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|
== code
# Problem: create a function which pushes n zeros on the stack.
# This is not a regular function, so it won't be idiomatic.
# Registers must be properly restored.
# Registers can be spilled, but that modifies the stack and needs to be
# cleaned up.
# This file is kinda like a research notebook, to interactively arrive at the
# solution. Nobody should have to do this without a computer. To run it:
# $ ./translate_subx_debug 000init.linux stack_array.subx && bootstrap/bootstrap --debug --trace --dump run a.elf
# There are multiple versions. You'll need to uncomment exactly one.
# The final version has its own Entry, but the others share this one.
#? Entry:
#? # . prologue
#? 89/<- %ebp 4/r32/esp
#? #
#? 68/push 0xfcfdfeff/imm32
#? b8/copy-to-eax 0x34353637/imm32
#? $dump-stack:
#? (push-n-zero-bytes 0x20)
#? $dump-stack2:
#? 68/push 0x20202020/imm32
#? $dump-stack3:
#? b8/copy-to-eax 1/imm32/exit
#? cd/syscall 0x80/imm8
## 0
#? push-n-zero-bytes: # n: int
#? # . prologue
#? 55/push-ebp
#? 89/<- %ebp 4/r32/esp
#? $push-n-zero-bytes:end:
#? # . epilogue
#? 89/<- %esp 5/r32/ebp
#? 5d/pop-to-ebp
#? c3/return
# stack at dump-stack:
# 0 a: bdffffd0: 00000000 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 fcfdfeff 00000001 bf000000
#
# =>
#
# stack at dump-stack3:
# 0 a: stack:
# 0 a: bdffffd0: 00000000 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 bdfffff8/ebp 090000cc/ra
# 0 a: bdfffff0: 00000004/arg fcfdfeff 00000001 bf000000
## 1
#? push-n-zero-bytes: # n: int
#? # . prologue
#? 55/push-ebp
#? 89/<- %ebp 4/r32/esp
#? # . save registers
#? 50/push-eax
#? $push-n-zero-bytes:end:
#? # . restore registers
#? 58/pop-to-eax
#? # . epilogue
#? 5d/pop-to-ebp
#? c3/return
# stack at dump-stack3:
# 0 a: bdffffd0: 00000000 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 34353637 bdfffff8 090000d1
# 0 a: bdfffff0: 00000004 fcfdfeff 00000001 bf000000
## 2
#? push-n-zero-bytes: # n: int
#? # . prologue
#? 55/push-ebp
#? 89/<- %ebp 4/r32/esp
#? # . save registers
#? 50/push-eax
#? #
#? 8b/-> *(esp+8) 0/r32/eax
#? 2b/subtract *(ebp+8) 4/r32/esp
#? 89/<- *(esp+8) 0/r32/eax
#? $push-n-zero-bytes:end:
#? # . restore registers
#? 58/pop-to-eax
#? # . epilogue
#? 5d/pop-to-ebp
#? c3/return
# stack at dump-stack3:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 00000000
# 0 a: bdffffc0: 00000000 00000000 00000000 090000d1
# 0 a: bdffffd0: 00000000 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 34353637 bdfffff8 090000d1
# 0 a: bdfffff0: 00000020 fcfdfeff 00000001 bf000000
## 3
#? push-n-zero-bytes: # n: int
#? # . prologue
#? 55/push-ebp
#? 89/<- %ebp 4/r32/esp
#? # . save registers
#? # -- esp = ebp
#? 50/push-eax
#? # -- esp+8 = ebp+4
#? 8b/-> *(esp+8) 0/r32/eax
#? 2b/subtract *(ebp+8) 4/r32/esp
#? 89/<- *(esp+8) 0/r32/eax
#? c7 0/subop/copy *(ebp+4) 0/imm32
#? $push-n-zero-bytes:end:
#? # . restore registers
#? 58/pop-to-eax
#? # . epilogue
#? 5d/pop-to-ebp
#? c3/return
# stack at dump-stack3:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 00000000
# 0 a: bdffffc0: 00000000 00000000 00000000 090000d1
# 0 a: bdffffd0: 20202020 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 34353637 bdfffff8 00000000
# 0 a: bdfffff0: 00000020 fcfdfeff 00000001 bf000000
## 4
#? push-n-zero-bytes: # n: int
#? # . prologue
#? 55/push-ebp
#? 89/<- %ebp 4/r32/esp
#? # . save registers
#? # -- esp = ebp
#? 50/push-eax
#? # copy return address over
#? # -- esp+8 = ebp+4
#? 8b/-> *(esp+8) 0/r32/eax
#? 2b/subtract *(ebp+8) 4/r32/esp
#? 89/<- *(esp+8) 0/r32/eax
#? 58/pop-to-eax
#? c7 0/subop/copy *(ebp+8) 0/imm32
#? c7 0/subop/copy *(ebp+4) 0/imm32
#? c7 0/subop/copy *(ebp+0) 0/imm32
#? c7 0/subop/copy *(ebp-4) 0/imm32
#? # . epilogue
#? 5d/pop-to-ebp
#? c3/return
# stack at dump-stack3:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 00000000
# 0 a: bdffffc0: 00000000 00000000 00000000 090000d1
# 0 a: bdffffd0: 20202020 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 fcfdfeff 00000001 bf000000
# Stack looks good now (the 20202020 marks where the array length 0x20 will
# go, and the next 0x20 bytes show the space for the array has been zeroed
# out).
# Final issue: ebp has been clobbered on return.
## 5
# I'd like to translate ebp to esp so we can stop pushing ebp. But we need to
# hold 'n' somewhere, which would require a register, which we then need to
# push.
#? push-n-zero-bytes: # n: int
#? 55/push-ebp
#? 89/<- %ebp 4/r32/esp
#? # -- esp = ebp
#? 50/push-eax
#? $push-n-zero-bytes:bulk-cleaning:
#? $push-n-zero-bytes:copy-ra:
#? # -- esp+8 = ebp+4
#? 8b/-> *(esp+8) 0/r32/eax
#? 2b/subtract *(esp+0xc) 4/r32/esp
#? # -- esp+8+n = ebp+4
#? 89/<- *(esp+8) 0/r32/eax
#? 58/pop-to-eax
#? # -- esp+n = ebp
#? $push-n-zero-bytes:spot-cleaning:
#? c7 0/subop/copy *(ebp+8) 0/imm32
#? c7 0/subop/copy *(ebp+4) 0/imm32
#? c7 0/subop/copy *(ebp+0) 0/imm32
#? c7 0/subop/copy *(ebp-4) 0/imm32
#? 5d/pop-to-ebp
#? c3/return
# stack at dump-stack3:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 00000000
# 0 a: bdffffc0: 00000000 00000000 00000000 090000d1
# 0 a: bdffffd0: 20202020 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 fcfdfeff 00000001 bf000000
# Bah. May be simpler to just create a new segment of global space for this
# function.
## 6
#? push-n-zero-bytes: # n: int
#? 89/<- *Push-n-zero-bytes-ebp 5/r32/ebp # spill ebp without affecting stack
#? 89/<- %ebp 4/r32/esp
#? # -- esp = ebp
#? 50/push-eax
#? $push-n-zero-bytes:bulk-cleaning:
#? $push-n-zero-bytes:copy-ra:
#? # -- esp+8 = ebp+4
#? # -- esp+4 = ebp
#? 8b/-> *(esp+4) 0/r32/eax
#? 2b/subtract *(ebp+4) 4/r32/esp
#? # -- esp+4+n = ebp
#? 89/<- *(esp+4) 0/r32/eax
#? 58/pop-to-eax
#? # -- esp+n = ebp
#? $push-n-zero-bytes:spot-cleaning:
#? c7 0/subop/copy *(ebp+4) 0/imm32
#? c7 0/subop/copy *(ebp+0) 0/imm32
#? c7 0/subop/copy *(ebp-4) 0/imm32
#? c7 0/subop/copy *(ebp-8) 0/imm32
#? 8b/-> *Push-n-zero-bytes-ebp 5/r32/ebp # restore spill
#? c3/return
#?
#? == data
#? Push-n-zero-bytes-ebp: # (addr int)
#? 0/imm32
#? == code
# stack at dump-stack3:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 00000000
# 0 a: bdffffc0: 00000000 00000000 00000000 090000d1
# 0 a: bdffffd0: 20202020 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 fcfdfeff 00000001 bf000000
# Ok, we're there. Now start using zero-out rather than spot-cleaning.
## 7: we need to zero out the return address, but we can't do it inside the function.
## So we'll change the signature slightly.
## Before: clear N bytes and then push N as the array length.
## After: clear N bytes, set *esp to N.
## The helper adds and clears N bytes *before* esp. esp can't be cleared since
## it contains the return address.
#? Entry:
#? # . prologue
#? 89/<- %ebp 4/r32/esp
#? #
#? 68/push 0xfcfdfeff/imm32
#? b8/copy-to-eax 0x34353637/imm32
#? $dump-stack0:
#? (push-n-zero-bytes 0x20)
#? $dump-stack9:
#? c7 0/subop/copy *esp 0x20/imm32
#? $dump-stacka:
#? b8/copy-to-eax 1/imm32/exit
#? cd/syscall 0x80/imm8
#?
