1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include "gcc-common.h"
4 
5 __visible int plugin_is_GPL_compatible;
6 
7 static unsigned int sp_mask, canary_offset;
8 
9 static unsigned int arm_pertask_ssp_rtl_execute(void)
10 {
11 	rtx_insn *insn;
12 
13 	for (insn = get_insns(); insn; insn = NEXT_INSN(insn)) {
14 		const char *sym;
15 		rtx body;
16 		rtx mask, masked_sp;
17 
18 		/*
19 		 * Find a SET insn involving a SYMBOL_REF to __stack_chk_guard
20 		 */
21 		if (!INSN_P(insn))
22 			continue;
23 		body = PATTERN(insn);
24 		if (GET_CODE(body) != SET ||
25 		    GET_CODE(SET_SRC(body)) != SYMBOL_REF)
26 			continue;
27 		sym = XSTR(SET_SRC(body), 0);
28 		if (strcmp(sym, "__stack_chk_guard"))
29 			continue;
30 
31 		/*
32 		 * Replace the source of the SET insn with an expression that
33 		 * produces the address of the copy of the stack canary value
34 		 * stored in struct thread_info
35 		 */
36 		mask = GEN_INT(sext_hwi(sp_mask, GET_MODE_PRECISION(Pmode)));
37 		masked_sp = gen_reg_rtx(Pmode);
38 
39 		emit_insn_before(gen_rtx_set(masked_sp,
40 					     gen_rtx_AND(Pmode,
41 							 stack_pointer_rtx,
42 							 mask)),
43 				 insn);
44 
45 		SET_SRC(body) = gen_rtx_PLUS(Pmode, masked_sp,
46 					     GEN_INT(canary_offset));
47 	}
48 	return 0;
49 }
50 
51 #define PASS_NAME arm_pertask_ssp_rtl
52 
53 #define NO_GATE
54 #include "gcc-generate-rtl-pass.h"
55 
56 #if BUILDING_GCC_VERSION >= 9000
57 static bool no(void)
58 {
59 	return false;
60 }
61 
62 static void arm_pertask_ssp_start_unit(void *gcc_data, void *user_data)
63 {
64 	targetm.have_stack_protect_combined_set = no;
65 	targetm.have_stack_protect_combined_test = no;
66 }
67 #endif
68 
69 __visible int plugin_init(struct plugin_name_args *plugin_info,
70 			  struct plugin_gcc_version *version)
71 {
72 	const char * const plugin_name = plugin_info->base_name;
73 	const int argc = plugin_info->argc;
74 	const struct plugin_argument *argv = plugin_info->argv;
75 	int tso = 0;
76 	int i;
77 
78 	if (!plugin_default_version_check(version, &gcc_version)) {
79 		error(G_("incompatible gcc/plugin versions"));
80 		return 1;
81 	}
82 
83 	for (i = 0; i < argc; ++i) {
84 		if (!strcmp(argv[i].key, "disable"))
85 			return 0;
86 
87 		/* all remaining options require a value */
88 		if (!argv[i].value) {
89 			error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
90 			      plugin_name, argv[i].key);
91 			return 1;
92 		}
93 
94 		if (!strcmp(argv[i].key, "tso")) {
95 			tso = atoi(argv[i].value);
96 			continue;
97 		}
98 
99 		if (!strcmp(argv[i].key, "offset")) {
100 			canary_offset = atoi(argv[i].value);
101 			continue;
102 		}
103 		error(G_("unknown option '-fplugin-arg-%s-%s'"),
104 		      plugin_name, argv[i].key);
105 		return 1;
106 	}
107 
108 	/* create the mask that produces the base of the stack */
109 	sp_mask = ~((1U << (12 + tso)) - 1);
110 
111 	PASS_INFO(arm_pertask_ssp_rtl, "expand", 1, PASS_POS_INSERT_AFTER);
112 
113 	register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP,
114 			  NULL, &arm_pertask_ssp_rtl_pass_info);
115 
116 #if BUILDING_GCC_VERSION >= 9000
117 	register_callback(plugin_info->base_name, PLUGIN_START_UNIT,
118 			  arm_pertask_ssp_start_unit, NULL);
119 #endif
120 
121 	return 0;
122 }
123