--- /dev/null
+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * objtool check:
+ *
+ * This command analyzes every .o file and ensures the validity of its stack
+ * trace metadata. It enforces a set of rules on asm code and C inline
+ * assembly code so that stack traces can be reliable.
+ *
+ * For more information, see tools/objtool/Documentation/stack-validation.txt.
+ */
+
+#include <string.h>
+#include <subcmd/parse-options.h>
+
+#include "builtin.h"
+#include "elf.h"
+#include "special.h"
+#include "arch.h"
+#include "warn.h"
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+#define STATE_FP_SAVED 0x1
+#define STATE_FP_SETUP 0x2
+#define STATE_FENTRY 0x4
+
+struct instruction {
+ struct list_head list;
+ struct section *sec;
+ unsigned long offset;
+ unsigned int len, state;
+ unsigned char type;
+ unsigned long immediate;
+ bool alt_group, visited;
+ struct symbol *call_dest;
+ struct instruction *jump_dest;
+ struct list_head alts;
+};
+
+struct alternative {
+ struct list_head list;
+ struct instruction *insn;
+};
+
+struct objtool_file {
+ struct elf *elf;
+ struct list_head insns;
+};
+
+const char *objname;
+static bool nofp;
+
+static struct instruction *find_instruction(struct objtool_file *file,
+ struct section *sec,
+ unsigned long offset)
+{
+ struct instruction *insn;
+
+ list_for_each_entry(insn, &file->insns, list)
+ if (insn->sec == sec && insn->offset == offset)
+ return insn;
+
+ return NULL;
+}
+
+/*
+ * Check if the function has been manually whitelisted with the
+ * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
+ * due to its use of a context switching instruction.
+ */
+static bool ignore_func(struct objtool_file *file, struct symbol *func)
+{
+ struct section *macro_sec;
+ struct rela *rela;
+ struct instruction *insn;
+
+ /* check for STACK_FRAME_NON_STANDARD */
+ macro_sec = find_section_by_name(file->elf, "__func_stack_frame_non_standard");
+ if (macro_sec && macro_sec->rela)
+ list_for_each_entry(rela, ¯o_sec->rela->relas, list)
+ if (rela->sym->sec == func->sec &&
+ rela->addend == func->offset)
+ return true;
+
+ /* check if it has a context switching instruction */
+ insn = find_instruction(file, func->sec, func->offset);
+ if (!insn)
+ return false;
+ list_for_each_entry_from(insn, &file->insns, list) {
+ if (insn->sec != func->sec ||
+ insn->offset >= func->offset + func->len)
+ break;
+ if (insn->type == INSN_CONTEXT_SWITCH)
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * This checks to see if the given function is a "noreturn" function.
+ *
+ * For global functions which are outside the scope of this object file, we
+ * have to keep a manual list of them.
+ *
+ * For local functions, we have to detect them manually by simply looking for
+ * the lack of a return instruction.
+ */
+static bool dead_end_function(struct objtool_file *file, struct symbol *func)
+{
+ int i;
+ struct instruction *insn;
+ bool empty = true;
+
+ /*
+ * Unfortunately these have to be hard coded because the noreturn
+ * attribute isn't provided in ELF data.
+ */
+ static const char * const global_noreturns[] = {
+ "__stack_chk_fail",
+ "panic",
+ "do_exit",
+ "__module_put_and_exit",
+ "complete_and_exit",
+ "kvm_spurious_fault",
+ "__reiserfs_panic",
+ "lbug_with_loc"
+ };
+
+ if (func->bind == STB_WEAK)
+ return false;
+
+ if (func->bind == STB_GLOBAL)
+ for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
+ if (!strcmp(func->name, global_noreturns[i]))
+ return true;
+
+ if (!func->sec)
+ return false;
+
+ insn = find_instruction(file, func->sec, func->offset);
+ if (!insn)
+ return false;
+
+ list_for_each_entry_from(insn, &file->insns, list) {
+ if (insn->sec != func->sec ||
+ insn->offset >= func->offset + func->len)
+ break;
+
+ empty = false;
+
+ if (insn->type == INSN_RETURN)
+ return false;
+
+ if (insn->type == INSN_JUMP_UNCONDITIONAL) {
+ struct instruction *dest = insn->jump_dest;
+ struct symbol *dest_func;
+
+ if (!dest)
+ /* sibling call to another file */
+ return false;
+
+ if (dest->sec != func->sec ||
+ dest->offset < func->offset ||
+ dest->offset >= func->offset + func->len) {
+ /* local sibling call */
+ dest_func = find_symbol_by_offset(dest->sec,
+ dest->offset);
+ if (!dest_func)
+ continue;
+
+ return dead_end_function(file, dest_func);
+ }
+ }
+
+ if (insn->type == INSN_JUMP_DYNAMIC)
+ /* sibling call */
+ return false;
+ }
+
+ return !empty;
+}
+
+/*
+ * Call the arch-specific instruction decoder for all the instructions and add
+ * them to the global insns list.
