# Helper to dynamically allocate memory on the heap.
#
# We'd like to be able to write tests for functions that allocate memory,
# making assertions on the precise addresses used. To achieve this we'll pass
# in an *allocation descriptor* to allocate from.
#
# Allocation descriptors are also useful outside of tests. Assembly and machine
# code are of necessity unsafe languages, and one of the most insidious kinds
# of bugs unsafe languages expose us to are dangling pointers to memory that
# has been freed and potentially even reused for something totally different.
# To reduce the odds of such "use after free" errors, SubX programs tend to not
# reclaim and reuse dynamically allocated memory. (Running out of memory is far
# easier to debug.) Long-running programs that want to reuse memory are mostly
# on their own to be careful. However, they do get one bit of help: they can
# carve out chunks of memory and then allocate from them manually using this
# very same 'allocate' helper. They just need a new allocation descriptor for
# their book-keeping.
== data
# Allocations are returned in a handle, which consists of an alloc-id and a payload.
# The alloc-id helps detect use-after-free errors.
Handle-size: # (addr int)
8/imm32
# A default allocation descriptor for programs to use.
Heap: # allocation-descriptor
# curr
0/imm32
# limit
0/imm32
# a reasonable default
Heap-size: # int
0x800000/imm32/8MB
Next-alloc-id: # int
0x100/imm32 # save a few alloc ids for fake handles
== 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
# Let's start initializing the default allocation descriptor.
Entry:
# initialize heap
# . Heap = new-segment(Heap-size)
# . . push args
68/push Heap/imm32
ff 6/subop/push 0/mod/indirect 5/rm32/.disp32 . . . Heap-size/disp32 # push *Heap-size
# . . call
e8/call new-segment/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
$array-equal-main:end:
# 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
e8/call syscall_exit/disp32
# Allocate and clear 'n' bytes of memory from an allocation-descriptor 'ad'.
# Abort if there isn't enough memory in 'ad'.
allocate: # ad: (addr allocation-descriptor), n: int, out: (addr handle _)
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# . save registers
50/push-eax
# allocate-raw(ad, n, out)
# . . push args
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0x10/disp8 . # push *(ebp+16)
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12)
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8)
# . . call
e8/call allocate-raw/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# eax = out->payload + 4
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0x10/disp8 . # copy *(ebp+16) to eax
8b/copy 1/mod/*+disp8 0/rm32/eax . . . 0/r32/eax 4/disp8 . # copy *(eax+4) to eax
05/add-to-eax 4/imm32
# zero-out(eax, n)
# . . push args
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12)
50/push-eax
# . . call
e8/call zero-out/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
$allocate:end:
# . restore registers
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
# Claim the next 'n' bytes of memory starting at ad->curr and update ad->curr.
# Abort if there isn't enough memory in 'ad'.
allocate-raw: # ad: (addr allocation-descriptor), n: int, out: (addr handle _)
# . 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
52/push-edx
53/push-ebx
56/push-esi
57/push-edi
# ecx = ad
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 8/disp8 . # copy *(ebp+8) to ecx
# edx = out
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0x10/disp8 . # copy *(ebp+16) to edx
# ebx = n
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 3/r32/ebx 0xc/disp8 . # copy *(ebp+12) to ebx
# out->alloc-id = Next-alloc-id
8b/copy 0/mod/indirect 5/rm32/.disp32 . . 0/r32/eax Next-alloc-id/disp32 # copy *Next-alloc-id to eax
89/copy 0/mod/indirect 2/rm32/edx . . . 0/r32/eax . . # copy eax to *edx
# out->payload = ad->curr
8b/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy *ecx to eax
$allocate-raw:save-payload-in-eax:
89/copy 1/mod/*+disp8 2/rm32/edx . . . 0/r32/eax 4/disp8 . # copy eax to *(edx+4)
# *out->payload = Next-alloc-id
8b/copy 1/mod/*+disp8 2/rm32/edx . . . 7/r32/edi 4/disp8 . # copy *(edx+4) to edi
