| # Copyright 2011-2016 Free Software Foundation, Inc. |
| # |
| # This is free software: you can redistribute it and/or modify it |
| # under the terms of the GNU General Public License as published by |
| # the Free Software Foundation, either version 3 of the License, or |
| # (at your option) any later version. |
| # |
| # This program is distributed in the hope that it will be useful, but |
| # WITHOUT ANY WARRANTY; without even the implied warranty of |
| # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| # General Public License for more details. |
| # |
| # You should have received a copy of the GNU General Public License |
| # along with this program. If not, see |
| # <http://www.gnu.org/licenses/>. |
| |
| # This is a GCC plugin that computes some exception-handling data for |
| # gdb. This data can then be summarized and checked by the |
| # exsummary.py script. |
| |
| # To use: |
| # * First, install the GCC Python plugin. See |
| # https://fedorahosted.org/gcc-python-plugin/ |
| # * export PYTHON_PLUGIN=/full/path/to/plugin/directory |
| # This should be the directory holding "python.so". |
| # * cd build/gdb; make mostlyclean |
| # * make CC=.../gcc-with-excheck |
| # This will write a number of .py files in the build directory. |
| # * python .../exsummary.py |
| # This will show the violations. |
| |
| import gcc |
| import gccutils |
| import sys |
| |
| # Where our output goes. |
| output_file = None |
| |
| # Cleanup functions require special treatment, because they take a |
| # function argument, but in theory the function must be nothrow. |
| cleanup_functions = { |
| 'make_cleanup': 1, |
| 'make_cleanup_dtor': 1, |
| 'make_final_cleanup': 1, |
| 'make_my_cleanup2': 1, |
| 'make_my_cleanup': 1 |
| } |
| |
| # Functions which may throw but which we want to ignore. |
| ignore_functions = { |
| # This one is super special. |
| 'exceptions_state_mc': 1, |
| # gdb generally pretends that internal_error cannot throw, even |
| # though it can. |
| 'internal_error': 1, |
| # do_cleanups and friends are supposedly nothrow but we don't want |
| # to run afoul of the indirect function call logic. |
| 'do_cleanups': 1, |
| 'do_final_cleanups': 1 |
| } |
| |
| # Functions which take a function argument, but which are not |
| # interesting, usually because the argument is not called in the |
| # current context. |
| non_passthrough_functions = { |
| 'signal': 1, |
| 'add_internal_function': 1 |
| } |
| |
| # Return True if the type is from Python. |
| def type_is_pythonic(t): |
| if isinstance(t, gcc.ArrayType): |
| t = t.type |
| if not isinstance(t, gcc.RecordType): |
| return False |
| # Hack. |
| return str(t).find('struct Py') == 0 |
| |
| # Examine all the fields of a struct. We don't currently need any |
| # sort of recursion, so this is simple for now. |
| def examine_struct_fields(initializer): |
| global output_file |
| for idx2, value2 in initializer.elements: |
| if isinstance(idx2, gcc.Declaration): |
| if isinstance(value2, gcc.AddrExpr): |
| value2 = value2.operand |
| if isinstance(value2, gcc.FunctionDecl): |
| output_file.write("declare_nothrow(%s)\n" |
| % repr(str(value2.name))) |
| |
| # Examine all global variables looking for pointers to functions in |
| # structures whose types were defined by Python. |
| def examine_globals(): |
| global output_file |
| vars = gcc.get_variables() |
| for var in vars: |
| if not isinstance(var.decl, gcc.VarDecl): |
| continue |
| output_file.write("################\n") |
| output_file.write("# Analysis for %s\n" % var.decl.name) |
| if not var.decl.initial: |
| continue |
| if not type_is_pythonic(var.decl.type): |
| continue |
| |
| if isinstance(var.decl.type, gcc.ArrayType): |
| for idx, value in var.decl.initial.elements: |
| examine_struct_fields(value) |
| else: |
| gccutils.check_isinstance(var.decl.type, gcc.RecordType) |
| examine_struct_fields(var.decl.initial) |
| |
| # Called at the end of compilation to write out some data derived from |
| # globals and to close the output. |
| def close_output(*args): |
| global output_file |
| examine_globals() |
| output_file.close() |
| |
| # The pass which derives some exception-checking information. We take |
| # a two-step approach: first we get a call graph from the compiler. |
| # This is emitted by the plugin as Python code. Then, we run a second |
| # program that reads all the generated Python and uses it to get a |
| # global view of exception routes in gdb. |
| class GdbExceptionChecker(gcc.GimplePass): |
| def __init__(self, output_file): |
| gcc.GimplePass.__init__(self, 'gdb_exception_checker') |
| self.output_file = output_file |
| |
| def log(self, obj): |
| self.output_file.write("# %s\n" % str(obj)) |
| |
| # Return true if FN is a call to a method on a Python object. |
| # We know these cannot throw in the gdb sense. |
| def fn_is_python_ignorable(self, fn): |
| if not isinstance(fn, gcc.SsaName): |
| return False |
| stmt = fn.def_stmt |
| if not isinstance(stmt, gcc.GimpleAssign): |
| return False |
| if stmt.exprcode is not gcc.ComponentRef: |
| return False |
| rhs = stmt.rhs[0] |
| if not isinstance(rhs, gcc.ComponentRef): |
| return False |
| if not isinstance(rhs.field, gcc.FieldDecl): |
| return False |
| return rhs.field.name == 'tp_dealloc' or rhs.field.name == 'tp_free' |