+ */
+static int decode_instructions(struct objtool_file *file)
+{
+ struct section *sec;
+ unsigned long offset;
+ struct instruction *insn;
+ int ret;
+
+ INIT_LIST_HEAD(&file->insns);
+
+ list_for_each_entry(sec, &file->elf->sections, list) {
+
+ if (!(sec->sh.sh_flags & SHF_EXECINSTR))
+ continue;
+
+ for (offset = 0; offset < sec->len; offset += insn->len) {
+ insn = malloc(sizeof(*insn));
+ memset(insn, 0, sizeof(*insn));
+
+ INIT_LIST_HEAD(&insn->alts);
+ insn->sec = sec;
+ insn->offset = offset;
+
+ ret = arch_decode_instruction(file->elf, sec, offset,
+ sec->len - offset,
+ &insn->len, &insn->type,
+ &insn->immediate);
+ if (ret)
+ return ret;
+
+ if (!insn->type || insn->type > INSN_LAST) {
+ WARN_FUNC("invalid instruction type %d",
+ insn->sec, insn->offset, insn->type);
+ return -1;
+ }
+
+ list_add_tail(&insn->list, &file->insns);
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Warnings shouldn't be reported for ignored functions.
+ */
+static void get_ignores(struct objtool_file *file)
+{
+ struct instruction *insn;
+ struct section *sec;
+ struct symbol *func;
+
+ list_for_each_entry(sec, &file->elf->sections, list) {
+ list_for_each_entry(func, &sec->symbols, list) {
+ if (func->type != STT_FUNC)
+ continue;
+
+ if (!ignore_func(file, func))
+ continue;
+
+ insn = find_instruction(file, sec, func->offset);
+ if (!insn)
+ continue;
+
+ list_for_each_entry_from(insn, &file->insns, list) {
+ if (insn->sec != func->sec ||
+ insn->offset >= func->offset + func->len)
+ break;
+
+ insn->visited = true;
+ }
+ }
+ }
+}
+
+/*
+ * Find the destination instructions for all jumps.
+ */
+static int get_jump_destinations(struct objtool_file *file)
+{
+ struct instruction *insn;
+ struct rela *rela;
+ struct section *dest_sec;
+ unsigned long dest_off;
+
+ list_for_each_entry(insn, &file->insns, list) {
+ if (insn->type != INSN_JUMP_CONDITIONAL &&
+ insn->type != INSN_JUMP_UNCONDITIONAL)
+ continue;
+
+ /* skip ignores */
+ if (insn->visited)
+ continue;
+
+ rela = find_rela_by_dest_range(insn->sec, insn->offset,
+ insn->len);
+ if (!rela) {
+ dest_sec = insn->sec;
+ dest_off = insn->offset + insn->len + insn->immediate;
+ } else if (rela->sym->type == STT_SECTION) {
+ dest_sec = rela->sym->sec;
+ dest_off = rela->addend + 4;
+ } else if (rela->sym->sec->idx) {
+ dest_sec = rela->sym->sec;
+ dest_off = rela->sym->sym.st_value + rela->addend + 4;
+ } else {
+ /* sibling call */
+ insn->jump_dest = 0;
+ continue;
+ }
+
+ insn->jump_dest = find_instruction(file, dest_sec, dest_off);
+ if (!insn->jump_dest) {
+
+ /*
+ * This is a special case where an alt instruction
+ * jumps past the end of the section. These are
+ * handled later in handle_group_alt().
