1 /* An experimental state machine, for tracking bad calls from within
4 Copyright (C) 2019-2020 Free Software Foundation, Inc.
5 Contributed by David Malcolm <dmalcolm@redhat.com>.
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify it
10 under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3, or (at your option)
14 GCC is distributed in the hope that it will be useful, but
15 WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with GCC; see the file COPYING3. If not see
21 <http://www.gnu.org/licenses/>. */
25 #include "coretypes.h"
28 #include "basic-block.h"
32 #include "diagnostic-path.h"
33 #include "diagnostic-metadata.h"
35 #include "analyzer/analyzer.h"
36 #include "diagnostic-event-id.h"
37 #include "analyzer/analyzer-logging.h"
38 #include "analyzer/sm.h"
39 #include "analyzer/pending-diagnostic.h"
42 #include "ordered-hash-map.h"
44 #include "analyzer/region-model.h"
45 #include "analyzer/program-state.h"
46 #include "analyzer/checker-path.h"
49 #include "gimple-iterator.h"
51 #include "analyzer/supergraph.h"
52 #include "analyzer/call-string.h"
53 #include "analyzer/program-point.h"
54 #include "alloc-pool.h"
55 #include "fibonacci_heap.h"
56 #include "analyzer/diagnostic-manager.h"
57 #include "shortest-paths.h"
58 #include "analyzer/exploded-graph.h"
59 #include "analyzer/function-set.h"
60 #include "analyzer/analyzer-selftests.h"
66 /* An experimental state machine, for tracking calls to async-signal-unsafe
67 functions from within signal handlers. */
69 class signal_state_machine : public state_machine
72 signal_state_machine (logger *logger);
74 bool inherited_state_p () const FINAL OVERRIDE { return false; }
76 bool on_stmt (sm_context *sm_ctxt,
77 const supernode *node,
78 const gimple *stmt) const FINAL OVERRIDE;
80 void on_condition (sm_context *sm_ctxt,
81 const supernode *node,
85 tree rhs) const FINAL OVERRIDE;
87 bool can_purge_p (state_t s) const FINAL OVERRIDE;
89 /* These states are "global", rather than per-expression. */
94 /* State for when we're in a signal handler. */
95 state_t m_in_signal_handler;
101 /* Concrete subclass for describing call to an async-signal-unsafe function
102 from a signal handler. */
104 class signal_unsafe_call
105 : public pending_diagnostic_subclass<signal_unsafe_call>
108 signal_unsafe_call (const signal_state_machine &sm, const gcall *unsafe_call,
110 : m_sm (sm), m_unsafe_call (unsafe_call), m_unsafe_fndecl (unsafe_fndecl)
112 gcc_assert (m_unsafe_fndecl);
115 const char *get_kind () const FINAL OVERRIDE { return "signal_unsafe_call"; }
117 bool operator== (const signal_unsafe_call &other) const
119 return m_unsafe_call == other.m_unsafe_call;
122 bool emit (rich_location *rich_loc) FINAL OVERRIDE
124 diagnostic_metadata m;
125 /* CWE-479: Signal Handler Use of a Non-reentrant Function. */
127 return warning_at (rich_loc, m,
128 OPT_Wanalyzer_unsafe_call_within_signal_handler,
129 "call to %qD from within signal handler",
133 label_text describe_state_change (const evdesc::state_change &change)
136 if (change.is_global_p ()
137 && change.m_new_state == m_sm.m_in_signal_handler)
140 = change.m_event.m_dst_state.m_region_model->get_current_function ();
141 return change.formatted_print ("registering %qD as signal handler",
144 return label_text ();
147 label_text describe_final_event (const evdesc::final_event &ev) FINAL OVERRIDE
149 return ev.formatted_print ("call to %qD from within signal handler",
154 const signal_state_machine &m_sm;
155 const gcall *m_unsafe_call;
156 tree m_unsafe_fndecl;
159 /* signal_state_machine's ctor. */
161 signal_state_machine::signal_state_machine (logger *logger)
162 : state_machine ("signal", logger)
164 m_start = add_state ("start");
165 m_in_signal_handler = add_state ("in_signal_handler");
166 m_stop = add_state ("stop");
169 /* Update MODEL for edges that simulate HANDLER_FUN being called as
170 an signal-handler in response to a signal. */
173 update_model_for_signal_handler (region_model *model,
174 function *handler_fun)
176 /* Purge all state within MODEL. */
177 *model = region_model ();
178 model->push_frame (handler_fun, NULL, NULL);
181 /* Custom exploded_edge info: entry into a signal-handler. */
183 class signal_delivery_edge_info_t : public exploded_edge::custom_info_t
