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Subject[PATCH] Wire up CONFIG_DEVTMPFS_MOUNT to initramfs.
Date
From: Rob Landley <rob@landley.net>

The kernel has had CONFIG_DEVTMPFS_MOUNT for years, but it only applied to
fallback ROOT= not initramfs/initmpfs. As long as the config option exists, it
might as well work.

I use this for board bringup: populating a chdir and calling cpio as a normal
user often leaves /dev empty (because mknod requires root access), meaning no
/dev/console for init/main.c to open, meaning init runs without
stdin/stdout/stderr and has to mount devtmpfs and redirect the filehandles blind
with no error output if something goes wrong.

Signed-off-by: Rob Landley <rob@landley.net>
---
Previously: https://lkml.org/lkml/2017/9/13/651

init/main.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/init/main.c b/init/main.c
index bb984ed79de0..288c73db57f4 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1612,7 +1612,6 @@ static noinline void __init kernel_init_freeable(void)
kunit_run_all_tests();

wait_for_initramfs();
- console_on_rootfs();

/*
* check if there is an early userspace init. If yes, let it do all
@@ -1621,7 +1620,11 @@ static noinline void __init kernel_init_freeable(void)
if (init_eaccess(ramdisk_execute_command) != 0) {
ramdisk_execute_command = NULL;
prepare_namespace();
+ } else if (IS_ENABLED(CONFIG_DEVTMPFS_MOUNT)) {
+ sys_mkdir("/dev", 0755);
+ devtmpfs_mount();
}
+ console_on_rootfs();

/*
* Ok, we have completed the initial bootup, and
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