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# Copyright 2022 The Emscripten Authors. All rights reserved.
# Emscripten is available under two separate licenses, the MIT license and the
# University of Illinois/NCSA Open Source License. Both these licenses can be
# found in the LICENSE file.
from . import webassembly
from .shared import exit_with_error
from .settings import settings
def is_wrapper_function(module, function):
module.seek(function.offset)
num_local_decls = module.readULEB()
while num_local_decls:
local_count = module.readULEB() # noqa
local_type = module.read_type() # noqa
num_local_decls -= 1
end = function.offset + function.size
while module.tell() != end:
opcode = module.readByte()
try:
opcode = webassembly.OpCode(opcode)
except ValueError as e:
print(e)
return False
if opcode == webassembly.OpCode.CALL:
callee = module.readULEB() # noqa
elif opcode == webassembly.OpCode.END:
break
else:
return False
assert opcode == webassembly.OpCode.END
return True
def get_const_expr_value(expr):
assert len(expr) == 2
assert expr[1][0] == webassembly.OpCode.END
opcode, immediates = expr[0]
if opcode in (webassembly.OpCode.I32_CONST, webassembly.OpCode.I64_CONST):
assert len(immediates) == 1
return immediates[0]
elif opcode in (webassembly.OpCode.GLOBAL_GET,):
return 0
else:
exit_with_error('unexpected opcode in const expr: ' + str(opcode))
def get_global_value(globl):
return get_const_expr_value(globl.init)
def find_segment_with_address(module, address, size=0):
segments = module.get_segments()
active = [s for s in segments if s.init]
for seg in active:
offset = get_const_expr_value(seg.init)
if offset is None:
continue
if offset == address:
return (seg, 0)
if address > offset and address < offset + seg.size:
return (seg, address - offset)
passive = [s for s in segments if not s.init]
for seg in passive:
if seg.size == size:
return (seg, 0)
def data_to_string(data):
data = data.decode('utf8')
# We have at least one test (tests/utf8.cpp) that uses a double
# backslash in the C++ source code, in order to represent a single backslash.
# This is because these strings historically were written and read back via
# JSON and a single slash is interpreted as an escape char there.
# Technically this escaping is no longer needed and could be removed
# but in order to maintain compatibility we strip out the double
# slashes here.
data = data.replace('\\\\', '\\')
return data
def get_asm_strings(module, globls, export_map, imported_globals):
if '__start_em_asm' not in export_map or '__stop_em_asm' not in export_map:
return {}
start = export_map['__start_em_asm']
end = export_map['__stop_em_asm']
start_global = globls[start.index - imported_globals]
end_global = globls[end.index - imported_globals]
start_addr = get_global_value(start_global)
end_addr = get_global_value(end_global)
seg = find_segment_with_address(module, start_addr, end_addr - start_addr)
if not seg:
exit_with_error('unable to find segment starting at __start_em_asm: %s' % start_addr)
seg, seg_offset = seg
asm_strings = {}
str_start = seg_offset
data = module.readAt(seg.offset, seg.size)
size = end_addr - start_addr
end = seg_offset + size
while str_start < end:
str_end = data.find(b'\0', str_start)
asm_strings[str(start_addr - seg_offset + str_start)] = data_to_string(data[str_start:str_end])
str_start = str_end + 1
return asm_strings
def get_main_reads_params(module, export_map, imported_funcs):
if settings.STANDALONE_WASM:
return 1
main = export_map.get('main')
if not main or main.kind != webassembly.ExternType.FUNC:
return 0
functions = module.get_functions()
main_func = functions[main.index - imported_funcs]
if is_wrapper_function(module, main_func):
return 0
else:
return 1
def get_names_globals(globls, exports, imported_globals):
named_globals = {}
for export in exports:
if export.kind == webassembly.ExternType.GLOBAL:
if export.name in ('__start_em_asm', '__stop_em_asm') or export.name.startswith('__em_js__'):
continue
g = globls[export.index - imported_globals]
named_globals[export.name] = str(get_global_value(g))
return named_globals
def update_metadata(filename, metadata):
declares = []
invoke_funcs = []
em_js_funcs = set(metadata['emJsFuncs'])
module = webassembly.Module(filename)
for i in module.get_imports():
if i.kind == webassembly.ExternType.FUNC:
if i.field.startswith('invoke_'):
invoke_funcs.append(i.field)
elif i.field not in em_js_funcs:
declares.append(i.field)
exports = [e.name for e in module.get_exports() if e.kind == webassembly.ExternType.FUNC]
metadata['declares'] = declares
metadata['exports'] = exports
metadata['invokeFuncs'] = invoke_funcs
def get_string_at(module, address):
seg, offset = find_segment_with_address(module, address)
data = module.readAt(seg.offset, seg.size)
str_end = data.find(b'\0', offset)
return data_to_string(data[offset:str_end])
def extract_metadata(filename):
module = webassembly.Module(filename)
export_names = []
declares = []
invoke_funcs = []
imported_funcs = 0
imported_globals = 0
global_imports = []
em_js_funcs = {}
exports = module.get_exports()
imports = module.get_imports()
globls = module.get_globals()
for i in imports:
if i.kind == webassembly.ExternType.FUNC:
if i.field.startswith('invoke_'):
invoke_funcs.append(i.field)
elif i.field not in em_js_funcs:
declares.append(i.field)
imported_funcs += 1
elif i.kind == webassembly.ExternType.GLOBAL:
imported_globals += 1
global_imports.append(i.field)
export_map = {e.name: e for e in exports}
for e in exports:
if e.kind == webassembly.ExternType.GLOBAL and e.name.startswith('__em_js__'):
name = e.name[len('__em_js__'):]
globl = globls[e.index - imported_globals]
string_address = get_global_value(globl)
em_js_funcs[name] = get_string_at(module, string_address)
export_names = [e.name for e in exports if e.kind == webassembly.ExternType.FUNC]
features = module.parse_features_section()
features = ['--enable-' + f[1] for f in features if f[0] == '+']
features = [f.replace('--enable-atomics', '--enable-threads') for f in features]
features = [f.replace('--enable-simd128', '--enable-simd') for f in features]
features = [f.replace('--enable-nontrapping-fptoint', '--enable-nontrapping-float-to-int') for f in features]
# If main does not read its parameters, it will just be a stub that
# calls __original_main (which has no parameters).
metadata = {}
metadata['asmConsts'] = get_asm_strings(module, globls, export_map, imported_globals)
metadata['declares'] = declares
metadata['emJsFuncs'] = em_js_funcs
metadata['exports'] = export_names
metadata['features'] = features
metadata['globalImports'] = global_imports
metadata['invokeFuncs'] = invoke_funcs
metadata['mainReadsParams'] = get_main_reads_params(module, export_map, imported_funcs)
metadata['namedGlobals'] = get_names_globals(globls, exports, imported_globals)
# print("Metadata parsed: " + pprint.pformat(metadata))
return metadata
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