// SPDX-License-Identifier: GPL-2.0
  /*
   * This file contains KASAN runtime code that manages shadow memory for
   * generic and software tag-based KASAN modes.
   *
   * 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>
   */
  
  #include <linux/init.h>
  #include <linux/kasan.h>
  #include <linux/kernel.h>

  #include <linux/kfence.h>

  #include <linux/kmemleak.h>
  #include <linux/memory.h>
  #include <linux/mm.h>
  #include <linux/string.h>
  #include <linux/types.h>
  #include <linux/vmalloc.h>
  
  #include <asm/cacheflush.h>
  #include <asm/tlbflush.h>
  
  #include "kasan.h"
  
  bool __kasan_check_read(const volatile void *p, unsigned int size)
  {

  	return kasan_check_range((unsigned long)p, size, false, _RET_IP_);

  }
  EXPORT_SYMBOL(__kasan_check_read);
  
  bool __kasan_check_write(const volatile void *p, unsigned int size)
  {

  	return kasan_check_range((unsigned long)p, size, true, _RET_IP_);

  }
  EXPORT_SYMBOL(__kasan_check_write);
  
  #undef memset
  void *memset(void *addr, int c, size_t len)
  {

  	if (!kasan_check_range((unsigned long)addr, len, true, _RET_IP_))

  		return NULL;
  
  	return __memset(addr, c, len);
  }
  
  #ifdef __HAVE_ARCH_MEMMOVE
  #undef memmove
  void *memmove(void *dest, const void *src, size_t len)
  {

  	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||
  	    !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))

  		return NULL;
  
  	return __memmove(dest, src, len);
  }
  #endif
  
  #undef memcpy
  void *memcpy(void *dest, const void *src, size_t len)
  {

  	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||
  	    !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))

  		return NULL;
  
  	return __memcpy(dest, src, len);
  }

  void kasan_poison(const void *addr, size_t size, u8 value, bool init)

  {
  	void *shadow_start, *shadow_end;

  	if (!kasan_arch_is_ready())
  		return;

  	/*
  	 * 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.
  	 */

  	addr = kasan_reset_tag(addr);

  	/* Skip KFENCE memory if called explicitly outside of sl*b. */

  	if (is_kfence_address(addr))

  		return;

  	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
  		return;
  	if (WARN_ON(size & KASAN_GRANULE_MASK))
  		return;
  
  	shadow_start = kasan_mem_to_shadow(addr);
  	shadow_end = kasan_mem_to_shadow(addr + size);

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

  EXPORT_SYMBOL(kasan_poison);

  #ifdef CONFIG_KASAN_GENERIC

  void kasan_poison_last_granule(const void *addr, size_t size)

  {

  	if (!kasan_arch_is_ready())
  		return;

  	if (size & KASAN_GRANULE_MASK) {

  		u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size);

  		*shadow = size & KASAN_GRANULE_MASK;
  	}
  }
  #endif

  void kasan_unpoison(const void *addr, size_t size, bool init)

  {

  	u8 tag = get_tag(addr);

  
  	/*
  	 * 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.
  	 */

  	addr = kasan_reset_tag(addr);

  	/*
  	 * Skip KFENCE memory if called explicitly outside of sl*b. Also note
  	 * that calls to ksize(), where size is not a multiple of machine-word
  	 * size, would otherwise poison the invalid portion of the word.
  	 */

  	if (is_kfence_address(addr))
  		return;
  
  	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))

  		return;

  	/* Unpoison all granules that cover the object. */

  	kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag, false);

  	/* Partially poison the last granule for the generic mode. */
  	if (IS_ENABLED(CONFIG_KASAN_GENERIC))

  		kasan_poison_last_granule(addr, size);

  }
  
  #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_GRANULE_SIZE) ||

  		WARN_ON(start_kaddr % KASAN_MEMORY_PER_SHADOW_PAGE))

  		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 addr, unsigned long size)
  {
  	unsigned long shadow_start, shadow_end;
  	int ret;
  
  	if (!is_vmalloc_or_module_addr((void *)addr))
  		return 0;
  
  	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
  	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
  	shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + 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);
  
  	/*
  	 * 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:

  	 * 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 unpoisoning 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(const void *start, unsigned long size)
  {
  	if (!is_vmalloc_or_module_addr(start))
  		return;
  
  	size = round_up(size, KASAN_GRANULE_SIZE);

  	kasan_poison(start, size, KASAN_VMALLOC_INVALID, false);

  }
  
  void kasan_unpoison_vmalloc(const void *start, unsigned long size)
  {
  	if (!is_vmalloc_or_module_addr(start))
  		return;

  	kasan_unpoison(start, size, false);

  }
  
  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, labeled 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;
  	unsigned long size;

  	region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE);
  	region_end = ALIGN_DOWN(end, KASAN_MEMORY_PER_SHADOW_PAGE);

  	free_region_start = ALIGN(free_region_start, KASAN_MEMORY_PER_SHADOW_PAGE);

  
  	if (start != region_start &&
  	    free_region_start < region_start)

  		region_start -= KASAN_MEMORY_PER_SHADOW_PAGE;

  	free_region_end = ALIGN_DOWN(free_region_end, KASAN_MEMORY_PER_SHADOW_PAGE);

  
  	if (end != region_end &&
  	    free_region_end > region_end)

  		region_end += KASAN_MEMORY_PER_SHADOW_PAGE;

  
  	shadow_start = kasan_mem_to_shadow((void *)region_start);
  	shadow_end = kasan_mem_to_shadow((void *)region_end);
  
  	if (shadow_end > shadow_start) {
  		size = shadow_end - shadow_start;
  		apply_to_existing_page_range(&init_mm,
  					     (unsigned long)shadow_start,
  					     size, kasan_depopulate_vmalloc_pte,
  					     NULL);
  		flush_tlb_kernel_range((unsigned long)shadow_start,
  				       (unsigned long)shadow_end);
  	}
  }
  
  #else /* CONFIG_KASAN_VMALLOC */

  int kasan_module_alloc(void *addr, size_t size, gfp_t gfp_mask)

  {
  	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_GRANULE_SIZE - 1) >>
  				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) {

  		struct vm_struct *vm = find_vm_area(addr);

  		__memset(ret, KASAN_SHADOW_INIT, shadow_size);

  		vm->flags |= VM_KASAN;

  		kmemleak_ignore(ret);

  
  		if (vm->flags & VM_DEFER_KMEMLEAK)
  			kmemleak_vmalloc(vm, size, gfp_mask);

  		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