On 4 June 2015 at 17:55, Heyi Guo <heyi....@linaro.org> wrote:
> DescEnd will be clipped for alignment in CoreFindFreePagesI, and it
> may fall below DescStart, when alignment is more than 16KB (included)
> and both DescStart and original DescEnd fall into a single range of
> such alignment. This results in a huge size (Negative number in
> unsigned type) for this descriptor, fulfilling the allocation
> requirement but failing to run ConvertPages; at last it causes
at least
> occasional failure of AllocatePages.
>
> A simple comparison is added to ensure we would never get a negative
> number.
>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Heyi Guo <heyi....@linaro.org>
Acked-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
So is this only happening because we use different granularities for
boottime and runtime allocations on AArch64?
> ---
> MdeModulePkg/Core/Dxe/Mem/Page.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/MdeModulePkg/Core/Dxe/Mem/Page.c
> b/MdeModulePkg/Core/Dxe/Mem/Page.c
> index a92c865..f2efaf1 100644
> --- a/MdeModulePkg/Core/Dxe/Mem/Page.c
> +++ b/MdeModulePkg/Core/Dxe/Mem/Page.c
> @@ -1051,6 +1051,11 @@ CoreFindFreePagesI (
>
> DescEnd = ((DescEnd + 1) & (~(Alignment - 1))) - 1;
>
> + // Skip if DescEnd is less than DescStart after alignment clipping
> + if (DescEnd < DescStart) {
> + continue;
> + }
> +
> //
> // Compute the number of bytes we can used from this
> // descriptor, and see it's enough to satisfy the request
> --
> 2.1.4
>
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