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sim: sim_core:insn_fetch/2: refactor, handle TRAP_2, for now by terminating with an error

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This commit is contained in:
Mikael Pettersson
2020-07-29 23:40:11 +02:00
parent a6f5b8446a
commit 0915326622
1 changed files with 30 additions and 9 deletions
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39
erlang/apps/sim/src/sim_core.erl
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@@ -85,14 +85,33 @@ next_pc(#core{pc_offset = PCOffset} = Core, Mem) ->
%% c.f. Toad-1 Architecture Manual, page 41, Figure 1.11
%% Instruction Fetch. This always uses local addressing.
insn_fetch(Core0, Mem) ->
%% TODO: Handle 2.9.6 Overflow Trapping
%% For now, arithmetic overflows are ignored, as if the user had installed a
%% no-op handler, so that C's unsigned arithmetic can work, and stack overflows
%% are treated as fatal errors.
%% TODO: Handle TRAP_2 (Stack Overflow/Underflow)
#core{flags = Flags0} = Core0,
Core = Core0#core{flags = Flags0 band bnot (1 bsl ?PDP10_PF_TRAP_1)},
insn_fetch(Core, Mem) ->
%% Arithmetic and stack overflows set trap flags which are checked after
%% completion of the faulting instruction, i.e., at the start of the next
%% instruction fetch cycle.
#core{flags = Flags} = Core,
%% TRAP_1 and TRAP_2 are adjacent
case (Flags bsr ?PDP10_PF_TRAP_1) band 3 of
0 ->
%% No trap flag set.
insn_fetch1(Core, Mem);
1 ->
%% TRAP_1 (arithmetic overflow) set.
%% For now, arithmetic overflows are ignored as if the user had installed
%% a no-op handler. This is so that C's unsigned arithmetic can work.
%% TODO: Handle 2.9.6 Overflow Trapping
Flags1 = Flags band bnot (1 bsl ?PDP10_PF_TRAP_1),
Core1 = Core#core{flags = Flags1},
insn_fetch1(Core1, Mem);
_ ->
%% TRAP_2 (stack overflow) set.
%% For now, treat this as a fatal error terminating execution.
%% TODO: Handle stack overflow faults properly.
PC = (Core#core.pc_section bsl 18) bor Core#core.pc_offset,
{Core, Mem, {error, {?MODULE, {stack_fault, PC}}}}
end.
insn_fetch1(Core, Mem) ->
PCOffset = Core#core.pc_offset,
case PCOffset =< 8#17 of
true ->
@@ -491,7 +510,9 @@ format_error(Reason) ->
[PC, IR, format_ea(EA)]);
{page_fault, Address, PC, Op, Reason, Cont} ->
io_lib:format("PAGE FAULT: ADDR=~10.8.0b PC=~10.8.0b OP=~p RSN=~p CONT=~p",
[Address, PC, Op, Reason, Cont])
[Address, PC, Op, Reason, Cont]);
{stack_fault, PC} ->
io_lib:format("STACK FAULT: PC=~10.8.0b", [PC])
end.
format_ea(#ea{section = Section, offset = Offset, islocal = IsLocal}) ->