// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright 2020 Google LLC
 */
#define _GNU_SOURCE

#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <time.h>
#include <stdbool.h>

#include "../kselftest.h"

#define EXPECT_SUCCESS 0
#define EXPECT_FAILURE 1
#define NON_OVERLAPPING 0
#define OVERLAPPING 1
#define NS_PER_SEC 1000000000ULL
#define VALIDATION_DEFAULT_THRESHOLD 4	/* 4MB */
#define VALIDATION_NO_THRESHOLD 0	/* Verify the entire region */

#ifndef MIN
#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
#define MAX(X, Y) ((X) > (Y) ? (X) : (Y))
#endif
#define SIZE_MB(m) ((size_t)m * (1024 * 1024))
#define SIZE_KB(k) ((size_t)k * 1024)

struct config {
	unsigned long long src_alignment;
	unsigned long long dest_alignment;
	unsigned long long region_size;
	int overlapping;
	unsigned int dest_preamble_size;
};

struct test {
	const char *name;
	struct config config;
	int expect_failure;
};

enum {
	_1KB = 1ULL << 10,	/* 1KB -> not page aligned */
	_4KB = 4ULL << 10,
	_8KB = 8ULL << 10,
	_1MB = 1ULL << 20,
	_2MB = 2ULL << 20,
	_4MB = 4ULL << 20,
	_5MB = 5ULL << 20,
	_1GB = 1ULL << 30,
	_2GB = 2ULL << 30,
	PMD = _2MB,
	PUD = _1GB,
};

#define PTE page_size

#define MAKE_TEST(source_align, destination_align, size,	\
		  overlaps, should_fail, test_name)		\
(struct test){							\
	.name = test_name,					\
	.config = {						\
		.src_alignment = source_align,			\
		.dest_alignment = destination_align,		\
		.region_size = size,				\
		.overlapping = overlaps,			\
	},							\
	.expect_failure = should_fail				\
}

/* compute square root using binary search */
static unsigned long get_sqrt(unsigned long val)
{
	unsigned long low = 1;

	/* assuming rand_size is less than 1TB */
	unsigned long high = (1UL << 20);

	while (low <= high) {
		unsigned long mid = low + (high - low) / 2;
		unsigned long temp = mid * mid;

		if (temp == val)
			return mid;
		if (temp < val)
			low = mid + 1;
		high = mid - 1;
	}
	return low;
}

/*
 * Returns false if the requested remap region overlaps with an
 * existing mapping (e.g text, stack) else returns true.
 */
static bool is_remap_region_valid(void *addr, unsigned long long size)
{
	void *remap_addr = NULL;
	bool ret = true;

	/* Use MAP_FIXED_NOREPLACE flag to ensure region is not mapped */
	remap_addr = mmap(addr, size, PROT_READ | PROT_WRITE,
					 MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
					 -1, 0);

	if (remap_addr == MAP_FAILED) {
		if (errno == EEXIST)
			ret = false;
	} else {
		munmap(remap_addr, size);
	}

	return ret;
}

/* Returns mmap_min_addr sysctl tunable from procfs */
static unsigned long long get_mmap_min_addr(void)
{
	FILE *fp;
	int n_matched;
	static unsigned long long addr;

	if (addr)
		return addr;

	fp = fopen("/proc/sys/vm/mmap_min_addr", "r");
	if (fp == NULL) {
		ksft_print_msg("Failed to open /proc/sys/vm/mmap_min_addr: %s\n",
			strerror(errno));
		exit(KSFT_SKIP);
	}

	n_matched = fscanf(fp, "%llu", &addr);
	if (n_matched != 1) {
		ksft_print_msg("Failed to read /proc/sys/vm/mmap_min_addr: %s\n",
			strerror(errno));
		fclose(fp);
		exit(KSFT_SKIP);
	}

	fclose(fp);
	return addr;
}

/*
 * Using /proc/self/maps, assert that the specified address range is contained
 * within a single mapping.
 */
static bool is_range_mapped(FILE *maps_fp, unsigned long start,
			    unsigned long end)
{
	char *line = NULL;
	size_t len = 0;
	bool success = false;
	unsigned long first_val, second_val;

	rewind(maps_fp);

	while (getline(&line, &len, maps_fp) != -1) {
		if (sscanf(line, "%lx-%lx", &first_val, &second_val) != 2) {
			ksft_exit_fail_msg("cannot parse /proc/self/maps\n");
			break;
		}

		if (first_val <= start && second_val >= end) {
			success = true;
			break;
		}
	}

	return success;
}

/*
 * Returns the start address of the mapping on success, else returns
 * NULL on failure.
 */
static void *get_source_mapping(struct config c)
{
	unsigned long long addr = 0ULL;
	void *src_addr = NULL;
	unsigned long long mmap_min_addr;

	mmap_min_addr = get_mmap_min_addr();
	/*
	 * For some tests, we need to not have any mappings below the
	 * source mapping. Add some headroom to mmap_min_addr for this.
	 */
	mmap_min_addr += 10 * _4MB;

