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From Gregory Shimansky <gshiman...@gmail.com>
Subject [drlvm] Redesign of hardware exceptions/signals handling
Date Sat, 25 Nov 2006 03:21:22 GMT
On Friday 24 November 2006 18:44 Salikh Zakirov wrote:
> However, these patches somewhat regress in functionality:
> I still haven't figured out how to piggy-back on exception throw
> to call JVMTI callback and to restore stack guard page.
> (the commented out block at the end of nt_exception_filter.cpp was doing it
> before fix).
>
> Any ideas appreciated.

I decided this deserves a separate topic. I think signals on unix deserve 
redesign along with NT exceptions since platform dependent part is actually 
quite small, and benefit is quite bit if we do this.

I've reviewed the patch in HARMONY-2320, the changes are going in the right 
direction except for 2 things.

1. The function vm_identify_eip seems to be called twice now, first in 
vectored_exception_handler_internal, second time in c_exception_handler. The 
function is quite a heavy lookup and it would be better to have it called 
only once. Probably it will require passing one more argument to 
c_exception_handler. Maybe it is better to create a separate place for all 
this stuff in TLS, I mean exception class pointer, registers and in_java 
flag. This would save you from ESP manipulation and make the code more 
portable (any ideas how do these ESP manipulations on IPF? ;) ).

2. JVMTI functionality is going to be broken with this patch. The 
exception_catch handling callback should be changed to accept registers in 
TLS instead of an assembly stub (makes it more portable too). I think JVMTI 
breakpoints handler could be integrated with the new functionality and called 
from inside of c_exception_handler.

I am very glad you've started to change this stuff (especially that you 
comment your code at every significant step). I would really like to help you 
because I've gone through doing a partial fix only for JVMTI, but now that it 
seems like all the rest has to be changed too I can share my experience.

Isn't it better to use conventional DIE instead of assert(!"...")?

-- 
Gregory

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