[uml-devel] Building a UML uClinux(Busybox/uClibc) filesystem

[uml-devel] Building a UML uClinux(Busybox/uClibc) filesystem

[Andrew Sinclair]

Hello all,

I've been able to use the pre-built Busybox 1.5.0 filesystem at
http://uml.nagafix.co.uk/ perfectly with the same UML kernel I am using.


Unfortunately, when trying to generate my own filesystem, my kernel no
longer works. It basically stops after mounting the filesystem. 

When I try and use gdb to debug I get stuck in
arch/um/include/um_uaccess.h:50

static inline int copy_to_user(void __user *to, const void *from, int n)
{
        return(CHOOSE_MODE_PROC(copy_to_user_tt, copy_to_user_skas, to, 
                                from, n));
}

If I put the kernel in tracing thread mode, to avoid this, it falls over
even with the prebuilt nagafix filesystem.

I have been unable to build the automated Busybox root filesystem
builder (based on buildroot) on
http://user-mode-linux.sourceforge.net/contrib.html
A number of the package download links in the makefile no longer exist,
so I searched the web for the packages from other locations. Perhaps I
have the wrong packages. I have got it to the point where it is looking
for a uml-gcc that is not in the build folder.

I've noticed that the nagafix prebuilt filesystem has no lib folder. I
guess this means that the pre-built filesystem was built with glibc?
(Unlike the mine or the buildroot variant which use uClibc)

Can anyone guide me as to how I can debug this from here? 


$ ./images/linux umid=unit_1 ubd0=./images/root_fs  init=/bin/sh
Checking that ptrace can change system call numbers...OK
Checking syscall emulation patch for ptrace...OK
Checking advanced syscall emulation patch for ptrace...OK
Checking for tmpfs mount on /dev/shm...OK
Checking PROT_EXEC mmap in /dev/shm/...OK
Checking for the skas3 patch in the host:
  - /proc/mm...not found
  - PTRACE_FAULTINFO...not found
  - PTRACE_LDT...not found
UML running in SKAS0 mode
Checking that ptrace can change system call numbers...OK
Checking syscall emulation patch for ptrace...OK
Checking advanced syscall emulation patch for ptrace...OK
[42949372.960000] Linux version 2.6.17-uc1-adi3
(andrew.sinclair@LinuxMachine.elpro) (gcc version 4.1.1 20070105 (Red
Hat 4.1.1-51)) #19 Thu Jun 7 12:03:20 EST 2007
[42949372.960000] Built 1 zonelists
[42949372.960000] Kernel command line: ubd0=./images/root_fs
init=/bin/sh root=98:0
[42949372.960000] PID hash table entries: 256 (order: 8, 1024 bytes)
[42949372.960000] Dentry cache hash table entries: 4096 (order: 2, 16384
bytes)
[42949372.960000] Inode-cache hash table entries: 2048 (order: 1, 8192
bytes)
[42949372.960000] Memory: 29108k available
[42949373.220000] Mount-cache hash table entries: 512
[42949373.220000] Checking for host processor cmov support...Yes
[42949373.220000] Checking for host processor xmm support...No
[42949373.220000] Checking that host ptys support output SIGIO...Yes
[42949373.220000] Checking that host ptys support SIGIO on close...No,
enabling workaround
[42949373.220000] Using 2.6 host AIO
[42949373.220000] NET: Registered protocol family 16
[42949373.220000] NET: Registered protocol family 2
[42949373.300000] IP route cache hash table entries: 1024 (order: 0,
4096 bytes)
[42949373.300000] TCP established hash table entries: 1024 (order: 0,
4096 bytes)
[42949373.300000] TCP bind hash table entries: 1024 (order: 0, 4096
bytes)
[42949373.300000] TCP: Hash tables configured (established 1024 bind
1024)
[42949373.300000] TCP reno registered
[42949373.300000] Checking host MADV_REMOVE support...OK
[42949373.300000] mconsole (version 2) initialized on
/home/andrew.sinclair/.uml/unit_1/mconsole
[42949373.300000] Host TLS support detected
[42949373.300000] Detected host type: i386
[42949373.300000] io scheduler noop registered (default)
[42949373.300000] RAMDISK driver initialized: 16 RAM disks of 4096K size
1024 blocksize
[42949373.300000] loop: loaded (max 8 devices)
[42949373.300000] TCP bic registered
[42949373.300000] 802.1Q VLAN Support v1.8 Ben Greear
<greearb@candelatech.com>
[42949373.300000] All bugs added by David S. Miller <davem@redhat.com>
[42949373.300000] Initialized stdio console driver
[42949373.300000] Console initialized on /dev/tty0
[42949373.300000] Initializing software serial port version 1
[42949373.300000]  ubda: unknown partition table
[42949373.300000] VFS: Mounted root (ext2 filesystem) readonly.