retry:
	addr += c.src_alignment;
	if (addr < mmap_min_addr)
		goto retry;

	src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
					MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
					-1, 0);
	if (src_addr == MAP_FAILED) {
		if (errno == EPERM || errno == EEXIST)
			goto retry;
		goto error;
	}
	/*
	 * Check that the address is aligned to the specified alignment.
	 * Addresses which have alignments that are multiples of that
	 * specified are not considered valid. For instance, 1GB address is
	 * 2MB-aligned, however it will not be considered valid for a
	 * requested alignment of 2MB. This is done to reduce coincidental
	 * alignment in the tests.
	 */
	if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
			!((unsigned long long) src_addr & c.src_alignment)) {
		munmap(src_addr, c.region_size);
		goto retry;
	}

	if (!src_addr)
		goto error;

	return src_addr;
error:
	ksft_print_msg("Failed to map source region: %s\n",
			strerror(errno));
	return NULL;
}

/*
 * This test validates that merge is called when expanding a mapping.
 * Mapping containing three pages is created, middle page is unmapped
 * and then the mapping containing the first page is expanded so that
 * it fills the created hole. The two parts should merge creating
 * single mapping with three pages.
 */
static void mremap_expand_merge(FILE *maps_fp, unsigned long page_size)
{
	char *test_name = "mremap expand merge";
	bool success = false;
	char *remap, *start;

	start = mmap(NULL, 3 * page_size, PROT_READ | PROT_WRITE,
		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

	if (start == MAP_FAILED) {
		ksft_print_msg("mmap failed: %s\n", strerror(errno));
		goto out;
	}

	munmap(start + page_size, page_size);
	remap = mremap(start, page_size, 2 * page_size, 0);
	if (remap == MAP_FAILED) {
		ksft_print_msg("mremap failed: %s\n", strerror(errno));
		munmap(start, page_size);
		munmap(start + 2 * page_size, page_size);
		goto out;
	}

	success = is_range_mapped(maps_fp, (unsigned long)start,
				  (unsigned long)(start + 3 * page_size));
	munmap(start, 3 * page_size);

out:
	if (success)
		ksft_test_result_pass("%s\n", test_name);
	else
		ksft_test_result_fail("%s\n", test_name);
}

/*
 * Similar to mremap_expand_merge() except instead of removing the middle page,
 * we remove the last then attempt to remap offset from the second page. This
 * should result in the mapping being restored to its former state.
 */
static void mremap_expand_merge_offset(FILE *maps_fp, unsigned long page_size)
{

	char *test_name = "mremap expand merge offset";
	bool success = false;
	char *remap, *start;

	start = mmap(NULL, 3 * page_size, PROT_READ | PROT_WRITE,
		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

	if (start == MAP_FAILED) {
		ksft_print_msg("mmap failed: %s\n", strerror(errno));
		goto out;
	}

	/* Unmap final page to ensure we have space to expand. */
	munmap(start + 2 * page_size, page_size);
	remap = mremap(start + page_size, page_size, 2 * page_size, 0);
	if (remap == MAP_FAILED) {
		ksft_print_msg("mremap failed: %s\n", strerror(errno));
		munmap(start, 2 * page_size);
		goto out;
	}

	success = is_range_mapped(maps_fp, (unsigned long)start,
				  (unsigned long)(start + 3 * page_size));
	munmap(start, 3 * page_size);

out:
	if (success)
		ksft_test_result_pass("%s\n", test_name);
	else
		ksft_test_result_fail("%s\n", test_name);
}

/*
 * Verify that an mremap within a range does not cause corruption
 * of unrelated part of range.
 *
 * Consider the following range which is 2MB aligned and is
 * a part of a larger 20MB range which is not shown. Each
 * character is 256KB below making the source and destination
 * 2MB each. The lower case letters are moved (s to d) and the
 * upper case letters are not moved. The below test verifies
 * that the upper case S letters are not corrupted by the
 * adjacent mremap.
 *
 * |DDDDddddSSSSssss|
 */
static void mremap_move_within_range(unsigned int pattern_seed, char *rand_addr)
{
	char *test_name = "mremap mremap move within range";
	void *src, *dest;
	unsigned int i, success = 1;

	size_t size = SIZE_MB(20);
	void *ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
			 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if (ptr == MAP_FAILED) {
		perror("mmap");
		success = 0;
		goto out;
	}
	memset(ptr, 0, size);

	src = ptr + SIZE_MB(6);
	src = (void *)((unsigned long)src & ~(SIZE_MB(2) - 1));

	/* Set byte pattern for source block. */
	memcpy(src, rand_addr, SIZE_MB(2));

	dest = src - SIZE_MB(2);

	void *new_ptr = mremap(src + SIZE_MB(1), SIZE_MB(1), SIZE_MB(1),
						   MREMAP_MAYMOVE | MREMAP_FIXED, dest + SIZE_MB(1));
	if (new_ptr == MAP_FAILED) {
		perror("mremap");
		success = 0;
		goto out;
	}

