Skip to content
Snippets Groups Projects
Select Git revision
  • cdcd6aef9db5797995d4153ea19fdf56d189f0e4
  • drm-misc-templates default
  • wip/final/kci-gitlab-lava-v1
  • wip/vignesh/kci-lava-gitlab-runner
  • kci-gitlab-igt-v8
  • kci-gitlab-igt-v4
  • drm-misc-fixes-2024-10-02
  • drm-misc-next-2024-09-26
  • drm-misc-fixes-2024-09-26
  • drm-misc-next-2024-09-20
  • drm-misc-fixes-2024-09-12
  • drm-misc-fixes-2024-09-05
  • drm-misc-next-fixes-2024-09-05
  • drm-misc-fixes-2024-08-29
  • drm-misc-next-2024-08-29
  • drm-misc-next-2024-08-22
  • drm-misc-fixes-2024-08-22
  • drm-misc-next-2024-08-16
  • drm-misc-fixes-2024-08-15
  • drm-misc-next-2024-08-09
  • drm-misc-fixes-2024-08-08
  • drm-misc-next-2024-08-01
  • drm-misc-fixes-2024-08-01
  • drm-misc-next-fixes-2024-07-25
  • drm-misc-next-fixes-2024-07-19
  • drm-misc-next-fixes-2024-07-11
26 results

vc4_mock_output.c

Blame
  • common.c 27.54 KiB
    // SPDX-License-Identifier: GPL-2.0
    /*
     * This file contains common generic and tag-based KASAN 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.
     *
     */
    
    #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 <linux/uaccess.h>
    
    #include <asm/tlbflush.h>
    
    #include "kasan.h"
    #include "../slab.h"
    
    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 unsigned int filter_irq_stacks(unsigned long *entries,
    					     unsigned int nr_entries)
    {
    	unsigned int i;
    
    	for (i = 0; i < nr_entries; i++) {
    		if (in_irqentry_text(entries[i])) {
    			/* Include the irqentry function into the stack. */
    			return i + 1;
    		}
    	}
    	return nr_entries;
    }
    
    static inline depot_stack_handle_t save_stack(gfp_t flags)
    {
    	unsigned long entries[KASAN_STACK_DEPTH];
    	unsigned int nr_entries;
    
    	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
    	nr_entries = filter_irq_stacks(entries, nr_entries);
    	return stack_depot_save(entries, nr_entries, flags);
    }
    
    static inline void set_track(struct kasan_track *track, gfp_t flags)
    {
    	track->pid = current->pid;
    	track->stack = save_stack(flags);
    }
    
    void kasan_enable_current(void)
    {
    	current->kasan_depth++;
    }
    
    void kasan_disable_current(void)
    {
    	current->kasan_depth--;
    }
    
    bool __kasan_check_read(const volatile void *p, unsigned int size)
    {
    	return check_memory_region((unsigned long)p, size, false, _RET_IP_);
    }
    EXPORT_SYMBOL(__kasan_check_read);
    
    bool __kasan_check_write(const volatile void *p, unsigned int size)
    {
    	return 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);
    }
    
    /*
     * Poisons the shadow memory for 'size' bytes starting from 'addr'.
     * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
     */
    void kasan_poison_shadow(const void *address, size_t size, u8 value)
    {
    	void *shadow_start, *shadow_end;
    
    	/*
    	 * Perform shadow offset calculation based on untagged address, as
    	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
    	 * addresses to this function.
    	 */
    	address = reset_tag(address);
    
    	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)
    {
    	u8 tag = get_tag(address);
    
