429 lines
23 KiB
Plaintext
429 lines
23 KiB
Plaintext
# A sketch of Mu-style handles or kinda-safe pointers, that add a modicum of
|
|
# checking to dynamically allocated memory.
|
|
#
|
|
# This approach avoids using 'allocate' directly in favor of two primitives:
|
|
# - 'new', which allocates some space (the 'payload'), stores the address
|
|
# along with an opaque 'alloc id' in a 'handle', and prepends the same
|
|
# alloc id to the payload.
|
|
# - 'lookup', which checks that the alloc id at the start of a handle matches
|
|
# the alloc id at the start of the payload before returning the address.
|
|
#
|
|
# Layout of a handle:
|
|
# offset 0: alloc id
|
|
# offset 4: address
|
|
#
|
|
# To run:
|
|
# $ ./subx translate init.linux 0*.subx apps/handle.subx -o apps/handle
|
|
# $ ./subx run apps/handle
|
|
# Expected result is a successful lookup followed by a hard abort:
|
|
# lookup succeeded
|
|
# lookup failed
|
|
# (This file is a prototype. The 'tests' in it aren't real; failures are
|
|
# expected.)
|
|
|
|
== 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
|
|
|
|
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-'.
|
|
$handle-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
|
|
b8/copy-to-eax 1/imm32/exit
|
|
cd/syscall 0x80/imm8
|
|
|
|
new: # ad : (addr allocation-descriptor), n : int, out : (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+4
|
|
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 1/r32/ecx 0xc/disp8 . # copy *(ebp+12) to ecx
|
|
81 0/subop/add 3/mod/direct 1/rm32/ecx . . . . . 4/imm32 # add to ecx
|
|
# var eax : (handle _) = allocate(ad, ecx)
|
|
# . . push args
|
|
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 . . . . . 8/imm32 # add to esp
|
|
# edx = out
|
|
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0x10/disp8 . # copy *(ebp+16) to edx
|
|
# out->address = eax
|
|
89/copy 1/mod/*+disp8 2/rm32/edx . . . 0/r32/eax 4/disp8 . # copy eax to *(edx+4)
|
|
# if (eax == 0) out->alloc_id = 0, return
|
|
3d/compare-eax-and 0/imm32
|
|
75/jump-if-not-equal $new:continue/disp8
|
|
c7 0/subop/copy 0/mod/indirect 2/rm32/edx . . . . . 0/imm32 # copy to *edx
|
|
eb/jump $new:end/disp8
|
|
$new:continue:
|
|
# otherwise:
|
|
# ecx = *Next-alloc-id
|
|
8b/copy 0/mod/indirect 5/rm32/.disp32 . . 1/r32/ecx Next-alloc-id/disp32 # copy *Next-alloc-id to ecx
|
|
# *eax = *Next-alloc-id/ecx
|
|
89/copy 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # copy ecx to *eax
|
|
# out->alloc_id = *Next-alloc-id
|
|
89/copy 0/mod/indirect 2/rm32/edx . . . 1/r32/ecx . . # copy ecx to *edx
|
|
# increment *Next-alloc-id
|
|
ff 0/subop/increment 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 # increment *Next-alloc-id
|
|
$new: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-new:
|
|
# . prologue
|
|
55/push-ebp
|
|
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
|
|
# var heap/edx : allocation-descriptor
|
|
68/push 0/imm32/limit
|
|
68/push 0/imm32/curr
|
|
89/copy 3/mod/direct 2/rm32/edx . . . 4/r32/esp . . # copy esp to edx
|
|
# heap = new-segment(512)
|
|
# . . push args
|
|
52/push-edx
|
|
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
|
|
# *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
|
|
# 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
|
|
# new(heap, 2, handle/ecx)
|
|
# . . push args
|
|
51/push-ecx
|
|
68/push 2/imm32/size
|
|
52/push-edx
|
|
# . . call
|
|
e8/call new/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
|
|
# check-ints-equal(handle->alloc_id, 0x34, msg)
|
|
# . . push args
|
|
68/push "F - test-new: alloc id of handle"/imm32
|
|
68/push 0x34/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
|
|
# check-ints-equal(*handle->address, 0x34, msg)
|
|
# . . push args
|
|
68/push "F - test-new: alloc id of payload"/imm32
|
|
68/push 0x34/imm32
|
|
8b/copy 1/mod/*+disp8 1/rm32/ecx . . . 2/r32/edx 4/disp8 . # copy *(ecx+4) to edx
|
|
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(*Next-alloc-id, 0x35)
|
|
# . . push args
|
|
68/push "F - test-new: next alloc id"/imm32
|
|
68/push 0x35/imm32
|
|
ff 6/subop/push 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 # copy to *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
|
|
# clean up
|
|
# . *Next-alloc-id = 1
|
|
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 1/imm32 # copy to *Next-alloc-id
|
|
# . epilogue
|
|
89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
|
|
5d/pop-to-ebp
|
|
c3/return
|
|
|
|
_pending-test-new-failure:
|
|
# . prologue
|
|
55/push-ebp
|
|
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
|
|
# . *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
|
|
# define an allocation-descriptor with no space left
|
|
# . var ad/eax : allocation-descriptor = {0x10, 0x10}
|
|
68/push 0x10/imm32/limit
|
|
68/push 0x10/imm32/curr
|
|
89/copy 3/mod/direct 0/rm32/eax . . . 4/r32/esp . . # copy esp to eax
|
|
# . var handle/ecx = {random, random}
|
|
68/push 1234/imm32/address
|
|
68/push 5678/imm32/alloc-id
|
|
