Re: [uml-devel] Problems with UML on Debian Sarge 64 host

[Ian McDonald <imcdnzl@gmail.com>]

> Comments inline
> >
> > On 15/04/05, Blaisorblade <blaisorblade@yahoo.it> wrote:
> > > On Thursday 14 April 2005 06:25, Ian McDonald wrote:
> > > > Hi there,
> 
> > > > The problem is that my bootup dies very early on and this is the total
> > > > output: Checking for /proc/mm...not found
> > > > Checking PROT_EXEC mmap in /tmp...OK
> > > > tracing thread pid = 20981
> > > > OP_FORK failed to attach pid
> 
> > > > I suspect that this is something to do with my mixed 32/64 bit
> > > > environment but I am not sure... Can anybody shed some light on this?
> > >
> > > I've seen that *sometimes* too on 64-bit envs., tried doing a "setarch
> > > i386 linux" or something like that, to force a 32-bit emulation?
> 
> > setarch isn't on this machine and I can't find the equivalent command for
> > sarge.
> Tried installing the needed package? On SUSE it's called "linux32".

The debian implementation has a 32 bit user space but it is picking up
64 bit for UML but just override with SUBARCH=i386.

I don't have root access to this box.

Interestingly enough it has now started working apart from some COW
backing store issues which I have to get the system administrator to
fix. I changed nothing but notice that the host kernel has changed
from 2.6.8 to 2.6.11.7 so something in host kernel may well have fixed
my issue! (which I have no control over).

> 
> Also, tried compiling UML itself on a real 32-bit box (with static linking,
> obviously)?
> 
Yes - work.

> > > Tried disabling the ptrace proxy in compilation, as the first thing?
> 
> > Tried that and no difference. Note that 2.6.11.x with bs4 doesn't
> > compile with this option showing unless you set FRAME_POINTER to n.
> > You get an error such as:
> 
> > kernel/built-in.o(.text+0x83f4): In function `profile_tick':
> > kernel/profile.c:387: undefined reference to `profile_pc'
> Hmm, interesting... However, the more likely culprit is CONFIG_SMP:

Tried it with CONFIG_SMP off and it resolved the issue.
> 
> include/asm-i386/ptrace.h
> 
> #if defined(CONFIG_SMP) && defined(CONFIG_FRAME_POINTER)
> extern unsigned long profile_pc(struct pt_regs *regs);
> #else
> #define profile_pc(regs) instruction_pointer(regs)
> #endif
> instruction_pointer is defined, profile_pc is not.
> 
> > The only way I could find to set this option to n was hacking the
> > autoconf.h file...
> Disable CONFIG_DEBUG_INFO and FRAME_POINTER should become 'n'.
> 
> > So still no 32 bit UML... will try 64 bit (once I get access to the 64
> > bit compiler) and see if I can get that to work....
> Let me recall: you *did* succeed on your older fully-32bit Debian Woody
> system, right? Or did I leave something unfixed behind?

Yes I did succeed on my 32 bit Woody but that machine is being turned
off in next couple of weeks :-(

The UML appears now to be working (once I can do more tests) on 64 bit
once host kernel was upgraded to 2.6.11.7 (guess is 2.6.11.4+bs4 32
bit).

Thanks for your help. Unfortunately I don't have much time to help
write patches at present or too many tests as my UML testing has
slowed down my project and I have acquired two dedicated machines to
help me out... I will certainly try to help though whenever I get
bored (which is quite often!)

Regards,

Ian


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