mirror of https://gitee.com/openkylin/linux.git
2822 lines
67 KiB
C
2822 lines
67 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
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*/
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#include <string.h>
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#include <stdlib.h>
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#include "builtin.h"
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#include "cfi.h"
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#include "arch.h"
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#include "check.h"
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#include "special.h"
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#include "warn.h"
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#include <linux/hashtable.h>
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#include <linux/kernel.h>
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#define FAKE_JUMP_OFFSET -1
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#define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
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struct alternative {
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struct list_head list;
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struct instruction *insn;
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bool skip_orig;
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};
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const char *objname;
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struct cfi_init_state initial_func_cfi;
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struct instruction *find_insn(struct objtool_file *file,
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struct section *sec, unsigned long offset)
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{
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struct instruction *insn;
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hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
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if (insn->sec == sec && insn->offset == offset)
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return insn;
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}
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return NULL;
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}
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static struct instruction *next_insn_same_sec(struct objtool_file *file,
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struct instruction *insn)
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{
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struct instruction *next = list_next_entry(insn, list);
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if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
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return NULL;
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return next;
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}
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static struct instruction *next_insn_same_func(struct objtool_file *file,
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struct instruction *insn)
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{
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struct instruction *next = list_next_entry(insn, list);
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struct symbol *func = insn->func;
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if (!func)
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return NULL;
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if (&next->list != &file->insn_list && next->func == func)
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return next;
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/* Check if we're already in the subfunction: */
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if (func == func->cfunc)
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return NULL;
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/* Move to the subfunction: */
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return find_insn(file, func->cfunc->sec, func->cfunc->offset);
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}
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static struct instruction *prev_insn_same_sym(struct objtool_file *file,
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struct instruction *insn)
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{
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struct instruction *prev = list_prev_entry(insn, list);
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if (&prev->list != &file->insn_list && prev->func == insn->func)
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return prev;
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return NULL;
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}
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#define func_for_each_insn(file, func, insn) \
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for (insn = find_insn(file, func->sec, func->offset); \
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insn; \
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insn = next_insn_same_func(file, insn))
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#define sym_for_each_insn(file, sym, insn) \
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for (insn = find_insn(file, sym->sec, sym->offset); \
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insn && &insn->list != &file->insn_list && \
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insn->sec == sym->sec && \
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insn->offset < sym->offset + sym->len; \
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insn = list_next_entry(insn, list))
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#define sym_for_each_insn_continue_reverse(file, sym, insn) \
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for (insn = list_prev_entry(insn, list); \
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&insn->list != &file->insn_list && \
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insn->sec == sym->sec && insn->offset >= sym->offset; \
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insn = list_prev_entry(insn, list))
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#define sec_for_each_insn_from(file, insn) \
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for (; insn; insn = next_insn_same_sec(file, insn))
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#define sec_for_each_insn_continue(file, insn) \
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for (insn = next_insn_same_sec(file, insn); insn; \
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insn = next_insn_same_sec(file, insn))
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static bool is_static_jump(struct instruction *insn)
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{
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return insn->type == INSN_JUMP_CONDITIONAL ||
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insn->type == INSN_JUMP_UNCONDITIONAL;
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}
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static bool is_sibling_call(struct instruction *insn)
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{
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/* An indirect jump is either a sibling call or a jump to a table. */
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if (insn->type == INSN_JUMP_DYNAMIC)
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return list_empty(&insn->alts);
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if (!is_static_jump(insn))
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return false;
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/* add_jump_destinations() sets insn->call_dest for sibling calls. */
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return !!insn->call_dest;
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}
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/*
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* This checks to see if the given function is a "noreturn" function.
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*
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* For global functions which are outside the scope of this object file, we
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* have to keep a manual list of them.
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*
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* For local functions, we have to detect them manually by simply looking for
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* the lack of a return instruction.
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*/
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static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
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int recursion)
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{
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int i;
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struct instruction *insn;
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bool empty = true;
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/*
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* Unfortunately these have to be hard coded because the noreturn
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* attribute isn't provided in ELF data.
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*/
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static const char * const global_noreturns[] = {
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"__stack_chk_fail",
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"panic",
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"do_exit",
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"do_task_dead",
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"__module_put_and_exit",
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"complete_and_exit",
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"__reiserfs_panic",
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"lbug_with_loc",
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"fortify_panic",
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"usercopy_abort",
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"machine_real_restart",
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"rewind_stack_do_exit",
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"kunit_try_catch_throw",
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};
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if (!func)
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return false;
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if (func->bind == STB_WEAK)
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return false;
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if (func->bind == STB_GLOBAL)
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for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
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if (!strcmp(func->name, global_noreturns[i]))
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return true;
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if (!func->len)
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return false;
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insn = find_insn(file, func->sec, func->offset);
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if (!insn->func)
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return false;
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func_for_each_insn(file, func, insn) {
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empty = false;
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if (insn->type == INSN_RETURN)
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return false;
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}
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if (empty)
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return false;
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/*
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* A function can have a sibling call instead of a return. In that
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* case, the function's dead-end status depends on whether the target
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* of the sibling call returns.
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*/
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func_for_each_insn(file, func, insn) {
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if (is_sibling_call(insn)) {
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struct instruction *dest = insn->jump_dest;
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if (!dest)
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/* sibling call to another file */
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return false;
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/* local sibling call */
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if (recursion == 5) {
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/*
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* Infinite recursion: two functions have
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* sibling calls to each other. This is a very
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* rare case. It means they aren't dead ends.
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*/
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return false;
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}
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return __dead_end_function(file, dest->func, recursion+1);
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}
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}
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return true;
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}
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static bool dead_end_function(struct objtool_file *file, struct symbol *func)
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{
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return __dead_end_function(file, func, 0);
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}
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static void init_cfi_state(struct cfi_state *cfi)
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{
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int i;
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for (i = 0; i < CFI_NUM_REGS; i++) {
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cfi->regs[i].base = CFI_UNDEFINED;
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cfi->vals[i].base = CFI_UNDEFINED;
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}
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cfi->cfa.base = CFI_UNDEFINED;
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cfi->drap_reg = CFI_UNDEFINED;
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cfi->drap_offset = -1;
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}
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static void init_insn_state(struct insn_state *state, struct section *sec)
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{
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memset(state, 0, sizeof(*state));
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init_cfi_state(&state->cfi);
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/*
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* We need the full vmlinux for noinstr validation, otherwise we can
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* not correctly determine insn->call_dest->sec (external symbols do
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* not have a section).
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*/
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if (vmlinux && sec)
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state->noinstr = sec->noinstr;
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}
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/*
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* Call the arch-specific instruction decoder for all the instructions and add
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* them to the global instruction list.
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*/
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static int decode_instructions(struct objtool_file *file)
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{
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struct section *sec;
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struct symbol *func;
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unsigned long offset;
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struct instruction *insn;
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unsigned long nr_insns = 0;
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int ret;
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for_each_sec(file, sec) {
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if (!(sec->sh.sh_flags & SHF_EXECINSTR))
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continue;
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if (strcmp(sec->name, ".altinstr_replacement") &&
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strcmp(sec->name, ".altinstr_aux") &&
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strncmp(sec->name, ".discard.", 9))
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sec->text = true;
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if (!strcmp(sec->name, ".noinstr.text") ||
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!strcmp(sec->name, ".entry.text"))
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sec->noinstr = true;
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for (offset = 0; offset < sec->len; offset += insn->len) {
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insn = malloc(sizeof(*insn));
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if (!insn) {
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WARN("malloc failed");
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return -1;
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}
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memset(insn, 0, sizeof(*insn));
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INIT_LIST_HEAD(&insn->alts);
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INIT_LIST_HEAD(&insn->stack_ops);
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init_cfi_state(&insn->cfi);
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insn->sec = sec;
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insn->offset = offset;
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ret = arch_decode_instruction(file->elf, sec, offset,
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sec->len - offset,
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&insn->len, &insn->type,
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&insn->immediate,
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&insn->stack_ops);
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if (ret)
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goto err;
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hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
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list_add_tail(&insn->list, &file->insn_list);
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nr_insns++;
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}
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list_for_each_entry(func, &sec->symbol_list, list) {
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if (func->type != STT_FUNC || func->alias != func)
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continue;
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if (!find_insn(file, sec, func->offset)) {
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WARN("%s(): can't find starting instruction",
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func->name);
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return -1;
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}
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sym_for_each_insn(file, func, insn)
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insn->func = func;
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}
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}
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if (stats)
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printf("nr_insns: %lu\n", nr_insns);
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return 0;
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err:
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free(insn);
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return ret;
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}
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static struct instruction *find_last_insn(struct objtool_file *file,
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struct section *sec)
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{
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struct instruction *insn = NULL;
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unsigned int offset;
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unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
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for (offset = sec->len - 1; offset >= end && !insn; offset--)
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insn = find_insn(file, sec, offset);
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return insn;
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}
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/*
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* Mark "ud2" instructions and manually annotated dead ends.
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*/
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static int add_dead_ends(struct objtool_file *file)
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{
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struct section *sec;
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struct rela *rela;
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struct instruction *insn;
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/*
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* By default, "ud2" is a dead end unless otherwise annotated, because
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* GCC 7 inserts it for certain divide-by-zero cases.
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*/
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for_each_insn(file, insn)
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if (insn->type == INSN_BUG)
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insn->dead_end = true;
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/*
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* Check for manually annotated dead ends.