8b/copy 0/mod/indirect 5/rm32/.disp32 . . 6/r32/esi Next-alloc-id/disp32 # copy *Next-alloc-id to esi
89/copy 0/mod/indirect 7/rm32/edi . . . 6/r32/esi . . # copy esi to *edi
$allocate-raw:increment-next-alloc-id:
# increment *Next-alloc-id
ff 0/subop/increment 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 # increment *Next-alloc-id
# check if there's enough space
# TODO: move this check up before any state updates when we support error recovery
8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/eax 3/index/ebx . 0/r32/eax 4/disp8 . # copy eax+ebx+4 to eax
3b/compare 1/mod/*+disp8 1/rm32/ecx . . . 0/r32/eax 4/disp8 . # compare eax with *(ecx+4)
73/jump-if->=-signed $allocate-raw:abort/disp8
$allocate-raw:commit:
# ad->curr += n+4
89/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy eax to *ecx
$allocate-raw:end:
# . restore registers
5f/pop-to-edi
5e/pop-to-esi
5b/pop-to-ebx
5a/pop-to-edx
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
$allocate-raw:abort:
# . _write(2/stderr, error)
# . . push args
68/push "allocate: failed\n"/imm32
68/push 2/imm32/stderr
# . . call
e8/call _write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# . syscall(exit, 1)
bb/copy-to-ebx 1/imm32
e8/call syscall_exit/disp32
# never gets here
test-allocate-raw-success:
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# var ad/ecx: allocation-descriptor
68/push 0/imm32/limit
68/push 0/imm32/curr
89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
# ad = new-segment(512)
# . . push args
51/push-ecx
68/push 0x200/imm32
# . . call
e8/call new-segment/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# var expected-payload/ebx = ad->curr
8b/copy 0/mod/indirect 1/rm32/ecx . . . 3/r32/ebx . . # copy *ecx to ebx
# var h/edx: handle = {0, 0}
68/push 0/imm32
68/push 0/imm32
89/copy 3/mod/direct 2/rm32/edx . . . 4/r32/esp . . # copy esp to edx
# *Next-alloc-id = 0x34
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 0x34/imm32 # copy to *Next-alloc-id
# allocate-raw(ad, 3, h)
# . . push args
52/push-edx
68/push 3/imm32
51/push-ecx
# . . call
e8/call allocate-raw/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# check-ints-equal(h->alloc-id, 0x34, msg)
# . . push args
68/push "F - test-allocate-raw-success: sets alloc-id in handle"/imm32
68/push 0x34/imm32
ff 6/subop/push 0/mod/indirect 2/rm32/edx . . . . . . # push *edx
# . . 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-ints-equal(h->payload, expected-payload, msg)
# . . push args
68/push "F - test-allocate-raw-success: sets payload in handle"/imm32
53/push-ebx
ff 6/subop/push 1/mod/*+disp8 2/rm32/edx . . . . 4/disp8 . # push *(edx+4)
# . . 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-ints-equal(h->payload->alloc-id, 0x34, msg)
# . . push args
68/push "F - test-allocate-raw-success: sets alloc-id in payload"/imm32
68/push 0x34/imm32
ff 6/subop/push 0/mod/indirect 3/rm32/ebx . . . . . . # push *ebx
# . . 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-ints-equal(*Next-alloc-id, 0x35, msg)
# . . push args
68/push "F - test-allocate-raw-success: increments Next-alloc-id"/imm32
68/push 0x35/imm32
ff 6/subop/push 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 # push *Next-alloc-id
# . . 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-ints-equal(ad->curr - expected-payload, 3 + 4 for alloc-id, msg)
# . . push args
68/push "F - test-allocate-raw-success: updates allocation descriptor"/imm32
68/push 7/imm32
8b/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy *ecx to eax
29/subtract 3/mod/direct 0/rm32/eax . . . 3/r32/ebx . . # subtract ebx from eax
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
# clean up
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 0x100/imm32 # copy to *Next-alloc-id
# . reclaim locals
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0x10/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
lookup: # h: (handle _T) -> result/eax: (addr _T)
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# . save registers
51/push-ecx
# eax = 0
31/xor 3/mod/direct 0/rm32/eax . . . 0/r32/eax . . # clear eax
# ecx = handle->alloc_id
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 8/disp8 . # copy *(ebp+8) to ecx
