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Date:      Tue, 27 Aug 2002 15:39:59 -0700
From:      Terry Lambert <tlambert2@mindspring.com>
To:        "Moore, Robert" <robert.moore@intel.com>
Cc:        'Mitsuru IWASAKI' <iwasaki@jp.FreeBSD.org>, yb@sainte-barbe.org, acpi-jp@jp.FreeBSD.org, current@freebsd.org, "Grover, Andrew" <andrew.grover@intel.com>
Subject:   Re: [acpi-jp 1735] Re: Call for testers: acpica-unix-20020815
Message-ID:  <3D6BFFBF.42810259@mindspring.com>
References:  <B9ECACBD6885D5119ADC00508B68C1EA0D19B71C@orsmsx107.jf.intel.com>

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"Moore, Robert" wrote:
> I think you are missing something:
> 
> 1) BIOS vendor writes ASL
> 2) BIOS vendor compiles ASL to AML byte-code
> 3) BIOS vendor puts AML into BIOS
> 4) OS gets AML from the BIOS
> 5) OS interprets AML
> 
> The error you are experiencing is in (5).  There is no return statement in
> the original ASL, so there is no return opcode in the AML.  The AML
> interpreter has nothing to "return" and things fall apart.
> 
> However, the error was written in (1) and should have been caught by the ASL
> compiler in (2).   However, there are other ASL compilers out there that do
> not perform such error-checking.  This is how these kinds of problems creep
> into the BIOS AML code.

As a consumer of 1-3, I have zero opportunity to fix the
problem before item #4.

Since use of a trademark or other legal baseball bat (8-))
won't get the code in the BIOS fixed, the only way to make
things work in the short term is to either intervene in step
#4 or in step #5.

In the long term, it'd probably be a good idea to release
the source code for the ASL-to-AML compiler under a strict
license, and displace all the ASL compilers that fail to do
error checking, so problems like this can't arise in the
first place.

I guess I would like to know if the AML can be recognized as
defective by the interpreter, and modify it at step #4 before
interning it for interpretation; Windows has to have *some* way
of dealing with this, short of supplying replacement AML for
every PC ever manufacturered, right?

-- Terry

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