orc_gen.c

  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/orc.h>
 14#include <objtool/warn.h>
 15
 16struct orc_list_entry {
 17	struct list_head list;
 18	struct orc_entry orc;
 19	struct section *insn_sec;
 20	unsigned long insn_off;
 21};
 22
 23static int orc_list_add(struct list_head *orc_list, struct orc_entry *orc,
 24			struct section *sec, unsigned long offset)
 25{
 26	struct orc_list_entry *entry = malloc(sizeof(*entry));
 27
 28	if (!entry) {
 29		WARN("malloc failed");
 30		return -1;
 31	}
 32
 33	entry->orc	= *orc;
 34	entry->insn_sec = sec;
 35	entry->insn_off = offset;
 36
 37	list_add_tail(&entry->list, orc_list);
 38	return 0;
 39}
 40
 41static unsigned long alt_group_len(struct alt_group *alt_group)
 42{
 43	return alt_group->last_insn->offset +
 44	       alt_group->last_insn->len -
 45	       alt_group->first_insn->offset;
 46}
 47
 48int orc_create(struct objtool_file *file)
 49{
 50	struct section *sec, *orc_sec;
 51	unsigned int nr = 0, idx = 0;
 52	struct orc_list_entry *entry;
 53	struct list_head orc_list;
 54
 55	struct orc_entry null = { .type = ORC_TYPE_UNDEFINED };
 56
 57	/* Build a deduplicated list of ORC entries: */
 58	INIT_LIST_HEAD(&orc_list);
 59	for_each_sec(file->elf, sec) {
 60		struct orc_entry orc, prev_orc = {0};
 61		struct instruction *insn;
 62		bool empty = true;
 63
 64		if (!sec->text)
 65			continue;
 66
 67		sec_for_each_insn(file, sec, insn) {
 68			struct alt_group *alt_group = insn->alt_group;
 69			int i;
 70
 71			if (!alt_group) {
 72				if (init_orc_entry(&orc, insn->cfi, insn))
 73					return -1;
 74				if (!memcmp(&prev_orc, &orc, sizeof(orc)))
 75					continue;
 76				if (orc_list_add(&orc_list, &orc, sec,
 77						 insn->offset))
 78					return -1;
 79				nr++;
 80				prev_orc = orc;
 81				empty = false;
 82				continue;
 83			}
 84
 85			/*
 86			 * Alternatives can have different stack layout
 87			 * possibilities (but they shouldn't conflict).
 88			 * Instead of traversing the instructions, use the
 89			 * alt_group's flattened byte-offset-addressed CFI
 90			 * array.
 91			 */
 92			for (i = 0; i < alt_group_len(alt_group); i++) {
 93				struct cfi_state *cfi = alt_group->cfi[i];
 94				if (!cfi)
 95					continue;
 96				/* errors are reported on the original insn */
 97				if (init_orc_entry(&orc, cfi, insn))
 98					return -1;
 99				if (!memcmp(&prev_orc, &orc, sizeof(orc)))
100					continue;
101				if (orc_list_add(&orc_list, &orc, insn->sec,
102						 insn->offset + i))
103					return -1;
104				nr++;
105				prev_orc = orc;
106				empty = false;
107			}
108
109			/* Skip to the end of the alt_group */
110			insn = alt_group->last_insn;
111		}
112
113		/* Add a section terminator */
114		if (!empty) {
115			orc_list_add(&orc_list, &null, sec, sec->sh.sh_size);
116			nr++;
117		}
118	}
119	if (!nr)
120		return 0;
121
122	/* Create .orc_unwind, .orc_unwind_ip and .rela.orc_unwind_ip sections: */
123	sec = find_section_by_name(file->elf, ".orc_unwind");
124	if (sec) {
125		WARN("file already has .orc_unwind section, skipping");
126		return -1;
127	}
128	orc_sec = elf_create_section(file->elf, ".orc_unwind",
129				     nr * sizeof(struct orc_entry),
130				     sizeof(struct orc_entry),
131				     SHT_PROGBITS,
132				     1,
133				     SHF_ALLOC);
134	if (!orc_sec)
135		return -1;
136
137	sec = elf_create_section_pair(file->elf, ".orc_unwind_ip", sizeof(int), nr, nr);
138	if (!sec)
139		return -1;
140
141	/* Write ORC entries to sections: */
142	list_for_each_entry(entry, &orc_list, list) {
143		if (write_orc_entry(file->elf, orc_sec, sec, idx++,
144				    entry->insn_sec, entry->insn_off,
145				    &entry->orc))
146			return -1;
147	}
148
149	return 0;
150}