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    SubjectRe: [uml-devel] Re: [RFC] PATCH 3/4 - Time virtualization : PTRACE_SYSCALL_MASK
    > For UML, instead, it's important to set that some peculiar syscalls are not 
    > traced, that the mask is 1-extended and that errors are reported.
    >
    > So, I suggest a "flags" parameter for this. Sadly, we're using the ptrace()
    > syscall and there's no 5th argument normally, we could either use it (IIRC
    > some calls use the 5th regs indeed), or pass as "data" a struct with flags
    > and the mask.
    >
    > The flags could be:
    >
    > MASK_DEFAULT_TRACE (set the default to 1 for remaining bits)
    > MASK_DEFAULT_IGNORE (set the default to 0 for remaining bits)
    > MASK_STRICT_VERIFY (return -EINVAL for bits exceeding NR_syscalls and set
    > differently than the default).
    >
    > probably with a reasonable prefix to avoid namespace pollution (something like
    > "PT_SC_-").

    You might as well introduce yet another ptrace call which returns the number
    of system calls and for this ptrace call force user space to pass a complete
    bitmap. Sounds easier to me.

    > > The tracing process won't see
    > > any of the non existant syscalls it requested to see anyway.
    > No, you misunderstood the code, it does the opposite very different - the loop

    Looks I missed a few "!"s :)
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