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, 35 insertions, 0 deletions

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 8fe5f162ccbc..222e86591f8a 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -113,6 +113,9 @@ enum iommufd_object_type {
 	IOMMUFD_OBJ_HW_PAGETABLE,
 	IOMMUFD_OBJ_IOAS,
 	IOMMUFD_OBJ_ACCESS,
+#ifdef CONFIG_IOMMUFD_TEST
+	IOMMUFD_OBJ_SELFTEST,
+#endif
 };
 
 /* Base struct for all objects with a userspace ID handle. */
@@ -269,4 +272,36 @@ void iopt_remove_access(struct io_pagetable *iopt,
 			struct iommufd_access *access);
 void iommufd_access_destroy_object(struct iommufd_object *obj);
 
+#ifdef CONFIG_IOMMUFD_TEST
+struct iommufd_hw_pagetable *
+iommufd_device_selftest_attach(struct iommufd_ctx *ictx,
+			       struct iommufd_ioas *ioas,
+			       struct device *mock_dev);
+void iommufd_device_selftest_detach(struct iommufd_ctx *ictx,
+				    struct iommufd_hw_pagetable *hwpt);
+int iommufd_test(struct iommufd_ucmd *ucmd);
+void iommufd_selftest_destroy(struct iommufd_object *obj);
+extern size_t iommufd_test_memory_limit;
+void iommufd_test_syz_conv_iova_id(struct iommufd_ucmd *ucmd,
+				   unsigned int ioas_id, u64 *iova, u32 *flags);
+bool iommufd_should_fail(void);
+void __init iommufd_test_init(void);
+void iommufd_test_exit(void);
+#else
+static inline void iommufd_test_syz_conv_iova_id(struct iommufd_ucmd *ucmd,
+						 unsigned int ioas_id,
+						 u64 *iova, u32 *flags)
+{
+}
+static inline bool iommufd_should_fail(void)
+{
+	return false;
+}
+static inline void __init iommufd_test_init(void)
+{
+}
+static inline void iommufd_test_exit(void)
+{
+}
+#endif
 #endif