| 1 | |
| 2 | * Copyright (C) 2015-2017 Josh Poimboeuf <[email protected]>
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| 3 | *
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| 4 | * This program is free software; you can redistribute it and/or
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| 5 | * modify it under the terms of the GNU General Public License
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| 6 | * as published by the Free Software Foundation; either version 2
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| 7 | * of the License, or (at your option) any later version.
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| 8 | *
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| 9 | * This program is distributed in the hope that it will be useful,
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| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 12 | * GNU General Public License for more details.
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| 13 | *
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| 14 | * You should have received a copy of the GNU General Public License
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| 15 | * along with this program; if not, see <http://www.gnu.org/licenses/>.
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| 16 |
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| 17 |
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| 18 | #include <string.h>
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| 19 | #include <stdlib.h>
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| 20 |
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| 21 | #include "check.h"
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| 22 | #include "elf.h"
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| 23 | #include "special.h"
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| 24 | #include "arch.h"
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| 25 | #include "warn.h"
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| 26 |
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| 27 | #include <linux/hashtable.h>
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| 28 | #include <linux/kernel.h>
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| 29 |
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| 30 | struct alternative {
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| 31 | struct list_head list;
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| 32 | struct instruction *insn;
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| 33 | };
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| 34 |
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| 35 | const char *objname;
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| 36 | static bool nofp;
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| 37 | struct cfi_state initial_func_cfi;
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| 38 |
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| 39 | static struct instruction *find_insn(struct objtool_file *file,
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| 40 | struct section *sec, unsigned long offset)
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| 41 | {
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| 42 | struct instruction *insn;
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| 43 |
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| 44 | hash_for_each_possible(file->insn_hash, insn, hash, offset)
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| 45 | if (insn->sec == sec && insn->offset == offset)
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| 46 | return insn;
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| 47 |
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| 48 | return NULL;
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| 49 | }
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| 50 |
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| 51 | static struct instruction *next_insn_same_sec(struct objtool_file *file,
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| 52 | struct instruction *insn)
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| 53 | {
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| 54 | struct instruction *next = list_next_entry(insn, list);
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| 55 |
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| 56 | if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
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| 57 | return NULL;
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| 58 |
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| 59 | return next;
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| 60 | }
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| 61 |
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| 62 | static bool gcov_enabled(struct objtool_file *file)
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| 63 | {
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| 64 | struct section *sec;
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| 65 | struct symbol *sym;
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| 66 |
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| 67 | for_each_sec(file, sec)
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| 68 | list_for_each_entry(sym, &sec->symbol_list, list)
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| 69 | if (!strncmp(sym->name, "__gcov_.", 8))
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| 70 | return true;
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| 71 |
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| 72 | return false;
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| 73 | }
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| 74 |
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| 75 | #define func_for_each_insn(file, func, insn) \
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| 76 | for (insn = find_insn(file, func->sec, func->offset); \
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| 77 | insn && &insn->list != &file->insn_list && \
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| 78 | insn->sec == func->sec && \
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| 79 | insn->offset < func->offset + func->len; \
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| 80 | insn = list_next_entry(insn, list))
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| 81 |
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| 82 | #define func_for_each_insn_continue_reverse(file, func, insn) \
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| 83 | for (insn = list_prev_entry(insn, list); \
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| 84 | &insn->list != &file->insn_list && \
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| 85 | insn->sec == func->sec && insn->offset >= func->offset; \
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| 86 | insn = list_prev_entry(insn, list))
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| 87 |
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| 88 | #define sec_for_each_insn_from(file, insn) \
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| 89 | for (; insn; insn = next_insn_same_sec(file, insn))
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| 90 |
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| 91 | #define sec_for_each_insn_continue(file, insn) \
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| 92 | for (insn = next_insn_same_sec(file, insn); insn; \
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| 93 | insn = next_insn_same_sec(file, insn))
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| 94 |
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| 95 | |
| 96 | * Check if the function has been manually whitelisted with the
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| 97 | * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
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| 98 | * due to its use of a context switching instruction.
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| 99 |
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| 100 | static bool ignore_func(struct objtool_file *file, struct symbol *func)
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| 101 | {
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| 102 | struct rela *rela;
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| 103 | struct instruction *insn;
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| 104 |
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| 105 |
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| 106 | if (file->whitelist && file->whitelist->rela)
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| 107 | list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
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| 108 | if (rela->sym->type == STT_SECTION &&
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| 109 | rela->sym->sec == func->sec &&
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| 110 | rela->addend == func->offset)
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| 111 | return true;
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| 112 | if (rela->sym->type == STT_FUNC && rela->sym == func)
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| 113 | return true;
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| 114 | }
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| 115 |
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| 116 |
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| 117 | func_for_each_insn(file, func, insn)
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| 118 | if (insn->type == INSN_CONTEXT_SWITCH)
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| 119 | return true;
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| 120 |
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| 121 | return false;
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| 122 | }
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| 123 |
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| 124 | |
| 125 | * This checks to see if the given function is a "noreturn" function.
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| 126 | *
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| 127 | * For global functions which are outside the scope of this object file, we
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| 128 | * have to keep a manual list of them.
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| 129 | *
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| 130 | * For local functions, we have to detect them manually by simply looking for
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| 131 | * the lack of a return instruction.
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| 132 | *
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| 133 | * Returns:
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| 134 | * -1: error
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| 135 | * 0: no dead end
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| 136 | * 1: dead end
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| 137 |
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| 138 | static int __dead_end_function(struct objtool_file *file, struct symbol *func,
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| 139 | int recursion)
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| 140 | {
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| 141 | int i;
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| 142 | struct instruction *insn;
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| 143 | bool empty = true;
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| 144 |
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| 145 | |
| 146 | * Unfortunately these have to be hard coded because the noreturn
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| 147 | * attribute isn't provided in ELF data.
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| 148 |
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| 149 | static const char * const global_noreturns[] = {
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| 150 | "__stack_chk_fail",
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| 151 | "panic",
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| 152 | "do_exit",
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| 153 | "do_task_dead",
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| 154 | "__module_put_and_exit",
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| 155 | "complete_and_exit",
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| 156 | "kvm_spurious_fault",
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| 157 | "__reiserfs_panic",
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| 158 | "lbug_with_loc",
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| 159 | "fortify_panic",
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| 160 | };
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| 161 |
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| 162 | if (func->bind == STB_WEAK)
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| 163 | return 0;
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| 164 |
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| 165 | if (func->bind == STB_GLOBAL)
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| 166 | for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
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| 167 | if (!strcmp(func->name, global_noreturns[i]))
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| 168 | return 1;
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| 169 |
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| 170 | if (!func->sec)
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| 171 | return 0;
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| 172 |
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| 173 | func_for_each_insn(file, func, insn) {
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| 174 | empty = false;
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| 175 |
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| 176 | if (insn->type == INSN_RETURN)
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| 177 | return 0;
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| 178 | }
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| 179 |
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| 180 | if (empty)
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| 181 | return 0;
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| 182 |
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| 183 | |
| 184 | * A function can have a sibling call instead of a return. In that
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| 185 | * case, the function's dead-end status depends on whether the target
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| 186 | * of the sibling call returns.
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| 187 |
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| 188 | func_for_each_insn(file, func, insn) {
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| 189 | if (insn->sec != func->sec ||
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| 190 | insn->offset >= func->offset + func->len)
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| 191 | break;
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| 192 |
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| 193 | if (insn->type == INSN_JUMP_UNCONDITIONAL) {
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| 194 | struct instruction *dest = insn->jump_dest;
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| 195 | struct symbol *dest_func;
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| 196 |
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| 197 | if (!dest)
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| 198 |
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| 199 | return 0;
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| 200 |
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| 201 | if (dest->sec != func->sec ||
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| 202 | dest->offset < func->offset ||
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| 203 | dest->offset >= func->offset + func->len) {
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| 204 |
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| 205 | dest_func = find_symbol_by_offset(dest->sec,
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| 206 | dest->offset);
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| 207 | if (!dest_func)
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| 208 | continue;
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| 209 |
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| 210 | if (recursion == 5) {
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| 211 | WARN_FUNC("infinite recursion (objtool bug!)",
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| 212 | dest->sec, dest->offset);
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| 213 | return -1;
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| 214 | }
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| 215 |
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| 216 | return __dead_end_function(file, dest_func,
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| 217 | recursion + 1);
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| 218 | }
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| 219 | }
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| 220 |
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| 221 | if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
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| 222 |
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| 223 | return 0;
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| 224 | }
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| 225 |
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| 226 | return 1;
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| 227 | }
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| 228 |
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| 229 | static int dead_end_function(struct objtool_file *file, struct symbol *func)
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| 230 | {
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| 231 | return __dead_end_function(file, func, 0);
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| 232 | }
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| 233 |
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| 234 | static void clear_insn_state(struct insn_state *state)
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| 235 | {
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| 236 | int i;
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| 237 |
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| 238 | memset(state, 0, sizeof(*state));
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| 239 | state->cfa.base = CFI_UNDEFINED;
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| 240 | for (i = 0; i < CFI_NUM_REGS; i++)
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| 241 | state->regs[i].base = CFI_UNDEFINED;
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| 242 | state->drap_reg = CFI_UNDEFINED;
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| 243 | }
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| 244 |
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| 245 | |
| 246 | * Call the arch-specific instruction decoder for all the instructions and add
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| 247 | * them to the global instruction list.
