iommufd: Add kernel support for testing iommufd

Provide a mock kernel module for the iommu_domain that allows it to run
without any HW and the mocking provides a way to directly validate that
the PFNs loaded into the iommu_domain are correct. This exposes the access
kAPI toward userspace to allow userspace to explore the functionality of
pages.c and io_pagetable.c

The mock also simulates the rare case of PAGE_SIZE > iommu page size as
the mock will operate at a 2K iommu page size. This allows exercising all
of the calculations to support this mismatch.

This is also intended to support syzkaller exploring the same space.

However, it is an unusually invasive config option to enable all of
this. The config option should not be enabled in a production kernel.

Link: https://lore.kernel.org/r/16-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com> # s390
Tested-by: Eric Auger <eric.auger@redhat.com> # aarch64
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 5cf69c4d591d..7c8f40bc8d98 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -19,6 +19,7 @@
 #include <linux/iommufd.h>
 
 #include "iommufd_private.h"
+#include "iommufd_test.h"
 
 struct iommufd_object_ops {
 	void (*destroy)(struct iommufd_object *obj);
@@ -239,6 +240,9 @@ union ucmd_buffer {
 	struct iommu_ioas_iova_ranges iova_ranges;
 	struct iommu_ioas_map map;
 	struct iommu_ioas_unmap unmap;
+#ifdef CONFIG_IOMMUFD_TEST
+	struct iommu_test_cmd test;
+#endif
 };
 
 struct iommufd_ioctl_op {
@@ -275,6 +279,9 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
 		 val64),
 	IOCTL_OP(IOMMU_VFIO_IOAS, iommufd_vfio_ioas, struct iommu_vfio_ioas,
 		 __reserved),
+#ifdef CONFIG_IOMMUFD_TEST
+	IOCTL_OP(IOMMU_TEST_CMD, iommufd_test, struct iommu_test_cmd, last),
+#endif
 };
 
 static long iommufd_fops_ioctl(struct file *filp, unsigned int cmd,
@@ -375,6 +382,11 @@ static const struct iommufd_object_ops iommufd_object_ops[] = {
 	[IOMMUFD_OBJ_HW_PAGETABLE] = {
 		.destroy = iommufd_hw_pagetable_destroy,
 	},
+#ifdef CONFIG_IOMMUFD_TEST
+	[IOMMUFD_OBJ_SELFTEST] = {
+		.destroy = iommufd_selftest_destroy,
+	},
+#endif
 };
 
 static struct miscdevice iommu_misc_dev = {
@@ -392,11 +404,13 @@ static int __init iommufd_init(void)
 	ret = misc_register(&iommu_misc_dev);
 	if (ret)
 		return ret;
+	iommufd_test_init();
 	return 0;
 }
 
 static void __exit iommufd_exit(void)
 {
+	iommufd_test_exit();
 	misc_deregister(&iommu_misc_dev);
 }