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*/
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sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
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if (!sec)
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goto reachable;
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list_for_each_entry(rela, &sec->rela_list, list) {
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if (rela->sym->type != STT_SECTION) {
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WARN("unexpected relocation symbol type in %s", sec->name);
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return -1;
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}
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insn = find_insn(file, rela->sym->sec, rela->addend);
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if (insn)
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insn = list_prev_entry(insn, list);
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else if (rela->addend == rela->sym->sec->len) {
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insn = find_last_insn(file, rela->sym->sec);
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if (!insn) {
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WARN("can't find unreachable insn at %s+0x%x",
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rela->sym->sec->name, rela->addend);
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return -1;
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}
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} else {
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WARN("can't find unreachable insn at %s+0x%x",
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rela->sym->sec->name, rela->addend);
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return -1;
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}
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insn->dead_end = true;
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}
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reachable:
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/*
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* These manually annotated reachable checks are needed for GCC 4.4,
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* where the Linux unreachable() macro isn't supported. In that case
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* GCC doesn't know the "ud2" is fatal, so it generates code as if it's
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* not a dead end.
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*/
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sec = find_section_by_name(file->elf, ".rela.discard.reachable");
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if (!sec)
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return 0;
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list_for_each_entry(rela, &sec->rela_list, list) {
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if (rela->sym->type != STT_SECTION) {
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WARN("unexpected relocation symbol type in %s", sec->name);
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return -1;
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}
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insn = find_insn(file, rela->sym->sec, rela->addend);
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if (insn)
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insn = list_prev_entry(insn, list);
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else if (rela->addend == rela->sym->sec->len) {
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insn = find_last_insn(file, rela->sym->sec);
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if (!insn) {
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WARN("can't find reachable insn at %s+0x%x",
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rela->sym->sec->name, rela->addend);
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return -1;
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}
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} else {
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WARN("can't find reachable insn at %s+0x%x",
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rela->sym->sec->name, rela->addend);
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return -1;
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}
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insn->dead_end = false;
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}
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return 0;
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}
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/*
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* Warnings shouldn't be reported for ignored functions.
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*/
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static void add_ignores(struct objtool_file *file)
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{
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struct instruction *insn;
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struct section *sec;
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struct symbol *func;
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struct rela *rela;
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sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
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if (!sec)
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return;
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list_for_each_entry(rela, &sec->rela_list, list) {
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switch (rela->sym->type) {
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case STT_FUNC:
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func = rela->sym;
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break;
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case STT_SECTION:
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func = find_func_by_offset(rela->sym->sec, rela->addend);
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if (!func)
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continue;
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break;
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default:
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WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
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continue;
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}
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func_for_each_insn(file, func, insn)
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insn->ignore = true;
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}
|
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}
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|
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/*
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* This is a whitelist of functions that is allowed to be called with AC set.
|
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* The list is meant to be minimal and only contains compiler instrumentation
|
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* ABI and a few functions used to implement *_{to,from}_user() functions.
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*
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* These functions must not directly change AC, but may PUSHF/POPF.
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*/
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static const char *uaccess_safe_builtin[] = {
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/* KASAN */
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"kasan_report",
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"check_memory_region",
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/* KASAN out-of-line */
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"__asan_loadN_noabort",
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"__asan_load1_noabort",
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"__asan_load2_noabort",
|
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"__asan_load4_noabort",
|
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"__asan_load8_noabort",
|
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"__asan_load16_noabort",
|
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"__asan_storeN_noabort",
|
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"__asan_store1_noabort",
|
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"__asan_store2_noabort",
|
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"__asan_store4_noabort",
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"__asan_store8_noabort",
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"__asan_store16_noabort",
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/* KASAN in-line */
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"__asan_report_load_n_noabort",
|
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"__asan_report_load1_noabort",
|
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"__asan_report_load2_noabort",
|
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"__asan_report_load4_noabort",
|
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"__asan_report_load8_noabort",
|
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"__asan_report_load16_noabort",
|
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"__asan_report_store_n_noabort",
|
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"__asan_report_store1_noabort",
|
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"__asan_report_store2_noabort",
|
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"__asan_report_store4_noabort",
|
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"__asan_report_store8_noabort",
|
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"__asan_report_store16_noabort",
|
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/* KCSAN */
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"__kcsan_check_access",
|
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"kcsan_found_watchpoint",
|
|
"kcsan_setup_watchpoint",
|
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"kcsan_check_scoped_accesses",
|
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"kcsan_disable_current",
|
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"kcsan_enable_current_nowarn",
|
|
/* KCSAN/TSAN */
|
|
"__tsan_func_entry",
|
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"__tsan_func_exit",
|
|
"__tsan_read_range",
|
|
"__tsan_write_range",
|
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"__tsan_read1",
|
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"__tsan_read2",
|
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"__tsan_read4",
|
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"__tsan_read8",
|
|
"__tsan_read16",
|
|
"__tsan_write1",
|
|
"__tsan_write2",
|
|
"__tsan_write4",
|
|
"__tsan_write8",
|
|
"__tsan_write16",
|
|
/* KCOV */
|
|
"write_comp_data",
|
|
"check_kcov_mode",
|
|
"__sanitizer_cov_trace_pc",
|
|
"__sanitizer_cov_trace_const_cmp1",
|
|
"__sanitizer_cov_trace_const_cmp2",
|
|
"__sanitizer_cov_trace_const_cmp4",
|
|
"__sanitizer_cov_trace_const_cmp8",
|
|
"__sanitizer_cov_trace_cmp1",
|
|
"__sanitizer_cov_trace_cmp2",
|
|
"__sanitizer_cov_trace_cmp4",
|
|
"__sanitizer_cov_trace_cmp8",
|
|
"__sanitizer_cov_trace_switch",
|
|
/* UBSAN */
|
|
"ubsan_type_mismatch_common",
|
|
"__ubsan_handle_type_mismatch",
|
|
"__ubsan_handle_type_mismatch_v1",
|
|
"__ubsan_handle_shift_out_of_bounds",
|
|
/* misc */
|
|
"csum_partial_copy_generic",
|
|
"__memcpy_mcsafe",
|
|
"mcsafe_handle_tail",
|
|
"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
|
|
NULL
|
|
};
|
|
|
|
static void add_uaccess_safe(struct objtool_file *file)
|
|
{
|
|
struct symbol *func;
|
|
const char **name;
|
|
|
|
if (!uaccess)
|
|
return;
|
|
|
|
for (name = uaccess_safe_builtin; *name; name++) {
|
|
func = find_symbol_by_name(file->elf, *name);
|
|
if (!func)
|
|
continue;
|
|
|
|
func->uaccess_safe = true;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* FIXME: For now, just ignore any alternatives which add retpolines. This is
|
|
* a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
|
|
* But it at least allows objtool to understand the control flow *around* the
|
|
* retpoline.
|
|
*/
|
|
static int add_ignore_alternatives(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
struct rela *rela;
|
|
struct instruction *insn;
|
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
|
|
if (!sec)
|
|
return 0;
|
|
|
|
list_for_each_entry(rela, &sec->rela_list, list) {
|
|
if (rela->sym->type != STT_SECTION) {
|
|
WARN("unexpected relocation symbol type in %s", sec->name);
|
|
return -1;
|
|
}
|
|
|
|
insn = find_insn(file, rela->sym->sec, rela->addend);
|
|
if (!insn) {
|
|
WARN("bad .discard.ignore_alts entry");
|
|
return -1;
|
|
}
|
|
|
|
insn->ignore_alts = true;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Find the destination instructions for all jumps.
|
|
*/
|
|
static int add_jump_destinations(struct objtool_file *file)
|
|
{
|
|
struct instruction *insn;
|
|
struct rela *rela;
|
|
struct section *dest_sec;
|
|
unsigned long dest_off;
|
|
|
|
for_each_insn(file, insn) {
|
|
if (!is_static_jump(insn))
|
|
continue;
|
|
|
|
if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
|
|
continue;
|
|
|
|
rela = find_rela_by_dest_range(file->elf, insn->sec,
|
|
insn->offset, insn->len);
|
|
if (!rela) {
|
|
dest_sec = insn->sec;
|
|
dest_off = arch_jump_destination(insn);
|
|
} else if (rela->sym->type == STT_SECTION) {
|
|
dest_sec = rela->sym->sec;
|
|
dest_off = arch_dest_rela_offset(rela->addend);
|
|
} else if (rela->sym->sec->idx) {
|
|
dest_sec = rela->sym->sec;
|
|
dest_off = rela->sym->sym.st_value +
|
|
arch_dest_rela_offset(rela->addend);
|
|
} else if (strstr(rela->sym->name, "_indirect_thunk_")) {
|
|
/*
|
|
* Retpoline jumps are really dynamic jumps in
|
|
* disguise, so convert them accordingly.
|
|
*/
|
|
if (insn->type == INSN_JUMP_UNCONDITIONAL)
|
|
insn->type = INSN_JUMP_DYNAMIC;
|
|
else
|
|
insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
|
|
|
|
insn->retpoline_safe = true;
|
|
continue;
|
|
} else {
|
|
/* external sibling call */
|
|
insn->call_dest = rela->sym;
|
|
continue;
|
|
}
|
|
|
|
insn->jump_dest = find_insn(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;
|
|
}
|
|
|
|
/*
|
|
* Cross-function jump.
|
|
*/
|
|
if (insn->func && insn->jump_dest->func &&
|
|
insn->func != insn->jump_dest->func) {
|
|
|
|
/*
|
|
* For GCC 8+, create parent/child links for any cold
|
|
* subfunctions. This is _mostly_ redundant with a
|
|
* similar initialization in read_symbols().
|
|
*
|
|
* If a function has aliases, we want the *first* such
|
|
* function in the symbol table to be the subfunction's
|
|
* parent. In that case we overwrite the
|
|
* initialization done in read_symbols().
|
|
*
|
|
* However this code can't completely replace the
|
|
* read_symbols() code because this doesn't detect the
|
|
* case where the parent function's only reference to a
|
|
* subfunction is through a jump table.