	/* Verify byte pattern after remapping */
	srand(pattern_seed);
	for (i = 0; i < SIZE_MB(1); i++) {
		char c = (char) rand();

		if (((char *)src)[i] != c) {
			ksft_print_msg("Data at src at %d got corrupted due to unrelated mremap\n",
				       i);
			ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff,
					((char *) src)[i] & 0xff);
			success = 0;
		}
	}

out:
	if (munmap(ptr, size) == -1)
		perror("munmap");

	if (success)
		ksft_test_result_pass("%s\n", test_name);
	else
		ksft_test_result_fail("%s\n", test_name);
}

static bool is_multiple_vma_range_ok(unsigned int pattern_seed,
				     char *ptr, unsigned long page_size)
{
	int i;

	srand(pattern_seed);
	for (i = 0; i <= 10; i += 2) {
		int j;
		char *buf = &ptr[i * page_size];
		size_t size = i == 4 ? 2 * page_size : page_size;

		for (j = 0; j < size; j++) {
			char chr = rand();

			if (chr != buf[j]) {
				ksft_print_msg("page %d offset %d corrupted, expected %d got %d\n",
					       i, j, chr, buf[j]);
				return false;
			}
		}
	}

	return true;
}

static void mremap_move_multiple_vmas(unsigned int pattern_seed,
				      unsigned long page_size,
				      bool dont_unmap)
{
	int mremap_flags = MREMAP_FIXED | MREMAP_MAYMOVE;
	char *test_name = "mremap move multiple vmas";
	const size_t size = 11 * page_size;
	bool success = true;
	char *ptr, *tgt_ptr;
	int i;

	if (dont_unmap)
		mremap_flags |= MREMAP_DONTUNMAP;

	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
		   MAP_PRIVATE | MAP_ANON, -1, 0);
	if (ptr == MAP_FAILED) {
		perror("mmap");
		success = false;
		goto out;
	}

	tgt_ptr = mmap(NULL, 2 * size, PROT_READ | PROT_WRITE,
		       MAP_PRIVATE | MAP_ANON, -1, 0);
	if (tgt_ptr == MAP_FAILED) {
		perror("mmap");
		success = false;
		goto out;
	}
	if (munmap(tgt_ptr, 2 * size)) {
		perror("munmap");
		success = false;
		goto out_unmap;
	}

	/*
	 * Unmap so we end up with:
	 *
	 *  0   2   4 5 6   8   10 offset in buffer
	 * |*| |*| |*****| |*| |*|
	 * |*| |*| |*****| |*| |*|
	 *  0   1   2 3 4   5   6  pattern offset
	 */
	for (i = 1; i < 10; i += 2) {
		if (i == 5)
			continue;

		if (munmap(&ptr[i * page_size], page_size)) {
			perror("munmap");
			success = false;
			goto out_unmap;
		}
	}

	srand(pattern_seed);

	/* Set up random patterns. */
	for (i = 0; i <= 10; i += 2) {
		int j;
		size_t size = i == 4 ? 2 * page_size : page_size;
		char *buf = &ptr[i * page_size];

		for (j = 0; j < size; j++)
			buf[j] = rand();
	}

	/* First, just move the whole thing. */
	if (mremap(ptr, size, size, mremap_flags, tgt_ptr) == MAP_FAILED) {
		perror("mremap");
		success = false;
		goto out_unmap;
	}
	/* Check move was ok. */
	if (!is_multiple_vma_range_ok(pattern_seed, tgt_ptr, page_size)) {
		success = false;
		goto out_unmap;
	}

	/* Move next to itself. */
	if (mremap(tgt_ptr, size, size, mremap_flags,
		   &tgt_ptr[size]) == MAP_FAILED) {
		perror("mremap");
		success = false;
		goto out_unmap;
	}
	/* Check that the move is ok. */
	if (!is_multiple_vma_range_ok(pattern_seed, &tgt_ptr[size], page_size)) {
		success = false;
		goto out_unmap;
	}

	/* Map a range to overwrite. */
	if (mmap(tgt_ptr, size, PROT_NONE,
		 MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0) == MAP_FAILED) {
		perror("mmap tgt");
		success = false;
		goto out_unmap;
	}
	/* Move and overwrite. */
	if (mremap(&tgt_ptr[size], size, size,
		   mremap_flags, tgt_ptr) == MAP_FAILED) {
		perror("mremap");
		success = false;
		goto out_unmap;
	}
	/* Check that the move is ok. */
	if (!is_multiple_vma_range_ok(pattern_seed, tgt_ptr, page_size)) {
		success = false;
		goto out_unmap;
	}

out_unmap:
	if (munmap(tgt_ptr, 2 * size))
		perror("munmap tgt");
	if (munmap(ptr, size))
		perror("munmap src");

out:
	if (success)
		ksft_test_result_pass("%s%s\n", test_name,
				      dont_unmap ? " [dontunnmap]" : "");
	else
		ksft_test_result_fail("%s%s\n", test_name,
				      dont_unmap ? " [dontunnmap]" : "");
}

static void mremap_shrink_multiple_vmas(unsigned long page_size,
					bool inplace)
{
	char *test_name = "mremap shrink multiple vmas";
	const size_t size = 10 * page_size;
	bool success = true;
	char *ptr, *tgt_ptr;
	void *res;
	int i;

