kasan: free allocated shadow memory on MEM_CANCEL_ONLINE

[mirror_ubuntu-eoan-kernel.git] / mm / kasan / kasan.c

/*
 * This file contains shadow memory manipulation code.
 *
 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
 *
 * Some code borrowed from https://github.com/xairy/kasan-prototype by
 *        Andrey Konovalov <andreyknvl@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define DISABLE_BRANCH_PROFILING

#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/kmemleak.h>
#include <linux/linkage.h>
#include <linux/memblock.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/bug.h>

#include "kasan.h"
#include "../slab.h"

void kasan_enable_current(void)
{
        current->kasan_depth++;
}

void kasan_disable_current(void)
{
        current->kasan_depth--;
}

/*
 * Poisons the shadow memory for 'size' bytes starting from 'addr'.
 * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
 */
static void kasan_poison_shadow(const void *address, size_t size, u8 value)
{
        void *shadow_start, *shadow_end;

        shadow_start = kasan_mem_to_shadow(address);
        shadow_end = kasan_mem_to_shadow(address + size);

        memset(shadow_start, value, shadow_end - shadow_start);
}

void kasan_unpoison_shadow(const void *address, size_t size)
{
        kasan_poison_shadow(address, size, 0);

        if (size & KASAN_SHADOW_MASK) {
                u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
                *shadow = size & KASAN_SHADOW_MASK;
        }
}

static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
{
        void *base = task_stack_page(task);
        size_t size = sp - base;

        kasan_unpoison_shadow(base, size);
}

/* Unpoison the entire stack for a task. */
void kasan_unpoison_task_stack(struct task_struct *task)
{
        __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
}

/* Unpoison the stack for the current task beyond a watermark sp value. */
asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
{
        /*
         * Calculate the task stack base address.  Avoid using 'current'
         * because this function is called by early resume code which hasn't
         * yet set up the percpu register (%gs).
         */
        void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));

        kasan_unpoison_shadow(base, watermark - base);
}

/*
 * Clear all poison for the region between the current SP and a provided
 * watermark value, as is sometimes required prior to hand-crafted asm function
 * returns in the middle of functions.
 */
void kasan_unpoison_stack_above_sp_to(const void *watermark)
{
        const void *sp = __builtin_frame_address(0);
        size_t size = watermark - sp;

        if (WARN_ON(sp > watermark))
                return;
        kasan_unpoison_shadow(sp, size);
}

/*
 * All functions below always inlined so compiler could
 * perform better optimizations in each of __asan_loadX/__assn_storeX
 * depending on memory access size X.
 */

static __always_inline bool memory_is_poisoned_1(unsigned long addr)
{
        s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);

        if (unlikely(shadow_value)) {
                s8 last_accessible_byte = addr & KASAN_SHADOW_MASK;
                return unlikely(last_accessible_byte >= shadow_value);
        }

        return false;
}

static __always_inline bool memory_is_poisoned_2_4_8(unsigned long addr,
                                                unsigned long size)
{
        u8 *shadow_addr = (u8 *)kasan_mem_to_shadow((void *)addr);

        /*
         * Access crosses 8(shadow size)-byte boundary. Such access maps
         * into 2 shadow bytes, so we need to check them both.
         */
        if (unlikely(((addr + size - 1) & KASAN_SHADOW_MASK) < size - 1))
                return *shadow_addr || memory_is_poisoned_1(addr + size - 1);

        return memory_is_poisoned_1(addr + size - 1);
}

static __always_inline bool memory_is_poisoned_16(unsigned long addr)
{
        u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);

