linux-net/tools/testing/selftests/kvm/guest_memfd_test.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright Intel Corporation, 2023
 *
 * Author: Chao Peng <chao.p.peng@linux.intel.com>
 */
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>

#include <linux/bitmap.h>
#include <linux/falloc.h>
#include <linux/sizes.h>
#include <setjmp.h>
#include <signal.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "kvm_util.h"
#include "test_util.h"
#include "ucall_common.h"

static void test_file_read_write(int fd)
{
	char buf[64];

	TEST_ASSERT(read(fd, buf, sizeof(buf)) < 0,
		    "read on a guest_mem fd should fail");
	TEST_ASSERT(write(fd, buf, sizeof(buf)) < 0,
		    "write on a guest_mem fd should fail");
	TEST_ASSERT(pread(fd, buf, sizeof(buf), 0) < 0,
		    "pread on a guest_mem fd should fail");
	TEST_ASSERT(pwrite(fd, buf, sizeof(buf), 0) < 0,
		    "pwrite on a guest_mem fd should fail");
}

static void test_mmap_supported(int fd, size_t page_size, size_t total_size)
{
	const char val = 0xaa;
	char *mem;
	size_t i;
	int ret;

	mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
	TEST_ASSERT(mem == MAP_FAILED, "Copy-on-write not allowed by guest_memfd.");

	mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	TEST_ASSERT(mem != MAP_FAILED, "mmap() for guest_memfd should succeed.");

	memset(mem, val, total_size);
	for (i = 0; i < total_size; i++)
		TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0,
			page_size);
	TEST_ASSERT(!ret, "fallocate the first page should succeed.");

	for (i = 0; i < page_size; i++)
		TEST_ASSERT_EQ(READ_ONCE(mem[i]), 0x00);
	for (; i < total_size; i++)
		TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);

	memset(mem, val, page_size);
	for (i = 0; i < total_size; i++)
		TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);

	ret = munmap(mem, total_size);
	TEST_ASSERT(!ret, "munmap() should succeed.");
}

static sigjmp_buf jmpbuf;
void fault_sigbus_handler(int signum)
{
	siglongjmp(jmpbuf, 1);
}

static void test_fault_overflow(int fd, size_t page_size, size_t total_size)
{
	struct sigaction sa_old, sa_new = {
		.sa_handler = fault_sigbus_handler,
	};
	size_t map_size = total_size * 4;
	const char val = 0xaa;
	char *mem;
	size_t i;
	int ret;

	mem = mmap(NULL, map_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	TEST_ASSERT(mem != MAP_FAILED, "mmap() for guest_memfd should succeed.");

	sigaction(SIGBUS, &sa_new, &sa_old);
	if (sigsetjmp(jmpbuf, 1) == 0) {
		memset(mem, 0xaa, map_size);
		TEST_ASSERT(false, "memset() should have triggered SIGBUS.");
	}
	sigaction(SIGBUS, &sa_old, NULL);

	for (i = 0; i < total_size; i++)
		TEST_ASSERT_EQ(READ_ONCE(mem[i]), val);

	ret = munmap(mem, map_size);
	TEST_ASSERT(!ret, "munmap() should succeed.");
}

static void test_mmap_not_supported(int fd, size_t page_size, size_t total_size)
{
	char *mem;

	mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	TEST_ASSERT_EQ(mem, MAP_FAILED);

	mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	TEST_ASSERT_EQ(mem, MAP_FAILED);
}

static void test_file_size(int fd, size_t page_size, size_t total_size)
{
	struct stat sb;
	int ret;

	ret = fstat(fd, &sb);
	TEST_ASSERT(!ret, "fstat should succeed");
	TEST_ASSERT_EQ(sb.st_size, total_size);
	TEST_ASSERT_EQ(sb.st_blksize, page_size);
}

static void test_fallocate(int fd, size_t page_size, size_t total_size)
{
	int ret;

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, total_size);
	TEST_ASSERT(!ret, "fallocate with aligned offset and size should succeed");

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
			page_size - 1, page_size);
	TEST_ASSERT(ret, "fallocate with unaligned offset should fail");