	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
		   MAP_PRIVATE | MAP_ANON, -1, 0);
	if (ptr == MAP_FAILED) {
		perror("mmap");
		success = false;
		goto out;
	}

	tgt_ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
		       MAP_PRIVATE | MAP_ANON, -1, 0);
	if (tgt_ptr == MAP_FAILED) {
		perror("mmap");
		success = false;
		goto out;
	}
	if (munmap(tgt_ptr, size)) {
		perror("munmap");
		success = false;
		goto out_unmap;
	}

	/*
	 * Unmap so we end up with:
	 *
	 *  0   2   4   6   8   10 offset in buffer
	 * |*| |*| |*| |*| |*| |*|
	 * |*| |*| |*| |*| |*| |*|
	 */
	for (i = 1; i < 10; i += 2) {
		if (munmap(&ptr[i * page_size], page_size)) {
			perror("munmap");
			success = false;
			goto out_unmap;
		}
	}

	/*
	 * Shrink in-place across multiple VMAs and gaps so we end up with:
	 *
	 *  0
	 * |*|
	 * |*|
	 */
	if (inplace)
		res = mremap(ptr, size, page_size, 0);
	else
		res = mremap(ptr, size, page_size, MREMAP_MAYMOVE | MREMAP_FIXED,
			     tgt_ptr);

	if (res == MAP_FAILED) {
		perror("mremap");
		success = false;
		goto out_unmap;
	}

out_unmap:
	if (munmap(tgt_ptr, size))
		perror("munmap tgt");
	if (munmap(ptr, size))
		perror("munmap src");
out:
	if (success)
		ksft_test_result_pass("%s%s\n", test_name,
				      inplace ? " [inplace]" : "");
	else
		ksft_test_result_fail("%s%s\n", test_name,
				      inplace ? " [inplace]" : "");
}

static void mremap_move_multiple_vmas_split(unsigned int pattern_seed,
					    unsigned long page_size,
					    bool dont_unmap)
{
	char *test_name = "mremap move multiple vmas split";
	int mremap_flags = MREMAP_FIXED | MREMAP_MAYMOVE;
	const size_t size = 10 * page_size;
	bool success = true;
	char *ptr, *tgt_ptr;
	int i;

	if (dont_unmap)
		mremap_flags |= MREMAP_DONTUNMAP;

	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
		   MAP_PRIVATE | MAP_ANON, -1, 0);
	if (ptr == MAP_FAILED) {
		perror("mmap");
		success = false;
		goto out;
	}

	tgt_ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
		       MAP_PRIVATE | MAP_ANON, -1, 0);
	if (tgt_ptr == MAP_FAILED) {
		perror("mmap");
		success = false;
		goto out;
	}
	if (munmap(tgt_ptr, size)) {
		perror("munmap");
		success = false;
		goto out_unmap;
	}

	/*
	 * Unmap so we end up with:
	 *
	 *  0 1 2 3 4 5 6 7 8 9 10 offset in buffer
	 * |**********| |*******|
	 * |**********| |*******|
	 *  0 1 2 3 4   5 6 7 8 9  pattern offset
	 */
	if (munmap(&ptr[5 * page_size], page_size)) {
		perror("munmap");
		success = false;
		goto out_unmap;
	}

	/* Set up random patterns. */
	srand(pattern_seed);
	for (i = 0; i < 10; i++) {
		int j;
		char *buf = &ptr[i * page_size];

		if (i == 5)
			continue;

		for (j = 0; j < page_size; j++)
			buf[j] = rand();
	}

	/*
	 * Move the below:
	 *
	 *      <------------->
	 *  0 1 2 3 4 5 6 7 8 9 10 offset in buffer
	 * |**********| |*******|
	 * |**********| |*******|
	 *  0 1 2 3 4   5 6 7 8 9  pattern offset
	 *
	 * Into:
	 *
	 * 0 1 2 3 4 5 6 7 offset in buffer
	 * |*****| |*****|
	 * |*****| |*****|
	 * 2 3 4   5 6 7   pattern offset
	 */
	if (mremap(&ptr[2 * page_size], size - 3 * page_size, size - 3 * page_size,
		   mremap_flags, tgt_ptr) == MAP_FAILED) {
		perror("mremap");
		success = false;
		goto out_unmap;
	}

	/* Offset into random pattern. */
	srand(pattern_seed);
	for (i = 0; i < 2 * page_size; i++)
		rand();

