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# primitives for emitting traces to a trace stream, and for tests to check the trace stream
#
# A trace stream looks like this:
# read : int # index that we've read until
# write : int # index at which writes go
# data : (array byte) # prefixed by length as usual
# In a real trace the data will be in a special segment set aside for the purpose.
#
# primitives for operating on traces:
# - initialize-trace-stream (update global variable)
# - trace: stream, string
# - die: stream (exit(1) if using real trace)
# - check-trace-contains: stream, string/line, string/message (scans only from stream's read pointer, prints message to stderr on failure, updates stream's read pointer)
# - rewind-reads: stream (resets read pointer)
# - scan-to-next-line: stream (advance read pointer past next newline)
#
# Traces are very fundamental, so many of the helpers we create here won't be
# used elsewhere; we'll switch to more bounds-checked variants. But here we get
# bounds-checking for free; we allocate a completely disjoint segment for trace
# data, and overflowing it will generate a page fault.
== data
# We'll save the address of the trace segment here.
Trace-stream:
00 00 00 00
# Fake trace-stream for tests.
# Also illustrates the layout of the real trace-stream (segment).
_test-trace-stream:
# current write index
00 00 00 00
# current read index
00 00 00 00
# length (= 8)
08 00 00 00
# data
00 00 00 00 00 00 00 00 # 8 bytes
== code
# instruction effective address operand 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
# main:
e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
# 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
cd/syscall 0x80/imm8
# Allocate a new segment for the trace stream, initialize its length, and save its address to Trace-stream.
# The Trace-stream segment will consist of variable-length lines separated by newlines (0x0a)
initialize-trace-stream:
# EAX = new-segment(0x1000)
# push args
68/push 0x1000/imm32/N
# call
e8/call new-segment/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# copy EAX to *Trace-stream
89/copy 0/mod/indirect 5/rm32/.disp32 . . 0/r32/EAX Trace-stream/disp32 # copy EAX to *Trace-stream
# Trace-stream.length = 0x1000/N - 12
c7 0/copy 1/mod/*+disp8 0/rm32/EAX . . . . 8/disp8 0xff4/imm32 # copy 0xff4 to *(EAX+8)
c3/return
# Append a string to the given trace stream.
# Silently give up if it's already full. Or truncate the string if there isn't enough room.
trace: # t : (address trace-stream), line : string
# prolog
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
# EDI = t
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none 7/r32/EDI 8/disp8 . # copy *(EBP+8) to EDI
# ESI = line
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none 6/r32/ESI 0xc/disp8 . # copy *(EBP+12) to ESI
# ECX = t->write
8b/copy 0/mod/indirect 7/rm32/EDI . . . 1/r32/ECX . . # copy *EDI to ECX
# EDX = t->length
8b/copy 1/mod/*+disp8 7/rm32/EDI . . . 2/r32/EDX 8/disp8 . # copy *(EDI+8) to EDX
# EAX = _append-3(&t->data[t->write], &t->data[t->length], line)
# push line
56/push-ESI
# push &t->data[t->length]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 2/index/EDX . 3/r32/EBX 0xc/disp8 . # copy EDI+EDX+12 to EBX
53/push-EBX
# push &t->data[t->write]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 1/index/ECX . 3/r32/EBX 0xc/disp8 . # copy EDI+ECX+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
# if EAX == 0 return
81 7/subop/compare 3/mod/direct 0/rm32/EAX . . . . . 0/imm32 # compare EDX
74/jump-if-equal $trace:end/disp8
# t->write += EAX
01/add 0/mod/indirect 7/rm32/EDI . . . 0/r32/EAX . . # add EAX to *EDI
# refresh ECX = t->write
8b/copy 0/mod/indirect 7/rm32/EDI . . . 1/r32/ECX . . # copy *EDI to ECX
# EAX = _append-3(&t->data[t->write], &t->data[t->length], line)
# push line
68/push Newline/imm32
# push &t->data[t->length]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 2/index/EDX . 3/r32/EBX 0xc/disp8 . # copy EDI+EDX+12 to EBX
53/push-EBX
# push &t->data[t->write]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 1/index/ECX . 3/r32/EBX 0xc/disp8 . # copy EDI+ECX+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
# t->write += EAX
01/add 0/mod/indirect 7/rm32/EDI . . . 0/r32/EAX . . # add EAX to *EDI
$trace: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
# epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
clear-trace-stream: # t : (address trace-stream)
# prolog
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 = t
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none 0/r32/EAX 8/disp8 . # copy *(EBP+8) to EAX
# ECX = t->length
8b/copy 1/mod/*+disp8 0/rm32/EAX . . . 1/r32/ECX 8/disp8 . # copy *(EAX+8) to ECX
# ECX = &t->data[t->length]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/EAX 1/index/ECX . 1/r32/ECX 0xc/disp8 . # copy EAX+ECX+12 to ECX
# t->write = 0
c7/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm32 # copy to *EAX
# t->read = 0
c7/copy 1/mod/*+disp8 0/rm32/EAX . . . . 4/disp8 0/imm32 # copy to *(EAX+4)
# EAX = t->data
81 0/subop/add 3/mod/direct 0/rm32/EAX . . . . . 0xc/imm32 # add to EAX
# while (true)
$clear-trace-stream:loop:
# if EAX >= ECX break
39/compare 3/mod/direct 0/rm32/EAX . . . 1/r32/ECX . . # compare EAX with ECX
7d/jump-if-greater-or-equal $clear-trace-stream:end/disp8
