1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
|
#! /your/favourite/path/to/ruby
# -*- Ruby -*-
# -*- frozen_string_literal: true; -*-
# -*- warn_indent: true; -*-
#
# Copyright (c) 2020 Wu, Alan. All rights reserved.
#
# This file is a part of the programming language Ruby. Permission is hereby
# granted, to either redistribute and/or modify this file, provided that the
# conditions mentioned in the file COPYING are met. Consult the file for
# details.
module RubyVM::MicroJIT
ScrapeResult = Struct.new(:pre_call_bytes, :post_call_bytes, :disassembly_lines)
class << self
def target_platform
# Note, checking RUBY_PLATRFORM doesn't work when cross compiling
@platform ||= if RUBY_PLATFORM.include?('darwin')
:darwin
elsif RUBY_PLATFORM.include?('linux')
:linux
else
:unknown
end
end
def get_fileoff
# use the load command to figure out the offset to the start of the content of vm.o
`otool -l vm.o`.each_line do |line|
if (fileoff = line[/fileoff (\d+)/, 1])
p [__method__, line] if $DEBUG
return fileoff.to_i
end
end
raise
end
def get_symbol_offset(symbol)
`nm vm.o`.each_line do |line|
if (offset = line[Regexp.compile('(\h+).+' + Regexp.escape(symbol) + '\Z'), 1])
p [__method__, line] if $DEBUG
return Integer(offset, 16)
end
end
raise
end
def readint8b(offset)
bytes = IO.binread('vm.o', 8, offset)
bytes.unpack('q').first # this is native endian but we want little endian. it's fine if the host moachine is x86
end
def get_symbol_section_and_offset(name)
`objdump -w -t vm.o`.each_line do |line|
split_line = line.split
next unless split_line.size >= 6
# the table should go into a data section
if split_line[5].include?('insns_address_table') && split_line[3].include?('data')
p line if $DEBUG
return [split_line[3], Integer(split_line[0], 16)]
end
end
raise 'Failed to find section and offset for the instruction address table'
end
def get_handler_offset(table_section, table_offset, insn_id)
target_offset = insn_id * 8 + table_offset
reloc_start_message = "RELOCATION RECORDS FOR [#{table_section}]:"
`objdump -w -r vm.o`.each_line do |line|
line.strip!
if (line == reloc_start_message)...(line.empty?)
split_line = line.split
next if split_line.first == 'RELOCATION'
next if split_line == ['OFFSET', 'TYPE', 'VALUE']
if Integer(split_line.first, 16) == target_offset
section, offset = split_line[2].split('+')
p line if $DEBUG
return section, Integer(offset, 16)
end
end
end
raise 'Failed to find relocation info for the target instruction'
end
def objdump_disassemble_command(offset)
case target_platform
when :darwin
"objdump --x86-asm-syntax=intel --start-address=#{offset} --stop-address=#{offset+50} -d vm.o"
when :linux
"objdump -M intel --start-address=#{offset} --stop-address=#{offset+50} -d vm.o"
else
raise "unkown platform"
end
end
def disassemble(offset)
command = objdump_disassemble_command(offset)
puts "Running: #{command}"
disassembly = `#{command}`
instructions = []
puts disassembly if $DEBUG
disassembly.each_line do |line|
line = line.strip
match_data = /\s*\h+:\s*((?:\h\h\s)+)\s+(\w+)/.match(line)
if match_data
bytes = match_data[1]
mnemonic = match_data[2]
instructions << [bytes, mnemonic, line]
break if mnemonic == 'jmp'
elsif !instructions.empty?
