linux-stable/arch/x86/kernel/jump_label.c
Ingo Molnar e48a12e546 jump_labels: Mark __jump_label_transform() as __always_inlined to work around aggressive compiler un-inlining
In randconfig testing, certain UBSAN and CC Kconfig combinations
with GCC 10.3.0:

  CONFIG_X86_32=y

  CONFIG_CC_OPTIMIZE_FOR_SIZE=y

  CONFIG_UBSAN=y
  # CONFIG_UBSAN_TRAP is not set
  # CONFIG_UBSAN_BOUNDS is not set
  CONFIG_UBSAN_SHIFT=y
  # CONFIG_UBSAN_DIV_ZERO is not set
  CONFIG_UBSAN_UNREACHABLE=y
  CONFIG_UBSAN_BOOL=y
  # CONFIG_UBSAN_ENUM is not set
  # CONFIG_UBSAN_ALIGNMENT is not set
  # CONFIG_UBSAN_SANITIZE_ALL is not set

... produce this build warning (and build error if
CONFIG_SECTION_MISMATCH_WARN_ONLY=y is set):

  WARNING: modpost: vmlinux.o(.text+0x4c1cc): Section mismatch in reference from the function __jump_label_transform() to the function .init.text:text_poke_early()
  The function __jump_label_transform() references
  the function __init text_poke_early().
  This is often because __jump_label_transform lacks a __init
  annotation or the annotation of text_poke_early is wrong.

  ERROR: modpost: Section mismatches detected.

The problem is that __jump_label_transform() gets uninlined by GCC,
despite there being only a single local scope user of the 'static inline'
function.

Mark the function __always_inline instead, to work around this compiler
bug/artifact.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2021-07-13 06:32:05 +02:00

161 lines
3.9 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* jump label x86 support
*
* Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
*
*/
#include <linux/jump_label.h>
#include <linux/memory.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/cpu.h>
#include <asm/kprobes.h>
#include <asm/alternative.h>
#include <asm/text-patching.h>
#include <asm/insn.h>
int arch_jump_entry_size(struct jump_entry *entry)
{
struct insn insn = {};
insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
BUG_ON(insn.length != 2 && insn.length != 5);
return insn.length;
}
struct jump_label_patch {
const void *code;
int size;
};
static struct jump_label_patch
__jump_label_patch(struct jump_entry *entry, enum jump_label_type type)
{
const void *expect, *code, *nop;
const void *addr, *dest;
int size;
addr = (void *)jump_entry_code(entry);
dest = (void *)jump_entry_target(entry);
size = arch_jump_entry_size(entry);
switch (size) {
case JMP8_INSN_SIZE:
code = text_gen_insn(JMP8_INSN_OPCODE, addr, dest);
nop = x86_nops[size];
break;
case JMP32_INSN_SIZE:
code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest);
nop = x86_nops[size];
break;
default: BUG();
}
if (type == JUMP_LABEL_JMP)
expect = nop;
else
expect = code;
if (memcmp(addr, expect, size)) {
/*
* The location is not an op that we were expecting.
* Something went wrong. Crash the box, as something could be
* corrupting the kernel.
*/
pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph != %5ph)) size:%d type:%d\n",
addr, addr, addr, expect, size, type);
BUG();
}
if (type == JUMP_LABEL_NOP)
code = nop;
return (struct jump_label_patch){.code = code, .size = size};
}
static __always_inline void
__jump_label_transform(struct jump_entry *entry,
enum jump_label_type type,
int init)
{
const struct jump_label_patch jlp = __jump_label_patch(entry, type);
/*
* As long as only a single processor is running and the code is still
* not marked as RO, text_poke_early() can be used; Checking that
* system_state is SYSTEM_BOOTING guarantees it. It will be set to
* SYSTEM_SCHEDULING before other cores are awaken and before the
* code is write-protected.
*
* At the time the change is being done, just ignore whether we
* are doing nop -> jump or jump -> nop transition, and assume
* always nop being the 'currently valid' instruction
*/
if (init || system_state == SYSTEM_BOOTING) {
text_poke_early((void *)jump_entry_code(entry), jlp.code, jlp.size);
return;
}
text_poke_bp((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
}
static void __ref jump_label_transform(struct jump_entry *entry,
enum jump_label_type type,
int init)
{
mutex_lock(&text_mutex);
__jump_label_transform(entry, type, init);
mutex_unlock(&text_mutex);
}
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
jump_label_transform(entry, type, 0);
}
bool arch_jump_label_transform_queue(struct jump_entry *entry,
enum jump_label_type type)
{
struct jump_label_patch jlp;
if (system_state == SYSTEM_BOOTING) {
/*
* Fallback to the non-batching mode.
*/
arch_jump_label_transform(entry, type);
return true;
}
mutex_lock(&text_mutex);
jlp = __jump_label_patch(entry, type);
text_poke_queue((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
mutex_unlock(&text_mutex);
return true;
}
void arch_jump_label_transform_apply(void)
{
mutex_lock(&text_mutex);
text_poke_finish();
mutex_unlock(&text_mutex);
}
static enum {
JL_STATE_START,
JL_STATE_NO_UPDATE,
JL_STATE_UPDATE,
} jlstate __initdata_or_module = JL_STATE_START;
__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
enum jump_label_type type)
{
if (jlstate == JL_STATE_UPDATE)
jump_label_transform(entry, type, 1);
}