#? push-n-zero-bytes: # n: int
#? $push-n-zero-bytes:prologue:
#? 89/<- *Push-n-zero-bytes-ebp 5/r32/ebp # spill ebp without affecting stack
#? 89/<- %ebp 4/r32/esp
#? $push-n-zero-bytes:copy-ra:
#? $dump-stack1:
#? # -- esp = ebp
#? 50/push-eax
#? $dump-stack2:
#? # -- esp+8 = ebp+4
#? # -- esp+4 = ebp
#? 8b/-> *(esp+4) 0/r32/eax
#? $dump-stack3:
#? 2b/subtract *(ebp+4) 4/r32/esp
#? $dump-stack4:
#? # -- esp+4+n = ebp
#? 89/<- *(esp+4) 0/r32/eax
#? $dump-stack5:
#? 58/pop-to-eax
#? # -- esp+n = ebp
#? $push-n-zero-bytes:bulk-cleaning:
#? $dump-stack6:
#? 89/<- *Push-n-zero-bytes-esp 4/r32/esp
#? 81 0/subop/add *Push-n-zero-bytes-esp 4/imm32
#? $dump-stack7:
#? (zero-out *Push-n-zero-bytes-esp *(ebp+4)) # n
#? $push-n-zero-bytes:epilogue:
#? $dump-stack8:
#? 8b/-> *Push-n-zero-bytes-ebp 5/r32/ebp # restore spill
#? c3/return
#?
#? zero-out: # start: (addr byte), len: int
#? # pseudocode:
#? # curr/esi = start
#? # i/ecx = 0
#? # while true
#? # if (i >= len) 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 = len
#? 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx
#? $zero-out:loop:
#? # if (i >= len) 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 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
#?
#? == data
#? Push-n-zero-bytes-ebp: # (addr int)
#? 0/imm32
#? Push-n-zero-bytes-esp: # (addr int)
#? 0/imm32
#? == code
# stack at dump-stack0:
# 0 a: bdffffb0: 00000000 00000000 00000000 00000000
# 0 a: bdffffc0: 00000000 00000000 00000000 00000000
# 0 a: bdffffd0: 00000000 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 [fcfdfeff] 00000001 bf000000
# desired state after push-n-zero-bytes:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 bdffffec
# 0 a: bdffffc0: 0900012a bdffffd0 00000020 090000d1
# 0 a: bdffffd0: [rrrrrrrr] 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 fcfdfeff 00000001 bf000000
# Stack pointer contains ra is caller's responsibility to over-write with array length.
# actual state:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 bdffffec
# 0 a: bdffffc0: 0900012a bdffffd0 00000020 090000d1
# 0 a: bdffffd0: 00000000 [00000000] 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000020 fcfdfeff 00000001 bf000000
# Couple of issues. But where does the return address disappear to?
## 8:
#? Entry:
#? # . prologue
#? 89/<- %ebp 4/r32/esp
#? #
#? 68/push 0xfcfdfeff/imm32
#? b8/copy-to-eax 0x34353637/imm32
#? $dump-stack0:
#? (push-n-zero-bytes 0x20)
#? $dump-stack9:
#? 68/push 0x20/imm32
#? #? c7 0/subop/copy *esp 0x20/imm32
#? $dump-stacka:
#? b8/copy-to-eax 1/imm32/exit
#? cd/syscall 0x80/imm8
#?
#? push-n-zero-bytes: # n: int
#? $push-n-zero-bytes:prologue:
#? 89/<- *Push-n-zero-bytes-ebp 5/r32/ebp # spill ebp without affecting stack
#? 89/<- %ebp 4/r32/esp
#? $push-n-zero-bytes:copy-ra:
#? $dump-stack1:
#? # -- esp = ebp
#? 50/push-eax
#? $dump-stack2:
#? # -- esp+8 = ebp+4
#? # -- esp+4 = ebp
#? 8b/-> *(esp+4) 0/r32/eax
#? $dump-stack3:
#? 2b/subtract *(ebp+4) 4/r32/esp
#? $dump-stack4:
#? # -- esp+4+n = ebp
#? 89/<- *(esp+4) 0/r32/eax
#? $dump-stack5:
#? 58/pop-to-eax
#? # -- esp+n = ebp
#? $push-n-zero-bytes:bulk-cleaning:
#? $dump-stack6:
#? 89/<- *Push-n-zero-bytes-esp 4/r32/esp
#? 81 0/subop/add *Push-n-zero-bytes-esp 4/imm32
#? $dump-stack7:
#? (zero-out *Push-n-zero-bytes-esp *(ebp+4)) # n
#? $push-n-zero-bytes:epilogue:
#? $dump-stack8:
#? 8b/-> *Push-n-zero-bytes-ebp 5/r32/ebp # restore spill
#? c3/return
#?
