On Thursday 18 January 2007 00:26, Jeff Dike wrote: > On Wed, Jan 17, 2007 at 05:15:35PM +0100, Blaisorblade wrote: > > kjournald starting. Commit interval 5 seconds > > EXT3-fs: mounted filesystem with ordered data mode. > > VFS: Mounted root (ext3 filesystem) readonly. > > > > it hangs giving the following result at strace -p (I've printed two > > consecutive iterations of the same messages to show that they are the > > same): > > I'm chasing something on i386 with the same symptoms, but I think it's > a different problem. What I'm seeing is init segfaulting on some > hosts, but not others. > > Figure out what the segfault is, and where it's happening. I've started an attempt. I'm also compiling uml 2.6.16-bs3 - with gcc 3.4 there is no problem, we'll see now with gcc 4.0. All these tests are run on a custom 2.6.18.6 64-bit kernel, without SKAS (and with my RFP patches , but this won't make a difference).
Ok, I hope I remembered correctly how to debug such faults (I'm posting the full procedure so you can give a look) (gdb) where #0 userspace (regs=0x60a5cac8) at /home/paolo/Admin/kernel/6/VCS/linux-2.6.18/arch/um/os-Linux/skas/process.c:275 #1 0x0000000060010192 in new_thread_handler (sig=<value optimized out>) at /home/paolo/Admin/kernel/6/VCS/linux-2.6.18/arch/um/kernel/skas/process_kern.c:68 #2 <signal handler called> #3 0x000000006017a829 in kill () at swab.h:135 #4 0x000000006001d7c9 in set_signals (enable=12139) at /home/paolo/Admin/kernel/6/VCS/linux-2.6.18/arch/um/os-Linux/signal.c:228 #5 0x00000000602a3330 in init_thread_union () #6 0x00000000602a34e0 in init_thread_union () #7 0x00000000600204a4 in new_thread (stack=Cannot access memory at address 0xfffffffffffffe38 ) at /home/paolo/Admin/kernel/6/VCS/linux-2.6.18/arch/um/os-Linux/skas/process.c:457 Previous frame inner to this frame (corrupt stack?) (gdb) print/x regs->skas.regs[16] # HOST_IP $22 = 0x4042f92f # Always this one (gdb) print pid $25 = 12191 bash $ grep 4042f000 /proc/12191/maps 4042f000-40430000 r-xs 019a5000 00:13 72548 /tmp/vm_file-eTomUL (deleted) Finally: (gdb) print/x uml_physmem + 0x019a5000 + 0x92f $24 = 0x619a592f (that's uml_physmem, plus mmap offset from /proc/<child>/maps, + the offset inside the vma). With disassemble I got: 0x00000000619a590f: nop 0x00000000619a5910: mov $0x15,%rax # 21 = __NR_access on x86_64. 0x00000000619a5917: syscall 0x00000000619a5919: cmp $0xfffffffffffff001,%rax # that's -4095, -MAX_ERRNO 0x00000000619a591f: jae 0x619a5922 0x00000000619a5921: retq 0x00000000619a5922: mov 1549599(%rip),%rcx # 0x61b1fe48 0x00000000619a5929: xor %rdx,%rdx 0x00000000619a592c: sub %rax,%rdx 0x00000000619a592f: mov %edx,%fs:(%rcx) #faulting instruction. 0x00000000619a5932: or $0xffffffffffffffff,%rax 0x00000000619a5936: jmp 0x619a5921 And there is also a caller: 0x00000000619a5940: push %rbx 0x00000000619a5941: mov %esi,%ebx 0x00000000619a5943: sub $0x90,%rsp 0x00000000619a594a: mov 1549783(%rip),%rax # 0x61b1ff28 0x00000000619a5951: mov (%rax),%edx 0x00000000619a5953: test %edx,%edx 0x00000000619a5955: jne 0x619a5969 0x00000000619a5957: callq 0x619a5910 0x00000000619a595c: mov %eax,%edx 0x00000000619a595e: add $0x90,%rsp 0x00000000619a5965: mov %edx,%eax 0x00000000619a5967: pop %rbx This looks like part of the code emitted for __syscall_return, with %fs:$rcx seeming like a move into errno (i.e. that's actually glibc code). This is from a Sarge-64 root_fs (the one from Antoine Martin). RCX there is (long)regs->skas.regs[11] = -64, and for FS, since HOST_FS = 25, I get: print/x regs->skas.regs[25] $45 = 0x63 -- Inform me of my mistakes, so I can add them to my list! Paolo Giarrusso, aka Blaisorblade http://www.user-mode-linux.org/~blaisorblade Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
