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