        /* Unaligned 16-bytes access maps into 3 shadow bytes. */
        if (unlikely(!IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
                return *shadow_addr || memory_is_poisoned_1(addr + 15);

        return *shadow_addr;
}

static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
                                        size_t size)
{
        while (size) {
                if (unlikely(*start))
                        return (unsigned long)start;
                start++;
                size--;
        }

        return 0;
}

static __always_inline unsigned long memory_is_nonzero(const void *start,
                                                const void *end)
{
        unsigned int words;
        unsigned long ret;
        unsigned int prefix = (unsigned long)start % 8;

        if (end - start <= 16)
                return bytes_is_nonzero(start, end - start);

        if (prefix) {
                prefix = 8 - prefix;
                ret = bytes_is_nonzero(start, prefix);
                if (unlikely(ret))
                        return ret;
                start += prefix;
        }

        words = (end - start) / 8;
        while (words) {
                if (unlikely(*(u64 *)start))
                        return bytes_is_nonzero(start, 8);
                start += 8;
                words--;
        }

        return bytes_is_nonzero(start, (end - start) % 8);
}

static __always_inline bool memory_is_poisoned_n(unsigned long addr,
                                                size_t size)
{
        unsigned long ret;

        ret = memory_is_nonzero(kasan_mem_to_shadow((void *)addr),
                        kasan_mem_to_shadow((void *)addr + size - 1) + 1);

        if (unlikely(ret)) {
                unsigned long last_byte = addr + size - 1;
                s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);

                if (unlikely(ret != (unsigned long)last_shadow ||
                        ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
                        return true;
        }
        return false;
}

static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
{
        if (__builtin_constant_p(size)) {
                switch (size) {
                case 1:
                        return memory_is_poisoned_1(addr);
                case 2:
                case 4:
                case 8:
                        return memory_is_poisoned_2_4_8(addr, size);
                case 16:
                        return memory_is_poisoned_16(addr);
                default:
                        BUILD_BUG();
                }
        }

        return memory_is_poisoned_n(addr, size);
}

static __always_inline void check_memory_region_inline(unsigned long addr,
                                                size_t size, bool write,
                                                unsigned long ret_ip)
{
        if (unlikely(size == 0))
                return;

        if (unlikely((void *)addr <
                kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
                kasan_report(addr, size, write, ret_ip);
                return;
        }

        if (likely(!memory_is_poisoned(addr, size)))
                return;

        kasan_report(addr, size, write, ret_ip);
}

static void check_memory_region(unsigned long addr,
                                size_t size, bool write,
                                unsigned long ret_ip)
{
        check_memory_region_inline(addr, size, write, ret_ip);
}

void kasan_check_read(const volatile void *p, unsigned int size)
{
        check_memory_region((unsigned long)p, size, false, _RET_IP_);
}
EXPORT_SYMBOL(kasan_check_read);

void kasan_check_write(const volatile void *p, unsigned int size)
{
        check_memory_region((unsigned long)p, size, true, _RET_IP_);
}
EXPORT_SYMBOL(kasan_check_write);

#undef memset
void *memset(void *addr, int c, size_t len)
{
        check_memory_region((unsigned long)addr, len, true, _RET_IP_);

        return __memset(addr, c, len);
}

#undef memmove
void *memmove(void *dest, const void *src, size_t len)
{
        check_memory_region((unsigned long)src, len, false, _RET_IP_);
        check_memory_region((unsigned long)dest, len, true, _RET_IP_);

        return __memmove(dest, src, len);
}

#undef memcpy
void *memcpy(void *dest, const void *src, size_t len)
{
        check_memory_region((unsigned long)src, len, false, _RET_IP_);
        check_memory_region((unsigned long)dest, len, true, _RET_IP_);

        return __memcpy(dest, src, len);
}

void kasan_alloc_pages(struct page *page, unsigned int order)
{
        if (likely(!PageHighMem(page)))
                kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
}

void kasan_free_pages(struct page *page, unsigned int order)
{
        if (likely(!PageHighMem(page)))
                kasan_poison_shadow(page_address(page),
                                PAGE_SIZE << order,
                                KASAN_FREE_PAGE);
}

/*
 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
 * For larger allocations larger redzones are used.
 */
static unsigned int optimal_redzone(unsigned int object_size)
{
        return
                object_size <= 64        - 16   ? 16 :
                object_size <= 128       - 32   ? 32 :
                object_size <= 512       - 64   ? 64 :
                object_size <= 4096      - 128  ? 128 :
                object_size <= (1 << 14) - 256  ? 256 :
                object_size <= (1 << 15) - 512  ? 512 :
                object_size <= (1 << 16) - 1024 ? 1024 : 2048;
}

void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
                        slab_flags_t *flags)
{
        unsigned int orig_size = *size;
        int redzone_adjust;

