diff options
Diffstat (limited to 'subx/057stop.subx')
| -rw-r--r-- | subx/057stop.subx | 270 |
1 files changed, 135 insertions, 135 deletions
diff --git a/subx/057stop.subx b/subx/057stop.subx index b7ae2fa2..483c9404 100644 --- a/subx/057stop.subx +++ b/subx/057stop.subx @@ -33,177 +33,177 @@ # Its value is its output, computed during stop and available to the test. == code -# instruction effective address operand displacement immediate -# op subop mod rm32 base index scale r32 -# 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes +# instruction effective address operand displacement immediate +# op subop mod rm32 base index scale r32 +# 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes # main: - e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'. -#? e8/call test-stop-skips-returns-on-exit/disp32 - # syscall(exit, Num-test-failures) - 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX - b8/copy-to-EAX 1/imm32 - cd/syscall 0x80/imm8 + e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'. +#? e8/call test-stop-skips-returns-on-exit/disp32 + # syscall(exit, Num-test-failures) + 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX + b8/copy-to-EAX 1/imm32 + cd/syscall 0x80/imm8 # Configure an exit-descriptor for a call pushing 'nbytes' bytes of args to # the stack. # Ugly that we need to know the size of args, but so it goes. tailor-exit-descriptor: # ed : (address exit-descriptor), nbytes : int -> <void> - # prolog - 55/push-EBP - 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP - # save registers - 50/push-EAX - 51/push-ECX - # EAX = nbytes - 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 0/r32/EAX 0xc/disp8 . # copy *(EBP+12) to EAX - # Let X be the value of ESP in the caller, before the call to tailor-exit-descriptor. - # The return address for a call in the caller's body will be at: - # X-8 if the caller takes 4 bytes of args for the exit-descriptor (add 4 bytes for the return address) - # X-12 if the caller takes 8 bytes of args - # ..and so on - # That's the value we need to return: X-nbytes-4 - # - # However, we also need to account for the perturbance to ESP caused by the - # call to tailor-exit-descriptor. It pushes 8 bytes of args followed by 4 - # bytes for the return address and 4 bytes to push EBP above. - # So EBP at this point is X-16. - # - # So the return address for the next call in the caller is: - # EBP+8 if the caller takes 4 bytes of args - # EBP+4 if the caller takes 8 bytes of args - # EBP if the caller takes 12 bytes of args - # EBP-4 if the caller takes 16 bytes of args - # ..and so on - # That's EBP+12-nbytes. + # prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # save registers + 50/push-EAX + 51/push-ECX + # EAX = nbytes + 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 0/r32/EAX 0xc/disp8 . # copy *(EBP+12) to EAX + # Let X be the value of ESP in the caller, before the call to tailor-exit-descriptor. + # The return address for a call in the caller's body will be at: + # X-8 if the caller takes 4 bytes of args for the exit-descriptor (add 4 bytes for the return address) + # X-12 if the caller takes 8 bytes of args + # ..and so on + # That's the value we need to return: X-nbytes-4 + # + # However, we also need to account for the perturbance to ESP caused by the + # call to tailor-exit-descriptor. It pushes 8 bytes of args followed by 4 + # bytes for the return address and 4 bytes to push EBP above. + # So EBP at this point is X-16. + # + # So the return address for the next call in the caller is: + # EBP+8 if the caller takes 4 bytes of args + # EBP+4 if the caller takes 8 bytes of args + # EBP if the caller takes 12 bytes of args + # EBP-4 if the caller takes 16 bytes of args + # ..and so on + # That's EBP+12-nbytes. # option 1: 6 + 3 bytes -#? 2d/subtract 3/mod/direct 0/rm32/EAX . . . . . 8/imm32 # subtract from EAX -#? 8d/copy-address 0/mod/indirect 4/rm32/sib 5/base/EBP 0/index/EAX . 0/r32/EAX . . # copy EBP+EAX to EAX +#? 2d/subtract 3/mod/direct 0/rm32/EAX . . . . . 8/imm32 # subtract from EAX +#? 8d/copy-address 0/mod/indirect 4/rm32/sib 5/base/EBP 0/index/EAX . 0/r32/EAX . . # copy EBP+EAX to EAX # option 2: 2 + 4 bytes - f7 3/subop/negate 3/mod/direct 0/rm32/EAX . . . . . . # negate EAX - 8d/copy-address 1/mod/*+disp8 4/rm32/sib 5/base/EBP 0/index/EAX . 