Re: [dpdk-dev] [PATCH v3 2/2] eal: fix side effects in ptr align macros

[Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>]

>> -----Original Message-----
>> From: pbhagavatula@marvell.com <pbhagavatula@marvell.com>
>> Sent: Tuesday, May 11, 2021 03:40
>> To: david.marchand@redhat.com; Wang, Haiyue
><haiyue.wang@intel.com>; Matan Azrad <matan@nvidia.com>;
>> Shahaf Shuler <shahafs@nvidia.com>; Viacheslav Ovsiienko
><viacheslavo@nvidia.com>; Jiawen Wu
>> <jiawenwu@trustnetic.com>; Jian Wang <jianwang@trustnetic.com>;
>Chautru, Nicolas
>> <nicolas.chautru@intel.com>; Thomas Monjalon
><thomas@monjalon.net>; Yigit, Ferruh
>> <ferruh.yigit@intel.com>; Andrew Rybchenko
><andrew.rybchenko@oktetlabs.ru>
>> Cc: dev@dpdk.org; Pavan Nikhilesh <pbhagavatula@marvell.com>;
>stable@dpdk.org
>> Subject: [dpdk-dev] [PATCH v3 2/2] eal: fix side effects in ptr align
>macros
>>
>> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
>>
>> Avoid expanding parameters inside RTE_*_ALIGN macros.
>> Update common_autotest to detect macro side effects.
>> Workaround static arrays relying on RTE_ALIGN macros.
>>
>> Fixes: af75078fece3 ("first public release")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
>> Signed-off-by: David Marchand <david.marchand@redhat.com>
>> ---
>>  app/test/test_common.c           |  6 ++++++
>>  drivers/net/e1000/e1000_ethdev.h |  7 ++++---
>>  drivers/net/ixgbe/ixgbe_ethdev.h |  6 ++++--
>>  drivers/net/mlx5/mlx5_rxtx_vec.h |  7 ++++---
>>  drivers/net/txgbe/txgbe_ethdev.h |  6 ++++--
>>  examples/bbdev_app/main.c        |  2 +-
>>  lib/eal/include/rte_common.h     | 17 +++++++++++++----
>>  lib/ethdev/rte_eth_ctrl.h        |  5 +++--
>>  8 files changed, 39 insertions(+), 17 deletions(-)
>>
>> diff --git a/app/test/test_common.c b/app/test/test_common.c
>> index 0dbb87e741..9efe3b10f9 100644
>> --- a/app/test/test_common.c
>> +++ b/app/test/test_common.c
>> @@ -69,6 +69,12 @@ test_macros(int __rte_unused unused_parm)
>>  	TEST_SIDE_EFFECT_2(RTE_PTR_ADD, void *, size_t);
>>  	TEST_SIDE_EFFECT_2(RTE_PTR_DIFF, void *, void *);
>>  	TEST_SIDE_EFFECT_2(RTE_PTR_SUB, void *, size_t);
>> +	TEST_SIDE_EFFECT_2(RTE_PTR_ALIGN, void *, size_t);
>> +	TEST_SIDE_EFFECT_2(RTE_PTR_ALIGN_CEIL, void *, size_t);
>> +	TEST_SIDE_EFFECT_2(RTE_PTR_ALIGN_FLOOR, void *, size_t);
>> +	TEST_SIDE_EFFECT_2(RTE_ALIGN, unsigned int, unsigned int);
>> +	TEST_SIDE_EFFECT_2(RTE_ALIGN_CEIL, unsigned int, unsigned
>int);
>> +	TEST_SIDE_EFFECT_2(RTE_ALIGN_FLOOR, unsigned int,
>unsigned int);
>>  	TEST_SIDE_EFFECT_2(RTE_ALIGN_MUL_CEIL, unsigned int,
>unsigned int);
>>  	TEST_SIDE_EFFECT_2(RTE_ALIGN_MUL_FLOOR, unsigned int,
>unsigned int);
>>  	TEST_SIDE_EFFECT_2(RTE_ALIGN_MUL_NEAR, unsigned int,
>unsigned int);
>> diff --git a/drivers/net/e1000/e1000_ethdev.h
>b/drivers/net/e1000/e1000_ethdev.h
>> index 3b4d9c3ee6..155d825d89 100644
>> --- a/drivers/net/e1000/e1000_ethdev.h
>> +++ b/drivers/net/e1000/e1000_ethdev.h
>> @@ -332,9 +332,10 @@ struct igb_eth_syn_filter_ele {
>>  };
>>
>>  #define IGB_FLEX_FILTER_MAXLEN	128	/**< bytes to use in flex
>filter. */
>> -#define IGB_FLEX_FILTER_MASK_SIZE	\
>> -	(RTE_ALIGN(IGB_FLEX_FILTER_MAXLEN, CHAR_BIT) /
>CHAR_BIT)
>> -					/**< mask bytes in flex filter. */
>> +#define IGB_FLEX_FILTER_MASK_SIZE                                              \
>> +	(RTE_ALIGN_FLOOR(IGB_FLEX_FILTER_MAXLEN + (CHAR_BIT -
>1), CHAR_BIT) /  \
>> +	 CHAR_BIT)
>> +/**< mask bytes in flex filter. */
>>
>
>Since:
>RTE_ALIGN --> RTE_ALIGN_CEIL(val, align) --> RTE_ALIGN_FLOOR(...)
>
>Why only change 'RTE_ALIGN_CEIL', but then call 'RTE_ALIGN_FLOOR'
>directly ?
>Sorry, can't get the point. : - (
>

