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.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 		orc->end = 0;
25 		orc->sp_reg = ORC_REG_UNDEFINED;
26 		return 0;
27 	}
28 
29 	orc->end = cfi->end;
30 
31 	if (cfi->cfa.base == CFI_UNDEFINED) {
32 		orc->sp_reg = ORC_REG_UNDEFINED;
33 		return 0;
34 	}
35 
36 	switch (cfi->cfa.base) {
37 	case CFI_SP:
38 		orc->sp_reg = ORC_REG_SP;
39 		break;
40 	case CFI_SP_INDIRECT:
41 		orc->sp_reg = ORC_REG_SP_INDIRECT;
42 		break;
43 	case CFI_BP:
44 		orc->sp_reg = ORC_REG_BP;
45 		break;
46 	case CFI_BP_INDIRECT:
47 		orc->sp_reg = ORC_REG_BP_INDIRECT;
48 		break;
49 	case CFI_R10:
50 		orc->sp_reg = ORC_REG_R10;
51 		break;
52 	case CFI_R13:
53 		orc->sp_reg = ORC_REG_R13;
54 		break;
55 	case CFI_DI:
56 		orc->sp_reg = ORC_REG_DI;
57 		break;
58 	case CFI_DX:
59 		orc->sp_reg = ORC_REG_DX;
60 		break;
61 	default:
62 		WARN_FUNC("unknown CFA base reg %d",
63 			  insn->sec, insn->offset, cfi->cfa.base);
64 		return -1;
65 	}
66 
67 	switch (bp->base) {
68 	case CFI_UNDEFINED:
69 		orc->bp_reg = ORC_REG_UNDEFINED;
70 		break;
71 	case CFI_CFA:
72 		orc->bp_reg = ORC_REG_PREV_SP;
73 		break;
74 	case CFI_BP:
75 		orc->bp_reg = ORC_REG_BP;
76 		break;
77 	default:
78 		WARN_FUNC("unknown BP base reg %d",
79 			  insn->sec, insn->offset, bp->base);
80 		return -1;
81 	}
82 
83 	orc->sp_offset = cfi->cfa.offset;
84 	orc->bp_offset = bp->offset;
85 	orc->type = cfi->type;
86 
87 	return 0;
88 }
89 
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)90 static int write_orc_entry(struct elf *elf, struct section *orc_sec,
91 			   struct section *ip_sec, unsigned int idx,
92 			   struct section *insn_sec, unsigned long insn_off,
93 			   struct orc_entry *o)
94 {
95 	struct orc_entry *orc;
96 
97 	/* populate ORC data */
98 	orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
99 	memcpy(orc, o, sizeof(*orc));
100 	orc->sp_offset = bswap_if_needed(orc->sp_offset);
101 	orc->bp_offset = bswap_if_needed(orc->bp_offset);
102 
103 	/* populate reloc for ip */
104 	if (elf_add_reloc_to_insn(elf, ip_sec, idx * sizeof(int), R_X86_64_PC32,
105 				  insn_sec, insn_off))
106 		return -1;
107 
108 	return 0;
109 }
110 
111 struct orc_list_entry {
112 	struct list_head list;
113 	struct orc_entry orc;
114 	struct section *insn_sec;
115 	unsigned long insn_off;
116 };
117 
orc_list_add(struct list_head * orc_list,struct orc_entry * orc,struct section * sec,unsigned long offset)118 static int orc_list_add(struct list_head *orc_list, struct orc_entry *orc,
119 			struct section *sec, unsigned long offset)
120 {
121 	struct orc_list_entry *entry = malloc(sizeof(*entry));
122 
123 	if (!entry) {
124 		WARN("malloc failed");
125 		return -1;
126 	}
127 
128 	entry->orc	= *orc;
129 	entry->insn_sec = sec;
130 	entry->insn_off = offset;
131 
132 	list_add_tail(&entry->list, orc_list);
133 	return 0;
134 }
135 
alt_group_len(struct alt_group * alt_group)136 static unsigned long alt_group_len(struct alt_group *alt_group)
137 {
138 	return alt_group->last_insn->offset +
