[2/2] arm64: acpi: Prepare for longer MADTs

Message ID 20181012192937.3819951-1-jeremy.linton@arm.com
State New
Headers show
Series
  • Untitled series #15549
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Commit Message

Jeremy Linton Oct. 12, 2018, 7:29 p.m.
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(-)

-- 
2.14.3

Comments

Sudeep Holla Oct. 15, 2018, 9:29 a.m. | #1
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
Lorenzo Pieralisi Nov. 1, 2018, 11:31 a.m. | #2
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(-)


Hi Jeremy,

I assume there is no [PATCH 1/2] (to make sure I have not missed
anything).

> 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)


I would add a comment explaining why the efficiency_class offset
corresponds to the min length, I will do it myself before sending it
upstream.

I will take this patch and send it to Will/Catalin with ARM64 ACPI
material for v4.21.

Thanks,
Lorenzo

>  

>  #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

>
Sudeep Holla Nov. 1, 2018, 2:22 p.m. | #3
On Thu, Nov 01, 2018 at 11:31:36AM +0000, Lorenzo Pieralisi wrote:
> 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(-)

>

> Hi Jeremy,

>

> I assume there is no [PATCH 1/2] (to make sure I have not missed

> anything).

>


IIRC, it's a patch fixing module device table entry for SPE. They are
independent, just happened to be put out together.

--
Regards,
Sudeep

Patch

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