mirror_ubuntu-kernels/drivers/gpu/drm/imagination/pvr_device.h

/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
/* Copyright (c) 2023 Imagination Technologies Ltd. */

#ifndef PVR_DEVICE_H
#define PVR_DEVICE_H

#include <drm/drm_device.h>
#include <drm/drm_file.h>
#include <drm/drm_mm.h>

#include <linux/bits.h>
#include <linux/compiler_attributes.h>
#include <linux/compiler_types.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/wait.h>

/**
 * struct pvr_device - powervr-specific wrapper for &struct drm_device
 */
struct pvr_device {
	/**
	 * @base: The underlying &struct drm_device.
	 *
	 * Do not access this member directly, instead call
	 * from_pvr_device().
	 */
	struct drm_device base;
};

/**
 * struct pvr_file - powervr-specific data to be assigned to &struct
 * drm_file.driver_priv
 */
struct pvr_file {
	/**
	 * @file: A reference to the parent &struct drm_file.
	 *
	 * Do not access this member directly, instead call from_pvr_file().
	 */
	struct drm_file *file;

	/**
	 * @pvr_dev: A reference to the powervr-specific wrapper for the
	 *           associated device. Saves on repeated calls to
	 *           to_pvr_device().
	 */
	struct pvr_device *pvr_dev;
};

#define from_pvr_device(pvr_dev) (&(pvr_dev)->base)

#define to_pvr_device(drm_dev) container_of_const(drm_dev, struct pvr_device, base)

#define from_pvr_file(pvr_file) ((pvr_file)->file)

#define to_pvr_file(file) ((file)->driver_priv)

/**
 * DOC: IOCTL validation helpers
 *
 * To validate the constraints imposed on IOCTL argument structs, a collection
 * of macros and helper functions exist in ``pvr_device.h``.
 *
 * Of the current helpers, it should only be necessary to call
 * PVR_IOCTL_UNION_PADDING_CHECK() directly. This macro should be used once in
 * every code path which extracts a union member from a struct passed from
 * userspace.
 */

/**
 * pvr_ioctl_union_padding_check() - Validate that the implicit padding between
 * the end of a union member and the end of the union itself is zeroed.
 * @instance: Pointer to the instance of the struct to validate.
 * @union_offset: Offset into the type of @instance of the target union. Must
 * be 64-bit aligned.
 * @union_size: Size of the target union in the type of @instance. Must be
 * 64-bit aligned.
 * @member_size: Size of the target member in the target union specified by
 * @union_offset and @union_size. It is assumed that the offset of the target
 * member is zero relative to @union_offset. Must be 64-bit aligned.
 *
 * You probably want to use PVR_IOCTL_UNION_PADDING_CHECK() instead of calling
 * this function directly, since that macro abstracts away much of the setup,
 * and also provides some static validation. See its docs for details.
 *
 * Return:
 *  * %true if every byte between the end of the used member of the union and
 *    the end of that union is zeroed, or
 *  * %false otherwise.
 */
static __always_inline bool
pvr_ioctl_union_padding_check(void *instance, size_t union_offset,
			      size_t union_size, size_t member_size)
{
	/*
	 * void pointer arithmetic is technically illegal - cast to a byte
	 * pointer so this addition works safely.
	 */
	void *padding_start = ((u8 *)instance) + union_offset + member_size;
	size_t padding_size = union_size - member_size;

	return !memchr_inv(padding_start, 0, padding_size);
}

/**
 * PVR_STATIC_ASSERT_64BIT_ALIGNED() - Inline assertion for 64-bit alignment.
 * @static_expr_: Target expression to evaluate.
 *
 * If @static_expr_ does not evaluate to a constant integer which would be a
 * 64-bit aligned address (i.e. a multiple of 8), compilation will fail.
 *
 * Return:
 * The value of @static_expr_.
 */
#define PVR_STATIC_ASSERT_64BIT_ALIGNED(static_expr_)                     \
	({                                                                \
		static_assert(((static_expr_) & (sizeof(u64) - 1)) == 0); \
		(static_expr_);                                           \
	})

/**
 * PVR_IOCTL_UNION_PADDING_CHECK() - Validate that the implicit padding between
 * the end of a union member and the end of the union itself is zeroed.
 * @struct_instance_: An expression which evaluates to a pointer to a UAPI data
 * struct.
 * @union_: The name of the union member of @struct_instance_ to check. If the
 * union member is nested within the type of @struct_instance_, this may
 * contain the member access operator (".").
 * @member_: The name of the member of @union_ to assess.
 *
 * This is a wrapper around pvr_ioctl_union_padding_check() which performs
 * alignment checks and simplifies things for the caller.
 *
 * Return:
 *  * %true if every byte in @struct_instance_ between the end of @member_ and
 *    the end of @union_ is zeroed, or
 *  * %false otherwise.
 */
#define PVR_IOCTL_UNION_PADDING_CHECK(struct_instance_, union_, member_)     \
	({                                                                   \
		typeof(struct_instance_) __instance = (struct_instance_);    \
		size_t __union_offset = PVR_STATIC_ASSERT_64BIT_ALIGNED(     \
			offsetof(typeof(*__instance), union_));              \
		size_t __union_size = PVR_STATIC_ASSERT_64BIT_ALIGNED(       \
			sizeof(__instance->union_));                         \
		size_t __member_size = PVR_STATIC_ASSERT_64BIT_ALIGNED(      \
			sizeof(__instance->union_.member_));                 \
		pvr_ioctl_union_padding_check(__instance, __union_offset,    \
					      __union_size, __member_size);  \
	})

#endif /* PVR_DEVICE_H */