139 	       alt_group->last_insn->len -
140 	       alt_group->first_insn->offset;
141 }
142 
orc_create(struct objtool_file * file)143 int orc_create(struct objtool_file *file)
144 {
145 	struct section *sec, *orc_sec;
146 	unsigned int nr = 0, idx = 0;
147 	struct orc_list_entry *entry;
148 	struct list_head orc_list;
149 
150 	struct orc_entry null = {
151 		.sp_reg  = ORC_REG_UNDEFINED,
152 		.bp_reg  = ORC_REG_UNDEFINED,
153 		.type    = UNWIND_HINT_TYPE_CALL,
154 	};
155 
156 	/* Build a deduplicated list of ORC entries: */
157 	INIT_LIST_HEAD(&orc_list);
158 	for_each_sec(file, sec) {
159 		struct orc_entry orc, prev_orc = {0};
160 		struct instruction *insn;
161 		bool empty = true;
162 
163 		if (!sec->text)
164 			continue;
165 
166 		sec_for_each_insn(file, sec, insn) {
167 			struct alt_group *alt_group = insn->alt_group;
168 			int i;
169 
170 			if (!alt_group) {
171 				if (init_orc_entry(&orc, insn->cfi, insn))
172 					return -1;
173 				if (!memcmp(&prev_orc, &orc, sizeof(orc)))
174 					continue;
175 				if (orc_list_add(&orc_list, &orc, sec,
176 						 insn->offset))
177 					return -1;
178 				nr++;
179 				prev_orc = orc;
180 				empty = false;
181 				continue;
182 			}
183 
184 			/*
185 			 * Alternatives can have different stack layout
186 			 * possibilities (but they shouldn't conflict).
187 			 * Instead of traversing the instructions, use the
188 			 * alt_group's flattened byte-offset-addressed CFI
189 			 * array.
190 			 */
191 			for (i = 0; i < alt_group_len(alt_group); i++) {
192 				struct cfi_state *cfi = alt_group->cfi[i];
193 				if (!cfi)
194 					continue;
195 				/* errors are reported on the original insn */
196 				if (init_orc_entry(&orc, cfi, insn))
197 					return -1;
198 				if (!memcmp(&prev_orc, &orc, sizeof(orc)))
199 					continue;
200 				if (orc_list_add(&orc_list, &orc, insn->sec,
201 						 insn->offset + i))
202 					return -1;
203 				nr++;
204 				prev_orc = orc;
205 				empty = false;
206 			}
207 
208 			/* Skip to the end of the alt_group */
209 			insn = alt_group->last_insn;
210 		}
211 
212 		/* Add a section terminator */
213 		if (!empty) {
214 			orc_list_add(&orc_list, &null, sec, sec->sh.sh_size);
215 			nr++;
216 		}
217 	}
218 	if (!nr)
219 		return 0;
220 
221 	/* Create .orc_unwind, .orc_unwind_ip and .rela.orc_unwind_ip sections: */
222 	sec = find_section_by_name(file->elf, ".orc_unwind");
223 	if (sec) {
224 		WARN("file already has .orc_unwind section, skipping");
225 		return -1;
226 	}
227 	orc_sec = elf_create_section(file->elf, ".orc_unwind", 0,
228 				     sizeof(struct orc_entry), nr);
229 	if (!orc_sec)
230 		return -1;
231 
232 	sec = elf_create_section(file->elf, ".orc_unwind_ip", 0, sizeof(int), nr);
233 	if (!sec)
234 		return -1;
235 
236 	/* Write ORC entries to sections: */
237 	list_for_each_entry(entry, &orc_list, list) {
238 		if (write_orc_entry(file->elf, orc_sec, sec, idx++,
239 				    entry->insn_sec, entry->insn_off,
240 				    &entry->orc))
241 			return -1;
242 	}
243 
244 	return 0;
245 }
246