/*
   * This file contains error reporting 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 <adech.fo@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/kernel.h>
  #include <linux/mm.h>
  #include <linux/printk.h>
  #include <linux/sched.h>
  #include <linux/slab.h>

  #include <linux/stackdepot.h>

  #include <linux/stacktrace.h>
  #include <linux/string.h>
  #include <linux/types.h>
  #include <linux/kasan.h>

  #include <linux/module.h>

  #include <asm/sections.h>

  #include "kasan.h"

  #include "../slab.h"

  
  /* Shadow layout customization. */
  #define SHADOW_BYTES_PER_BLOCK 1
  #define SHADOW_BLOCKS_PER_ROW 16
  #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  #define SHADOW_ROWS_AROUND_ADDR 2
  
  static const void *find_first_bad_addr(const void *addr, size_t size)
  {
  	u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
  	const void *first_bad_addr = addr;
  
  	while (!shadow_val && first_bad_addr < addr + size) {
  		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
  		shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
  	}
  	return first_bad_addr;
  }
  
  static void print_error_description(struct kasan_access_info *info)
  {

  	const char *bug_type = "unknown-crash";

  	u8 *shadow_addr;

  
  	info->first_bad_addr = find_first_bad_addr(info->access_addr,
  						info->access_size);

  	shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);

  	/*
  	 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
  	 * at the next shadow byte to determine the type of the bad access.
  	 */
  	if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
  		shadow_addr++;
  
  	switch (*shadow_addr) {

  	case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:

  		/*
  		 * In theory it's still possible to see these shadow values
  		 * due to a data race in the kernel code.
  		 */

  		bug_type = "out-of-bounds";

  		break;

  	case KASAN_PAGE_REDZONE:
  	case KASAN_KMALLOC_REDZONE:

  		bug_type = "slab-out-of-bounds";
  		break;

  	case KASAN_GLOBAL_REDZONE:

  		bug_type = "global-out-of-bounds";

  		break;

  	case KASAN_STACK_LEFT:
  	case KASAN_STACK_MID:
  	case KASAN_STACK_RIGHT:
  	case KASAN_STACK_PARTIAL:

  		bug_type = "stack-out-of-bounds";
  		break;
  	case KASAN_FREE_PAGE:
  	case KASAN_KMALLOC_FREE:
  		bug_type = "use-after-free";

  		break;

  	case KASAN_USE_AFTER_SCOPE:
  		bug_type = "use-after-scope";
  		break;

  	}

  	pr_err("BUG: KASAN: %s in %pS at addr %p
  ",

  		bug_type, (void *)info->ip,
  		info->access_addr);
  	pr_err("%s of size %zu by task %s/%d
  ",
  		info->is_write ? "Write" : "Read",
  		info->access_size, current->comm, task_pid_nr(current));
  }

  static inline bool kernel_or_module_addr(const void *addr)
  {

  	if (addr >= (void *)_stext && addr < (void *)_end)
  		return true;
  	if (is_module_address((unsigned long)addr))
  		return true;
  	return false;

  }
  
  static inline bool init_task_stack_addr(const void *addr)
  {
  	return addr >= (void *)&init_thread_union.stack &&
  		(addr <= (void *)&init_thread_union.stack +
  			sizeof(init_thread_union.stack));
  }

  static DEFINE_SPINLOCK(report_lock);
  
  static void kasan_start_report(unsigned long *flags)
  {
  	/*
  	 * Make sure we don't end up in loop.
  	 */
  	kasan_disable_current();
  	spin_lock_irqsave(&report_lock, *flags);
  	pr_err("==================================================================
  ");
  }
  
  static void kasan_end_report(unsigned long *flags)
  {
  	pr_err("==================================================================
  ");
  	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
  	spin_unlock_irqrestore(&report_lock, *flags);
  	kasan_enable_current();
  }

  static void print_track(struct kasan_track *track)
  {

  	pr_err("PID = %u
  ", track->pid);
  	if (track->stack) {
  		struct stack_trace trace;
  
  		depot_fetch_stack(track->stack, &trace);
  		print_stack_trace(&trace, 0);
  	} else {
  		pr_err("(stack is not available)
  ");
  	}

  }

  static void kasan_object_err(struct kmem_cache *cache, void *object)

  {
  	struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);

  
  	dump_stack();

  	pr_err("Object at %p, in cache %s size: %d
  ", object, cache->name,
  		cache->object_size);

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

  
  	pr_err("Allocated:
  ");
  	print_track(&alloc_info->alloc_track);
  	pr_err("Freed:
  ");
  	print_track(&alloc_info->free_track);