+ */
+ if (!strcmp(insn->sec->name, ".altinstr_replacement"))
+ continue;
+
+ WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
+ insn->sec, insn->offset, dest_sec->name,
+ dest_off);
+ return -1;
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Find the destination instructions for all calls.
+ */
+static int get_call_destinations(struct objtool_file *file)
+{
+ struct instruction *insn;
+ unsigned long dest_off;
+ struct rela *rela;
+
+ list_for_each_entry(insn, &file->insns, list) {
+ if (insn->type != INSN_CALL)
+ continue;
+
+ rela = find_rela_by_dest_range(insn->sec, insn->offset,
+ insn->len);
+ if (!rela) {
+ dest_off = insn->offset + insn->len + insn->immediate;
+ insn->call_dest = find_symbol_by_offset(insn->sec,
+ dest_off);
+ if (!insn->call_dest) {
+ WARN_FUNC("can't find call dest symbol at offset 0x%lx",
+ insn->sec, insn->offset, dest_off);
+ return -1;
+ }
+ } else if (rela->sym->type == STT_SECTION) {
+ insn->call_dest = find_symbol_by_offset(rela->sym->sec,
+ rela->addend+4);
+ if (!insn->call_dest ||
+ insn->call_dest->type != STT_FUNC) {
+ WARN_FUNC("can't find call dest symbol at %s+0x%x",
+ insn->sec, insn->offset,
+ rela->sym->sec->name,
+ rela->addend + 4);
+ return -1;
+ }
+ } else
+ insn->call_dest = rela->sym;
+ }
+
+ return 0;
+}
+
+/*
+ * The .alternatives section requires some extra special care, over and above
+ * what other special sections require:
+ *
+ * 1. Because alternatives are patched in-place, we need to insert a fake jump
+ * instruction at the end so that validate_branch() skips all the original
+ * replaced instructions when validating the new instruction path.
+ *
+ * 2. An added wrinkle is that the new instruction length might be zero. In
+ * that case the old instructions are replaced with noops. We simulate that
+ * by creating a fake jump as the only new instruction.
+ *
+ * 3. In some cases, the alternative section includes an instruction which
+ * conditionally jumps to the _end_ of the entry. We have to modify these
+ * jumps' destinations to point back to .text rather than the end of the
+ * entry in .altinstr_replacement.
+ *
+ * 4. It has been requested that we don't validate the !POPCNT feature path
+ * which is a "very very small percentage of machines".
+ */
+static int handle_group_alt(struct objtool_file *file,
+ struct special_alt *special_alt,
+ struct instruction *orig_insn,
+ struct instruction **new_insn)
+{
+ struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
+ unsigned long dest_off;
+
+ last_orig_insn = NULL;
+ insn = orig_insn;
+ list_for_each_entry_from(insn, &file->insns, list) {
+ if (insn->sec != special_alt->orig_sec ||
+ insn->offset >= special_alt->orig_off + special_alt->orig_len)
+ break;
+
+ if (special_alt->skip_orig)
+ insn->type = INSN_NOP;
+
+ insn->alt_group = true;
+ last_orig_insn = insn;
+ }
+
+ if (list_is_last(&last_orig_insn->list, &file->insns) ||
+ list_next_entry(last_orig_insn, list)->sec != special_alt->orig_sec) {
+ WARN("%s: don't know how to handle alternatives at end of section",
+ special_alt->orig_sec->name);
+ return -1;
+ }
+
+ fake_jump = malloc(sizeof(*fake_jump));
+ if (!fake_jump) {
+ WARN("malloc failed");
+ return -1;
+ }
+ memset(fake_jump, 0, sizeof(*fake_jump));
+ INIT_LIST_HEAD(&fake_jump->alts);
+ fake_jump->sec = special_alt->new_sec;
+ fake_jump->offset = -1;
+ fake_jump->type = INSN_JUMP_UNCONDITIONAL;
+ fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
+
+ if (!special_alt->new_len) {
+ *new_insn = fake_jump;
+ return 0;
+ }
+
+ last_new_insn = NULL;
+ insn = *new_insn;
+ list_for_each_entry_from(insn, &file->insns, list) {
+ if (insn->sec != special_alt->new_sec ||
+ insn->offset >= special_alt->new_off + special_alt->new_len)
+ break;
+
+ last_new_insn = insn;
+
+ if (insn->type != INSN_JUMP_CONDITIONAL &&
+ insn->type != INSN_JUMP_UNCONDITIONAL)
+ continue;
+
+ if (!insn->immediate)
+ continue;
+
+ dest_off = insn->offset + insn->len + insn->immediate;
+ if (dest_off == special_alt->new_off + special_alt->new_len)
+ insn->jump_dest = fake_jump;
+
+ if (!insn->jump_dest) {
+ WARN_FUNC("can't find alternative jump destination",
+ insn->sec, insn->offset);
+ return -1;
+ }
+ }
+
+ if (!last_new_insn) {
+ WARN_FUNC("can't find last new alternative instruction",
+ special_alt->new_sec, special_alt->new_off);
+ return -1;
+ }
+
+ list_add(&fake_jump->list, &last_new_insn->list);
+
+ return 0;
+}
+
+/*
+ * A jump table entry can either convert a nop to a jump or a jump to a nop.