# if (ecx == 0) return 0
81 7/subop/compare 3/mod/direct 1/rm32/ecx . . . . . 0/imm32 # compare ecx
74/jump-if-= $lookup:end/disp8
# eax = handle->address (payload)
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0xc/disp8 . # copy *(ebp+12) to eax
# if (ecx != *eax) abort
39/compare 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # compare *eax and ecx
75/jump-if-!= $lookup:abort/disp8
# add 4 to eax
05/add-to-eax 4/imm32
$lookup:end:
# . restore registers
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
$lookup:abort:
# . _write(2/stderr, msg)
# . . push args
68/push "lookup failed\n"/imm32
68/push 2/imm32/stderr
# . . call
e8/call _write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# . syscall(exit, 1)
bb/copy-to-ebx 1/imm32/exit-status
e8/call syscall_exit/disp32
test-lookup-success:
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# var ad/ebx: allocation-descriptor
68/push 0/imm32/limit
68/push 0/imm32/curr
89/copy 3/mod/direct 3/rm32/ebx . . . 4/r32/esp . . # copy esp to ebx
# ad = new-segment(512)
# . . push args
53/push-ebx
68/push 0x200/imm32
# . . call
e8/call new-segment/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# var handle/ecx: handle
68/push 0/imm32/address
68/push 0/imm32/alloc-id
89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
# var old-top/edx = ad->curr
8b/copy 0/mod/indirect 3/rm32/ebx . . . 2/r32/edx . . # copy *ebx to edx
# allocate-raw(ad, 2, handle)
# . . push args
51/push-ecx
68/push 2/imm32/size
53/push-ebx
# . . call
e8/call allocate-raw/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# eax = lookup(handle)
# . . push args
ff 6/subop/push 1/mod/*+disp8 1/rm32/ecx . . . . 4/disp8 . # push *(ecx+4)
ff 6/subop/push 0/mod/indirect 1/rm32/ecx . . . . . . # push *ecx
# . . call
e8/call lookup/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# eax contains old top of heap, except skipping the alloc-id in the payload
# . check-ints-equal(eax, old-top+4, msg)
# . . push args
68/push "F - test-lookup-success"/imm32
81 0/subop/add 3/mod/direct 2/rm32/edx . . . . . 4/imm32 # add to edx
52/push-edx
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
# clean up
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 0x100/imm32 # copy to *Next-alloc-id
# . reclaim locals
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0x10/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
test-lookup-null-returns-null:
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# var handle/ecx: handle
68/push 0/imm32/address
68/push 0/imm32/alloc-id
89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
# eax = lookup(handle)
# . . push args
ff 6/subop/push 1/mod/*+disp8 1/rm32/ecx . . . . 4/disp8 . # push *(ecx+4)
ff 6/subop/push 0/mod/indirect 1/rm32/ecx . . . . . . # push *ecx
# . . call
e8/call lookup/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-ints-equal(eax, 0, msg)
# . . push args
68/push "F - test-lookup-null-returns-null"/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
# . reclaim locals
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/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
_pending-test-lookup-failure:
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# var heap/esi: allocation-descriptor
68/push 0/imm32/limit
68/push 0/imm32/curr
89/copy 3/mod/direct 6/rm32/esi . . . 4/r32/esp . . # copy esp to esi
# heap = new-segment(512)
# . . push args
56/push-esi
68/push 0x200/imm32
# . . call
e8/call new-segment/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# var h1/ecx: handle
68/push 0/imm32/address
68/push 0/imm32/alloc-id
89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
# var old_top/ebx = heap->curr
8b/copy 0/mod/indirect 6/rm32/esi . . . 3/r32/ebx . . # copy *esi to ebx
# first allocation, to h1
# . allocate(heap, 2, h1)
# . . push args
51/push-ecx
68/push 2/imm32/size
56/push-esi
# . . call
e8/call allocate/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# reset heap->curr to mimic reclamation
89/copy 0/mod/indirect 6/rm32/esi . . . 3/r32/ebx . . # copy ebx to *esi
# second allocation that returns the same address as the first
# var h2/edx: handle
68/push 0/imm32/address
68/push 0/imm32/alloc-id
