From: Rob Landley To: linux-kernel@vger.kernel.org Cc: Andrew Morton ,"Steven Rostedt (Google)" , "Jason A. Donenfeld" ,Masami Hiramatsu ,Peter Zijlstra ,Mark Rutland ,Mark-PK Tsai ,Alexey Dobriyan ,Li Zhe Date: Sun, 16 Jan 2022 12:36:49 -0600 Subject: [PATCH 3/5] Wire up CONFIG_DEVTMPFS_MOUNT to initramfs. 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 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 e1c3911d7c70..eca7ba2c2764 100644 --- a/init/main.c +++ b/init/main.c @@ -1636,7 +1636,6 @@ 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 @@ -1645,7 +1644,11 @@ 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)) { + init_mkdir("/dev", 0755); + devtmpfs_mount(); } + console_on_rootfs(); /* * Ok, we have completed the initial bootup, and -- 2.20.1