        /* Add alloc meta. */
        cache->kasan_info.alloc_meta_offset = *size;
        *size += sizeof(struct kasan_alloc_meta);

        /* Add free meta. */
        if (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
            cache->object_size < sizeof(struct kasan_free_meta)) {
                cache->kasan_info.free_meta_offset = *size;
                *size += sizeof(struct kasan_free_meta);
        }
        redzone_adjust = optimal_redzone(cache->object_size) -
                (*size - cache->object_size);

        if (redzone_adjust > 0)
                *size += redzone_adjust;

        *size = min_t(unsigned int, KMALLOC_MAX_SIZE,
                        max(*size, cache->object_size +
                                        optimal_redzone(cache->object_size)));

        /*
         * If the metadata doesn't fit, don't enable KASAN at all.
         */
        if (*size <= cache->kasan_info.alloc_meta_offset ||
                        *size <= cache->kasan_info.free_meta_offset) {
                cache->kasan_info.alloc_meta_offset = 0;
                cache->kasan_info.free_meta_offset = 0;
                *size = orig_size;
                return;
        }

        *flags |= SLAB_KASAN;
}

void kasan_cache_shrink(struct kmem_cache *cache)
{
        quarantine_remove_cache(cache);
}

void kasan_cache_shutdown(struct kmem_cache *cache)
{
        if (!__kmem_cache_empty(cache))
                quarantine_remove_cache(cache);
}

size_t kasan_metadata_size(struct kmem_cache *cache)
{
        return (cache->kasan_info.alloc_meta_offset ?
                sizeof(struct kasan_alloc_meta) : 0) +
                (cache->kasan_info.free_meta_offset ?
                sizeof(struct kasan_free_meta) : 0);
}

void kasan_poison_slab(struct page *page)
{
        kasan_poison_shadow(page_address(page),
                        PAGE_SIZE << compound_order(page),
                        KASAN_KMALLOC_REDZONE);
}

void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
{
        kasan_unpoison_shadow(object, cache->object_size);
}

void kasan_poison_object_data(struct kmem_cache *cache, void *object)
{
        kasan_poison_shadow(object,
                        round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
                        KASAN_KMALLOC_REDZONE);
}

static inline int in_irqentry_text(unsigned long ptr)
{
        return (ptr >= (unsigned long)&__irqentry_text_start &&
                ptr < (unsigned long)&__irqentry_text_end) ||
                (ptr >= (unsigned long)&__softirqentry_text_start &&
                 ptr < (unsigned long)&__softirqentry_text_end);
}

static inline void filter_irq_stacks(struct stack_trace *trace)
{
        int i;

        if (!trace->nr_entries)
                return;
        for (i = 0; i < trace->nr_entries; i++)
                if (in_irqentry_text(trace->entries[i])) {
                        /* Include the irqentry function into the stack. */
                        trace->nr_entries = i + 1;
                        break;
                }
}

static inline depot_stack_handle_t save_stack(gfp_t flags)
{
        unsigned long entries[KASAN_STACK_DEPTH];
        struct stack_trace trace = {
                .nr_entries = 0,
                .entries = entries,
                .max_entries = KASAN_STACK_DEPTH,
                .skip = 0
        };

        save_stack_trace(&trace);
        filter_irq_stacks(&trace);
        if (trace.nr_entries != 0 &&
            trace.entries[trace.nr_entries-1] == ULONG_MAX)
                trace.nr_entries--;

        return depot_save_stack(&trace, flags);
}

static inline void set_track(struct kasan_track *track, gfp_t flags)
{
        track->pid = current->pid;
        track->stack = save_stack(flags);
}

struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
                                        const void *object)
{
        BUILD_BUG_ON(sizeof(struct kasan_alloc_meta) > 32);
        return (void *)object + cache->kasan_info.alloc_meta_offset;
}

struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
                                      const void *object)
{
        BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
        return (void *)object + cache->kasan_info.free_meta_offset;
}

void kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
{
        struct kasan_alloc_meta *alloc_info;

        if (!(cache->flags & SLAB_KASAN))
                return;

        alloc_info = get_alloc_info(cache, object);
        __memset(alloc_info, 0, sizeof(*alloc_info));
}

void kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
{
        kasan_kmalloc(cache, object, cache->object_size, flags);
}

static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
                              unsigned long ip, bool quarantine)
{
        s8 shadow_byte;
        unsigned long rounded_up_size;

        if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
            object)) {
                kasan_report_invalid_free(object, ip);
                return true;
        }

