(freelist_entry) list;
	union {
		struct {
			vm_size_t size      : 28;
			vm_size_t user_size : 28;
			vm_size_t frames    : 4; /* number of frames in backtrace */
			vm_size_t __unused  : 4;
		};
		uint64_t bits;
	};
	zone_t zone;
	uint32_t backtrace[];
};
_Static_assert(sizeof(struct freelist_entry) <= KASAN_GUARD_PAD, "kasan freelist header exceeds padded size");

#define FREELIST_MAGIC_XOR ((uint32_t)0xF23333D)
static uint32_t
freelist_magic(vm_offset_t addr)
{
	return (uint32_t)addr ^ FREELIST_MAGIC_XOR;
}

struct quarantine {
	STAILQ_HEAD(freelist_head, freelist_entry) freelist;
	unsigned long entries;
	unsigned long max_entries;
	vm_size_t size;
	vm_size_t max_size;
};

struct quarantine quarantines[] = {
	{ STAILQ_HEAD_INITIALIZER((quarantines[KASAN_HEAP_ZALLOC].freelist)),    0, QUARANTINE_ENTRIES, 0, QUARANTINE_MAXSIZE },
	{ STAILQ_HEAD_INITIALIZER((quarantines[KASAN_HEAP_KALLOC].freelist)),    0, QUARANTINE_ENTRIES, 0, QUARANTINE_MAXSIZE },
	{ STAILQ_HEAD_INITIALIZER((quarantines[KASAN_HEAP_FAKESTACK].freelist)), 0, QUARANTINE_ENTRIES, 0, QUARANTINE_MAXSIZE }
};

/*
 * addr, sizep: pointer/size of full allocation including redzone
 */
void NOINLINE
kasan_free_internal(void **addrp, vm_size_t *sizep, int type,
                    zone_t *zone, vm_size_t user_size, int locked,
                    bool doquarantine)
{
	vm_size_t size = *sizep;
	vm_offset_t addr = *(vm_offset_t *)addrp;

	assert(type >= 0 && type < KASAN_HEAP_TYPES);
	if (type == KASAN_HEAP_KALLOC) {
		/* zero-size kalloc allocations are allowed */
		assert(!zone);
	} else if (type == KASAN_HEAP_ZALLOC) {
		assert(zone && user_size);
	} else if (type == KASAN_HEAP_FAKESTACK) {
		assert(zone && user_size);
	}

	/* clobber the entire freed region */
	kasan_rz_clobber(addr, 0, size, 0);

	if (!doquarantine || !quarantine_enabled) {
		goto free_current;
	}

	/* poison the entire freed region */
	uint8_t flags = (type == KASAN_HEAP_FAKESTACK) ? ASAN_STACK_FREED : ASAN_HEAP_FREED;
	kasan_poison(addr, 0, size, 0, flags);

	struct freelist_entry *fle, *tofree = NULL;
	struct quarantine *q = &quarantines[type];
	assert(size >= sizeof(struct freelist_entry));

	/* create a new freelist entry */
	fle = (struct freelist_entry *)addr;
	fle->magic = freelist_magic((vm_offset_t)fle);
	fle->size = size;
	fle->user_size = user_size;
	fle->frames = 0;
	fle->zone = ZONE_NULL;
	if (zone) {
		fle->zone = *zone;
	}
	if (type != KASAN_HEAP_FAKESTACK) {
		fle->frames = kasan_alloc_bt(fle->backtrace, fle->size - sizeof(struct freelist_entry), 3);
	}

	boolean_t flg;
	if (!locked) {
		kasan_lock(&flg);
	}

	if (q->size + size > q->max_size) {
		/*
		 * Adding this entry would put us over the max quarantine size. Free the
		 * larger of the current object and the quarantine head object.
		 */
		tofree = STAILQ_FIRST(&q->freelist);
		if (fle->size > tofree->size) {
			goto free_current_locked;
		}
	}

	STAILQ_INSERT_TAIL(&q->freelist, fle, list);
	q->entries++;
	q->size += size;

	/* free the oldest entry, if necessary */
	if (tofree || q->entries > q->max_entries) {
		tofree = STAILQ_FIRST(&q->freelist);
		STAILQ_REMOVE_HEAD(&q->freelist, list);

		assert(q->entries > 0 && q->size >= tofree->size);
		q->entries--;
		q->size -= tofree->size;

		if (type != KASAN_HEAP_KALLOC) {
			assert((vm_offset_t)zone >= VM_MIN_KERNEL_AND_KEXT_ADDRESS &&
			       (vm_offset_t)zone <= VM_MAX_KERNEL_ADDRESS);
			*zone = tofree->zone;
		}

		size = tofree->size;
		addr = (vm_offset_t)tofree;
		if (tofree->magic != freelist_magic(addr)) {
			kasan_crash_report(addr, size, TYPE_FREE);
		}