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| 248 |
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| 249 | static int decode_instructions(struct objtool_file *file)
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| 250 | {
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| 251 | struct section *sec;
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| 252 | struct symbol *func;
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| 253 | unsigned long offset;
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| 254 | struct instruction *insn;
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| 255 | int ret;
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| 256 |
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| 257 | for_each_sec(file, sec) {
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| 258 |
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| 259 | if (!(sec->sh.sh_flags & SHF_EXECINSTR))
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| 260 | continue;
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| 261 |
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| 262 | for (offset = 0; offset < sec->len; offset += insn->len) {
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| 263 | insn = malloc(sizeof(*insn));
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| 264 | if (!insn) {
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| 265 | WARN("malloc failed");
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| 266 | return -1;
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| 267 | }
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| 268 | memset(insn, 0, sizeof(*insn));
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| 269 | INIT_LIST_HEAD(&insn->alts);
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| 270 | clear_insn_state(&insn->state);
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| 271 |
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| 272 | insn->sec = sec;
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| 273 | insn->offset = offset;
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| 274 |
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| 275 | ret = arch_decode_instruction(file->elf, sec, offset,
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| 276 | sec->len - offset,
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| 277 | &insn->len, &insn->type,
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| 278 | &insn->immediate,
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| 279 | &insn->stack_op);
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| 280 | if (ret)
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| 281 | return ret;
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| 282 |
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| 283 | if (!insn->type || insn->type > INSN_LAST) {
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| 284 | WARN_FUNC("invalid instruction type %d",
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| 285 | insn->sec, insn->offset, insn->type);
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| 286 | return -1;
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| 287 | }
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| 288 |
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| 289 | hash_add(file->insn_hash, &insn->hash, insn->offset);
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| 290 | list_add_tail(&insn->list, &file->insn_list);
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| 291 | }
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| 292 |
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| 293 | list_for_each_entry(func, &sec->symbol_list, list) {
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| 294 | if (func->type != STT_FUNC)
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| 295 | continue;
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| 296 |
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| 297 | if (!find_insn(file, sec, func->offset)) {
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| 298 | WARN("%s(): can't find starting instruction",
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| 299 | func->name);
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| 300 | return -1;
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| 301 | }
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| 302 |
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| 303 | func_for_each_insn(file, func, insn)
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| 304 | if (!insn->func)
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| 305 | insn->func = func;
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| 306 | }
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| 307 | }
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| 308 |
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| 309 | return 0;
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| 310 | }
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| 311 |
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| 312 | |
| 313 | * Find all uses of the unreachable() macro, which are code path dead ends.
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| 314 |
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| 315 | static int add_dead_ends(struct objtool_file *file)
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| 316 | {
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| 317 | struct section *sec;
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| 318 | struct rela *rela;
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| 319 | struct instruction *insn;
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| 320 | bool found;
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| 321 |
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| 322 | sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
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| 323 | if (!sec)
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| 324 | return 0;
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| 325 |
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| 326 | list_for_each_entry(rela, &sec->rela_list, list) {
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| 327 | if (rela->sym->type != STT_SECTION) {
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| 328 | WARN("unexpected relocation symbol type in %s", sec->name);
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| 329 | return -1;
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| 330 | }
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| 331 | insn = find_insn(file, rela->sym->sec, rela->addend);
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| 332 | if (insn)
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| 333 | insn = list_prev_entry(insn, list);
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| 334 | else if (rela->addend == rela->sym->sec->len) {
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| 335 | found = false;
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| 336 | list_for_each_entry_reverse(insn, &file->insn_list, list) {
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| 337 | if (insn->sec == rela->sym->sec) {
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| 338 | found = true;
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| 339 | break;
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| 340 | }
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| 341 | }
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| 342 |
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| 343 | if (!found) {
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| 344 | WARN("can't find unreachable insn at %s+0x%x",
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| 345 | rela->sym->sec->name, rela->addend);
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| 346 | return -1;
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| 347 | }
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| 348 | } else {
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| 349 | WARN("can't find unreachable insn at %s+0x%x",
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| 350 | rela->sym->sec->name, rela->addend);
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| 351 | return -1;
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| 352 | }
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| 353 |
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| 354 | insn->dead_end = true;
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| 355 | }
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| 356 |
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| 357 | return 0;
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| 358 | }
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| 359 |
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| 360 | |
| 361 | * Warnings shouldn't be reported for ignored functions.
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| 362 |
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| 363 | static void add_ignores(struct objtool_file *file)
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| 364 | {
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| 365 | struct instruction *insn;
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| 366 | struct section *sec;
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| 367 | struct symbol *func;
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| 368 |
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| 369 | for_each_sec(file, sec) {
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| 370 | list_for_each_entry(func, &sec->symbol_list, list) {
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| 371 | if (func->type != STT_FUNC)
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| 372 | continue;
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| 373 |
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| 374 | if (!ignore_func(file, func))
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| 375 | continue;
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| 376 |
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| 377 | func_for_each_insn(file, func, insn)
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| 378 | insn->ignore = true;
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| 379 | }
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| 380 | }
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| 381 | }
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| 382 |
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| 383 | |
| 384 | * Find the destination instructions for all jumps.
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| 385 |
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| 386 | static int add_jump_destinations(struct objtool_file *file)
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| 387 | {
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| 388 | struct instruction *insn;
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| 389 | struct rela *rela;
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| 390 | struct section *dest_sec;
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| 391 | unsigned long dest_off;
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| 392 |
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| 393 | for_each_insn(file, insn) {
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| 394 | if (insn->type != INSN_JUMP_CONDITIONAL &&
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| 395 | insn->type != INSN_JUMP_UNCONDITIONAL)
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| 396 | continue;
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| 397 |
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| 398 | if (insn->ignore)
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| 399 | continue;
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| 400 |
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| 401 | rela = find_rela_by_dest_range(insn->sec, insn->offset,
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| 402 | insn->len);
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| 403 | if (!rela) {
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| 404 | dest_sec = insn->sec;
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| 405 | dest_off = insn->offset + insn->len + insn->immediate;
|
| 406 | } else if (rela->sym->type == STT_SECTION) {
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| 407 | dest_sec = rela->sym->sec;
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| 408 | dest_off = rela->addend + 4;
|
| 409 | } else if (rela->sym->sec->idx) {
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| 410 | dest_sec = rela->sym->sec;
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| 411 | dest_off = rela->sym->sym.st_value + rela->addend + 4;
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| 412 | } else {
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| 413 |
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| 414 | insn->jump_dest = 0;
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| 415 | continue;
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| 416 | }
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| 417 |
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| 418 | insn->jump_dest = find_insn(file, dest_sec, dest_off);
|
| 419 | if (!insn->jump_dest) {
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| 420 |
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| 421 | |
| 422 | * This is a special case where an alt instruction
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| 423 | * jumps past the end of the section. These are
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| 424 | * handled later in handle_group_alt().
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| 425 |
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| 426 | if (!strcmp(insn->sec->name, ".altinstr_replacement"))
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| 427 | continue;
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| 428 |
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| 429 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
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| 430 | insn->sec, insn->offset, dest_sec->name,
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| 431 | dest_off);
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| 432 | return -1;
|
| 433 | }
|
| 434 | }
|
| 435 |
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| 436 | return 0;
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| 437 | }
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| 438 |
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| 439 | |
| 440 | * Find the destination instructions for all calls.
