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    SubjectRe: [RFC] convert ftrace syscall tracer to TRACE_EVENT()

    * Frédéric Weisbecker <> wrote:

    > > Secondly, we should reuse the information we get in
    > > SYSCALL_DEFINE, to construct the TRACE_EVENT tracepoints
    > > directly - without having to list all syscalls again in a
    > > separate file.
    > Indeed, that's not trivial though, but feasible. I'm not sure we
    > can reuse the TRACE_EVENT macro directly inside SYSCALL_DEFINE.
    > The resulting macro tempest effect that would occur confuses me
    > and I have troubles to imagine the result.

    Lets take an example. This syscall:

    SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy,
    struct sched_param __user *, param)

    Is equivalent to:

    SYSCALL_DEFINE3(name, t1, v1, t2, v2, t3, v3)

    ('t' for type, 'v' for variable/value).

    This would transform into the following TRACE_EVENT() construct:


    TP_PROTO(t1 v1, t2 v2),
    TP_ARGS(v1, v2),
    __field(t1, v1)
    __field(t2, v2)
    __entry->v1 = v1;
    __entry->v2 = v2;
    TP_printk("%016Lx %016Lx", (u64)__entry->v1, (u64)__entry->v2)

    We need TRACE_EVENT_SYSCALL[123456] definitions, and that's it.

    The only place where we lose type information is the printk format -
    but that's not a big issue, as i'd expect the event record to be the
    main user of this.

    [ In addition to this, we could extend DEFINE_SYSCALL[1..6] with a
    (optional) format string definition field, and fill that in for
    anything that matters. ]

    Note, this assumes that all syscall types can be described via
    __field() - i think that's correct. (we dont want to deref strings
    as they are untrusted, and there are no arrays in syscall

    Can you see any complication?

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      Last update: 2009-05-09 15:37    [W:0.023 / U:5.084 seconds]
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