[Openmcl-devel] freshly built wx86cl64.exe crashes on start

Bharat Shetty bshetty at gmail.com
Fri Jan 6 14:01:39 PST 2023

Is there some place we can get more details on the start up code/low
address stuff in lisp-kernel, LAP, level-0 etc.? The info in the current
and old ccl manual at trac is bit high level.


On Thu, Jan 5, 2023 at 2:03 PM Bharat Shetty <bshetty at gmail.com> wrote:

> Unfortunately yes in low memory for now. But as I pointed earlier there
> might be issues with heap locations as well (windows handling FTH).
> Regards,
> Bharat
> On Thu, Jan 5, 2023 at 5:27 AM R. Matthew Emerson <rme at acm.org> wrote:
>> > On Jan 4, 2023, at 3:15 PM, Bharat Shetty <bshetty at gmail.com> wrote:
>> >
>> > Since two days wx86cl64.exe has been behaving erratically (both the
>> version i downloaded and built using gccv4.7.1) it has been crashing
>> randomly at startup and emacs is unable to start it with slime. I suspect
>> this might be to do with some security patches installed.
>> >
>> > So I looked into the windows security controls. Turns out windows
>> defender lets us configure "exploit protection setting" by configuring the
>> following parameters
>> >     •
>> > control flow guard CFG
>> >     • Data Execution Prevention DEP
>> >     • Mandatory ASLR (force randomisation for images - force relocation
>> of images not compiled with Bottom-up ASLR ) -- off by default for now
>> >     • Randomise memory allocation (Bottom-up ASLR) -- on by default
>> >     • High Entropy ASLR - needs Bottom-up ASLR to be ON
>> >     • validate execution chains (SEHOP)
>> >     • validate heap integrity - terminate process when heap corruption
>> os detected
>> >
>> > I observed we can get wxcl8664 to run with 'Mandatory ASLR' and 'High
>> Entropy ASLR' turned off and with all other options enabled. So even if gcc
>> were to enable us to build non PIE position independant executable, it is
>> just a matter of time before no-pie apps and ccl stops running on windows.
>> >
>> > The only way we can keep ccl running is making the code relocatable
>> (PIE) at the earliest. The bright spot is it still runs on linux :)
>> The x86 port of CCL uses absolute addresses to reference code and other
>> data in low memory. Is this what the problem is?
>> Changing that would be a big hassle.
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