text: // SPDX-License-Identifier: GPL-2.0
  /*
   * This file contains some kasan initialization code.
   *
   * Copyright (c) 2015 Samsung Electronics Co., Ltd.
   * Author: Andrey Ryabinin <ryabinin.a.a@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/memblock.h>
  #include <linux/init.h>
  #include <linux/kasan.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/pfn.h>
  #include <linux/slab.h>
  
  #include <asm/page.h>
  #include <asm/pgalloc.h>
  
  #include "kasan.h"
  
  /*
   * This page serves two purposes:
   *   - It used as early shadow memory. The entire shadow region populated
   *     with this page, before we will be able to setup normal shadow memory.
   *   - Latter it reused it as zero shadow to cover large ranges of memory
   *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
   */
  unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
  
  #if CONFIG_PGTABLE_LEVELS > 4
  p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
  static inline bool kasan_p4d_table(pgd_t pgd)
  {
  	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
  }
  #else
  static inline bool kasan_p4d_table(pgd_t pgd)
  {
  	return false;
  }
  #endif
  #if CONFIG_PGTABLE_LEVELS > 3
  pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
  static inline bool kasan_pud_table(p4d_t p4d)
  {
  	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
  }
  #else
  static inline bool kasan_pud_table(p4d_t p4d)
  {
  	return false;
  }
  #endif
  #if CONFIG_PGTABLE_LEVELS > 2
  pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
  static inline bool kasan_pmd_table(pud_t pud)
  {
  	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
  }
  #else
  static inline bool kasan_pmd_table(pud_t pud)
  {
  	return false;
  }
  #endif
  pte_t kasan_early_shadow_pte[PTRS_PER_PTE] __page_aligned_bss;
  
  static inline bool kasan_pte_table(pmd_t pmd)
  {
  	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
  }
  
  static inline bool kasan_early_shadow_page_entry(pte_t pte)
  {
  	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
  }
  
  static __init void *early_alloc(size_t size, int node)
  {
  	void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
  					   MEMBLOCK_ALLOC_ACCESSIBLE, node);
  
  	if (!ptr)
  		panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
  		      __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
  
  	return ptr;
  }
  
  static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
  				unsigned long end)
  {
  	pte_t *pte = pte_offset_kernel(pmd, addr);
  	pte_t zero_pte;
  
  	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
  				PAGE_KERNEL);
  	zero_pte = pte_wrprotect(zero_pte);
  
  	while (addr + PAGE_SIZE <= end) {
  		set_pte_at(&init_mm, addr, pte, zero_pte);
  		addr += PAGE_SIZE;
  		pte = pte_offset_kernel(pmd, addr);
  	}
  }
  
  static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
  				unsigned long end)
  {
  	pmd_t *pmd = pmd_offset(pud, addr);
  	unsigned long next;
  
  	do {
  		next = pmd_addr_end(addr, end);
  
  		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
  			pmd_populate_kernel(&init_mm, pmd,
  					lm_alias(kasan_early_shadow_pte));
  			continue;
  		}
  
  		if (pmd_none(*pmd)) {
  			pte_t *p;
  
  			if (slab_is_available())
  				p = pte_alloc_one_kernel(&init_mm);
  			else
  				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
  			if (!p)
  				return -ENOMEM;
  
  			pmd_populate_kernel(&init_mm, pmd, p);
  		}
  		zero_pte_populate(pmd, addr, next);
  	} while (pmd++, addr = next, addr != end);
  
  	return 0;
  }
  
  static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
  				unsigned long end)
  {
  	pud_t *pud = pud_offset(p4d, addr);
  	unsigned long next;
  
  	do {
  		next = pud_addr_end(addr, end);
  		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
  			pmd_t *pmd;
  
  			pud_populate(&init_mm, pud,
  					lm_alias(kasan_early_shadow_pmd));
  			pmd = pmd_offset(pud, addr);
  			pmd_populate_kernel(&init_mm, pmd,
  					lm_alias(kasan_early_shadow_pte));
  			continue;
  		}
  
  		if (pud_none(*pud)) {
  			pmd_t *p;
  
  			if (slab_is_available()) {
  				p = pmd_alloc(&init_mm, pud, addr);
  				if (!p)
  					return -ENOMEM;
  			} else {
  				pud_populate(&init_mm, pud,
  					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
  			}
  		}
  		zero_pmd_populate(pud, addr, next);
  	} while (pud++, addr = next, addr != end);
  