        /* RCU slabs could be legally used after free within the RCU period */
        if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
                return false;

        shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
        if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
                kasan_report_invalid_free(object, ip);
                return true;
        }

        rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
        kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);

        if (!quarantine || unlikely(!(cache->flags & SLAB_KASAN)))
                return false;

        set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
        quarantine_put(get_free_info(cache, object), cache);
        return true;
}

bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
{
        return __kasan_slab_free(cache, object, ip, true);
}

void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
                   gfp_t flags)
{
        unsigned long redzone_start;
        unsigned long redzone_end;

        if (gfpflags_allow_blocking(flags))
                quarantine_reduce();

        if (unlikely(object == NULL))
                return;

        redzone_start = round_up((unsigned long)(object + size),
                                KASAN_SHADOW_SCALE_SIZE);
        redzone_end = round_up((unsigned long)object + cache->object_size,
                                KASAN_SHADOW_SCALE_SIZE);

        kasan_unpoison_shadow(object, size);
        kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
                KASAN_KMALLOC_REDZONE);

        if (cache->flags & SLAB_KASAN)
                set_track(&get_alloc_info(cache, object)->alloc_track, flags);
}
EXPORT_SYMBOL(kasan_kmalloc);

void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
{
        struct page *page;
        unsigned long redzone_start;
        unsigned long redzone_end;

        if (gfpflags_allow_blocking(flags))
                quarantine_reduce();

        if (unlikely(ptr == NULL))
                return;

        page = virt_to_page(ptr);
        redzone_start = round_up((unsigned long)(ptr + size),
                                KASAN_SHADOW_SCALE_SIZE);
        redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));

        kasan_unpoison_shadow(ptr, size);
        kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
                KASAN_PAGE_REDZONE);
}

void kasan_krealloc(const void *object, size_t size, gfp_t flags)
{
        struct page *page;

        if (unlikely(object == ZERO_SIZE_PTR))
                return;

        page = virt_to_head_page(object);

        if (unlikely(!PageSlab(page)))
                kasan_kmalloc_large(object, size, flags);
        else
                kasan_kmalloc(page->slab_cache, object, size, flags);
}

void kasan_poison_kfree(void *ptr, unsigned long ip)
{
        struct page *page;

        page = virt_to_head_page(ptr);

        if (unlikely(!PageSlab(page))) {
                if (ptr != page_address(page)) {
                        kasan_report_invalid_free(ptr, ip);
                        return;
                }
                kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
                                KASAN_FREE_PAGE);
        } else {
                __kasan_slab_free(page->slab_cache, ptr, ip, false);
        }
}

void kasan_kfree_large(void *ptr, unsigned long ip)
{
        if (ptr != page_address(virt_to_head_page(ptr)))
                kasan_report_invalid_free(ptr, ip);
        /* The object will be poisoned by page_alloc. */
}

int kasan_module_alloc(void *addr, size_t size)
{
        void *ret;
        size_t shadow_size;
        unsigned long shadow_start;

        shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
        shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
                        PAGE_SIZE);

        if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
                return -EINVAL;

        ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
                        shadow_start + shadow_size,
                        GFP_KERNEL | __GFP_ZERO,
                        PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
                        __builtin_return_address(0));

        if (ret) {
                find_vm_area(addr)->flags |= VM_KASAN;
                kmemleak_ignore(ret);
                return 0;
        }

        return -ENOMEM;
}

void kasan_free_shadow(const struct vm_struct *vm)
{
        if (vm->flags & VM_KASAN)
                vfree(kasan_mem_to_shadow(vm->addr));
}

static void register_global(struct kasan_global *global)
{
        size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);

        kasan_unpoison_shadow(global->beg, global->size);

        kasan_poison_shadow(global->beg + aligned_size,
                global->size_with_redzone - aligned_size,
                KASAN_GLOBAL_REDZONE);
}

void __asan_register_globals(struct kasan_global *globals, size_t size)
{
        int i;

        for (i = 0; i < size; i++)
                register_global(&globals[i]);
}
EXPORT_SYMBOL(__asan_register_globals);

void __asan_unregister_globals(struct kasan_global *globals, size_t size)
{
}
EXPORT_SYMBOL(__asan_unregister_globals);

