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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/init/main.c b/init/main.c
index 3c4054a95545..767ee2672176 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1506,6 +1506,8 @@ static int __ref kernel_init(void *unused)
 	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();