  	return 0;
  }
  
  static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
  				unsigned long end)
  {
  	p4d_t *p4d = p4d_offset(pgd, addr);
  	unsigned long next;
  
  	do {
  		next = p4d_addr_end(addr, end);
  		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
  			pud_t *pud;
  			pmd_t *pmd;
  
  			p4d_populate(&init_mm, p4d,
  					lm_alias(kasan_early_shadow_pud));
  			pud = pud_offset(p4d, addr);
  			pud_populate(&init_mm, pud,
  					lm_alias(kasan_early_shadow_pmd));
  			pmd = pmd_offset(pud, addr);
  			pmd_populate_kernel(&init_mm, pmd,
  					lm_alias(kasan_early_shadow_pte));
  			continue;
  		}
  
  		if (p4d_none(*p4d)) {
  			pud_t *p;
  
  			if (slab_is_available()) {
  				p = pud_alloc(&init_mm, p4d, addr);
  				if (!p)
  					return -ENOMEM;
  			} else {
  				p4d_populate(&init_mm, p4d,
  					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
  			}
  		}
  		zero_pud_populate(p4d, addr, next);
  	} while (p4d++, addr = next, addr != end);
  
  	return 0;
  }
  
  /**
   * kasan_populate_early_shadow - populate shadow memory region with
   *                               kasan_early_shadow_page
   * @shadow_start - start of the memory range to populate
   * @shadow_end   - end of the memory range to populate
   */
  int __ref kasan_populate_early_shadow(const void *shadow_start,
  					const void *shadow_end)
  {
  	unsigned long addr = (unsigned long)shadow_start;
  	unsigned long end = (unsigned long)shadow_end;
  	pgd_t *pgd = pgd_offset_k(addr);
  	unsigned long next;
  
  	do {
  		next = pgd_addr_end(addr, end);
  
  		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
  			p4d_t *p4d;
  			pud_t *pud;
  			pmd_t *pmd;
  
  			/*
  			 * kasan_early_shadow_pud should be populated with pmds
  			 * at this moment.
  			 * [pud,pmd]_populate*() below needed only for
  			 * 3,2 - level page tables where we don't have
  			 * puds,pmds, so pgd_populate(), pud_populate()
  			 * is noops.
  			 *
  			 * The ifndef is required to avoid build breakage.
  			 *
  			 * With 5level-fixup.h, pgd_populate() is not nop and
  			 * we reference kasan_early_shadow_p4d. It's not defined
  			 * unless 5-level paging enabled.
  			 *
  			 * The ifndef can be dropped once all KASAN-enabled
  			 * architectures will switch to pgtable-nop4d.h.
  			 */
  #ifndef __ARCH_HAS_5LEVEL_HACK
  			pgd_populate(&init_mm, pgd,
  					lm_alias(kasan_early_shadow_p4d));
  #endif
  			p4d = p4d_offset(pgd, addr);
  			p4d_populate(&init_mm, p4d,
  					lm_alias(kasan_early_shadow_pud));
  			pud = pud_offset(p4d, addr);
  			pud_populate(&init_mm, pud,
  					lm_alias(kasan_early_shadow_pmd));
  			pmd = pmd_offset(pud, addr);
  			pmd_populate_kernel(&init_mm, pmd,
  					lm_alias(kasan_early_shadow_pte));
  			continue;
  		}
  
  		if (pgd_none(*pgd)) {
  			p4d_t *p;
  
  			if (slab_is_available()) {
  				p = p4d_alloc(&init_mm, pgd, addr);
  				if (!p)
  					return -ENOMEM;
  			} else {
  				pgd_populate(&init_mm, pgd,
  					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
  			}
  		}
  		zero_p4d_populate(pgd, addr, next);
  	} while (pgd++, addr = next, addr != end);
  
  	return 0;
  }
  
  static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
  {
  	pte_t *pte;
  	int i;
  
  	for (i = 0; i < PTRS_PER_PTE; i++) {
  		pte = pte_start + i;
  		if (!pte_none(*pte))
  			return;
  	}
  
  	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
  	pmd_clear(pmd);
  }
  
  static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
  {
  	pmd_t *pmd;
  	int i;
  
  	for (i = 0; i < PTRS_PER_PMD; i++) {
  		pmd = pmd_start + i;
  		if (!pmd_none(*pmd))
  			return;
  	}
  
  	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
  	pud_clear(pud);
  }
  
  static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
  {
  	pud_t *pud;
  	int i;
  
  	for (i = 0; i < PTRS_PER_PUD; i++) {
  		pud = pud_start + i;
  		if (!pud_none(*pud))
  			return;
  	}
  
