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SubjectRe: [PATCH] Improve usability in case of init binary failure
On Sun, 27 Dec 2009, Andreas Mohr wrote:

> Well, took quite a while longer, partly due to broken Broadcom USB host
> (OpenWrt fix to be submitted) and non-working USB-audio on nicer platforms.
>
> Took most of the comments into account (thanks!), improved some wording.
>
> Patch against current git, compile- and runtime-tested,
> checkpatch.pl'd (with a single nice hierarchy warning resulting from mixing
> git diff output and manual /dev/null diffing).
>
> Thanks!
>

It looks like this patch got mangled when added to mmotm-2010-02-01-16-25
in init-mainc-improve-usability-in-case-of-init-binary-failure.patch since
it added init.txt to the root directory instead of Documentation, even
though the patch below is correct.

> Signed-off-by: Andreas Mohr <andi@lisas.de>
>
> diff --git a/init/main.c b/init/main.c
> index dac44a9..33748c6 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -836,7 +836,8 @@ static noinline int init_post(void)
> run_init_process("/bin/init");
> run_init_process("/bin/sh");
>
> - panic("No init found. Try passing init= option to kernel.");
> + panic("No init found. Try passing init= option to kernel. "
> + "See Linux Documentation/init.txt for guidance.");
> }
>
> static int __init kernel_init(void * unused)
> --- /dev/null 2009-12-27 16:25:29.521258205 +0100
> +++ Documentation/init.txt 2009-12-27 15:47:46.000000000 +0100
> @@ -0,0 +1,49 @@
> +Explaining the dreaded "No init found." boot hang message
> +=========================================================
> +
> +OK, so you've got this pretty unintuitive message (currently located
> +in init/main.c) and are wondering what the H*** went wrong.
> +Some high-level reasons for failure (listed roughly in order of execution)
> +to load the init binary are:
> +A) Unable to mount root FS
> +B) init binary doesn't exist on rootfs
> +C) broken console device
> +D) binary exists but dependencies not available
> +E) binary cannot be loaded
> +
> +Detailed explanations:
> +0) Set "debug" kernel parameter (in bootloader config file or CONFIG_CMDLINE)
> + to get more detailed kernel messages.
> +A) make sure you have the correct root FS type
> + (and root= kernel parameter points to the correct partition),
> + required drivers such as storage hardware (such as SCSI or USB!)
> + and filesystem (ext3, jffs2 etc.) are builtin (alternatively as modules,
> + to be pre-loaded by an initrd)
> +C) Possibly a conflict in console= setup --> initial console unavailable.
> + E.g. some serial consoles are unreliable due to serial IRQ issues (e.g.
> + missing interrupt-based configuration).
> + Try using a different console= device or e.g. netconsole= .
> +D) e.g. required library dependencies of the init binary such as
> + /lib/ld-linux.so.2 missing or broken. Use readelf -d <INIT>|grep NEEDED
> + to find out which libraries are required.
> +E) make sure the binary's architecture matches your hardware.
> + E.g. i386 vs. x86_64 mismatch, or trying to load x86 on ARM hardware.
> + In case you tried loading a non-binary file here (shell script?),
> + you should make sure that the script specifies an interpreter in its shebang
> + header line (#!/...) that is fully working (including its library
> + dependencies). And before tackling scripts, better first test a simple
> + non-script binary such as /bin/sh and confirm its successful execution.
> + To find out more, add code to init/main.c to display kernel_execve()s
> + return values.
> +
> +Please extend this explanation whenever you find new failure causes
> +(after all loading the init binary is a CRITICAL and hard transition step
> +which needs to be made as painless as possible), then submit patch to LKML.
> +Further TODOs:
> +- Implement the various run_init_process() invocations via a struct array
> + which can then store the kernel_execve() result value and on failure
> + log it all by iterating over _all_ results (very important usability fix).
> +- try to make the implementation itself more helpful in general,
> + e.g. by providing additional error messages at affected places.
> +
> +Andreas Mohr <andi at lisas period de>


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