	/* Check pattern. */
	for (i = 0; i < 7; i++) {
		int j;
		char *buf = &tgt_ptr[i * page_size];

		if (i == 3)
			continue;

		for (j = 0; j < page_size; j++) {
			char chr = rand();

			if (chr != buf[j]) {
				ksft_print_msg("page %d offset %d corrupted, expected %d got %d\n",
					       i, j, chr, buf[j]);
				goto out_unmap;
			}
		}
	}

out_unmap:
	if (munmap(tgt_ptr, size))
		perror("munmap tgt");
	if (munmap(ptr, size))
		perror("munmap src");
out:
	if (success)
		ksft_test_result_pass("%s%s\n", test_name,
				      dont_unmap ? " [dontunnmap]" : "");
	else
		ksft_test_result_fail("%s%s\n", test_name,
				      dont_unmap ? " [dontunnmap]" : "");
}

/* Returns the time taken for the remap on success else returns -1. */
static long long remap_region(struct config c, unsigned int threshold_mb,
			      char *rand_addr)
{
	void *addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
	unsigned long long t, d;
	struct timespec t_start = {0, 0}, t_end = {0, 0};
	long long  start_ns, end_ns, align_mask, ret, offset;
	unsigned long long threshold;
	unsigned long num_chunks;

	if (threshold_mb == VALIDATION_NO_THRESHOLD)
		threshold = c.region_size;
	else
		threshold = MIN(threshold_mb * _1MB, c.region_size);

	src_addr = get_source_mapping(c);
	if (!src_addr) {
		ret = -1;
		goto out;
	}

	/* Set byte pattern for source block. */
	memcpy(src_addr, rand_addr, threshold);

	/* Mask to zero out lower bits of address for alignment */
	align_mask = ~(c.dest_alignment - 1);
	/* Offset of destination address from the end of the source region */
	offset = (c.overlapping) ? -c.dest_alignment : c.dest_alignment;
	addr = (void *) (((unsigned long long) src_addr + c.region_size
			  + offset) & align_mask);

	/* Remap after the destination block preamble. */
	addr += c.dest_preamble_size;

	/* See comment in get_source_mapping() */
	if (!((unsigned long long) addr & c.dest_alignment))
		addr = (void *) ((unsigned long long) addr | c.dest_alignment);

	/* Don't destroy existing mappings unless expected to overlap */
	while (!is_remap_region_valid(addr, c.region_size) && !c.overlapping) {
		/* Check for unsigned overflow */
		if (addr + c.dest_alignment < addr) {
			ksft_print_msg("Couldn't find a valid region to remap to\n");
			ret = -1;
			goto clean_up_src;
		}
		addr += c.dest_alignment;
	}

	if (c.dest_preamble_size) {
		dest_preamble_addr = mmap((void *) addr - c.dest_preamble_size, c.dest_preamble_size,
					  PROT_READ | PROT_WRITE,
					  MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
							-1, 0);
		if (dest_preamble_addr == MAP_FAILED) {
			ksft_print_msg("Failed to map dest preamble region: %s\n",
					strerror(errno));
			ret = -1;
			goto clean_up_src;
		}

		/* Set byte pattern for the dest preamble block. */
		memcpy(dest_preamble_addr, rand_addr, c.dest_preamble_size);
	}

	clock_gettime(CLOCK_MONOTONIC, &t_start);
	dest_addr = mremap(src_addr, c.region_size, c.region_size,
					  MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
	clock_gettime(CLOCK_MONOTONIC, &t_end);

	if (dest_addr == MAP_FAILED) {
		ksft_print_msg("mremap failed: %s\n", strerror(errno));
		ret = -1;
		goto clean_up_dest_preamble;
	}

	/*
	 * Verify byte pattern after remapping. Employ an algorithm with a
	 * square root time complexity in threshold: divide the range into
	 * chunks, if memcmp() returns non-zero, only then perform an
	 * iteration in that chunk to find the mismatch index.
	 */
	num_chunks = get_sqrt(threshold);
	for (unsigned long i = 0; i < num_chunks; ++i) {
		size_t chunk_size = threshold / num_chunks;
		unsigned long shift = i * chunk_size;

		if (!memcmp(dest_addr + shift, rand_addr + shift, chunk_size))
			continue;

		/* brute force iteration only over mismatch segment */
		for (t = shift; t < shift + chunk_size; ++t) {
			if (((char *) dest_addr)[t] != rand_addr[t]) {
				ksft_print_msg("Data after remap doesn't match at offset %llu\n",
						t);
				ksft_print_msg("Expected: %#x\t Got: %#x\n", rand_addr[t] & 0xff,
						((char *) dest_addr)[t] & 0xff);
				ret = -1;
				goto clean_up_dest;
			}
		}
	}

