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    SubjectRe: asm-generic/unistd.h and glibc use of NR_ipc
     (Adding libc-ports to the cc list.)

    On 9/28/2010 4:40 AM, Arnd Bergmann wrote:
    > Chris Metcalf is using the generic unistd.h file on the tile architecture
    > and has a glibc port that should be easily portable to all future
    > architectures. There are a few of them getting ready to be merged
    > now (c6x, lm32, nios2, and some people have contacted me privately
    > for architectures I cannot name).
    >
    > I expect that all of them will just use the same syscall ABI and glibc
    > port.

    I'm happy to provide some previews of the work I'm doing to interested parties.

    One question for the libc folks is nomenclature. For now I'm using
    "sysdeps/unix/sysv/linux/generic" to hold the sources that are meant to be
    used for any architecture that uses Arnd's <asm-generic/unistd.h> along
    with the other asm-generic headers, e.g. <asm-generic/stat.h>. I've
    appended a list of the files that I've put in that directory to this
    email. Many of them are there just for handling missing "standard"
    syscalls in <asm-generic/unistd.h>; for example the "readlink" syscall
    becomes "readlinkat" in dl-origin.c, etc.

    Is this the best name to use for the directory, though? In particular,
    glibc already uses "sysdeps/generic" in a slightly special sense to provide
    the fallback if no sysdeps override is available for a given file. But the
    Linux naming of "generic unistd.h" is pretty commonplace, so I assume that
    in the "linux/" hierarchy it is reasonably clear what that subdirectory means.

    In practice, of course, there's still lots of architecture-specific code
    that is needed above and beyond the generic Linux subdirectory. Our 32-bit
    platform ("tile/tilepro") has an "Implies" file with
    unix/sysv/linux/generic and unix/sysv/linux/generic/wordsize-32; our 64-bit
    platform ("tile/tilegx") has an "Implies" file with unix/sysv/linux/generic
    and unix/sysv/linux/wordsize-64. Beyond that we have another 30-odd files
    in sysdeps/unix/sysv/linux/tile to implement the non-NPTL part of our glibc
    support, plus 50-odd files in sysdeps/tile.

    I haven't provided an "nptl/sysdeps/unix/sysv/linux/generic/" directory
    since there wasn't anything obviously generic about the "tile" support I
    added for NPTL.

    Another point where I'd appreciate guidance from libc-alpha is the sysctl()
    and ustat() APIs. The corresponding system calls are missing from
    <asm-generic/unistd.h>, since they are deprecated and their functionality
    is better provided by other means (/proc/sys, fstat). So I've simply had
    them return -1 with errno == ENOSYS. Is there any reason to think they
    merit more substantial work? One could imagine baking in some horrible
    mapping of "integer names" into path components for a sysctl()
    implementation and reading /proc/sys to provide results, or walking all of
    the mount points looking for a matching device number to pass a name to
    fstat(), but I'm not sure it's worth the bloat to the library.

    I have a few patches for the platform-independent glibc code, mostly for
    things which are exposed in our platform but not in others. E.g.
    __readlink() in include/unistd.h returns the wrong type (int not ssize_t),
    and some of the standard Linux implementations of things like fxstat64.c
    need to be completely wrapped with "#ifndef XSTAT_IS_XSTAT64" so that
    fxstat.c can provide the alias, since all the stat structures are the same
    everywhere. I will submit some separate patches to libc-alpha for this.

    Thanks in advance for any feedback. Please keep me cc'ed on any
    discussions of the generic Linux syscall ABI. Thanks!

    sysdeps/unix/sysv/linux/generic/access.c
    sysdeps/unix/sysv/linux/generic/bits/fcntl.h
    sysdeps/unix/sysv/linux/generic/bits/sem.h
    sysdeps/unix/sysv/linux/generic/bits/stat.h
    sysdeps/unix/sysv/linux/generic/bits/typesizes.h
    sysdeps/unix/sysv/linux/generic/chmod.c
    sysdeps/unix/sysv/linux/generic/chown.c
    sysdeps/unix/sysv/linux/generic/lxstat.c
    sysdeps/unix/sysv/linux/generic/xstat.c
    sysdeps/unix/sysv/linux/generic/Versions
    sysdeps/unix/sysv/linux/generic/fxstatat.c
    sysdeps/unix/sysv/linux/generic/lchown.c
    sysdeps/unix/sysv/linux/generic/link.c
    sysdeps/unix/sysv/linux/generic/readlink.c
    sysdeps/unix/sysv/linux/generic/open.c
    sysdeps/unix/sysv/linux/generic/open64.c
    sysdeps/unix/sysv/linux/generic/pipe.c
    sysdeps/unix/sysv/linux/generic/poll.c
    sysdeps/unix/sysv/linux/generic/recv.c
    sysdeps/unix/sysv/linux/generic/rmdir.c
    sysdeps/unix/sysv/linux/generic/send.c
    sysdeps/unix/sysv/linux/generic/symlink.c
    sysdeps/unix/sysv/linux/generic/syscalls.list
    sysdeps/unix/sysv/linux/generic/sysdep.h
    sysdeps/unix/sysv/linux/generic/unlink.c
    sysdeps/unix/sysv/linux/generic/xmknod.c
    sysdeps/unix/sysv/linux/generic/sysctl.c
    sysdeps/unix/sysv/linux/generic/readlink_chk.c
    sysdeps/unix/sysv/linux/generic/ustat.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/fcntl.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/fstatfs.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/ftruncate.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/fxstat.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/llseek.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/lseek.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/mmap.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/posix_fadvise.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/sendfile.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/statfs.c
    sysdeps/unix/sysv/linux/generic/wordsize-32/truncate.c
    sysdeps/unix/sysv/linux/generic/brk.c
    sysdeps/unix/sysv/linux/generic/dl-origin.c
    sysdeps/unix/sysv/linux/generic/umount.c
    sysdeps/unix/sysv/linux/generic/creat.c
    sysdeps/unix/sysv/linux/generic/pause.c
    sysdeps/unix/sysv/linux/generic/Makefile
    sysdeps/unix/sysv/linux/generic/select.c
    sysdeps/unix/sysv/linux/generic/epoll_create.c
    sysdeps/unix/sysv/linux/generic/epoll_wait.c
    sysdeps/unix/sysv/linux/generic/inotify_init.c
    sysdeps/unix/sysv/linux/generic/dup2.c
    sysdeps/unix/sysv/linux/generic/mkdir.c
    sysdeps/unix/sysv/linux/generic/rename.c
    sysdeps/unix/sysv/linux/generic/utimes.c

    --
    Chris Metcalf, Tilera Corp.
    http://www.tilera.com



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