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    SubjectRe: Compat 32-bit syscall entry from 64-bit task!?
    In arch_ptrace, task_user_regset_view is called on current.  On an x86-64
    kernel, that path is only reached for a 64-bit syscall. compat_arch_ptrace
    doesn't use it at all, always using the 32-bit view. So your change would
    have no effect on PTRACE_GETREGS.

    It would only affect PTRACE_GETREGSET, which calls task_user_regset_view on
    the target task. Is that what you meant? I think that would be confusing
    at best. A caller of PTRACE_GETREGSET is expecting a particular layout
    based on what type of task he thinks he's dealing with. The caller can
    look at the iov_len in the result to discern which layout it actually got
    filled in, but I don't think that's what callers expect.

    The other use of task_user_regset_view is in core dump
    (binfmt_elf.c:fill_note_info). Off hand I don't think there's a way a core
    dump can be started while still "inside" a syscall so that TS_COMPAT could
    ever be set. But that should be double-checked.

    As to whether it was considered before, I doubt that it was. I don't
    really recall the sequence of events, but I think that I did all the
    user_regset code before I was really cognizant of the TS_COMPAT subtleties.


    Thanks,
    Roland


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