	/*
	 * if threshold is not divisible by num_chunks, then check the
	 * last chunk
	 */
	for (t = num_chunks * (threshold / num_chunks); t < threshold; ++t) {
		if (((char *) dest_addr)[t] != rand_addr[t]) {
			ksft_print_msg("Data after remap doesn't match at offset %llu\n",
					t);
			ksft_print_msg("Expected: %#x\t Got: %#x\n", rand_addr[t] & 0xff,
					((char *) dest_addr)[t] & 0xff);
			ret = -1;
			goto clean_up_dest;
		}
	}

	/* Verify the dest preamble byte pattern after remapping */
	if (!c.dest_preamble_size)
		goto no_preamble;

	num_chunks = get_sqrt(c.dest_preamble_size);

	for (unsigned long i = 0; i < num_chunks; ++i) {
		size_t chunk_size = c.dest_preamble_size / num_chunks;
		unsigned long shift = i * chunk_size;

		if (!memcmp(dest_preamble_addr + shift, rand_addr + shift,
			    chunk_size))
			continue;

		/* brute force iteration only over mismatched segment */
		for (d = shift; d < shift + chunk_size; ++d) {
			if (((char *) dest_preamble_addr)[d] != rand_addr[d]) {
				ksft_print_msg("Preamble data after remap doesn't match at offset %llu\n",
						d);
				ksft_print_msg("Expected: %#x\t Got: %#x\n", rand_addr[d] & 0xff,
						((char *) dest_preamble_addr)[d] & 0xff);
				ret = -1;
				goto clean_up_dest;
			}
		}
	}

	for (d = num_chunks * (c.dest_preamble_size / num_chunks); d < c.dest_preamble_size; ++d) {
		if (((char *) dest_preamble_addr)[d] != rand_addr[d]) {
			ksft_print_msg("Preamble data after remap doesn't match at offset %llu\n",
					d);
			ksft_print_msg("Expected: %#x\t Got: %#x\n", rand_addr[d] & 0xff,
					((char *) dest_preamble_addr)[d] & 0xff);
			ret = -1;
			goto clean_up_dest;
		}
	}

no_preamble:
	start_ns = t_start.tv_sec * NS_PER_SEC + t_start.tv_nsec;
	end_ns = t_end.tv_sec * NS_PER_SEC + t_end.tv_nsec;
	ret = end_ns - start_ns;

/*
 * Since the destination address is specified using MREMAP_FIXED, subsequent
 * mremap will unmap any previous mapping at the address range specified by
 * dest_addr and region_size. This significantly affects the remap time of
 * subsequent tests. So we clean up mappings after each test.
 */
clean_up_dest:
	munmap(dest_addr, c.region_size);
clean_up_dest_preamble:
	if (c.dest_preamble_size && dest_preamble_addr)
		munmap(dest_preamble_addr, c.dest_preamble_size);
clean_up_src:
	munmap(src_addr, c.region_size);
out:
	return ret;
}

/*
 * Verify that an mremap aligning down does not destroy
 * the beginning of the mapping just because the aligned
 * down address landed on a mapping that maybe does not exist.
 */
static void mremap_move_1mb_from_start(unsigned int pattern_seed,
				       char *rand_addr)
{
	char *test_name = "mremap move 1mb from start at 1MB+256KB aligned src";
	void *src = NULL, *dest = NULL;
	unsigned int i, success = 1;

	/* Config to reuse get_source_mapping() to do an aligned mmap. */
	struct config c = {
		.src_alignment = SIZE_MB(1) + SIZE_KB(256),
		.region_size = SIZE_MB(6)
	};

	src = get_source_mapping(c);
	if (!src) {
		success = 0;
		goto out;
	}

	c.src_alignment = SIZE_MB(1) + SIZE_KB(256);
	dest = get_source_mapping(c);
	if (!dest) {
		success = 0;
		goto out;
	}

	/* Set byte pattern for source block. */
	memcpy(src, rand_addr, SIZE_MB(2));

	/*
	 * Unmap the beginning of dest so that the aligned address
	 * falls on no mapping.
	 */
	munmap(dest, SIZE_MB(1));

	void *new_ptr = mremap(src + SIZE_MB(1), SIZE_MB(1), SIZE_MB(1),
						   MREMAP_MAYMOVE | MREMAP_FIXED, dest + SIZE_MB(1));
	if (new_ptr == MAP_FAILED) {
		perror("mremap");
		success = 0;
		goto out;
	}

