def CollectAliasesByAddress(elf_path, tool_prefix):
"""Runs nm on |elf_path| and returns a dict of address->[names]"""
# Constructors often show up twice, so use sets to ensure no duplicates.
names_by_address = collections.defaultdict(set)
# About 60mb of output, but piping takes ~30s, and loading it into RAM
# directly takes 3s.
args = [path_util.GetNmPath(tool_prefix), '--no-sort', '--defined-only',
elf_path]
output = subprocess.check_output(args)
for line in output.splitlines():
space_idx = line.find(' ')
address_str = line[:space_idx]
section = line[space_idx + 1]
mangled_name = line[space_idx + 3:]
# To verify that rodata does not have aliases:
# nm --no-sort --defined-only libchrome.so > nm.out
# grep -v '\$' nm.out | grep ' r ' | sort | cut -d' ' -f1 > addrs
# wc -l < addrs; uniq < addrs | wc -l
if section not in 'tTW' or not _IsRelevantNmName(mangled_name):
continue
address = int(address_str, 16)
if not address:
continue
names_by_address[address].add(mangled_name)
# Demangle all names.
names_by_address = demangle.DemangleSetsInDicts(names_by_address, tool_prefix)
# Since this is run in a separate process, minimize data passing by returning
# only aliased symbols.
# Also: Sort to ensure stable ordering.
return {k: sorted(v) for k, v in names_by_address.iteritems() if len(v) > 1}
def CollectAliasesByAddress(elf_path, tool_prefix):
"""Runs nm on |elf_path| and returns a dict of address->[names]"""
# Constructors often show up twice, so use sets to ensure no duplicates.
names_by_address = collections.defaultdict(set)
# Many OUTLINED_FUNCTION_* entries can coexist on a single address, possibly
# mixed with regular symbols. However, naively keeping these is bad because:
# * OUTLINED_FUNCTION_* can have many duplicates. Keeping them would cause
# false associations downstream, when looking up object_paths from names.
# * For addresses with multiple OUTLINED_FUNCTION_* entries, we can't get the
# associated object_path (exception: the one entry in the .map file, for LLD
# without ThinLTO). So keeping copies around is rather useless.
# Our solution is to merge OUTLINED_FUNCTION_* entries at the same address
# into a single symbol. We'd also like to keep track of the number of copies
# (although it will not be used to compute PSS computation). This is done by
# writing the count in the name, e.g., '** outlined function * 5'.
num_outlined_functions_at_address = collections.Counter()
# About 60mb of output, but piping takes ~30s, and loading it into RAM
# directly takes 3s.
args = [path_util.GetNmPath(tool_prefix), '--no-sort', '--defined-only',
elf_path]
# pylint: disable=unexpected-keyword-arg
proc = subprocess.Popen(
args, stdout=subprocess.PIPE, stderr=subprocess.PIPE, encoding='utf-8')
# llvm-nm may write to stderr. Discard to denoise.
stdout, _ = proc.communicate()
assert proc.returncode == 0
for line in stdout.splitlines():
space_idx = line.find(' ')
address_str = line[:space_idx]
section = line[space_idx + 1]
mangled_name = line[space_idx + 3:]
# To verify that rodata does not have aliases:
# nm --no-sort --defined-only libchrome.so > nm.out
# grep -v '\$' nm.out | grep ' r ' | sort | cut -d' ' -f1 > addrs
# wc -l < addrs; uniq < addrs | wc -l
if section not in 'tTW' or not _IsRelevantNmName(mangled_name):
continue
address = int(address_str, 16)
if not address:
continue
if mangled_name.startswith('OUTLINED_FUNCTION_'):
num_outlined_functions_at_address[address] += 1
else:
names_by_address[address].add(mangled_name)
# Need to add before demangling because |names_by_address| changes type.
for address, count in num_outlined_functions_at_address.items():
name = '** outlined function' + (' * %d' % count if count > 1 else '')
names_by_address[address].add(name)
# Demangle all names.
names_by_address = demangle.DemangleSetsInDicts(names_by_address, tool_prefix)
# Since this is run in a separate process, minimize data passing by returning
# only aliased symbols.
# Also: Sort to ensure stable ordering.
return {
addr: sorted(names, key=lambda n: (n.startswith('**'), n))
for addr, names in names_by_address.items()
if len(names) > 1 or num_outlined_functions_at_address.get(addr, 0) > 1
}