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Altera_Forum's avatar
Altera_Forum
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16 years ago

Debug user space application with MMU

I am trying to use the gdbserver as described here:

http://nioswiki.com/linux/debug_user_space

At some point, this was working, but sometimes it wouldn't work and now I haven't had it working for a while. The application and gdb dies on a crash and doesn't let me debug. This isn't just this particular crash, I've had this happen with almost every crash while developing.

On the server:

--- Quote Start ---

root:/> gdbserver localhost:9999 myprogram

Process myprogram created; pid = 50

Listening on port 9999

Remote debugging from host 192.168.100.28

<program output...>

Child terminated with signal = b

Child terminated with signal = 0xb (SIGSEGV)

GDBserver exiting

root:/>

--- Quote End ---

On the client:

--- Quote Start ---

Program terminated with signal SIGSEGV, Segmentation fault.

The program no longer exists.

(gdb) backtrace

No stack.

--- Quote End ---

Any advice?

Also, the wiki says "we will add the gdbserver source to uclinux-dist later" -- is there any progress on this? Could the gdbserver currently in uclinux-dist work?

16 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    In the cases when I could run the program on my PC, I could debug the crash using gdb, so it is something with the NIOS gdbserver provided with the mmu toolchain.

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Just wanted to add that breakpoints don't work either, with the same result, the program just terminates:

    Program terminated with signal SIGTRAP, Trace/breakpoint trap.

    Not having the debugger available is really eating up a lot of time :-(
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Hi,

    --- Quote Start ---

    Just wanted to add that breakpoints don't work either, with the same result, the program just terminates:

    --- Quote End ---

    When the debuggee program crashes, the 'gdbserver' will terminate itself. So please get debuggee's 'coredump' file by setting 'ulimit -c ***', for example in your 'bash', And copy it to your PC, and read it by Nios's 'gdb' with the command 'core-file core'. I think that you can reach the position which causes the crash. Then set a breakpoint there and...

    And don't forget to compile your program with the option switch '-O0'.

    --- Quote Start ---

    Program terminated with signal SIGTRAP, Trace/breakpoint trap.

    --- Quote End ---

    SIGTRAP? Really?

    Kazu
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    I realized when somebody mentioned it in the other thread on this topic (http://www.alteraforum.com/forum/showthread.php?t=19322) that I am not actually quite following the directions there.

    I am not using 

    set solib-absolute-prefix ~/nios2-linux/toolchain-mmu/x86-linux2/nios2-wrs-linux-gnu/libc

    but instead the libs in the romfs: 

    set solib-absolute-prefix /data/nios/nios2-linux/uClinux-dist/romfs/

    Since all the libraries I am using need to be on the device for the application to run, I think this should not make a difference.
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    --- Quote Start ---

    When the debuggee program crashes, the 'gdbserver' will terminate itself. So please get debuggee's 'coredump' file by setting 'ulimit -c ***', for example in your 'bash', And copy it to your PC, and read it by Nios's 'gdb' with the command 'core-file core'. I think that you can reach the position which causes the crash. Then set a breakpoint there and...

    And don't forget to compile your program with the option switch '-O0'.

    --- Quote End ---

    I am trying to use a core file now. I am running `nios2-linux-gnu-gdb mynios2program`, with set solib-absolute-prefix /data/nios/nios2-linux/uClinux-dist/romfs/ in .gdbinit. Then core-file mycorefile, but all I can get is: 

    warning: Couldn't find general-purpose registers in core file.
# 0  0x00000000 in ?? ()
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Hi,

    --- Quote Start ---

    I am trying to use a core file now. I am running `nios2-linux-gnu-gdb mynios2program`, with set solib-absolute-prefix /data/nios/nios2-linux/uClinux-dist/romfs/ in .gdbinit. Then core-file mycorefile, but all I can get is: 

    warning: Couldn't find general-purpose registers in core file.# 0  0x00000000 in ?? ()

    --- Quote End ---

    Do you have enough space for the core dump file? For example,

    ulimit -c unlimiled

    Kazu
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Hi,

    I am debugging a user application and I have some doubts, and maby someone can answer my questions.

    My application produces a segmentation fault, I suppose that a segmentation fault provoke a core dumped, is this true?

    If I want to have core dumps in uClinux, as kazuyasu commented in last posts I have to insert the command : ulimit -c unlimited. But where is it in the configuration kernel?, I haven't found.

    And my last question is, is the core file created in /proc/sys/kernel?, if not where is it found?

    Many thanks
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Hi,

    --- Quote Start ---

    My application produces a segmentation fault, I suppose that a segmentation fault provoke a core dumped, is this true?

    --- Quote End ---

    Yes, but the dumping is limited by 'core file size', and it's 0 by default.

    --- Quote Start ---

    I have to insert the command : ulimit -c unlimited. But where is it in the configuration kernel?, I haven't found.

    --- Quote End ---

    'ulimit -c ***' that I mentioned before is an internal command of 'bash' and you don't need to configure your kernel in general. See also

    http://linux.die.net/man/3/ulimit

    --- Quote Start ---

    And my last question is, is the core file created in /proc/sys/kernel?, if not where is it found?

    --- Quote End ---

    In general, the core dump file is made in your 'current working directory'.

    http://linux.die.net/man/5/core

    Kazu
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Hi Kazu,

    I have changed the shell to ash and now I can see the core file.

    Many thanks