mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 10:49:33 +00:00
![Linus Torvalds](/assets/img/avatar_default.png)
Pull x86 asm updates from Ingo Molnar: "The main changes in this cycle were: - Cross-arch changes to move the linker sections for NOTES and EXCEPTION_TABLE into the RO_DATA area, where they belong on most architectures. (Kees Cook) - Switch the x86 linker fill byte from x90 (NOP) to 0xcc (INT3), to trap jumps into the middle of those padding areas instead of sliding execution. (Kees Cook) - A thorough cleanup of symbol definitions within x86 assembler code. The rather randomly named macros got streamlined around a (hopefully) straightforward naming scheme: SYM_START(name, linkage, align...) SYM_END(name, sym_type) SYM_FUNC_START(name) SYM_FUNC_END(name) SYM_CODE_START(name) SYM_CODE_END(name) SYM_DATA_START(name) SYM_DATA_END(name) etc - with about three times of these basic primitives with some label, local symbol or attribute variant, expressed via postfixes. No change in functionality intended. (Jiri Slaby) - Misc other changes, cleanups and smaller fixes" * 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (67 commits) x86/entry/64: Remove pointless jump in paranoid_exit x86/entry/32: Remove unused resume_userspace label x86/build/vdso: Remove meaningless CFLAGS_REMOVE_*.o m68k: Convert missed RODATA to RO_DATA x86/vmlinux: Use INT3 instead of NOP for linker fill bytes x86/mm: Report actual image regions in /proc/iomem x86/mm: Report which part of kernel image is freed x86/mm: Remove redundant address-of operators on addresses xtensa: Move EXCEPTION_TABLE to RO_DATA segment powerpc: Move EXCEPTION_TABLE to RO_DATA segment parisc: Move EXCEPTION_TABLE to RO_DATA segment microblaze: Move EXCEPTION_TABLE to RO_DATA segment ia64: Move EXCEPTION_TABLE to RO_DATA segment h8300: Move EXCEPTION_TABLE to RO_DATA segment c6x: Move EXCEPTION_TABLE to RO_DATA segment arm64: Move EXCEPTION_TABLE to RO_DATA segment alpha: Move EXCEPTION_TABLE to RO_DATA segment x86/vmlinux: Move EXCEPTION_TABLE to RO_DATA segment x86/vmlinux: Actually use _etext for the end of the text segment vmlinux.lds.h: Allow EXCEPTION_TABLE to live in RO_DATA ...
2498 lines
59 KiB
C
2498 lines
59 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/*
|
|
* Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
|
|
*/
|
|
|
|
#include <string.h>
|
|
#include <stdlib.h>
|
|
|
|
#include "builtin.h"
|
|
#include "check.h"
|
|
#include "elf.h"
|
|
#include "special.h"
|
|
#include "arch.h"
|
|
#include "warn.h"
|
|
|
|
#include <linux/hashtable.h>
|
|
#include <linux/kernel.h>
|
|
|
|
#define FAKE_JUMP_OFFSET -1
|
|
|
|
#define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
|
|
|
|
struct alternative {
|
|
struct list_head list;
|
|
struct instruction *insn;
|
|
bool skip_orig;
|
|
};
|
|
|
|
const char *objname;
|
|
struct cfi_state initial_func_cfi;
|
|
|
|
struct instruction *find_insn(struct objtool_file *file,
|
|
struct section *sec, unsigned long offset)
|
|
{
|
|
struct instruction *insn;
|
|
|
|
hash_for_each_possible(file->insn_hash, insn, hash, offset)
|
|
if (insn->sec == sec && insn->offset == offset)
|
|
return insn;
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static struct instruction *next_insn_same_sec(struct objtool_file *file,
|
|
struct instruction *insn)
|
|
{
|
|
struct instruction *next = list_next_entry(insn, list);
|
|
|
|
if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
|
|
return NULL;
|
|
|
|
return next;
|
|
}
|
|
|
|
static struct instruction *next_insn_same_func(struct objtool_file *file,
|
|
struct instruction *insn)
|
|
{
|
|
struct instruction *next = list_next_entry(insn, list);
|
|
struct symbol *func = insn->func;
|
|
|
|
if (!func)
|
|
return NULL;
|
|
|
|
if (&next->list != &file->insn_list && next->func == func)
