[apple/xnu.git] / san / kasan.c

/*
 * 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>

const uintptr_t __asan_shadow_memory_dynamic_address = KASAN_SHIFT;

static unsigned kexts_loaded;
unsigned shadow_pages_total;
unsigned shadow_pages_used;

vm_offset_t kernel_vbase;
vm_offset_t kernel_vtop;

static unsigned kasan_enabled;
static unsigned quarantine_enabled;
static unsigned enabled_checks = TYPE_ALL; /* bitmask of enabled checks */
static unsigned report_ignored;            /* issue non-fatal report for disabled/blacklisted checks */
static unsigned free_yield = 0;            /* ms yield after each free */

/* forward decls */
static void kasan_crash_report(uptr p, uptr width, access_t access, violation_t reason);
static void kasan_log_report(uptr p, uptr width, access_t access, violation_t reason);

/* imported osfmk functions */
extern vm_offset_t ml_stack_base(void);
extern vm_size_t ml_stack_size(void);

/*
 * unused: expected to be called, but (currently) does nothing
 */
#define UNUSED_ABI(func, ...) \
        _Pragma("clang diagnostic push") \
        _Pragma("clang diagnostic ignored \"-Wunused-parameter\"") \
        void func(__VA_ARGS__); \
        void func(__VA_ARGS__) {}; \
        _Pragma("clang diagnostic pop") \

static const size_t BACKTRACE_BITS       = 4;
static const size_t BACKTRACE_MAXFRAMES  = (1UL << BACKTRACE_BITS) - 1;

decl_simple_lock_data(, kasan_vm_lock);
static thread_t kasan_lock_holder;

/*
 * 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, LCK_GRP_NULL);
        kasan_lock_holder = current_thread();
}

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

/* Return true if 'thread' holds the kasan lock. Only safe if 'thread' == current
 * thread */
bool
kasan_lock_held(thread_t thread)
{
        return thread && thread == kasan_lock_holder;
}

static inline bool
kasan_check_enabled(access_t access)
{
        return kasan_enabled && (enabled_checks & access) && !kasan_is_blacklisted(access);
}

static inline bool
kasan_poison_active(uint8_t flags)
{
        switch (flags) {
        case ASAN_GLOBAL_RZ:
                return kasan_check_enabled(TYPE_POISON_GLOBAL);
        case ASAN_HEAP_RZ:
        case ASAN_HEAP_LEFT_RZ:
        case ASAN_HEAP_RIGHT_RZ:
        case ASAN_HEAP_FREED:
                return kasan_check_enabled(TYPE_POISON_HEAP);
        default:
                return true;
        };
}

/*
 * 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_poison_active(flags)) {
                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; /* XXX: should not be necessary */
        }
        if (partial && (i < total)) {
                shadow[i] = partial;
                i++;
        }
        for (; i < total; i++) {
                shadow[i] = r_flags;
        }
}

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);

        /* align base and size to 8 bytes */
        vm_offset_t align = base & 0x7;
        base -= align;
        size += align;
        size = (size + 7) & ~0x7;

        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
}

/*
 * Report a violation that may be disabled and/or blacklisted. This can only be
 * called for dynamic checks (i.e. where the fault is recoverable). Use
 * kasan_crash_report() for static (unrecoverable) violations.
 *
 * access: what we were trying to do when the violation occured
 * reason: what failed about the access
 */
static void
kasan_violation(uintptr_t addr, size_t size, access_t access, violation_t reason)
{
        assert(__builtin_popcount(access) == 1);
        if (!kasan_check_enabled(access)) {
                if (report_ignored) {
                        kasan_log_report(addr, size, access, reason);
                }
                return;
        }
        kasan_crash_report(addr, size, access, reason);
}

void NOINLINE
kasan_check_range(const void *x, size_t sz, access_t access)
{
        uintptr_t invalid;
        uintptr_t ptr = (uintptr_t)x;
        if (kasan_range_poisoned(ptr, sz, &invalid)) {
                size_t remaining = sz - (invalid - ptr);
                kasan_violation(invalid, remaining, access, 0);
        }
}

/*
 * Return true if [base, base+sz) is unpoisoned or has given shadow value.
 */
bool
kasan_check_shadow(vm_address_t base, vm_size_t sz, 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 && *sh != shadow) {
                        return false;
                }
                base += 8;
        }
        return true;
}