	/* Verify byte pattern after remapping */
	srand(pattern_seed);
	for (i = 0; i < SIZE_MB(1); i++) {
		char c = (char) rand();

		if (((char *)src)[i] != c) {
			ksft_print_msg("Data at src at %d got corrupted due to unrelated mremap\n",
				       i);
			ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff,
					((char *) src)[i] & 0xff);
			success = 0;
		}
	}

out:
	if (src && munmap(src, c.region_size) == -1)
		perror("munmap src");

	if (dest && munmap(dest, c.region_size) == -1)
		perror("munmap dest");

	if (success)
		ksft_test_result_pass("%s\n", test_name);
	else
		ksft_test_result_fail("%s\n", test_name);
}

static void run_mremap_test_case(struct test test_case, int *failures,
				 unsigned int threshold_mb,
				 char *rand_addr)
{
	long long remap_time = remap_region(test_case.config, threshold_mb,
					    rand_addr);

	if (remap_time < 0) {
		if (test_case.expect_failure)
			ksft_test_result_xfail("%s\n\tExpected mremap failure\n",
					      test_case.name);
		else {
			ksft_test_result_fail("%s\n", test_case.name);
			*failures += 1;
		}
	} else {
		/*
		 * Comparing mremap time is only applicable if entire region
		 * was faulted in.
		 */
		if (threshold_mb == VALIDATION_NO_THRESHOLD ||
		    test_case.config.region_size <= threshold_mb * _1MB)
			ksft_test_result_pass("%s\n\tmremap time: %12lldns\n",
					      test_case.name, remap_time);
		else
			ksft_test_result_pass("%s\n", test_case.name);
	}
}

static void usage(const char *cmd)
{
	fprintf(stderr,
		"Usage: %s [[-t <threshold_mb>] [-p <pattern_seed>]]\n"
		"-t\t only validate threshold_mb of the remapped region\n"
		"  \t if 0 is supplied no threshold is used; all tests\n"
		"  \t are run and remapped regions validated fully.\n"
		"  \t The default threshold used is 4MB.\n"
		"-p\t provide a seed to generate the random pattern for\n"
		"  \t validating the remapped region.\n", cmd);
}

static int parse_args(int argc, char **argv, unsigned int *threshold_mb,
		      unsigned int *pattern_seed)
{
	const char *optstr = "t:p:";
	int opt;

	while ((opt = getopt(argc, argv, optstr)) != -1) {
		switch (opt) {
		case 't':
			*threshold_mb = atoi(optarg);
			break;
		case 'p':
			*pattern_seed = atoi(optarg);
			break;
		default:
			usage(argv[0]);
			return -1;
		}
	}

	if (optind < argc) {
		usage(argv[0]);
		return -1;
	}

	return 0;
}

#define MAX_TEST 15
#define MAX_PERF_TEST 3
int main(int argc, char **argv)
{
	int failures = 0;
	unsigned int i;
	int run_perf_tests;
	unsigned int threshold_mb = VALIDATION_DEFAULT_THRESHOLD;

	/* hard-coded test configs */
	size_t max_test_variable_region_size = _2GB;
	size_t max_test_constant_region_size = _2MB;
	size_t dest_preamble_size = 10 * _4MB;

	unsigned int pattern_seed;
	char *rand_addr;
	size_t rand_size;
	int num_expand_tests = 2;
	int num_misc_tests = 8;
	struct test test_cases[MAX_TEST] = {};
	struct test perf_test_cases[MAX_PERF_TEST];
	int page_size;
	time_t t;
	FILE *maps_fp;

	pattern_seed = (unsigned int) time(&t);

	if (parse_args(argc, argv, &threshold_mb, &pattern_seed) < 0)
		exit(EXIT_FAILURE);

	ksft_print_msg("Test configs:\n\tthreshold_mb=%u\n\tpattern_seed=%u\n\n",
		       threshold_mb, pattern_seed);

	/*
	 * set preallocated random array according to test configs; see the
	 * functions for the logic of setting the size
	 */
	if (!threshold_mb)
		rand_size = MAX(max_test_variable_region_size,
				max_test_constant_region_size);
	else
		rand_size = MAX(MIN(threshold_mb * _1MB,
				    max_test_variable_region_size),
				max_test_constant_region_size);
	rand_size = MAX(dest_preamble_size, rand_size);

	rand_addr = (char *)mmap(NULL, rand_size, PROT_READ | PROT_WRITE,
				 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if (rand_addr == MAP_FAILED) {
		perror("mmap");
		ksft_exit_fail_msg("cannot mmap rand_addr\n");
	}

	/* fill stream of random bytes */
	srand(pattern_seed);
	for (unsigned long i = 0; i < rand_size; ++i)
		rand_addr[i] = (char) rand();

	page_size = sysconf(_SC_PAGESIZE);

	/* Expected mremap failures */
	test_cases[0] =	MAKE_TEST(page_size, page_size, page_size,
				  OVERLAPPING, EXPECT_FAILURE,
				  "mremap - Source and Destination Regions Overlapping");

	test_cases[1] = MAKE_TEST(page_size, page_size/4, page_size,
				  NON_OVERLAPPING, EXPECT_FAILURE,
				  "mremap - Destination Address Misaligned (1KB-aligned)");
	test_cases[2] = MAKE_TEST(page_size/4, page_size, page_size,
				  NON_OVERLAPPING, EXPECT_FAILURE,
				  "mremap - Source Address Misaligned (1KB-aligned)");

	/* Src addr PTE aligned */
	test_cases[3] = MAKE_TEST(PTE, PTE, PTE * 2,
				  NON_OVERLAPPING, EXPECT_SUCCESS,
				  "8KB mremap - Source PTE-aligned, Destination PTE-aligned");