|
|
return next;
|
|
|
|
/* Check if we're already in the subfunction: */
|
|
if (func == func->cfunc)
|
|
return NULL;
|
|
|
|
/* Move to the subfunction: */
|
|
return find_insn(file, func->cfunc->sec, func->cfunc->offset);
|
|
}
|
|
|
|
#define func_for_each_insn_all(file, func, insn) \
|
|
for (insn = find_insn(file, func->sec, func->offset); \
|
|
insn; \
|
|
insn = next_insn_same_func(file, insn))
|
|
|
|
#define func_for_each_insn(file, func, insn) \
|
|
for (insn = find_insn(file, func->sec, func->offset); \
|
|
insn && &insn->list != &file->insn_list && \
|
|
insn->sec == func->sec && \
|
|
insn->offset < func->offset + func->len; \
|
|
insn = list_next_entry(insn, list))
|
|
|
|
#define func_for_each_insn_continue_reverse(file, func, insn) \
|
|
for (insn = list_prev_entry(insn, list); \
|
|
&insn->list != &file->insn_list && \
|
|
insn->sec == func->sec && insn->offset >= func->offset; \
|
|
insn = list_prev_entry(insn, list))
|
|
|
|
#define sec_for_each_insn_from(file, insn) \
|
|
for (; insn; insn = next_insn_same_sec(file, insn))
|
|
|
|
#define sec_for_each_insn_continue(file, insn) \
|
|
for (insn = next_insn_same_sec(file, insn); insn; \
|
|
insn = next_insn_same_sec(file, insn))
|
|
|
|
static bool is_sibling_call(struct instruction *insn)
|
|
{
|
|
/* An indirect jump is either a sibling call or a jump to a table. */
|
|
if (insn->type == INSN_JUMP_DYNAMIC)
|
|
return list_empty(&insn->alts);
|
|
|
|
if (insn->type != INSN_JUMP_CONDITIONAL &&
|
|
insn->type != INSN_JUMP_UNCONDITIONAL)
|
|
return false;
|
|
|
|
/* add_jump_destinations() sets insn->call_dest for sibling calls. */
|
|
return !!insn->call_dest;
|
|
}
|
|
|
|
/*
|
|
* This checks to see if the given function is a "noreturn" function.
|
|
*
|
|
* For global functions which are outside the scope of this object file, we
|
|
* have to keep a manual list of them.
|
|
*
|
|
* For local functions, we have to detect them manually by simply looking for
|
|
* the lack of a return instruction.
|
|
*/
|
|
static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
|
|
int recursion)
|
|
{
|
|
int i;
|
|
struct instruction *insn;
|
|
bool empty = true;
|
|
|
|
/*
|
|
* Unfortunately these have to be hard coded because the noreturn
|
|
* attribute isn't provided in ELF data.
|
|
*/
|
|
static const char * const global_noreturns[] = {
|
|
"__stack_chk_fail",
|
|
"panic",
|
|
"do_exit",
|
|
"do_task_dead",
|
|
"__module_put_and_exit",
|
|
"complete_and_exit",
|
|
"__reiserfs_panic",
|
|
"lbug_with_loc",
|
|
"fortify_panic",
|
|
"usercopy_abort",
|
|
"machine_real_restart",
|
|
"rewind_stack_do_exit",
|
|
"kunit_try_catch_throw",
|
|
};
|
|
|
|
if (!func)
|
|
return false;
|
|
|
|
if (func->bind == STB_WEAK)
|
|
return false;
|
|
|
|
if (func->bind == STB_GLOBAL)
|
|
for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
|
|
if (!strcmp(func->name, global_noreturns[i]))
|
|
return true;
|
|
|
|
if (!func->len)
|
|
return false;
|
|
|
|
insn = find_insn(file, func->sec, func->offset);
|
|
if (!insn->func)
|
|
return false;
|
|
|
|
func_for_each_insn_all(file, func, insn) {
|
|
empty = false;
|
|
|
|
if (insn->type == INSN_RETURN)
|
|
return false;
|
|
}
|
|
|
|
if (empty)
|
|
return false;
|
|
|
|
/*
|
|
* A function can have a sibling call instead of a return. In that
|
|
* case, the function's dead-end status depends on whether the target
|
|
* of the sibling call returns.
|
|
*/
|
|
func_for_each_insn_all(file, func, insn) {
|
|
if (is_sibling_call(insn)) {
|
|
struct instruction *dest = insn->jump_dest;
|
|
|
|
if (!dest)
|
|
/* sibling call to another file */
|
|
return false;
|
|
|
|
/* local sibling call */
|
|
if (recursion == 5) {
|
|
/*
|
|
* Infinite recursion: two functions have
|
|
* sibling calls to each other. This is a very
|
|
* rare case. It means they aren't dead ends.
