xref: /haiku/src/tests/system/kernel/mmap_cut_tests.cpp (revision c0a12a6b7d697382511ff36e7815aad6a379b3a7)

/*
 * Copyright 2023, Haiku, Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <OS.h>


int gTestFd = -1;


int
map_negative_offset_test()
{
	// should fail (negative offset)
	void* ptr = mmap(NULL, B_PAGE_SIZE, PROT_READ, MAP_PRIVATE, gTestFd, -4096);
	if (ptr != MAP_FAILED) {
		printf("map-negative-offset unexpectedly succeeded!\n");
		return -1;
	}
	return 0;
}


int
map_cut_compare_test()
{
	uint8* ptr1 = (uint8*)mmap(NULL, 16 * B_PAGE_SIZE, PROT_READ, MAP_PRIVATE, gTestFd, 0);
	uint8 chunk[128];
	memcpy(chunk, &ptr1[3 * B_PAGE_SIZE], sizeof(chunk));

	// now cut the area
	uint8* ptr2 = (uint8*)mmap(&ptr1[B_PAGE_SIZE], B_PAGE_SIZE,
		PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0);

	// validate that the area after the cut still has the expected data
	int status = memcmp(&ptr1[3 * B_PAGE_SIZE], chunk, sizeof(chunk));
	if (status != 0) {
		printf("map-cut-compare test failed!\n");
		return status;
	}
	return 0;
}


int
map_protect_cut_test()
{
	uint8* ptr = (uint8*)mmap(NULL, B_PAGE_SIZE * 4, PROT_NONE,
		MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

	// make the tail accessible
	mprotect(ptr + B_PAGE_SIZE * 3, B_PAGE_SIZE, PROT_READ | PROT_WRITE);

	// store any value
	ptr[B_PAGE_SIZE * 3] = 'a';

	// cut the area in the middle, before the accessible tail
	mmap(ptr + B_PAGE_SIZE, B_PAGE_SIZE, PROT_READ | PROT_WRITE,
		MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);

	// validate that this does not crash
	if (ptr[B_PAGE_SIZE * 3] != 'a') {
		printf("map-protect-cut test failed!\n");
		return -1;
	}
	return 0;
}


int
map_cut_fork_test()
{
	char name[24];
	sprintf(name, "/shm-mmap-cut-fork-test-%d", getpid());
	name[sizeof(name) - 1] = '\0';
	shm_unlink(name);
	int fd = shm_open(name, O_RDWR | O_CREAT | O_EXCL | O_NOFOLLOW, 0600);
	shm_unlink(name);

	if (fd < 0) {
		printf("failed to create temporary file!\n");
		return fd;
	}

	ftruncate(fd, B_PAGE_SIZE * 4);

	uint8* ptr = (uint8*)mmap(NULL, B_PAGE_SIZE * 4, PROT_NONE, MAP_PRIVATE,
		fd, 0);

	// we can close the FD as mmap acquires another reference to the vnode
	close(fd);

	// make the head accessible and also force the kernel to allocate the
	// page_protections array
	mprotect(ptr, B_PAGE_SIZE, PROT_READ | PROT_WRITE);

	// store any value
	ptr[0] = 'a';

	// cut the area in the middle
	mmap(ptr + B_PAGE_SIZE, B_PAGE_SIZE, PROT_NONE,
		MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);

	// validate that the fork does not crash the kernel
	int pid = fork();

	if (pid == 0)
	{
		exit(0);
	}
	else if (pid < 0)
	{
		printf("failed to fork the test process!\n");
		return pid;
	}

	int status;
	waitpid(pid, &status, 0);

	// validate that this does not crash
	if (ptr[0] != 'a') {
		printf("map-cut-fork test failed!\n");
		return -1;
	}
	return 0;
}


int
main()
{
	gTestFd = open("/boot/system/lib/libroot.so", O_CLOEXEC | O_RDONLY);
	if (gTestFd < 0)
		return -1;

	int status;

	if ((status = map_negative_offset_test()) != 0)
		return status;

	if ((status = map_cut_compare_test()) != 0)
		return status;

	if ((status = map_protect_cut_test()) != 0)
		return status;

	if ((status = map_cut_fork_test()) != 0)
		return status;

	return 0;
}