|
|
*/
|
|
if (!strstr(insn->func->name, ".cold.") &&
|
|
strstr(insn->jump_dest->func->name, ".cold.")) {
|
|
insn->func->cfunc = insn->jump_dest->func;
|
|
insn->jump_dest->func->pfunc = insn->func;
|
|
|
|
} else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
|
|
insn->jump_dest->offset == insn->jump_dest->func->offset) {
|
|
|
|
/* internal sibling call */
|
|
insn->call_dest = insn->jump_dest->func;
|
|
}
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void remove_insn_ops(struct instruction *insn)
|
|
{
|
|
struct stack_op *op, *tmp;
|
|
|
|
list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
|
|
list_del(&op->list);
|
|
free(op);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Find the destination instructions for all calls.
|
|
*/
|
|
static int add_call_destinations(struct objtool_file *file)
|
|
{
|
|
struct instruction *insn;
|
|
unsigned long dest_off;
|
|
struct rela *rela;
|
|
|
|
for_each_insn(file, insn) {
|
|
if (insn->type != INSN_CALL)
|
|
continue;
|
|
|
|
rela = find_rela_by_dest_range(file->elf, insn->sec,
|
|
insn->offset, insn->len);
|
|
if (!rela) {
|
|
dest_off = arch_jump_destination(insn);
|
|
insn->call_dest = find_func_by_offset(insn->sec, dest_off);
|
|
if (!insn->call_dest)
|
|
insn->call_dest = find_symbol_by_offset(insn->sec, dest_off);
|
|
|
|
if (insn->ignore)
|
|
continue;
|
|
|
|
if (!insn->call_dest) {
|
|
WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
if (insn->func && insn->call_dest->type != STT_FUNC) {
|
|
WARN_FUNC("unsupported call to non-function",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
} else if (rela->sym->type == STT_SECTION) {
|
|
dest_off = arch_dest_rela_offset(rela->addend);
|
|
insn->call_dest = find_func_by_offset(rela->sym->sec,
|
|
dest_off);
|
|
if (!insn->call_dest) {
|
|
WARN_FUNC("can't find call dest symbol at %s+0x%lx",
|
|
insn->sec, insn->offset,
|
|
rela->sym->sec->name,
|
|
dest_off);
|
|
return -1;
|
|
}
|
|
} else
|
|
insn->call_dest = rela->sym;
|
|
|
|
/*
|
|
* Whatever stack impact regular CALLs have, should be undone
|
|
* by the RETURN of the called function.
|
|
*
|
|
* Annotated intra-function calls retain the stack_ops but
|
|
* are converted to JUMP, see read_intra_function_calls().
|
|
*/
|
|
remove_insn_ops(insn);
|
|
}
|
|
|
|
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.
|
|
*/
|
|
static int handle_group_alt(struct objtool_file *file,
|
|
struct special_alt *special_alt,
|
|
struct instruction *orig_insn,
|
|
struct instruction **new_insn)
|
|
{
|
|
static unsigned int alt_group_next_index = 1;
|
|
struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
|
|
unsigned int alt_group = alt_group_next_index++;
|
|
unsigned long dest_off;
|
|
|
|
last_orig_insn = NULL;
|
|
insn = orig_insn;
|
|
sec_for_each_insn_from(file, insn) {
|
|
if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
|
|
break;
|
|
|
|
insn->alt_group = alt_group;
|
|
last_orig_insn = insn;
|
|
}
|
|
|
|
if (next_insn_same_sec(file, last_orig_insn)) {
|
|
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);
|
|
INIT_LIST_HEAD(&fake_jump->stack_ops);
|
|
init_cfi_state(&fake_jump->cfi);
|
|
|
|
fake_jump->sec = special_alt->new_sec;
|
|
fake_jump->offset = FAKE_JUMP_OFFSET;
|
|
fake_jump->type = INSN_JUMP_UNCONDITIONAL;
|
|
fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
|
|
fake_jump->func = orig_insn->func;
|
|
}
|
|
|
|
if (!special_alt->new_len) {
|
|
if (!fake_jump) {
|
|
WARN("%s: empty alternative at end of section",
|
|
special_alt->orig_sec->name);
|
|
return -1;
|
|
}
|
|
|
|
*new_insn = fake_jump;
|
|
return 0;
|
|
}
|
|
|
|
last_new_insn = NULL;
|
|
alt_group = alt_group_next_index++;
|
|
insn = *new_insn;
|
|
sec_for_each_insn_from(file, insn) {
|
|
if (insn->offset >= special_alt->new_off + special_alt->new_len)
|
|
break;
|
|
|
|
last_new_insn = insn;
|
|
|
|
insn->ignore = orig_insn->ignore_alts;
|
|
insn->func = orig_insn->func;
|
|
insn->alt_group = alt_group;
|
|
|
|
/*
|
|
* Since alternative replacement code is copy/pasted by the
|
|
* kernel after applying relocations, generally such code can't
|
|
* have relative-address relocation references to outside the
|
|
* .altinstr_replacement section, unless the arch's
|
|
* alternatives code can adjust the relative offsets
|
|
* accordingly.
|
|
*
|
|
* The x86 alternatives code adjusts the offsets only when it
|
|
* encounters a branch instruction at the very beginning of the
|
|
* replacement group.
|
|
*/
|
|
if ((insn->offset != special_alt->new_off ||
|
|
(insn->type != INSN_CALL && !is_static_jump(insn))) &&
|
|
find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {
|
|
|
|
WARN_FUNC("unsupported relocation in alternatives section",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
if (!is_static_jump(insn))
|
|
continue;
|
|
|
|
if (!insn->immediate)
|
|
continue;
|
|
|
|
dest_off = arch_jump_destination(insn);
|
|
if (dest_off == special_alt->new_off + special_alt->new_len) {
|
|
if (!fake_jump) {
|
|
WARN("%s: alternative jump to end of section",
|
|
special_alt->orig_sec->name);
|
|
return -1;
|
|
}
|
|
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;
|
|
}
|
|
|
|
if (fake_jump)
|
|
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 add_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) {
|
|
|
|
orig_insn = find_insn(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_insn(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) {
|
|
if (!special_alt->orig_len) {
|
|
WARN_FUNC("empty alternative entry",
|
|
orig_insn->sec, orig_insn->offset);
|
|
continue;
|
|
}
|
|
|
|
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 = malloc(sizeof(*alt));
|
|
if (!alt) {
|
|
WARN("malloc failed");
|
|
ret = -1;
|
|
goto out;
|
|
}
|
|
|
|
alt->insn = new_insn;
|
|
alt->skip_orig = special_alt->skip_orig;
|
|
orig_insn->ignore_alts |= special_alt->skip_alt;
|
|
list_add_tail(&alt->list, &orig_insn->alts);
|
|
|
|
list_del(&special_alt->list);
|
|
free(special_alt);
|
|
}
|
|
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
static int add_jump_table(struct objtool_file *file, struct instruction *insn,
|
|
struct rela *table)
|
|
{
|
|
struct rela *rela = table;
|
|
struct instruction *dest_insn;
|
|
struct alternative *alt;
|
|
struct symbol *pfunc = insn->func->pfunc;
|
|
unsigned int prev_offset = 0;
|
|
|
|
/*
|
|
* Each @rela is a switch table relocation which points to the target
|
|
* instruction.
|
|
*/
|
|
list_for_each_entry_from(rela, &table->sec->rela_list, list) {
|
|
|
|
/* Check for the end of the table: */
|
|
if (rela != table && rela->jump_table_start)
|
|
break;
|
|
|
|
/* Make sure the table entries are consecutive: */
|
|
if (prev_offset && rela->offset != prev_offset + 8)
|
|
break;
|
|
|
|
/* Detect function pointers from contiguous objects: */
|
|
if (rela->sym->sec == pfunc->sec &&
|
|
rela->addend == pfunc->offset)
|
|
break;
|
|
|
|
dest_insn = find_insn(file, rela->sym->sec, rela->addend);
|
|
if (!dest_insn)
|
|
break;
|
|
|
|
/* Make sure the destination is in the same function: */
|
|
if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
|
|
break;
|
|
|
|
alt = malloc(sizeof(*alt));
|
|
if (!alt) {
|
|
WARN("malloc failed");
|
|
return -1;
|
|
}
|
|
|
|
alt->insn = dest_insn;
|
|
list_add_tail(&alt->list, &insn->alts);
|
|
prev_offset = rela->offset;
|
|
}
|
|
|
|
if (!prev_offset) {
|
|
WARN_FUNC("can't find switch jump table",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* find_jump_table() - Given a dynamic jump, find the switch jump table in
|
|
* .rodata associated with it.
|
|
*
|
|
* There are 3 basic patterns:
|
|
*
|
|
* 1. jmpq *[rodata addr](,%reg,8)
|
|
*
|
|
* This is the most common case by far. It jumps to an address in a simple
|
|
* jump table which is stored in .rodata.
|
|
*
|
|
* 2. jmpq *[rodata addr](%rip)
|
|
*
|
|
* This is caused by a rare GCC quirk, currently only seen in three driver
|
|
* functions in the kernel, only with certain obscure non-distro configs.
|
|
*
|
|
* As part of an optimization, GCC makes a copy of an existing switch jump
|
|
* table, modifies it, and then hard-codes the jump (albeit with an indirect
|
|
* jump) to use a single entry in the table. The rest of the jump table and
|
|
* some of its jump targets remain as dead code.
|
|
*
|
|
* In such a case we can just crudely ignore all unreachable instruction
|
|
* warnings for the entire object file. Ideally we would just ignore them
|
|
* for the function, but that would require redesigning the code quite a
|
|
* bit. And honestly that's just not worth doing: unreachable instruction
|
|
* warnings are of questionable value anyway, and this is such a rare issue.
|
|
*
|
|
* 3. mov [rodata addr],%reg1
|
|
* ... some instructions ...