		/* clobber the quarantine header */
		kasan_rz_clobber(addr, 0, sizeof(struct freelist_entry), 0);

	} else {
		/* quarantine is not full - don't really free anything */
		addr = 0;
	}

 free_current_locked:
	if (!locked) {
		kasan_unlock(flg);
	}

 free_current:
	*addrp = (void *)addr;
	if (addr) {
		kasan_unpoison((void *)addr, size);
		*sizep = size;
	}
}

void NOINLINE
kasan_free(void **addrp, vm_size_t *sizep, int type, zone_t *zone,
           vm_size_t user_size, bool quarantine)
{
	kasan_free_internal(addrp, sizep, type, zone, user_size, 0, quarantine);
}

uptr
__asan_load_cxx_array_cookie(uptr *p)
{
	uint8_t *shadow = SHADOW_FOR_ADDRESS((uptr)p);
	if (*shadow == ASAN_ARRAY_COOKIE) {
		return *p;
	} else if (*shadow == ASAN_HEAP_FREED) {
		return 0;
	} else {
		return *p;
	}
}

void
__asan_poison_cxx_array_cookie(uptr p)
{
	uint8_t *shadow = SHADOW_FOR_ADDRESS(p);
	*shadow = ASAN_ARRAY_COOKIE;
}

#define ACCESS_CHECK_DECLARE(type, sz, access_type) \
	void __asan_##type##sz(uptr addr) { \
		kasan_check_range((const void *)addr, sz, access_type); \
	} \
	void __asan_exp_##type##sz(uptr, int32_t); \
	void __asan_exp_##type##sz(uptr __unused addr, int32_t __unused e) { ABI_UNSUPPORTED; }

ACCESS_CHECK_DECLARE(load,  1,  TYPE_LOAD);
ACCESS_CHECK_DECLARE(load,  2,  TYPE_LOAD);
ACCESS_CHECK_DECLARE(load,  4,  TYPE_LOAD);
ACCESS_CHECK_DECLARE(load,  8,  TYPE_LOAD);
ACCESS_CHECK_DECLARE(load,  16, TYPE_LOAD);
ACCESS_CHECK_DECLARE(store, 1,  TYPE_STORE);
ACCESS_CHECK_DECLARE(store, 2,  TYPE_STORE);
ACCESS_CHECK_DECLARE(store, 4,  TYPE_STORE);
ACCESS_CHECK_DECLARE(store, 8,  TYPE_STORE);
ACCESS_CHECK_DECLARE(store, 16, TYPE_STORE);

void
__asan_loadN(uptr addr, size_t sz)
{
	kasan_check_range((const void *)addr, sz, TYPE_LOAD);
}

void
__asan_storeN(uptr addr, size_t sz)
{
	kasan_check_range((const void *)addr, sz, TYPE_STORE);
}

void __asan_exp_loadN(uptr, size_t, int32_t);
void __asan_exp_storeN(uptr, size_t, int32_t);
void __asan_exp_loadN(uptr __unused addr, size_t __unused sz, int32_t __unused e) { ABI_UNSUPPORTED; }
void __asan_exp_storeN(uptr __unused addr, size_t __unused sz, int32_t __unused e) { ABI_UNSUPPORTED; }

void __asan_report_exp_load_n(uptr, unsigned long, int32_t);
void __asan_report_exp_store_n(uptr, unsigned long, int32_t);
void __asan_report_exp_load_n(uptr __unused p, unsigned long __unused sz, int32_t __unused e) { ABI_UNSUPPORTED; }
void __asan_report_exp_store_n(uptr __unused p, unsigned long __unused sz, int32_t __unused e) { ABI_UNSUPPORTED; }

static void
kasan_set_shadow(uptr addr, size_t sz, uint8_t val)
{
	__nosan_memset((void *)addr, val, sz);
}

#define SET_SHADOW_DECLARE(val) \
	void __asan_set_shadow_##val(uptr addr, size_t sz) { \
		kasan_set_shadow(addr, sz, 0x##val); \
	}

SET_SHADOW_DECLARE(00)
SET_SHADOW_DECLARE(f1)
SET_SHADOW_DECLARE(f2)
SET_SHADOW_DECLARE(f3)
SET_SHADOW_DECLARE(f5)
SET_SHADOW_DECLARE(f8)

