Re: Resolution (Re: [uml-devel] 2.4.22-[67] problems)

[Nuno S. <nun...@vg...>]

Nuno Silva wrote:

[...]

> 
> I've been doing some tests and I'd say that the problem is something 
> regarding the NPTL+TLS+__thread features of recent libc6 (2.3.2 and 
> 2.3.3cvs)... But I'm clueless about the fix :-)
> 
> I'll setup a chroot where I can play around with glibc setups.
> 

OK, just finished the chroot: debian unstable with glibc-2.3.3cvs 
hand-compiled (../libc/configure --with-tls --with-__thread 
--enable-add-ons=nptl --prefix=/ --enable-kernel=2.6.0) and removed the 
debian's libc.

Everything runs OK with the new glibc, tested: bash, apt-get, perl, mc, 
strace, gcc, etc.

However linux (UML's executable) doesn't run:
puma:/uml# ls -la /proc/mm
--w--w--w-    1 root     root            0 Jan  6 08:33 /proc/mm
puma:/uml# uname -a
Linux puma 2.6.0 #2 Mon Jan 5 09:25:45 WET 2004 i686 unknown unknown 
GNU/Linux
puma:/uml# ./linux
Checking for the skas3 patch in the host...found
Checking for /proc/mm...found

[1]+  Stopped                 ./linux
puma:/uml# fg
./linux
Segmentation fault
puma:/uml#


Now with strace:
(see attached file)

Now with gdb:
puma:/uml# gdb ./linux
GNU gdb 6.0-debian
Copyright 2003 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain 
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-linux"...
(gdb) run
Starting program: /uml/linux
Detaching after fork from child process 26378.
Checking for the skas3 patch in the host...found
Checking for /proc/mm...found
Detaching after fork from child process 26379.

Program received signal SIGSTOP, Stopped (signal).
0x400f18dc in clone () from /lib/libc.so.6
(gdb) bt
#0  0x400f18dc in clone () from /lib/libc.so.6
#1  0x4014f000 in ?? ()
#2  0x00000007 in ?? ()
#3  0x00001000 in ?? ()
#4  0xa00a7b7f in start_userspace (cpu=26379) at process.c:113
#5  0xa00a88e2 in start_uml_skas () at process_kern.c:162
#6  0xa00a6bcb in linux_main (argc=0, argv=0xa0000000) at um_arch.c:387
#7  0xa000de0e in main (argc=1, argv=0xbffffa44, envp=0xbffffa4c) at 
arch/um/main.c:146
(gdb) cont
Continuing.

Program received signal SIGSTOP, Stopped (signal).
0x400f18dc in clone () from /lib/libc.so.6
(gdb) bt
#0  0x400f18dc in clone () from /lib/libc.so.6
#1  0x4014f000 in ?? ()
#2  0x00000007 in ?? ()
#3  0x00001000 in ?? ()
#4  0xa00a7b7f in start_userspace (cpu=26379) at process.c:113
#5  0xa00a88e2 in start_uml_skas () at process_kern.c:162
#6  0xa00a6bcb in linux_main (argc=0, argv=0xa0000000) at um_arch.c:387
#7  0xa000de0e in main (argc=1, argv=0xbffffa44, envp=0xbffffa4c) at 
arch/um/main.c:146
(gdb) cont
Continuing.

Program received signal SIGSEGV, Segmentation fault.
0xa001305a in panic (fmt=0xbfffc000 "") at panic.c:67
67      panic.c: No such file or directory.
         in panic.c
(gdb) bt
#0  0xa001305a in panic (fmt=0xbfffc000 "") at panic.c:67
#1  0xa00a7bdd in start_userspace (cpu=-1073758208) at process.c:127
#2  0xa00a88e2 in start_uml_skas () at process_kern.c:162
#3  0xa00a6bcb in linux_main (argc=0, argv=0xa0000000) at um_arch.c:387
#4  0xa000de0e in main (argc=1, argv=0xbffffa44, envp=0xbffffa4c) at 
arch/um/main.c:146
(gdb) cont
Continuing.

Program terminated with signal SIGSEGV, Segmentation fault.
The program no longer exists.
(gdb) quit
puma:/uml#

In my tree, arch/um/kernel/skas/process.c:113 is the pid=clone(..., in

void start_userspace(int cpu)
{
         void *stack;
         unsigned long sp;
         int pid, status, n;

         stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
         if(stack == MAP_FAILED)
                 panic("start_userspace : mmap failed, errno = %d", errno);
         sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);

         pid = clone(userspace_tramp, (void *) sp,
                     CLONE_FILES | CLONE_VM | SIGCHLD, NULL);


I hope this makes sense to someone because I'm off to sleep a few hours :-)

Regards,
Nuno Silva