# A stack looks like this: # top: int # data: (array byte) # prefixed by size as usual # # TODO: is it confusing that the push opcodes grow memory downward, but the # push function grows stacks upward? == code # instruction effective address register 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 clear-stack: # s: (addr stack) # . prologue 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 = s 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 8/disp8 . # copy *(ebp+8) to eax # var max/ecx: (addr byte) = &s->data[s->size] 8b/copy 1/mod/*+disp8 0/rm32/eax . . . 1/r32/ecx 4/disp8 . # copy *(eax+4) to eax 8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/eax 1/index/ecx . 1/r32/ecx 8/disp8 . # copy eax+ecx+8 to ecx # s->top = 0 c7 0/subop/copy 0/mod/direct 0/rm32/eax . . . . . 0/imm32 # copy to *eax # var curr/eax: (addr byte) = s->data 81 0/subop/add 3/mod/direct 0/rm32/eax . . . . . 8/imm32 # add to eax $clear-stack:loop: # if (curr >= max) break 39/compare 3/mod/direct 0/rm32/eax . . . 1/r32/ecx . . # compare eax with ecx 73/jump-if-addr>= $clear-stack:end/disp8 # *curr = 0 c6 0/subop/copy 0/mod/direct 0/rm32/eax . . . . . 0/imm8 # copy byte to *eax # ++curr 40/increment-eax eb/jump $clear-stack:loop/disp8 $clear-stack:end: # . restore registers 59/pop-to-ecx 58/pop-to-eax # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return test-clear-stack: # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # var stack/ecx = stack of size 8 with random data in it 68/push 34/imm32 68/push 35/imm32 68/push 8/imm32/size 68/push 14/imm32/top 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx # clear(stack) # . . push args 51/push-ecx # . . call e8/call clear-stack/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # top should be 0 58/pop-to-eax # . check-ints-equal(eax, 0, msg) # . . push args 68/push "F - test-clear-stack: top"/imm32 68/push 0/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # size should remain 8 58/pop-to-eax # . check-ints-equal(eax, 8, msg) # . . push args 68/push "F - test-clear-stack: size"/imm32 68/push 8/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # first word is 0 58/pop-to-eax # . check-ints-equal(eax, 0, msg) # . . push args 68/push "F - test-clear-stack: data[0..3]"/imm32 68/push 0/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # second word is 0 58/pop-to-eax # . check-ints-equal(eax, 0, msg) # . . push args 68/push "F - test-clear-stack: data[4..7]"/imm32 68/push 0/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return # TODO: make this generic push: # s: (addr stack), n: int # . prologue 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 56/push-esi # esi = s 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi # ecx = s->top 8b/copy 0/mod/indirect 6/rm32/esi . . . 1/r32/ecx . . # copy *esi to ecx # if (s->top >= s->size) abort 39/compare 1/mod/*+disp8 6/rm32/esi . . . 1/r32/ecx 4/disp8 . # compare *(esi+4) and ecx 7e/jump-if-<= $push:abort/disp8 # s->data[s->top] = n 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0xc/disp8 . # copy *(ebp+12) to eax 89/copy 1/mod/*+disp8 4/rm32/sib 6/base/esi 1/index/ecx . 0/r32/eax 8/disp8 . # copy eax to *(esi+ecx+8) # s->top += 4 81 0/subop/add 0/mod/direct 6/rm32/esi . . . . . 4/imm32 # subtract from *esi $push:end: # . restore registers 5e/pop-to-esi 59/pop-to-ecx 58/pop-to-eax # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return $push:abort: # print(stderr, "error: push: no space left") # . write-buffered(Stderr, "error: push: no space left") # . . push args 68/push "error: push: no space left"/imm32 68/push Stderr/imm32 # . . call e8/call write-buffered/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # . flush(Stderr) # . . push args 68/push Stderr/imm32 # . . call e8/call flush/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # . syscall(exit, 1) bb/copy-to-ebx 1/imm32 e8/call syscall_exit/disp32 # never gets here test-push: # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # var stack/ecx = empty stack of size 8 68/push 0/imm32 68/push 0/imm32 68/push 8/imm32/size 68/push 0/imm32/top 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx # push(stack, 0x42) # . . push args 68/push 0x42/imm32 51/push-ecx # . . call e8/call push/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # check top 58/pop-to-eax # . check-ints-equal(eax, 4, msg) # . . push args 68/push "F - test-push: top"/imm32 68/push 4/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # check size 58/pop-to-eax # . check-ints-equal(eax, 8, msg) # . . push args 68/push "F - test-push: size"/imm32 68/push 8/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # first