For a research project, I needed to generate a lot of exceptions. For
this, I repurposed the illegal instruction exception. I found a bug where
the EPCR was loaded with the wrong address. The patch below fixes this
problem and has serviced over 1 billion exceptions both with Linux and in
bare metal.
At a higher level, is there any reason why different exceptions should have
different EPCR values? It seems like having a single EPCR selection logic
would simplify things and probably eliminate subtle (hard to detect and
correct) bugs. Note that the patch I submitted matches (coincidentally)
the range exception.
Index: or1200_except.v
===================================================================
--- or1200_except.v (revision 868)
+++ or1200_except.v (working copy)
@@ -518,7 +518,9 @@
except_type <= `OR1200_EXCEPT_ILLEGAL;
eear <= ex_pc;
epcr <= ex_dslot ?
- wb_pc : ex_pc;
+ wb_pc : delayed1_ex_dslot ?
+ dl_pc : delayed2_ex_dslot ?
+ id_pc : ex_pc;
dsx <= ex_dslot;
end
`endif
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