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| 441 |
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| 442 | static int add_call_destinations(struct objtool_file *file)
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| 443 | {
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| 444 | struct instruction *insn;
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| 445 | unsigned long dest_off;
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| 446 | struct rela *rela;
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| 447 |
|
| 448 | for_each_insn(file, insn) {
|
| 449 | if (insn->type != INSN_CALL)
|
| 450 | continue;
|
| 451 |
|
| 452 | rela = find_rela_by_dest_range(insn->sec, insn->offset,
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| 453 | insn->len);
|
| 454 | if (!rela) {
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| 455 | dest_off = insn->offset + insn->len + insn->immediate;
|
| 456 | insn->call_dest = find_symbol_by_offset(insn->sec,
|
| 457 | dest_off);
|
| 458 | if (!insn->call_dest) {
|
| 459 | WARN_FUNC("can't find call dest symbol at offset 0x%lx",
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| 460 | insn->sec, insn->offset, dest_off);
|
| 461 | return -1;
|
| 462 | }
|
| 463 | } else if (rela->sym->type == STT_SECTION) {
|
| 464 | insn->call_dest = find_symbol_by_offset(rela->sym->sec,
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| 465 | rela->addend+4);
|
| 466 | if (!insn->call_dest ||
|
| 467 | insn->call_dest->type != STT_FUNC) {
|
| 468 | WARN_FUNC("can't find call dest symbol at %s+0x%x",
|
| 469 | insn->sec, insn->offset,
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| 470 | rela->sym->sec->name,
|
| 471 | rela->addend + 4);
|
| 472 | return -1;
|
| 473 | }
|
| 474 | } else
|
| 475 | insn->call_dest = rela->sym;
|
| 476 | }
|
| 477 |
|
| 478 | return 0;
|
| 479 | }
|
| 480 |
|
| 481 | |
| 482 | * The .alternatives section requires some extra special care, over and above
|
| 483 | * what other special sections require:
|
| 484 | *
|
| 485 | * 1. Because alternatives are patched in-place, we need to insert a fake jump
|
| 486 | * instruction at the end so that validate_branch() skips all the original
|
| 487 | * replaced instructions when validating the new instruction path.
|
| 488 | *
|
| 489 | * 2. An added wrinkle is that the new instruction length might be zero. In
|
| 490 | * that case the old instructions are replaced with noops. We simulate that
|
| 491 | * by creating a fake jump as the only new instruction.
|
| 492 | *
|
| 493 | * 3. In some cases, the alternative section includes an instruction which
|
| 494 | * conditionally jumps to the _end_ of the entry. We have to modify these
|
| 495 | * jumps' destinations to point back to .text rather than the end of the
|
| 496 | * entry in .altinstr_replacement.
|
| 497 | *
|
| 498 | * 4. It has been requested that we don't validate the !POPCNT feature path
|
| 499 | * which is a "very very small percentage of machines".
|
| 500 |
|
| 501 | static int handle_group_alt(struct objtool_file *file,
|
| 502 | struct special_alt *special_alt,
|
| 503 | struct instruction *orig_insn,
|
| 504 | struct instruction **new_insn)
|
| 505 | {
|
| 506 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
|
| 507 | unsigned long dest_off;
|
| 508 |
|
| 509 | last_orig_insn = NULL;
|
| 510 | insn = orig_insn;
|
| 511 | sec_for_each_insn_from(file, insn) {
|
| 512 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
|
| 513 | break;
|
| 514 |
|
| 515 | if (special_alt->skip_orig)
|
| 516 | insn->type = INSN_NOP;
|
| 517 |
|
| 518 | insn->alt_group = true;
|
| 519 | last_orig_insn = insn;
|
| 520 | }
|
| 521 |
|
| 522 | if (!next_insn_same_sec(file, last_orig_insn)) {
|
| 523 | WARN("%s: don't know how to handle alternatives at end of section",
|
| 524 | special_alt->orig_sec->name);
|
| 525 | return -1;
|
| 526 | }
|
| 527 |
|
| 528 | fake_jump = malloc(sizeof(*fake_jump));
|
| 529 | if (!fake_jump) {
|
| 530 | WARN("malloc failed");
|
| 531 | return -1;
|
| 532 | }
|
| 533 | memset(fake_jump, 0, sizeof(*fake_jump));
|
| 534 | INIT_LIST_HEAD(&fake_jump->alts);
|
| 535 | clear_insn_state(&fake_jump->state);
|
| 536 |
|
| 537 | fake_jump->sec = special_alt->new_sec;
|
| 538 | fake_jump->offset = -1;
|
| 539 | fake_jump->type = INSN_JUMP_UNCONDITIONAL;
|
| 540 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
|
| 541 | fake_jump->ignore = true;
|
| 542 |
|
| 543 | if (!special_alt->new_len) {
|
| 544 | *new_insn = fake_jump;
|
| 545 | return 0;
|
| 546 | }
|
| 547 |
|
| 548 | last_new_insn = NULL;
|
| 549 | insn = *new_insn;
|
| 550 | sec_for_each_insn_from(file, insn) {
|
| 551 | if (insn->offset >= special_alt->new_off + special_alt->new_len)
|
| 552 | break;
|
| 553 |
|
| 554 | last_new_insn = insn;
|
| 555 |
|
| 556 | if (insn->type != INSN_JUMP_CONDITIONAL &&
|
| 557 | insn->type != INSN_JUMP_UNCONDITIONAL)
|
| 558 | continue;
|
| 559 |
|
| 560 | if (!insn->immediate)
|
| 561 | continue;
|
| 562 |
|
| 563 | dest_off = insn->offset + insn->len + insn->immediate;
|
| 564 | if (dest_off == special_alt->new_off + special_alt->new_len)
|
| 565 | insn->jump_dest = fake_jump;
|
| 566 |
|
| 567 | if (!insn->jump_dest) {
|
| 568 | WARN_FUNC("can't find alternative jump destination",
|
| 569 | insn->sec, insn->offset);
|
| 570 | return -1;
|
| 571 | }
|
| 572 | }
|
| 573 |
|
| 574 | if (!last_new_insn) {
|
| 575 | WARN_FUNC("can't find last new alternative instruction",
|
| 576 | special_alt->new_sec, special_alt->new_off);
|
| 577 | return -1;
|
| 578 | }
|
| 579 |
|
| 580 | list_add(&fake_jump->list, &last_new_insn->list);
|
| 581 |
|
| 582 | return 0;
|
| 583 | }
|
| 584 |
|
| 585 | |
| 586 | * A jump table entry can either convert a nop to a jump or a jump to a nop.
|
| 587 | * If the original instruction is a jump, make the alt entry an effective nop
|
| 588 | * by just skipping the original instruction.
|
| 589 |
|
| 590 | static int handle_jump_alt(struct objtool_file *file,
|
| 591 | struct special_alt *special_alt,
|
| 592 | struct instruction *orig_insn,
|
| 593 | struct instruction **new_insn)
|
| 594 | {
|
| 595 | if (orig_insn->type == INSN_NOP)
|
| 596 | return 0;
|
| 597 |
|
| 598 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
|
| 599 | WARN_FUNC("unsupported instruction at jump label",
|
| 600 | orig_insn->sec, orig_insn->offset);
|
| 601 | return -1;
|
| 602 | }
|
| 603 |
|
| 604 | *new_insn = list_next_entry(orig_insn, list);
|
| 605 | return 0;
|
| 606 | }
|
| 607 |
|
| 608 | |
| 609 | * Read all the special sections which have alternate instructions which can be
|
| 610 | * patched in or redirected to at runtime. Each instruction having alternate
|
| 611 | * instruction(s) has them added to its insn->alts list, which will be
|
| 612 | * traversed in validate_branch().
