Re: [PATCH 1/6] arm/mpu: Find MPU region by range

[Ayan Kumar Halder <ayankuma@xxxxxxx>]

Hi,

On 20/06/2025 10:49, Hari Limaye wrote:
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>
> From: Luca Fancellu <luca.fancellu@xxxxxxx>
>
> Implement a function to find the index of a MPU region
> in the xen_mpumap MPU region array.
>
> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
> Signed-off-by: Hari Limaye <hari.limaye@xxxxxxx>
Reviewed-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> ---
>   xen/arch/arm/include/asm/mpu/mm.h | 29 ++++++++++++++
>   xen/arch/arm/mpu/mm.c             | 66 +++++++++++++++++++++++++++++++
>   2 files changed, 95 insertions(+)
>
> diff --git a/xen/arch/arm/include/asm/mpu/mm.h 
> b/xen/arch/arm/include/asm/mpu/mm.h
> index a7f970b465..a0f0d86d4a 100644
> --- a/xen/arch/arm/include/asm/mpu/mm.h
> +++ b/xen/arch/arm/include/asm/mpu/mm.h
> @@ -10,6 +10,13 @@
>   #include <asm/mm.h>
>   #include <asm/mpu.h>
>
> +#define MPUMAP_REGION_OVERLAP      -1
> +#define MPUMAP_REGION_NOTFOUND      0
> +#define MPUMAP_REGION_FOUND         1
> +#define MPUMAP_REGION_INCLUSIVE     2
> +
> +#define INVALID_REGION_IDX     0xFFU
> +
>   extern struct page_info *frame_table;
>
>   extern uint8_t max_mpu_regions;
> @@ -75,6 +82,28 @@ void write_protection_region(const pr_t *pr_write, uint8_t 
> sel);
>    */
>   pr_t pr_of_addr(paddr_t base, paddr_t limit, unsigned int flags);
>
> +/*
> + * Checks whether a given memory range is present in the provided table of
> + * MPU protection regions.
> + *
> + * @param table         Array of pr_t protection regions.
> + * @param r_regions     Number of elements in `table`.
> + * @param base          Start of the memory region to be checked (inclusive).
> + * @param limit         End of the memory region to be checked (exclusive).
> + * @param index         Set to the index of the region if an exact or inclusive
> + *                      match is found, and INVALID_REGION otherwise.
> + * @return: Return code indicating the result of the search:
> + *          MPUMAP_REGION_NOTFOUND: no part of the range is present in #table
> + *          MPUMAP_REGION_FOUND: found an exact match in #table
> + *          MPUMAP_REGION_INCLUSIVE: found an inclusive match in #table
> + *          MPUMAP_REGION_OVERLAP: found an overlap with a mapping in #table
> + *
> + * Note: make sure that the range [#base, #limit) refers to the half-open
> + * interval inclusive of #base and exclusive of #limit.
> + */
> +int mpumap_contain_region(pr_t *table, uint8_t nr_regions, paddr_t base,
> +                          paddr_t limit, uint8_t *index);
> +
>   #endif /* __ARM_MPU_MM_H__ */
>
>   /*
> diff --git a/xen/arch/arm/mpu/mm.c b/xen/arch/arm/mpu/mm.c
> index ccfb37a67b..15197339b1 100644
> --- a/xen/arch/arm/mpu/mm.c
> +++ b/xen/arch/arm/mpu/mm.c
> @@ -12,6 +12,18 @@
>   #include <asm/page.h>
>   #include <asm/sysregs.h>
>
> +#ifdef NDEBUG
> +static inline void __attribute__ ((__format__ (__printf__, 1, 2)))
> +region_printk(const char *fmt, ...) {}
> +#else /* !NDEBUG */
> +#define region_printk(fmt, args...)         \
> +    do                                      \
> +    {                                       \
> +        dprintk(XENLOG_ERR, fmt, ## args);  \
> +        WARN();                             \
> +    } while (0)
> +#endif /* NDEBUG */
> +
>   struct page_info *frame_table;
>
>   /* Maximum number of supported MPU memory regions by the EL2 MPU. */
> @@ -110,6 +122,60 @@ pr_t pr_of_addr(paddr_t base, paddr_t limit, unsigned int 
> flags)
>       return region;
>   }
>
> +int mpumap_contain_region(pr_t *table, uint8_t nr_regions, paddr_t base,
> +                          paddr_t limit, uint8_t *index)
> +{
> +    uint8_t i = 0, _index;
> +
> +    /* Allow index to be NULL */
> +    index = index ? index : &_index;
> +
> +    /* Inside mpumap_contain_region check for inclusive range */
> +    limit = limit - 1;
> +
> +    *index = INVALID_REGION_IDX;
> +
> +    if ( limit < base )
> +    {
> +        region_printk("Base address 0x%"PRIpaddr" must be smaller than limit address 
> 0x%"PRIpaddr"\n",
> +                      base, limit);
> +        return -EINVAL;
> +    }
> +
> +    for ( ; i < nr_regions; i++ )
> +    {
> +        paddr_t iter_base = pr_get_base(&table[i]);
> +        paddr_t iter_limit = pr_get_limit(&table[i]);
> +
> +        /* Found an exact valid match */
> +        if ( (iter_base == base) && (iter_limit == limit) &&
> +             region_is_valid(&table[i]) )
> +        {
> +            *index = i;
> +            return MPUMAP_REGION_FOUND;
> +        }
> +
> +        /* No overlapping */
> +        if ( (iter_limit < base) || (iter_base > limit) )
> +            continue;
> +
> +        /* Inclusive and valid */
> +        if ( (base >= iter_base) && (limit <= iter_limit) &&
> +             region_is_valid(&table[i]) )
> +        {
> +            *index = i;
> +            return MPUMAP_REGION_INCLUSIVE;
> +        }
> +
> +        /* Overlap */
> +        region_printk("Range 0x%"PRIpaddr" - 0x%"PRIpaddr" overlaps with the existing region 
> 0x%"PRIpaddr" - 0x%"PRIpaddr"\n",
> +                      base, limit + 1, iter_base, iter_limit + 1);
> +        return MPUMAP_REGION_OVERLAP;
> +    }
> +
> +    return MPUMAP_REGION_NOTFOUND;
> +}
> +
>   void __init setup_mm(void)
>   {
>       BUG_ON("unimplemented");
LGTM.

- Ayan

> --
> 2.34.1