1      li x15, 5 # this many instructions will raise an exception
 2      la x6, exception_handler
 3      csrw mtvec, x6 # set-up handler
 4      # test read-only CSRs
 5      csrw mvendorid, 1
 6      csrw marchid, 1
 7      csrw mimpid, 1
 8      csrw mhartid, 1
 9      csrw 0xf15, 1  # csrw mconfigptr, 1
10      csrr x1, mvendorid
11      csrr x2, marchid
12      csrr x3, mimpid
13      csrr x4, mhartid
14      csrr x5, 0xf15  # csrr x5, mconfigptr
15      # test writable CSRs
16      csrw mscratch, 4
17      csrr x6, mscratch
18  infloop:
19      j infloop
20  
21  exception_handler:
22     addi x15, x15, -1 # count exceptions
23  
24     csrr x31, mepc    # resume program execution,
25     addi x31, x31, 4   # but skip unimplemented instruction
26     csrw mepc, x31
27     mret