Re: [uml-devel] UML running on host-kernel 2.6.0 with NPTL-enabled glibc problem

[Nuno Silva <nuno.silva@vgertech.com>]

Oleg Drokin wrote:
> Hello!
> 
> Nuno Silva <nuno.silva@vgertech.com> wrote:
> 
> NS> I've been trying for days and made lots of tests and it seems that the
> NS> 2.4 UML binary can't run on a host with 2.6 kernel and nptl-enabled glibc.
> 
> Hm. I guess you are running some sort of old uml code.
> The fix was oneliner and included long ago. See the patch below.
> Apply it and then recompile.
> 
> I use 2.6.1 + glibc 2.3.2-101 from Fedora Core 1,
> I hope this is new enough? ;)

Thanks, but this patch is in my tree (2.4.23-um1). And, as BlaisorBlade 
mentions in the next message, I'm trying to build a dynamic UML -- This 
is mainly to try to take advantage of sysenter/sysexit. Sysenter could 
speedup UML a bit :)

Also, the version of glibc itself says nothing about this subject. You 
must make sure that you're using a nptl-tls-enabled one. These optimized 
libraries are usually in /lib/tls/i686/cmov/* or something similar. One 
nice way to verify is ldd:

ldd on my debian sid instalation:
# ldd ./linux
         libutil.so.1 => /lib/tls/i686/cmov/libutil.so.1 (0x40018000)
         libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0x4001b000)
         /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
#

ldd in my chroot (only) with optimized glibc:
# ldd ./linux
         linux-gate.so.1 =>  (0xffffe000)
         libutil.so.1 => /lib/libutil.so.1 (0x40019000)
         libc.so.6 => /lib/libc.so.6 (0x4001c000)
         /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
#

That "linux-gate" thing is the system call multiplexer that enables 
sysenter.

DISCLAIMER: I'm no expert in this linker/sysenter/glibc magic so I might 
be wrong. The fact is that ./linux doesn't run when ldd reports 
"linux-gate" in it's output.

I'll try BlaisorBlade's /arch/um/dyn.lds.S patch next.

Thanks,
Nuno Silva


> 
> Bye,
>     Oleg
> 
> --- linux-2.4.20.orig/arch/um/link.ld.in	2003-10-25 00:35:59.000000000 +0400
> +++ linux-2.4.20/arch/um/link.ld.in	2003-10-25 00:36:02.000000000 +0400
> @@ -6,7 +6,6 @@
>  {
>    . = START() + SIZEOF_HEADERS;
>  
> -  . = ALIGN(4096);
>    __binary_start = .;
>  ifdef(`MODE_TT', `
>    .thread_private : {
> 



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