|
|
*/
|
|
return false;
|
|
}
|
|
|
|
return __dead_end_function(file, dest->func, recursion+1);
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool dead_end_function(struct objtool_file *file, struct symbol *func)
|
|
{
|
|
return __dead_end_function(file, func, 0);
|
|
}
|
|
|
|
static void clear_insn_state(struct insn_state *state)
|
|
{
|
|
int i;
|
|
|
|
memset(state, 0, sizeof(*state));
|
|
state->cfa.base = CFI_UNDEFINED;
|
|
for (i = 0; i < CFI_NUM_REGS; i++) {
|
|
state->regs[i].base = CFI_UNDEFINED;
|
|
state->vals[i].base = CFI_UNDEFINED;
|
|
}
|
|
state->drap_reg = CFI_UNDEFINED;
|
|
state->drap_offset = -1;
|
|
}
|
|
|
|
/*
|
|
* Call the arch-specific instruction decoder for all the instructions and add
|
|
* them to the global instruction list.
|
|
*/
|
|
static int decode_instructions(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
struct symbol *func;
|
|
unsigned long offset;
|
|
struct instruction *insn;
|
|
int ret;
|
|
|
|
for_each_sec(file, sec) {
|
|
|
|
if (!(sec->sh.sh_flags & SHF_EXECINSTR))
|
|
continue;
|
|
|
|
if (strcmp(sec->name, ".altinstr_replacement") &&
|
|
strcmp(sec->name, ".altinstr_aux") &&
|
|
strncmp(sec->name, ".discard.", 9))
|
|
sec->text = true;
|
|
|
|
for (offset = 0; offset < sec->len; offset += insn->len) {
|
|
insn = malloc(sizeof(*insn));
|
|
if (!insn) {
|
|
WARN("malloc failed");
|
|
return -1;
|
|
}
|
|
memset(insn, 0, sizeof(*insn));
|
|
INIT_LIST_HEAD(&insn->alts);
|
|
clear_insn_state(&insn->state);
|
|
|
|
insn->sec = sec;
|
|
insn->offset = offset;
|
|
|
|
ret = arch_decode_instruction(file->elf, sec, offset,
|
|
sec->len - offset,
|
|
&insn->len, &insn->type,
|
|
&insn->immediate,
|
|
&insn->stack_op);
|
|
if (ret)
|
|
goto err;
|
|
|
|
hash_add(file->insn_hash, &insn->hash, insn->offset);
|
|
list_add_tail(&insn->list, &file->insn_list);
|
|
}
|
|
|
|
list_for_each_entry(func, &sec->symbol_list, list) {
|
|
if (func->type != STT_FUNC || func->alias != func)
|
|
continue;
|
|
|
|
if (!find_insn(file, sec, func->offset)) {
|
|
WARN("%s(): can't find starting instruction",
|
|
func->name);
|
|
return -1;
|
|
}
|
|
|
|
func_for_each_insn(file, func, insn)
|
|
insn->func = func;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
|
|
err:
|
|
free(insn);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Mark "ud2" instructions and manually annotated dead ends.
|
|
*/
|
|
static int add_dead_ends(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
struct rela *rela;
|
|
struct instruction *insn;
|
|
bool found;
|
|
|
|
/*
|
|
* By default, "ud2" is a dead end unless otherwise annotated, because
|
|
* GCC 7 inserts it for certain divide-by-zero cases.
|
|
*/
|
|
for_each_insn(file, insn)
|
|
if (insn->type == INSN_BUG)
|
|
insn->dead_end = true;
|
|
|
|
/*
|
|
* Check for manually annotated dead ends.
|
|
*/
|
|
sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
|
|
if (!sec)
|
|
goto reachable;
|
|
|
|
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)
|
|
insn = list_prev_entry(insn, list);
|
|
else if (rela->addend == rela->sym->sec->len) {
|
|
found = false;
|
|
list_for_each_entry_reverse(insn, &file->insn_list, list) {
|
|
if (insn->sec == rela->sym->sec) {
|
|
found = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (!found) {
|
|
WARN("can't find unreachable insn at %s+0x%x",
|
|
rela->sym->sec->name, rela->addend);
|
|
return -1;
|
|
}
|
|
} else {
|
|
WARN("can't find unreachable insn at %s+0x%x",
|
|
rela->sym->sec->name, rela->addend);
|
|
return -1;
|
|
}
|
|
|
|
insn->dead_end = true;
|
|
}
|
|
|
|
reachable:
|
|
/*
|
|
* These manually annotated reachable checks are needed for GCC 4.4,
|
|
* where the Linux unreachable() macro isn't supported. In that case
|
|
* GCC doesn't know the "ud2" is fatal, so it generates code as if it's
|
|
* not a dead end.