/*
 *
 * KASAN violation reporting
 *
 */

static const char *
access_str(access_t type)
{
        if (type & TYPE_READ) {
                return "load from";
        } else if (type & TYPE_WRITE) {
                return "store to";
        } else if (type & TYPE_FREE) {
                return "free of";
        } else {
                return "access of";
        }
}

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_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_STACK_OOSCOPE] =  "STACK_OOSCOPE",
        [ASAN_GLOBAL_RZ] =      "GLOBAL_RZ",
        [ASAN_HEAP_LEFT_RZ] =   "HEAP_LEFT_RZ",
        [ASAN_HEAP_RIGHT_RZ] =  "HEAP_RIGHT_RZ",
        [ASAN_HEAP_FREED] =     "HEAP_FREED",
        [0xff] =                NULL
};

#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 n = 0;
        int before = CRASH_CONTEXT_BEFORE;
        int after = CRASH_CONTEXT_AFTER;

        uptr shadow = (uptr)SHADOW_FOR_ADDRESS(p);
        uptr shadow_p = shadow;
        uptr shadow_page = vm_map_round_page(shadow_p, HW_PAGE_MASK);

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

        n += snprintf(buf+n, len-n,
                        " Shadow             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f\n");

        for (i = 0; i < 1 + before + after; i++, shadow += 16) {
                if ((vm_map_round_page(shadow, HW_PAGE_MASK) != shadow_page) && !kasan_is_shadow_mapped(shadow)) {
                        /* avoid unmapped shadow when crossing page boundaries */
                        continue;
                }

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

                char *left = " ";
                char *right;

                for (j = 0; j < 16; j++) {
                        uint8_t *x = (uint8_t *)(shadow + j);

                        right = " ";
                        if ((uptr)x == shadow_p) {
                                left = "[";
                                right = "]";
                        } else if ((uptr)(x + 1) == shadow_p) {
                                right = "";
                        }

                        n += snprintf(buf+n, len-n, "%s%02x%s", left, (unsigned)*x, right);
                        left = "";
                }
                n += snprintf(buf+n, len-n, "\n");
        }

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

static void
kasan_report_internal(uptr p, uptr width, access_t access, violation_t reason, bool dopanic)
{
        const size_t len = 4096;
        static char buf[len];
        size_t n = 0;

        uint8_t *shadow_ptr = SHADOW_FOR_ADDRESS(p);
        uint8_t shadow_type = *shadow_ptr;
        const char *shadow_str = shadow_strings[shadow_type];
        if (!shadow_str) {
                shadow_str = "<invalid>";
        }
        buf[0] = '\0';

        if (reason == REASON_MOD_OOB || reason == REASON_BAD_METADATA) {
                n += snprintf(buf+n, len-n, "KASan: free of corrupted/invalid object %#lx\n", p);
        } else if (reason == REASON_MOD_AFTER_FREE) {
                n += snprintf(buf+n, len-n, "KASan: UaF of quarantined object %#lx\n", p);
        } else {
                n += snprintf(buf+n, len-n, "KASan: invalid %lu-byte %s %#lx [%s]\n",
                                width, access_str(access), p, shadow_str);
        }
        n += kasan_shadow_crashlog(p, buf+n, len-n);

        if (dopanic) {
                panic("%s", buf);
        } else {
                printf("%s", buf);
        }
}

static void NOINLINE OS_NORETURN
kasan_crash_report(uptr p, uptr width, access_t access, violation_t reason)
{
        kasan_handle_test();
        kasan_report_internal(p, width, access, reason, true);
        __builtin_unreachable(); /* we cant handle this returning anyway */
}

static void
kasan_log_report(uptr p, uptr width, access_t access, violation_t reason)
{
        const size_t len = 256;
        char buf[len];
        size_t l = 0;
        uint32_t nframes = 14;
        uintptr_t frames[nframes];
        uintptr_t *bt = frames;

        kasan_report_internal(p, width, access, reason, false);

        /*
         * print a backtrace
         */

        nframes = backtrace_frame(bt, nframes, __builtin_frame_address(0)); /* ignore current frame */

        buf[0] = '\0';
        l += snprintf(buf+l, len-l, "Backtrace: ");
        for (uint32_t i = 0; i < nframes; i++) {
                l += snprintf(buf+l, len-l, "%lx,", VM_KERNEL_UNSLIDE(bt[i]));
        }
        l += snprintf(buf+l, len-l, "\n");

        printf("%s", buf);
}

#define REPORT_DECLARE(n) \
        void OS_NORETURN __asan_report_load##n(uptr p)  { kasan_crash_report(p, n, TYPE_LOAD,  0); } \
        void OS_NORETURN __asan_report_store##n(uptr p) { kasan_crash_report(p, n, TYPE_STORE, 0); } \
        void UNSUPPORTED_API(__asan_report_exp_load##n, uptr a, int32_t b); \
        void UNSUPPORTED_API(__asan_report_exp_store##n, uptr a, int32_t b);