    	/*
    	 * Perform shadow offset calculation based on untagged address, as
    	 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
    	 * addresses to this function.
    	 */
    	address = reset_tag(address);
    
    	kasan_poison_shadow(address, size, tag);
    
    	if (size & KASAN_SHADOW_MASK) {
    		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
    
    		if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
    			*shadow = tag;
    		else
    			*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);
    }
    
    void kasan_alloc_pages(struct page *page, unsigned int order)
    {
    	u8 tag;
    	unsigned long i;
    
    	if (unlikely(PageHighMem(page)))
    		return;
    
    	tag = random_tag();
    	for (i = 0; i < (1 << order); i++)
    		page_kasan_tag_set(page + i, tag);
    	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 inline unsigned int optimal_redzone(unsigned int object_size)
    {
    	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
    		return 0;
    
    	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;
    	unsigned int redzone_size;
    	int redzone_adjust;
    
    	/* Add alloc meta. */
    	cache->kasan_info.alloc_meta_offset = *size;
    	*size += sizeof(struct kasan_alloc_meta);
    
    	/* Add free meta. */
    	if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
    	    (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_size = optimal_redzone(cache->object_size);
    	redzone_adjust = redzone_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 + redzone_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;
    }
    
    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);
    }
    
    struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
    					const void *object)
    {
    	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;
    }
    
    
    static void kasan_set_free_info(struct kmem_cache *cache,
    		void *object, u8 tag)
    {
    	struct kasan_alloc_meta *alloc_meta;
    	u8 idx = 0;
    
    	alloc_meta = get_alloc_info(cache, object);
    
    #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
    	idx = alloc_meta->free_track_idx;
    	alloc_meta->free_pointer_tag[idx] = tag;
    	alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS;
    #endif
    
    	set_track(&alloc_meta->free_track[idx], GFP_NOWAIT);
    }
    
    void kasan_poison_slab(struct page *page)
    {
    	unsigned long i;
    
    	for (i = 0; i < compound_nr(page); i++)
    		page_kasan_tag_reset(page + i);
    	kasan_poison_shadow(page_address(page), page_size(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);
    }
    
    /*
     * This function assigns a tag to an object considering the following:
     * 1. A cache might have a constructor, which might save a pointer to a slab
     *    object somewhere (e.g. in the object itself). We preassign a tag for
     *    each object in caches with constructors during slab creation and reuse
     *    the same tag each time a particular object is allocated.
     * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
     *    accessed after being freed. We preassign tags for objects in these
     *    caches as well.
     * 3. For SLAB allocator we can't preassign tags randomly since the freelist
     *    is stored as an array of indexes instead of a linked list. Assign tags
     *    based on objects indexes, so that objects that are next to each other
     *    get different tags.
     */
    static u8 assign_tag(struct kmem_cache *cache, const void *object,
    			bool init, bool keep_tag)
    {
    	/*
    	 * 1. When an object is kmalloc()'ed, two hooks are called:
    	 *    kasan_slab_alloc() and kasan_kmalloc(). We assign the
    	 *    tag only in the first one.
    	 * 2. We reuse the same tag for krealloc'ed objects.
    	 */
    	if (keep_tag)
    		return get_tag(object);
    
    	/*
    	 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
    	 * set, assign a tag when the object is being allocated (init == false).
    	 */
    	if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
    		return init ? KASAN_TAG_KERNEL : random_tag();
    
    	/* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
    #ifdef CONFIG_SLAB
    	/* For SLAB assign tags based on the object index in the freelist. */
    	return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
    #else
    	/*
    	 * For SLUB assign a random tag during slab creation, otherwise reuse
    	 * the already assigned tag.
    	 */
    	return init ? random_tag() : get_tag(object);
    #endif
    }
    
    void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
    						const void *object)
    {
    	struct kasan_alloc_meta *alloc_info;
    
    	if (!(cache->flags & SLAB_KASAN))
    		return (void *)object;
    
    	alloc_info = get_alloc_info(cache, object);
    	__memset(alloc_info, 0, sizeof(*alloc_info));
    
    	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
    		object = set_tag(object,
    				assign_tag(cache, object, true, false));
    
    	return (void *)object;
    }
    
    static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
    {
    	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
    		return shadow_byte < 0 ||
    			shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
    
