linux-kernel - [PATCH 18/23] init: open code setting up stdin/stdout/stderr

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Date:   Tue, 14 Jul 2020 21:04:22 +0200
From:   Christoph Hellwig <hch@....de>
To:     linux-kernel@...r.kernel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>, Song Liu <song@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-raid@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH 18/23] init: open code setting up stdin/stdout/stderr

Don't rely on the implicit set_fs(KERNEL_DS) for ksys_open to work, but
instead open a struct file for /dev/console and then install it as FD
0/1/2 manually.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 init/main.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/init/main.c b/init/main.c
index 0ead83e86b5aa2..db0621dfbb0468 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1457,15 +1457,19 @@ static int __ref kernel_init(void *unused)
 	      "See Linux Documentation/admin-guide/init.rst for guidance.");
 }
 
+/* Open /dev/console, for stdin/stdout/stderr, this should never fail */
 void console_on_rootfs(void)
 {
-	/* Open the /dev/console as stdin, this should never fail */
-	if (ksys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
-		pr_err("Warning: unable to open an initial console.\n");
+	struct file *file = filp_open("/dev/console", O_RDWR, 0);
 
-	/* create stdout/stderr */
-	(void) ksys_dup(0);
-	(void) ksys_dup(0);
+	if (IS_ERR(file)) {
+		pr_err("Warning: unable to open an initial console.\n");
+		return;
+	}
+	get_file_rcu_many(file, 2);
+	fd_install(get_unused_fd_flags(0), file);
+	fd_install(get_unused_fd_flags(0), file);
+	fd_install(get_unused_fd_flags(0), file);
 }
 
 static noinline void __init kernel_init_freeable(void)
-- 
2.27.0