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SubjectRe: [PATCH 2/2] arm64: acpi: Prepare for longer MADTs
On Fri, Oct 12, 2018 at 02:29:37PM -0500, Jeremy Linton wrote:
> The BAD_MADT_GICC_ENTRY check is a little too strict because
> it rejects MADT entries that don't match the currently known
> lengths. We should remove this restriction to avoid problems
> if the table length changes. Future code which might depend on
> additional fields should be written to validate those fields
> before using them, rather than trying to globally check
> known MADT version lengths.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
> arch/arm64/include/asm/acpi.h | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> index 709208dfdc8b..4d0946bd485a 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -22,12 +22,12 @@
> #include <asm/tlbflush.h>
>
> /* Macros for consistency checks of the GICC subtable of MADT */
> -#define ACPI_MADT_GICC_LENGTH \
> - (acpi_gbl_FADT.header.revision < 6 ? 76 : 80)
> +#define ACPI_MADT_GICC_MIN_LENGTH ACPI_OFFSET( \
> + struct acpi_madt_generic_interrupt, efficiency_class)
>

This makes it 76 always which is fine, just that the first user of
efficiency_class should check for the length before accessing it.
No user of efficiency_class yet, so I am fine with this change.

> #define BAD_MADT_GICC_ENTRY(entry, end) \
> - (!(entry) || (entry)->header.length != ACPI_MADT_GICC_LENGTH || \
> - (unsigned long)(entry) + ACPI_MADT_GICC_LENGTH > (end))
> + (!(entry) || (entry)->header.length < ACPI_MADT_GICC_MIN_LENGTH || \
> + (unsigned long)(entry) + (entry)->header.length > (end))
>

Acked-by: Sudeep Holla <sudeep.holla@arm.com>

--
Regards,
Sudeep

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