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MORIN" To: Vineet Gupta Subject: Re: [Buildroot] ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console) Message-ID: <20210107152724.GL1485369@scaer> References: <20201111135450.11214-1-pmladek@suse.com> <20201111135450.11214-2-pmladek@suse.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.22 (2013-10-16) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210107_102805_116215_249C67D5 X-CRM114-Status: GOOD ( 18.32 ) X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Petr Mladek , Sergey Senozhatsky , John Ogness , Shreyas Joshi , linux-kernel@vger.kernel.org, Steven Rostedt , Sergey Senozhatsky , Thomas Petazzoni , Greg Kroah-Hartman , buildroot@busybox.net, arcml , Linus Torvalds , shreyasjoshi15@gmail.com, Guenter Roeck Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org Vineet, All, On 2021-01-06 15:36 -0800, Vineet Gupta spake thusly: > On 11/11/20 5:54 AM, Petr Mladek wrote: [--SNIP--] > >Make sure that stdin, stdout, stderr, and /dev/console are always > >available by a fallback to the existing ttynull driver. It has > >been implemented for exactly this purpose but it was used only > >when explicitly configured. > > > >Signed-off-by: Petr Mladek > > >--- a/init/main.c > >+++ b/init/main.c > >@@ -1470,8 +1470,14 @@ void __init console_on_rootfs(void) > > struct file *file = filp_open("/dev/console", O_RDWR, 0); > > if (IS_ERR(file)) { > >- pr_err("Warning: unable to open an initial console.\n"); > >- return; > >+ pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n"); > >+ register_ttynull_console(); > >+ > >+ file = filp_open("/dev/console", O_RDWR, 0); > >+ if (IS_ERR(file)) { > >+ pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n"); > >+ return; > >+ } > > This breaks ARC booting (no output on console). > > Our Buildroot based setup has dynamic /dev where /dev/console doesn't exist > statically and there's a primoridla /init shell script which does following > > /bin/mount -t devtmpfs devtmpfs /dev > exec 0 exec 1>/dev/console > exec 2>/dev/console > exec /sbin/init "$@" I guess you are speaking about the initramfs (cpio) case, right? We've changed that code last August: https://git.buildroot.org/buildroot/commit/fs/cpio/init?id=b9026e83f I.e. if we can't do the redirection, then we don't redirect anything. The change was done for people who explicitly pass an empty console= on their kernel command line. Now, I haven't looked at nulltty yet, and I have (so far) no idea on how it works. Thanks for the hint, I'll have a look. > Buildroot has had this way of handling missing /dev/console since 2011 [1] > and [2]. See also more archaelogy on that topic, referenced in that commit: https://git.buildroot.org/buildroot/commit/fs/cpio/?id=98a6f1fc02e41 > Please advise what needs to be done to unbork boot. This has been present since the 2020.08 release, and has been backported to the maintenance branches: 2020.02.x (LTS) -> f1a83afe2df2a 2020.05.x -> 797f9e40224c9 > Otherwise this seems > like a kernel change which breaks user-space and needs to be backed-out (or > perhaps conditionalize on CONFIG_NULL_TTY. I'm surprised it hasn't been > reported by any other embedded folks I won't speak about whether this is a kernel regression or not, not my call. Regards, Yann E. MORIN. -- .-----------------.--------------------.------------------.--------------------. | Yann E. 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