+ * If the original instruction is a jump, make the alt entry an effective nop
+ * by just skipping the original instruction.
+ */
+static int handle_jump_alt(struct objtool_file *file,
+ struct special_alt *special_alt,
+ struct instruction *orig_insn,
+ struct instruction **new_insn)
+{
+ if (orig_insn->type == INSN_NOP)
+ return 0;
+
+ if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
+ WARN_FUNC("unsupported instruction at jump label",
+ orig_insn->sec, orig_insn->offset);
+ return -1;
+ }
+
+ *new_insn = list_next_entry(orig_insn, list);
+ return 0;
+}
+
+/*
+ * Read all the special sections which have alternate instructions which can be
+ * patched in or redirected to at runtime. Each instruction having alternate
+ * instruction(s) has them added to its insn->alts list, which will be
+ * traversed in validate_branch().
+ */
+static int get_special_section_alts(struct objtool_file *file)
+{
+ struct list_head special_alts;
+ struct instruction *orig_insn, *new_insn;
+ struct special_alt *special_alt, *tmp;
+ struct alternative *alt;
+ int ret;
+
+ ret = special_get_alts(file->elf, &special_alts);
+ if (ret)
+ return ret;
+
+ list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
+ alt = malloc(sizeof(*alt));
+ if (!alt) {
+ WARN("malloc failed");
+ ret = -1;
+ goto out;
+ }
+
+ orig_insn = find_instruction(file, special_alt->orig_sec,
+ special_alt->orig_off);
+ if (!orig_insn) {
+ WARN_FUNC("special: can't find orig instruction",
+ special_alt->orig_sec, special_alt->orig_off);
+ ret = -1;
+ goto out;
+ }
+
+ new_insn = NULL;
+ if (!special_alt->group || special_alt->new_len) {
+ new_insn = find_instruction(file, special_alt->new_sec,
+ special_alt->new_off);
+ if (!new_insn) {
+ WARN_FUNC("special: can't find new instruction",
+ special_alt->new_sec,
+ special_alt->new_off);
+ ret = -1;
+ goto out;
+ }
+ }
+
+ if (special_alt->group) {
+ ret = handle_group_alt(file, special_alt, orig_insn,
+ &new_insn);
+ if (ret)
+ goto out;
+ } else if (special_alt->jump_or_nop) {
+ ret = handle_jump_alt(file, special_alt, orig_insn,
+ &new_insn);
+ if (ret)
+ goto out;
+ }
+
+ alt->insn = new_insn;
+ list_add_tail(&alt->list, &orig_insn->alts);
+
+ list_del(&special_alt->list);
+ free(special_alt);
+ }
+
+out:
+ return ret;
+}
+
+/*
+ * For some switch statements, gcc generates a jump table in the .rodata
+ * section which contains a list of addresses within the function to jump to.
+ * This finds these jump tables and adds them to the insn->alts lists.