# *EAX = 0
c7/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm32 # copy to *EAX
# EAX += 4
81 0/subop/add 3/mod/direct 0/rm32/EAX . . . . . 4/imm32 # add to EAX
eb/jump $clear-trace-stream:loop/disp8
$clear-trace-stream:end:
# restore registers
59/pop-to-ECX
58/pop-to-EAX
# epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
## tests
test-trace-single:
# clear-trace-stream(_test-trace-stream)
# push args
68/push _test-trace-stream/imm32
# call
e8/call clear-trace-stream/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# trace(_test-trace-stream, "Ab")
# push args
68/push "Ab"/imm32
68/push _test-trace-stream/imm32
# call
e8/call trace/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# check-ints-equal(*_test-trace-stream.data, 41/A 62/b 0a/newline 00, msg)
# push args
68/push "F - test-trace-single"/imm32
68/push 0x0a6241/imm32/Ab-newline
# push *_test-trace-stream.data
b8/copy-to-EAX _test-trace-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-trace-appends:
# clear-trace-stream(_test-trace-stream)
# push args
68/push _test-trace-stream/imm32
# call
e8/call clear-trace-stream/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# trace(_test-trace-stream, "C")
# push args
68/push "C"/imm32
68/push _test-trace-stream/imm32
# call
e8/call trace/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# trace(_test-trace-stream, "D")
# push args
68/push "D"/imm32
68/push _test-trace-stream/imm32
# call
e8/call trace/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# check-ints-equal(*_test-trace-stream.data, 43/C 0a/newline 44/D 0a/newline, msg)
# push args
68/push "F - test-trace-appends"/imm32
68/push 0x0a440a43/imm32/C-newline-D-newline
# push *_test-trace-stream.data
b8/copy-to-EAX _test-trace-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-trace-empty-line:
# clear-trace-stream(_test-trace-stream)
# push args
68/push _test-trace-stream/imm32
# call
e8/call clear-trace-stream/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# trace(_test-trace-stream, "")
# push args
68/push ""/imm32
68/push _test-trace-stream/imm32
# call
e8/call trace/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# check-ints-equal(*_test-trace-stream.data, 0, msg)
# push args
68/push "F - test-trace-empty-line"/imm32
68/push 0/imm32
# push *_test-trace-stream.data
b8/copy-to-EAX _test-trace-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
## helpers
# 3-argument variant of _append
_append-3: # out : address, outend : address, s : (array byte) -> num_bytes_appended/EAX
# prolog
55/push-EBP
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
# save registers
51/push-ECX
# _append-4(out, outend, &s.data[0], &s.data[s.length]) -> num_bytes_appended/EAX
# push &s.data[s.length]
# EAX = s
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none 0/r32/EAX 0x10/disp8 . # copy *(EBP+16) to EAX
# ECX = s.length
8b/copy 0/mod/indirect 0/rm32/EAX . . . 1/r32/ECX . . # copy *EAX to ECX
# ECX = &s.data[s.length]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/EAX 1/index/ECX . 1/r32/ECX 4/disp8 . # copy EAX+ECX+4 to ECX
51/push-ECX
# push &s.data[0]
8d/copy-address 1/mod/*+disp8 0/rm32/EAX . . . 1/r32/ECX 4/disp8 . # copy EAX+4 to ECX
51/push-ECX
# push outend
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 0xc/disp8 . # push *(EBP+12)
# push out
ff 6/subop/push 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . . 0x8/disp8 . # push *(EBP+8)
# call
e8/call _append-4/disp32
# discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0x10/imm32 # add to ESP
# restore registers
59/pop-to-ECX
# epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
# 4-argument variant of _append
_append-4: # out : address, outend : address, in : address, inend : address -> num_bytes_appended/EAX
# prolog
55/push-EBP
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
# save registers
51/push-ECX
52/push-EDX
53/push-EBX
56/push-ESI
57/push-EDI
# EAX/num_bytes_appended = 0
b8/copy-to-EAX 0/imm32
# EDI = out
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 7/r32/EDI 0x8/disp8 . # copy *(EBP+8) to EDI
# EDX = outend
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 2/r32/EDX 0xc/disp8 . # copy *(EBP+12) to EDX
# ESI = in
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 6/r32/ESI 0x10/disp8 . # copy *(EBP+16) to ESI
# ECX = inend
8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 1/r32/ECX 0x14/disp8 . # copy *(EBP+20) to ECX
$_append-4:loop:
# if ESI/src >= ECX/srcend break
39/compare 3/mod/direct 6/rm32/ESI . . . 1/r32/ECX . . # compare ESI with ECX
7d/jump-if-greater-or-equal $_append-4:end/disp8
# if EDI/out >= EDX/outend break (for now silently ignore filled up buffer)
39/compare 3/mod/direct 7/rm32/EDI . . . 2/r32/EDX . . # compare EDI with EDX
7d/jump-if-greater-or-equal $_append-4:end/disp8
# copy one byte from ESI/src to EDI/out
8a/copy-byte 0/mod/indirect 6/rm32/ESI . . . 3/r32/BL . . # copy byte at *ESI to BL
88/copy-byte 0/mod/indirect 7/rm32/EDI . . . 3/r32/BL . . # copy byte at BL to *EDI
# updates
40/increment-EAX
46/increment-ESI
47/increment-EDI
eb/jump $_append-4:loop/disp8
$_append-4:end:
# restore registers
5f/pop-to-EDI
5e/pop-to-ESI
5b/pop-to-EBX
5a/pop-to-EDX
59/pop-to-ECX
# epilog
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
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