|
|
* jmpq *(%reg1,%reg2,8)
|
|
*
|
|
* This is a fairly uncommon pattern which is new for GCC 6. As of this
|
|
* writing, there are 11 occurrences of it in the allmodconfig kernel.
|
|
*
|
|
* As of GCC 7 there are quite a few more of these and the 'in between' code
|
|
* is significant. Esp. with KASAN enabled some of the code between the mov
|
|
* and jmpq uses .rodata itself, which can confuse things.
|
|
*
|
|
* TODO: Once we have DWARF CFI and smarter instruction decoding logic,
|
|
* ensure the same register is used in the mov and jump instructions.
|
|
*
|
|
* NOTE: RETPOLINE made it harder still to decode dynamic jumps.
|
|
*/
|
|
static struct rela *find_jump_table(struct objtool_file *file,
|
|
struct symbol *func,
|
|
struct instruction *insn)
|
|
{
|
|
struct rela *text_rela, *table_rela;
|
|
struct instruction *dest_insn, *orig_insn = insn;
|
|
struct section *table_sec;
|
|
unsigned long table_offset;
|
|
|
|
/*
|
|
* Backward search using the @first_jump_src links, these help avoid
|
|
* much of the 'in between' code. Which avoids us getting confused by
|
|
* it.
|
|
*/
|
|
for (;
|
|
insn && insn->func && insn->func->pfunc == func;
|
|
insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
|
|
|
|
if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
|
|
break;
|
|
|
|
/* allow small jumps within the range */
|
|
if (insn->type == INSN_JUMP_UNCONDITIONAL &&
|
|
insn->jump_dest &&
|
|
(insn->jump_dest->offset <= insn->offset ||
|
|
insn->jump_dest->offset > orig_insn->offset))
|
|
break;
|
|
|
|
/* look for a relocation which references .rodata */
|
|
text_rela = find_rela_by_dest_range(file->elf, insn->sec,
|
|
insn->offset, insn->len);
|
|
if (!text_rela || text_rela->sym->type != STT_SECTION ||
|
|
!text_rela->sym->sec->rodata)
|
|
continue;
|
|
|
|
table_offset = text_rela->addend;
|
|
table_sec = text_rela->sym->sec;
|
|
|
|
if (text_rela->type == R_X86_64_PC32)
|
|
table_offset += 4;
|
|
|
|
/*
|
|
* Make sure the .rodata address isn't associated with a
|
|
* symbol. GCC jump tables are anonymous data.
|
|
*
|
|
* Also support C jump tables which are in the same format as
|
|
* switch jump tables. For objtool to recognize them, they
|
|
* need to be placed in the C_JUMP_TABLE_SECTION section. They
|
|
* have symbols associated with them.
|
|
*/
|
|
if (find_symbol_containing(table_sec, table_offset) &&
|
|
strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
|
|
continue;
|
|
|
|
/*
|
|
* Each table entry has a rela associated with it. The rela
|
|
* should reference text in the same function as the original
|
|
* instruction.
|
|
*/
|
|
table_rela = find_rela_by_dest(file->elf, table_sec, table_offset);
|
|
if (!table_rela)
|
|
continue;
|
|
dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend);
|
|
if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
|
|
continue;
|
|
|
|
/*
|
|
* Use of RIP-relative switch jumps is quite rare, and
|
|
* indicates a rare GCC quirk/bug which can leave dead code
|
|
* behind.
|
|
*/
|
|
if (text_rela->type == R_X86_64_PC32)
|
|
file->ignore_unreachables = true;
|
|
|
|
return table_rela;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* First pass: Mark the head of each jump table so that in the next pass,
|
|
* we know when a given jump table ends and the next one starts.
|
|
*/
|
|
static void mark_func_jump_tables(struct objtool_file *file,
|
|
struct symbol *func)
|
|
{
|
|
struct instruction *insn, *last = NULL;
|
|
struct rela *rela;
|
|
|
|
func_for_each_insn(file, func, insn) {
|
|
if (!last)
|
|
last = insn;
|
|
|
|
/*
|
|
* Store back-pointers for unconditional forward jumps such
|
|
* that find_jump_table() can back-track using those and
|
|
* avoid some potentially confusing code.
|
|
*/
|
|
if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
|
|
insn->offset > last->offset &&
|
|
insn->jump_dest->offset > insn->offset &&
|
|
!insn->jump_dest->first_jump_src) {
|
|
|
|
insn->jump_dest->first_jump_src = insn;
|
|
last = insn->jump_dest;
|
|
}
|
|
|
|
if (insn->type != INSN_JUMP_DYNAMIC)
|
|
continue;
|
|
|
|
rela = find_jump_table(file, func, insn);
|
|
if (rela) {
|
|
rela->jump_table_start = true;
|
|
insn->jump_table = rela;
|
|
}
|
|
}
|
|
}
|
|
|
|
static int add_func_jump_tables(struct objtool_file *file,
|
|
struct symbol *func)
|
|
{
|
|
struct instruction *insn;
|
|
int ret;
|
|
|
|
func_for_each_insn(file, func, insn) {
|
|
if (!insn->jump_table)
|
|
continue;
|
|
|
|
ret = add_jump_table(file, insn, insn->jump_table);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* 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 add_jump_table_alts(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
struct symbol *func;
|
|
int ret;
|
|
|
|
if (!file->rodata)
|
|
return 0;
|
|
|
|
for_each_sec(file, sec) {
|
|
list_for_each_entry(func, &sec->symbol_list, list) {
|
|
if (func->type != STT_FUNC)
|
|
continue;
|
|
|
|
mark_func_jump_tables(file, func);
|
|
ret = add_func_jump_tables(file, func);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int read_unwind_hints(struct objtool_file *file)
|
|
{
|
|
struct section *sec, *relasec;
|
|
struct rela *rela;
|
|
struct unwind_hint *hint;
|
|
struct instruction *insn;
|
|
struct cfi_reg *cfa;
|
|
int i;
|
|
|
|
sec = find_section_by_name(file->elf, ".discard.unwind_hints");
|
|
if (!sec)
|
|
return 0;
|
|
|
|
relasec = sec->rela;
|
|
if (!relasec) {
|
|
WARN("missing .rela.discard.unwind_hints section");
|
|
return -1;
|
|
}
|
|
|
|
if (sec->len % sizeof(struct unwind_hint)) {
|
|
WARN("struct unwind_hint size mismatch");
|
|
return -1;
|
|
}
|
|
|
|
file->hints = true;
|
|
|
|
for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
|
|
hint = (struct unwind_hint *)sec->data->d_buf + i;
|
|
|
|
rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint));
|
|
if (!rela) {
|
|
WARN("can't find rela for unwind_hints[%d]", i);
|
|
return -1;
|
|
}
|
|
|
|
insn = find_insn(file, rela->sym->sec, rela->addend);
|
|
if (!insn) {
|
|
WARN("can't find insn for unwind_hints[%d]", i);
|
|
return -1;
|
|
}
|
|
|
|
cfa = &insn->cfi.cfa;
|
|
|
|
if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) {
|
|
insn->ret_offset = hint->sp_offset;
|
|
continue;
|
|
}
|
|
|
|
insn->hint = true;
|
|
|
|
switch (hint->sp_reg) {
|
|
case ORC_REG_UNDEFINED:
|
|
cfa->base = CFI_UNDEFINED;
|
|
break;
|
|
case ORC_REG_SP:
|
|
cfa->base = CFI_SP;
|
|
break;
|
|
case ORC_REG_BP:
|
|
cfa->base = CFI_BP;
|
|
break;
|
|
case ORC_REG_SP_INDIRECT:
|
|
cfa->base = CFI_SP_INDIRECT;
|
|
break;
|
|
case ORC_REG_R10:
|
|
cfa->base = CFI_R10;
|
|
break;
|
|
case ORC_REG_R13:
|
|
cfa->base = CFI_R13;
|
|
break;
|
|
case ORC_REG_DI:
|
|
cfa->base = CFI_DI;
|
|
break;
|
|
case ORC_REG_DX:
|
|
cfa->base = CFI_DX;
|
|
break;
|
|
default:
|
|
WARN_FUNC("unsupported unwind_hint sp base reg %d",
|
|
insn->sec, insn->offset, hint->sp_reg);
|
|
return -1;
|
|
}
|
|
|
|
cfa->offset = hint->sp_offset;
|
|
insn->cfi.type = hint->type;
|
|
insn->cfi.end = hint->end;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int read_retpoline_hints(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
struct instruction *insn;
|
|
struct rela *rela;
|
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
|
|
if (!sec)
|
|
return 0;
|
|
|
|
list_for_each_entry(rela, &sec->rela_list, list) {
|
|
if (rela->sym->type != STT_SECTION) {
|
|
WARN("unexpected relocation symbol type in %s", sec->name);
|
|
return -1;
|
|
}
|
|
|
|
insn = find_insn(file, rela->sym->sec, rela->addend);
|
|
if (!insn) {
|
|
WARN("bad .discard.retpoline_safe entry");
|
|
return -1;
|
|
}
|
|
|
|
if (insn->type != INSN_JUMP_DYNAMIC &&
|
|
insn->type != INSN_CALL_DYNAMIC) {
|
|
WARN_FUNC("retpoline_safe hint not an indirect jump/call",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
insn->retpoline_safe = true;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int read_instr_hints(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
struct instruction *insn;
|
|
struct rela *rela;
|
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
|
|
if (!sec)
|
|
return 0;
|
|
|
|
list_for_each_entry(rela, &sec->rela_list, list) {
|
|
if (rela->sym->type != STT_SECTION) {
|
|
WARN("unexpected relocation symbol type in %s", sec->name);
|
|
return -1;
|
|
}
|
|
|
|
insn = find_insn(file, rela->sym->sec, rela->addend);
|
|
if (!insn) {
|
|
WARN("bad .discard.instr_end entry");
|
|
return -1;
|
|
}
|
|
|
|
insn->instr--;
|
|
}
|
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
|
|
if (!sec)
|
|
return 0;
|
|
|
|
list_for_each_entry(rela, &sec->rela_list, list) {
|
|
if (rela->sym->type != STT_SECTION) {
|
|
WARN("unexpected relocation symbol type in %s", sec->name);
|
|
return -1;
|
|
}
|
|
|
|
insn = find_insn(file, rela->sym->sec, rela->addend);
|
|
if (!insn) {
|
|
WARN("bad .discard.instr_begin entry");
|
|
return -1;
|
|
}
|
|
|
|
insn->instr++;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int read_intra_function_calls(struct objtool_file *file)
|
|
{
|
|
struct instruction *insn;
|
|
struct section *sec;
|
|
struct rela *rela;
|
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
|
|
if (!sec)
|
|
return 0;
|
|
|
|
list_for_each_entry(rela, &sec->rela_list, list) {
|
|
unsigned long dest_off;
|
|
|
|
if (rela->sym->type != STT_SECTION) {
|
|
WARN("unexpected relocation symbol type in %s",
|
|
sec->name);
|
|
return -1;
|
|
}
|
|
|
|
insn = find_insn(file, rela->sym->sec, rela->addend);
|
|
if (!insn) {
|
|
WARN("bad .discard.intra_function_call entry");
|
|
return -1;
|
|
}
|
|
|
|
if (insn->type != INSN_CALL) {
|
|
WARN_FUNC("intra_function_call not a direct call",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* Treat intra-function CALLs as JMPs, but with a stack_op.
