ACPICA commit 0e24fb67cde08d7df7671d7d7b183490dc79707e
The MLC (Module Level Code) is an ACPICA terminology describing the AML
code out of any control method, its support is an indication of the
interpreter behavior during the table loading.
The original implementation of MLC in ACPICA had several issues:
1. Out of any control method, besides of the object creating opcodes, only
the code blocks wrapped by "If/Else/While" opcodes were supported.
2. The supported MLC code blocks were executed after loading the table
rather than being executed right in place.
============================================================
The demo of this order issue is as follows:
Name (OBJ1, 1)
If (CND1 == 1)
{
Name (OBJ2, 2)
}
Name (OBJ3, 3)
The original MLC support created OBJ2 after OBJ3's creation.
============================================================
Other than these limitations, MLC support in ACPICA looks correct. And
supporting this should be easy/natural for ACPICA, but enabling of this was
blocked by some ACPICA internal and OSPM specific initialization order
issues we've fixed recently. The wrong support started from the following
false bug fixing commit:
Commit: 7f0c826a43
Subject: ACPICA: Add support for module-level executable AML code
Commit: 9a884ab64a
Subject: ACPICA: Add additional module-level code support
...
We can confirm Windows interpreter behavior via reverse engineering means.
It can be proven that not only If/Else/While wrapped code blocks, all
opcodes can be executed at the module level, including operation region
accesses. And it can be proven that the MLC should be executed right in
place, not in such a deferred way executed after loading the table.
And the above facts indeed reflect the spec words around ACPI definition
block tables (DSDT/SSDT/...), the entire table and the Scope object is
defined by the AML specification in BNF style as:
AMLCode := def_block_header term_list
def_scope := scope_op pkg_length name_string term_list
The bodies of the scope opening terms (AMLCode/Scope) are all term_list,
thus the table loading should be no difference than the control method
evaluations as the body of the Method is also defined by the AML
specification as term_list:
def_method := method_op pkg_length name_string method_flags term_list
The only difference is: after evaluating control method, created named
objects may be freed due to no reference, while named objects created by
the table loading should only be freed after unloading the table.
So this patch follows the spec and the de-facto standard behavior, enables
the new grammar (term_list) for the table loading.
By doing so, beyond the fixes to the above issues, we can see additional
differences comparing to the old grammar based table loading:
1. Originally, beyond the scope opening terms (AMLCode/Scope),
If/Else/While wrapped code blocks under the scope creating terms
(Device/power_resource/Processor/thermal_zone) are also supported as
deferred MLC, which violates the spec defined grammar where object_list
is enforced. With MLC support improved as non-deferred, the interpreter
parses such scope creating terms as term_list rather object_list like the
scope opening terms.
After probing the Windows behavior and proving that it also parses these
terms as term_list, we submitted an ECR (Engineering Change Request) to
the ASWG (ACPI Specification Working Group) to clarify this. The ECR is
titled as "ASL Grammar Clarification for Executable AML Opcodes" and has
been accepted by the ASWG. The new grammar will appear in ACPI
specification 6.2.
2. Originally, Buffer/Package/operation_region/create_XXXField/bank_field
arguments are evaluated in a deferred way after loading the table. With
MLC support improved, they are also parsed right in place during the
table loading.
This is also Windows compliant and the only difference is the removal
of the debugging messages implemented before acpi_ds_execute_arguments(),
see Link # [1] for the details. A previous commit should have ensured
that acpi_check_address_range() won't regress.
Note that enabling this feature may cause regressions due to long term
Linux ACPI support on top of the wrong grammar. So this patch also prepares
a global option to be used to roll back to the old grammar during the
period between a regression is reported and the regression is
root-cause-fixed. Lv Zheng.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=112911 # [1]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=117671 # [1]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=153541 # [1]
Link: https://github.com/acpica/acpica/issues/122
Link: https://bugs.acpica.org/show_bug.cgi?id=963
Link: https://github.com/acpica/acpica/commit/0e24fb67
Reported-and-tested-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Reported-by: Ehsan <dashesy@gmail.com>
Reported-and-tested-by: Dutch Guy <lucht_piloot@gmx.net>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
de56ba95e8