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, total_size, page_size);
	TEST_ASSERT(ret, "fallocate beginning at total_size should fail");

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, total_size + page_size, page_size);
	TEST_ASSERT(ret, "fallocate beginning after total_size should fail");

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
			total_size, page_size);
	TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) at total_size should succeed");

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
			total_size + page_size, page_size);
	TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) after total_size should succeed");

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
			page_size, page_size - 1);
	TEST_ASSERT(ret, "fallocate with unaligned size should fail");

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
			page_size, page_size);
	TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) with aligned offset and size should succeed");

	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, page_size, page_size);
	TEST_ASSERT(!ret, "fallocate to restore punched hole should succeed");
}

static void test_invalid_punch_hole(int fd, size_t page_size, size_t total_size)
{
	struct {
		off_t offset;
		off_t len;
	} testcases[] = {
		{0, 1},
		{0, page_size - 1},
		{0, page_size + 1},

		{1, 1},
		{1, page_size - 1},
		{1, page_size},
		{1, page_size + 1},

		{page_size, 1},
		{page_size, page_size - 1},
		{page_size, page_size + 1},
	};
	int ret, i;

	for (i = 0; i < ARRAY_SIZE(testcases); i++) {
		ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
				testcases[i].offset, testcases[i].len);
		TEST_ASSERT(ret == -1 && errno == EINVAL,
			    "PUNCH_HOLE with !PAGE_SIZE offset (%lx) and/or length (%lx) should fail",
			    testcases[i].offset, testcases[i].len);
	}
}

static void test_create_guest_memfd_invalid_sizes(struct kvm_vm *vm,
						  uint64_t guest_memfd_flags,
						  size_t page_size)
{
	size_t size;
	int fd;

	for (size = 1; size < page_size; size++) {
		fd = __vm_create_guest_memfd(vm, size, guest_memfd_flags);
		TEST_ASSERT(fd < 0 && errno == EINVAL,
			    "guest_memfd() with non-page-aligned page size '0x%lx' should fail with EINVAL",
			    size);
	}
}

static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
{
	int fd1, fd2, ret;
	struct stat st1, st2;
	size_t page_size = getpagesize();

	fd1 = __vm_create_guest_memfd(vm, page_size, 0);
	TEST_ASSERT(fd1 != -1, "memfd creation should succeed");

	ret = fstat(fd1, &st1);
	TEST_ASSERT(ret != -1, "memfd fstat should succeed");
	TEST_ASSERT(st1.st_size == page_size, "memfd st_size should match requested size");

	fd2 = __vm_create_guest_memfd(vm, page_size * 2, 0);
	TEST_ASSERT(fd2 != -1, "memfd creation should succeed");

	ret = fstat(fd2, &st2);
	TEST_ASSERT(ret != -1, "memfd fstat should succeed");
	TEST_ASSERT(st2.st_size == page_size * 2, "second memfd st_size should match requested size");

	ret = fstat(fd1, &st1);
	TEST_ASSERT(ret != -1, "memfd fstat should succeed");
	TEST_ASSERT(st1.st_size == page_size, "first memfd st_size should still match requested size");
	TEST_ASSERT(st1.st_ino != st2.st_ino, "different memfd should have different inode numbers");

	close(fd2);
	close(fd1);
}

static void test_guest_memfd_flags(struct kvm_vm *vm)
{
	uint64_t valid_flags = vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS);
	size_t page_size = getpagesize();
	uint64_t flag;
	int fd;

	for (flag = BIT(0); flag; flag <<= 1) {
		fd = __vm_create_guest_memfd(vm, page_size, flag);
		if (flag & valid_flags) {
			TEST_ASSERT(fd >= 0,
				    "guest_memfd() with flag '0x%lx' should succeed",
				    flag);
			close(fd);
		} else {
			TEST_ASSERT(fd < 0 && errno == EINVAL,
				    "guest_memfd() with flag '0x%lx' should fail with EINVAL",
				    flag);
		}
	}
}

static void test_guest_memfd(unsigned long vm_type)
{
	struct kvm_vm *vm;
	size_t total_size;
	size_t page_size;
	uint64_t flags;
	int fd;

	page_size = getpagesize();
	total_size = page_size * 4;

	vm = vm_create_barebones_type(vm_type);
	flags = vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS);