    	/* else CONFIG_KASAN_SW_TAGS: */
    	if ((u8)shadow_byte == KASAN_TAG_INVALID)
    		return true;
    	if ((tag != KASAN_TAG_KERNEL) && (tag != (u8)shadow_byte))
    		return true;
    
    	return false;
    }
    
    static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
    			      unsigned long ip, bool quarantine)
    {
    	s8 shadow_byte;
    	u8 tag;
    	void *tagged_object;
    	unsigned long rounded_up_size;
    
    	tag = get_tag(object);
    	tagged_object = object;
    	object = reset_tag(object);
    
    	if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
    	    object)) {
    		kasan_report_invalid_free(tagged_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_invalid(tag, shadow_byte)) {
    		kasan_report_invalid_free(tagged_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 ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
    			unlikely(!(cache->flags & SLAB_KASAN)))
    		return false;
    
    	kasan_set_free_info(cache, object, tag);
    
    	quarantine_put(get_free_info(cache, object), cache);
    
    	return IS_ENABLED(CONFIG_KASAN_GENERIC);
    }
    
    bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
    {
    	return __kasan_slab_free(cache, object, ip, true);
    }
    
    static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
    				size_t size, gfp_t flags, bool keep_tag)
    {
    	unsigned long redzone_start;
    	unsigned long redzone_end;
    	u8 tag = 0xff;
    
    	if (gfpflags_allow_blocking(flags))
    		quarantine_reduce();
    
    	if (unlikely(object == NULL))
    		return NULL;
    
    	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);
    
    	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
    		tag = assign_tag(cache, object, false, keep_tag);
    
    	/* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
    	kasan_unpoison_shadow(set_tag(object, tag), 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);
    
    	return set_tag(object, tag);
    }
    
    void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
    					gfp_t flags)
    {
    	return __kasan_kmalloc(cache, object, cache->object_size, flags, false);
    }
    
    void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
    				size_t size, gfp_t flags)
    {
    	return __kasan_kmalloc(cache, object, size, flags, true);
    }
    EXPORT_SYMBOL(kasan_kmalloc);
    
    void * __must_check 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 NULL;
    
    	page = virt_to_page(ptr);
    	redzone_start = round_up((unsigned long)(ptr + size),
    				KASAN_SHADOW_SCALE_SIZE);
    	redzone_end = (unsigned long)ptr + page_size(page);
    
    	kasan_unpoison_shadow(ptr, size);
    	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
    		KASAN_PAGE_REDZONE);
    
    	return (void *)ptr;
    }
    
    void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
    {
    	struct page *page;
    
    	if (unlikely(object == ZERO_SIZE_PTR))
    		return (void *)object;
    
    	page = virt_to_head_page(object);
    
    	if (unlikely(!PageSlab(page)))
    		return kasan_kmalloc_large(object, size, flags);
    	else
    		return __kasan_kmalloc(page->slab_cache, object, size,
    						flags, true);
    }
    
    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(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. */
    }
    
    #ifndef CONFIG_KASAN_VMALLOC
    int kasan_module_alloc(void *addr, size_t size)
    {
    	void *ret;
    	size_t scaled_size;
    	size_t shadow_size;
    	unsigned long shadow_start;
    
    	shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
    	scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
    	shadow_size = round_up(scaled_size, 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,
    			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
    			__builtin_return_address(0));
    
    	if (ret) {
    		__memset(ret, KASAN_SHADOW_INIT, shadow_size);
    		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));
    }
    #endif
    
    extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);
    
    void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
    {
    	unsigned long flags = user_access_save();
    	__kasan_report(addr, size, is_write, ip);
    	user_access_restore(flags);
    }
    
