On Tue, Jul 19, 2022 at 05:04:18PM +0300, Gwan-gyeong Mun wrote:
> It moves overflows_type utility macro into drm util header from i915_utils
> header. The overflows_type can be used to catch the truncation between data
> types. And it adds safe_conversion() macro which performs a type conversion
> (cast) of an source value into a new variable, checking that the
> destination is large enough to hold the source value.
> And it adds exact_type and exactly_pgoff_t macro to catch type mis-match
> while compiling.
>
> v3: Add is_type_unsigned() macro (Mauro)
> Modify overflows_type() macro to consider signed data types (Mauro)
> Fix the problem that safe_conversion() macro always returns true
> v4: Fix kernel-doc markups
>
> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx>
> Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
> Cc: Nirmoy Das <nirmoy.das@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
> Reviewed-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_utils.h | 5 +-
> include/drm/drm_util.h | 77 +++++++++++++++++++++++++++++++
It's nice that there's less random piling into i915_utils.h, but pushing
them into drm_util.h isn't really better. These should all be in
include/linux/ somewhere, so that we have as consistent code as possible.
drm_util.h should only be a fallback if we get nacks for a more general
place and still think it's the right thing to do.
i915_util.h has frankyl gone completely bonkers and should die.
-Daniel
> 2 files changed, 78 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
> index c10d68cdc3ca..345e5b2dc1cd 100644
> --- a/drivers/gpu/drm/i915/i915_utils.h
> +++ b/drivers/gpu/drm/i915/i915_utils.h
> @@ -32,6 +32,7 @@
> #include <linux/types.h>
> #include <linux/workqueue.h>
> #include <linux/sched/clock.h>
> +#include <drm/drm_util.h>
>
> #ifdef CONFIG_X86
> #include <asm/hypervisor.h>
> @@ -111,10 +112,6 @@ bool i915_error_injected(void);
> #define range_overflows_end_t(type, start, size, max) \
> range_overflows_end((type)(start), (type)(size), (type)(max))
>
> -/* Note we don't consider signbits :| */
> -#define overflows_type(x, T) \
> - (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T))
> -
> #define ptr_mask_bits(ptr, n) ({ \
> unsigned long __v = (unsigned long)(ptr); \
> (typeof(ptr))(__v & -BIT(n)); \
> diff --git a/include/drm/drm_util.h b/include/drm/drm_util.h
> index 79952d8c4bba..1de9ee5704fa 100644
> --- a/include/drm/drm_util.h
> +++ b/include/drm/drm_util.h
> @@ -62,6 +62,83 @@
> */
> #define for_each_if(condition) if (!(condition)) {} else
>
> +/**
> + * is_type_unsigned - helper for checking data type which is an unsigned data
> + * type or not
> + * @x: The data type to check
> + *
> + * Returns:
> + * True if the data type is an unsigned data type, false otherwise.
> + */
> +#define is_type_unsigned(x) ((typeof(x))-1 >= (typeof(x))0)
> +
> +/**
> + * overflows_type - helper for checking the truncation between data types
> + * @x: Source for overflow type comparison
> + * @T: Destination for overflow type comparison
> + *
> + * It compares the values and size of each data type between the first and
> + * second argument to check whether truncation can occur when assigning the
> + * first argument to the variable of the second argument.
> + * Source and Destination can be used with or without sign bit.
> + * Composite data structures such as union and structure are not considered.
> + * Enum data types are not considered.
> + * Floating point data types are not considered.
> + *
> + * Returns:
> + * True if truncation can occur, false otherwise.
> + */
> +
> +#define overflows_type(x, T) \
> + (is_type_unsigned(x) ? \
> + is_type_unsigned(T) ? \
> + (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T)) ? 1 : 0 \
> + : (sizeof(x) >= sizeof(T) && (x) >> (BITS_PER_TYPE(T) - 1)) ? 1 : 0 \
> + : is_type_unsigned(T) ? \
> + ((x) < 0) ? 1 : (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T)) ? 1 : 0 \
> + : (sizeof(x) > sizeof(T)) ? \
> + ((x) < 0) ? (((x) * -1) >> BITS_PER_TYPE(T)) ? 1 : 0 \
> + : ((x) >> BITS_PER_TYPE(T)) ? 1 : 0 \
> + : 0)
> +
> +/**
> + * exact_type - break compile if source type and destination value's type are
> + * not the same
> + * @T: Source type
> + * @n: Destination value
> + *
> + * It is a helper macro for a poor man's -Wconversion: only allow variables of
> + * an exact type. It determines whether the source type and destination value's
> + * type are the same while compiling, and it breaks compile if two types are
> + * not the same
> + */
> +#define exact_type(T, n) \
> + BUILD_BUG_ON(!__builtin_constant_p(n) && !__builtin_types_compatible_p(T, typeof(n)))
> +
> +/**
> + * exactly_pgoff_t - helper to check if the type of a value is pgoff_t
> + * @n: value to compare pgoff_t type
> + *
> + * It breaks compile if the argument value's type is not pgoff_t type.
> + */
> +#define exactly_pgoff_t(n) exact_type(pgoff_t, n)
> +
> +/**
> + * safe_conversion - perform a type conversion (cast) of an source value into
> + * a new variable, checking that the destination is large enough to hold the
> + * source value.
> + * @ptr: Destination pointer address
> + * @value: Source value
> + *
> + * Returns:
> + * If the value would overflow the destination, it returns false.
> + */
> +#define safe_conversion(ptr, value) ({ \
> + typeof(value) __v = (value); \
> + typeof(ptr) __ptr = (ptr); \
> + overflows_type(__v, *__ptr) ? 0 : ((*__ptr = (typeof(*__ptr))__v), 1); \
> +})
> +
> /**
> * drm_can_sleep - returns true if currently okay to sleep
> *
> --
> 2.34.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
