| .option norvc | |
| .text | |
| .global _start | |
| _start: | |
| lla t0, trap | |
| csrw mtvec, t0 | |
| # These are all illegal instructions | |
| csrw time, x0 | |
| .insn i CUSTOM_0, 0, x0, x0, 0x321 | |
| csrw time, x0 | |
| .insn i CUSTOM_0, 0, x0, x0, 0x123 | |
| csrw cycle, x0 | |
| # Success! | |
| li a0, 0 | |
| j _exit | |
| trap: | |
| # When an instruction traps, compare it to the insn in memory. | |
| csrr t0, mepc | |
| csrr t1, mtval | |
| lwu t2, 0(t0) | |
| bne t1, t2, fail | |
| # Skip the insn and continue. | |
| addi t0, t0, 4 | |
| csrw mepc, t0 | |
| mret | |
| fail: | |
| li a0, 1 | |
| # Exit code in a0 | |
| _exit: | |
| lla a1, semiargs | |
| li t0, 0x20026 # ADP_Stopped_ApplicationExit | |
| sd t0, 0(a1) | |
| sd a0, 8(a1) | |
| li a0, 0x20 # TARGET_SYS_EXIT_EXTENDED | |
| # Semihosting call sequence | |
| .balign 16 | |
| slli zero, zero, 0x1f | |
| ebreak | |
| srai zero, zero, 0x7 | |
| j . | |
| .data | |
| .balign 16 | |
| semiargs: | |
| .space 16 |