|
| 613 |
|
| 614 | static int add_special_section_alts(struct objtool_file *file)
|
| 615 | {
|
| 616 | struct list_head special_alts;
|
| 617 | struct instruction *orig_insn, *new_insn;
|
| 618 | struct special_alt *special_alt, *tmp;
|
| 619 | struct alternative *alt;
|
| 620 | int ret;
|
| 621 |
|
| 622 | ret = special_get_alts(file->elf, &special_alts);
|
| 623 | if (ret)
|
| 624 | return ret;
|
| 625 |
|
| 626 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
|
| 627 | alt = malloc(sizeof(*alt));
|
| 628 | if (!alt) {
|
| 629 | WARN("malloc failed");
|
| 630 | ret = -1;
|
| 631 | goto out;
|
| 632 | }
|
| 633 |
|
| 634 | orig_insn = find_insn(file, special_alt->orig_sec,
|
| 635 | special_alt->orig_off);
|
| 636 | if (!orig_insn) {
|
| 637 | WARN_FUNC("special: can't find orig instruction",
|
| 638 | special_alt->orig_sec, special_alt->orig_off);
|
| 639 | ret = -1;
|
| 640 | goto out;
|
| 641 | }
|
| 642 |
|
| 643 | new_insn = NULL;
|
| 644 | if (!special_alt->group || special_alt->new_len) {
|
| 645 | new_insn = find_insn(file, special_alt->new_sec,
|
| 646 | special_alt->new_off);
|
| 647 | if (!new_insn) {
|
| 648 | WARN_FUNC("special: can't find new instruction",
|
| 649 | special_alt->new_sec,
|
| 650 | special_alt->new_off);
|
| 651 | ret = -1;
|
| 652 | goto out;
|
| 653 | }
|
| 654 | }
|
| 655 |
|
| 656 | if (special_alt->group) {
|
| 657 | ret = handle_group_alt(file, special_alt, orig_insn,
|
| 658 | &new_insn);
|
| 659 | if (ret)
|
| 660 | goto out;
|
| 661 | } else if (special_alt->jump_or_nop) {
|
| 662 | ret = handle_jump_alt(file, special_alt, orig_insn,
|
| 663 | &new_insn);
|
| 664 | if (ret)
|
| 665 | goto out;
|
| 666 | }
|
| 667 |
|
| 668 | alt->insn = new_insn;
|
| 669 | list_add_tail(&alt->list, &orig_insn->alts);
|
| 670 |
|
| 671 | list_del(&special_alt->list);
|
| 672 | free(special_alt);
|
| 673 | }
|
| 674 |
|
| 675 | out:
|
| 676 | return ret;
|
| 677 | }
|
| 678 |
|
| 679 | static int add_switch_table(struct objtool_file *file, struct symbol *func,
|
| 680 | struct instruction *insn, struct rela *table,
|
| 681 | struct rela *next_table)
|
| 682 | {
|
| 683 | struct rela *rela = table;
|
| 684 | struct instruction *alt_insn;
|
| 685 | struct alternative *alt;
|
| 686 |
|
| 687 | list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
|
| 688 | if (rela == next_table)
|
| 689 | break;
|
| 690 |
|
| 691 | if (rela->sym->sec != insn->sec ||
|
| 692 | rela->addend <= func->offset ||
|
| 693 | rela->addend >= func->offset + func->len)
|
| 694 | break;
|
| 695 |
|
| 696 | alt_insn = find_insn(file, insn->sec, rela->addend);
|
| 697 | if (!alt_insn) {
|
| 698 | WARN("%s: can't find instruction at %s+0x%x",
|
| 699 | file->rodata->rela->name, insn->sec->name,
|
| 700 | rela->addend);
|
| 701 | return -1;
|
| 702 | }
|
| 703 |
|
| 704 | alt = malloc(sizeof(*alt));
|
| 705 | if (!alt) {
|
| 706 | WARN("malloc failed");
|
| 707 | return -1;
|
| 708 | }
|
| 709 |
|
| 710 | alt->insn = alt_insn;
|
| 711 | list_add_tail(&alt->list, &insn->alts);
|
| 712 | }
|
| 713 |
|
| 714 | return 0;
|
| 715 | }
|
| 716 |
|
| 717 | |
| 718 | * find_switch_table() - Given a dynamic jump, find the switch jump table in
|
| 719 | * .rodata associated with it.
|
| 720 | *
|
| 721 | * There are 3 basic patterns:
|
| 722 | *
|
| 723 | * 1. jmpq *[rodata addr](,%reg,8)
|
| 724 | *
|
| 725 | * This is the most common case by far. It jumps to an address in a simple
|
| 726 | * jump table which is stored in .rodata.
|
| 727 | *
|
| 728 | * 2. jmpq *[rodata addr](%rip)
|
| 729 | *
|
| 730 | * This is caused by a rare GCC quirk, currently only seen in three driver
|
| 731 | * functions in the kernel, only with certain obscure non-distro configs.
|
| 732 | *
|
| 733 | * As part of an optimization, GCC makes a copy of an existing switch jump
|
| 734 | * table, modifies it, and then hard-codes the jump (albeit with an indirect
|
| 735 | * jump) to use a single entry in the table. The rest of the jump table and
|
| 736 | * some of its jump targets remain as dead code.
|
| 737 | *
|
| 738 | * In such a case we can just crudely ignore all unreachable instruction
|
| 739 | * warnings for the entire object file. Ideally we would just ignore them
|
| 740 | * for the function, but that would require redesigning the code quite a
|
| 741 | * bit. And honestly that's just not worth doing: unreachable instruction
|
| 742 | * warnings are of questionable value anyway, and this is such a rare issue.
|
| 743 | *
|
| 744 | * 3. mov [rodata addr],%reg1
|
| 745 | * ... some instructions ...
|
| 746 | * jmpq *(%reg1,%reg2,8)
|
| 747 | *
|
| 748 | * This is a fairly uncommon pattern which is new for GCC 6. As of this
|
| 749 | * writing, there are 11 occurrences of it in the allmodconfig kernel.
|
| 750 | *
|
| 751 | * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
|
| 752 | * ensure the same register is used in the mov and jump instructions.
|
| 753 |
|
| 754 | static struct rela *find_switch_table(struct objtool_file *file,
|
| 755 | struct symbol *func,
|
| 756 | struct instruction *insn)
|
| 757 | {
|
| 758 | struct rela *text_rela, *rodata_rela;
|
| 759 | struct instruction *orig_insn = insn;
|
| 760 |
|
| 761 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
|
| 762 | if (text_rela && text_rela->sym == file->rodata->sym) {
|
| 763 |
|
| 764 | rodata_rela = find_rela_by_dest(file->rodata,
|
| 765 | text_rela->addend);
|
| 766 | if (rodata_rela)
|
| 767 | return rodata_rela;
|
| 768 |
|
| 769 |
|
| 770 | rodata_rela = find_rela_by_dest(file->rodata,
|
| 771 | text_rela->addend + 4);
|
| 772 | if (!rodata_rela)
|
| 773 | return NULL;
|
| 774 | file->ignore_unreachables = true;
|
| 775 | return rodata_rela;
|
| 776 | }
|
| 777 |
|
| 778 |
|
| 779 | func_for_each_insn_continue_reverse(file, func, insn) {
|
| 780 | if (insn->type == INSN_JUMP_DYNAMIC)
|
| 781 | break;
|
| 782 |
|
| 783 |
|
| 784 | if (insn->type == INSN_JUMP_UNCONDITIONAL &&
|
| 785 | insn->jump_dest &&
|
| 786 | (insn->jump_dest->offset <= insn->offset ||
|
| 787 | insn->jump_dest->offset > orig_insn->offset))
|
| 788 | break;
|
| 789 |
|
| 790 |
|
| 791 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
|
| 792 | insn->len);
|
| 793 | if (!text_rela || text_rela->sym != file->rodata->sym)
|
| 794 | continue;
|
| 795 |
|
| 796 | |
| 797 | * Make sure the .rodata address isn't associated with a
|
| 798 | * symbol. gcc jump tables are anonymous data.
|
| 799 |
|
| 800 | if (find_symbol_containing(file->rodata, text_rela->addend))
|
| 801 | continue;
|
| 802 |
|
| 803 | return find_rela_by_dest(file->rodata, text_rela->addend);
|
| 804 | }
|
| 805 |
|
| 806 | return NULL;
|
| 807 | }
|
| 808 |
|
| 809 | static int add_func_switch_tables(struct objtool_file *file,
|
| 810 | struct symbol *func)
|
| 811 | {
|
| 812 | struct instruction *insn, *prev_jump = NULL;
|
| 813 | struct rela *rela, *prev_rela = NULL;
|
| 814 | int ret;
|
| 815 |
|
| 816 | func_for_each_insn(file, func, insn) {
|
| 817 | if (insn->type != INSN_JUMP_DYNAMIC)
|
| 818 | continue;
|
| 819 |
|
| 820 | rela = find_switch_table(file, func, insn);
|
| 821 | if (!rela)
|
| 822 | continue;
|
| 823 |
|
| 824 | |
| 825 | * We found a switch table, but we don't know yet how big it
|
| 826 | * is. Don't add it until we reach the end of the function or
|
| 827 | * the beginning of another switch table in the same function.