#? zero-out: # start: (addr byte), len: int
#? # pseudocode:
#? # curr/esi = start
#? # i/ecx = 0
#? # while true
#? # if (i >= len) 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 = len
#? 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx
#? $zero-out:loop:
#? # if (i >= len) 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 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
#?
#? == data
#? Push-n-zero-bytes-ebp: # (addr int)
#? 0/imm32
#? Push-n-zero-bytes-esp: # (addr int)
#? 0/imm32
#? == code
# stack at dump-stack0:
# 0 a: bdffffb0: 00000000 00000000 00000000 00000000
# 0 a: bdffffc0: 00000000 00000000 00000000 00000000
# 0 a: bdffffd0: 00000000 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 [fcfdfeff] 00000001 bf000000
# desired state after push-n-zero-bytes:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 bdffffec
# 0 a: bdffffc0: 0900012a bdffffd0 00000020 090000d1
# 0 a: bdffffd0: [rrrrrrrr] 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 fcfdfeff 00000001 bf000000
# actual state:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 bdffffec
# 0 a: bdffffc0: 09000124 bdffffd0 00000020 090000d1
# 0 a: bdffffd0: [00000000] 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000020 fcfdfeff 00000001 bf000000
# Ok, just one diff, at bdfffff0
## 9:
Entry:
# . prologue
89/<- %ebp 4/r32/esp
#
68/push 0xfcfdfeff/imm32
b8/copy-to-eax 0x34353637/imm32
$dump-stack0:
(push-n-zero-bytes 0x20)
$dump-stack9:
68/push 0x20/imm32
$dump-stacka:
b8/copy-to-eax 1/imm32/exit
cd/syscall 0x80/imm8
push-n-zero-bytes: # n: int
$push-n-zero-bytes:prologue:
89/<- *Push-n-zero-bytes-ebp 5/r32/ebp # spill ebp without affecting stack
89/<- %ebp 4/r32/esp
$push-n-zero-bytes:copy-ra:
$dump-stack1:
# -- esp = ebp
50/push-eax
$dump-stack2:
# -- esp+8 = ebp+4
# -- esp+4 = ebp
8b/-> *(esp+4) 0/r32/eax
$dump-stack3:
2b/subtract *(ebp+4) 4/r32/esp
$dump-stack4:
# -- esp+4+n = ebp
89/<- *(esp+4) 0/r32/eax
$dump-stack5:
58/pop-to-eax
# -- esp+n = ebp
$push-n-zero-bytes:bulk-cleaning:
$dump-stack6:
89/<- *Push-n-zero-bytes-esp 4/r32/esp
81 0/subop/add *Push-n-zero-bytes-esp 4/imm32
$dump-stack7:
81 0/subop/add *(ebp+4) 4/imm32
(zero-out *Push-n-zero-bytes-esp *(ebp+4)) # n
$push-n-zero-bytes:epilogue:
$dump-stack8:
8b/-> *Push-n-zero-bytes-ebp 5/r32/ebp # restore spill
c3/return
zero-out: # start: (addr byte), len: int
# pseudocode:
# curr/esi = start
# i/ecx = 0
# while true
# if (i >= len) 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 = len
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx
$zero-out:loop:
# if (i >= len) 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 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
== data
Push-n-zero-bytes-ebp: # (addr int)
0/imm32
Push-n-zero-bytes-esp: # (addr int)
0/imm32
== code
# stack at dump-stack0:
# 0 a: bdffffb0: 00000000 00000000 00000000 00000000
# 0 a: bdffffc0: 00000000 00000000 00000000 00000000
# 0 a: bdffffd0: 00000000 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 [fcfdfeff] 00000001 bf000000
# desired state after push-n-zero-bytes:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 bdffffec
# 0 a: bdffffc0: 0900012a bdffffd0 00000020 090000d1
# 0 a: bdffffd0: [xxxxxxxx] 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 fcfdfeff 00000001 bf000000
# actual state:
# 0 a: bdffff90: 00000000 00000000 00000000 00000000
# 0 a: bdffffa0: 00000000 00000000 00000000 00000000
# 0 a: bdffffb0: 00000000 00000000 00000000 bdffffec
# 0 a: bdffffc0: 0900012f bdffffd0 00000024 090000d1
# 0 a: bdffffd0: [00000000] 00000000 00000000 00000000
# 0 a: bdffffe0: 00000000 00000000 00000000 00000000
# 0 a: bdfffff0: 00000000 fcfdfeff 00000001 bf000000
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