|
|
*/
|
|
sec = find_section_by_name(file->elf, ".rela.discard.reachable");
|
|
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)
|
|
insn = list_prev_entry(insn, list);
|
|
else if (rela->addend == rela->sym->sec->len) {
|
|
found = false;
|
|
list_for_each_entry_reverse(insn, &file->insn_list, list) {
|
|
if (insn->sec == rela->sym->sec) {
|
|
found = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (!found) {
|
|
WARN("can't find reachable insn at %s+0x%x",
|
|
rela->sym->sec->name, rela->addend);
|
|
return -1;
|
|
}
|
|
} else {
|
|
WARN("can't find reachable insn at %s+0x%x",
|
|
rela->sym->sec->name, rela->addend);
|
|
return -1;
|
|
}
|
|
|
|
insn->dead_end = false;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Warnings shouldn't be reported for ignored functions.
|
|
*/
|
|
static void add_ignores(struct objtool_file *file)
|
|
{
|
|
struct instruction *insn;
|
|
struct section *sec;
|
|
struct symbol *func;
|
|
struct rela *rela;
|
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
|
|
if (!sec)
|
|
return;
|
|
|
|
list_for_each_entry(rela, &sec->rela_list, list) {
|
|
switch (rela->sym->type) {
|
|
case STT_FUNC:
|
|
func = rela->sym;
|
|
break;
|
|
|
|
case STT_SECTION:
|
|
func = find_symbol_by_offset(rela->sym->sec, rela->addend);
|
|
if (!func || func->type != STT_FUNC)
|
|
continue;
|
|
break;
|
|
|
|
default:
|
|
WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
|
|
continue;
|
|
}
|
|
|
|
func_for_each_insn_all(file, func, insn)
|
|
insn->ignore = true;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is a whitelist of functions that is allowed to be called with AC set.
|
|
* The list is meant to be minimal and only contains compiler instrumentation
|
|
* ABI and a few functions used to implement *_{to,from}_user() functions.
|
|
*
|
|
* These functions must not directly change AC, but may PUSHF/POPF.
|
|
*/
|
|
static const char *uaccess_safe_builtin[] = {
|
|
/* KASAN */
|
|
"kasan_report",
|
|
"check_memory_region",
|
|
/* KASAN out-of-line */
|
|
"__asan_loadN_noabort",
|
|
"__asan_load1_noabort",
|
|
"__asan_load2_noabort",
|
|
"__asan_load4_noabort",
|
|
"__asan_load8_noabort",
|
|
"__asan_load16_noabort",
|
|
"__asan_storeN_noabort",
|
|
"__asan_store1_noabort",
|
|
"__asan_store2_noabort",
|
|
"__asan_store4_noabort",
|
|
"__asan_store8_noabort",
|
|
"__asan_store16_noabort",
|
|
/* KASAN in-line */
|
|
"__asan_report_load_n_noabort",
|
|
"__asan_report_load1_noabort",
|
|
"__asan_report_load2_noabort",
|
|
"__asan_report_load4_noabort",
|
|
"__asan_report_load8_noabort",
|
|
"__asan_report_load16_noabort",
|
|
"__asan_report_store_n_noabort",
|
|
"__asan_report_store1_noabort",
|
|
"__asan_report_store2_noabort",
|
|
"__asan_report_store4_noabort",
|
|
"__asan_report_store8_noabort",
|
|
"__asan_report_store16_noabort",
|
|
/* KCOV */
|
|
"write_comp_data",
|
|
"__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",
|
|
/* 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 (insn->type != INSN_JUMP_CONDITIONAL &&
|
|
insn->type != INSN_JUMP_UNCONDITIONAL)
|
|
continue;
|
|
|
|
if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
|
|
continue;
|
|
|
|
rela = find_rela_by_dest_range(insn->sec, insn->offset,
|
|
insn->len);
|
|
if (!rela) {
|
|
dest_sec = insn->sec;
|
|
dest_off = insn->offset + insn->len + insn->immediate;
|
|
} else if (rela->sym->type == STT_SECTION) {
|
|
dest_sec = rela->sym->sec;
|
|
dest_off = rela->addend + 4;
|
|
} else if (rela->sym->sec->idx) {
|
|
dest_sec = rela->sym->sec;
|
|
dest_off = rela->sym->sym.st_value + rela->addend + 4;
|
|
} else 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;
|
|
}
|
|
|
|
/*
|
|
* 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(insn->sec, insn->offset,
|
|
insn->len);
|
|
if (!rela) {
|
|
dest_off = insn->offset + insn->len + insn->immediate;
|
|
insn->call_dest = find_symbol_by_offset(insn->sec,
|
|
dest_off);
|
|
|
|
if (!insn->call_dest && !insn->ignore) {
|
|
WARN_FUNC("unsupported intra-function call",
|
|
insn->sec, insn->offset);
|
|
if (retpoline)
|
|
WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
|
|
return -1;
|
|
}
|
|
|
|
} else if (rela->sym->type == STT_SECTION) {
|
|
insn->call_dest = find_symbol_by_offset(rela->sym->sec,
|
|
rela->addend+4);
|
|
if (!insn->call_dest ||
|
|
insn->call_dest->type != STT_FUNC) {
|
|
WARN_FUNC("can't find call dest symbol at %s+0x%x",
|
|
insn->sec, insn->offset,
|
|
rela->sym->sec->name,
|
|
rela->addend + 4);
|
|
return -1;
|
|
}
|
|
} else
|
|
insn->call_dest = rela->sym;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* The .alternatives section requires some extra special care, over and above
|
|
* what other special sections require:
|
|
*
|
|
* 1. Because alternatives are patched in-place, we need to insert a fake jump
|
|
* instruction at the end so that validate_branch() skips all the original
|
|
* replaced instructions when validating the new instruction path.