89/copy 3/mod/direct 2/rm32/edx . . . 4/r32/esp . . # copy esp to edx
# . allocate(heap, 2, h2)
# . . push args
52/push-edx
68/push 2/imm32/size
56/push-esi
# . . call
e8/call allocate/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# check-ints-equal(h1->address, h2->address, msg)
# . . push args
68/push "F - test-lookup-failure"/imm32
ff 6/subop/push 1/mod/*+disp8 2/rm32/ecx . . . . 4/disp8 . # push *(edx+4)
ff 6/subop/push 1/mod/*+disp8 1/rm32/ecx . . . . 4/disp8 . # push *(ecx+4)
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# lookup(h1) should crash
# . . push args
ff 6/subop/push 1/mod/*+disp8 1/rm32/ecx . . . . 4/disp8 . # push *(ecx+4)
ff 6/subop/push 0/mod/indirect 1/rm32/ecx . . . . . . # push *ecx
# . . call
e8/call lookup/disp32
# should never get past this point
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# clean up
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 0x100/imm32 # copy to *Next-alloc-id
# . reclaim locals
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/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
# when comparing handles, just treat them as pure values
handle-equal?: # a: (handle _T), b: (handle _T) -> result/eax: boolean
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# . save registers
51/push-ecx
# eax = false
b8/copy-to-eax 0/imm32/false
$handle-equal?:compare-alloc-id:
# ecx = a->alloc_id
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 8/disp8 . # copy *(ebp+8) to ecx
# if (ecx != b->alloc_id) return false
39/compare 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0x10/disp8 . # compare ecx and *(ebp+16)
75/jump-if-!= $handle-equal?:end/disp8
$handle-equal?:compare-address:
# ecx = handle->address
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0xc/disp8 . # copy *(ebp+12) to ecx
# if (ecx != b->address) return false
39/compare 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0x14/disp8 . # compare ecx and *(ebp+20)
75/jump-if-!= $handle-equal?:end/disp8
$handle-equal?:return-true:
# return true
b8/copy-to-eax 1/imm32/true
$handle-equal?:end:
# . restore registers
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
copy-handle: # src: (handle _T), dest: (addr handle _T)
# . 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
# ecx = dest
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0x10/disp8 . # copy *(ebp+16) to ecx
# *dest = src
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 8/disp8 . # copy *(ebp+8) to eax
89/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy eax to *ecx
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0xc/disp8 . # copy *(ebp+12) to eax
89/copy 1/mod/*+disp8 1/rm32/ecx . . . 0/r32/eax 4/disp8 . # copy eax to *(ecx+4)
$copy-handle: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
# helper: create a nested allocation descriptor (useful for tests)
allocate-region: # ad: (addr allocation-descriptor), n: int, out: (addr handle allocation-descriptor)
# . 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
# allocate(ad, n, out)
# . . push args
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0x10/disp8 . # push *(ebp+16)
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12)
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8)
# . . call
e8/call allocate/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# eax = out->payload
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0x10/disp8 . # copy *(ebp+16) to eax
8b/copy 1/mod/*+disp8 0/rm32/eax . . . 0/r32/eax 4/disp8 . # copy *(eax+4) to eax
# skip payload->allocid
05/add-to-eax 4/imm32
# if (eax == 0) abort
3d/compare-eax-and 0/imm32
74/jump-if-= $allocate-region:abort/disp8
# earmark 8 bytes at the start for a new allocation descriptor
# . *eax = eax + 8
89/copy 3/mod/direct 1/rm32/ecx . . . 0/r32/eax . . # copy eax to ecx
81 0/subop/add 3/mod/direct 1/rm32/ecx . . . . . 8/imm32 # add to ecx
89/copy 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # copy ecx to *eax
# . *(eax+4) = eax + n
89/copy 3/mod/direct 1/rm32/ecx . . . 0/r32/eax . . # copy eax to ecx
03/add 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0xc/disp8 . # add *(ebp+12) to ecx
89/copy 1/mod/*+disp8 0/rm32/eax . . . 1/r32/ecx 4/disp8 . # copy ecx to *(eax+4)