|
| 828 |
|
| 829 | if (prev_jump) {
|
| 830 | ret = add_switch_table(file, func, prev_jump, prev_rela,
|
| 831 | rela);
|
| 832 | if (ret)
|
| 833 | return ret;
|
| 834 | }
|
| 835 |
|
| 836 | prev_jump = insn;
|
| 837 | prev_rela = rela;
|
| 838 | }
|
| 839 |
|
| 840 | if (prev_jump) {
|
| 841 | ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
|
| 842 | if (ret)
|
| 843 | return ret;
|
| 844 | }
|
| 845 |
|
| 846 | return 0;
|
| 847 | }
|
| 848 |
|
| 849 | |
| 850 | * For some switch statements, gcc generates a jump table in the .rodata
|
| 851 | * section which contains a list of addresses within the function to jump to.
|
| 852 | * This finds these jump tables and adds them to the insn->alts lists.
|
| 853 |
|
| 854 | static int add_switch_table_alts(struct objtool_file *file)
|
| 855 | {
|
| 856 | struct section *sec;
|
| 857 | struct symbol *func;
|
| 858 | int ret;
|
| 859 |
|
| 860 | if (!file->rodata || !file->rodata->rela)
|
| 861 | return 0;
|
| 862 |
|
| 863 | for_each_sec(file, sec) {
|
| 864 | list_for_each_entry(func, &sec->symbol_list, list) {
|
| 865 | if (func->type != STT_FUNC)
|
| 866 | continue;
|
| 867 |
|
| 868 | ret = add_func_switch_tables(file, func);
|
| 869 | if (ret)
|
| 870 | return ret;
|
| 871 | }
|
| 872 | }
|
| 873 |
|
| 874 | return 0;
|
| 875 | }
|
| 876 |
|
| 877 | static int decode_sections(struct objtool_file *file)
|
| 878 | {
|
| 879 | int ret;
|
| 880 |
|
| 881 | ret = decode_instructions(file);
|
| 882 | if (ret)
|
| 883 | return ret;
|
| 884 |
|
| 885 | ret = add_dead_ends(file);
|
| 886 | if (ret)
|
| 887 | return ret;
|
| 888 |
|
| 889 | add_ignores(file);
|
| 890 |
|
| 891 | ret = add_jump_destinations(file);
|
| 892 | if (ret)
|
| 893 | return ret;
|
| 894 |
|
| 895 | ret = add_call_destinations(file);
|
| 896 | if (ret)
|
| 897 | return ret;
|
| 898 |
|
| 899 | ret = add_special_section_alts(file);
|
| 900 | if (ret)
|
| 901 | return ret;
|
| 902 |
|
| 903 | ret = add_switch_table_alts(file);
|
| 904 | if (ret)
|
| 905 | return ret;
|
| 906 |
|
| 907 | return 0;
|
| 908 | }
|
| 909 |
|
| 910 | static bool is_fentry_call(struct instruction *insn)
|
| 911 | {
|
| 912 | if (insn->type == INSN_CALL &&
|
| 913 | insn->call_dest->type == STT_NOTYPE &&
|
| 914 | !strcmp(insn->call_dest->name, "__fentry__"))
|
| 915 | return true;
|
| 916 |
|
| 917 | return false;
|
| 918 | }
|
| 919 |
|
| 920 | static bool has_modified_stack_frame(struct insn_state *state)
|
| 921 | {
|
| 922 | int i;
|
| 923 |
|
| 924 | if (state->cfa.base != initial_func_cfi.cfa.base ||
|
| 925 | state->cfa.offset != initial_func_cfi.cfa.offset ||
|
| 926 | state->stack_size != initial_func_cfi.cfa.offset ||
|
| 927 | state->drap)
|
| 928 | return true;
|
| 929 |
|
| 930 | for (i = 0; i < CFI_NUM_REGS; i++)
|
| 931 | if (state->regs[i].base != initial_func_cfi.regs[i].base ||
|
| 932 | state->regs[i].offset != initial_func_cfi.regs[i].offset)
|
| 933 | return true;
|
| 934 |
|
| 935 | return false;
|
| 936 | }
|
| 937 |
|
| 938 | static bool has_valid_stack_frame(struct insn_state *state)
|
| 939 | {
|
| 940 | if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
|
| 941 | state->regs[CFI_BP].offset == -16)
|
| 942 | return true;
|
| 943 |
|
| 944 | if (state->drap && state->regs[CFI_BP].base == CFI_BP)
|
| 945 | return true;
|
| 946 |
|
| 947 | return false;
|
| 948 | }
|
| 949 |
|
| 950 | static void save_reg(struct insn_state *state, unsigned char reg, int base,
|
| 951 | int offset)
|
| 952 | {
|
| 953 | if ((arch_callee_saved_reg(reg) ||
|
| 954 | (state->drap && reg == state->drap_reg)) &&
|
| 955 | state->regs[reg].base == CFI_UNDEFINED) {
|
| 956 | state->regs[reg].base = base;
|
| 957 | state->regs[reg].offset = offset;
|
| 958 | }
|
| 959 | }
|
| 960 |
|
| 961 | static void restore_reg(struct insn_state *state, unsigned char reg)
|
| 962 | {
|
| 963 | state->regs[reg].base = CFI_UNDEFINED;
|
| 964 | state->regs[reg].offset = 0;
|
| 965 | }
|
| 966 |
|
| 967 | |
| 968 | * A note about DRAP stack alignment:
|
| 969 | *
|
| 970 | * GCC has the concept of a DRAP register, which is used to help keep track of
|
| 971 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
|
| 972 | * register. The typical DRAP pattern is:
|
| 973 | *
|
| 974 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
|
| 975 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
|
| 976 | * 41 ff 72 f8 pushq -0x8(%r10)
|
| 977 | * 55 push %rbp
|
| 978 | * 48 89 e5 mov %rsp,%rbp
|
| 979 | * (more pushes)
|
| 980 | * 41 52 push %r10
|
| 981 | * ...
|
| 982 | * 41 5a pop %r10
|
| 983 | * (more pops)
|
| 984 | * 5d pop %rbp
|
| 985 | * 49 8d 62 f8 lea -0x8(%r10),%rsp
|
| 986 | * c3 retq
|
| 987 | *
|
| 988 | * There are some variations in the epilogues, like:
|
| 989 | *
|
| 990 | * 5b pop %rbx
|
| 991 | * 41 5a pop %r10
|
| 992 | * 41 5c pop %r12
|
| 993 | * 41 5d pop %r13
|
| 994 | * 41 5e pop %r14
|
| 995 | * c9 leaveq
|
| 996 | * 49 8d 62 f8 lea -0x8(%r10),%rsp
|
| 997 | * c3 retq
|
| 998 | *
|
| 999 | * and:
|
| 1000 | *
|
| 1001 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10
|
| 1002 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx
|
| 1003 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12
|
| 1004 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13
|
| 1005 | * c9 leaveq
|
| 1006 | * 49 8d 62 f8 lea -0x8(%r10),%rsp
|
| 1007 | * c3 retq
|
| 1008 | *
|
| 1009 | * Sometimes r13 is used as the DRAP register, in which case it's saved and
|
| 1010 | * restored beforehand:
|
| 1011 | *
|
| 1012 | * 41 55 push %r13
|
| 1013 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
|
| 1014 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
|
| 1015 | * ...
