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Problem Report 1178 Details

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    Problem Report Number 1178
    Submitter's Classification Test Suite problem
    State Resolved
    Resolution Rejected (REJ)
    Problem Resolution ID REJ.X.0380
    Raised 1970-01-01 08:00
    Updated 2003-03-13 08:00
    Published null
    Product Standard Internationalised System Calls and Libraries Extended (UNIX 95)
    Certification Program The Open Brand certification program
    Test Suite VSU version 4.1.11
    Test Identification base/mmap 9 12 21
    Problem Summary PG4U.00087 This IR claims that mmap() should fail when mapping a region larger than the current size of the file.
    Problem Text
    In the above test cases, a temporary file is created which is used
    for mapping. The size of the file created is 8192 bytes, and mmap()
    is invoked as follows:
    if ((ask_addr = (int *)mmap((void *)0, (size_t)(3*pgsz),
    PROT_NONE, MAP_SHARED, fd1, 0)) == (int *)-1)
    {
    fwerrno("mmap");
    return;
    }

    The size of the process area to be mapped, which is (3*pgsz)
    where pgsz is 4096, is 12288. This is greater than the file
    size and so mmap() fails with errno set to ENXIO. This
    behaviour of mmap() is in line with the XPG4.2 specification,
    which states:

    mmap() function will fail if:

    [ENXIO] Addresses in the range [off, off + len)
    are invalid for the file descriptor.

    To ensure passing of mmap() in the above test purposes, size of the file
    created must be 12288 bytes.
    Test Output
    TEST CASE: mmap

    TEST PURPOSE #9
    A call to void *mmap(void *addr, size_t len, int prot,
    int flags, int fildes, off_t off) when fildes is
    associated with a regular file and the MAP_FIXED flag
    is set in flags shall cause the file associated with
    fildes to be mapped at an address exactly matching
    addr.
    PREP: Obtain the system page size by call to
    sysconf(_SC_PAGESIZE)
    pgsz = 4096
    PREP: Establish signal handlers for SIGSEGV and SIGBUS
    PREP: Open a file and initialize it
    PREP: Allocate memory for buffer
    PREP: Now set proper permissions and re-open file
    PREP: Find a fixed address for mapping text
    ERROR: mmap failed, errno = 6(ENXIO - No such device or address)
    9 FAIL

    TEST PURPOSE #12
    References to mapped pages beyond the page containing
    the last byte of a file mapped by a call to void
    *mmap(void *addr, size_t len, int prot, int flags, int
    fildes, off_t off) shall result in the delivery of a
    SIGBUS or a SIGSEGV signal.
    PREP: Obtain the system page size by call to
    sysconf(_SC_PAGESIZE)
    pgsz = 4096
    PREP: Establish signal handlers for SIGSEGV and SIGBUS
    PREP: Allocate memory for buffer
    PREP: Open a file and initialize it
    TEST: mmap() with MAP_SHARED returns location where
    file is mapped
    ERROR: mmap failed, errno = 6(ENXIO - No such device or address)
    12 FAIL

    TEST PURPOSE #21
    EINVAL in errno and return -1 on a call to void
    *mmap(void *addr, size_t len, int prot, int flags, int
    fildes, off_t off) when addr is not a multiple of the
    page size returned by sysconf(_SC_PAGESIZE) and
    MAP_FIXED is specified.
    PREP: Obtain the system page size by call to
    sysconf(_SC_PAGESIZE)
    pgsz = 4096
    PREP: Establish signal handlers for SIGSEGV and SIGBUS
    PREP: Open a file and initialize it
    PREP: Allocate memory for buffer
    PREP: Now set proper permissions and re-open file
    PREP: Find a fixed address not aligned to page boundary
    ERROR: mmap failed, errno = 6(ENXIO - No such device or address)
    21 FAIL

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    We recommend this request be refused.

    We believe the test is correct.

    The length specified is valid for the possible address space of the
    file. The standard states for the mmap() function,

    The address ranges covered by [pa, pa + len) and [off, off +
    len) must be legitimate for the possible (not necessarily
    current) address space of a process and the file,
    respectively.

    As a result, it allows pages to be mapped that are beyond the current
    end of the file and ENXIO should not be returned. The key phrase here
    is, "not necessarily current."

    The standard provides the user with errors and signals to detect when
    references to invalid portions of the file are made, but otherwise,
    the user is free to mmap() currently non-existent portions of a file
    that may be become valid prior to the user referencing those currently
    non-existent portions of the file.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Rejected (REJ)
    Review Conclusion
    This request is refused.

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