Subject: Re: Where/how is rootvp set in kernel initialisation?
To: None <firstname.lastname@example.org>
From: Bill Studenmund <email@example.com>
Date: 09/19/2000 12:57:45
On Tue, 19 Sep 2000 firstname.lastname@example.org wrote:
> Background: I am the maintainer of the Booter program for the Mac68k
> port, and I am trying to build a MacOS program which uses
> the actual kernel code for doing FFS volume manipulation
> (instead of the hacked old UFS code it uses now).
> Status: I have a few libraries of the relevant files from the syssrc
> archive, and a hacked together main. When my main does the
> guts of vfs_mountroot(), it accesses non-existant memory when
> ffs_mountroot() calls ffs_mountfs() with rootvp.
> (basically, vinvalbuf() does a VSYNC, but because
> rootvp is not set to anything but NULL, v_op is invalid)
The routine you need to look at is in ffs_mountroot(). A few lines above
the ffs_mountfs() call is a call to bdevvp(rootdev, &rootvp);. That's the
call which will set up rootvp. Make sure it works right, and you'll have a
good vnode. bdevvp() will call into kern/vfs_subr.c and you'll need files
from miscfs/specfs so that spec_vnode_p is set up. Then the v_op table
will be ok.
> I have searched through the kernel source, and these are the
> only three places that seem to set rootvp:
> coda_vfsops.c : coda_mount()
Note that there is a local variable in this routine named rootvp, so it's
not changing the global rootvp. :-)
> vfs_getcwd.c : sys___getcwd()
As best I could tell, this one was just reading rootvp. ??
> kernfs_vfsops.c : kernfs_unmount()
This one too has a local variable for rootvp. I think both it and the coda
code are refering to the root of the file system, not the system's overall
> Assuming that I haven't stuffed up in my searching,
> which of these is called (indirectly) from init_main(), and why ?
You'll need to make sure that your init_main() has the vfs initialization
in it, then all should be well.