|
| 1016 | * 49 8d 65 f0 lea -0x10(%r13),%rsp
|
| 1017 | * 41 5d pop %r13
|
| 1018 | * c3 retq
|
| 1019 |
|
| 1020 | static int update_insn_state(struct instruction *insn, struct insn_state *state)
|
| 1021 | {
|
| 1022 | struct stack_op *op = &insn->stack_op;
|
| 1023 | struct cfi_reg *cfa = &state->cfa;
|
| 1024 | struct cfi_reg *regs = state->regs;
|
| 1025 |
|
| 1026 |
|
| 1027 | if (cfa->base == CFI_UNDEFINED) {
|
| 1028 | if (insn->func) {
|
| 1029 | WARN_FUNC("undefined stack state", insn->sec, insn->offset);
|
| 1030 | return -1;
|
| 1031 | }
|
| 1032 | return 0;
|
| 1033 | }
|
| 1034 |
|
| 1035 | switch (op->dest.type) {
|
| 1036 |
|
| 1037 | case OP_DEST_REG:
|
| 1038 | switch (op->src.type) {
|
| 1039 |
|
| 1040 | case OP_SRC_REG:
|
| 1041 | if (cfa->base == op->src.reg && cfa->base == CFI_SP &&
|
| 1042 | op->dest.reg == CFI_BP && regs[CFI_BP].base == CFI_CFA &&
|
| 1043 | regs[CFI_BP].offset == -cfa->offset) {
|
| 1044 |
|
| 1045 |
|
| 1046 | cfa->base = op->dest.reg;
|
| 1047 | state->bp_scratch = false;
|
| 1048 | } else if (state->drap) {
|
| 1049 |
|
| 1050 |
|
| 1051 | regs[CFI_BP].base = CFI_BP;
|
| 1052 | regs[CFI_BP].offset = -state->stack_size;
|
| 1053 | state->bp_scratch = false;
|
| 1054 | } else if (!nofp) {
|
| 1055 |
|
| 1056 | WARN_FUNC("unknown stack-related register move",
|
| 1057 | insn->sec, insn->offset);
|
| 1058 | return -1;
|
| 1059 | }
|
| 1060 |
|
| 1061 | break;
|
| 1062 |
|
| 1063 | case OP_SRC_ADD:
|
| 1064 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
|
| 1065 |
|
| 1066 |
|
| 1067 | state->stack_size -= op->src.offset;
|
| 1068 | if (cfa->base == CFI_SP)
|
| 1069 | cfa->offset -= op->src.offset;
|
| 1070 | break;
|
| 1071 | }
|
| 1072 |
|
| 1073 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
|
| 1074 |
|
| 1075 |
|
| 1076 | state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
|
| 1077 | break;
|
| 1078 | }
|
| 1079 |
|
| 1080 | if (op->dest.reg != CFI_BP && op->src.reg == CFI_SP &&
|
| 1081 | cfa->base == CFI_SP) {
|
| 1082 |
|
| 1083 |
|
| 1084 | state->drap_reg = op->dest.reg;
|
| 1085 | break;
|
| 1086 | }
|
| 1087 |
|
| 1088 | if (state->drap && op->dest.reg == CFI_SP &&
|
| 1089 | op->src.reg == state->drap_reg) {
|
| 1090 |
|
| 1091 |
|
| 1092 | cfa->base = CFI_SP;
|
| 1093 | cfa->offset = state->stack_size = -op->src.offset;
|
| 1094 | state->drap_reg = CFI_UNDEFINED;
|
| 1095 | state->drap = false;
|
| 1096 | break;
|
| 1097 | }
|
| 1098 |
|
| 1099 | if (op->dest.reg == state->cfa.base) {
|
| 1100 | WARN_FUNC("unsupported stack register modification",
|
| 1101 | insn->sec, insn->offset);
|
| 1102 | return -1;
|
| 1103 | }
|
| 1104 |
|
| 1105 | break;
|
| 1106 |
|
| 1107 | case OP_SRC_AND:
|
| 1108 | if (op->dest.reg != CFI_SP ||
|
| 1109 | (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
|
| 1110 | (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
|
| 1111 | WARN_FUNC("unsupported stack pointer realignment",
|
| 1112 | insn->sec, insn->offset);
|
| 1113 | return -1;
|
| 1114 | }
|
| 1115 |
|
| 1116 | if (state->drap_reg != CFI_UNDEFINED) {
|
| 1117 |
|
| 1118 | cfa->base = state->drap_reg;
|
| 1119 | cfa->offset = state->stack_size = 0;
|
| 1120 | state->drap = true;
|
| 1121 |
|
| 1122 | }
|
| 1123 |
|
| 1124 | |
| 1125 | * Older versions of GCC (4.8ish) realign the stack
|
| 1126 | * without DRAP, with a frame pointer.
|
| 1127 |
|
| 1128 |
|
| 1129 | break;
|
| 1130 |
|
| 1131 | case OP_SRC_POP:
|
| 1132 | if (!state->drap && op->dest.type == OP_DEST_REG &&
|
| 1133 | op->dest.reg == cfa->base) {
|
| 1134 |
|
| 1135 |
|
| 1136 | cfa->base = CFI_SP;
|
| 1137 | }
|
| 1138 |
|
| 1139 | if (regs[op->dest.reg].offset == -state->stack_size) {
|
| 1140 |
|
| 1141 | if (state->drap && cfa->base == CFI_BP_INDIRECT &&
|
| 1142 | op->dest.type == OP_DEST_REG &&
|
| 1143 | op->dest.reg == state->drap_reg) {
|
| 1144 |
|
| 1145 |
|
| 1146 | cfa->base = state->drap_reg;
|
| 1147 | cfa->offset = 0;
|
| 1148 | }
|
| 1149 |
|
| 1150 | restore_reg(state, op->dest.reg);
|
| 1151 | }
|
| 1152 |
|
| 1153 | state->stack_size -= 8;
|
| 1154 | if (cfa->base == CFI_SP)
|
| 1155 | cfa->offset -= 8;
|
| 1156 |
|
| 1157 | break;
|
| 1158 |
|
| 1159 | case OP_SRC_REG_INDIRECT:
|
| 1160 | if (state->drap && op->src.reg == CFI_BP &&
|
| 1161 | op->src.offset == regs[op->dest.reg].offset) {
|
| 1162 |
|
| 1163 |
|
| 1164 | if (op->dest.reg == state->drap_reg) {
|
| 1165 | cfa->base = state->drap_reg;
|
| 1166 | cfa->offset = 0;
|
| 1167 | }
|
| 1168 |
|
| 1169 | restore_reg(state, op->dest.reg);
|
| 1170 |
|
| 1171 | } else if (op->src.reg == cfa->base &&
|
| 1172 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
|
| 1173 |
|
| 1174 |
|
| 1175 |
|
| 1176 | restore_reg(state, op->dest.reg);
|
| 1177 | }
|
| 1178 |
|
| 1179 | break;
|
| 1180 |
|
| 1181 | default:
|
| 1182 | WARN_FUNC("unknown stack-related instruction",
|
| 1183 | insn->sec, insn->offset);
|
| 1184 | return -1;
|
| 1185 | }
|
| 1186 |
|
| 1187 | break;
|
| 1188 |
|
| 1189 | case OP_DEST_PUSH:
|
| 1190 | state->stack_size += 8;
|
| 1191 | if (cfa->base == CFI_SP)
|
| 1192 | cfa->offset += 8;
|
| 1193 |
|
| 1194 | if (op->src.type != OP_SRC_REG)
|
| 1195 | break;
|
| 1196 |
|
| 1197 | if (state->drap) {
|
| 1198 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
|
| 1199 |
|
| 1200 |
|
| 1201 | cfa->base = CFI_BP_INDIRECT;
|
| 1202 | cfa->offset = -state->stack_size;
|
| 1203 |
|
| 1204 |
|
| 1205 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
|
| 1206 |
|
| 1207 | } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
|
| 1208 |
|
| 1209 |
|
| 1210 | state->stack_size = 0;
|
| 1211 |
|
| 1212 | } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
|
| 1213 |
|
| 1214 |
|
| 1215 | save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
|
| 1216 | }
|
| 1217 |
|
| 1218 | } else {
|
| 1219 |
|
| 1220 |
|
| 1221 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
|
| 1222 | }
|
| 1223 |
|
| 1224 |
|
| 1225 | if (!nofp && insn->func && op->src.reg == CFI_BP &&
|
| 1226 | cfa->base != CFI_BP)
|
| 1227 | state->bp_scratch = true;
|
| 1228 | break;
|
| 1229 |
|
| 1230 | case OP_DEST_REG_INDIRECT:
|
| 1231 |
|
| 1232 | if (state->drap) {
|
| 1233 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
|
| 1234 |
|
| 1235 |
|
| 1236 | cfa->base = CFI_BP_INDIRECT;
|
| 1237 | cfa->offset = op->dest.offset;
|
| 1238 |
|
| 1239 |
|
| 1240 | save_reg(state, op->src.reg, CFI_CFA, op->dest.offset);
|
| 1241 | }
|
| 1242 |
|
| 1243 | else if (regs[op->src.reg].base == CFI_UNDEFINED) {
|
| 1244 |
|
| 1245 |
|
| 1246 | save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
|
| 1247 | }
|
| 1248 |
|
| 1249 | } else if (op->dest.reg == cfa->base) {
|
| 1250 |
|
| 1251 |
|
| 1252 |
|
| 1253 | save_reg(state, op->src.reg, CFI_CFA,
|
| 1254 | op->dest.offset - state->cfa.offset);
|
| 1255 | }
|
| 1256 |
|
| 1257 | break;
|
| 1258 |
|
| 1259 | case OP_DEST_LEAVE:
|
| 1260 | if ((!state->drap && cfa->base != CFI_BP) ||
|
| 1261 | (state->drap && cfa->base != state->drap_reg)) {
|
| 1262 | WARN_FUNC("leave instruction with modified stack frame",
|
| 1263 | insn->sec, insn->offset);
|
| 1264 | return -1;
|
| 1265 | }
|
| 1266 |
|
| 1267 |
|
| 1268 |
|
| 1269 | state->stack_size = -state->regs[CFI_BP].offset - 8;
|
| 1270 | restore_reg(state, CFI_BP);
