http://copilotco.com/mail-archives/uml.2008/msg01515.html
On Thu, Aug 6, 2015 at 7:54 PM, Sergei Antonov <sap...@gmail.com> wrote: > Hello! > I'm trying compile and run UML (version 4.1) on x86_64. It builds and > runs fine as a normal program. But when run under gdb, it produces > several segmentation faults. > > This is how I build and run it (based on > http://user-mode-linux.sourceforge.net/hacking.html instructions and > disk image from http://fs.devloop.org.uk/ ): > cd linux && > make mrproper && > make mrproper ARCH=um && > git checkout v4.1 && > make defconfig ARCH=um && > make -j6 ARCH=um && > cd .. && > gdb --args linux/linux ubda=BusyBox-1.13.2-amd64-root_fs mem=256m > > > And this is a complete gdb output: > > =========================================================== > GNU gdb (GDB) 7.9.1 > Copyright (C) 2015 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show copying" > and "show warranty" for details. > This GDB was configured as "x86_64-unknown-linux-gnu". > Type "show configuration" for configuration details. > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>. > Find the GDB manual and other documentation resources online at: > <http://www.gnu.org/software/gdb/documentation/>. > For help, type "help". > Type "apropos word" to search for commands related to "word"... > Reading symbols from linux/linux...done. > (gdb) r > Starting program: /root/exfat/linux/linux > ubda=BusyBox-1.13.2-amd64-root_fs mem=256m > Core dump limits : > soft - 0 > hard - NONE > Core dump limits : > soft - 0 > hard - NONE > Core dump limits : > soft - 0 > hard - NONE > Core dump limits : > soft - 0 > hard - NONE > Checking environment variables for a tempdir...none found > Checking if /dev/shm is on tmpfs...OK > Checking PROT_EXEC mmap in /dev/shm...OK > Core dump limits : > soft - 0 > hard - NONE > Checking environment variables for a tempdir...none found > Checking if /dev/shm is on tmpfs...OK > Checking PROT_EXEC mmap in /dev/shm...OK > Initializing cgroup subsys cpuset > Initializing cgroup subsys cpu > Initializing cgroup subsys cpuacct > Linux version 4.1.0 (root@linux64) (gcc version 4.9.2 (GCC) ) #1 Tue > Aug 4 17:31:01 CEST 2015 > Built 1 zonelists in Zone order, mobility grouping on. Total pages: 64640 > Kernel command line: ubda=BusyBox-1.13.2-amd64-root_fs mem=256m root=98:0 > PID hash table entries: 1024 (order: 1, 8192 bytes) > Dentry cache hash table entries: 32768 (order: 6, 262144 bytes) > Inode-cache hash table entries: 16384 (order: 5, 131072 bytes) > Memory: 253796K/262144K available (2471K kernel code, 624K rwdata, > 780K rodata, 109K init, 161K bss, 8348K reserved, 0K cma-reserved) > NR_IRQS:15 > clocksource itimer: mask: 0xffffffffffffffff max_cycles: 0x1d854df40, > max_idle_ns: 3526361616960 ns > Calibrating delay loop... 2649.29 BogoMIPS (lpj=13246464) > pid_max: default: 32768 minimum: 301 > Mount-cache hash table entries: 512 (order: 0, 4096 bytes) > Mountpoint-cache hash table entries: 512 (order: 0, 4096 bytes) > Initializing cgroup subsys blkio > Initializing cgroup subsys devices > Initializing cgroup subsys freezer > Checking that host ptys support output SIGIO...Yes > Checking that host ptys support SIGIO on close...No, enabling workaround > devtmpfs: initialized > Using 2.6 host AIO > clocksource jiffies: mask: 0xffffffff max_cycles: 0xffffffff, > max_idle_ns: 19112604462750000 ns > NET: Registered protocol family 16 > Switched