|
|
* See add_call_destinations(), which strips stack_ops from
|
|
* normal CALLs.
|
|
*/
|
|
insn->type = INSN_JUMP_UNCONDITIONAL;
|
|
|
|
dest_off = insn->offset + insn->len + insn->immediate;
|
|
insn->jump_dest = find_insn(file, insn->sec, dest_off);
|
|
if (!insn->jump_dest) {
|
|
WARN_FUNC("can't find call dest at %s+0x%lx",
|
|
insn->sec, insn->offset,
|
|
insn->sec->name, dest_off);
|
|
return -1;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void mark_rodata(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
bool found = false;
|
|
|
|
/*
|
|
* Search for the following rodata sections, each of which can
|
|
* potentially contain jump tables:
|
|
*
|
|
* - .rodata: can contain GCC switch tables
|
|
* - .rodata.<func>: same, if -fdata-sections is being used
|
|
* - .rodata..c_jump_table: contains C annotated jump tables
|
|
*
|
|
* .rodata.str1.* sections are ignored; they don't contain jump tables.
|
|
*/
|
|
for_each_sec(file, sec) {
|
|
if (!strncmp(sec->name, ".rodata", 7) &&
|
|
!strstr(sec->name, ".str1.")) {
|
|
sec->rodata = true;
|
|
found = true;
|
|
}
|
|
}
|
|
|
|
file->rodata = found;
|
|
}
|
|
|
|
static int decode_sections(struct objtool_file *file)
|
|
{
|
|
int ret;
|
|
|
|
mark_rodata(file);
|
|
|
|
ret = decode_instructions(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = add_dead_ends(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
add_ignores(file);
|
|
add_uaccess_safe(file);
|
|
|
|
ret = add_ignore_alternatives(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = add_jump_destinations(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = add_special_section_alts(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = read_intra_function_calls(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = add_call_destinations(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = add_jump_table_alts(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = read_unwind_hints(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = read_retpoline_hints(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = read_instr_hints(file);
|
|
if (ret)
|
|
return ret;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static bool is_fentry_call(struct instruction *insn)
|
|
{
|
|
if (insn->type == INSN_CALL && insn->call_dest &&
|
|
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, struct insn_state *state)
|
|
{
|
|
u8 ret_offset = insn->ret_offset;
|
|
struct cfi_state *cfi = &state->cfi;
|
|
int i;
|
|
|
|
if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
|
|
return true;
|
|
|
|
if (cfi->cfa.offset != initial_func_cfi.cfa.offset + ret_offset)
|
|
return true;
|
|
|
|
if (cfi->stack_size != initial_func_cfi.cfa.offset + ret_offset)
|
|
return true;
|
|
|
|
/*
|
|
* If there is a ret offset hint then don't check registers
|
|
* because a callee-saved register might have been pushed on
|
|
* the stack.
|
|
*/
|
|
if (ret_offset)
|
|
return false;
|
|
|
|
for (i = 0; i < CFI_NUM_REGS; i++) {
|
|
if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
|
|
cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool has_valid_stack_frame(struct insn_state *state)
|
|
{
|
|
struct cfi_state *cfi = &state->cfi;
|
|
|
|
if (cfi->cfa.base == CFI_BP && cfi->regs[CFI_BP].base == CFI_CFA &&
|
|
cfi->regs[CFI_BP].offset == -16)
|
|
return true;
|
|
|
|
if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static int update_cfi_state_regs(struct instruction *insn,
|
|
struct cfi_state *cfi,
|
|
struct stack_op *op)
|
|
{
|
|
struct cfi_reg *cfa = &cfi->cfa;
|
|
|
|
if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
|
|
return 0;
|
|
|
|
/* push */
|
|
if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
|
|
cfa->offset += 8;
|
|
|
|
/* pop */
|
|
if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
|
|
cfa->offset -= 8;
|
|
|
|
/* add immediate to sp */
|
|
if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
|
|
op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
|
|
cfa->offset -= op->src.offset;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
|
|
{
|
|
if (arch_callee_saved_reg(reg) &&
|
|
cfi->regs[reg].base == CFI_UNDEFINED) {
|
|
cfi->regs[reg].base = base;
|
|
cfi->regs[reg].offset = offset;
|
|
}
|
|
}
|
|
|
|
static void restore_reg(struct cfi_state *cfi, unsigned char reg)
|
|
{
|
|
cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
|
|
cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
|
|
}
|
|
|
|
/*
|
|
* A note about DRAP stack alignment:
|
|
*
|
|
* GCC has the concept of a DRAP register, which is used to help keep track of
|
|
* the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
|
|
* register. The typical DRAP pattern is:
|
|
*
|
|
* 4c 8d 54 24 08 lea 0x8(%rsp),%r10
|
|
* 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
|
|
* 41 ff 72 f8 pushq -0x8(%r10)
|
|
* 55 push %rbp
|
|
* 48 89 e5 mov %rsp,%rbp
|
|
* (more pushes)
|
|
* 41 52 push %r10
|
|
* ...
|
|
* 41 5a pop %r10
|
|
* (more pops)
|
|
* 5d pop %rbp
|
|
* 49 8d 62 f8 lea -0x8(%r10),%rsp
|
|
* c3 retq
|
|
*
|
|
* There are some variations in the epilogues, like:
|
|
*
|
|
* 5b pop %rbx
|
|
* 41 5a pop %r10
|
|
* 41 5c pop %r12
|
|
* 41 5d pop %r13
|
|
* 41 5e pop %r14
|
|
* c9 leaveq
|
|
* 49 8d 62 f8 lea -0x8(%r10),%rsp
|
|
* c3 retq
|
|
*
|
|
* and:
|
|
*
|
|
* 4c 8b 55 e8 mov -0x18(%rbp),%r10
|
|
* 48 8b 5d e0 mov -0x20(%rbp),%rbx
|
|
* 4c 8b 65 f0 mov -0x10(%rbp),%r12
|
|
* 4c 8b 6d f8 mov -0x8(%rbp),%r13
|
|
* c9 leaveq
|
|
* 49 8d 62 f8 lea -0x8(%r10),%rsp
|
|
* c3 retq
|
|
*
|
|
* Sometimes r13 is used as the DRAP register, in which case it's saved and
|
|
* restored beforehand:
|
|
*
|
|
* 41 55 push %r13
|
|
* 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
|
|
* 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
|
|
* ...
|
|
* 49 8d 65 f0 lea -0x10(%r13),%rsp
|
|
* 41 5d pop %r13
|
|
* c3 retq
|
|
*/
|
|
static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
|
|
struct stack_op *op)
|
|
{
|
|
struct cfi_reg *cfa = &cfi->cfa;
|
|
struct cfi_reg *regs = cfi->regs;
|
|
|
|
/* stack operations don't make sense with an undefined CFA */
|
|
if (cfa->base == CFI_UNDEFINED) {
|
|
if (insn->func) {
|
|
WARN_FUNC("undefined stack state", insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
if (cfi->type == ORC_TYPE_REGS || cfi->type == ORC_TYPE_REGS_IRET)
|
|
return update_cfi_state_regs(insn, cfi, op);
|
|
|
|
switch (op->dest.type) {
|
|
|
|
case OP_DEST_REG:
|
|
switch (op->src.type) {
|
|
|
|
case OP_SRC_REG:
|
|
if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
|
|
cfa->base == CFI_SP &&
|
|
regs[CFI_BP].base == CFI_CFA &&
|
|
regs[CFI_BP].offset == -cfa->offset) {
|
|
|
|
/* mov %rsp, %rbp */
|
|
cfa->base = op->dest.reg;
|
|
cfi->bp_scratch = false;
|
|
}
|
|
|
|
else if (op->src.reg == CFI_SP &&
|
|
op->dest.reg == CFI_BP && cfi->drap) {
|
|
|
|
/* drap: mov %rsp, %rbp */
|
|
regs[CFI_BP].base = CFI_BP;
|
|
regs[CFI_BP].offset = -cfi->stack_size;
|
|
cfi->bp_scratch = false;
|
|
}
|
|
|
|
else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
|
|
|
|
/*
|
|
* mov %rsp, %reg
|
|
*
|
|
* This is needed for the rare case where GCC
|
|
* does:
|
|
*
|
|
* mov %rsp, %rax
|
|
* ...