|
| 1271 |
|
| 1272 | if (!state->drap) {
|
| 1273 | cfa->base = CFI_SP;
|
| 1274 | cfa->offset -= 8;
|
| 1275 | }
|
| 1276 |
|
| 1277 | break;
|
| 1278 |
|
| 1279 | case OP_DEST_MEM:
|
| 1280 | if (op->src.type != OP_SRC_POP) {
|
| 1281 | WARN_FUNC("unknown stack-related memory operation",
|
| 1282 | insn->sec, insn->offset);
|
| 1283 | return -1;
|
| 1284 | }
|
| 1285 |
|
| 1286 |
|
| 1287 | state->stack_size -= 8;
|
| 1288 | if (cfa->base == CFI_SP)
|
| 1289 | cfa->offset -= 8;
|
| 1290 |
|
| 1291 | break;
|
| 1292 |
|
| 1293 | default:
|
| 1294 | WARN_FUNC("unknown stack-related instruction",
|
| 1295 | insn->sec, insn->offset);
|
| 1296 | return -1;
|
| 1297 | }
|
| 1298 |
|
| 1299 | return 0;
|
| 1300 | }
|
| 1301 |
|
| 1302 | static bool insn_state_match(struct instruction *insn, struct insn_state *state)
|
| 1303 | {
|
| 1304 | struct insn_state *state1 = &insn->state, *state2 = state;
|
| 1305 | int i;
|
| 1306 |
|
| 1307 | if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
|
| 1308 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
|
| 1309 | insn->sec, insn->offset,
|
| 1310 | state1->cfa.base, state1->cfa.offset,
|
| 1311 | state2->cfa.base, state2->cfa.offset);
|
| 1312 |
|
| 1313 | } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
|
| 1314 | for (i = 0; i < CFI_NUM_REGS; i++) {
|
| 1315 | if (!memcmp(&state1->regs[i], &state2->regs[i],
|
| 1316 | sizeof(struct cfi_reg)))
|
| 1317 | continue;
|
| 1318 |
|
| 1319 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
|
| 1320 | insn->sec, insn->offset,
|
| 1321 | i, state1->regs[i].base, state1->regs[i].offset,
|
| 1322 | i, state2->regs[i].base, state2->regs[i].offset);
|
| 1323 | break;
|
| 1324 | }
|
| 1325 |
|
| 1326 | } else if (state1->drap != state2->drap ||
|
| 1327 | (state1->drap && state1->drap_reg != state2->drap_reg)) {
|
| 1328 | WARN_FUNC("stack state mismatch: drap1=%d(%d) drap2=%d(%d)",
|
| 1329 | insn->sec, insn->offset,
|
| 1330 | state1->drap, state1->drap_reg,
|
| 1331 | state2->drap, state2->drap_reg);
|
| 1332 |
|
| 1333 | } else
|
| 1334 | return true;
|
| 1335 |
|
| 1336 | return false;
|
| 1337 | }
|
| 1338 |
|
| 1339 | |
| 1340 | * Follow the branch starting at the given instruction, and recursively follow
|
| 1341 | * any other branches (jumps). Meanwhile, track the frame pointer state at
|
| 1342 | * each instruction and validate all the rules described in
|
| 1343 | * tools/objtool/Documentation/stack-validation.txt.
|
| 1344 |
|
| 1345 | static int validate_branch(struct objtool_file *file, struct instruction *first,
|
| 1346 | struct insn_state state)
|
| 1347 | {
|
| 1348 | struct alternative *alt;
|
| 1349 | struct instruction *insn;
|
| 1350 | struct section *sec;
|
| 1351 | struct symbol *func = NULL;
|
| 1352 | int ret;
|
| 1353 |
|
| 1354 | insn = first;
|
| 1355 | sec = insn->sec;
|
| 1356 |
|
| 1357 | if (insn->alt_group && list_empty(&insn->alts)) {
|
| 1358 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
|
| 1359 | sec, insn->offset);
|
| 1360 | return -1;
|
| 1361 | }
|
| 1362 |
|
| 1363 | while (1) {
|
| 1364 | if (file->c_file && insn->func) {
|
| 1365 | if (func && func != insn->func) {
|
| 1366 | WARN("%s() falls through to next function %s()",
|
| 1367 | func->name, insn->func->name);
|
| 1368 | return 1;
|
| 1369 | }
|
| 1370 | }
|
| 1371 |
|
| 1372 | func = insn->func;
|
| 1373 |
|
| 1374 | if (func && insn->ignore) {
|
| 1375 | WARN_FUNC("BUG: why am I validating an ignored function?",
|
| 1376 | sec, insn->offset);
|
| 1377 | return -1;
|
| 1378 | }
|
| 1379 |
|
| 1380 | if (insn->visited) {
|
| 1381 | if (!!insn_state_match(insn, &state))
|
| 1382 | return 1;
|
| 1383 |
|
| 1384 | return 0;
|
| 1385 | }
|
| 1386 |
|
| 1387 | insn->state = state;
|
| 1388 |
|
| 1389 | insn->visited = true;
|
| 1390 |
|
| 1391 | list_for_each_entry(alt, &insn->alts, list) {
|
| 1392 | ret = validate_branch(file, alt->insn, state);
|
| 1393 | if (ret)
|
| 1394 | return 1;
|
| 1395 | }
|
| 1396 |
|
| 1397 | switch (insn->type) {
|
| 1398 |
|
| 1399 | case INSN_RETURN:
|
| 1400 | if (func && has_modified_stack_frame(&state)) {
|
| 1401 | WARN_FUNC("return with modified stack frame",
|
| 1402 | sec, insn->offset);
|
| 1403 | return 1;
|
| 1404 | }
|
| 1405 |
|
| 1406 | if (state.bp_scratch) {
|
| 1407 | WARN("%s uses BP as a scratch register",
|
| 1408 | insn->func->name);
|
| 1409 | return 1;
|
| 1410 | }
|
| 1411 |
|
| 1412 | return 0;
|
| 1413 |
|
| 1414 | case INSN_CALL:
|
| 1415 | if (is_fentry_call(insn))
|
| 1416 | break;
|
| 1417 |
|
| 1418 | ret = dead_end_function(file, insn->call_dest);
|
| 1419 | if (ret == 1)
|
| 1420 | return 0;
|
| 1421 | if (ret == -1)
|
| 1422 | return 1;
|
| 1423 |
|
| 1424 |
|
| 1425 | case INSN_CALL_DYNAMIC:
|
| 1426 | if (!nofp && func && !has_valid_stack_frame(&state)) {
|
| 1427 | WARN_FUNC("call without frame pointer save/setup",
|
| 1428 | sec, insn->offset);
|
| 1429 | return 1;
|
| 1430 | }
|
| 1431 | break;
|
| 1432 |
|
| 1433 | case INSN_JUMP_CONDITIONAL:
|
| 1434 | case INSN_JUMP_UNCONDITIONAL:
|
| 1435 | if (insn->jump_dest &&
|
| 1436 | (!func || !insn->jump_dest->func ||
|
| 1437 | func == insn->jump_dest->func)) {
|
| 1438 | ret = validate_branch(file, insn->jump_dest,
|
| 1439 | state);
|
| 1440 | if (ret)
|
| 1441 | return 1;
|
| 1442 |
|
| 1443 | } else if (func && has_modified_stack_frame(&state)) {
|
| 1444 | WARN_FUNC("sibling call from callable instruction with modified stack frame",
|
| 1445 | sec, insn->offset);
|
| 1446 | return 1;
|
| 1447 | }
|
| 1448 |
|
| 1449 | if (insn->type == INSN_JUMP_UNCONDITIONAL)
|
| 1450 | return 0;
|
| 1451 |
|
| 1452 | break;
|
| 1453 |
|
| 1454 | case INSN_JUMP_DYNAMIC:
|
| 1455 | if (func && list_empty(&insn->alts) &&
|
| 1456 | has_modified_stack_frame(&state)) {
|
| 1457 | WARN_FUNC("sibling call from callable instruction with modified stack frame",
|
| 1458 | sec, insn->offset);
|
| 1459 | return 1;
|
| 1460 | }
|
| 1461 |
|
| 1462 | return 0;
|
| 1463 |
|
| 1464 | case INSN_STACK:
|
| 1465 | if (update_insn_state(insn, &state))
|
| 1466 | return -1;
|
| 1467 |
|
| 1468 | break;
|
| 1469 |
|
| 1470 | default:
|
| 1471 | break;
|
| 1472 | }
|
| 1473 |
|
| 1474 | if (insn->dead_end)
|
| 1475 | return 0;
|
| 1476 |
|
| 1477 | insn = next_insn_same_sec(file, insn);
|
| 1478 | if (!insn) {
|
| 1479 | WARN("%s: unexpected end of section", sec->name);
|
| 1480 | return 1;
|
| 1481 | }
|
| 1482 | }
|
| 1483 |
|
| 1484 | return 0;
|
| 1485 | }
|
| 1486 |
|
| 1487 | static bool is_kasan_insn(struct instruction *insn)
|
| 1488 | {
|
| 1489 | return (insn->type == INSN_CALL &&
|
| 1490 | !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
|
| 1491 | }
|
| 1492 |
|
| 1493 | static bool is_ubsan_insn(struct instruction *insn)
|
| 1494 | {
|
| 1495 | return (insn->type == INSN_CALL &&
|
| 1496 | !strcmp(insn->call_dest->name,
|
| 1497 | "__ubsan_handle_builtin_unreachable"));
|
| 1498 | }
|
| 1499 |
|
| 1500 | static bool ignore_unreachable_insn(struct instruction *insn)
|
| 1501 | {
|
| 1502 | int i;
|
| 1503 |
|
| 1504 | if (insn->ignore || insn->type == INSN_NOP)
|
| 1505 | return true;
|
| 1506 |
|
| 1507 | |
| 1508 | * Ignore any unused exceptions. This can happen when a whitelisted
|
| 1509 | * function has an exception table entry.
