160 lines
7.7 KiB
Plaintext
160 lines
7.7 KiB
Plaintext
# write: like _write, but also support in-memory streams in addition to file
|
|
# descriptors.
|
|
#
|
|
# Our first dependency-injected and testable primitive. We can pass it either
|
|
# a file descriptor or an address to a stream. If a file descriptor is passed
|
|
# in, we _write to it using the right syscall. If a 'fake file descriptor' or
|
|
# stream is passed in, we append to the stream. This lets us redirect output
|
|
# in tests and check it later.
|
|
#
|
|
# We assume our data segment will never begin at an address shorter than
|
|
# 0x08000000, so any smaller arguments are assumed to be real file descriptors.
|
|
#
|
|
# A stream looks like this:
|
|
# read: int # index at which to read next
|
|
# write: int # index at which writes go
|
|
# data: (array byte) # prefixed by length as usual
|
|
|
|
== 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
|
|
|
|
# TODO: come up with a way to signal when a write to disk fails
|
|
write: # f : fd or (address stream), s : (address array byte) -> <void>
|
|
# . prolog
|
|
55/push-EBP
|
|
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
|
|
# if (f < 0x08000000) _write(f, s) and return # f can't be a user-mode address, so treat it as a kernel file descriptor
|
|
81 7/subop/compare 1/mod/*+disp8 5/rm32/EBP . . . . 8/disp8 0x08000000/imm32 # compare *(EBP+8)
|
|
73/jump-if-greater-unsigned-or-equal $write:fake/disp8
|
|
# . . push args
|
|
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 _write/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
|
|
eb/jump $write:end/disp8
|
|
$write:fake:
|
|
# otherwise, treat 'f' as a stream to append to
|
|
# . save registers
|
|
50/push-EAX
|
|
51/push-ECX
|
|
52/push-EDX
|
|
53/push-EBX
|
|
# ECX = f
|
|
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 1/r32/ECX 8/disp8 . # copy *(EBP+8) to ECX
|
|
# EDX = f->write
|
|
8b/copy 0/mod/indirect 1/rm32/ECX . . . 2/r32/EDX . . # copy *ECX to EDX
|
|
# EBX = f->length
|
|
8b/copy 1/mod/*+disp8 1/rm32/ECX . . . 3/r32/EBX 8/disp8 . # copy *(ECX+8) to EBX
|
|
# EAX = _append-3(&f->data[f->write], &f->data[f->length], s)
|
|
# . . push s
|
|
ff 6/subop/push 1/mod/*+disp8 5/rm32/EBP . . . . 0xc/disp8 . # push *(EBP+12)
|
|
# . . push &f->data[f->length]
|
|
8d/copy-address 1/mod/*+disp8 4/rm32/sib 1/base/ECX 3/index/EBX . 3/r32/EBX 0xc/disp8 . # copy ECX+EBX+12 to EBX
|
|
53/push-EBX
|
|
# . . push &f->data[f->write]
|
|
8d/copy-address 1/mod/*+disp8 4/rm32/sib 1/base/ECX 2/index/EDX . 3/r32/EBX 0xc/disp8 . # copy ECX+EDX+12 to EBX
|
|
53/push-EBX
|
|
# . . call
|
|
e8/call _append-3/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
|
|
# f->write += EAX
|
|
01/add 0/mod/indirect 1/rm32/ECX . . . 0/r32/EAX . . # add EAX to *ECX
|
|
# . restore registers
|
|
5b/pop-to-EBX
|
|
5a/pop-to-EDX
|
|
59/pop-to-ECX
|
|
58/pop-to-EAX
|
|
$write:end:
|
|
# . epilog
|
|
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
|
|
5d/pop-to-EBP
|
|
c3/return
|
|
|
|
test-write-single:
|
|
# clear-stream(_test-stream)
|
|
# . . push args
|
|
68/push _test-stream/imm32
|
|
# . . call
|
|
e8/call clear-stream/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
|
|
# write(_test-stream, "Ab")
|
|
# . . push args
|
|
68/push "Ab"/imm32
|
|
68/push _test-stream/imm32
|
|
# . . call
|
|
e8/call write/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
|
|
# check-ints-equal(*_test-stream->data, 41/A 62/b 00 00, msg)
|
|
# . . push args
|
|
68/push "F - test-write-single"/imm32
|
|
68/push 0x006241/imm32/Ab
|
|
# . . push *_test-stream->data
|
|
b8/copy-to-EAX _test-stream/imm32
|
|
ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX . . . . 0xc/disp8 . # push *(EAX+12)
|
|
# . . call
|
|
e8/call check-ints-equal/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
|
|
# end
|
|
c3/return
|
|
|
|
test-write-appends:
|
|
# clear-stream(_test-stream)
|
|
# . . push args
|
|
68/push _test-stream/imm32
|
|
# . . call
|
|
e8/call clear-stream/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
|
|
# write(_test-stream, "C")
|
|
# . . push args
|
|
68/push "C"/imm32
|
|
68/push _test-stream/imm32
|
|
# . . call
|
|
e8/call write/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
|
|
# write(_test-stream, "D")
|
|
# . . push args
|
|
68/push "D"/imm32
|
|
68/push _test-stream/imm32
|
|
# . . call
|
|
e8/call write/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
|
|
# check-ints-equal(*_test-stream->data, 43/C 44/D 00 00, msg)
|
|
# . . push args
|
|
68/push "F - test-write-appends"/imm32
|
|
68/push 0x00004443/imm32/C-D
|
|
# . . push *_test-stream->data
|
|
b8/copy-to-EAX _test-stream/imm32
|
|
ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX . . . . 0xc/disp8 . # push *(EAX+12)
|
|
# . . call
|
|
e8/call check-ints-equal/disp32
|
|
# . . discard args
|
|
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
|
|
# end
|
|
c3/return
|
|
|
|
== data
|
|
|
|
_test-stream:
|
|
# current write index
|
|
0/imm32
|
|
# current read index
|
|
0/imm32
|
|
# length
|
|
0x10/imm32
|
|
# data (2 lines x 8 bytes/line)
|
|
00 00 00 00 00 00 00 00
|
|
00 00 00 00 00 00 00 00
|
|
|
|
# . . vim:nowrap:textwidth=0
|