Re: [PATCH 1/2] init: ensure that /dev/console is (nearly) always available in initramfs

On 2/23/26 11:34, Askar Safin wrote:
> Rob Landley <[email protected]>:
>> The real problem isn't cpio, it's that the kernel interface
> 
> So there is some bug here?
> 
> Then, please, describe properly this bug.
> 
> I. e. using usual formula "steps to reproduce - what I got - what I expected to see".

I think that the kernel special case creating files in initramfs is the 
wrong design approach, but it would address the problem and it's what 
the kernel already did in a different codepath.

> Also, does the kernel broke *documented* feature? If indeed some
> *documented* feature doesn't work, then this is indeed very real bug.

Documentation/filesystems/ramfs-rootfs-initramfs.txt section "populating 
initramfs" described using the text file format back in 2005 
(https://github.com/mpe/linux-fullhistory/commit/7f46a240b0a1 line 135) 
and then commit 
https://github.com/mpe/linux-fullhistory/commit/99aef427e206f a year 
later described running usr/gen_init_cpio to create those files from a 
directory to give you an easy starting point to edit.

But I wrote that documentation, so it probably doesn't count.

> I kindly ask you, please, please, describe this bug. I really want
> to help you.
Back when the gen_init_cpio stuff let you create the file and consume 
the file separately so you could edit it in between, there was an easy 
way to address this problem by creating a cpio containing /dev/console 
as a regular user using the kernel plumbing. Then the kernel broke that 
and created a regression, which they decided to fix with special case 
code doing mknod within the kernel before launching PID 1, but only for 
one of two codepaths.

I think adding the special case hack to the other codepath is the wrong 
_WAY_ to fix it... but I guess that ship has sailed. I agree doing that 
can avoid the "init has no stdin/stdout/stderr" problem and thus address 
the issue.

(I still think if you have a CONFIG_DEVTMPFS_MOUNT config symbol, it 
should actually work, but that's a somewhat separate issue and a 
half-dozen patches ignored by linux-kernel for a decade now apparently 
argue otherwise...)

Rob