On Wed, 2010-05-26 at 10:39 +0800, Lin Ming wrote:
> On Tue, 2010-05-25 at 18:59 +0800, Alexey Starikovskiy wrote:
> > Allow field reads of more than 64 bits if the field is properly aligned.
> > EC driver will be able to read in bursts of up to 32 bytes with this patch.
>
> Hi, Alexey,
>
> Got a divide-by-zero fault when running aslts test.
>
> $cd aslts/src/runtime/collections/functional/region
> $iasl MAIN.asl
> $acpiexec -bex,mn00 region.aml
> ......
> Floating point exception
>
> It's because in the region test case, ObjDesc->CommonField.BitLength is
> 2048 and ObjDesc->CommonField.AccessByteWidth is UINT8,
>
> ObjDesc->CommonField.AccessByteWidth =
> ACPI_ROUND_BITS_UP_TO_BYTES(ObjDesc->CommonField.BitLength);
>
> so this assignment causes ObjDesc->CommonField.AccessByteWidth to zero.
>
> Although this test case nearly can not exist in real BIOS aml code, but
> how about add below code to do more check?
>
> diff --git a/source/components/executer/exprep.c b/source/components/executer/exprep.c
> index 95fa502..65cbe39 100644
> --- a/source/components/executer/exprep.c
> +++ b/source/components/executer/exprep.c
> @@ -511,6 +511,7 @@ AcpiExPrepFieldValue (
> ACPI_OPERAND_OBJECT *ObjDesc;
> ACPI_OPERAND_OBJECT *SecondDesc = NULL;
> UINT32 Type;
> + UINT32 AccessByteWidth;
> ACPI_STATUS Status;
>
>
> @@ -568,8 +569,12 @@ AcpiExPrepFieldValue (
> /* allow full data read from EC address space */
> if (ObjDesc->Field.RegionObj->Region.SpaceId == ACPI_ADR_SPACE_EC) {
> if (ObjDesc->CommonField.BitLength > 8) {
> - ObjDesc->CommonField.AccessByteWidth =
> - ACPI_ROUND_BITS_UP_TO_BYTES(ObjDesc->CommonField.BitLength);
> + AccessByteWidth = ACPI_ROUND_BITS_UP_TO_BYTES(ObjDesc->CommonField.BitLength);
> +
> + /* The max of ObjDesc->CommonField.AccessByteWidth is 0xFF */
> + if (!(AccessByteWidth >> 8)) {
Better to test AccessByteWidth as below,
+ if (!(AccessByteWidth & ~0xFF)) {
> + ObjDesc->CommonField.AccessByteWidth = AccessByteWidth;
> + }
> }
> }
>
> ---
> Lin Ming
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