[PATCH v2 3/3] arm: caches: manage phys_addr_t overflow in mmu_set_region_dcache_behaviour

[Tom Rini]

On Fri, Apr 24, 2020 at 08:20:17PM +0200, Patrick Delaunay wrote:

> Solved the overflow on phys_addr_t type for start + size in
> mmu_set_region_dcache_behaviour() function.
> 
> This overflow is avoided by dividing start and end by 2 before addition,
> and we only expecting that start and size are even.
> 
> This patch doesn't change the current function behavior if the
> parameters (start or size) are not aligned on MMU_SECTION_SIZE.
> 
> For example, this overflow occurs on ARM32 with:
> start = 0xC0000000 and size = 0x40000000
> then start + size = 0x100000000 and end = 0x0.
> 
> For information the function behavior change with risk of regression,
> if we just shift start and size before the addition.
> Example with 2MB section size:
>   MMU_SECTION_SIZE 0x200000 and MMU_SECTION_SHIFT = 21
>   with start = 0x1000000, size = 0x1000000,
>   - with the proposed patch, start = 0 and end = 0x1 as previously
>   - with the more simple patch:
>     end = (start >> MMU_SECTION_SHIFT) + (size >> MMU_SECTION_SHIFT)
>     the value of end change:
>     start >> 21 = 0, size >> 21 = 0 and end = 0x0 !!!
> 
> Signed-off-by: Patrick Delaunay <patrick.delaunay at st.com>

Applied to u-boot/master, thanks!

-- 
Tom
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