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    SubjectRe: [PATCH 08/10] Use __kernel_ulong_t in struct msqid64_ds
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    On Thu, May 17, 2012 at 8:21 PM, H. Peter Anvin <hpa@kernel.org> wrote:
    > On 05/17/2012 04:51 PM, H. Peter Anvin wrote:
    >>
    >> This patch and the one before it seems to have another problem: we
    >> currently define __BITS_PER_LONG as:
    >>
    >> #ifdef __x86_64__
    >> # define __BITS_PER_LONG 64
    >> #else
    >> # define __BITS_PER_LONG 32
    >> #endif
    >>
    >
    > H.J., do you see any problem *other* than this wretched struct
    > msqid64_ds with changing the above from __x86_64__ to
    >
    > #if defined(__x86_64__) && !defined(__ILP32__)
    >
    > ... in the above?
    >
    > As far as struct msqid64_ds,  I think we can fix it simply because x86
    > is the only compat-aware architecture which has to deal with it.
    >
    > (Incidentally, if sh is ever expanded to 64 bits, it will have a problem
    > in the bigendian configuration...)

    That will be wrong. __BITS_PER_LONG defines # bits of long
    as seen by kernel. We don't use it in user space. Remember
    x32 uses the identical interface as x86-64. So

    #ifdef __x86_64__
    # define __BITS_PER_LONG 64
    #else
    # define __BITS_PER_LONG 32
    #endif

    struct msqid64_ds {
    struct ipc64_perm msg_perm;
    __kernel_time_t msg_stime; /* last msgsnd time */
    #if __BITS_PER_LONG != 64
    unsigned long __unused1;
    #endif
    __kernel_time_t msg_rtime; /* last msgrcv time */
    #if __BITS_PER_LONG != 64
    unsigned long __unused2;
    #endif
    __kernel_time_t msg_ctime; /* last change time */
    #if __BITS_PER_LONG != 64
    unsigned long __unused3;
    #endif

    are absolutely correct for x32. You can think

    #if __BITS_PER_LONG != 64

    as

    #ifndef __x86_64__

    which is used in glibc.


    --
    H.J.
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