tools/objtool/orc_gen.c

   1 /*
   2  * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include <stdlib.h>
  19 #include <string.h>
  20
  21 #include "orc.h"
  22 #include "check.h"
  23 #include "warn.h"
  24
  25 int create_orc(struct objtool_file *file)
  26 {
  27         struct instruction *insn;
  28
  29         for_each_insn(file, insn) {
  30                 struct orc_entry *orc = &insn->orc;
  31                 struct cfi_reg *cfa = &insn->state.cfa;
  32                 struct cfi_reg *bp = &insn->state.regs[CFI_BP];
  33
  34                 if (cfa->base == CFI_UNDEFINED) {
  35                         orc->sp_reg = ORC_REG_UNDEFINED;
  36                         continue;
  37                 }
  38
  39                 switch (cfa->base) {
  40                 case CFI_SP:
  41                         orc->sp_reg = ORC_REG_SP;
  42                         break;
  43                 case CFI_SP_INDIRECT:
  44                         orc->sp_reg = ORC_REG_SP_INDIRECT;
  45                         break;
  46                 case CFI_BP:
  47                         orc->sp_reg = ORC_REG_BP;
  48                         break;
  49                 case CFI_BP_INDIRECT:
  50                         orc->sp_reg = ORC_REG_BP_INDIRECT;
  51                         break;
  52                 case CFI_R10:
  53                         orc->sp_reg = ORC_REG_R10;
  54                         break;
  55                 case CFI_R13:
  56                         orc->sp_reg = ORC_REG_R13;
  57                         break;
  58                 case CFI_DI:
  59                         orc->sp_reg = ORC_REG_DI;
  60                         break;
  61                 case CFI_DX:
  62                         orc->sp_reg = ORC_REG_DX;
  63                         break;
  64                 default:
  65                         WARN_FUNC("unknown CFA base reg %d",
  66                                   insn->sec, insn->offset, cfa->base);
  67                         return -1;
  68                 }
  69
  70                 switch(bp->base) {
  71                 case CFI_UNDEFINED:
  72                         orc->bp_reg = ORC_REG_UNDEFINED;
  73                         break;
  74                 case CFI_CFA:
  75                         orc->bp_reg = ORC_REG_PREV_SP;
  76                         break;
  77                 case CFI_BP:
  78                         orc->bp_reg = ORC_REG_BP;
  79                         break;
  80                 default:
  81                         WARN_FUNC("unknown BP base reg %d",
  82                                   insn->sec, insn->offset, bp->base);
  83                         return -1;
  84                 }
  85
  86                 orc->sp_offset = cfa->offset;
  87                 orc->bp_offset = bp->offset;
  88                 orc->type = insn->state.type;
  89         }
  90
  91         return 0;
  92 }
  93
  94 static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,
  95                                 unsigned int idx, struct section *insn_sec,
  96                                 unsigned long insn_off, struct orc_entry *o)
  97 {
  98         struct orc_entry *orc;
  99         struct rela *rela;
 100
 101         /* populate ORC data */
 102         orc = (struct orc_entry *)u_sec->data->d_buf + idx;
 103         memcpy(orc, o, sizeof(*orc));
 104
 105         /* populate rela for ip */
 106         rela = malloc(sizeof(*rela));
 107         if (!rela) {
 108                 perror("malloc");
 109                 return -1;
 110         }
 111         memset(rela, 0, sizeof(*rela));
 112
 113         if (insn_sec->sym) {
 114                 rela->sym = insn_sec->sym;
 115                 rela->addend = insn_off;
 116         } else {
 117                 /*
 118                  * The Clang assembler doesn't produce section symbols, so we
 119                  * have to reference the function symbol instead:
 120                  */
 121                 rela->sym = find_symbol_containing(insn_sec, insn_off);
 122                 if (!rela->sym) {
 123                         /*
 124                          * Hack alert.  This happens when we need to reference
 125                          * the NOP pad insn immediately after the function.