|
|
*
|
|
* 2. An added wrinkle is that the new instruction length might be zero. In
|
|
* that case the old instructions are replaced with noops. We simulate that
|
|
* by creating a fake jump as the only new instruction.
|
|
*
|
|
* 3. In some cases, the alternative section includes an instruction which
|
|
* conditionally jumps to the _end_ of the entry. We have to modify these
|
|
* jumps' destinations to point back to .text rather than the end of the
|
|
* entry in .altinstr_replacement.
|
|
*/
|
|
static int handle_group_alt(struct objtool_file *file,
|
|
struct special_alt *special_alt,
|
|
struct instruction *orig_insn,
|
|
struct instruction **new_insn)
|
|
{
|
|
struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
|
|
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 = true;
|
|
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);
|
|
clear_insn_state(&fake_jump->state);
|
|
|
|
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;
|
|
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;
|
|
|
|
if (insn->type != INSN_JUMP_CONDITIONAL &&
|
|
insn->type != INSN_JUMP_UNCONDITIONAL)
|
|
continue;
|
|
|
|
if (!insn->immediate)
|
|
continue;
|
|
|
|
dest_off = insn->offset + insn->len + insn->immediate;
|
|
if (dest_off == special_alt->new_off + special_alt->new_len) {
|
|
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) {
|
|
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 *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->list != &file->insn_list &&
|
|
insn->sec == func->sec &&
|
|
insn->offset >= func->offset;
|
|
|
|
insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
|
|
|
|
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(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. */
|
|
table_rela = find_rela_by_dest(table_sec, table_offset);
|
|
if (!table_rela)
|
|
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_all(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_all(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(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->state.cfa;
|
|
|
|
if (hint->type == UNWIND_HINT_TYPE_SAVE) {
|
|
insn->save = true;
|
|
continue;
|
|
|
|
} else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
|
|
insn->restore = true;
|
|
insn->hint = true;
|
|
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->state.type = hint->type;
|
|
insn->state.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 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.")) ||
|
|
!strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
|
|
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 = 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;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static bool is_fentry_call(struct instruction *insn)
|
|
{
|
|
if (insn->type == INSN_CALL &&
|
|
insn->call_dest->type == STT_NOTYPE &&
|
|
!strcmp(insn->call_dest->name, "__fentry__"))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool has_modified_stack_frame(struct insn_state *state)
|
|
{
|
|
int i;
|
|
|
|
if (state->cfa.base != initial_func_cfi.cfa.base ||
|
|
state->cfa.offset != initial_func_cfi.cfa.offset ||
|
|
state->stack_size != initial_func_cfi.cfa.offset ||
|
|
state->drap)
|
|
return true;
|
|
|
|
for (i = 0; i < CFI_NUM_REGS; i++)
|
|
if (state->regs[i].base != initial_func_cfi.regs[i].base ||
|
|
state->regs[i].offset != initial_func_cfi.regs[i].offset)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool has_valid_stack_frame(struct insn_state *state)
|
|
{
|
|
if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
|
|
state->regs[CFI_BP].offset == -16)
|
|
return true;
|
|
|
|
if (state->drap && state->regs[CFI_BP].base == CFI_BP)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
|
|
{
|
|
struct cfi_reg *cfa = &state->cfa;
|
|
struct stack_op *op = &insn->stack_op;
|
|
|
|
if (cfa->base != CFI_SP)
|
|
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 insn_state *state, unsigned char reg, int base,
|
|
int offset)
|
|
{
|
|
if (arch_callee_saved_reg(reg) &&
|
|
state->regs[reg].base == CFI_UNDEFINED) {
|
|
state->regs[reg].base = base;
|
|
state->regs[reg].offset = offset;
|
|
}
|
|
}
|
|
|
|
static void restore_reg(struct insn_state *state, unsigned char reg)
|
|
{
|
|
state->regs[reg].base = CFI_UNDEFINED;
|
|
state->regs[reg].offset = 0;
|
|
}
|
|
|
|
/*
|
|
* 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_insn_state(struct instruction *insn, struct insn_state *state)
|
|
{
|
|
struct stack_op *op = &insn->stack_op;
|
|
struct cfi_reg *cfa = &state->cfa;
|
|
struct cfi_reg *regs = state->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 (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
|
|
return update_insn_state_regs(insn, state);
|
|
|
|
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;
|
|
state->bp_scratch = false;
|
|
}
|
|
|
|
else if (op->src.reg == CFI_SP &&
|
|
op->dest.reg == CFI_BP && state->drap) {
|
|
|
|
/* drap: mov %rsp, %rbp */
|
|
regs[CFI_BP].base = CFI_BP;
|
|
regs[CFI_BP].offset = -state->stack_size;
|
|
state->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
|
|
*/
|
|
state->vals[op->dest.reg].base = CFI_CFA;
|
|
state->vals[op->dest.reg].offset = -state->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).
