Commit f4b20bb3 authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

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: default avatarJason Gunthorpe <jgg@nvidia.com>
parent d624d665

drivers/iommu/iommufd/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -10,3 +10,15 @@ config IOMMUFD 
	  it relates to managing IO page tables that point at user space memory.



	  If you don't know what to do here, say N.



if IOMMUFD

config IOMMUFD_TEST

	bool "IOMMU Userspace API Test support"

	depends on DEBUG_KERNEL

	depends on FAULT_INJECTION

	depends on RUNTIME_TESTING_MENU

	default n

	help

	  This is dangerous, do not enable unless running

	  tools/testing/selftests/iommu

endif

drivers/iommu/iommufd/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -8,4 +8,6 @@ iommufd-y := \ 
	pages.o \

	vfio_compat.o



iommufd-$(CONFIG_IOMMUFD_TEST) += selftest.o



obj-$(CONFIG_IOMMUFD) += iommufd.o

drivers/iommu/iommufd/device.c

+38 −0
Original line number Diff line number Diff line
@@ -733,3 +733,41 @@ int iommufd_access_rw(struct iommufd_access *access, unsigned long iova, 
	return rc;

}

EXPORT_SYMBOL_NS_GPL(iommufd_access_rw, IOMMUFD);



#ifdef CONFIG_IOMMUFD_TEST

/*

 * Creating a real iommufd_device is too hard, bypass creating a iommufd_device

 * and go directly to attaching a domain.

 */

struct iommufd_hw_pagetable *

iommufd_device_selftest_attach(struct iommufd_ctx *ictx,

			       struct iommufd_ioas *ioas,

			       struct device *mock_dev)

{

	struct iommufd_hw_pagetable *hwpt;

	int rc;



	hwpt = iommufd_hw_pagetable_alloc(ictx, ioas, mock_dev);

	if (IS_ERR(hwpt))

		return hwpt;



	rc = iopt_table_add_domain(&hwpt->ioas->iopt, hwpt->domain);

	if (rc)

		goto out_hwpt;



	refcount_inc(&hwpt->obj.users);

	iommufd_object_finalize(ictx, &hwpt->obj);

	return hwpt;



out_hwpt:

	iommufd_object_abort_and_destroy(ictx, &hwpt->obj);

	return ERR_PTR(rc);

}



void iommufd_device_selftest_detach(struct iommufd_ctx *ictx,

				    struct iommufd_hw_pagetable *hwpt)

{

	iopt_table_remove_domain(&hwpt->ioas->iopt, hwpt->domain);

	refcount_dec(&hwpt->obj.users);

}

#endif

drivers/iommu/iommufd/ioas.c

+3 −0
Original line number Diff line number Diff line
@@ -242,6 +242,9 @@ int iommufd_ioas_copy(struct iommufd_ucmd *ucmd) 
	unsigned long iova;

	int rc;



	iommufd_test_syz_conv_iova_id(ucmd, cmd->src_ioas_id, &cmd->src_iova,

				      &cmd->flags);



	if ((cmd->flags &

	     ~(IOMMU_IOAS_MAP_FIXED_IOVA | IOMMU_IOAS_MAP_WRITEABLE |

	       IOMMU_IOAS_MAP_READABLE)))

drivers/iommu/iommufd/iommufd_private.h

+35 −0
Original line number Diff line number Diff line
@@ -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