	/* This test doesn't yet support testing mmap() on private memory. */
	if (!(flags & GUEST_MEMFD_FLAG_INIT_SHARED))
		flags &= ~GUEST_MEMFD_FLAG_MMAP;

	test_create_guest_memfd_multiple(vm);
	test_create_guest_memfd_invalid_sizes(vm, flags, page_size);

	fd = vm_create_guest_memfd(vm, total_size, flags);

	test_file_read_write(fd);

	if (flags & GUEST_MEMFD_FLAG_MMAP) {
		test_mmap_supported(fd, page_size, total_size);
		test_fault_overflow(fd, page_size, total_size);
	} else {
		test_mmap_not_supported(fd, page_size, total_size);
	}

	test_file_size(fd, page_size, total_size);
	test_fallocate(fd, page_size, total_size);
	test_invalid_punch_hole(fd, page_size, total_size);

	test_guest_memfd_flags(vm);

	close(fd);
	kvm_vm_free(vm);
}

static void guest_code(uint8_t *mem, uint64_t size)
{
	size_t i;

	for (i = 0; i < size; i++)
		__GUEST_ASSERT(mem[i] == 0xaa,
			       "Guest expected 0xaa at offset %lu, got 0x%x", i, mem[i]);

	memset(mem, 0xff, size);
	GUEST_DONE();
}

static void test_guest_memfd_guest(void)
{
	/*
	 * Skip the first 4gb and slot0.  slot0 maps <1gb and is used to back
	 * the guest's code, stack, and page tables, and low memory contains
	 * the PCI hole and other MMIO regions that need to be avoided.
	 */
	const uint64_t gpa = SZ_4G;
	const int slot = 1;

	struct kvm_vcpu *vcpu;
	struct kvm_vm *vm;
	uint8_t *mem;
	size_t size;
	int fd, i;

	if (!kvm_check_cap(KVM_CAP_GUEST_MEMFD_FLAGS))
		return;

	vm = __vm_create_shape_with_one_vcpu(VM_SHAPE_DEFAULT, &vcpu, 1, guest_code);

	TEST_ASSERT(vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS) & GUEST_MEMFD_FLAG_MMAP,
		    "Default VM type should support MMAP, supported flags = 0x%x",
		    vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS));
	TEST_ASSERT(vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS) & GUEST_MEMFD_FLAG_INIT_SHARED,
		    "Default VM type should support INIT_SHARED, supported flags = 0x%x",
		    vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS));

	size = vm->page_size;
	fd = vm_create_guest_memfd(vm, size, GUEST_MEMFD_FLAG_MMAP |
					     GUEST_MEMFD_FLAG_INIT_SHARED);
	vm_set_user_memory_region2(vm, slot, KVM_MEM_GUEST_MEMFD, gpa, size, NULL, fd, 0);

	mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	TEST_ASSERT(mem != MAP_FAILED, "mmap() on guest_memfd failed");
	memset(mem, 0xaa, size);
	munmap(mem, size);

	virt_pg_map(vm, gpa, gpa);
	vcpu_args_set(vcpu, 2, gpa, size);
	vcpu_run(vcpu);

	TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_DONE);

	mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	TEST_ASSERT(mem != MAP_FAILED, "mmap() on guest_memfd failed");
	for (i = 0; i < size; i++)
		TEST_ASSERT_EQ(mem[i], 0xff);

	close(fd);
	kvm_vm_free(vm);
}

int main(int argc, char *argv[])
{
	unsigned long vm_types, vm_type;

	TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));

	/*
	 * Not all architectures support KVM_CAP_VM_TYPES. However, those that
	 * support guest_memfd have that support for the default VM type.
	 */
	vm_types = kvm_check_cap(KVM_CAP_VM_TYPES);
	if (!vm_types)
		vm_types = BIT(VM_TYPE_DEFAULT);

	for_each_set_bit(vm_type, &vm_types, BITS_PER_TYPE(vm_types))
		test_guest_memfd(vm_type);

	test_guest_memfd_guest();
}