[BUG] Device node major comes out wrong on HFS+ under linux

[BUG] Device node major comes out wrong on HFS+ under linux

[DagB]

Hi.

Executive summary:

/dev/null:
osx:	crw-rw-rw- 1 root wheel 1, 3 Oct 13 04:12 null	
linux:	crw-rw-rw- 1 root root 16, 3 Oct 13 02:12 /dev/null

/dev/console:
osx:	crw------- 1 root wheel 5, 1 Oct 13 04:12 console
linux:	crw------- 1 root root 80, 1 Oct 13 02:12 /dev/console

/dev/sda4:
osx:	brw-r----- 1 root wheel  8, 4 Oct 13 04:12 sda4
linux:	brw-r----- 1 root root 128, 4 Oct 13 02:12 /dev/sda4




Details:

I am slowly figuring out how to boot linux on my shiny new macbook air.

The actual *booting* bit turns out to be incredibly easy with rEFIt,
keithp's macbook air tree, and mfleming's efi stub tree. (3.1.0-ish)
Just pop a suitable kernel somewhere rEFIt can see it, and off you go.
No mucking with bootloaders or repartitioning with esoteric tools and
options. Slick. Got to use a built-in kernel command line, though.

Shrinking the existing OSX HFS+ partition and adding another for a linux
root fs from within OSX also turned out to be a breeze.

I decided to give HFS+ a go for the root fs, just for a POC.
(I'll make an initramfs for making a sane fs. Would be cooler to do
everything from within OSX, and just reboot straight into Linux.)

Untarring a root fs on a my new HFS+ filesystem was straightforward. I
*do* get a warning from OSX' tar when creating the devicenodes, but the
nodes are created with the correct perms and major/minor.

tar: qtn_file_apply_to_path(./dev/console): Operation not permitted
results in (when viewed from OSX):

crw-------  1 root  wheel    5,   1 Oct 13 04:12 dev/console
which nicely reflects what the source filesystem has.


Booting a linux kernel (with init=/bin/sh) results in:
crw------- 1 root wheel	80, 1	Oct 13 02:12 /dev/console

Clearly a Major bug.  ("ka-pisch".....)



Looks like an endianness issue at hand here:
1 p
1
16 p
10000


5 p
101
80 p
1010000


8 p
1000
128 p
10000000


Good thing I didn't end up trying to dial out through my HDD....


Anyone care to squash this bug, please?

Dag B

Re: [BUG] Device node major comes out wrong on HFS+ under linux

[Thomas Meyer]

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Am Samstag, den 15.10.2011, 20:04 +0200 schrieb DagB:
> Hi.
> 
> Executive summary:
> 
> /dev/null:
> osx:	crw-rw-rw- 1 root wheel 1, 3 Oct 13 04:12 null	
> linux:	crw-rw-rw- 1 root root 16, 3 Oct 13 02:12 /dev/null
> 
> /dev/console:
> osx:	crw------- 1 root wheel 5, 1 Oct 13 04:12 console
> linux:	crw------- 1 root root 80, 1 Oct 13 02:12 /dev/console
> 
> /dev/sda4:
> osx:	brw-r----- 1 root wheel  8, 4 Oct 13 04:12 sda4
> linux:	brw-r----- 1 root root 128, 4 Oct 13 02:12 /dev/sda4

> 
> Anyone care to squash this bug, please?
> 

This is not a bug. Linux uses a 12/20 split for major and minor device
ids and the xnu kernel uses a 8/24 split:

8, 4
00001000 000000000000000000000100
= 128, 4
000010000000 00000000000000000100

with kind regards
thomas


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