linux-kernel - Re: [PATCH v5 0/5] Provide better MADT subtable sanity checks

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Message-ID: <560BA4C9.7090607@huawei.com>
Date:	Wed, 30 Sep 2015 17:00:57 +0800
From:	Hanjun Guo <guohanjun@...wei.com>
To:	Al Stone <al.stone@...aro.org>, <linux-acpi@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
CC:	<linaro-kernel@...ts.linaro.org>, <linux-ia64@...r.kernel.org>,
	<patches@...aro.org>, <linux-pm@...r.kernel.org>,
	<linaro-acpi@...ts.linaro.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 0/5] Provide better MADT subtable sanity checks

On 2015/9/30 7:45, Al Stone wrote:
> NB: this patch set is for use against the linux-pm bleeding edge branch.
>
> 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 v5:
>    -- 0-day found incorrect data in the table describing allowed MADT
>       subtables; this only affected ACPI 1.0 firmware.  Corrected the
>       data to meet the 1.0b spec.
>    -- Rebase to bleeding-edge branch for Rafael Wysocki; this patch set
>       now requires that a patch set from Marc Zyngier be applied first:
>       https://lkml.org/lkml/2015/9/28/421
>    -- Tested on AMD Seattle (linux-pm tree) also
>
> 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

For this patch set,

Reviewed-by: Hanjun Guo <hanjun.guo@...aro.org>

Thanks
Hanjun

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