to clocksource itimer > NET: Registered protocol family 2 > TCP established hash table entries: 2048 (order: 2, 16384 bytes) > TCP bind hash table entries: 2048 (order: 2, 16384 bytes) > TCP: Hash tables configured (established 2048 bind 2048) > UDP hash table entries: 256 (order: 1, 8192 bytes) > UDP-Lite hash table entries: 256 (order: 1, 8192 bytes) > NET: Registered protocol family 1 > console [stderr0] disabled > mconsole (version 2) initialized on /root/.uml/1BxIWh/mconsole > Checking host MADV_REMOVE support...OK > futex hash table entries: 256 (order: 0, 6144 bytes) > VFS: Disk quotas dquot_6.6.0 > VFS: Dquot-cache hash table entries: 512 (order 0, 4096 bytes) > io scheduler noop registered > io scheduler deadline registered (default) > NET: Registered protocol family 17 > Initialized stdio console driver > Console initialized on /dev/tty0 > console [tty0] enabled > Initializing software serial port version 1 > console [mc-1] enabled > > Program received signal SIGSEGV, Segmentation fault. > 0x00007ffff78b16c4 in memset () from /lib64/libc.so.6 > (gdb) bt > #0 0x00007ffff78b16c4 in memset () from /lib64/libc.so.6 > #1 0x00000000601b14f3 in check_partition (hd=<optimized out>, > bdev=<optimized out>) at block/partitions/check.c:165 > #2 0x00000000601b0abb in rescan_partitions (disk=0x70800000, > bdev=0x0) at block/partition-generic.c:433 > #3 0x00000000600e7783 in __blkdev_get (bdev=0x6f802880, > mode=<optimized out>, for_part=0) at fs/block_dev.c:1213 > #4 0x00000000600e7c3b in blkdev_get (bdev=0x0, mode=<optimized out>, > holder=0x0) at fs/block_dev.c:1317 > #5 0x00000000601ae7e3 in register_disk (disk=<optimized out>) at > block/genhd.c:556 > #6 add_disk (disk=0x6fd94000) at block/genhd.c:618 > #7 0x0000000060026270 in ubd_disk_register (major=<optimized out>, > size=<optimized out>, unit=1614123056, disk_out=0x603f6340 > <ubd_gendisk>) at arch/um/drivers/ubd_kern.c:835 > #8 0x0000000060026b1a in ubd_add (n=0, error_out=0x6fc4de90) at > arch/um/drivers/ubd_kern.c:872 > #9 0x0000000060003c23 in ubd_init () at arch/um/drivers/ubd_kern.c:1073 > #10 0x00000000600184c4 in do_one_initcall (fn=0x60003b5a <ubd_init>) > at init/main.c:788 > #11 0x0000000060001e38 in do_initcall_level (level=<optimized out>) at > init/main.c:853 > #12 do_initcalls () at init/main.c:861 > #13 do_basic_setup () at init/main.c:880 > #14 kernel_init_freeable () at init/main.c:1001 > #15 0x000000006027ce2f in kernel_init (unused=<optimized out>) at > init/main.c:931 > #16 0x0000000060019a7f in new_thread_handler () at > arch/um/kernel/process.c:129 > #17 0x0000000000000000 in ?? () > (gdb) c > Continuing. > > Program received signal SIGSEGV, Segmentation fault. > n_tty_open (tty=0x6fcb5c00) at drivers/tty/n_tty.c:1929 > 1929 ldata->overrun_time = jiffies; > (gdb) bt > #0 n_tty_open (tty=0x6fcb5c00) at drivers/tty/n_tty.c:1929 > #1 0x00000000601d1f49 in tty_ldisc_open (tty=0x70804288, > ld=<optimized out>) at drivers/tty/tty_ldisc.c:450 > #2 0x00000000601d289a in tty_ldisc_setup (tty=0x6fcb5c00, o_tty=0x0) > at drivers/tty/tty_ldisc.c:735 > #3 0x00000000601cc503 in tty_init_dev (driver=0x6fdb3d00, idx=0) at > drivers/tty/tty_io.c:1548 > #4 0x00000000601cc906 in tty_open (inode=0x6f8001e0, filp=0x6fd2d900) > at drivers/tty/tty_io.c:2091 > #5 0x00000000600bce52 in chrdev_open (inode=0x6f8001e0, > filp=0x6fd2d900) at fs/char_dev.c:388 > #6 0x00000000600b74c2 in do_dentry_open (f=0x6fd2d900, > open=0x600bcd15 <chrdev_open>, cred=<optimized out>) at fs/open.c:734 > #7 0x00000000600b7690 in vfs_open (path=<optimized out>, > filp=<optimized out>, cred=<optimized out>) at fs/open.c:871 > #8 0x00000000600c42ad in do_last (nd=0x6fc4de10, path=0x6fc4ddb0, > file=0x6fd2d900, op=<optimized out>, opened=<optimized out>, > name=<optimized out>) at fs/namei.c:3104 > #9 0x00000000600c62ca in path_openat (dfd=<optimized out>, > pathname=<optimized out>, nd=0x6fc4de10, op=0x6fc4df0c, > flags=<optimized out>) at fs/namei.c:3243 > #10 0x00000000600c7443 in do_filp_open (dfd=-100, pathname=0x6fe37000, > op=0x6fc4df0c) at fs/namei.c:3290 > #11 0x00000000600b860e in do_sys_open (dfd=-100, filename=<optimized > out>, flags=<optimized out>, mode=<optimized out>) at fs/open.c:1014 > #12 0x00000000600b86e0 in SYSC_open (mode=<optimized out>, > flags=<optimized out>, filename=<optimized out>) at fs/open.c:1032 > #13 SyS_open (filename=<optimized out>, flags=<optimized out>, > mode=<optimized out>) at fs/open.c:1027 > #14 0x0000000060001e6b in kernel_init_freeable () at init/main.c:1004 > #15 0x000000006027ce2f in kernel_init (unused=<optimized out>) at > init/main.c:931 > #16 0x0000000060019a7f in new_thread_handler () at > arch/um/kernel/process.c:129 > #17 0x0000000000000000 in ?? () > (gdb) c > Continuing. > EXT4-fs (ubda): mounting ext3 file system using the ext4 subsystem > EXT4-fs (ubda): mounted filesystem with ordered data mode. Opts: (null) > VFS: Mounted root (ext3 filesystem) readonly on device 98:0. > devtmpfs: mounted > > Program received signal SIGSEGV, Segmentation fault. > n_tty_open (tty=0x6fd16800) at drivers/tty/n_tty.c:1929 > 1929 ldata->overrun_time = jiffies; > (gdb) > Continuing. > Virtual console 5 assigned device '/dev/pts/1' > > Program received signal SIGSEGV, Segmentation fault. > n_tty_open (tty=0x6fd16000) at drivers/tty/n_tty.c:1929 > 1929 ldata->overrun_time = jiffies; > (gdb) > Continuing. > Serial line 0 assigned device '/dev/pts/2' > > Please press Enter to activate this console. > =========================================================== > > > The first fault happens in check_partition(), then several more happen > in some tty code. I investigated the first fault a little and found > this. > > 1. The memset is called by this line: > memset(state->parts, 0, state->limit * sizeof(state->parts[0])); > > 2. I printk-ed its parameters: > printk(" %s %p %lu\n", __func__, state->parts, state->limit * > sizeof(state->parts[0])); > they look normal: > check_partition 0000000070800000 2048 > > 3. Even a 1-byte memset produces segfault too: > memset(state->parts, 0, 1); > > 4. The memory is allocated by vzalloc() in allocate_partitions(). > > 5. Writing 1 byte with vwrite() does not fault and returns 0. > vwrite(state->parts, &some_variable, 1); > > > I tried changing a kernel version (4.0) and a version of gdb (7.7.1) - > it was all the same. > > How do I fix this problem and debug UML without getting scary and > disturbing faults? > > ------------------------------------------------------------------------------ > _______________________________________________ > User-mode-linux-user mailing list > User-mode-linux-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user ------------------------------------------------------------------------------ _______________________________________________ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
