# 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