#include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/string.h>
  #include <linux/types.h>
  #include <linux/mm.h>
  #include <linux/smp.h>
  #include <linux/init.h>
  #include <linux/pfn.h>

  #include <linux/memblock.h>

  static u64 patterns[] __initdata = {

  	/* The first entry has to be 0 to leave memtest with zeroed memory */

  	0,
  	0xffffffffffffffffULL,
  	0x5555555555555555ULL,
  	0xaaaaaaaaaaaaaaaaULL,

  	0x1111111111111111ULL,
  	0x2222222222222222ULL,
  	0x4444444444444444ULL,
  	0x8888888888888888ULL,
  	0x3333333333333333ULL,
  	0x6666666666666666ULL,
  	0x9999999999999999ULL,
  	0xccccccccccccccccULL,
  	0x7777777777777777ULL,
  	0xbbbbbbbbbbbbbbbbULL,
  	0xddddddddddddddddULL,
  	0xeeeeeeeeeeeeeeeeULL,
  	0x7a6c7258554e494cULL, /* yeah ;-) */

  };

  static void __init reserve_bad_mem(u64 pattern, phys_addr_t start_bad, phys_addr_t end_bad)

  {

  	printk(KERN_INFO "  %016llx bad mem addr %010llx - %010llx reserved
  ",
  	       (unsigned long long) pattern,
  	       (unsigned long long) start_bad,
  	       (unsigned long long) end_bad);

  	memblock_reserve(start_bad, end_bad - start_bad);

  }

  static void __init memtest(u64 pattern, phys_addr_t start_phys, phys_addr_t size)

  {

  	u64 *p, *start, *end;

  	phys_addr_t start_bad, last_bad;
  	phys_addr_t start_phys_aligned;

  	const size_t incr = sizeof(pattern);

  	start_phys_aligned = ALIGN(start_phys, incr);

  	start = __va(start_phys_aligned);

  	end = start + (size - (start_phys_aligned - start_phys)) / incr;

  	start_bad = 0;
  	last_bad = 0;

  	for (p = start; p < end; p++)
  		*p = pattern;

  	for (p = start; p < end; p++, start_phys_aligned += incr) {
  		if (*p == pattern)

  			continue;
  		if (start_phys_aligned == last_bad + incr) {
  			last_bad += incr;
  			continue;

  		}

  		if (start_bad)
  			reserve_bad_mem(pattern, start_bad, last_bad + incr);
  		start_bad = last_bad = start_phys_aligned;

  	}

  	if (start_bad)
  		reserve_bad_mem(pattern, start_bad, last_bad + incr);

  }

  static void __init do_one_pass(u64 pattern, phys_addr_t start, phys_addr_t end)

  {

  	u64 i;
  	phys_addr_t this_start, this_end;

  	for_each_free_mem_range(i, NUMA_NO_NODE, &this_start, &this_end, NULL) {

  		this_start = clamp(this_start, start, end);
  		this_end = clamp(this_end, start, end);

  		if (this_start < this_end) {
  			printk(KERN_INFO "  %010llx - %010llx pattern %016llx
  ",
  			       (unsigned long long)this_start,
  			       (unsigned long long)this_end,
  			       (unsigned long long)cpu_to_be64(pattern));
  			memtest(pattern, this_start, this_end - this_start);
  		}

  	}
  }

  /* default is disabled */
  static int memtest_pattern __initdata;
  
  static int __init parse_memtest(char *arg)
  {
  	if (arg)
  		memtest_pattern = simple_strtoul(arg, NULL, 0);

  	else
  		memtest_pattern = ARRAY_SIZE(patterns);

  	return 0;
  }
  
  early_param("memtest", parse_memtest);

  void __init early_memtest(phys_addr_t start, phys_addr_t end)

  {

  	unsigned int i;

  	unsigned int idx = 0;

  
  	if (!memtest_pattern)
  		return;

  	printk(KERN_INFO "early_memtest: # of tests: %d
  ", memtest_pattern);

  	for (i = memtest_pattern-1; i < UINT_MAX; --i) {

  		idx = i % ARRAY_SIZE(patterns);
  		do_one_pass(patterns[idx], start, end);
  	}

  }