xref: /openbmc/linux/tools/objtool/orc_gen.c (revision 6342a20e)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
4  */
5 
6 #include <stdlib.h>
7 #include <string.h>
8 
9 #include <linux/objtool_types.h>
10 #include <asm/orc_types.h>
11 
12 #include <objtool/check.h>
13 #include <objtool/warn.h>
14 #include <objtool/endianness.h>
15 
init_orc_entry(struct orc_entry * orc,struct cfi_state * cfi,struct instruction * insn)16 static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
17 			  struct instruction *insn)
18 {
19 	struct cfi_reg *bp = &cfi->regs[CFI_BP];
20 
21 	memset(orc, 0, sizeof(*orc));
22 
23 	if (!cfi) {
24 		/*
25 		 * This is usually either unreachable nops/traps (which don't
26 		 * trigger unreachable instruction warnings), or
27 		 * STACK_FRAME_NON_STANDARD functions.
28 		 */
29 		orc->type = ORC_TYPE_UNDEFINED;
30 		return 0;
31 	}
32 
33 	switch (cfi->type) {
34 	case UNWIND_HINT_TYPE_UNDEFINED:
35 		orc->type = ORC_TYPE_UNDEFINED;
36 		return 0;
37 	case UNWIND_HINT_TYPE_END_OF_STACK:
38 		orc->type = ORC_TYPE_END_OF_STACK;
39 		return 0;
40 	case UNWIND_HINT_TYPE_CALL:
41 		orc->type = ORC_TYPE_CALL;
42 		break;
43 	case UNWIND_HINT_TYPE_REGS:
44 		orc->type = ORC_TYPE_REGS;
45 		break;
46 	case UNWIND_HINT_TYPE_REGS_PARTIAL:
47 		orc->type = ORC_TYPE_REGS_PARTIAL;
48 		break;
49 	default:
50 		WARN_INSN(insn, "unknown unwind hint type %d", cfi->type);
51 		return -1;
52 	}
53 
54 	orc->signal = cfi->signal;
55 
56 	switch (cfi->cfa.base) {
57 	case CFI_SP:
58 		orc->sp_reg = ORC_REG_SP;
59 		break;
60 	case CFI_SP_INDIRECT:
61 		orc->sp_reg = ORC_REG_SP_INDIRECT;
62 		break;
63 	case CFI_BP:
64 		orc->sp_reg = ORC_REG_BP;
65 		break;
66 	case CFI_BP_INDIRECT:
67 		orc->sp_reg = ORC_REG_BP_INDIRECT;
68 		break;
69 	case CFI_R10:
70 		orc->sp_reg = ORC_REG_R10;
71 		break;
72 	case CFI_R13:
73 		orc->sp_reg = ORC_REG_R13;
74 		break;
75 	case CFI_DI:
76 		orc->sp_reg = ORC_REG_DI;
77 		break;
78 	case CFI_DX:
79 		orc->sp_reg = ORC_REG_DX;
80 		break;
81 	default:
82 		WARN_INSN(insn, "unknown CFA base reg %d", cfi->cfa.base);
83 		return -1;
84 	}
85 
86 	switch (bp->base) {
87 	case CFI_UNDEFINED:
88 		orc->bp_reg = ORC_REG_UNDEFINED;
89 		break;
90 	case CFI_CFA:
91 		orc->bp_reg = ORC_REG_PREV_SP;
92 		break;
93 	case CFI_BP:
94 		orc->bp_reg = ORC_REG_BP;
95 		break;
96 	default:
97 		WARN_INSN(insn, "unknown BP base reg %d", bp->base);
98 		return -1;
99 	}
100 
101 	orc->sp_offset = cfi->cfa.offset;
102 	orc->bp_offset = bp->offset;
103 
104 	return 0;
105 }
106 
write_orc_entry(struct elf * elf,struct section * orc_sec,struct section * ip_sec,unsigned int idx,struct section * insn_sec,unsigned long insn_off,struct orc_entry * o)107 static int write_orc_entry(struct elf *elf, struct section *orc_sec,
108 			   struct section *ip_sec, unsigned int idx,
109 			   struct section *insn_sec, unsigned long insn_off,
110 			   struct orc_entry *o)
111 {
112 	struct orc_entry *orc;
113 
114 	/* populate ORC data */
115 	orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
116 	memcpy(orc, o, sizeof(*orc));
117 	orc->sp_offset = bswap_if_needed(elf, orc->sp_offset);
118 	orc->bp_offset = bswap_if_needed(elf, orc->bp_offset);
119 
120 	/* populate reloc for ip */
121 	if (!elf_init_reloc_text_sym(elf, ip_sec, idx * sizeof(int), idx,
122 				     insn_sec, insn_off))
123 		return -1;
124 
125 	return 0;
126 }
127 
128 struct orc_list_entry {
129 	struct list_head list;
130 	struct orc_entry orc;
131 	struct section *insn_sec;
132 	unsigned long insn_off;
133 };
134 
