On Fri, Jul 10, 2015 at 04:47:34PM +0100, Moore, Robert wrote: > > > > -----Original Message----- > > From: Lorenzo Pieralisi [mailto:lorenzo.pieral...@arm.com] > > Sent: Friday, July 10, 2015 8:18 AM > > To: Moore, Robert > > Cc: Ming Lei; Zheng, Lv; Wysocki, Rafael J; Linux Kernel Mailing List; > > linux-arm-kernel; Thomas Gleixner; Jason Cooper; hanjun....@linaro.org > > Subject: Re: ACPI: regression: Failed to initialize GIC IRQ controller > > > > On Fri, Jul 10, 2015 at 03:45:32PM +0100, Moore, Robert wrote: > > > It's nice that someone took a sizeof() on the struct -- so, one would > > hope that no code actually depended on a particular value, no? > > > > Unfortunately that sizeof has been there forever (x86/ia64), > > ia64 code ran into a similar issue, so the check was removed to cope with > > lsapic MADT updates, see: > > > > arch/ia64/kernel/acpi.c line 204 > > > > /*Skip BAD_MADT_ENTRY check, as lsapic size could vary */ > > > > Is checking the subtable length field against a static value really > > worthwhile/suitable ? > > > > I would at least traverse the subtables via the subtable length given in the > table, and not use a sizeof() for each subtable. Then, multiple > table/subtable versions are handled automatically; you don't have to use any > new fields until necessary.
I lost you here, sorry. You are describing how the subtable entries are parsed in acpi_parse_entries, but that's not what we are debating here. BAD_MADT_ENTRY checks the subtable length against the ACPICA MADT structs sized through sizeof to determine if the length field is "correct", I do not see how you can do it by traversing the tables (how can you determine where a subtable _really_ ends or to put it differently how to check that a subtable length is _really_ right ?). Thanks, Lorenzo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
