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 
26 tree sancov_fndecl;
27 
28 static struct plugin_info sancov_plugin_info = {
29 	.version	= PLUGIN_VERSION,
30 	.help		= "sancov plugin\n",
31 };
32 
sancov_execute(void)33 static 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 
sancov_start_unit(void __unused * gcc_data,void __unused * user_data)65 static 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 
plugin_init(struct plugin_name_args * plugin_info,struct plugin_gcc_version * version)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