| |
| # Decode a function call and write something to the output. |
| # THIS_FUN is the enclosing function that we are processing. |
| # FNDECL is the call to process; it might not actually be a DECL |
| # node. |
| # LOC is the location of the call. |
| def handle_one_fndecl(self, this_fun, fndecl, loc): |
| callee_name = '' |
| if isinstance(fndecl, gcc.AddrExpr): |
| fndecl = fndecl.operand |
| if isinstance(fndecl, gcc.FunctionDecl): |
| # Ordinary call to a named function. |
| callee_name = str(fndecl.name) |
| self.output_file.write("function_call(%s, %s, %s)\n" |
| % (repr(callee_name), |
| repr(this_fun.decl.name), |
| repr(str(loc)))) |
| elif self.fn_is_python_ignorable(fndecl): |
| # Call to tp_dealloc. |
| pass |
| elif (isinstance(fndecl, gcc.SsaName) |
| and isinstance(fndecl.var, gcc.ParmDecl)): |
| # We can ignore an indirect call via a parameter to the |
| # current function, because this is handled via the rule |
| # for passthrough functions. |
| pass |
| else: |
| # Any other indirect call. |
| self.output_file.write("has_indirect_call(%s, %s)\n" |
| % (repr(this_fun.decl.name), |
| repr(str(loc)))) |
| return callee_name |
| |
| # This does most of the work for examine_one_bb. |
| # THIS_FUN is the enclosing function. |
| # BB is the basic block to process. |
| # Returns True if this block is the header of a TRY_CATCH, False |
| # otherwise. |
| def examine_one_bb_inner(self, this_fun, bb): |
| if not bb.gimple: |
| return False |
| try_catch = False |
| for stmt in bb.gimple: |
| loc = stmt.loc |
| if not loc: |
| loc = this_fun.decl.location |
| if not isinstance(stmt, gcc.GimpleCall): |
| continue |
| callee_name = self.handle_one_fndecl(this_fun, stmt.fn, loc) |
| |
| if callee_name == 'exceptions_state_mc_action_iter': |
| try_catch = True |
| |
| global non_passthrough_functions |
| if callee_name in non_passthrough_functions: |
| continue |
| |
| # We have to specially handle calls where an argument to |
| # the call is itself a function, e.g., qsort. In general |
| # we model these as "passthrough" -- we assume that in |
| # addition to the call the qsort there is also a call to |
| # the argument function. |
| for arg in stmt.args: |
| # We are only interested in arguments which are functions. |
| t = arg.type |
| if isinstance(t, gcc.PointerType): |
| t = t.dereference |
| if not isinstance(t, gcc.FunctionType): |
| continue |
| |
| if isinstance(arg, gcc.AddrExpr): |
| arg = arg.operand |
| |
| global cleanup_functions |
| if callee_name in cleanup_functions: |
| if not isinstance(arg, gcc.FunctionDecl): |
| gcc.inform(loc, 'cleanup argument not a DECL: %s' % repr(arg)) |
| else: |
| # Cleanups must be nothrow. |
| self.output_file.write("declare_cleanup(%s)\n" |
| % repr(str(arg.name))) |
| else: |
| # Assume we have a passthrough function, like |
| # qsort or an iterator. We model this by |
| # pretending there is an ordinary call at this |
| # point. |
| self.handle_one_fndecl(this_fun, arg, loc) |
| return try_catch |
| |
| # Examine all the calls in a basic block and generate output for |
| # them. |
| # THIS_FUN is the enclosing function. |
| # BB is the basic block to examine. |
| # BB_WORKLIST is a list of basic blocks to work on; we add the |
| # appropriate successor blocks to this. |
| # SEEN_BBS is a map whose keys are basic blocks we have already |
| # processed. We use this to ensure that we only visit a given |
| # block once. |
| def examine_one_bb(self, this_fun, bb, bb_worklist, seen_bbs): |
| try_catch = self.examine_one_bb_inner(this_fun, bb) |
| for edge in bb.succs: |
| if edge.dest in seen_bbs: |
| continue |
| seen_bbs[edge.dest] = 1 |
| if try_catch: |
| # This is bogus, but we magically know the right |
| # answer. |
| if edge.false_value: |
| bb_worklist.append(edge.dest) |
| else: |
| bb_worklist.append(edge.dest) |
| |
| # Iterate over all basic blocks in THIS_FUN. |
| def iterate_bbs(self, this_fun): |
| # Iteration must be in control-flow order, because if we see a |
| # TRY_CATCH construct we need to drop all the contained blocks. |
| bb_worklist = [this_fun.cfg.entry] |
| seen_bbs = {} |
| seen_bbs[this_fun.cfg.entry] = 1 |
| for bb in bb_worklist: |
| self.examine_one_bb(this_fun, bb, bb_worklist, seen_bbs) |
| |
| def execute(self, fun): |
| if fun and fun.cfg and fun.decl: |
| self.output_file.write("################\n") |
| self.output_file.write("# Analysis for %s\n" % fun.decl.name) |
| self.output_file.write("define_function(%s, %s)\n" |
| % (repr(fun.decl.name), |
| repr(str(fun.decl.location)))) |
| |
| global ignore_functions |
| if fun.decl.name not in ignore_functions: |
| self.iterate_bbs(fun) |
| |
| def main(**kwargs): |
| global output_file |
| output_file = open(gcc.get_dump_base_name() + '.gdb_exc.py', 'w') |
| # We used to use attributes here, but there didn't seem to be a |
| # big benefit over hard-coding. |
| output_file.write('declare_throw("throw_exception")\n') |
| output_file.write('declare_throw("throw_verror")\n') |
| output_file.write('declare_throw("throw_vfatal")\n') |
| output_file.write('declare_throw("throw_error")\n') |
| gcc.register_callback(gcc.PLUGIN_FINISH_UNIT, close_output) |
| ps = GdbExceptionChecker(output_file) |
| ps.register_after('ssa') |
| |
| main() |
