1/*
2 * Copyright (C) 2012 Oracle.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
16 */
17
18/*
19 * This is almost the same as smatch_param_filter.c.  The difference is that
20 * this only deals with values passed on the stack and param filter only deals
21 * with values changed so that the caller sees the new value.  It other words
22 * the key for these should always be "$" and the key for param_filter should
23 * never be "$".  Also smatch_param_set() should never use "$" as the key.
24 * Param set should work together with param_filter to determine the value that
25 * the caller sees at the end.
26 *
27 * This is for functions like this:
28 *
29 * int foo(int a)
30 * {
31 *        if (a >= 0 && a < 10) {
32 *                 a = 42;
33 *                 return 1;
34 *        }
35 *        return 0;
36 * }
37 *
38 * If we pass in 5, it returns 1.
39 *
40 * It's a bit complicated because we can't just consider the final value, we
41 * have to always consider the passed in value.
42 *
43 */
44
45#include "scope.h"
46#include "smatch.h"
47#include "smatch_extra.h"
48#include "smatch_slist.h"
49
50static int my_id;
51
52static struct stree *start_states;
53static struct stree_stack *saved_stack;
54
55static void save_start_states(struct statement *stmt)
56{
57	start_states = get_all_states_stree(SMATCH_EXTRA);
58}
59
60static void free_start_states(void)
61{
62	free_stree(&start_states);
63}
64
65static struct smatch_state *unmatched_state(struct sm_state *sm)
66{
67	struct smatch_state *state;
68
69	state = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
70	if (state)
71		return state;
72	return alloc_estate_whole(estate_type(sm->state));
73}
74
75struct smatch_state *get_orig_estate(const char *name, struct symbol *sym)
76{
77	struct smatch_state *state;
78
79	state = get_state(my_id, name, sym);
80	if (state)
81		return state;
82
83	state = get_state(SMATCH_EXTRA, name, sym);
84	if (state)
85		return state;
86	return alloc_estate_rl(alloc_whole_rl(get_real_base_type(sym)));
87}
88
89struct smatch_state *get_orig_estate_type(const char *name, struct symbol *sym, struct symbol *type)
90{
91	struct smatch_state *state;
92
93	state = get_state(my_id, name, sym);
94	if (state)
95		return state;
96
97	state = get_state(SMATCH_EXTRA, name, sym);
98	if (state)
99		return state;
100	return alloc_estate_rl(alloc_whole_rl(type));
101}
102
103static struct range_list *generify_mtag_range(struct smatch_state *state)
104{
105	struct range_list *rl;
106	struct data_range *drange;
107
108	if (!estate_type(state) || estate_type(state)->type != SYM_PTR)
109		return estate_rl(state);
110
111	/*
112	 * The problem is that we get too specific on our param limits when we
113	 * know exactly what pointers are passed to a function.  It gets to the
114	 * point where we say "pointer x will succeed, but everything else will
115	 * fail."  And then we introduce a new caller which passes a different
116	 * pointer and it's like, "Sorry bro, that's not possible."
117	 *
118	 */
119	rl = estate_rl(state);
120	FOR_EACH_PTR(rl, drange) {
121		if (drange->min.value != drange->max.value)
122			continue;
123		if (drange->min.value == 0)
124			continue;
125		if (is_err_ptr(drange->min))
126			continue;
127		return rl_union(valid_ptr_rl, rl);
128	} END_FOR_EACH_PTR(drange);
129
130	return estate_rl(state);
131}
132
133static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
134{
135	struct smatch_state *state, *old;
136	struct sm_state *tmp;
137	struct range_list *rl;
138	const char *param_name;
139	int param;
140
141	FOR_EACH_MY_SM(SMATCH_EXTRA, __get_cur_stree(), tmp) {
142		param = get_param_num_from_sym(tmp->sym);
143		if (param < 0)
144			continue;
145
146		param_name = get_param_name(tmp);
147		if (!param_name)
148			continue;
149
150		state = __get_state(my_id, tmp->name, tmp->sym);
151		if (!state)
152			state = tmp->state;
153
154		if (estate_is_whole(state) || estate_is_empty(state))
155			continue;
156		old = get_state_stree(start_states, SMATCH_EXTRA, tmp->name, tmp->sym);
157		if (old && rl_equiv(estate_rl(old), estate_rl(state)))
158			continue;
159
160		if (is_ignored_kernel_data(param_name))
161			continue;
162
163		rl = generify_mtag_range(state);
164		sql_insert_return_states(return_id, return_ranges, PARAM_LIMIT,
165					 param, param_name, show_rl(rl));
166	} END_FOR_EACH_SM(tmp);
167}
168
169static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
170{
171	struct smatch_state *orig_vals;
172	int param;
173
174	param = get_param_num_from_sym(sym);
175	if (param < 0)
176		return;
177
178	orig_vals = get_orig_estate_type(name, sym, estate_type(state));
179	set_state(my_id, name, sym, orig_vals);
180}
181
182static void match_save_states(struct expression *expr)
183{
184	push_stree(&saved_stack, start_states);
185	start_states = NULL;
186}
187
188static void match_restore_states(struct expression *expr)
189{
190	free_stree(&start_states);
191	start_states = pop_stree(&saved_stack);
192}
193
194void register_param_limit(int id)
195{
196	my_id = id;
197
198	set_dynamic_states(my_id);
199	add_hook(&save_start_states, AFTER_DEF_HOOK);
200	add_hook(&free_start_states, AFTER_FUNC_HOOK);
201
202	add_extra_mod_hook(&extra_mod_hook);
203	add_unmatched_state_hook(my_id, &unmatched_state);
204	add_merge_hook(my_id, &merge_estates);
205
206	add_hook(&match_save_states, INLINE_FN_START);
207	add_hook(&match_restore_states, INLINE_FN_END);
208
209	add_split_return_callback(&print_return_value_param);
210}
211
212