switch_root: don't bail out when console doesn't exist

Busybox is very often used in initramfs at the end of which usually
there is a switch_root to the actual rootfs. There are many cases where
the console kernel argument is either just a placeholder (for example
RaspberryPi uses serial0 and serial1) or configured as null to avoid any
console messages - usually you would see such of a setup in production
environments.

Currently busybox bails out if can't open the console argument. If this
happenes in initramfs and if the console=null for example, you get in a
blind kernel panic. Avoid this by only warning instead of dying.

function                                             old     new   delta
switch_root_main                                     371     368      -3

Signed-off-by: Andrei Gherzan <andrei@gherzan.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/util-linux/switch_root.c b/util-linux/switch_root.c
index 6034485d7..aaee35a3e 100644
--- a/util-linux/switch_root.c
+++ b/util-linux/switch_root.c
@@ -141,10 +141,12 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
 
         // If a new console specified, redirect stdin/stdout/stderr to it
         if (console) {
-                close(0);
-                xopen(console, O_RDWR);
-                xdup2(0, 1);
-                xdup2(0, 2);
+                int fd = open_or_warn(console, O_RDWR);
+                if (fd >= 0) {
+                        xmove_fd(fd, 0);
+                        xdup2(0, 1);
+                        xdup2(0, 2);
+                }
         }
 
         // Exec real init