 126                          */
 127                         rela->sym = find_symbol_containing(insn_sec,
 128                                                            insn_off - 1);
 129                 }
 130                 if (!rela->sym) {
 131                         WARN("missing symbol for insn at offset 0x%lx\n",
 132                              insn_off);
 133                         return -1;
 134                 }
 135
 136                 rela->addend = insn_off - rela->sym->offset;
 137         }
 138
 139         rela->type = R_X86_64_PC32;
 140         rela->offset = idx * sizeof(int);
 141
 142         list_add_tail(&rela->list, &ip_relasec->rela_list);
 143         hash_add(ip_relasec->rela_hash, &rela->hash, rela->offset);
 144
 145         return 0;
 146 }
 147
 148 int create_orc_sections(struct objtool_file *file)
 149 {
 150         struct instruction *insn, *prev_insn;
 151         struct section *sec, *u_sec, *ip_relasec;
 152         unsigned int idx;
 153
 154         struct orc_entry empty = {
 155                 .sp_reg = ORC_REG_UNDEFINED,
 156                 .bp_reg  = ORC_REG_UNDEFINED,
 157                 .type    = ORC_TYPE_CALL,
 158         };
 159
 160         sec = find_section_by_name(file->elf, ".orc_unwind");
 161         if (sec) {
 162                 WARN("file already has .orc_unwind section, skipping");
 163                 return -1;
 164         }
 165
 166         /* count the number of needed orcs */
 167         idx = 0;
 168         for_each_sec(file, sec) {
 169                 if (!sec->text)
 170                         continue;
 171
 172                 prev_insn = NULL;
 173                 sec_for_each_insn(file, sec, insn) {
 174                         if (!prev_insn ||
 175                             memcmp(&insn->orc, &prev_insn->orc,
 176                                    sizeof(struct orc_entry))) {
 177                                 idx++;
 178                         }
 179                         prev_insn = insn;
 180                 }
 181
 182                 /* section terminator */
 183                 if (prev_insn)
 184                         idx++;
 185         }
 186         if (!idx)
 187                 return -1;
 188
 189
 190         /* create .orc_unwind_ip and .rela.orc_unwind_ip sections */
 191         sec = elf_create_section(file->elf, ".orc_unwind_ip", sizeof(int), idx);
 192         if (!sec)
 193                 return -1;
 194
 195         ip_relasec = elf_create_rela_section(file->elf, sec);
 196         if (!ip_relasec)
 197                 return -1;
 198
 199         /* create .orc_unwind section */
 200         u_sec = elf_create_section(file->elf, ".orc_unwind",
 201                                    sizeof(struct orc_entry), idx);
 202
 203         /* populate sections */
 204         idx = 0;
 205         for_each_sec(file, sec) {
 206                 if (!sec->text)
 207                         continue;
 208
 209                 prev_insn = NULL;
 210                 sec_for_each_insn(file, sec, insn) {
 211                         if (!prev_insn || memcmp(&insn->orc, &prev_insn->orc,
 212                                                  sizeof(struct orc_entry))) {
 213
 214                                 if (create_orc_entry(u_sec, ip_relasec, idx,
 215                                                      insn->sec, insn->offset,
 216                                                      &insn->orc))
 217                                         return -1;
 218
 219                                 idx++;
 220                         }
 221                         prev_insn = insn;
 222                 }
 223
 224                 /* section terminator */
 225                 if (prev_insn) {
 226                         if (create_orc_entry(u_sec, ip_relasec, idx,
 227                                              prev_insn->sec,
 228                                              prev_insn->offset + prev_insn->len,
 229                                              &empty))
 230                                 return -1;
 231
 232                         idx++;
 233                 }
 234         }
 235
 236         if (elf_rebuild_rela_section(ip_relasec))
 237                 return -1;
 238
 239         return 0;
 240 }