+ */
+static int get_switch_alts(struct objtool_file *file)
+{
+ struct instruction *insn, *alt_insn;
+ struct rela *rodata_rela, *rela;
+ struct section *rodata;
+ struct symbol *func;
+ struct alternative *alt;
+
+ list_for_each_entry(insn, &file->insns, list) {
+ if (insn->type != INSN_JUMP_DYNAMIC)
+ continue;
+
+ rodata_rela = find_rela_by_dest_range(insn->sec, insn->offset,
+ insn->len);
+ if (!rodata_rela || strcmp(rodata_rela->sym->name, ".rodata"))
+ continue;
+
+ rodata = find_section_by_name(file->elf, ".rodata");
+ if (!rodata || !rodata->rela)
+ continue;
+
+ /* common case: jmpq *[addr](,%rax,8) */
+ rela = find_rela_by_dest(rodata, rodata_rela->addend);
+
+ /* rare case: jmpq *[addr](%rip) */
+ if (!rela)
+ rela = find_rela_by_dest(rodata,
+ rodata_rela->addend + 4);
+ if (!rela)
+ continue;
+
+ func = find_containing_func(insn->sec, insn->offset);
+ if (!func) {
+ WARN_FUNC("can't find containing func",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ list_for_each_entry_from(rela, &rodata->rela->relas, list) {
+ if (rela->sym->sec != insn->sec ||
+ rela->addend <= func->offset ||
+ rela->addend >= func->offset + func->len)
+ break;
+
+ alt_insn = find_instruction(file, insn->sec,
+ rela->addend);
+ if (!alt_insn) {
+ WARN("%s: can't find instruction at %s+0x%x",
+ rodata->rela->name, insn->sec->name,
+ rela->addend);
+ return -1;
+ }
+
+ alt = malloc(sizeof(*alt));
+ if (!alt) {
+ WARN("malloc failed");
+ return -1;
+ }
+
+ alt->insn = alt_insn;
+ list_add_tail(&alt->list, &insn->alts);
+ }
+ }
+
+ return 0;
+}
+
+static int decode_sections(struct objtool_file *file)
+{
+ int ret;
+
+ ret = decode_instructions(file);
+ if (ret)
+ return ret;
+
+ get_ignores(file);
+
+ ret = get_jump_destinations(file);
+ if (ret)
+ return ret;
+
+ ret = get_call_destinations(file);
+ if (ret)
+ return ret;
+
+ ret = get_special_section_alts(file);
+ if (ret)
+ return ret;
+
+ ret = get_switch_alts(file);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
+static bool is_fentry_call(struct instruction *insn)
+{
+ if (insn->type == INSN_CALL &&
+ insn->call_dest->type == STT_NOTYPE &&
+ !strcmp(insn->call_dest->name, "__fentry__"))
+ return true;
+
+ return false;
+}
+
+static bool has_modified_stack_frame(struct instruction *insn)
+{
+ return (insn->state & STATE_FP_SAVED) ||
+ (insn->state & STATE_FP_SETUP);
+}
+
+static bool has_valid_stack_frame(struct instruction *insn)
+{
+ return (insn->state & STATE_FP_SAVED) &&
+ (insn->state & STATE_FP_SETUP);
+}
+
+/*
+ * Follow the branch starting at the given instruction, and recursively follow
+ * any other branches (jumps). Meanwhile, track the frame pointer state at
+ * each instruction and validate all the rules described in
+ * tools/objtool/Documentation/stack-validation.txt.
+ */
+static int validate_branch(struct objtool_file *file,
+ struct instruction *first, unsigned char first_state)
+{
+ struct alternative *alt;
+ struct instruction *insn;
+ struct section *sec;
+ unsigned char state;
+ int ret, warnings = 0;
+
+ insn = first;
+ sec = insn->sec;
+ state = first_state;
+
+ if (insn->alt_group && list_empty(&insn->alts)) {
+ WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
+ sec, insn->offset);
+ warnings++;
+ }
+
+ while (1) {
+ if (insn->visited) {
+ if (insn->state != state) {
+ WARN_FUNC("frame pointer state mismatch",
+ sec, insn->offset);
+ warnings++;
+ }
+
+ return warnings;
+ }
+
+ /*
+ * Catch a rare case where a noreturn function falls through to
+ * the next function.