    #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;
    }
    
    core_initcall(kasan_memhotplug_init);
    #endif
    
    #ifdef CONFIG_KASAN_VMALLOC
    static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
    				      void *unused)
    {
    	unsigned long page;
    	pte_t pte;
    
    	if (likely(!pte_none(*ptep)))
    		return 0;
    
    	page = __get_free_page(GFP_KERNEL);
    	if (!page)
    		return -ENOMEM;
    
    	memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE);
    	pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL);
    
    	spin_lock(&init_mm.page_table_lock);
    	if (likely(pte_none(*ptep))) {
    		set_pte_at(&init_mm, addr, ptep, pte);
    		page = 0;
    	}
    	spin_unlock(&init_mm.page_table_lock);
    	if (page)
    		free_page(page);
    	return 0;
    }
    
    int kasan_populate_vmalloc(unsigned long requested_size, struct vm_struct *area)
    {
    	unsigned long shadow_start, shadow_end;
    	int ret;
    
    	shadow_start = (unsigned long)kasan_mem_to_shadow(area->addr);
    	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
    	shadow_end = (unsigned long)kasan_mem_to_shadow(area->addr +
    							area->size);
    	shadow_end = ALIGN(shadow_end, PAGE_SIZE);
    
    	ret = apply_to_page_range(&init_mm, shadow_start,
    				  shadow_end - shadow_start,
    				  kasan_populate_vmalloc_pte, NULL);
    	if (ret)
    		return ret;
    
    	flush_cache_vmap(shadow_start, shadow_end);
    
    	kasan_unpoison_shadow(area->addr, requested_size);
    
    	area->flags |= VM_KASAN;
    
    	/*
    	 * We need to be careful about inter-cpu effects here. Consider:
    	 *
    	 *   CPU#0				  CPU#1
    	 * WRITE_ONCE(p, vmalloc(100));		while (x = READ_ONCE(p)) ;
    	 *					p[99] = 1;
    	 *
    	 * With compiler instrumentation, that ends up looking like this:
    	 *
    	 *   CPU#0				  CPU#1
    	 * // vmalloc() allocates memory
    	 * // let a = area->addr
    	 * // we reach kasan_populate_vmalloc
    	 * // and call kasan_unpoison_shadow:
    	 * STORE shadow(a), unpoison_val
    	 * ...
    	 * STORE shadow(a+99), unpoison_val	x = LOAD p
    	 * // rest of vmalloc process		<data dependency>
    	 * STORE p, a				LOAD shadow(x+99)
    	 *
    	 * If there is no barrier between the end of unpoisioning the shadow
    	 * and the store of the result to p, the stores could be committed
    	 * in a different order by CPU#0, and CPU#1 could erroneously observe
    	 * poison in the shadow.
    	 *
    	 * We need some sort of barrier between the stores.
    	 *
    	 * In the vmalloc() case, this is provided by a smp_wmb() in
    	 * clear_vm_uninitialized_flag(). In the per-cpu allocator and in
    	 * get_vm_area() and friends, the caller gets shadow allocated but
    	 * doesn't have any pages mapped into the virtual address space that
    	 * has been reserved. Mapping those pages in will involve taking and
    	 * releasing a page-table lock, which will provide the barrier.
    	 */
    
    	return 0;
    }
    
    /*
     * Poison the shadow for a vmalloc region. Called as part of the
     * freeing process at the time the region is freed.
     */
    void kasan_poison_vmalloc(void *start, unsigned long size)
    {
    	size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
    	kasan_poison_shadow(start, size, KASAN_VMALLOC_INVALID);
    }
    
    static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
    					void *unused)
    {
    	unsigned long page;
    
    	page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);
    
    	spin_lock(&init_mm.page_table_lock);
    
    	if (likely(!pte_none(*ptep))) {
    		pte_clear(&init_mm, addr, ptep);
    		free_page(page);
    	}
    	spin_unlock(&init_mm.page_table_lock);
    