|
|
*/
|
|
state->stack_size = -state->regs[CFI_BP].offset;
|
|
}
|
|
|
|
else if (op->dest.reg == cfa->base) {
|
|
|
|
/* mov %reg, %rsp */
|
|
if (cfa->base == CFI_SP &&
|
|
state->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 = -state->vals[op->src.reg].offset;
|
|
state->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 */
|
|
state->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 */
|
|
state->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 */
|
|
state->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
|
|
*/
|
|
state->vals[op->dest.reg].base = CFI_CFA;
|
|
state->vals[op->dest.reg].offset = \
|
|
-state->stack_size + op->src.offset;
|
|
|
|
break;
|
|
}
|
|
|
|
if (state->drap && op->dest.reg == CFI_SP &&
|
|
op->src.reg == state->drap_reg) {
|
|
|
|
/* drap: lea disp(%drap), %rsp */
|
|
cfa->base = CFI_SP;
|
|
cfa->offset = state->stack_size = -op->src.offset;
|
|
state->drap_reg = CFI_UNDEFINED;
|
|
state->drap = false;
|
|
break;
|
|
}
|
|
|
|
if (op->dest.reg == state->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 ||
|
|
(state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
|
|
(state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
|
|
WARN_FUNC("unsupported stack pointer realignment",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
if (state->drap_reg != CFI_UNDEFINED) {
|
|
/* drap: and imm, %rsp */
|
|
cfa->base = state->drap_reg;
|
|
cfa->offset = state->stack_size = 0;
|
|
state->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 (!state->drap && op->dest.type == OP_DEST_REG &&
|
|
op->dest.reg == cfa->base) {
|
|
|
|
/* pop %rbp */
|
|
cfa->base = CFI_SP;
|
|
}
|
|
|
|
if (state->drap && cfa->base == CFI_BP_INDIRECT &&
|
|
op->dest.type == OP_DEST_REG &&
|
|
op->dest.reg == state->drap_reg &&
|
|
state->drap_offset == -state->stack_size) {
|
|
|
|
/* drap: pop %drap */
|
|
cfa->base = state->drap_reg;
|
|
cfa->offset = 0;
|
|
state->drap_offset = -1;
|
|
|
|
} else if (regs[op->dest.reg].offset == -state->stack_size) {
|
|
|
|
/* pop %reg */
|
|
restore_reg(state, op->dest.reg);
|
|
}
|
|
|
|
state->stack_size -= 8;
|
|
if (cfa->base == CFI_SP)
|
|
cfa->offset -= 8;
|
|
|
|
break;
|
|
|
|
case OP_SRC_REG_INDIRECT:
|
|
if (state->drap && op->src.reg == CFI_BP &&
|
|
op->src.offset == state->drap_offset) {
|
|
|
|
/* drap: mov disp(%rbp), %drap */
|
|
cfa->base = state->drap_reg;
|
|
cfa->offset = 0;
|
|
state->drap_offset = -1;
|
|
}
|
|
|
|
if (state->drap && op->src.reg == CFI_BP &&
|
|
op->src.offset == regs[op->dest.reg].offset) {
|
|
|
|
/* drap: mov disp(%rbp), %reg */
|
|
restore_reg(state, 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(state, 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:
|
|
state->stack_size += 8;
|
|
if (cfa->base == CFI_SP)
|
|
cfa->offset += 8;
|
|
|
|
if (op->src.type != OP_SRC_REG)
|
|
break;
|
|
|
|
if (state->drap) {
|
|
if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
|
|
|
|
/* drap: push %drap */
|
|
cfa->base = CFI_BP_INDIRECT;
|
|
cfa->offset = -state->stack_size;
|
|
|
|
/* save drap so we know when to restore it */
|
|
state->drap_offset = -state->stack_size;
|
|
|
|
} else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
|
|
|
|
/* drap: push %rbp */
|
|
state->stack_size = 0;
|
|
|
|
} else if (regs[op->src.reg].base == CFI_UNDEFINED) {
|
|
|
|
/* drap: push %reg */
|
|
save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
|
|
}
|
|
|
|
} else {
|
|
|
|
/* push %reg */
|
|
save_reg(state, op->src.reg, CFI_CFA, -state->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)
|
|
state->bp_scratch = true;
|
|
break;
|
|
|
|
case OP_DEST_REG_INDIRECT:
|
|
|
|
if (state->drap) {
|
|
