1/*
2 * Copyright 2011-2016 by Emese Revfy <re.emese@gmail.com>
3 * Licensed under the GPL v2, or (at your option) v3
4 *
5 * Homepage:
6 * https://github.com/ephox-gcc-plugins/sancov
7 *
8 * This plugin inserts a __sanitizer_cov_trace_pc() call at the start of basic blocks.
9 * It supports all gcc versions with plugin support (from gcc-4.5 on).
10 * It is based on the commit "Add fuzzing coverage support" by Dmitry Vyukov <dvyukov@google.com>.
11 *
12 * You can read about it more here:
13 *  https://gcc.gnu.org/viewcvs/gcc?limit_changes=0&view=revision&revision=231296
14 *  https://lwn.net/Articles/674854/
15 *  https://github.com/google/syzkaller
16 *  https://lwn.net/Articles/677764/
17 *
18 * Usage:
19 * make run
20 */
21
22#include "gcc-common.h"
23
24__visible int plugin_is_GPL_compatible;
25
26tree sancov_fndecl;
27
28static struct plugin_info sancov_plugin_info = {
29	.version	= PLUGIN_VERSION,
30	.help		= "sancov plugin\n",
31};
32
33static unsigned int sancov_execute(void)
34{
35	basic_block bb;
36
37	/* Remove this line when this plugin and kcov will be in the kernel.
38	if (!strcmp(DECL_NAME_POINTER(current_function_decl), DECL_NAME_POINTER(sancov_fndecl)))
39		return 0;
40	*/
41
42	FOR_EACH_BB_FN(bb, cfun) {
43		const_gimple stmt;
44		gcall *gcall;
45		gimple_stmt_iterator gsi = gsi_after_labels(bb);
46
47		if (gsi_end_p(gsi))
48			continue;
49
50		stmt = gsi_stmt(gsi);
51		gcall = as_a_gcall(gimple_build_call(sancov_fndecl, 0));
52		gimple_set_location(gcall, gimple_location(stmt));
53		gsi_insert_before(&gsi, gcall, GSI_SAME_STMT);
54	}
55	return 0;
56}
57
58#define PASS_NAME sancov
59
60#define NO_GATE
61#define TODO_FLAGS_FINISH TODO_dump_func | TODO_verify_stmts | TODO_update_ssa_no_phi | TODO_verify_flow
62
63#include "gcc-generate-gimple-pass.h"
64
65static void sancov_start_unit(void __unused *gcc_data, void __unused *user_data)
66{
67	tree leaf_attr, nothrow_attr;
68	tree BT_FN_VOID = build_function_type_list(void_type_node, NULL_TREE);
69
70	sancov_fndecl = build_fn_decl("__sanitizer_cov_trace_pc", BT_FN_VOID);
71
72	DECL_ASSEMBLER_NAME(sancov_fndecl);
73	TREE_PUBLIC(sancov_fndecl) = 1;
74	DECL_EXTERNAL(sancov_fndecl) = 1;
75	DECL_ARTIFICIAL(sancov_fndecl) = 1;
76	DECL_PRESERVE_P(sancov_fndecl) = 1;
77	DECL_UNINLINABLE(sancov_fndecl) = 1;
78	TREE_USED(sancov_fndecl) = 1;
79
80	nothrow_attr = tree_cons(get_identifier("nothrow"), NULL, NULL);
81	decl_attributes(&sancov_fndecl, nothrow_attr, 0);
82	gcc_assert(TREE_NOTHROW(sancov_fndecl));
83	leaf_attr = tree_cons(get_identifier("leaf"), NULL, NULL);
84	decl_attributes(&sancov_fndecl, leaf_attr, 0);
85}
86
87__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
88{
89	int i;
90	const char * const plugin_name = plugin_info->base_name;
91	const int argc = plugin_info->argc;
92	const struct plugin_argument * const argv = plugin_info->argv;
93	bool enable = true;
94
95	static const struct ggc_root_tab gt_ggc_r_gt_sancov[] = {
96		{
97			.base = &sancov_fndecl,
98			.nelt = 1,
99			.stride = sizeof(sancov_fndecl),
100			.cb = &gt_ggc_mx_tree_node,
101			.pchw = &gt_pch_nx_tree_node
102		},
103		LAST_GGC_ROOT_TAB
104	};
105
106	/* BBs can be split afterwards?? */
107	PASS_INFO(sancov, "asan", 0, PASS_POS_INSERT_BEFORE);
108
109	if (!plugin_default_version_check(version, &gcc_version)) {
110		error(G_("incompatible gcc/plugin versions"));
111		return 1;
112	}
113
114	for (i = 0; i < argc; ++i) {
115		if (!strcmp(argv[i].key, "no-sancov")) {
116			enable = false;
117			continue;
118		}
119		error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
120	}
121
122	register_callback(plugin_name, PLUGIN_INFO, NULL, &sancov_plugin_info);
123
124	if (!enable)
125		return 0;
126
127#if BUILDING_GCC_VERSION < 6000
128	register_callback(plugin_name, PLUGIN_START_UNIT, &sancov_start_unit, NULL);
129	register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL, (void *)&gt_ggc_r_gt_sancov);
130	register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &sancov_pass_info);
131#endif
132
133	return 0;
134}
135