89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx
|
|
# try to allocate
|
|
# . new(ad, 2, handle/ecx)
|
|
# . . push args
|
|
51/push-ecx
|
|
68/push 2/imm32/size
|
|
50/push-eax
|
|
# . . call
|
|
e8/call new/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
|
|
# handle should be cleared
|
|
# . check-ints-equal(handle->alloc_id, 0, msg)
|
|
# . . push args
|
|
68/push "F - test-new-failure: alloc id of handle"/imm32
|
|
68/push 0/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
|
|
# . check-ints-equal(handle->address, 0, msg)
|
|
# . . push args
|
|
68/push "F - test-new-failure: address of handle"/imm32
|
|
68/push 0/imm32
|
|
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
|
|
# Next-alloc-id should be unmodified
|
|
# . check-ints-equal(*Next-alloc-id, 0x34)
|
|
# . . push args
|
|
68/push "F - test-new-failure: next alloc id"/imm32
|
|
68/push 0x34/imm32
|
|
ff 6/subop/push 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 # copy to *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
|
|
# clean up
|
|
# . *Next-alloc-id = 1
|
|
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 1/imm32 # copy to *Next-alloc-id
|
|
# . 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) -> eax : (addr T)
|
|
# . prologue
|
|
55/push-ebp
|
|
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
|
|
# - as a proof of concept for future inlining, uses no general-purpose registers besides the output (eax)
|
|
# eax = handle
|
|
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 8/disp8 . # copy *(ebp+8) to eax
|
|
# - inline {
|
|
# push handle->alloc_id
|
|
ff 6/subop/push 0/mod/indirect 0/rm32/eax . . . . . . # push *eax
|
|
# eax = handle->address (payload)
|
|
8b/copy 1/mod/*+disp8 0/rm32/eax . . . . 4/disp8 . # copy *(eax+4) to eax
|
|
# push handle->address
|
|
50/push-eax
|
|
# eax = payload->alloc_id
|
|
8b/copy 0/mod/indirect 0/rm32/eax . . . . . . # copy *eax to eax
|
|
# if (eax != handle->alloc_id) abort
|
|
39/compare 1/mod/*+disp8 4/rm32/sib 4/base/esp 4/index/none . 0/r32/eax 4/disp8 . # compare *(esp+4) and eax
|
|
75/jump-if-not-equal $lookup:abort/disp8
|
|
# eax = pop handle->address
|
|
58/pop-to-eax
|
|
# discard handle->alloc_id
|
|
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
|
|
# add 4
|
|
05/add-to-eax 4/imm32
|
|
# - }
|
|
# - alternative consuming a second register {
|
|
#? # ecx = handle->alloc_id
|
|
#? 8b/copy 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # copy *eax to ecx
|
|
#? # eax = handle->address (payload)
|
|
#? 8b/copy 1/mod/*+disp8 0/rm32/eax . . . 0/r32/eax 4/disp8 . # copy *(eax+4) to eax
|
|
#? # if (ecx != *eax) abort
|
|
#? 39/compare 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # compare *eax and ecx
|
|
#? 75/jump-if-not-equal $lookup:abort/disp8
|
|
#? # add 4 to eax
|
|
#? 05/add-to-eax 4/imm32
|
|
# - }
|
|
# . 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
|
|
b8/copy-to-eax 1/imm32/exit
|
|
cd/syscall 0x80/imm8
|
|
|
|
test-lookup-success:
|
|
# . prologue
|
|
55/push-ebp
|
|
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
|
|
# . save registers
|
|
# var heap/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
|
|
# heap = 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 = heap->curr
|
|
8b/copy 0/mod/indirect 3/rm32/ebx . . . 2/r32/edx . . # copy *ebx to edx
|
|
# new(heap, 2, handle)
|
|
# . . push args
|
|
51/push-ecx
|
|
68/push 2/imm32/size
|
|
53/push-ebx
|
|
# . . call
|
|
e8/call new/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
|
|
# eax = lookup(handle)
|
|
# . . push args
|
|
51/push-ecx
|
|
# . . call
|
|
e8/call lookup/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/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
|
|
# . *Next-alloc-id = 1
|
|
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 1/imm32 # copy to *Next-alloc-id
|
|
# write(2/stderr, "lookup succeeded\n")
|
|
# . . push args
|
|
68/push "lookup succeeded\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
|
|
# . restore registers
|
|
5a/pop-to-edx
|
|
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
|
|
|
|
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
|
|
# . new(heap, 2, h1)
|
|
# . . push args
|
|
51/push-ecx
|
|
68/push 2/imm32/size
|
|
56/push-esi
|
|
# . . call
|
|
e8/call new/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
|
|
# . new(heap, 2, h2)
|
|
# . . push args
|
|
52/push-edx
|
|
68/push 2/imm32/size
|
|
56/push-esi
|
|
# . . call
|
|
e8/call new/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
|
|
51/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 . . . . . 4/imm32 # add to esp
|
|
# clean up
|
|
# . *Next-alloc-id = 1
|
|
c7 0/subop/copy 0/mod/indirect 5/rm32/.disp32 . . . Next-alloc-id/disp32 1/imm32 # copy to *Next-alloc-id
|
|
# . epilogue
|
|
89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
|
|
5d/pop-to-ebp
|
|
c3/return
|
|
|
|
== data
|
|
|
|
# Monotonically increasing counter for calls to 'new'
|
|
Next-alloc-id: # int
|
|
1/imm32
|
|
|
|
# . . vim:nowrap:textwidth=0
|