|
|
* mov %rax, %rsp
|
|
*/
|
|
cfi->vals[op->dest.reg].base = CFI_CFA;
|
|
cfi->vals[op->dest.reg].offset = -cfi->stack_size;
|
|
}
|
|
|
|
else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
|
|
cfa->base == CFI_BP) {
|
|
|
|
/*
|
|
* mov %rbp, %rsp
|
|
*
|
|
* Restore the original stack pointer (Clang).
|
|
*/
|
|
cfi->stack_size = -cfi->regs[CFI_BP].offset;
|
|
}
|
|
|
|
else if (op->dest.reg == cfa->base) {
|
|
|
|
/* mov %reg, %rsp */
|
|
if (cfa->base == CFI_SP &&
|
|
cfi->vals[op->src.reg].base == CFI_CFA) {
|
|
|
|
/*
|
|
* This is needed for the rare case
|
|
* where GCC does something dumb like:
|
|
*
|
|
* lea 0x8(%rsp), %rcx
|
|
* ...
|
|
* mov %rcx, %rsp
|
|
*/
|
|
cfa->offset = -cfi->vals[op->src.reg].offset;
|
|
cfi->stack_size = cfa->offset;
|
|
|
|
} else {
|
|
cfa->base = CFI_UNDEFINED;
|
|
cfa->offset = 0;
|
|
}
|
|
}
|
|
|
|
break;
|
|
|
|
case OP_SRC_ADD:
|
|
if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
|
|
|
|
/* add imm, %rsp */
|
|
cfi->stack_size -= op->src.offset;
|
|
if (cfa->base == CFI_SP)
|
|
cfa->offset -= op->src.offset;
|
|
break;
|
|
}
|
|
|
|
if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
|
|
|
|
/* lea disp(%rbp), %rsp */
|
|
cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
|
|
break;
|
|
}
|
|
|
|
if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
|
|
|
|
/* drap: lea disp(%rsp), %drap */
|
|
cfi->drap_reg = op->dest.reg;
|
|
|
|
/*
|
|
* lea disp(%rsp), %reg
|
|
*
|
|
* This is needed for the rare case where GCC
|
|
* does something dumb like:
|
|
*
|
|
* lea 0x8(%rsp), %rcx
|
|
* ...
|
|
* mov %rcx, %rsp
|
|
*/
|
|
cfi->vals[op->dest.reg].base = CFI_CFA;
|
|
cfi->vals[op->dest.reg].offset = \
|
|
-cfi->stack_size + op->src.offset;
|
|
|
|
break;
|
|
}
|
|
|
|
if (cfi->drap && op->dest.reg == CFI_SP &&
|
|
op->src.reg == cfi->drap_reg) {
|
|
|
|
/* drap: lea disp(%drap), %rsp */
|
|
cfa->base = CFI_SP;
|
|
cfa->offset = cfi->stack_size = -op->src.offset;
|
|
cfi->drap_reg = CFI_UNDEFINED;
|
|
cfi->drap = false;
|
|
break;
|
|
}
|
|
|
|
if (op->dest.reg == cfi->cfa.base) {
|
|
WARN_FUNC("unsupported stack register modification",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
break;
|
|
|
|
case OP_SRC_AND:
|
|
if (op->dest.reg != CFI_SP ||
|
|
(cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
|
|
(cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
|
|
WARN_FUNC("unsupported stack pointer realignment",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
if (cfi->drap_reg != CFI_UNDEFINED) {
|
|
/* drap: and imm, %rsp */
|
|
cfa->base = cfi->drap_reg;
|
|
cfa->offset = cfi->stack_size = 0;
|
|
cfi->drap = true;
|
|
}
|
|
|
|
/*
|
|
* Older versions of GCC (4.8ish) realign the stack
|
|
* without DRAP, with a frame pointer.
|
|
*/
|
|
|
|
break;
|
|
|
|
case OP_SRC_POP:
|
|
case OP_SRC_POPF:
|
|
if (!cfi->drap && op->dest.reg == cfa->base) {
|
|
|
|
/* pop %rbp */
|
|
cfa->base = CFI_SP;
|
|
}
|
|
|
|
if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
|
|
op->dest.reg == cfi->drap_reg &&
|
|
cfi->drap_offset == -cfi->stack_size) {
|
|
|
|
/* drap: pop %drap */
|
|
cfa->base = cfi->drap_reg;
|
|
cfa->offset = 0;
|
|
cfi->drap_offset = -1;
|
|
|
|
} else if (regs[op->dest.reg].offset == -cfi->stack_size) {
|
|
|
|
/* pop %reg */
|
|
restore_reg(cfi, op->dest.reg);
|
|
}
|
|
|
|
cfi->stack_size -= 8;
|
|
if (cfa->base == CFI_SP)
|
|
cfa->offset -= 8;
|
|
|
|
break;
|
|
|
|
case OP_SRC_REG_INDIRECT:
|
|
if (cfi->drap && op->src.reg == CFI_BP &&
|
|
op->src.offset == cfi->drap_offset) {
|
|
|
|
/* drap: mov disp(%rbp), %drap */
|
|
cfa->base = cfi->drap_reg;
|
|
cfa->offset = 0;
|
|
cfi->drap_offset = -1;
|
|
}
|
|
|
|
if (cfi->drap && op->src.reg == CFI_BP &&
|
|
op->src.offset == regs[op->dest.reg].offset) {
|
|
|
|
/* drap: mov disp(%rbp), %reg */
|
|
restore_reg(cfi, op->dest.reg);
|
|
|
|
} else if (op->src.reg == cfa->base &&
|
|
op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
|
|
|
|
/* mov disp(%rbp), %reg */
|
|
/* mov disp(%rsp), %reg */
|
|
restore_reg(cfi, op->dest.reg);
|
|
}
|
|
|
|
break;
|
|
|
|
default:
|
|
WARN_FUNC("unknown stack-related instruction",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
break;
|
|
|
|
case OP_DEST_PUSH:
|
|
case OP_DEST_PUSHF:
|
|
cfi->stack_size += 8;
|
|
if (cfa->base == CFI_SP)
|
|
cfa->offset += 8;
|
|
|
|
if (op->src.type != OP_SRC_REG)
|
|
break;
|
|
|
|
if (cfi->drap) {
|
|
if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
|
|
|
|
/* drap: push %drap */
|
|
cfa->base = CFI_BP_INDIRECT;
|
|
cfa->offset = -cfi->stack_size;
|
|
|
|
/* save drap so we know when to restore it */
|
|
cfi->drap_offset = -cfi->stack_size;
|
|
|
|
} else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
|
|
|
|
/* drap: push %rbp */
|
|
cfi->stack_size = 0;
|
|
|
|
} else if (regs[op->src.reg].base == CFI_UNDEFINED) {
|
|
|
|
/* drap: push %reg */
|
|
save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
|
|
}
|
|
|
|
} else {
|
|
|
|
/* push %reg */
|
|
save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
|
|
}
|
|
|
|
/* detect when asm code uses rbp as a scratch register */
|
|
if (!no_fp && insn->func && op->src.reg == CFI_BP &&
|
|
cfa->base != CFI_BP)
|
|
cfi->bp_scratch = true;
|
|
break;
|
|
|
|
case OP_DEST_REG_INDIRECT:
|
|
|
|
if (cfi->drap) {
|
|
if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
|
|
|
|
/* drap: mov %drap, disp(%rbp) */
|
|
cfa->base = CFI_BP_INDIRECT;
|
|
cfa->offset = op->dest.offset;
|
|
|
|
/* save drap offset so we know when to restore it */
|
|
cfi->drap_offset = op->dest.offset;
|
|
}
|
|
|
|
else if (regs[op->src.reg].base == CFI_UNDEFINED) {
|
|
|
|
/* drap: mov reg, disp(%rbp) */
|
|
save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
|
|
}
|
|
|
|
} else if (op->dest.reg == cfa->base) {
|
|
|
|
/* mov reg, disp(%rbp) */
|
|
/* mov reg, disp(%rsp) */
|
|
save_reg(cfi, op->src.reg, CFI_CFA,
|
|
op->dest.offset - cfi->cfa.offset);
|
|
}
|
|
|
|
break;
|
|
|
|
case OP_DEST_LEAVE:
|
|
if ((!cfi->drap && cfa->base != CFI_BP) ||
|
|
(cfi->drap && cfa->base != cfi->drap_reg)) {
|
|
WARN_FUNC("leave instruction with modified stack frame",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
/* leave (mov %rbp, %rsp; pop %rbp) */
|
|
|
|
cfi->stack_size = -cfi->regs[CFI_BP].offset - 8;
|
|
restore_reg(cfi, CFI_BP);
|
|
|
|
if (!cfi->drap) {
|
|
cfa->base = CFI_SP;
|
|
cfa->offset -= 8;
|
|
}
|
|
|
|
break;
|
|
|
|
case OP_DEST_MEM:
|
|
if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
|
|
WARN_FUNC("unknown stack-related memory operation",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
/* pop mem */
|
|
cfi->stack_size -= 8;
|
|
if (cfa->base == CFI_SP)
|
|
cfa->offset -= 8;
|
|
|
|
break;
|
|
|
|
default:
|
|
WARN_FUNC("unknown stack-related instruction",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int handle_insn_ops(struct instruction *insn, struct insn_state *state)
|
|
{
|
|
struct stack_op *op;
|
|
|
|
list_for_each_entry(op, &insn->stack_ops, list) {
|
|
struct cfi_state old_cfi = state->cfi;
|
|
int res;
|
|
|
|
res = update_cfi_state(insn, &state->cfi, op);
|
|
if (res)
|
|
return res;
|
|
|
|
if (insn->alt_group && memcmp(&state->cfi, &old_cfi, sizeof(struct cfi_state))) {
|
|
WARN_FUNC("alternative modifies stack", insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
if (op->dest.type == OP_DEST_PUSHF) {
|
|
if (!state->uaccess_stack) {
|
|
state->uaccess_stack = 1;
|
|
} else if (state->uaccess_stack >> 31) {
|
|
WARN_FUNC("PUSHF stack exhausted",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
state->uaccess_stack <<= 1;
|
|
state->uaccess_stack |= state->uaccess;
|
|
}
|
|
|
|
if (op->src.type == OP_SRC_POPF) {
|
|
if (state->uaccess_stack) {
|
|
state->uaccess = state->uaccess_stack & 1;
|
|
state->uaccess_stack >>= 1;
|
|
if (state->uaccess_stack == 1)
|
|
state->uaccess_stack = 0;
|
|
}
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
|
|
{
|
|
struct cfi_state *cfi1 = &insn->cfi;
|
|
int i;
|
|
|
|
if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
|
|
|
|
WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
|
|
insn->sec, insn->offset,
|
|
cfi1->cfa.base, cfi1->cfa.offset,
|
|
cfi2->cfa.base, cfi2->cfa.offset);
|
|
|
|
} else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
|
|
for (i = 0; i < CFI_NUM_REGS; i++) {
|
|
if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
|
|
sizeof(struct cfi_reg)))
|
|
continue;
|
|
|
|
WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
|
|
insn->sec, insn->offset,
|
|
i, cfi1->regs[i].base, cfi1->regs[i].offset,
|
|
i, cfi2->regs[i].base, cfi2->regs[i].offset);
|
|
break;
|
|
}
|
|
|
|
} else if (cfi1->type != cfi2->type) {
|
|
|
|
WARN_FUNC("stack state mismatch: type1=%d type2=%d",
|
|
insn->sec, insn->offset, cfi1->type, cfi2->type);
|
|
|
|
} else if (cfi1->drap != cfi2->drap ||
|
|
(cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
|
|
(cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
|
|
|
|
WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
|
|
insn->sec, insn->offset,
|
|
cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
|
|
cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
|
|
|
|
} else
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static inline bool func_uaccess_safe(struct symbol *func)
|
|
{
|
|
if (func)
|
|
return func->uaccess_safe;
|
|
|
|
return false;
|
|
}
|
|
|
|
static inline const char *call_dest_name(struct instruction *insn)
|
|
{
|
|
if (insn->call_dest)
|
|
return insn->call_dest->name;
|
|
|
|
return "{dynamic}";
|
|
}
|
|
|
|
static int validate_call(struct instruction *insn, struct insn_state *state)
|
|
{
|
|
if (state->noinstr && state->instr <= 0 &&
|
|
(!insn->call_dest || !insn->call_dest->sec->noinstr)) {
|
|
WARN_FUNC("call to %s() leaves .noinstr.text section",
|
|
insn->sec, insn->offset, call_dest_name(insn));
|
|
return 1;
|
|
}
|
|
|
|
if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
|
|
WARN_FUNC("call to %s() with UACCESS enabled",
|
|
insn->sec, insn->offset, call_dest_name(insn));
|
|
return 1;
|
|
}
|
|
|
|
if (state->df) {
|
|
WARN_FUNC("call to %s() with DF set",
|
|
insn->sec, insn->offset, call_dest_name(insn));
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
|
|
{
|
|
if (has_modified_stack_frame(insn, state)) {
|
|
WARN_FUNC("sibling call from callable instruction with modified stack frame",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
return validate_call(insn, state);
|
|
}
|
|
|
|
static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
|
|
{
|
|
if (state->noinstr && state->instr > 0) {
|
|
WARN_FUNC("return with instrumentation enabled",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (state->uaccess && !func_uaccess_safe(func)) {
|
|
WARN_FUNC("return with UACCESS enabled",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (!state->uaccess && func_uaccess_safe(func)) {
|
|
WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (state->df) {
|
|
WARN_FUNC("return with DF set",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (func && has_modified_stack_frame(insn, state)) {
|
|
WARN_FUNC("return with modified stack frame",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (state->cfi.bp_scratch) {
|
|
WARN_FUNC("BP used as a scratch register",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Alternatives should not contain any ORC entries, this in turn means they
|
|
* should not contain any CFI ops, which implies all instructions should have
|
|
* the same same CFI state.
|
|
*
|
|
* It is possible to constuct alternatives that have unreachable holes that go
|
|
* unreported (because they're NOPs), such holes would result in CFI_UNDEFINED
|
|
* states which then results in ORC entries, which we just said we didn't want.
|
|
*
|
|
* Avoid them by copying the CFI entry of the first instruction into the whole
|
|
* alternative.
|
|
*/
|
|
static void fill_alternative_cfi(struct objtool_file *file, struct instruction *insn)
|
|
{
|
|
struct instruction *first_insn = insn;
|
|
int alt_group = insn->alt_group;
|
|
|
|
sec_for_each_insn_continue(file, insn) {
|
|
if (insn->alt_group != alt_group)
|
|
break;
|
|
insn->cfi = first_insn->cfi;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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 symbol *func,
|
|
struct instruction *insn, struct insn_state state)
|
|
{
|
|
struct alternative *alt;
|
|
struct instruction *next_insn;
|
|
struct section *sec;
|
|
u8 visited;
|
|
int ret;
|
|
|
|
sec = insn->sec;
|
|
|
|
while (1) {
|
|
next_insn = next_insn_same_sec(file, insn);
|
|
|
|
if (file->c_file && func && insn->func && func != insn->func->pfunc) {
|
|
WARN("%s() falls through to next function %s()",
|
|
func->name, insn->func->name);
|
|
return 1;
|
|
}
|
|
|
|
if (func && insn->ignore) {
|
|
WARN_FUNC("BUG: why am I validating an ignored function?",
|
|
sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
visited = 1 << state.uaccess;
|
|
if (insn->visited) {
|
|
if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
|
|
return 1;
|
|
|
|
if (insn->visited & visited)
|
|
return 0;
|
|
}
|
|
|
|
if (state.noinstr)
|
|
state.instr += insn->instr;
|
|
|
|
if (insn->hint)
|
|
state.cfi = insn->cfi;
|
|
else
|
|
insn->cfi = state.cfi;
|
|
|
|
insn->visited |= visited;
|
|
|
|
if (!insn->ignore_alts && !list_empty(&insn->alts)) {
|
|
bool skip_orig = false;
|
|
|
|
list_for_each_entry(alt, &insn->alts, list) {
|
|
if (alt->skip_orig)
|
|
skip_orig = true;
|
|
|
|
ret = validate_branch(file, func, alt->insn, state);
|
|
if (ret) {
|
|
if (backtrace)
|
|
BT_FUNC("(alt)", insn);
|
|
return ret;
|
|
}
|
|
}
|
|
|
|
if (insn->alt_group)
|
|
fill_alternative_cfi(file, insn);
|
|
|
|
if (skip_orig)
|
|
return 0;
|
|
}
|
|
|
|
if (handle_insn_ops(insn, &state))
|
|
return 1;
|
|
|
|
switch (insn->type) {
|
|
|
|
case INSN_RETURN:
|
|
return validate_return(func, insn, &state);
|
|
|
|
case INSN_CALL:
|
|
case INSN_CALL_DYNAMIC:
|
|
ret = validate_call(insn, &state);
|
|
if (ret)
|
|
return ret;
|
|
|
|
if (!no_fp && func && !is_fentry_call(insn) &&
|
|
!has_valid_stack_frame(&state)) {
|
|
WARN_FUNC("call without frame pointer save/setup",
|
|
sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (dead_end_function(file, insn->call_dest))
|
|
return 0;
|
|
|
|
break;
|
|
|
|
case INSN_JUMP_CONDITIONAL:
|
|
case INSN_JUMP_UNCONDITIONAL:
|
|
if (func && is_sibling_call(insn)) {
|
|
ret = validate_sibling_call(insn, &state);
|
|
if (ret)
|
|
return ret;
|
|
|
|
} else if (insn->jump_dest) {
|
|
ret = validate_branch(file, func,
|
|
insn->jump_dest, state);
|
|
if (ret) {
|
|
if (backtrace)
|
|
BT_FUNC("(branch)", insn);
|
|
return ret;
|
|
}
|
|
}
|
|
|
|
if (insn->type == INSN_JUMP_UNCONDITIONAL)
|
|
return 0;
|
|
|
|
break;
|
|
|
|
case INSN_JUMP_DYNAMIC:
|
|
case INSN_JUMP_DYNAMIC_CONDITIONAL:
|
|
if (func && is_sibling_call(insn)) {
|
|
ret = validate_sibling_call(insn, &state);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
|
|
if (insn->type == INSN_JUMP_DYNAMIC)
|
|
return 0;
|
|
|
|
break;
|
|
|
|
case INSN_CONTEXT_SWITCH:
|
|
if (func && (!next_insn || !next_insn->hint)) {
|
|
WARN_FUNC("unsupported instruction in callable function",
|
|
sec, insn->offset);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
|
|
case INSN_STAC:
|
|
if (state.uaccess) {
|
|
WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
state.uaccess = true;
|
|
break;
|
|
|
|
case INSN_CLAC:
|
|
if (!state.uaccess && func) {
|
|
WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (func_uaccess_safe(func) && !state.uaccess_stack) {
|
|
WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
state.uaccess = false;
|
|
break;
|
|
|
|
case INSN_STD:
|
|
if (state.df)
|
|
WARN_FUNC("recursive STD", sec, insn->offset);
|
|
|
|
state.df = true;
|
|
break;
|
|
|
|
case INSN_CLD:
|
|
if (!state.df && func)
|
|
WARN_FUNC("redundant CLD", sec, insn->offset);
|
|
|
|
state.df = false;
|
|
break;
|
|
|
|
default:
|
|
break;
|
|
}
|
|
|
|
if (insn->dead_end)
|
|
return 0;
|
|
|
|
if (!next_insn) {
|
|
if (state.cfi.cfa.base == CFI_UNDEFINED)
|
|
return 0;
|
|
WARN("%s: unexpected end of section", sec->name);
|
|
return 1;
|
|
}
|
|
|
|
insn = next_insn;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
|
|
{
|
|
struct instruction *insn;
|
|
struct insn_state state;
|
|
int ret, warnings = 0;
|
|
|
|
if (!file->hints)
|
|
return 0;
|
|
|
|
init_insn_state(&state, sec);
|
|
|
|
if (sec) {
|
|
insn = find_insn(file, sec, 0);
|
|
if (!insn)
|
|
return 0;
|
|
} else {
|
|
insn = list_first_entry(&file->insn_list, typeof(*insn), list);
|
|
}
|
|
|
|
while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
|
|
if (insn->hint && !insn->visited) {
|
|
ret = validate_branch(file, insn->func, insn, state);
|
|
if (ret && backtrace)
|
|
BT_FUNC("<=== (hint)", insn);
|
|
warnings += ret;
|
|
}
|
|
|
|
insn = list_next_entry(insn, list);
|
|
}
|
|
|
|
return warnings;
|
|
}
|
|
|
|
static int validate_retpoline(struct objtool_file *file)
|
|
{
|
|
struct instruction *insn;
|
|
int warnings = 0;
|
|
|
|
for_each_insn(file, insn) {
|
|
if (insn->type != INSN_JUMP_DYNAMIC &&
|
|
insn->type != INSN_CALL_DYNAMIC)
|
|
continue;
|
|
|
|
if (insn->retpoline_safe)
|
|
continue;
|
|
|
|
/*
|
|
* .init.text code is ran before userspace and thus doesn't
|
|
* strictly need retpolines, except for modules which are
|
|
* loaded late, they very much do need retpoline in their
|
|
* .init.text
|
|
*/
|
|
if (!strcmp(insn->sec->name, ".init.text") && !module)
|
|
continue;
|
|
|
|
WARN_FUNC("indirect %s found in RETPOLINE build",
|
|
insn->sec, insn->offset,
|
|
insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
|
|
|
|
warnings++;
|
|
}
|
|
|
|
return warnings;
|
|
}
|
|
|
|
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)
|
|
{
|
|
int i;
|
|
|
|
if (insn->ignore || insn->type == INSN_NOP)
|
|
return true;
|
|
|
|
/*
|
|
* Ignore any unused exceptions. This can happen when a whitelisted
|
|
* function has an exception table entry.