# . restore registers
59/pop-to-ecx
58/pop-to-eax
# . epilogue
89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
5d/pop-to-ebp
c3/return
# We could create a more general '$abort' jump target, but then we'd need to do
# a conditional jump followed by loading the error message and an unconditional
# jump. Or we'd need to unconditionally load the error message before a
# conditional jump, even if it's unused the vast majority of the time. This way
# we bloat a potentially cold segment in RAM so we can abort with a single
# instruction.
$allocate-region:abort:
# . _write(2/stderr, error)
# . . push args
68/push "allocate-region: failed to allocate\n"/imm32
68/push 2/imm32/stderr
# . . call
e8/call _write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# . syscall(exit, 1)
bb/copy-to-ebx 1/imm32
e8/call syscall_exit/disp32
# never gets here
# Claim the next 'n+4' bytes of memory and initialize the first 4 to n.
# Abort if there isn't enough memory in 'ad'.
allocate-array: # ad: (addr allocation-descriptor), n: int, out: (addr handle _)
# . 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
52/push-edx
# ecx = n
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0xc/disp8 . # copy *(ebp+12) to ecx
# var size/edx: int = n+4
8d/copy-address 1/mod/*+disp8 1/rm32/ecx . . . 2/r32/edx 4/disp8 . # copy ecx+4 to edx
# allocate(ad, size, out)
# . . push args
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0x10/disp8 . # push *(ebp+16)
52/push-edx
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8)
# . . call
e8/call allocate/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# *out->payload = n
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0x10/disp8 . # copy *(ebp+16) to eax
8b/copy 1/mod/*+disp8 0/rm32/eax . . . 0/r32/eax 4/disp8 . # copy *(eax+4) to eax
# . skip payload->allocid
05/add-to-eax 4/imm32
# .
89/copy 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # copy ecx to *eax
$allocate-array:end:
# . restore registers
5a/pop-to-edx
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-allocate-array:
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# var ad/ecx: allocation-descriptor
68/push 0/imm32/limit
68/push 0/imm32/curr
89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
# ad = new-segment(512)
# . . push args
51/push-ecx
68/push 0x200/imm32
# . . call
e8/call new-segment/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# var expected-payload/ebx = ad->curr
8b/copy 0/mod/indirect 1/rm32/ecx . . . 3/r32/ebx . . # copy *ecx to ebx
# var h/edx: handle = {0, 0}
68/push 0/imm32
68/push 0/imm32
89/copy 3/mod/direct 2/rm32/edx . . . 4/r32/esp . . # copy esp to edx
# *Next-alloc-id = 0x34
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 0x34/imm32 # copy to *Next-alloc-id
# allocate-array(ad, 3, h)
# . . push args
52/push-edx
68/push 3/imm32
51/push-ecx
# . . call
e8/call allocate-array/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# check-ints-equal(h->alloc-id, 0x34, msg)
# . . push args
68/push "F - test-allocate-array: sets alloc-id in handle"/imm32
68/push 0x34/imm32
ff 6/subop/push 0/mod/indirect 2/rm32/edx . . . . . . # push *edx
# . . 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-ints-equal(h->payload, expected-payload, msg)
# . . push args
68/push "F - test-allocate-array: sets payload in handle"/imm32
53/push-ebx
ff 6/subop/push 1/mod/*+disp8 2/rm32/edx . . . . 4/disp8 . # push *(edx+4)
# . . 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-ints-equal(h->payload->alloc-id, 0x34, msg)
# . . push args
68/push "F - test-allocate-array: sets alloc-id in payload"/imm32
68/push 0x34/imm32
ff 6/subop/push 0/mod/indirect 3/rm32/ebx . . . . . . # push *ebx
# . . 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-ints-equal(h->payload->size, 3, msg)
# . . push args
68/push "F - test-allocate-array: sets array size in payload"/imm32