RTE_ALIGN_CEIL is prone to macro side effects since it uses align twice in the macro.
To fix it RTE_ALIGN_CEIL first expands the val and align values to temporary values 
and then calls ALIGN_FLOOR.
Due to this we can no longer use ALIGN/ALIGN_CEIL in static array declarations

Example:
In file included from ../lib/eal/x86/include/rte_atomic.h:13,
                 from ../examples/bbdev_app/main.c:21:
../lib/eal/include/rte_common.h:312:15: error: braced-group within expression allowed only inside a function
  __extension__({                                                        \
               ^
../examples/bbdev_app/main.c:48:18: note: in expansion of macro 'RTE_ALIGN_CEIL'
 #define NCB (3 * RTE_ALIGN_CEIL(K + 4, 32))
                  ^~~~~~~~~~~~~~
../examples/bbdev_app/main.c:145:23: note: in expansion of macro 'NCB'
  uint8_t llr_temp_buf[NCB];

To workaround this I had to call RTE_ALIGN_FLOOR for known constants directly.

>Why not change 'RTE_ALIGN' if it has issue ?
>
>>
>> diff --git a/lib/eal/include/rte_common.h
>b/lib/eal/include/rte_common.h
>> index a142596587..6acd067b5c 100644
>> --- a/lib/eal/include/rte_common.h
>> +++ b/lib/eal/include/rte_common.h
>> @@ -294,8 +294,13 @@ static void
>__attribute__((destructor(RTE_PRIO(prio)), used)) func(void)
>>   * point to an address no lower than the first parameter. Second
>parameter
>>   * must be a power-of-two value.
>>   */
>> -#define RTE_PTR_ALIGN_CEIL(ptr, align) \
>> -	RTE_PTR_ALIGN_FLOOR((typeof(ptr))RTE_PTR_ADD(ptr, (align)
>- 1), align)
>> +#define RTE_PTR_ALIGN_CEIL(ptr, align)                                         \
>> +	__extension__({                                                        \
>> +		typeof(ptr) _pc = (ptr);                                       \
>> +		typeof(align) _ac = (align);                                   \
>> +
>	RTE_PTR_ALIGN_FLOOR((typeof(ptr))RTE_PTR_ADD(_pc, _ac -
>1),    \
>> +				    _ac);                                      \
>> +	})
>>
>>  /**
>>   * Macro to align a value to a given power-of-two. The resultant value
>> @@ -303,8 +308,12 @@ static void
>__attribute__((destructor(RTE_PRIO(prio)), used)) func(void)
>>   * than the first parameter. Second parameter must be a power-of-
>two
>>   * value.
>>   */
>> -#define RTE_ALIGN_CEIL(val, align) \
>> -	RTE_ALIGN_FLOOR(((val) + ((typeof(val)) (align) - 1)), align)
>> +#define RTE_ALIGN_CEIL(val, align)                                             \
>> +	__extension__({                                                        \
>> +		typeof(val) _vc = (val);                                       \
>> +		typeof(val) _ac = (typeof(val))(align);                        \
>> +		RTE_ALIGN_FLOOR((_vc + _ac - 1), _ac);                         \
>> +	})
>>
>>  /**
>>   * Macro to align a pointer to a given power-of-two. The resultant
>> diff --git a/lib/ethdev/rte_eth_ctrl.h b/lib/ethdev/rte_eth_ctrl.h
>> index 42652f9cce..863e56170b 100644
>> --- a/lib/ethdev/rte_eth_ctrl.h
>> +++ b/lib/ethdev/rte_eth_ctrl.h
>> @@ -431,8 +431,9 @@ enum rte_fdir_mode {
>>  };
>>
>>  #define UINT64_BIT (CHAR_BIT * sizeof(uint64_t))
>> -#define RTE_FLOW_MASK_ARRAY_SIZE \
>> -	(RTE_ALIGN(RTE_ETH_FLOW_MAX, UINT64_BIT)/UINT64_BIT)
>> +#define RTE_FLOW_MASK_ARRAY_SIZE                                               \
>> +	(RTE_ALIGN_FLOOR(RTE_ETH_FLOW_MAX + (UINT64_BIT - 1),
>UINT64_BIT) /    \
>> +	 UINT64_BIT)
>>
>>  /**
>>   * A structure used to get the information of flow director filter.
>> --
>> 2.17.1