+ */
+ if (is_fentry_call(insn) && (state & STATE_FENTRY))
+ return warnings;
+
+ insn->visited = true;
+ insn->state = state;
+
+ list_for_each_entry(alt, &insn->alts, list) {
+ ret = validate_branch(file, alt->insn, state);
+ warnings += ret;
+ }
+
+ switch (insn->type) {
+
+ case INSN_FP_SAVE:
+ if (!nofp) {
+ if (state & STATE_FP_SAVED) {
+ WARN_FUNC("duplicate frame pointer save",
+ sec, insn->offset);
+ warnings++;
+ }
+ state |= STATE_FP_SAVED;
+ }
+ break;
+
+ case INSN_FP_SETUP:
+ if (!nofp) {
+ if (state & STATE_FP_SETUP) {
+ WARN_FUNC("duplicate frame pointer setup",
+ sec, insn->offset);
+ warnings++;
+ }
+ state |= STATE_FP_SETUP;
+ }
+ break;
+
+ case INSN_FP_RESTORE:
+ if (!nofp) {
+ if (has_valid_stack_frame(insn))
+ state &= ~STATE_FP_SETUP;
+
+ state &= ~STATE_FP_SAVED;
+ }
+ break;
+
+ case INSN_RETURN:
+ if (!nofp && has_modified_stack_frame(insn)) {
+ WARN_FUNC("return without frame pointer restore",
+ sec, insn->offset);
+ warnings++;
+ }
+ return warnings;
+
+ case INSN_CALL:
+ if (is_fentry_call(insn)) {
+ state |= STATE_FENTRY;
+ break;
+ }
+
+ if (dead_end_function(file, insn->call_dest))
+ return warnings;
+
+ /* fallthrough */
+ case INSN_CALL_DYNAMIC:
+ if (!nofp && !has_valid_stack_frame(insn)) {
+ WARN_FUNC("call without frame pointer save/setup",
+ sec, insn->offset);
+ warnings++;
+ }
+ break;
+
+ case INSN_JUMP_CONDITIONAL:
+ case INSN_JUMP_UNCONDITIONAL:
+ if (insn->jump_dest) {
+ ret = validate_branch(file, insn->jump_dest,
+ state);
+ warnings += ret;
+ } else if (has_modified_stack_frame(insn)) {
+ WARN_FUNC("sibling call from callable instruction with changed frame pointer",
+ sec, insn->offset);
+ warnings++;
+ } /* else it's a sibling call */
+
+ if (insn->type == INSN_JUMP_UNCONDITIONAL)
+ return warnings;
+
+ break;
+
+ case INSN_JUMP_DYNAMIC:
+ if (list_empty(&insn->alts) &&
+ has_modified_stack_frame(insn)) {
+ WARN_FUNC("sibling call from callable instruction with changed frame pointer",
+ sec, insn->offset);
+ warnings++;
+ }
+
+ return warnings;
+
+ case INSN_BUG:
+ return warnings;
+
+ default:
+ break;
+ }
+
+ insn = list_next_entry(insn, list);
+
+ if (&insn->list == &file->insns || insn->sec != sec) {
+ WARN("%s: unexpected end of section", sec->name);
+ warnings++;
+ return warnings;
+ }
+ }
+
+ return warnings;
+}
+
+static bool is_gcov_insn(struct instruction *insn)
+{
+ struct rela *rela;
+ struct section *sec;
+ struct symbol *sym;
+ unsigned long offset;
+
+ rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
+ if (!rela)
+ return false;
+
+ if (rela->sym->type != STT_SECTION)
+ return false;
+
+ sec = rela->sym->sec;
+ offset = rela->addend + insn->offset + insn->len - rela->offset;
+
+ list_for_each_entry(sym, &sec->symbols, list) {
+ if (sym->type != STT_OBJECT)
+ continue;
+
+ if (offset >= sym->offset && offset < sym->offset + sym->len)
+ return (!memcmp(sym->name, "__gcov0.", 8));
+ }
+
+ return false;
+}
+
+static bool is_kasan_insn(struct instruction *insn)
+{
+ return (insn->type == INSN_CALL &&
+ !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
+}
+
+static bool is_ubsan_insn(struct instruction *insn)
+{
+ return (insn->type == INSN_CALL &&
+ !strcmp(insn->call_dest->name,
+ "__ubsan_handle_builtin_unreachable"));
+}
+
+static bool ignore_unreachable_insn(struct instruction *insn,
+ unsigned long func_end)
+{
+ int i;
+
+ if (insn->type == INSN_NOP)
+ return true;
+
+ if (is_gcov_insn(insn))
+ return true;
+
+ /*
+ * Check if this (or a subsequent) instruction is related to
+ * CONFIG_UBSAN or CONFIG_KASAN.