/*
 * XXX: implement these
 */

void __asan_alloca_poison(uptr addr, uptr size)
{
	(void)addr;
	(void)size;
}

void __asan_allocas_unpoison(uptr top, uptr bottom)
{
	(void)top;
	(void)bottom;
}

void
__sanitizer_ptr_sub(uptr a, uptr b)
{
	(void)a;
	(void)b;
}

void
__sanitizer_ptr_cmp(uptr a, uptr b)
{
	(void)a;
	(void)b;
}

void
__asan_poison_stack_memory(uptr addr, size_t size)
{
	(void)addr;
	(void)size;
}

void
__asan_unpoison_stack_memory(uptr addr, size_t size)
{
	(void)addr;
	(void)size;
}

void
__sanitizer_annotate_contiguous_container(const void *beg,
		const void *end,
		const void *old_mid,
		const void *new_mid)
{
	(void)beg;
	(void)end;
	(void)old_mid;
	(void)new_mid;
}

/*
 */

void
__asan_init(void)
{
}

#define VERSION_DECLARE(v) \
	void __asan_version_mismatch_check_##v(void); \
	void __asan_version_mismatch_check_##v(void) {}

VERSION_DECLARE(v8)
VERSION_DECLARE(apple_802)
VERSION_DECLARE(apple_900)

void
__asan_register_globals(uptr __unused a, uptr __unused b)
{
	ABI_UNSUPPORTED;
}

void
__asan_unregister_globals(uptr __unused a, uptr __unused b)
{
	ABI_UNSUPPORTED;
}

void
__asan_register_image_globals(uptr __unused ptr)
{
}

void
__asan_unregister_image_globals(uptr __unused ptr)
{
}

void
__asan_init_v5(void)
{
}

void
__asan_before_dynamic_init(uptr __unused arg)
{
}

void
__asan_after_dynamic_init(void)
{
}


/*
 *
 * SYSCTL
 *
 */

static int
sysctl_kasan_test(__unused struct sysctl_oid *oidp, __unused void *arg1, int arg2, struct sysctl_req *req)
{
	int mask = 0;
	int ch;
	int err;
	err = sysctl_io_number(req, 0, sizeof(int), &mask, &ch);

	if (!err && mask) {
		kasan_test(mask, arg2);
	}

	return err;
}

SYSCTL_DECL(kasan);
SYSCTL_NODE(_kern, OID_AUTO, kasan, CTLFLAG_RW | CTLFLAG_LOCKED, 0, "");

SYSCTL_COMPAT_INT(_kern_kasan, OID_AUTO, available, CTLFLAG_RD, NULL, KASAN, "");
SYSCTL_INT(_kern_kasan, OID_AUTO, enabled, CTLFLAG_RD, &kasan_enabled, 0, "");
SYSCTL_INT(_kern_kasan, OID_AUTO, quarantine, CTLFLAG_RW, &quarantine_enabled, 0, "");
SYSCTL_LONG(_kern_kasan, OID_AUTO, memused, CTLFLAG_RD, &shadow_pages_used, "");
SYSCTL_LONG(_kern_kasan, OID_AUTO, memtotal, CTLFLAG_RD, &shadow_pages_total, "");
SYSCTL_LONG(_kern_kasan, OID_AUTO, kexts, CTLFLAG_RD, &kexts_loaded, "");

SYSCTL_COMPAT_INT(_kern_kasan, OID_AUTO, debug,         CTLFLAG_RD, NULL, KASAN_DEBUG, "");
SYSCTL_COMPAT_INT(_kern_kasan, OID_AUTO, zalloc,        CTLFLAG_RD, NULL, KASAN_ZALLOC, "");
SYSCTL_COMPAT_INT(_kern_kasan, OID_AUTO, kalloc,        CTLFLAG_RD, NULL, KASAN_KALLOC, "");
SYSCTL_COMPAT_INT(_kern_kasan, OID_AUTO, fakestack,     CTLFLAG_RD, NULL, FAKESTACK, "");
SYSCTL_COMPAT_INT(_kern_kasan, OID_AUTO, dynamicbl,     CTLFLAG_RD, NULL, KASAN_DYNAMIC_BLACKLIST, "");
SYSCTL_COMPAT_INT(_kern_kasan, OID_AUTO, memintrinsics, CTLFLAG_RD, NULL, MEMINTRINSICS, "");

SYSCTL_PROC(_kern_kasan, OID_AUTO, test,
		CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
		0, 0, sysctl_kasan_test, "I", "");

SYSCTL_PROC(_kern_kasan, OID_AUTO, fail,
		CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
		0, 1, sysctl_kasan_test, "I", "");