if (op->src.reg == cfa->base && op->src.reg == state->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 */
|
|
state->drap_offset = op->dest.offset;
|
|
}
|
|
|
|
else if (regs[op->src.reg].base == CFI_UNDEFINED) {
|
|
|
|
/* drap: mov reg, disp(%rbp) */
|
|
save_reg(state, 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(state, op->src.reg, CFI_CFA,
|
|
op->dest.offset - state->cfa.offset);
|
|
}
|
|
|
|
break;
|
|
|
|
case OP_DEST_LEAVE:
|
|
if ((!state->drap && cfa->base != CFI_BP) ||
|
|
(state->drap && cfa->base != state->drap_reg)) {
|
|
WARN_FUNC("leave instruction with modified stack frame",
|
|
insn->sec, insn->offset);
|
|
return -1;
|
|
}
|
|
|
|
/* leave (mov %rbp, %rsp; pop %rbp) */
|
|
|
|
state->stack_size = -state->regs[CFI_BP].offset - 8;
|
|
restore_reg(state, CFI_BP);
|
|
|
|
if (!state->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 */
|
|
state->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 bool insn_state_match(struct instruction *insn, struct insn_state *state)
|
|
{
|
|
struct insn_state *state1 = &insn->state, *state2 = state;
|
|
int i;
|
|
|
|
if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
|
|
WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
|
|
insn->sec, insn->offset,
|
|
state1->cfa.base, state1->cfa.offset,
|
|
state2->cfa.base, state2->cfa.offset);
|
|
|
|
} else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
|
|
for (i = 0; i < CFI_NUM_REGS; i++) {
|
|
if (!memcmp(&state1->regs[i], &state2->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, state1->regs[i].base, state1->regs[i].offset,
|
|
i, state2->regs[i].base, state2->regs[i].offset);
|
|
break;
|
|
}
|
|
|
|
} else if (state1->type != state2->type) {
|
|
WARN_FUNC("stack state mismatch: type1=%d type2=%d",
|
|
insn->sec, insn->offset, state1->type, state2->type);
|
|
|
|
} else if (state1->drap != state2->drap ||
|
|
(state1->drap && state1->drap_reg != state2->drap_reg) ||
|
|
(state1->drap && state1->drap_offset != state2->drap_offset)) {
|
|
WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
|
|
insn->sec, insn->offset,
|
|
state1->drap, state1->drap_reg, state1->drap_offset,
|
|
state2->drap, state2->drap_reg, state2->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->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(state)) {
|
|
WARN_FUNC("sibling call from callable instruction with modified stack frame",
|
|
insn->sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
return validate_call(insn, state);
|
|
}
|
|
|
|
/*
|
|
* 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 *first, struct insn_state state)
|
|
{
|
|
struct alternative *alt;
|
|
struct instruction *insn, *next_insn;
|
|
struct section *sec;
|
|
u8 visited;
|
|
int ret;
|
|
|
|
insn = first;
|
|
sec = insn->sec;
|
|
|
|
if (insn->alt_group && list_empty(&insn->alts)) {
|
|
WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
|
|
sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
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_state_match(insn, &state))
|
|
return 1;
|
|
|
|
if (insn->visited & visited)
|
|
return 0;
|
|
}
|
|
|
|
if (insn->hint) {
|
|
if (insn->restore) {
|
|
struct instruction *save_insn, *i;
|
|
|
|
i = insn;
|
|
save_insn = NULL;
|
|
func_for_each_insn_continue_reverse(file, func, i) {
|
|
if (i->save) {
|
|
save_insn = i;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (!save_insn) {
|
|
WARN_FUNC("no corresponding CFI save for CFI restore",
|
|
sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (!save_insn->visited) {
|
|
/*
|
|
* Oops, no state to copy yet.
|
|
* Hopefully we can reach this
|
|
* instruction from another branch
|
|
* after the save insn has been
|
|
* visited.