0/r32/EAX 0xc/disp8 . # copy EBP+EAX+12 to EAX - # copy EAX to ed->target - 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 1/r32/ECX 8/disp8 . # copy *(EBP+8) to ECX - 89/copy 0/mod/indirect 1/rm32/ECX . . . 0/r32/EAX . . # copy EAX to *ECX - # initialize ed->value - c7/copy 1/mod/*+disp8 1/rm32/ECX . . . . 4/disp8 0/imm32 # copy to *(ECX+4) - # restore registers - 59/pop-to-ECX - 58/pop-to-EAX - # epilog - 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP - 5d/pop-to-EBP - c3/return + f7 3/subop/negate 3/mod/direct 0/rm32/EAX . . . . . . # negate EAX + 8d/copy-address 1/mod/*+disp8 4/rm32/sib 5/base/EBP 0/index/EAX . 0/r32/EAX 0xc/disp8 . # copy EBP+EAX+12 to EAX + # copy EAX to ed->target + 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 1/r32/ECX 8/disp8 . # copy *(EBP+8) to ECX + 89/copy 0/mod/indirect 1/rm32/ECX . . . 0/r32/EAX . . # copy EAX to *ECX + # initialize ed->value + c7/copy 1/mod/*+disp8 1/rm32/ECX . . . . 4/disp8 0/imm32 # copy to *(ECX+4) + # restore registers + 59/pop-to-ECX + 58/pop-to-EAX + # epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return stop: # ed : (address exit-descriptor), value : int - # no prolog; one way or another, we're going to clobber registers - # EAX = ed - 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 0/r32/EAX 4/disp8 . # copy *(ESP+4) to EAX - # exit(value) if ed->target == 0 - 81 7/subop/compare 0/mod/indirect 0/rm32/EAX . . . . . 0/imm32 # compare *EAX - 75/jump-if-not-equal $stop:fake/disp8 - # syscall(exit, value) - 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 3/r32/EBX 8/disp8 . # copy *(ESP+8) to EBX - b8/copy-to-EAX 1/imm32 - cd/syscall 0x80/imm8 + # no prolog; one way or another, we're going to clobber registers + # EAX = ed + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 0/r32/EAX 4/disp8 . # copy *(ESP+4) to EAX + # exit(value) if ed->target == 0 + 81 7/subop/compare 0/mod/indirect 0/rm32/EAX . . . . . 0/imm32 # compare *EAX + 75/jump-if-not-equal $stop:fake/disp8 + # syscall(exit, value) + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 3/r32/EBX 8/disp8 . # copy *(ESP+8) to EBX + b8/copy-to-EAX 1/imm32 + cd/syscall 0x80/imm8 $stop:fake: - # ed->value = value+1 - 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 1/r32/ECX 8/disp8 . # copy *(ESP+8) to ECX - 41/inc-ECX - 89/copy 1/mod/*+disp8 0/rm32/EAX . . . 1/r32/ECX 4/disp8 . # copy ECX to *(EAX+4) - # non-local jump to ed->target - 8b/copy 0/mod/indirect 0/rm32/EAX . . . 4/r32/ESP . . # copy *EAX to ESP - c3/return # doesn't return to caller + # ed->value = value+1 + 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none . 1/r32/ECX 8/disp8 . # copy *(ESP+8) to ECX + 41/inc-ECX + 89/copy 1/mod/*+disp8 0/rm32/EAX . . . 1/r32/ECX 4/disp8 . # copy ECX to *(EAX+4) + # non-local jump to ed->target + 8b/copy 0/mod/indirect 0/rm32/EAX . . . 4/r32/ESP . . # copy *EAX to ESP + c3/return # doesn't return to caller test-stop-skips-returns-on-exit: - # This looks like the standard prolog, but is here for different reasons. - # A function calling 'stop' can't rely on EBP persisting past the call. - # - # Use EBP here as a stable base to refer to locals and arguments from in the - # presence of push/pop/call instructions. - # *Don't* use EBP as a way to restore ESP. - 55/push-EBP - 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP - # Make room for an exit descriptor on the stack. That's almost always the - # right place for it, available only as long as it's legal to use. Once this - # containing function returns we'll need a new exit descriptor. - # var ed/EAX : (address exit-descriptor) - 81 5/subop/subtract 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # subtract from ESP - 8d/copy-address 0/mod/indirect 4/rm32/sib 4/base/ESP 4/index/none . 0/r32/EAX . . # copy ESP to EAX - # Size the exit-descriptor precisely for the next call below, to _test-stop-1. - # tailor-exit-descriptor(ed, 4) + # This looks like the standard prolog, but is here for different reasons. + # A function calling 'stop' can't rely on EBP persisting past the call. + # + # Use EBP here as a stable base to refer to locals and arguments from in the + # presence of push/pop/call instructions. + # *Don't* use EBP as a way to restore ESP. + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # Make room for an exit descriptor on the stack. That's almost always the + # right place for it, available only as long as it's legal to use. Once this + # containing function returns we'll need a new exit descriptor. + # var ed/EAX : (address exit-descriptor) + 81 5/subop/subtract 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # subtract from ESP + 8d/copy-address 0/mod/indirect 4/rm32/sib 4/base/ESP 4/index/none . 