p line
raise "expected a continuous sequence of disassembly lines"
end
end
jmp_idx = instructions.find_index { |_, mnemonic, _| mnemonic == 'jmp' }
raise 'failed to find jmp' unless jmp_idx
raise 'generated code for example too long' unless jmp_idx < 10
handler_instructions = instructions[(0..jmp_idx)]
disassembly_lines = handler_instructions.map {|_, _, line| line}
puts "Disassembly for the example handler:"
puts disassembly_lines
raise 'rip reference in example makes copying unsafe' if handler_instructions.any? { |_, _, full_line| full_line.downcase.include?('rip') }
acceptable_mnemonics = %w(mov jmp lea call endbr64)
unrecognized = nil
handler_instructions.each { |i| unrecognized = i unless acceptable_mnemonics.include?(i[1]) }
raise "found an unrecognized \"#{unrecognized[1]}\" instruction in the example. List of recognized instructions: #{acceptable_mnemonics.join(', ')}" if unrecognized
raise 'found multiple jmp instructions' if handler_instructions.count { |_, mnemonic, _| mnemonic == 'jmp' } > 1
raise "the jmp instruction seems to be relative which isn't copiable" if instructions[jmp_idx][0].split.size > 4
raise 'no call instructions found' if handler_instructions.count { |_, mnemonic, _| mnemonic == 'call' } == 0
raise 'found multiple call instructions' if handler_instructions.count { |_, mnemonic, _| mnemonic == 'call' } > 1
call_idx = handler_instructions.find_index { |_, mnemonic, _| mnemonic == 'call' }
pre_call_bytes = []
post_call_bytes = []
handler_instructions.take(call_idx).each do |bytes, mnemonic, _|
pre_call_bytes += bytes.split
end
handler_instructions[call_idx + 1, handler_instructions.size].each do |bytes, _, _|
post_call_bytes += bytes.split
end
ScrapeResult.new(
comma_separated_hex_string(pre_call_bytes),
comma_separated_hex_string(post_call_bytes),
disassembly_lines
)
end
def darwin_scrape(instruction_id)
fileoff = get_fileoff
tc_table_offset = get_symbol_offset('vm_exec_core.insns_address_table')
vm_exec_core_offset = get_symbol_offset('vm_exec_core')
p instruction_id if $DEBUG
p fileoff if $DEBUG
p tc_table_offset.to_s(16) if $DEBUG
offset_to_insn_in_tc_table = fileoff + tc_table_offset + 8 * instruction_id
p offset_to_insn_in_tc_table if $DEBUG
offset_to_handler_code_from_vm_exec_core = readint8b(offset_to_insn_in_tc_table)
p offset_to_handler_code_from_vm_exec_core if $DEBUG
disassemble(vm_exec_core_offset + offset_to_handler_code_from_vm_exec_core)
end
def linux_scrape(instruction_id)
table_section, table_offset = get_symbol_section_and_offset('vm_exec_core.insns_address_table')
p [table_section, table_offset] if $DEBUG
handler_section, handler_offset = get_handler_offset(table_section, table_offset, instruction_id)
p [handler_section, handler_offset] if $DEBUG
disassemble(handler_offset)
end
def make_result(success, with_pc)
[success ? 1 : 0,
[
['ujit_with_ec', with_pc],
]
]
end
def scrape_instruction(instruction_id)
raise unless instruction_id.is_a?(Integer)
case target_platform
when :darwin
darwin_scrape(instruction_id)
when :linux
linux_scrape(instruction_id)
else
raise 'Unknown platform. Only Mach-O on macOS and ELF on Linux are supported'
end
end
def scrape
with_ec = scrape_instruction(RubyVM::Instructions.find_index { |insn| insn.name == 'ujit_call_example_with_ec' })
make_result(true, with_ec)
rescue => e
print_warning("scrape failed: #{e.message}")
int3 = '0xcc'
failure_result = ScrapeResult.new(int3, int3, ['int3'])
make_result(false, failure_result)
end
def print_warning(text)
text = "ujit warning: #{text}"
text = "\x1b[1m#{text}\x1b[0m" if STDOUT.tty?
STDOUT.puts(text)
end
def comma_separated_hex_string(nums)
nums.map{ |byte| '0x'+byte}.join(', ')
end
end
end
require_relative 'micro_jit/example_instructions'
|