|
|
*/
|
|
if (insn == first)
|
|
return 0;
|
|
|
|
WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
|
|
sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
insn->state = save_insn->state;
|
|
}
|
|
|
|
state = insn->state;
|
|
|
|
} else
|
|
insn->state = state;
|
|
|
|
insn->visited |= visited;
|
|
|
|
if (!insn->ignore_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 (skip_orig)
|
|
return 0;
|
|
}
|
|
|
|
switch (insn->type) {
|
|
|
|
case INSN_RETURN:
|
|
if (state.uaccess && !func_uaccess_safe(func)) {
|
|
WARN_FUNC("return with UACCESS enabled", sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (!state.uaccess && func_uaccess_safe(func)) {
|
|
WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (state.df) {
|
|
WARN_FUNC("return with DF set", sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (func && has_modified_stack_frame(&state)) {
|
|
WARN_FUNC("return with modified stack frame",
|
|
sec, insn->offset);
|
|
return 1;
|
|
}
|
|
|
|
if (state.bp_scratch) {
|
|
WARN("%s uses BP as a scratch register",
|
|
func->name);
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
|
|
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_STACK:
|
|
if (update_insn_state(insn, &state))
|
|
return 1;
|
|
|
|
if (insn->stack_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", sec, insn->offset);
|
|
return 1;
|
|
}
|
|
state.uaccess_stack <<= 1;
|
|
state.uaccess_stack |= state.uaccess;
|
|
}
|
|
|
|
if (insn->stack_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;
|
|
}
|
|
}
|
|
|
|
break;
|
|
|
|
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.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 instruction *insn;
|
|
int ret, warnings = 0;
|
|
struct insn_state state;
|
|
|
|
if (!file->hints)
|
|
return 0;
|
|
|
|
clear_insn_state(&state);
|
|
|
|
for_each_insn(file, insn) {
|
|
if (insn->hint && !insn->visited) {
|
|
ret = validate_branch(file, insn->func, insn, state);
|
|
if (ret && backtrace)
|
|
BT_FUNC("<=== (hint)", insn);
|
|
warnings += ret;
|
|
}
|
|
}
|
|
|
|
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;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (!insn->func)
|
|
return false;
|
|
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_functions(struct objtool_file *file)
|
|
{
|
|
struct section *sec;
|
|
struct symbol *func;
|
|
struct instruction *insn;
|
|
struct insn_state state;
|
|
int ret, warnings = 0;
|
|
|
|
clear_insn_state(&state);
|
|
|
|
state.cfa = initial_func_cfi.cfa;
|
|
memcpy(&state.regs, &initial_func_cfi.regs,
|
|
CFI_NUM_REGS * sizeof(struct cfi_reg));
|
|
state.stack_size = initial_func_cfi.cfa.offset;
|
|
|
|
for_each_sec(file, sec) {
|
|
list_for_each_entry(func, &sec->symbol_list, list) {
|
|
if (func->type != STT_FUNC)
|
|
continue;
|
|
|
|
if (!func->len) {
|
|
WARN("%s() is missing an ELF size annotation",
|
|
func->name);
|
|
warnings++;
|
|
}
|
|
|
|
if (func->pfunc != func || func->alias != func)
|
|
continue;
|
|
|
|
insn = find_insn(file, sec, func->offset);
|
|
if (!insn || insn->ignore || insn->visited)
|
|
continue;
|
|
|
|
state.uaccess = func->uaccess_safe;
|
|
|
|
ret = validate_branch(file, func, insn, state);
|
|
if (ret && backtrace)
|
|
BT_FUNC("<=== (func)", insn);
|
|
warnings += ret;
|
|
}
|
|
}
|
|
|
|
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 void cleanup(struct objtool_file *file)
|
|
{
|
|
struct instruction *insn, *tmpinsn;
|
|
struct alternative *alt, *tmpalt;
|
|
|
|
list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
|
|
list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
|
|
list_del(&alt->list);
|
|
free(alt);
|
|
}
|
|
list_del(&insn->list);
|
|
hash_del(&insn->hash);
|
|
free(insn);
|
|
}
|
|
elf_close(file->elf);
|
|
}
|
|
|
|
static struct objtool_file file;
|
|
|
|
int check(const char *_objname, bool orc)
|
|
{
|
|
int ret, warnings = 0;
|
|
|
|
objname = _objname;
|
|
|
|
file.elf = elf_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 (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);
|
|
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:
|
|
cleanup(&file);
|
|
|
|
/* ignore warnings for now until we get all the code cleaned up */
|
|
if (ret || warnings)
|
|
return 0;
|
|
return 0;
|
|
}
|