68/push 3/imm32
ff 6/subop/push 1/mod/*+disp8 3/rm32/ebx . . . . 4/disp8 . # push *(ebx+4)
# . . 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-ints-equal(*Next-alloc-id, 0x35, msg)
# . . push args
68/push "F - test-allocate-array: increments Next-alloc-id"/imm32
68/push 0x35/imm32
ff 6/subop/push 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 # push *Next-alloc-id
# . . 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-ints-equal(ad->curr - expected-payload, 3 + 4 for alloc-id + 4 for array size, msg)
# . . push args
68/push "F - test-allocate-array: updates allocation descriptor"/imm32
68/push 0xb/imm32
8b/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy *ecx to eax
29/subtract 3/mod/direct 0/rm32/eax . . . 3/r32/ebx . . # subtract ebx from eax
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
# clean up
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 1/imm32 # copy to *Next-alloc-id
# . reclaim locals
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0x10/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
copy-array: # ad: (addr allocation-descriptor), src: (addr array _T), out: (addr handle array _T)
# . 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
52/push-edx
56/push-esi
# esi = src
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 0xc/disp8 . # copy *(ebp+12) to esi
# var size/ecx: int = src->size+4
8b/copy 0/mod/indirect 6/rm32/esi . . . 1/r32/ecx . . # copy *esi to ecx
81 0/subop/add 3/mod/direct 1/rm32/ecx . . . . . 4/imm32 # add to ecx
# allocate(ad, size, out)
# . . push args
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0x10/disp8 . # push *(ebp+16)
51/push-ecx
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8)
# . . call
e8/call allocate/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# var payload/eax: (addr byte) = out->payload
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0x10/disp8 . # copy *(ebp+16) to eax
8b/copy 1/mod/*+disp8 0/rm32/eax . . . 0/r32/eax 4/disp8 . # copy *(eax+4) to eax
# . skip payload->allocid
05/add-to-eax 4/imm32
# var max/ecx: (addr byte) = payload + size
01/add 3/mod/direct 1/rm32/ecx . . . 0/r32/eax . . # add eax to ecx
# _append-4(payload, max, src, &src->data[src->size])
# . . push &src->data[src->size]
8b/copy 0/mod/indirect 6/rm32/esi . . . 2/r32/edx . . # copy *esi to edx
8d/copy-address 1/mod/*+disp8 4/rm32/sib 6/base/esi 2/index/edx . 2/r32/edx 4/disp8 . # copy esi+edx+4 to edx
52/push-edx
# . . push src
56/push-esi
# . . push max
51/push-ecx
# . . push payload
50/push-eax
# . . call
e8/call _append-4/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0x10/imm32 # add to esp
$copy-array:end:
# . restore registers
5e/pop-to-esi
5a/pop-to-edx
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-copy-array:
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# var src/esi: (addr array int) = [3, 4, 5]
68/push 5/imm32
68/push 4/imm32
68/push 3/imm32
68/push 0xc/imm32/size
89/copy 3/mod/direct 6/rm32/esi . . . 4/r32/esp . . # copy esp to esi
# var ad/ecx: allocation-descriptor
68/push 0/imm32/limit
68/push 0/imm32/curr
89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
# ad = new-segment(512)
# . . push args
51/push-ecx
68/push 0x200/imm32
# . . call
e8/call new-segment/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# var expected-payload/ebx = ad->curr
8b/copy 0/mod/indirect 1/rm32/ecx . . . 3/r32/ebx . . # copy *ecx to ebx
# var h/edx: handle = {0, 0}
68/push 0/imm32
68/push 0/imm32
89/copy 3/mod/direct 2/rm32/edx . . . 4/r32/esp . . # copy esp to edx
# *Next-alloc-id = 0x34
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 0x34/imm32 # copy to *Next-alloc-id
# copy-array(ad, src, h)
# . . push args
52/push-edx
56/push-esi
51/push-ecx
# . . call
e8/call copy-array/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# check-ints-equal(h->alloc-id, 0x34, msg)