Kind Regards,

Andrew Sinclair

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Re: [uml-devel] Building a UML uClinux(Busybox/uClibc) filesystem

[Antoine Martin]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

Andrew Sinclair wrote:
> Hello all,
> 
> I've been able to use the pre-built Busybox 1.5.0 filesystem at
> http://uml.nagafix.co.uk/ perfectly with the same UML kernel I am using.
> 
> 
> Unfortunately, when trying to generate my own filesystem, my kernel no
> longer works. It basically stops after mounting the filesystem. 
You may want to diff the config I used with yours:
http://uml.nagafix.co.uk/BusyBox-1.5.0/amd64.config
And see if anything major turns up.

> When I try and use gdb to debug I get stuck in
> arch/um/include/um_uaccess.h:50
> 
> static inline int copy_to_user(void __user *to, const void *from, int n)
> {
>         return(CHOOSE_MODE_PROC(copy_to_user_tt, copy_to_user_skas, to, 
>                                 from, n));
> }
> 
> If I put the kernel in tracing thread mode, to avoid this, it falls over
> even with the prebuilt nagafix filesystem.
> 
> I have been unable to build the automated Busybox root filesystem
> builder (based on buildroot) on
> http://user-mode-linux.sourceforge.net/contrib.html
> A number of the package download links in the makefile no longer exist,
> so I searched the web for the packages from other locations. Perhaps I
> have the wrong packages. I have got it to the point where it is looking
> for a uml-gcc that is not in the build folder.
> 
> I've noticed that the nagafix prebuilt filesystem has no lib folder. I
> guess this means that the pre-built filesystem was built with glibc?
> (Unlike the mine or the buildroot variant which use uClibc)
IIRC, that's because it was built with the static option.

Antoine
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Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

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=ODDY
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[uml-devel] Problems with dynamic linking applications for UML

[Andrew Sinclair]

Hello everyone,

I am using uClinux. When I statically link the user applications for
UML, everything works fine. I find that if I dynamically link user
applications, my UML halts after mounting the filesystem. 

If I statically link Busybox only, and dynamically the remaining user
applications I receive a "Floating point exception" when I try to run
them from a Busybox shell. 

Dynamic linking application source works ok for our target ARM based
hardware, just not UML. I must be missing a key setting when I build for
UML. Can anyone help?

Kind Regards,

Andrew Sinclair






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Re: [uml-devel] Problems with dynamic linking applications for UML

[Jeff Dike]

On Mon, Jul 02, 2007 at 09:38:58AM +1000, Andrew Sinclair wrote:
> If I statically link Busybox only, and dynamically the remaining user
> applications I receive a "Floating point exception" when I try to run
> them from a Busybox shell. 

Can you send me a copy of the affected filesystem?

				Jeff

-- 
Work email - jdike at linux dot intel dot com

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Re: [uml-devel] Building a UML uClinux(Busybox/uClibc) filesystem

[Jeff Dike]

On Thu, Jun 07, 2007 at 05:57:19PM +1000, Andrew Sinclair wrote:
> Unfortunately, when trying to generate my own filesystem, my kernel no
> longer works. It basically stops after mounting the filesystem. 
> 
> When I try and use gdb to debug I get stuck in
> arch/um/include/um_uaccess.h:50
> 
> static inline int copy_to_user(void __user *to, const void *from, int n)
> {
>         return(CHOOSE_MODE_PROC(copy_to_user_tt, copy_to_user_skas, to, 
>                                 from, n));
> }

I'm guessing gdb is stopping because it sees a segfault there:

(gdb) handle SIGSEGV pass nostop noprint

Segfaults within UML are normal, and gdb should just ignore them.

				Jeff

-- 
Work email - jdike at linux dot intel dot com

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