On Wednesday, September 16, 2015 05:26:40 PM Al Stone wrote:
Currently, the BAD_MADT_ENTRY macro is used to do a very simple sanity check on the various subtables that are defined for the MADT. The check compares the size of the subtable data structure as defined by ACPICA to the length entry in the subtable. If they are not the same, the assumption is that the subtable is incorrect.
Over time, the ACPI spec has allowed for MADT subtables where this can never be true (the local SAPIC subtable, for example). Or, more recently, the spec has accumulated some minor flaws where there are three possible sizes for a subtable, all of which are valid, but only for specific versions of the spec (the GICC subtable). In both cases, BAD_MADT_ENTRY reports these subtables as bad when they are not. In order to retain some sanity check on the MADT subtables, we now have to special case these subtables. Of necessity, these special cases have ended up in arch-dependent code (arm64) or an arch has simply decided to forgo the check (ia64).
This patch set replaces the BAD_MADT_ENTRY macro with a function called bad_madt_entry(). This function uses a data set of details about the subtables to provide more sanity checking than before:
-- is the subtable legal for the version given in the FADT?
-- is the subtable legal for the revision of the MADT in use?
-- is the subtable of the proper length (including checking on the one variable length subtable that is currently ignored), given the FADT version and the MADT revision?
Further, this patch set adds in the call to bad_madt_entry() from the acpi_table_parse_madt() function, allowing it to be used consistently by all architectures, for all subtables, and removing the need for each of the subtable traversal callback functions to use BAD_MADT_ENTRY.
In theory, as the ACPI specification changes, we would only have to add additional information to the data set describing the MADT subtables in order to continue providing sanity checks, even when new subtables are added.
These patches have been tested on an APM Mustang (arm64) and are known to work there. They have also been cross-compiled for x86 and ia64 with no known failures.
Changes for v4: -- Remove extraneous white space change (Graeme Gregory) -- acpi_parse_entries() changes also needed a check to make sure that only MADT entries used bad_madt_entry() (Sudeep Holla) -- inadvertent use of 01day build noted that bad_madt_entry() can be static, so added it (Sudeep Holla, Fengguang Wu)
Changes for v3: -- Reviewed-and-tested-by from Sudeep Holla for arm64 parts -- Clearer language in error messages (Graeme Gregory, Timur Tabi) -- Double checked that inserting call to bad_madt_entry() into the function acpi_parse_entries() does not impact current behavior (Sudeep Holla) Changes for v2: -- Acked-by on 2/5 from Marc Zyngier and Catalin Marinas for ARM -- Correct faulty end of loop test found by Timur Tabi
Al Stone (5): ACPI: add in a bad_madt_entry() function to eventually replace the macro ACPI / ARM64: remove usage of BAD_MADT_ENTRY/BAD_MADT_GICC_ENTRY ACPI / IA64: remove usage of BAD_MADT_ENTRY ACPI / X86: remove usage of BAD_MADT_ENTRY ACPI: remove definition of BAD_MADT_ENTRY macro
I've queued this up for v4.4, but I had to rebase it on top of some previous changes in my linux-next branch.
Can you please look at my bleeding-edge branch and see if the result of the rebase is as intended? In particular, I'm not sure if we really need to return -EINVAL from acpi_parse_entries_array() when we find a bad MADT entry or it will be sufficient to simply go to the next entry in that case?
Thanks, Rafael