    	return 0;
    }
    
    /*
     * Release the backing for the vmalloc region [start, end), which
     * lies within the free region [free_region_start, free_region_end).
     *
     * This can be run lazily, long after the region was freed. It runs
     * under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap
     * infrastructure.
     *
     * How does this work?
     * -------------------
     *
     * We have a region that is page aligned, labelled as A.
     * That might not map onto the shadow in a way that is page-aligned:
     *
     *                    start                     end
     *                    v                         v
     * |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc
     *  -------- -------- --------          -------- --------
     *      |        |       |                 |        |
     *      |        |       |         /-------/        |
     *      \-------\|/------/         |/---------------/
     *              |||                ||
     *             |??AAAAAA|AAAAAAAA|AA??????|                < shadow
     *                 (1)      (2)      (3)
     *
     * First we align the start upwards and the end downwards, so that the
     * shadow of the region aligns with shadow page boundaries. In the
     * example, this gives us the shadow page (2). This is the shadow entirely
     * covered by this allocation.
     *
     * Then we have the tricky bits. We want to know if we can free the
     * partially covered shadow pages - (1) and (3) in the example. For this,
     * we are given the start and end of the free region that contains this
     * allocation. Extending our previous example, we could have:
     *
     *  free_region_start                                    free_region_end
     *  |                 start                     end      |
     *  v                 v                         v        v
     * |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc
     *  -------- -------- --------          -------- --------
     *      |        |       |                 |        |
     *      |        |       |         /-------/        |
     *      \-------\|/------/         |/---------------/
     *              |||                ||
     *             |FFAAAAAA|AAAAAAAA|AAF?????|                < shadow
     *                 (1)      (2)      (3)
     *
     * Once again, we align the start of the free region up, and the end of
     * the free region down so that the shadow is page aligned. So we can free
     * page (1) - we know no allocation currently uses anything in that page,
     * because all of it is in the vmalloc free region. But we cannot free
     * page (3), because we can't be sure that the rest of it is unused.
     *
     * We only consider pages that contain part of the original region for
     * freeing: we don't try to free other pages from the free region or we'd
     * end up trying to free huge chunks of virtual address space.
     *
     * Concurrency
     * -----------
     *
     * How do we know that we're not freeing a page that is simultaneously
     * being used for a fresh allocation in kasan_populate_vmalloc(_pte)?
     *
     * We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running
     * at the same time. While we run under free_vmap_area_lock, the population
     * code does not.
     *
     * free_vmap_area_lock instead operates to ensure that the larger range
     * [free_region_start, free_region_end) is safe: because __alloc_vmap_area and
     * the per-cpu region-finding algorithm both run under free_vmap_area_lock,
     * no space identified as free will become used while we are running. This
     * means that so long as we are careful with alignment and only free shadow
     * pages entirely covered by the free region, we will not run in to any
     * trouble - any simultaneous allocations will be for disjoint regions.
     */
    void kasan_release_vmalloc(unsigned long start, unsigned long end,
    			   unsigned long free_region_start,
    			   unsigned long free_region_end)
    {
    	void *shadow_start, *shadow_end;
    	unsigned long region_start, region_end;
    
    	region_start = ALIGN(start, PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
    	region_end = ALIGN_DOWN(end, PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
    
    	free_region_start = ALIGN(free_region_start,
    				  PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
    
    	if (start != region_start &&
    	    free_region_start < region_start)
    		region_start -= PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE;
    
    	free_region_end = ALIGN_DOWN(free_region_end,
    				     PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
    
    	if (end != region_end &&
    	    free_region_end > region_end)
    		region_end += PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE;
    
    	shadow_start = kasan_mem_to_shadow((void *)region_start);
    	shadow_end = kasan_mem_to_shadow((void *)region_end);
    
    	if (shadow_end > shadow_start) {
    		apply_to_page_range(&init_mm, (unsigned long)shadow_start,
    				    (unsigned long)(shadow_end - shadow_start),
    				    kasan_depopulate_vmalloc_pte, NULL);
    		flush_tlb_kernel_range((unsigned long)shadow_start,
    				       (unsigned long)shadow_end);
    	}
    }
    #endif