#define DEFINE_ASAN_LOAD_STORE(size)                                    \
        void __asan_load##size(unsigned long addr)                      \
        {                                                               \
                check_memory_region_inline(addr, size, false, _RET_IP_);\
        }                                                               \
        EXPORT_SYMBOL(__asan_load##size);                               \
        __alias(__asan_load##size)                                      \
        void __asan_load##size##_noabort(unsigned long);                \
        EXPORT_SYMBOL(__asan_load##size##_noabort);                     \
        void __asan_store##size(unsigned long addr)                     \
        {                                                               \
                check_memory_region_inline(addr, size, true, _RET_IP_); \
        }                                                               \
        EXPORT_SYMBOL(__asan_store##size);                              \
        __alias(__asan_store##size)                                     \
        void __asan_store##size##_noabort(unsigned long);               \
        EXPORT_SYMBOL(__asan_store##size##_noabort)

DEFINE_ASAN_LOAD_STORE(1);
DEFINE_ASAN_LOAD_STORE(2);
DEFINE_ASAN_LOAD_STORE(4);
DEFINE_ASAN_LOAD_STORE(8);
DEFINE_ASAN_LOAD_STORE(16);

void __asan_loadN(unsigned long addr, size_t size)
{
        check_memory_region(addr, size, false, _RET_IP_);
}
EXPORT_SYMBOL(__asan_loadN);

__alias(__asan_loadN)
void __asan_loadN_noabort(unsigned long, size_t);
EXPORT_SYMBOL(__asan_loadN_noabort);

void __asan_storeN(unsigned long addr, size_t size)
{
        check_memory_region(addr, size, true, _RET_IP_);
}
EXPORT_SYMBOL(__asan_storeN);

__alias(__asan_storeN)
void __asan_storeN_noabort(unsigned long, size_t);
EXPORT_SYMBOL(__asan_storeN_noabort);

/* to shut up compiler complaints */
void __asan_handle_no_return(void) {}
EXPORT_SYMBOL(__asan_handle_no_return);

/* Emitted by compiler to poison large objects when they go out of scope. */
void __asan_poison_stack_memory(const void *addr, size_t size)
{
        /*
         * Addr is KASAN_SHADOW_SCALE_SIZE-aligned and the object is surrounded
         * by redzones, so we simply round up size to simplify logic.
         */
        kasan_poison_shadow(addr, round_up(size, KASAN_SHADOW_SCALE_SIZE),
                            KASAN_USE_AFTER_SCOPE);
}
EXPORT_SYMBOL(__asan_poison_stack_memory);

/* Emitted by compiler to unpoison large objects when they go into scope. */
void __asan_unpoison_stack_memory(const void *addr, size_t size)
{
        kasan_unpoison_shadow(addr, size);
}
EXPORT_SYMBOL(__asan_unpoison_stack_memory);

/* Emitted by compiler to poison alloca()ed objects. */
void __asan_alloca_poison(unsigned long addr, size_t size)
{
        size_t rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
        size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
                        rounded_up_size;
        size_t rounded_down_size = round_down(size, KASAN_SHADOW_SCALE_SIZE);

        const void *left_redzone = (const void *)(addr -
                        KASAN_ALLOCA_REDZONE_SIZE);
        const void *right_redzone = (const void *)(addr + rounded_up_size);

        WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE));

        kasan_unpoison_shadow((const void *)(addr + rounded_down_size),
                              size - rounded_down_size);
        kasan_poison_shadow(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
                        KASAN_ALLOCA_LEFT);
        kasan_poison_shadow(right_redzone,
                        padding_size + KASAN_ALLOCA_REDZONE_SIZE,
                        KASAN_ALLOCA_RIGHT);
}
EXPORT_SYMBOL(__asan_alloca_poison);

