Re: [Intel-gfx] [PATCH v4 1/7] drm: Move and add a few utility macros into drm util header
On Thu, 11 Aug 2022, Daniel Vetter wrote:
> 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
>> Cc: Thomas Hellström
>> Cc: Matthew Auld
>> Cc: Nirmoy Das
>> Cc: Jani Nikula
>> Reviewed-by: Mauro Carvalho Chehab
>> ---
>> 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.
Agreed [1].
BR,
Jani.
[1] https://lore.kernel.org/r/875yj9qv62@intel.com
> -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
>> #include
>> #include
>> +#include
>>
>> #ifdef CONFIG_X86
>> #include
>> @@ -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
>> + */
>>
Re: [Intel-gfx] [PATCH v4 1/7] drm: Move and add a few utility macros into drm util header
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
> Cc: Thomas Hellström
> Cc: Matthew Auld
> Cc: Nirmoy Das
> Cc: Jani Nikula
> Reviewed-by: Mauro Carvalho Chehab
> ---
> 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
> #include
> #include
> +#include
>
> #ifdef CONFIG_X86
> #include
> @@ -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
> +