  }

  void kasan_report_double_free(struct kmem_cache *cache, void *object,
  			s8 shadow)
  {
  	unsigned long flags;
  
  	kasan_start_report(&flags);
  	pr_err("BUG: Double free or freeing an invalid pointer
  ");
  	pr_err("Unexpected shadow byte: 0x%hhX
  ", shadow);
  	kasan_object_err(cache, object);
  	kasan_end_report(&flags);
  }

  static void print_address_description(struct kasan_access_info *info)
  {

  	const void *addr = info->access_addr;
  
  	if ((addr >= (void *)PAGE_OFFSET) &&
  		(addr < high_memory)) {
  		struct page *page = virt_to_head_page(addr);

  
  		if (PageSlab(page)) {
  			void *object;
  			struct kmem_cache *cache = page->slab_cache;

  			object = nearest_obj(cache, page,
  						(void *)info->access_addr);

  			kasan_object_err(cache, object);

  			return;
  		}

  		dump_page(page, "kasan: bad access detected");
  	}

  	if (kernel_or_module_addr(addr)) {
  		if (!init_task_stack_addr(addr))
  			pr_err("Address belongs to variable %pS
  ", addr);
  	}

  	dump_stack();
  }
  
  static bool row_is_guilty(const void *row, const void *guilty)
  {
  	return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
  }
  
  static int shadow_pointer_offset(const void *row, const void *shadow)
  {
  	/* The length of ">ff00ff00ff00ff00: " is
  	 *    3 + (BITS_PER_LONG/8)*2 chars.
  	 */
  	return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
  		(shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
  }
  
  static void print_shadow_for_address(const void *addr)
  {
  	int i;
  	const void *shadow = kasan_mem_to_shadow(addr);
  	const void *shadow_row;
  
  	shadow_row = (void *)round_down((unsigned long)shadow,
  					SHADOW_BYTES_PER_ROW)
  		- SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
  
  	pr_err("Memory state around the buggy address:
  ");
  
  	for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
  		const void *kaddr = kasan_shadow_to_mem(shadow_row);
  		char buffer[4 + (BITS_PER_LONG/8)*2];

  		char shadow_buf[SHADOW_BYTES_PER_ROW];

  
  		snprintf(buffer, sizeof(buffer),
  			(i == 0) ? ">%p: " : " %p: ", kaddr);

  		/*
  		 * We should not pass a shadow pointer to generic
  		 * function, because generic functions may try to
  		 * access kasan mapping for the passed address.
  		 */

  		memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);

  		print_hex_dump(KERN_ERR, buffer,
  			DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,

  			shadow_buf, SHADOW_BYTES_PER_ROW, 0);

  
  		if (row_is_guilty(shadow_row, shadow))
  			pr_err("%*c
  ",
  				shadow_pointer_offset(shadow_row, shadow),
  				'^');
  
  		shadow_row += SHADOW_BYTES_PER_ROW;
  	}
  }

  static void kasan_report_error(struct kasan_access_info *info)

  {
  	unsigned long flags;

  	const char *bug_type;

  	kasan_start_report(&flags);

  	if (info->access_addr <
  			kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
  		if ((unsigned long)info->access_addr < PAGE_SIZE)
  			bug_type = "null-ptr-deref";
  		else if ((unsigned long)info->access_addr < TASK_SIZE)
  			bug_type = "user-memory-access";
  		else
  			bug_type = "wild-memory-access";

  		pr_err("BUG: KASAN: %s on address %p
  ",

  			bug_type, info->access_addr);
  		pr_err("%s of size %zu by task %s/%d
  ",
  			info->is_write ? "Write" : "Read",
  			info->access_size, current->comm,
  			task_pid_nr(current));
  		dump_stack();
  	} else {
  		print_error_description(info);
  		print_address_description(info);
  		print_shadow_for_address(info->first_bad_addr);
  	}

  
  	kasan_end_report(&flags);

  }
  
  void kasan_report(unsigned long addr, size_t size,
  		bool is_write, unsigned long ip)
  {
  	struct kasan_access_info info;

  	if (likely(!kasan_report_enabled()))

  		return;
  
  	info.access_addr = (void *)addr;
  	info.access_size = size;
  	info.is_write = is_write;
  	info.ip = ip;

  	kasan_report_error(&info);
  }
  
  
  #define DEFINE_ASAN_REPORT_LOAD(size)                     \
  void __asan_report_load##size##_noabort(unsigned long addr) \
  {                                                         \
  	kasan_report(addr, size, false, _RET_IP_);	  \
  }                                                         \
  EXPORT_SYMBOL(__asan_report_load##size##_noabort)
  
  #define DEFINE_ASAN_REPORT_STORE(size)                     \
  void __asan_report_store##size##_noabort(unsigned long addr) \
  {                                                          \
  	kasan_report(addr, size, true, _RET_IP_);	   \
  }                                                          \
  EXPORT_SYMBOL(__asan_report_store##size##_noabort)
  
  DEFINE_ASAN_REPORT_LOAD(1);
  DEFINE_ASAN_REPORT_LOAD(2);
  DEFINE_ASAN_REPORT_LOAD(4);
  DEFINE_ASAN_REPORT_LOAD(8);
  DEFINE_ASAN_REPORT_LOAD(16);
  DEFINE_ASAN_REPORT_STORE(1);
  DEFINE_ASAN_REPORT_STORE(2);
  DEFINE_ASAN_REPORT_STORE(4);
  DEFINE_ASAN_REPORT_STORE(8);
  DEFINE_ASAN_REPORT_STORE(16);
  
  void __asan_report_load_n_noabort(unsigned long addr, size_t size)
  {
  	kasan_report(addr, size, false, _RET_IP_);
  }
  EXPORT_SYMBOL(__asan_report_load_n_noabort);
  
  void __asan_report_store_n_noabort(unsigned long addr, size_t size)
  {
  	kasan_report(addr, size, true, _RET_IP_);
  }
  EXPORT_SYMBOL(__asan_report_store_n_noabort);