# . . push args
68/push "F - test-copy-array: sets alloc-id in handle"/imm32
68/push 0x34/imm32
ff 6/subop/push 0/mod/indirect 2/rm32/edx . . . . . . # push *edx
# . . 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-ints-equal(h->payload, expected-payload, msg)
# . . push args
68/push "F - test-copy-array: sets payload in handle"/imm32
53/push-ebx
ff 6/subop/push 1/mod/*+disp8 2/rm32/edx . . . . 4/disp8 . # push *(edx+4)
# . . 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-ints-equal(h->payload->alloc-id, 0x34, msg)
# . . push args
68/push "F - test-copy-array: sets alloc-id in payload"/imm32
68/push 0x34/imm32
ff 6/subop/push 0/mod/indirect 2/rm32/edx . . . . . . # push *edx
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# var payload/eax: (addr int) = lookup(h)
# . . push args
ff 6/subop/push 1/mod/*+disp8 2/rm32/edx . . . . 4/disp8 . # push *(edx+4)
ff 6/subop/push 0/mod/indirect 2/rm32/edx . . . . . . # push *edx
# . . call
e8/call lookup/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-ints-equal(payload->size, 0xc, msg)
# . . push args
68/push "F - test-copy-array: sets array size in payload"/imm32
68/push 0xc/imm32
ff 6/subop/push 0/mod/indirect 0/rm32/eax . . . . . . # 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-ints-equal(*Next-alloc-id, 0x35, msg)
# . . push args
68/push "F - test-copy-array: increments Next-alloc-id"/imm32
68/push 0x35/imm32
ff 6/subop/push 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 # push *Next-alloc-id
# . . 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-ints-equal(ad->curr - expected-payload, 12 + 4 for alloc-id + 4 for size, msg)
# . . push args
68/push "F - test-copy-array: updates allocation descriptor"/imm32
68/push 0x14/imm32
8b/copy 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # copy *ecx to eax
29/subtract 3/mod/direct 0/rm32/eax . . . 3/r32/ebx . . # subtract ebx from eax
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
# clean up
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 1/imm32 # copy to *Next-alloc-id
# . reclaim locals
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0x20/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
# Fill a region of memory with zeroes.
zero-out: # start: (addr byte), size: int
# pseudocode:
# curr/esi = start
# i/ecx = 0
# while true
# if (i >= size) break
# *curr = 0
# ++curr
# ++i
#
# . 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
52/push-edx
56/push-esi
# curr/esi = start
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi
# var i/ecx: int = 0
31/xor 3/mod/direct 1/rm32/ecx . . . 1/r32/ecx . . # clear ecx
# edx = size
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx
$zero-out:loop:
# if (i >= size) break
39/compare 3/mod/direct 1/rm32/ecx . . . 2/r32/edx . . # compare ecx with edx
7d/jump-if->= $zero-out:end/disp8
# *curr = 0
c6 0/subop/copy-byte 0/mod/direct 6/rm32/esi . . . . . 0/imm8 # copy byte to *esi
# ++curr
46/increment-esi
# ++i
41/increment-ecx
eb/jump $zero-out:loop/disp8
$zero-out:end:
# . restore registers
5e/pop-to-esi
5a/pop-to-edx
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-zero-out:
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# region/ecx = 34, 35, 36, 37
68/push 0x37363534/imm32
89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
# zero-out(ecx, 3)
# . . push args
68/push 3/imm32/size
51/push-ecx
# . . call
e8/call zero-out/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# first 3 bytes cleared, fourth left alone
# . check-ints-equal(*ecx, 0x37000000, msg)
# . . push args
68/push "F - test-zero-out"/imm32
68/push 0x37000000/imm32
ff 6/subop/push 0/mod/indirect 1/rm32/ecx . . . . . . # push *ecx
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
# . reclaim locals
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/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