[1/3] eal: fix pointer arithmetic with an expression argument

  RTE_PTR_SUB(ptr, x) and RTE_PTR_ALIGN_FLOOR() worked incorrectly
if "ptr" was an expression:

    uint32_t arr[3];

    RTE_PTR_SUB(arr + 1, sizeof(arr[0]));
    // expected: (uint32_t *)((uintptr_t)(arr + 1) - 4) == arr
    // actual:   (uint32_t *)((uintptr_t) arr + 1  - 4) != arr

    RTE_PTR_ALIGN_FLOOR(arr + 2, sizeof(arr[0]));
    // expected: RTE_ALIGN_FLOOR((uintptr_t)(arr + 2), 4) == &arr[2]
    // actual:   RTE_ALIGN_FLOOR((uintptr_t) arr + 2,  4) == &arr[0]

Fix the macros and extend the relevant unit test.

Fixes: af75078fece3 ("first public release")
Cc: stable@dpdk.org

Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
---
 app/test/test_common.c       | 11 +++++++++++
 lib/eal/include/rte_common.h |  4 ++--
 2 files changed, 13 insertions(+), 2 deletions(-)
  

> From: Dmitry Kozlyuk [mailto:dmitry.kozliuk@gmail.com]
> Sent: Sunday, 21 August 2022 22.50
> 
> RTE_PTR_SUB(ptr, x) and RTE_PTR_ALIGN_FLOOR() worked incorrectly
> if "ptr" was an expression:
> 
>     uint32_t arr[3];
> 
>     RTE_PTR_SUB(arr + 1, sizeof(arr[0]));
>     // expected: (uint32_t *)((uintptr_t)(arr + 1) - 4) == arr
>     // actual:   (uint32_t *)((uintptr_t) arr + 1  - 4) != arr
> 
>     RTE_PTR_ALIGN_FLOOR(arr + 2, sizeof(arr[0]));
>     // expected: RTE_ALIGN_FLOOR((uintptr_t)(arr + 2), 4) == &arr[2]
>     // actual:   RTE_ALIGN_FLOOR((uintptr_t) arr + 2,  4) == &arr[0]
> 
> Fix the macros and extend the relevant unit test.

Good catch. Serious bugs!

> 
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
> ---
>  app/test/test_common.c       | 11 +++++++++++
>  lib/eal/include/rte_common.h |  4 ++--
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/app/test/test_common.c b/app/test/test_common.c
> index ef177cecb1..4194c1208a 100644
> --- a/app/test/test_common.c
> +++ b/app/test/test_common.c
> @@ -31,6 +31,7 @@ test_macros(int __rte_unused unused_parm)
> 
>  	uintptr_t unused = 0;
>  	unsigned int smaller = SMALLER, bigger  = BIGGER;
> +	uint32_t arr[3];
> 
>  	RTE_SET_USED(unused);
> 
> @@ -41,6 +42,16 @@ test_macros(int __rte_unused unused_parm)
>  		FAIL_MACRO(RTE_PTR_ADD);
>  	if ((uintptr_t)RTE_PTR_SUB(BIGGER, PTR_DIFF) != SMALLER)
>  		FAIL_MACRO(RTE_PTR_SUB);
> +	if (RTE_PTR_ADD(arr + 1, sizeof(arr[0])) != &arr[2])
> +		FAIL_MACRO(RTE_PTR_ADD);
> +	if (RTE_PTR_SUB(arr + 1, sizeof(arr[0])) != &arr[0])
> +		FAIL_MACRO(RTE_PTR_SUB);

Very elegant test cases. :-)

> +	if (RTE_PTR_ALIGN_FLOOR(arr + 2, 4) != &arr[2])
> +		FAIL_MACRO(RTE_PTR_ALIGN_FLOOR);
> +	if (RTE_PTR_ALIGN_CEIL(arr + 2, 4) != &arr[2])
> +		FAIL_MACRO(RTE_PTR_ALIGN_CEIL);

While you are at it, consider adding a few more test cases, e.g.

RTE_PTR_ALIGN_FLOOR/CEIL(RTE_PTR_ADD(&arr[1], 1), 4), and
RTE_PTR_ALIGN_FLOOR/CEIL(RTE_PTR_ADD(&arr[1], sizeof(uint32_t) - 1), 4)

> +	if (RTE_PTR_ALIGN(arr + 2, 4) != &arr[2])
> +		FAIL_MACRO(RTE_PTR_ALIGN);
>  	if (RTE_PTR_DIFF(BIGGER, SMALLER) != PTR_DIFF)
>  		FAIL_MACRO(RTE_PTR_DIFF);
>  	if (RTE_MAX(SMALLER, BIGGER) != BIGGER)
> diff --git a/lib/eal/include/rte_common.h
> b/lib/eal/include/rte_common.h
> index a96cc2a138..d517e9f75f 100644
> --- a/lib/eal/include/rte_common.h
> +++ b/lib/eal/include/rte_common.h
> @@ -295,7 +295,7 @@ static void
> __attribute__((destructor(RTE_PRIO(prio)), used)) func(void)
>  /**
>   * subtract a byte-value offset from a pointer
>   */
> -#define RTE_PTR_SUB(ptr, x) ((void*)((uintptr_t)ptr - (x)))
> +#define RTE_PTR_SUB(ptr, x) ((void *)((uintptr_t)(ptr) - (x)))
> 
>  /**
>   * get the difference between two pointer values, i.e. how far apart
> @@ -320,7 +320,7 @@ static void
> __attribute__((destructor(RTE_PRIO(prio)), used)) func(void)
>   * must be a power-of-two value.
>   */
>  #define RTE_PTR_ALIGN_FLOOR(ptr, align) \
> -	((typeof(ptr))RTE_ALIGN_FLOOR((uintptr_t)ptr, align))
> +	((typeof(ptr))RTE_ALIGN_FLOOR((uintptr_t)(ptr), align))
> 
>  /**
>   * Macro to align a value to a given power-of-two. The resultant value
> --
> 2.33.1
> 

Reviewed-by: Morten Brørup <mb@smartsharesystems.com>