linux-kernel - Re: Regression in kernel 4.12-rc1 for Powerpc 32

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Date:   Wed, 21 Jun 2017 10:10:57 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     LKML <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...IV.linux.org.uk>
Cc:     Thorsten Leemhuis <regressions@...mhuis.info>
Subject: Re: Regression in kernel 4.12-rc1 for Powerpc 32 - bisected to commit
 3448890c32c3

On 06/01/2017 11:39 AM, Larry Finger wrote:
> On my Powerbook G4 aluminum, kernel 4.12-rc1 fails to boot. I cannot save a copy 
> of the early printk messages and I will need to summarize.
> 
> The kernel finds the hard driver and recognizes the various partitions. All 
> seems normal until after the "unused kernel memory is freed" and that "This 
> architecture does not have kernel memory protection", which are both normal. The 
> next batch of logged messages are
> 
> Loading, please wait...
> udevd[64]: starting version 175
> udevd[64]: Unable to receive ctrl message: Bad address.
> modprobe: chdir(4.12-rc1): No such file or directory
> udevd[64]: Unable to receive ctrl message: Bad address.
> Begin: Loading essential drivers ... modprobe: chdir: chdir(4.12.0-rc1): No such 
> file or directory
> done.
> Begin: Running /scripts/init-premount ... done.
> udevd[64]: Begin: Waiting for root file system ... [   11.651175] random: faast 
> init done
> done.
> Gave up waiting for root device. Common problems:
>   - Boot args (cat /proc/cmdline)
>     - Check rootdelay= (did the system wait long enough?)
>     - Check root= (Did the system wait for the right device?)
>   - Missing modules (cat /proc/modules; ls /dev)
> ALERT! /dev/disk/by-uuid/<UUID> does not exist. Dropping to a shell!
> modprobe: chdir(4.12-rc1): No such file or directory <listed 6 times>
> 
> BusyBox v1.20.2 (Debian 1:1.20.0-7) built-in shell (ash)
> Enter 'help' for a list of built-in commands.
> 
> /bin/sh: can't access tty: Job control turned off
> (initramfs)
> 
> At that point, the system is dead. I have tried bisecting this issue; however, I 
> run into a second problem that crashes the bootstrap.

I finally finished the bisection by patching each commit that was affected by 
the bootstrap crash. The faulty change is commit 
3448890c32c32c482c3ec20baa8fdd2ab4f94cc0 ("powerpc: get rid of zeroing, switch 
to RAW_COPY_USER"). I am very confident in the bisection.

As I know nothing of assembly for ppc32, I have not been able to attempt to find 
the problem with these patches.

Larry