text: /*
   * Xtensa KASAN shadow map initialization
   *
   * This file is subject to the terms and conditions of the GNU General Public
   * License.  See the file "COPYING" in the main directory of this archive
   * for more details.
   *
   * Copyright (C) 2017 Cadence Design Systems Inc.
   */
  
  #include <linux/memblock.h>
  #include <linux/init_task.h>
  #include <linux/kasan.h>
  #include <linux/kernel.h>
  #include <asm/initialize_mmu.h>
  #include <asm/tlbflush.h>
  #include <asm/traps.h>
  
  void __init kasan_early_init(void)
  {
  	unsigned long vaddr = KASAN_SHADOW_START;
  	pgd_t *pgd = pgd_offset_k(vaddr);
  	pmd_t *pmd = pmd_offset(pgd, vaddr);
  	int i;
  
  	for (i = 0; i < PTRS_PER_PTE; ++i)
  		set_pte(kasan_early_shadow_pte + i,
  			mk_pte(virt_to_page(kasan_early_shadow_page),
  				PAGE_KERNEL));
  
  	for (vaddr = 0; vaddr < KASAN_SHADOW_SIZE; vaddr += PMD_SIZE, ++pmd) {
  		BUG_ON(!pmd_none(*pmd));
  		set_pmd(pmd, __pmd((unsigned long)kasan_early_shadow_pte));
  	}
  	early_trap_init();
  }
  
  static void __init populate(void *start, void *end)
  {
  	unsigned long n_pages = (end - start) / PAGE_SIZE;
  	unsigned long n_pmds = n_pages / PTRS_PER_PTE;
  	unsigned long i, j;
  	unsigned long vaddr = (unsigned long)start;
  	pgd_t *pgd = pgd_offset_k(vaddr);
  	pmd_t *pmd = pmd_offset(pgd, vaddr);
  	pte_t *pte = memblock_alloc(n_pages * sizeof(pte_t), PAGE_SIZE);
  
  	if (!pte)
  		panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
  		      __func__, n_pages * sizeof(pte_t), PAGE_SIZE);
  
  	pr_debug("%s: %p - %p\n", __func__, start, end);
  
  	for (i = j = 0; i < n_pmds; ++i) {
  		int k;
  
  		for (k = 0; k < PTRS_PER_PTE; ++k, ++j) {
  			phys_addr_t phys =
  				memblock_phys_alloc_range(PAGE_SIZE, PAGE_SIZE,
  							  0,
  							  MEMBLOCK_ALLOC_ANYWHERE);
  
  			if (!phys)
  				panic("Failed to allocate page table page\n");
  
  			set_pte(pte + j, pfn_pte(PHYS_PFN(phys), PAGE_KERNEL));
  		}
  	}
  
  	for (i = 0; i < n_pmds ; ++i, pte += PTRS_PER_PTE)
  		set_pmd(pmd + i, __pmd((unsigned long)pte));
  
  	local_flush_tlb_all();
  	memset(start, 0, end - start);
  }
  
  void __init kasan_init(void)
  {
  	int i;
  
  	BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_START -
  		     (KASAN_START_VADDR >> KASAN_SHADOW_SCALE_SHIFT));
  	BUILD_BUG_ON(VMALLOC_START < KASAN_START_VADDR);
  
  	/*
  	 * Replace shadow map pages that cover addresses from VMALLOC area
  	 * start to the end of KSEG with clean writable pages.
  	 */
  	populate(kasan_mem_to_shadow((void *)VMALLOC_START),
  		 kasan_mem_to_shadow((void *)XCHAL_KSEG_BYPASS_VADDR));
  
  	/*
  	 * Write protect kasan_early_shadow_page and zero-initialize it again.
  	 */
  	for (i = 0; i < PTRS_PER_PTE; ++i)
  		set_pte(kasan_early_shadow_pte + i,
  			mk_pte(virt_to_page(kasan_early_shadow_page),
  				PAGE_KERNEL_RO));
  
  	local_flush_tlb_all();
  	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
  
  	/* At this point kasan is fully initialized. Enable error messages. */
  	current->kasan_depth = 0;
  	pr_info("KernelAddressSanitizer initialized\n");
  }
  