github-mirrors/ibex
1
0
Fork 0
mirror of https://github.com/lowRISC/ibex.git synced 2025-04-23 05:17:12 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

Controller: change behavior of DRET instruction

Browse source 
Executing a DRET instruction outside of debug mode now causes an
illegal instruction exception as mandated by the Debug Spec v0.13.2
p.41.

This resolves lowRISC/ibex#270.
This commit is contained in:
Pirmin Vogel 2019-08-29 11:04:21 +01:00
parent 68b170638a
commit d79722ba47
1 changed files with 10 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

13
rtl/ibex_controller.sv
View file

@ -104,6 +104,8 @@ module ibex_controller (
logic stall;
logic halt_if;
logic halt_id;
logic illegal_dret;
logic illegal_insn;
logic exc_req;
logic exc_req_lsu;
logic special_req;
@ -119,7 +121,7 @@ module ibex_controller (
// glitches
always_ff @(negedge clk_i) begin
// print warning in case of decoding errors
if ((ctrl_fsm_cs == DECODE) && instr_valid_i && illegal_insn_i) begin
if ((ctrl_fsm_cs == DECODE) && instr_valid_i && illegal_insn) begin
$display("%t: Illegal instruction (core %0d) at PC 0x%h: 0x%h", $time, ibex_core.core_id_i,
ibex_id_stage.pc_id_i, ibex_id_stage.instr_rdata_i);
end
@ -134,8 +136,13 @@ module ibex_controller (
assign load_err_d = load_err_i;
assign store_err_d = store_err_i;
// "Executing DRET outside of Debug Mode causes an illegal instruction exception."
// [Debug Spec v0.13.2, p.41]
assign illegal_dret = dret_insn_i & ~debug_mode_q;
assign illegal_insn = illegal_insn_i | illegal_dret;
// exception requests
assign exc_req = ecall_insn_i | ebrk_insn_i | illegal_insn_i | instr_fetch_err_i;
assign exc_req = ecall_insn_i | ebrk_insn_i | illegal_insn | instr_fetch_err_i;
// LSU exception requests
assign exc_req_lsu = store_err_i | load_err_i;
@ -442,7 +449,7 @@ module ibex_controller (
exc_cause_o = EXC_CAUSE_INSTR_ACCESS_FAULT;
csr_mtval_o = pc_id_i;
end else if (illegal_insn_i) begin
end else if (illegal_insn) begin
exc_cause_o = EXC_CAUSE_ILLEGAL_INSN;
csr_mtval_o = instr_is_compressed_i ? {16'b0, instr_compressed_i} : instr_i;