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

void OS_NORETURN __asan_report_load_n(uptr p, unsigned long sz)  { kasan_crash_report(p, sz, TYPE_LOAD,  0); }
void OS_NORETURN __asan_report_store_n(uptr p, unsigned long sz) { kasan_crash_report(p, sz, TYPE_STORE, 0); }

/* unpoison the current stack */
void NOINLINE
kasan_unpoison_curstack(bool whole_stack)
{
        uintptr_t base = ml_stack_base();
        size_t sz = ml_stack_size();
        uintptr_t cur = (uintptr_t)&base;

        if (whole_stack) {
                cur = base;
        }

        if (cur >= base && cur < base + sz) {
                /* unpoison from current stack depth to the top */
                size_t unused = cur - base;
                kasan_unpoison_stack(cur, sz - unused);
        }
}

void NOINLINE
__asan_handle_no_return(void)
{
        kasan_unpoison_curstack(false);

        /*
         * No need to free any fakestack objects because they must stay alive until
         * we drop the real stack, at which point we can drop the entire fakestack
         * anyway.
         */
}

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_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;

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

        /* 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++;
        }
}

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
}

/*
 * Turn off as much as possible for panic path etc. There's no way to turn it back
 * on.
 */
void NOINLINE
kasan_disable(void)
{
        __asan_option_detect_stack_use_after_return = 0;
        fakestack_enabled = 0;
        kasan_enabled = 0;
        quarantine_enabled = 0;
        enabled_checks = 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)
{
#if KASAN_DYNAMIC_BLACKLIST
        kasan_init_dybl();
#endif

        kasan_init_fakestack();
        kasan_init_xnu_globals();
}

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)
{
        unsigned arg;

        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();

        /*
         * handle KASan boot-args
         */

        if (PE_parse_boot_argn("kasan.checks", &arg, sizeof(arg))) {
                enabled_checks = arg;
        }

        if (PE_parse_boot_argn("kasan", &arg, sizeof(arg))) {
                if (arg & KASAN_ARGS_FAKESTACK) {
                        fakestack_enabled = 1;
                }
                if (arg & KASAN_ARGS_REPORTIGNORED) {
                        report_ignored = 1;
                }
                if (arg & KASAN_ARGS_NODYCHECKS) {
                        enabled_checks &= ~TYPE_DYNAMIC;
                }
                if (arg & KASAN_ARGS_NOPOISON_HEAP) {
                        enabled_checks &= ~TYPE_POISON_HEAP;
                }
                if (arg & KASAN_ARGS_NOPOISON_GLOBAL) {
                        enabled_checks &= ~TYPE_POISON_GLOBAL;
                }
        }

        if (PE_parse_boot_argn("kasan.free_yield_ms", &arg, sizeof(arg))) {
                free_yield = arg;
        }

        /* kasan.bl boot-arg handled in kasan_init_dybl() */

        quarantine_enabled = 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_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 {
        uint16_t magic;
        uint16_t crc;
        uint32_t alloc_size;
        uint32_t user_size;
        struct {
                uint32_t left_rz : 32 - BACKTRACE_BITS;
                uint32_t frames  : BACKTRACE_BITS;
        };
};
_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 LIVE_XOR ((uint16_t)0x3a65)
#define FREE_XOR ((uint16_t)0xf233)

static uint16_t
magic_for_addr(vm_offset_t addr, uint16_t magic_xor)
{
        uint16_t magic = addr & 0xFFFF;
        magic ^= (addr >> 16) & 0xFFFF;
        magic ^= (addr >> 32) & 0xFFFF;
        magic ^= (addr >> 48) & 0xFFFF;
        magic ^= magic_xor;
        return magic;
}

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: user address of allocation */
static uint16_t
kasan_alloc_crc(vm_offset_t addr)
{
        struct kasan_alloc_header *h = header_for_user_addr(addr);
        vm_size_t rightrz = h->alloc_size - h->user_size - h->left_rz;

        uint16_t crc_orig = h->crc;
        h->crc = 0;

        uint16_t crc = 0;
        crc = __nosan_crc16(crc, (void *)(addr - h->left_rz), h->left_rz);
        crc = __nosan_crc16(crc, (void *)(addr + h->user_size), rightrz);

        h->crc = crc_orig;

        return crc;
}

/*
 * 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, LIVE_XOR);
        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);