|
|
*
|
|
* Also ignore alternative replacement instructions. This can happen
|
|
* when a whitelisted function uses one of the ALTERNATIVE macros.
|
|
*/
|
|
if (!strcmp(insn->sec->name, ".fixup") ||
|
|
!strcmp(insn->sec->name, ".altinstr_replacement") ||
|
|
!strcmp(insn->sec->name, ".altinstr_aux"))
|
|
return true;
|
|
|
|
if (!insn->func)
|
|
return false;
|
|
|
|
/*
|
|
* CONFIG_UBSAN_TRAP inserts a UD2 when it sees
|
|
* __builtin_unreachable(). The BUG() macro has an unreachable() after
|
|
* the UD2, which causes GCC's undefined trap logic to emit another UD2
|
|
* (or occasionally a JMP to UD2).
|
|
*/
|
|
if (list_prev_entry(insn, list)->dead_end &&
|
|
(insn->type == INSN_BUG ||
|
|
(insn->type == INSN_JUMP_UNCONDITIONAL &&
|
|
insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
|
|
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) {
|
|
if (insn->jump_dest &&
|
|
insn->jump_dest->func == insn->func) {
|
|
insn = insn->jump_dest;
|
|
continue;
|
|
}
|
|
|
|
break;
|
|
}
|
|
|
|
if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
|
|
break;
|
|
|
|
insn = list_next_entry(insn, list);
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static int validate_symbol(struct objtool_file *file, struct section *sec,
|
|
struct symbol *sym, struct insn_state *state)
|
|
{
|
|
struct instruction *insn;
|
|
int ret;
|
|
|
|
if (!sym->len) {
|
|
WARN("%s() is missing an ELF size annotation", sym->name);
|
|
return 1;
|
|
}
|
|
|
|
if (sym->pfunc != sym || sym->alias != sym)
|
|
return 0;
|
|
|
|
insn = find_insn(file, sec, sym->offset);
|
|
if (!insn || insn->ignore || insn->visited)
|
|
return 0;
|
|
|
|
state->uaccess = sym->uaccess_safe;
|
|
|
|
ret = validate_branch(file, insn->func, insn, *state);
|
|
if (ret && backtrace)
|
|
BT_FUNC("<=== (sym)", insn);
|
|
return ret;
|
|
}
|
|
|
|
static int validate_section(struct objtool_file *file, struct section *sec)
|
|
{
|
|
struct insn_state state;
|
|
struct symbol *func;
|
|
int warnings = 0;
|
|
|
|
list_for_each_entry(func, &sec->symbol_list, list) {
|
|
if (func->type != STT_FUNC)
|
|
continue;
|
|
|
|
init_insn_state(&state, sec);
|
|
state.cfi.cfa = initial_func_cfi.cfa;
|
|
memcpy(&state.cfi.regs, &initial_func_cfi.regs,
|
|
CFI_NUM_REGS * sizeof(struct cfi_reg));
|
|
state.cfi.stack_size = initial_func_cfi.cfa.offset;
|
|
|
|
warnings += validate_symbol(file, sec, func, &state);
|
|
}
|
|
|
|
return warnings;
|
|
}
|
|
|
|
static int validate_vmlinux_functions(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
int warnings = 0;
|
|
|
|
sec = find_section_by_name(file->elf, ".noinstr.text");
|
|
if (sec) {
|
|
warnings += validate_section(file, sec);
|
|
warnings += validate_unwind_hints(file, sec);
|
|
}
|
|
|
|
sec = find_section_by_name(file->elf, ".entry.text");
|
|
if (sec) {
|
|
warnings += validate_section(file, sec);
|
|
warnings += validate_unwind_hints(file, sec);
|
|
}
|
|
|
|
return warnings;
|
|
}
|
|
|
|
static int validate_functions(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
int warnings = 0;
|
|
|
|
for_each_sec(file, sec) {
|
|
if (!(sec->sh.sh_flags & SHF_EXECINSTR))
|
|
continue;
|
|
|
|
warnings += validate_section(file, sec);
|
|
}
|
|
|
|
return warnings;
|
|
}
|
|
|
|
static int validate_reachable_instructions(struct objtool_file *file)
|
|
{
|
|
struct instruction *insn;
|
|
|
|
if (file->ignore_unreachables)
|
|
return 0;
|
|
|
|
for_each_insn(file, insn) {
|
|
if (insn->visited || ignore_unreachable_insn(insn))
|
|
continue;
|
|
|
|
WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static struct objtool_file file;
|
|
|
|
int check(const char *_objname, bool orc)
|
|
{
|
|
int ret, warnings = 0;
|
|
|
|
objname = _objname;
|
|
|
|
file.elf = elf_open_read(objname, orc ? O_RDWR : O_RDONLY);
|
|
if (!file.elf)
|
|
return 1;
|
|
|
|
INIT_LIST_HEAD(&file.insn_list);
|
|
hash_init(file.insn_hash);
|
|
file.c_file = find_section_by_name(file.elf, ".comment");
|
|
file.ignore_unreachables = no_unreachable;
|
|
file.hints = false;
|
|
|
|
arch_initial_func_cfi_state(&initial_func_cfi);
|
|
|
|
ret = decode_sections(&file);
|
|
if (ret < 0)
|
|
goto out;
|
|
warnings += ret;
|
|
|
|
if (list_empty(&file.insn_list))
|
|
goto out;
|
|
|
|
if (vmlinux && !validate_dup) {
|
|
ret = validate_vmlinux_functions(&file);
|
|
if (ret < 0)
|
|
goto out;
|
|
|
|
warnings += ret;
|
|
goto out;
|
|
}
|
|
|
|
if (retpoline) {
|
|
ret = validate_retpoline(&file);
|
|
if (ret < 0)
|
|
return ret;
|
|
warnings += ret;
|
|
}
|
|
|
|
ret = validate_functions(&file);
|
|
if (ret < 0)
|
|
goto out;
|
|
warnings += ret;
|
|
|
|
ret = validate_unwind_hints(&file, NULL);
|
|
if (ret < 0)
|
|
goto out;
|
|
warnings += ret;
|
|
|
|
if (!warnings) {
|
|
ret = validate_reachable_instructions(&file);
|
|
if (ret < 0)
|
|
goto out;
|
|
warnings += ret;
|
|
}
|
|
|
|
if (orc) {
|
|
ret = create_orc(&file);
|
|
if (ret < 0)
|
|
goto out;
|
|
|
|
ret = create_orc_sections(&file);
|
|
if (ret < 0)
|
|
goto out;
|
|
|
|
ret = elf_write(file.elf);
|
|
if (ret < 0)
|
|
goto out;
|
|
}
|
|
|
|
out:
|
|
if (ret < 0) {
|
|
/*
|
|
* Fatal error. The binary is corrupt or otherwise broken in
|
|
* some way, or objtool itself is broken. Fail the kernel
|
|
* build.
|
|
*/
|
|
return ret;
|
|
}
|
|
|
|
return 0;
|
|
}
|