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    SubjectRe: [PATCH 6/8] ptrace: arch_ptrace -ENOSYS return
    > Hmm.. I see the whole series, and I see this patch, but I think it adds 
    > new code and new complexity, and I don't really see *why*.

    The motivation is to get the arch function out of the code path for the
    machine-independent request handling. I want to be able to change the
    implementation later without touching the arch code again.

    The arguments passed down to arch_ptrace are sufficient for what the arch
    code itself needs and for the current implementation in ptrace_request.
    In future, I'd like the option of changing the code for the standard
    requests to use a local data structure set up at the start of ptrace, and
    such like (so more pointers and the like would need to be passed down to
    ptrace_request). These patches let me remove ptrace_request or change
    its calling convention without touching the arch code again.

    > Wouldn't it be nicer to just let "arch_ptrace()" return a flag saying
    > whether it handled things or not?

    It would certainly be nicer. I would prefer:

    extern int arch_ptrace(struct task_struct *child, long request,
    long addr, long data, long *retval);

    where it returns an error code or it returns 0 and *retval is the value
    or it returns 1 and it didn't do anything.

    The reason I took the approach I did instead is incrementalism.
    I can't change that signature without breaking about 22 arch builds.
    I'm only really prepared to thoroughly verify a change on 2 of those
    myself. It should be a simple enough change to make blind and get
    right. But I've gotten a lot of things wrong before. On principle,
    I wouldn't really expect anyone to sign off on stuff I won't even
    claim to have tried. I did the forced_successful_syscall_return()
    macro for arch's I don't try to build, and was just awful sure golly
    that I hadn't got them wrong, because the generic change would break
    those few arch's (not 20) without it.

    So this ugliness seemed like a better bet than waiting for 20 more
    arch sign-offs before any of it could go in. You are certainly in a
    position to just change the generic signature and make every arch do
    the update (or fix your typos if you just tweak them all blind), and
    let them grumble. I did not presume to do so.

    If you'd like a patch that changes this signature, updates all arch
    implementations, and is actually verified to compile and work only
    on x86 and powerpc, I'll be happy to provide that.


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