+ *
+ * End the search at 5 instructions to avoid going into the weeds.
+ */
+ for (i = 0; i < 5; i++) {
+
+ if (is_kasan_insn(insn) || is_ubsan_insn(insn))
+ return true;
+
+ if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
+ insn = insn->jump_dest;
+ continue;
+ }
+
+ if (insn->offset + insn->len >= func_end)
+ break;
+ insn = list_next_entry(insn, list);
+ }
+
+ return false;
+}
+
+static int validate_functions(struct objtool_file *file)
+{
+ struct section *sec;
+ struct symbol *func;
+ struct instruction *insn;
+ unsigned long func_end;
+ int ret, warnings = 0;
+
+ list_for_each_entry(sec, &file->elf->sections, list) {
+ list_for_each_entry(func, &sec->symbols, list) {
+ if (func->type != STT_FUNC)
+ continue;
+
+ insn = find_instruction(file, sec, func->offset);
+ if (!insn) {
+ WARN("%s(): can't find starting instruction",
+ func->name);
+ warnings++;
+ continue;
+ }
+
+ ret = validate_branch(file, insn, 0);
+ warnings += ret;
+ }
+ }
+
+ list_for_each_entry(sec, &file->elf->sections, list) {
+ list_for_each_entry(func, &sec->symbols, list) {
+ if (func->type != STT_FUNC)
+ continue;
+
+ insn = find_instruction(file, sec, func->offset);
+ if (!insn)
+ continue;
+
+ func_end = func->offset + func->len;
+
+ list_for_each_entry_from(insn, &file->insns, list) {
+ if (insn->sec != func->sec ||
+ insn->offset >= func_end)
+ break;
+
+ if (insn->visited)
+ continue;
+
+ if (!ignore_unreachable_insn(insn, func_end)) {
+ WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset);
+ warnings++;
+ }
+
+ insn->visited = true;
+ }
+ }
+ }
+
+ return warnings;
+}
+
+static int validate_uncallable_instructions(struct objtool_file *file)
+{
+ struct instruction *insn;
+ int warnings = 0;
+
+ list_for_each_entry(insn, &file->insns, list) {
+ if (!insn->visited && insn->type == INSN_RETURN) {
+ WARN_FUNC("return instruction outside of a callable function",
+ insn->sec, insn->offset);
+ warnings++;
+ }
+ }
+
+ return warnings;
+}
+
+static void cleanup(struct objtool_file *file)
+{
+ struct instruction *insn, *tmpinsn;
+ struct alternative *alt, *tmpalt;
+
+ list_for_each_entry_safe(insn, tmpinsn, &file->insns, list) {
+ list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
+ list_del(&alt->list);
+ free(alt);
+ }
+ list_del(&insn->list);
+ free(insn);
+ }
+ elf_close(file->elf);
+}
+
+const char * const check_usage[] = {
+ "objtool check [<options>] file.o",
+ NULL,
+};
+
+int cmd_check(int argc, const char **argv)
+{
+ struct objtool_file file;
+ int ret, warnings = 0;
+
+ const struct option options[] = {
+ OPT_BOOLEAN('f', "no-fp", &nofp, "Skip frame pointer validation"),
+ OPT_END(),
+ };
+
+ argc = parse_options(argc, argv, options, check_usage, 0);
+
+ if (argc != 1)
+ usage_with_options(check_usage, options);
+
+ objname = argv[0];
+
+ file.elf = elf_open(objname);
+ if (!file.elf) {
+ fprintf(stderr, "error reading elf file %s\n", objname);
+ return 1;
+ }
+
+ INIT_LIST_HEAD(&file.insns);
+
+ ret = decode_sections(&file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+
+ ret = validate_functions(&file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+
+ ret = validate_uncallable_instructions(&file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+
+out:
+ cleanup(&file);
+
+ /* ignore warnings for now until we get all the code cleaned up */
+ if (ret || warnings)
+ return 0;
+ return 0;
+}
projects / cascardo / linux.git / blobdiff