Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755267AbbFLRUr (ORCPT ); Fri, 12 Jun 2015 13:20:47 -0400 Received: from mail-ie0-f172.google.com ([209.85.223.172]:34959 "EHLO mail-ie0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751199AbbFLRUp (ORCPT ); Fri, 12 Jun 2015 13:20:45 -0400 Message-ID: <557B14EA.80509@linaro.org> Date: Fri, 12 Jun 2015 11:20:42 -0600 From: Al Stone User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Lorenzo Pieralisi CC: "linux-acpi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linaro-acpi@lists.linaro.org" , "patches@linaro.org" , "linaro-kernel@lists.linaro.org" Subject: Re: [PATCH 2/3] ACPI: add BAD_MADT_GICC_ENTRY() macro References: <1434051911-14665-1-git-send-email-al.stone@linaro.org> <1434051911-14665-3-git-send-email-al.stone@linaro.org> <20150612145244.GB27385@red-moon> In-Reply-To: <20150612145244.GB27385@red-moon> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3852 Lines: 101 On 06/12/2015 08:52 AM, Lorenzo Pieralisi wrote: > On Thu, Jun 11, 2015 at 08:45:10PM +0100, al.stone@linaro.org wrote: >> From: Al Stone >> >> The BAD_MADT_ENTRY() macro is designed to work for all of the subtables >> of the MADT. In the ACPI 5.1 version of the spec, the struct for the >> GICC subtable (struct acpi_madt_generic_interrupt) is 76 bytes long; in >> ACPI 6.0, the struct is 80 bytes long. But, there is only one definition >> in ACPICA for this struct -- and that is the 6.0 version. Hence, when >> BAD_MADT_ENTRY() compares the struct size to the length in the GICC >> subtable, it fails if 5.1 structs are in use, and there are systems in >> the wild that have them. >> >> This patch adds the BAD_MADT_GICC_ENTRY() that checks the GICC subtable >> only, accounting for the difference in specification versions that are >> possible. The BAD_MADT_ENTRY() will continue to work as is for all other >> MADT subtables. > > Unfortunately that's nothing new, it seems. ia64 put in place a quite > nifty solution to that (I *guess* owing to ACPI 3.0 updates to Local > sapic specs), have a look at: > > arch/ia64/kernel/acpi.c acpi_parse_lsacpi() > > /*Skip BAD_MADT_ENTRY check, as lsapic size could vary */ > > We remove the check, job done ;-) Heh. Yes, that's one way to do it :). >> Signed-off-by: Al Stone >> Reviewed-by: Hanjun Guo >> Reviewed-by: Graeme Gregory >> >> CC: Rafael J. Wysocki >> CC: Len Brown >> >> --- >> include/linux/acpi.h | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/include/linux/acpi.h b/include/linux/acpi.h >> index 33ed313..8a83f91 100644 >> --- a/include/linux/acpi.h >> +++ b/include/linux/acpi.h >> @@ -127,6 +127,13 @@ static inline void acpi_initrd_override(void *data, size_t size) >> (!entry) || (unsigned long)entry + sizeof(*entry) > end || \ >> ((struct acpi_subtable_header *)entry)->length < sizeof(*entry)) >> >> +#define BAD_MADT_GICC_ENTRY(entry, end) ( \ >> + (!entry) || (unsigned long)entry + sizeof(*entry) > end || \ >> + ((ACPI_FADT_SPEC_VERSION == ACPI_SPEC_VERSION(5,1)) && \ >> + (entry->header.length != 76)) || \ >> + ((ACPI_FADT_SPEC_VERSION == ACPI_SPEC_VERSION(6,0)) && \ >> + (entry->header.length != 80))) > > I would make those length magic numbers ACPICA defines at least. Yup, you're right. I'll fix that. > It is not a GICC only issue, that's true for all MADT subtables that change > size with versions so, maybe we can replace the sizeof(*entry) in > BAD_MADT_ENTRY with a macro compound statement returning the subtable > length (where you can add a switch case on entry->type and return > sizeof(*entry) in the default case) ? > > Overkill ? Certainly ugly, but at least you do not need to patch anything > else. There is precedent for this; there's a function to print MADT subtable entries with exactly this structure. And yeah, it's a bit ugly, but it does the job. > I am inclined to relegate these checks to ACPICA tools (statically) > altogether. Interestingly enough, the acpi_table_print_madt_entry() function I was referring to is in the drivers/acpi code, not ACPICA. I wonder what the history is on that and why it ended up there... > It is better to check Len and Rafael opinion on this first before coding it. > > Lorenzo > Yup. Agreed. -- ciao, al ----------------------------------- Al Stone Software Engineer Linaro Enterprise Group al.stone@linaro.org ----------------------------------- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/