|
| 1510 |
|
| 1511 | if (!strcmp(insn->sec->name, ".fixup"))
|
| 1512 | return true;
|
| 1513 |
|
| 1514 | |
| 1515 | * Check if this (or a subsequent) instruction is related to
|
| 1516 | * CONFIG_UBSAN or CONFIG_KASAN.
|
| 1517 | *
|
| 1518 | * End the search at 5 instructions to avoid going into the weeds.
|
| 1519 |
|
| 1520 | if (!insn->func)
|
| 1521 | return false;
|
| 1522 | for (i = 0; i < 5; i++) {
|
| 1523 |
|
| 1524 | if (is_kasan_insn(insn) || is_ubsan_insn(insn))
|
| 1525 | return true;
|
| 1526 |
|
| 1527 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
|
| 1528 | insn = insn->jump_dest;
|
| 1529 | continue;
|
| 1530 | }
|
| 1531 |
|
| 1532 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
|
| 1533 | break;
|
| 1534 | insn = list_next_entry(insn, list);
|
| 1535 | }
|
| 1536 |
|
| 1537 | return false;
|
| 1538 | }
|
| 1539 |
|
| 1540 | static int validate_functions(struct objtool_file *file)
|
| 1541 | {
|
| 1542 | struct section *sec;
|
| 1543 | struct symbol *func;
|
| 1544 | struct instruction *insn;
|
| 1545 | struct insn_state state;
|
| 1546 | int ret, warnings = 0;
|
| 1547 |
|
| 1548 | clear_insn_state(&state);
|
| 1549 |
|
| 1550 | state.cfa = initial_func_cfi.cfa;
|
| 1551 | memcpy(&state.regs, &initial_func_cfi.regs,
|
| 1552 | CFI_NUM_REGS * sizeof(struct cfi_reg));
|
| 1553 | state.stack_size = initial_func_cfi.cfa.offset;
|
| 1554 |
|
| 1555 | for_each_sec(file, sec) {
|
| 1556 | list_for_each_entry(func, &sec->symbol_list, list) {
|
| 1557 | if (func->type != STT_FUNC)
|
| 1558 | continue;
|
| 1559 |
|
| 1560 | insn = find_insn(file, sec, func->offset);
|
| 1561 | if (!insn || insn->ignore)
|
| 1562 | continue;
|
| 1563 |
|
| 1564 | ret = validate_branch(file, insn, state);
|
| 1565 | warnings += ret;
|
| 1566 | }
|
| 1567 | }
|
| 1568 |
|
| 1569 | return warnings;
|
| 1570 | }
|
| 1571 |
|
| 1572 | static int validate_reachable_instructions(struct objtool_file *file)
|
| 1573 | {
|
| 1574 | struct instruction *insn;
|
| 1575 |
|
| 1576 | if (file->ignore_unreachables)
|
| 1577 | return 0;
|
| 1578 |
|
| 1579 | for_each_insn(file, insn) {
|
| 1580 | if (insn->visited || ignore_unreachable_insn(insn))
|
| 1581 | continue;
|
| 1582 |
|
| 1583 | |
| 1584 | * gcov produces a lot of unreachable instructions. If we get
|
| 1585 | * an unreachable warning and the file has gcov enabled, just
|
| 1586 | * ignore it, and all other such warnings for the file. Do
|
| 1587 | * this here because this is an expensive function.
|
| 1588 |
|
| 1589 | if (gcov_enabled(file))
|
| 1590 | return 0;
|
| 1591 |
|
| 1592 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
|
| 1593 | return 1;
|
| 1594 | }
|
| 1595 |
|
| 1596 | return 0;
|
| 1597 | }
|
| 1598 |
|
| 1599 | static void cleanup(struct objtool_file *file)
|
| 1600 | {
|
| 1601 | struct instruction *insn, *tmpinsn;
|
| 1602 | struct alternative *alt, *tmpalt;
|
| 1603 |
|
| 1604 | list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
|
| 1605 | list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
|
| 1606 | list_del(&alt->list);
|
| 1607 | free(alt);
|
| 1608 | }
|
| 1609 | list_del(&insn->list);
|
| 1610 | hash_del(&insn->hash);
|
| 1611 | free(insn);
|
| 1612 | }
|
| 1613 | elf_close(file->elf);
|
| 1614 | }
|
| 1615 |
|
| 1616 | int check(const char *_objname, bool _nofp)
|
| 1617 | {
|
| 1618 | struct objtool_file file;
|
| 1619 | int ret, warnings = 0;
|
| 1620 |
|
| 1621 | objname = _objname;
|
| 1622 | nofp = _nofp;
|
| 1623 |
|
| 1624 | file.elf = elf_open(objname);
|
| 1625 | if (!file.elf)
|
| 1626 | return 1;
|
| 1627 |
|
| 1628 | INIT_LIST_HEAD(&file.insn_list);
|
| 1629 | hash_init(file.insn_hash);
|
| 1630 | file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
|
| 1631 | file.rodata = find_section_by_name(file.elf, ".rodata");
|
| 1632 | file.ignore_unreachables = false;
|
| 1633 | file.c_file = find_section_by_name(file.elf, ".comment");
|
| 1634 |
|
| 1635 | arch_initial_func_cfi_state(&initial_func_cfi);
|
| 1636 |
|
| 1637 | ret = decode_sections(&file);
|
| 1638 | if (ret < 0)
|
| 1639 | goto out;
|
| 1640 | warnings += ret;
|
| 1641 |
|
| 1642 | if (list_empty(&file.insn_list))
|
| 1643 | goto out;
|
| 1644 |
|
| 1645 | ret = validate_functions(&file);
|
| 1646 | if (ret < 0)
|
| 1647 | goto out;
|
| 1648 | warnings += ret;
|
| 1649 |
|
| 1650 | if (!warnings) {
|
| 1651 | ret = validate_reachable_instructions(&file);
|
| 1652 | if (ret < 0)
|
| 1653 | goto out;
|
| 1654 | warnings += ret;
|
| 1655 | }
|
| 1656 |
|
| 1657 | out:
|
| 1658 | cleanup(&file);
|
| 1659 |
|
| 1660 |
|
| 1661 | if (ret || warnings)
|
| 1662 | return 0;
|
| 1663 | return 0;
|
| 1664 | }
|