        /* checksum the whole object, minus the user part */
        h->crc = kasan_alloc_crc(addr);

        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);
        *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, LIVE_XOR));
        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 */
        access_t type = heap_type == KASAN_HEAP_KALLOC    ? TYPE_KFREE  :
                        heap_type == KASAN_HEAP_ZALLOC    ? TYPE_ZFREE  :
                        heap_type == KASAN_HEAP_FAKESTACK ? TYPE_FSFREE : 0;

        /* check the magic and crc match */
        if (h->magic != magic_for_addr(addr, LIVE_XOR)) {
                kasan_violation(addr, size, type, REASON_BAD_METADATA);
        }
        if (h->crc != kasan_alloc_crc(addr)) {
                kasan_violation(addr, size, type, REASON_MOD_OOB);
        }

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

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

        /* Check that the redzones are valid */
        if (!kasan_check_shadow(addr - h->left_rz, h->left_rz, ASAN_HEAP_LEFT_RZ) ||
                !kasan_check_shadow(addr + h->user_size, rightrz_sz, ASAN_HEAP_RIGHT_RZ)) {
                kasan_violation(addr, size, type, REASON_BAD_METADATA);
        }

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

/*
 *
 * Quarantine
 *
 */

struct freelist_entry {
        uint16_t magic;
        uint16_t crc;
        STAILQ_ENTRY(freelist_entry) list;
        union {
                struct {
                        vm_size_t size      : 28;
                        vm_size_t user_size : 28;
                        vm_size_t frames    : BACKTRACE_BITS; /* number of frames in backtrace */
                        vm_size_t __unused  : 8 - BACKTRACE_BITS;
                };
                uint64_t bits;
        };
        zone_t zone;
        uint32_t backtrace[];
};
_Static_assert(sizeof(struct freelist_entry) <= KASAN_GUARD_PAD, "kasan freelist header exceeds padded size");

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 }
};

static uint16_t
fle_crc(struct freelist_entry *fle)
{
        return __nosan_crc16(0, &fle->bits, fle->size - offsetof(struct freelist_entry, bits));
}

/*
 * 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 = magic_for_addr((vm_offset_t)fle, FREE_XOR);
        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) {
                /* don't do expensive things on the fakestack path */
                fle->frames = kasan_alloc_bt(fle->backtrace, fle->size - sizeof(struct freelist_entry), 3);
                fle->crc = fle_crc(fle);
        }

        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;

                /* check the magic and crc match */
                if (tofree->magic != magic_for_addr(addr, FREE_XOR)) {
                        kasan_violation(addr, size, TYPE_UAF, REASON_MOD_AFTER_FREE);
                }
                if (type != KASAN_HEAP_FAKESTACK && tofree->crc != fle_crc(tofree)) {
                        kasan_violation(addr, size, TYPE_UAF, REASON_MOD_AFTER_FREE);
                }

                /* clobber the quarantine header */
                __nosan_bzero((void *)addr, sizeof(struct freelist_entry));

        } 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);

        if (free_yield) {
                thread_yield_internal(free_yield);
        }
}

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) \
        void __asan_##type##sz(uptr addr) { \
                kasan_check_range((const void *)addr, sz, access); \
        } \
        void UNSUPPORTED_API(__asan_exp_##type##sz, uptr a, int32_t b);

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);
}

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)


/*
 * Call 'cb' for each contiguous range of the shadow map. This could be more
 * efficient by walking the page table directly.
 */
int
kasan_traverse_mappings(pmap_traverse_callback cb, void *ctx)
{
        uintptr_t shadow_base = (uintptr_t)SHADOW_FOR_ADDRESS(VM_MIN_KERNEL_AND_KEXT_ADDRESS);
        uintptr_t shadow_top = (uintptr_t)SHADOW_FOR_ADDRESS(VM_MAX_KERNEL_ADDRESS);
        shadow_base = vm_map_trunc_page(shadow_base, HW_PAGE_MASK);
        shadow_top = vm_map_round_page(shadow_top, HW_PAGE_MASK);

        uintptr_t start = 0, end = 0;