/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom)
{
        if (unlikely(!stack_top || stack_top > stack_bottom))
                return;

        kasan_unpoison_shadow(stack_top, stack_bottom - stack_top);
}
EXPORT_SYMBOL(__asan_allocas_unpoison);

/* Emitted by the compiler to [un]poison local variables. */
#define DEFINE_ASAN_SET_SHADOW(byte) \
        void __asan_set_shadow_##byte(const void *addr, size_t size)    \
        {                                                               \
                __memset((void *)addr, 0x##byte, size);                 \
        }                                                               \
        EXPORT_SYMBOL(__asan_set_shadow_##byte)

DEFINE_ASAN_SET_SHADOW(00);
DEFINE_ASAN_SET_SHADOW(f1);
DEFINE_ASAN_SET_SHADOW(f2);
DEFINE_ASAN_SET_SHADOW(f3);
DEFINE_ASAN_SET_SHADOW(f5);
DEFINE_ASAN_SET_SHADOW(f8);

#ifdef CONFIG_MEMORY_HOTPLUG
static bool shadow_mapped(unsigned long addr)
{
        pgd_t *pgd = pgd_offset_k(addr);
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

        if (pgd_none(*pgd))
                return false;
        p4d = p4d_offset(pgd, addr);
        if (p4d_none(*p4d))
                return false;
        pud = pud_offset(p4d, addr);
        if (pud_none(*pud))
                return false;

        /*
         * We can't use pud_large() or pud_huge(), the first one is
         * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
         * pud_bad(), if pud is bad then it's bad because it's huge.
         */
        if (pud_bad(*pud))
                return true;
        pmd = pmd_offset(pud, addr);
        if (pmd_none(*pmd))
                return false;

        if (pmd_bad(*pmd))
                return true;
        pte = pte_offset_kernel(pmd, addr);
        return !pte_none(*pte);
}

static int __meminit kasan_mem_notifier(struct notifier_block *nb,
                        unsigned long action, void *data)
{
        struct memory_notify *mem_data = data;
        unsigned long nr_shadow_pages, start_kaddr, shadow_start;
        unsigned long shadow_end, shadow_size;

        nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
        start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
        shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
        shadow_size = nr_shadow_pages << PAGE_SHIFT;
        shadow_end = shadow_start + shadow_size;

        if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
                WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
                return NOTIFY_BAD;

        switch (action) {
        case MEM_GOING_ONLINE: {
                void *ret;

                /*
                 * If shadow is mapped already than it must have been mapped
                 * during the boot. This could happen if we onlining previously
                 * offlined memory.
                 */
                if (shadow_mapped(shadow_start))
                        return NOTIFY_OK;

                ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
                                        shadow_end, GFP_KERNEL,
                                        PAGE_KERNEL, VM_NO_GUARD,
                                        pfn_to_nid(mem_data->start_pfn),
                                        __builtin_return_address(0));
                if (!ret)
                        return NOTIFY_BAD;

                kmemleak_ignore(ret);
                return NOTIFY_OK;
        }
        case MEM_CANCEL_ONLINE:
        case MEM_OFFLINE: {
                struct vm_struct *vm;

                /*
                 * shadow_start was either mapped during boot by kasan_init()
                 * or during memory online by __vmalloc_node_range().
                 * In the latter case we can use vfree() to free shadow.
                 * Non-NULL result of the find_vm_area() will tell us if
                 * that was the second case.
                 *
                 * Currently it's not possible to free shadow mapped
                 * during boot by kasan_init(). It's because the code
                 * to do that hasn't been written yet. So we'll just
                 * leak the memory.
                 */
                vm = find_vm_area((void *)shadow_start);
                if (vm)
                        vfree((void *)shadow_start);
        }
        }

        return NOTIFY_OK;
}

static int __init kasan_memhotplug_init(void)
{
        hotplug_memory_notifier(kasan_mem_notifier, 0);

        return 0;
}

module_init(kasan_memhotplug_init);
#endif