  	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
  	p4d_clear(p4d);
  }
  
  static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
  {
  	p4d_t *p4d;
  	int i;
  
  	for (i = 0; i < PTRS_PER_P4D; i++) {
  		p4d = p4d_start + i;
  		if (!p4d_none(*p4d))
  			return;
  	}
  
  	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
  	pgd_clear(pgd);
  }
  
  static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
  				unsigned long end)
  {
  	unsigned long next;
  
  	for (; addr < end; addr = next, pte++) {
  		next = (addr + PAGE_SIZE) & PAGE_MASK;
  		if (next > end)
  			next = end;
  
  		if (!pte_present(*pte))
  			continue;
  
  		if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
  			continue;
  		pte_clear(&init_mm, addr, pte);
  	}
  }
  
  static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
  				unsigned long end)
  {
  	unsigned long next;
  
  	for (; addr < end; addr = next, pmd++) {
  		pte_t *pte;
  
  		next = pmd_addr_end(addr, end);
  
  		if (!pmd_present(*pmd))
  			continue;
  
  		if (kasan_pte_table(*pmd)) {
  			if (IS_ALIGNED(addr, PMD_SIZE) &&
  			    IS_ALIGNED(next, PMD_SIZE))
  				pmd_clear(pmd);
  			continue;
  		}
  		pte = pte_offset_kernel(pmd, addr);
  		kasan_remove_pte_table(pte, addr, next);
  		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
  	}
  }
  
  static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
  				unsigned long end)
  {
  	unsigned long next;
  
  	for (; addr < end; addr = next, pud++) {
  		pmd_t *pmd, *pmd_base;
  
  		next = pud_addr_end(addr, end);
  
  		if (!pud_present(*pud))
  			continue;
  
  		if (kasan_pmd_table(*pud)) {
  			if (IS_ALIGNED(addr, PUD_SIZE) &&
  			    IS_ALIGNED(next, PUD_SIZE))
  				pud_clear(pud);
  			continue;
  		}
  		pmd = pmd_offset(pud, addr);
  		pmd_base = pmd_offset(pud, 0);
  		kasan_remove_pmd_table(pmd, addr, next);
  		kasan_free_pmd(pmd_base, pud);
  	}
  }
  
  static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
  				unsigned long end)
  {
  	unsigned long next;
  
  	for (; addr < end; addr = next, p4d++) {
  		pud_t *pud;
  
  		next = p4d_addr_end(addr, end);
  
  		if (!p4d_present(*p4d))
  			continue;
  
  		if (kasan_pud_table(*p4d)) {
  			if (IS_ALIGNED(addr, P4D_SIZE) &&
  			    IS_ALIGNED(next, P4D_SIZE))
  				p4d_clear(p4d);
  			continue;
  		}
  		pud = pud_offset(p4d, addr);
  		kasan_remove_pud_table(pud, addr, next);
  		kasan_free_pud(pud_offset(p4d, 0), p4d);
  	}
  }
  
  void kasan_remove_zero_shadow(void *start, unsigned long size)
  {
  	unsigned long addr, end, next;
  	pgd_t *pgd;
  
  	addr = (unsigned long)kasan_mem_to_shadow(start);
  	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
  
  	if (WARN_ON((unsigned long)start %
  			(KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
  	    WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
  		return;
  
  	for (; addr < end; addr = next) {
  		p4d_t *p4d;
  
  		next = pgd_addr_end(addr, end);
  
  		pgd = pgd_offset_k(addr);
  		if (!pgd_present(*pgd))
  			continue;
  
  		if (kasan_p4d_table(*pgd)) {
  			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
  			    IS_ALIGNED(next, PGDIR_SIZE))
  				pgd_clear(pgd);
  			continue;
  		}
  
  		p4d = p4d_offset(pgd, addr);
  		kasan_remove_p4d_table(p4d, addr, next);
  		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
  	}
  }
  
  int kasan_add_zero_shadow(void *start, unsigned long size)
  {
  	int ret;
  	void *shadow_start, *shadow_end;
  
  	shadow_start = kasan_mem_to_shadow(start);
  	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
  
  	if (WARN_ON((unsigned long)start %
  			(KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
  	    WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
  		return -EINVAL;
  
  	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
  	if (ret)
  		kasan_remove_zero_shadow(shadow_start,
  					size >> KASAN_SHADOW_SCALE_SHIFT);
  	return ret;
  }
  