orc_list_add(struct list_head * orc_list,struct orc_entry * orc,struct section * sec,unsigned long offset)135 static int orc_list_add(struct list_head *orc_list, struct orc_entry *orc,
136 			struct section *sec, unsigned long offset)
137 {
138 	struct orc_list_entry *entry = malloc(sizeof(*entry));
139 
140 	if (!entry) {
141 		WARN("malloc failed");
142 		return -1;
143 	}
144 
145 	entry->orc	= *orc;
146 	entry->insn_sec = sec;
147 	entry->insn_off = offset;
148 
149 	list_add_tail(&entry->list, orc_list);
150 	return 0;
151 }
152 
alt_group_len(struct alt_group * alt_group)153 static unsigned long alt_group_len(struct alt_group *alt_group)
154 {
155 	return alt_group->last_insn->offset +
156 	       alt_group->last_insn->len -
157 	       alt_group->first_insn->offset;
158 }
159 
orc_create(struct objtool_file * file)160 int orc_create(struct objtool_file *file)
161 {
162 	struct section *sec, *orc_sec;
163 	unsigned int nr = 0, idx = 0;
164 	struct orc_list_entry *entry;
165 	struct list_head orc_list;
166 
167 	struct orc_entry null = { .type = ORC_TYPE_UNDEFINED };
168 
169 	/* Build a deduplicated list of ORC entries: */
170 	INIT_LIST_HEAD(&orc_list);
171 	for_each_sec(file, sec) {
172 		struct orc_entry orc, prev_orc = {0};
173 		struct instruction *insn;
174 		bool empty = true;
175 
176 		if (!sec->text)
177 			continue;
178 
179 		sec_for_each_insn(file, sec, insn) {
180 			struct alt_group *alt_group = insn->alt_group;
181 			int i;
182 
183 			if (!alt_group) {
184 				if (init_orc_entry(&orc, insn->cfi, insn))
185 					return -1;
186 				if (!memcmp(&prev_orc, &orc, sizeof(orc)))
187 					continue;
188 				if (orc_list_add(&orc_list, &orc, sec,
189 						 insn->offset))
190 					return -1;
191 				nr++;
192 				prev_orc = orc;
193 				empty = false;
194 				continue;
195 			}
196 
197 			/*
198 			 * Alternatives can have different stack layout
199 			 * possibilities (but they shouldn't conflict).
200 			 * Instead of traversing the instructions, use the
201 			 * alt_group's flattened byte-offset-addressed CFI
202 			 * array.
203 			 */
204 			for (i = 0; i < alt_group_len(alt_group); i++) {
205 				struct cfi_state *cfi = alt_group->cfi[i];
206 				if (!cfi)
207 					continue;
208 				/* errors are reported on the original insn */
209 				if (init_orc_entry(&orc, cfi, insn))
210 					return -1;
211 				if (!memcmp(&prev_orc, &orc, sizeof(orc)))
212 					continue;
213 				if (orc_list_add(&orc_list, &orc, insn->sec,
214 						 insn->offset + i))
215 					return -1;
216 				nr++;
217 				prev_orc = orc;
218 				empty = false;
219 			}
220 
221 			/* Skip to the end of the alt_group */
222 			insn = alt_group->last_insn;
223 		}
224 
225 		/* Add a section terminator */
226 		if (!empty) {
227 			orc_list_add(&orc_list, &null, sec, sec->sh.sh_size);
228 			nr++;
229 		}
230 	}
231 	if (!nr)
232 		return 0;
233 
234 	/* Create .orc_unwind, .orc_unwind_ip and .rela.orc_unwind_ip sections: */
235 	sec = find_section_by_name(file->elf, ".orc_unwind");
236 	if (sec) {
237 		WARN("file already has .orc_unwind section, skipping");
238 		return -1;
239 	}
240 	orc_sec = elf_create_section(file->elf, ".orc_unwind",
241 				     sizeof(struct orc_entry), nr);
242 	if (!orc_sec)
243 		return -1;
244 
245 	sec = elf_create_section_pair(file->elf, ".orc_unwind_ip", sizeof(int), nr, nr);
246 	if (!sec)
247 		return -1;
248 
249 	/* Write ORC entries to sections: */
250 	list_for_each_entry(entry, &orc_list, list) {
251 		if (write_orc_entry(file->elf, orc_sec, sec, idx++,
252 				    entry->insn_sec, entry->insn_off,
253 				    &entry->orc))
254 			return -1;
255 	}
256 
257 	return 0;
258 }
259