linux-kernel - [PATCH 2/2] arm64: acpi: Prepare for longer MADTs

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Message-Id: <20181012192937.3819951-1-jeremy.linton@arm.com>
Date:   Fri, 12 Oct 2018 14:29:37 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will.deacon@....com,
        ard.biesheuvel@...aro.org, james.morse@....com,
        rafael.j.wysocki@...el.com, takahiro.akashi@...aro.org,
        lorenzo.pieralisi@....com, sudeep.holla@....com, ahs3@...hat.com,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jeremy Linton <jeremy.linton@....com>
Subject: [PATCH 2/2] arm64: acpi: Prepare for longer MADTs

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@....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)
 
 #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))
 
 /* Basic configuration for ACPI */
 #ifdef	CONFIG_ACPI
-- 
2.14.3