[patch 115/262] mm: create a new system state and fix core_kernel_text()

Andrew Morton
2021-11-05T20:40:43Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>
Subject: mm: create a new system state and fix core_kernel_text()

core_kernel_text() considers that until system_state in at least
SYSTEM_RUNNING, init memory is valid.

But init memory is freed a few lines before setting SYSTEM_RUNNING, so we
have a small period of time when core_kernel_text() is wrong.

Create an intermediate system state called SYSTEM_FREEING_INIT that is set
before starting freeing init memory, and use it in core_kernel_text() to
report init memory invalid earlier.

Link: https://lkml.kernel.org/r/9ecfdee7dd4d741d172cb93ff1d87f1c58127c9a.1633001016.git.christophe.leroy@csgroup.eu
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/kernel.h | 1 +
init/main.c | 2 ++
kernel/extable.c | 2 +-
3 files changed, 4 insertions(+), 1 deletion(-)

--- a/include/linux/kernel.h~mm-create-a-new-system-state-and-fix-core_kernel_text
+++ a/include/linux/kernel.h
@@ -248,6 +248,7 @@ extern bool early_boot_irqs_disabled;
extern enum system_states {
SYSTEM_BOOTING,
SYSTEM_SCHEDULING,
+ SYSTEM_FREEING_INITMEM,
SYSTEM_RUNNING,
SYSTEM_HALT,
SYSTEM_POWER_OFF,
--- a/init/main.c~mm-create-a-new-system-state-and-fix-core_kernel_text
+++ a/init/main.c
@@ -1506,6 +1506,8 @@ static int __ref kernel_init(void *unuse
kernel_init_freeable();
/* need to finish all async __init code before freeing the memory */
async_synchronize_full();
+
+ system_state = SYSTEM_FREEING_INITMEM;
kprobe_free_init_mem();
ftrace_free_init_mem();
kgdb_free_init_mem();
--- a/kernel/extable.c~mm-create-a-new-system-state-and-fix-core_kernel_text
+++ a/kernel/extable.c
@@ -76,7 +76,7 @@ int notrace core_kernel_text(unsigned lo
addr < (unsigned long)_etext)
return 1;

- if (system_state < SYSTEM_RUNNING &&
+ if (system_state < SYSTEM_FREEING_INITMEM &&
init_kernel_text(addr))
return 1;
return 0;
_