#!/usr/bin/python3
# Parsing dwarfdump's output to determine whether the location list for the
# parameter "b" covers all of the function. The script searches for information
# in the input file to determine the [prologue, epilogue) range for the
# function, the location list range for "b", and checks that the latter covers
# the entirety of the former.
import re
import sys
DebugInfoPattern = r"\.debug_info contents:"
DebugLinePattern = r"\.debug_line contents:"
ProloguePattern = r"^\s*0x([0-9a-f]+)\s.+prologue_end"
EpiloguePattern = r"^\s*0x([0-9a-f]+)\s.+epilogue_begin"
FormalPattern = r"^0x[0-9a-f]+:\s+DW_TAG_formal_parameter"
LocationPattern = r"DW_AT_location\s+\[DW_FORM_([a-z_]+)\](?:.*0x([a-f0-9]+))"
DebugLocPattern = r'\[0x([a-f0-9]+),\s+0x([a-f0-9]+)\) ".text": (.+)$'
SeenDebugInfo = False
SeenDebugLine = False
LocationRanges = None
PrologueEnd = None
EpilogueBegin = None
# The dwarfdump output should contain the DW_AT_location for "b" first, then the
# line table which should contain prologue_end and epilogue_begin entries.
with open(sys.argv[1], "r") as dwarf_dump_file:
dwarf_iter = iter(dwarf_dump_file)
for line in dwarf_iter:
if not SeenDebugInfo and re.match(DebugInfoPattern, line):
SeenDebugInfo = True
if not SeenDebugLine and re.match(DebugLinePattern, line):
SeenDebugLine = True
# Get the range of DW_AT_location for "b".
if LocationRanges is None:
if match := re.match(FormalPattern, line):
# Go until we either find DW_AT_location or reach the end of this entry.
location_match = None
while location_match is None:
if (line := next(dwarf_iter, "")) == "\n":
raise RuntimeError(
".debug_info output is missing DW_AT_location for 'b'"
)
location_match = re.search(LocationPattern, line)
# Variable has whole-scope location, represented by an empty tuple.
if location_match.group(1) == "exprloc":
LocationRanges = ()
continue
if location_match.group(1) != "sec_offset":
raise RuntimeError(
f"Unhandled form for DW_AT_location: DW_FORM_{location_match.group(1)}"
)
# Variable has location range list.
if (
debug_loc_match := re.search(DebugLocPattern, next(dwarf_iter, ""))
) is None:
raise RuntimeError(f"Invalid location range list for 'b'")
LocationRanges = (
int(debug_loc_match.group(1), 16),
int(debug_loc_match.group(2), 16),
)
while (
debug_loc_match := re.search(DebugLocPattern, next(dwarf_iter, ""))
) is not None:
match_loc_start = int(debug_loc_match.group(1), 16)
match_loc_end = int(debug_loc_match.group(2), 16)
match_expr = debug_loc_match.group(3)
if match_loc_start != LocationRanges[1]:
raise RuntimeError(
f"Location list for 'b' is discontinuous from [0x{LocationRanges[1]:x}, 0x{match_loc_start:x})"
)
if "stack_value" in match_expr:
raise RuntimeError(
f"Location list for 'b' contains a stack_value expression: {match_expr}"
)
LocationRanges = (LocationRanges[0], match_loc_end)
# Get the prologue_end address.
elif PrologueEnd is None:
if match := re.match(ProloguePattern, line):
PrologueEnd = int(match.group(1), 16)
# Get the epilogue_begin address.
elif EpilogueBegin is None:
if match := re.match(EpiloguePattern, line):
EpilogueBegin = int(match.group(1), 16)
break
if not SeenDebugInfo:
raise RuntimeError(".debug_info section not found.")
if not SeenDebugLine:
raise RuntimeError(".debug_line section not found.")
if LocationRanges is None:
raise RuntimeError(".debug_info output is missing parameter 'b'")
if PrologueEnd is None:
raise RuntimeError(".debug_line output is missing prologue_end")
if EpilogueBegin is None:
raise RuntimeError(".debug_line output is missing epilogue_begin")
if len(LocationRanges) == 2 and (
LocationRanges[0] > PrologueEnd or LocationRanges[1] < EpilogueBegin
):
raise RuntimeError(
f"""Location list for 'b' does not cover the whole function:")
Prologue to Epilogue = [0x{PrologueEnd:x}, 0x{EpilogueBegin:x})
Location range = [0x{LocationRanges[0]:x}, 0x{LocationRanges[1]:x})
"""
)
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