0/r32/EAX . . # copy ESP to EAX + # Size the exit-descriptor precisely for the next call below, to _test-stop-1. + # tailor-exit-descriptor(ed, 4) # push args - 68/push 4/imm32/nbytes-of-args-for-_test-stop-1 - 50/push-EAX + 68/push 4/imm32/nbytes-of-args-for-_test-stop-1 + 50/push-EAX # call - e8/call tailor-exit-descriptor/disp32 + e8/call tailor-exit-descriptor/disp32 # discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP - # call _test-stop-1(ed) + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # call _test-stop-1(ed) # push args - 50/push-EAX + 50/push-EAX # call - e8/call _test-stop-1/disp32 - ## registers except ESP may be clobbered at this point + e8/call _test-stop-1/disp32 + ## registers except ESP may be clobbered at this point # restore args - 58/pop-to-EAX - # check that _test-stop-1 tried to call exit(1) - # check-ints-equal(ed->value, 2, msg) # i.e. stop was called with value 1 + 58/pop-to-EAX + # check that _test-stop-1 tried to call exit(1) + # check-ints-equal(ed->value, 2, msg) # i.e. stop was called with value 1 # push args - 68/push "F - test-stop-skips-returns-on-exit"/imm32 - 68/push 2/imm32 + 68/push "F - test-stop-skips-returns-on-exit"/imm32 + 68/push 2/imm32 # push ed->value - ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX . . . . 4/disp8 . # push *(EAX+4) + ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX . . . . 4/disp8 . # push *(EAX+4) # call - e8/call check-ints-equal/disp32 + e8/call check-ints-equal/disp32 # discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP - # epilog - 5d/pop-to-EBP + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # epilog + 5d/pop-to-EBP # don't restore ESP from EBP; manually reclaim locals - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP - c3/return + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + c3/return _test-stop-1: # ed : (address exit-descriptor) - # prolog - 55/push-EBP - 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP - # _test-stop-2(ed) + # prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # _test-stop-2(ed) # push args - ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 8/disp8 . # push *(EBP+8) + ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 8/disp8 . # push *(EBP+8) # call - e8/call _test-stop-2/disp32 - ## should never get past this point + e8/call _test-stop-2/disp32 + ## should never get past this point # discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP - # signal test failed: check-ints-equal(1, 0, msg) + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP + # signal test failed: check-ints-equal(1, 0, msg) # push args - 68/push "F - test-stop-skips-returns-on-exit"/imm32 - 68/push 0/imm32 - 68/push 1/imm32 + 68/push "F - test-stop-skips-returns-on-exit"/imm32 + 68/push 0/imm32 + 68/push 1/imm32 # call - e8/call check-ints-equal/disp32 + e8/call check-ints-equal/disp32 # discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP - # epilog - 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP - 5d/pop-to-EBP - c3/return + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return _test-stop-2: # ed : (address exit-descriptor) - # prolog - 55/push-EBP - 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP - # call stop(ed, 1) + # prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # call stop(ed, 1) # push args - 68/push 1/imm32 - ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 8/disp8 . # push *(EBP+8) + 68/push 1/imm32 + ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 8/disp8 . # push *(EBP+8) # call - e8/call stop/disp32 - ## should never get past this point - # epilog - 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP - 5d/pop-to-EBP - c3/return + e8/call stop/disp32 + ## should never get past this point + # epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return # vim:nowrap:textwidth=0 |