lkml.org 
[lkml]   [2005]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    Subjectkernel generating SIGBUS while handling pagefault.
    Hello,

    I have a program which is trying to access its virtual memory segments
    (listed in /proc/<pid>/maps file). But while reading the following
    virtual memory segment as below.
    <-------------------------------------------------------------------------------------------------------------------->
    0x2a95556000 0x2a9566b000 0x115000 0
    /lib64/ld-2.3.2.so
    0x2a9566b000 0x2a9566c000 0x1000 0x15000
    /lib64/ld-2.3.2.so
    <-------------------------------------------------------------------------------------------------------------------->
    generate SIGBUS with siginfo as BUS_ADRERR (Non-existent physical
    address), I traced back into the kernel code to get the detail on why
    this BUS_ADRERR is set and found that, if the kernel could not handle
    pagefault it generates BUS_ADRERR.

    In the file /usr/src/linux-2.4.21-20.EL/mm/memory.c at line 1746.
    <------------------------------------------------------------------->
    new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, 0);

    if (new_page == NULL) /* no page was available -- SIGBUS */
    return 0;
    if (new_page == NOPAGE_OOM)
    return -1;
    <------------------------------------------------------------------->
    So is the kernel trying to get a page (map a page) into the swap space
    from file, and failing to map the file ? due to lack of swap space??.
    Currently the kernel runs on a amd64 machine with 5GB RAM and 33GB
    swap space.

    But if I run the same program(executable) on amd64 machine with kernel
    2.4.21-4 with 8GB RAM and 16GB swap space, there were no page faults
    and I see only 1 virtual address mapping for /lib64/ld-2.3.2.so on
    this machine.

    I analyzed the strace on the machine failing with SIGBUS and found the
    following in the strace output
    <-------------------------------------------------------------------->
    mmap(NULL, 1061968, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) =
    0x2a95687000 mprotect(0x2a9568b000, 1045584, PROT_NONE) = 0
    mmap(0x2a95787000, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED,
    3, 0) = 0x2a95787000
    close(3) = 0
    mprotect(0x7fbff09000, 4096,
    PROT_READ|PROT_WRITE|PROT_EXEC|PROT_GROWSDOWN) = -1 EINVAL (Invalid
    argument) mprotect(0x7fbff02000, 32768,
    PROT_READ|PROT_WRITE|PROT_EXEC) = -1 ENOMEM (Cannot allocate memory)
    mprotect(0x7fbff06000, 16384, PROT_READ|PROT_WRITE|PROT_EXEC) = -1
    ENOMEM (Cannot allocate memory) mprotect(0x7fbff08000, 8192,
    PROT_READ|PROT_WRITE|PROT_EXEC) = 0 mprotect(0x7fbff06000, 8192,
    PROT_READ|PROT_WRITE|PROT_EXEC) = -1 ENOMEM (Cannot allocate memory)
    mprotect(0x7fbff07000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC) = -1
    ENOMEM (Cannot allocate memory)
    <-------------------------------------------------------------------->
    I see some system calls failing with 'Cannot allocate memory', is this
    because that I use only 5GB of RAM for a 64-bit machine?

    Can some mm hackers kindly give some inputs in this?

    Thanks in advance.

    Best,
    Vamsi kundeti.
    India.
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-05-31 20:50    [W:0.023 / U:5.728 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site