186 void print (pretty_printer *pp) FINAL OVERRIDE
188 pp_string (pp, "signal delivered");
191 void update_model (region_model *model,
192 const exploded_edge &eedge) FINAL OVERRIDE
194 update_model_for_signal_handler (model, eedge.m_dest->get_function ());
197 void add_events_to_path (checker_path *emission_path,
198 const exploded_edge &eedge ATTRIBUTE_UNUSED)
201 emission_path->add_event
202 (new custom_event (UNKNOWN_LOCATION, NULL_TREE, 0,
204 " when the signal is delivered to the process"));
208 /* Concrete subclass of custom_transition for modeling registration of a
209 signal handler and the signal handler later being called. */
211 class register_signal_handler : public custom_transition
214 register_signal_handler (const signal_state_machine &sm,
216 : m_sm (sm), m_fndecl (fndecl) {}
218 /* Model a signal-handler FNDECL being called at some later point
219 by injecting an edge to a new function-entry node with an empty
220 callstring, setting the 'in-signal-handler' global state
222 void impl_transition (exploded_graph *eg,
223 exploded_node *src_enode,
224 int sm_idx) FINAL OVERRIDE
226 function *handler_fun = DECL_STRUCT_FUNCTION (m_fndecl);
229 program_point entering_handler
230 = program_point::from_function_entry (eg->get_supergraph (),
233 program_state state_entering_handler (eg->get_ext_state ());
234 update_model_for_signal_handler (state_entering_handler.m_region_model,
236 state_entering_handler.m_checker_states[sm_idx]->set_global_state
237 (m_sm.m_in_signal_handler);
239 exploded_node *dst_enode = eg->get_or_create_node (entering_handler,
240 state_entering_handler,
243 eg->add_edge (src_enode, dst_enode, NULL, state_change (),
244 new signal_delivery_edge_info_t ());
247 const signal_state_machine &m_sm;
251 /* Get a set of functions that are known to be unsafe to call from an
252 async signal handler. */
255 get_async_signal_unsafe_fns ()
257 // TODO: populate this list more fully
258 static const char * const async_signal_unsafe_fns[] = {
259 /* This array must be kept sorted. */
272 = sizeof(async_signal_unsafe_fns) / sizeof (async_signal_unsafe_fns[0]);
273 function_set fs (async_signal_unsafe_fns, count);
277 /* Return true if FNDECL is known to be unsafe to call from a signal
281 signal_unsafe_p (tree fndecl)
283 function_set fs = get_async_signal_unsafe_fns ();
284 return fs.contains_decl_p (fndecl);
287 /* Implementation of state_machine::on_stmt vfunc for signal_state_machine. */
290 signal_state_machine::on_stmt (sm_context *sm_ctxt,
291 const supernode *node,
292 const gimple *stmt) const
294 const state_t global_state = sm_ctxt->get_global_state ();
295 if (global_state == m_start)
297 if (const gcall *call = dyn_cast <const gcall *> (stmt))
298 if (tree callee_fndecl = sm_ctxt->get_fndecl_for_call (call))
299 if (is_named_call_p (callee_fndecl, "signal", call, 2))
301 tree handler = gimple_call_arg (call, 1);
302 if (TREE_CODE (handler) == ADDR_EXPR
303 && TREE_CODE (TREE_OPERAND (handler, 0)) == FUNCTION_DECL)
305 tree fndecl = TREE_OPERAND (handler, 0);
306 register_signal_handler rsh (*this, fndecl);
307 sm_ctxt->on_custom_transition (&rsh);
311 else if (global_state == m_in_signal_handler)
313 if (const gcall *call = dyn_cast <const gcall *> (stmt))
314 if (tree callee_fndecl = sm_ctxt->get_fndecl_for_call (call))
315 if (signal_unsafe_p (callee_fndecl))
316 sm_ctxt->warn_for_state (node, stmt, NULL_TREE, m_in_signal_handler,
317 new signal_unsafe_call (*this, call,
324 /* Implementation of state_machine::on_condition vfunc for
325 signal_state_machine. */
328 signal_state_machine::on_condition (sm_context *sm_ctxt ATTRIBUTE_UNUSED,
329 const supernode *node ATTRIBUTE_UNUSED,
330 const gimple *stmt ATTRIBUTE_UNUSED,
331 tree lhs ATTRIBUTE_UNUSED,
332 enum tree_code op ATTRIBUTE_UNUSED,
333 tree rhs ATTRIBUTE_UNUSED) const
339 signal_state_machine::can_purge_p (state_t s ATTRIBUTE_UNUSED) const
344 } // anonymous namespace
346 /* Internal interface to this file. */
349 make_signal_state_machine (logger *logger)
351 return new signal_state_machine (logger);
358 /* Run all of the selftests within this file. */
361 analyzer_sm_signal_cc_tests ()
363 function_set fs = get_async_signal_unsafe_fns ();
368 } // namespace selftest
370 #endif /* CHECKING_P */
371 #endif /* #if ENABLE_ANALYZER */