word is 0x42 58/pop-to-eax # . check-ints-equal(eax, 0x42, msg) # . . push args 68/push "F - test-push: data[0..3]"/imm32 68/push 0x42/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # second word is 0 58/pop-to-eax # . check-ints-equal(eax, 0, msg) # . . push args 68/push "F - test-push: data[4..7]"/imm32 68/push 0/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return # TODO: make this generic pop: # s: (addr stack) -> n/eax: int # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # . save registers 51/push-ecx 56/push-esi # esi = s 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi # if (s->top <= 0) abort 81 7/subop/compare 0/mod/indirect 6/rm32/esi . . . . . 0/imm32 # compare *esi 7e/jump-if-<= $pop:abort/disp8 # s->top -= 4 81 5/subop/subtract 0/mod/direct 6/rm32/esi . . . . . 4/imm32 # subtract from *esi # eax = s->data[s->top] 8b/copy 0/mod/indirect 6/rm32/esi . . . 1/r32/ecx . . # copy *esi to ecx 8b/copy 1/mod/*+disp8 4/rm32/sib 6/base/esi 1/index/ecx . 0/r32/eax 8/disp8 . # copy *(esi+ecx+8) to eax # s->data[s->top] = 0 c7 0/subop/copy 1/mod/*+disp8 4/rm32/sib 6/base/esi 1/index/ecx . 0/r32/eax 8/disp8 0/imm32 # copy to *(esi+ecx+8) $pop:end: # . restore registers 5e/pop-to-esi 59/pop-to-ecx # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return $pop:abort: # print(stderr, "error: pop: nothing left in stack") # . write-buffered(Stderr, "error: pop: nothing left in stack") # . . push args 68/push "error: pop: nothing left in stack"/imm32 68/push Stderr/imm32 # . . call e8/call write-buffered/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # . flush(Stderr) # . . push args 68/push Stderr/imm32 # . . call e8/call flush/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # . syscall(exit, 1) bb/copy-to-ebx 1/imm32 e8/call syscall_exit/disp32 # never gets here test-pop: # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # var stack/ecx = stack of size 8 containing just 0x42 68/push 0/imm32 68/push 0x42/imm32 68/push 8/imm32/size 68/push 4/imm32/top 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx # eax = pop(stack) # . . push args 51/push-ecx # . . call e8/call pop/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # check-ints-equal(eax, 0x42, msg) # . . push args 68/push "F - test-pop: result"/imm32 68/push 0x42/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # check top 58/pop-to-eax # . check-ints-equal(eax, 0, msg) # . . push args 68/push "F - test-pop: top"/imm32 68/push 0/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # check size 58/pop-to-eax # . check-ints-equal(eax, 8, msg) # . . push args 68/push "F - test-pop: size"/imm32 68/push 8/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return # TODO: make this generic top: # s: (addr stack) -> n/eax: int # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # . save registers 51/push-ecx 56/push-esi # esi = s 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi # if (s->top <= 0) abort 81 7/subop/compare 0/mod/indirect 6/rm32/esi . . . . . 0/imm32 # compare *esi 7e/jump-if-<= $top:abort/disp8 # n = s->data[s->top - 4] 8b/copy 0/mod/indirect 6/rm32/esi . . . 1/r32/ecx . . # copy *esi to ecx 81 5/subop/subtract 3/mod/direct 1/rm32/ecx . . . . . 4/imm32 # subtract from ecx 8b/copy 1/mod/*+disp8 4/rm32/sib 6/base/esi 1/index/ecx . 0/r32/eax 8/disp8 . # copy *(esi+ecx+8) to eax $top:end: # . restore registers 5e/pop-to-esi 59/pop-to-ecx # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return $top:abort: # print(stderr, "error: top: nothing left in stack") # . write-buffered(Stderr, "error: top: nothing left in stack") # . . push args 68/push "error: top: nothing left in stack"/imm32 68/push Stderr/imm32 # . . call e8/call write-buffered/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # . flush(Stderr) # . . push args 68/push Stderr/imm32 # . . call e8/call flush/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # . syscall(exit, 1) bb/copy-to-ebx 1/imm32 e8/call syscall_exit/disp32 # never gets here test-top: # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # var stack/ecx = stack of size 8 containing just 0x42 68/push 0/imm32 68/push 0x42/imm32 68/push 8/imm32/size 68/push 4/imm32/top 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx # eax = top(stack) # . . push args 51/push-ecx # . . call e8/call top/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # check-ints-equal(eax, 42, msg") # . . push args 68/push "F - test-top: result"/imm32 68/push 0x42/imm32 50/push-eax # . . call e8/call check-ints-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp # . epilogue 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