        for (uintptr_t addr = shadow_base; addr < shadow_top; addr += HW_PAGE_SIZE) {
                if (kasan_is_shadow_mapped(addr)) {
                        if (start == 0) {
                                start = addr;
                        }
                        end = addr + HW_PAGE_SIZE;
                } else if (start && end) {
                        cb(start, end, ctx);
                        start = end = 0;
                }
        }

        if (start && end) {
                cb(start, end, ctx);
        }

        return 0;
}

/*
 * XXX: implement these
 */

UNUSED_ABI(__asan_alloca_poison, uptr addr, uptr size);
UNUSED_ABI(__asan_allocas_unpoison, uptr top, uptr bottom);
UNUSED_ABI(__sanitizer_ptr_sub, uptr a, uptr b);
UNUSED_ABI(__sanitizer_ptr_cmp, uptr a, uptr b);
UNUSED_ABI(__sanitizer_annotate_contiguous_container, const void *a, const void *b, const void *c, const void *d);
UNUSED_ABI(__asan_poison_stack_memory, uptr addr, size_t size);
UNUSED_ABI(__asan_unpoison_stack_memory, uptr a, uptr b);

/*
 * Miscellaneous unimplemented asan ABI
 */

UNUSED_ABI(__asan_init, void);
UNUSED_ABI(__asan_register_image_globals, uptr a);
UNUSED_ABI(__asan_unregister_image_globals, uptr a);
UNUSED_ABI(__asan_before_dynamic_init, uptr a);
UNUSED_ABI(__asan_after_dynamic_init, void);
UNUSED_ABI(__asan_version_mismatch_check_v8, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_802, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_900, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_902, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_1000, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_1001, void);

void UNSUPPORTED_API(__asan_init_v5, void);
void UNSUPPORTED_API(__asan_register_globals, uptr a, uptr b);
void UNSUPPORTED_API(__asan_unregister_globals, uptr a, uptr b);
void UNSUPPORTED_API(__asan_register_elf_globals, uptr a, uptr b, uptr c);
void UNSUPPORTED_API(__asan_unregister_elf_globals, uptr a, uptr b, uptr c);

void UNSUPPORTED_API(__asan_exp_loadN, uptr addr, size_t sz, int32_t e);
void UNSUPPORTED_API(__asan_exp_storeN, uptr addr, size_t sz, int32_t e);
void UNSUPPORTED_API(__asan_report_exp_load_n, uptr addr, unsigned long b, int32_t c);
void UNSUPPORTED_API(__asan_report_exp_store_n, uptr addr, unsigned long b, int32_t c);

/*
 *
 * 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;
}

static int
sysctl_fakestack_enable(__unused struct sysctl_oid *oidp, __unused void *arg1, int __unused arg2, struct sysctl_req *req)
{
        int ch, err, val;

        err = sysctl_io_number(req, fakestack_enabled, sizeof(fakestack_enabled), &val, &ch);
        if (err == 0 && ch) {
                fakestack_enabled = !!val;
                __asan_option_detect_stack_use_after_return = !!val;
        }

        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_UINT(_kern_kasan, OID_AUTO, enabled, CTLFLAG_RD, &kasan_enabled, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, checks, CTLFLAG_RW, &enabled_checks, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, quarantine, CTLFLAG_RW, &quarantine_enabled, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, report_ignored, CTLFLAG_RW, &report_ignored, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, free_yield_ms, CTLFLAG_RW, &free_yield, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, memused, CTLFLAG_RD, &shadow_pages_used, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, memtotal, CTLFLAG_RD, &shadow_pages_total, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, kexts, CTLFLAG_RD, &kexts_loaded, 0, "");
SYSCTL_COMPAT_UINT(_kern_kasan, OID_AUTO, debug,     CTLFLAG_RD, NULL, KASAN_DEBUG, "");
SYSCTL_COMPAT_UINT(_kern_kasan, OID_AUTO, zalloc,    CTLFLAG_RD, NULL, KASAN_ZALLOC, "");
SYSCTL_COMPAT_UINT(_kern_kasan, OID_AUTO, kalloc,    CTLFLAG_RD, NULL, KASAN_KALLOC, "");
SYSCTL_COMPAT_UINT(_kern_kasan, OID_AUTO, dynamicbl, CTLFLAG_RD, NULL, KASAN_DYNAMIC_BLACKLIST, "");

SYSCTL_PROC(_kern_kasan, OID_AUTO, fakestack,
                CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
                0, 0, sysctl_fakestack_enable, "I", "");

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", "");