	/* Src addr 1MB aligned */
	test_cases[4] = MAKE_TEST(_1MB, PTE, _2MB, NON_OVERLAPPING, EXPECT_SUCCESS,
				  "2MB mremap - Source 1MB-aligned, Destination PTE-aligned");
	test_cases[5] = MAKE_TEST(_1MB, _1MB, _2MB, NON_OVERLAPPING, EXPECT_SUCCESS,
				  "2MB mremap - Source 1MB-aligned, Destination 1MB-aligned");

	/* Src addr PMD aligned */
	test_cases[6] = MAKE_TEST(PMD, PTE, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
				  "4MB mremap - Source PMD-aligned, Destination PTE-aligned");
	test_cases[7] =	MAKE_TEST(PMD, _1MB, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
				  "4MB mremap - Source PMD-aligned, Destination 1MB-aligned");
	test_cases[8] = MAKE_TEST(PMD, PMD, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
				  "4MB mremap - Source PMD-aligned, Destination PMD-aligned");

	/* Src addr PUD aligned */
	test_cases[9] = MAKE_TEST(PUD, PTE, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
				  "2GB mremap - Source PUD-aligned, Destination PTE-aligned");
	test_cases[10] = MAKE_TEST(PUD, _1MB, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
				   "2GB mremap - Source PUD-aligned, Destination 1MB-aligned");
	test_cases[11] = MAKE_TEST(PUD, PMD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
				   "2GB mremap - Source PUD-aligned, Destination PMD-aligned");
	test_cases[12] = MAKE_TEST(PUD, PUD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
				   "2GB mremap - Source PUD-aligned, Destination PUD-aligned");

	/* Src and Dest addr 1MB aligned. 5MB mremap. */
	test_cases[13] = MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SUCCESS,
				  "5MB mremap - Source 1MB-aligned, Destination 1MB-aligned");

	/* Src and Dest addr 1MB aligned. 5MB mremap. */
	test_cases[14] = MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SUCCESS,
				  "5MB mremap - Source 1MB-aligned, Dest 1MB-aligned with 40MB Preamble");
	test_cases[14].config.dest_preamble_size = 10 * _4MB;

	perf_test_cases[0] =  MAKE_TEST(page_size, page_size, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
					"1GB mremap - Source PTE-aligned, Destination PTE-aligned");
	/*
	 * mremap 1GB region - Page table level aligned time
	 * comparison.
	 */
	perf_test_cases[1] = MAKE_TEST(PMD, PMD, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
				       "1GB mremap - Source PMD-aligned, Destination PMD-aligned");
	perf_test_cases[2] = MAKE_TEST(PUD, PUD, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
				       "1GB mremap - Source PUD-aligned, Destination PUD-aligned");

	run_perf_tests =  (threshold_mb == VALIDATION_NO_THRESHOLD) ||
				(threshold_mb * _1MB >= _1GB);

	ksft_set_plan(ARRAY_SIZE(test_cases) + (run_perf_tests ?
		      ARRAY_SIZE(perf_test_cases) : 0) + num_expand_tests + num_misc_tests);

	for (i = 0; i < ARRAY_SIZE(test_cases); i++)
		run_mremap_test_case(test_cases[i], &failures, threshold_mb,
				     rand_addr);

	maps_fp = fopen("/proc/self/maps", "r");

	if (maps_fp == NULL) {
		munmap(rand_addr, rand_size);
		ksft_exit_fail_msg("Failed to read /proc/self/maps: %s\n", strerror(errno));
	}

	mremap_expand_merge(maps_fp, page_size);
	mremap_expand_merge_offset(maps_fp, page_size);

	fclose(maps_fp);

	mremap_move_within_range(pattern_seed, rand_addr);
	mremap_move_1mb_from_start(pattern_seed, rand_addr);
	mremap_shrink_multiple_vmas(page_size, /* inplace= */true);
	mremap_shrink_multiple_vmas(page_size, /* inplace= */false);
	mremap_move_multiple_vmas(pattern_seed, page_size, /* dontunmap= */ false);
	mremap_move_multiple_vmas(pattern_seed, page_size, /* dontunmap= */ true);
	mremap_move_multiple_vmas_split(pattern_seed, page_size, /* dontunmap= */ false);
	mremap_move_multiple_vmas_split(pattern_seed, page_size, /* dontunmap= */ true);

	if (run_perf_tests) {
		ksft_print_msg("\n%s\n",
		 "mremap HAVE_MOVE_PMD/PUD optimization time comparison for 1GB region:");
		for (i = 0; i < ARRAY_SIZE(perf_test_cases); i++)
			run_mremap_test_case(perf_test_cases[i], &failures,
					     threshold_mb,
					     rand_addr);
	}

	munmap(rand_addr, rand_size);

	if (failures > 0)
		ksft_exit_fail();
	else
		ksft_exit_pass();
}