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    Subject[PATCH 3/3] TEST PATCH - ftrace example patch for use of trace pipe headers
    DO NOT APPLY THIS PATCH!!!!!

    This is an example of implementing a plugin for header for the trace_pipe
    file.

    DO NOT APPLY THIS PATCH!!!!!

    Signed-off-by: Steven Rostedt <srostedt@redhat.com>
    ---
    kernel/trace/trace_functions.c | 41 +++++++++++++++++++++++++++++++++++++++++
    1 file changed, 41 insertions(+)

    Index: linux-sched-devel.git/kernel/trace/trace_functions.c
    ===================================================================
    --- linux-sched-devel.git.orig/kernel/trace/trace_functions.c 2008-04-21 16:50:49.000000000 -0400
    +++ linux-sched-devel.git/kernel/trace/trace_functions.c 2008-04-21 16:54:55.000000000 -0400
    @@ -16,6 +16,45 @@

    #include "trace.h"

    +static void function_pipe_open(struct trace_iterator *iter)
    +{
    + int *traceme;
    +
    + traceme = kzalloc(sizeof(int), GFP_KERNEL);
    + if (!traceme)
    + return;
    +
    + iter->private = traceme;
    +}
    +
    +static ssize_t function_read(struct trace_iterator *iter,
    + struct file *filp, char __user *ubuf,
    + size_t cnt, loff_t *ppos)
    +{
    + unsigned char head[] = "Test header\n";
    + int *traced;
    + int ret;
    +
    + if (!iter->private)
    + return 0;
    +
    + traced = iter->private;
    + if (*traced >= sizeof(head)-1)
    + return 0;
    +
    + if (cnt > sizeof(head)-1)
    + cnt = sizeof(head)-1;
    +
    + ret = copy_to_user(ubuf, head + *traced, cnt);
    +
    + *traced += cnt;
    +
    + if (ret)
    + cnt = -EFAULT;
    +
    + return cnt;
    +}
    +
    static void function_reset(struct trace_array *tr)
    {
    int cpu;
    @@ -68,6 +107,8 @@ static struct tracer function_trace __re
    #ifdef CONFIG_FTRACE_SELFTEST
    .selftest = trace_selftest_startup_function,
    #endif
    + .pipe_open = function_pipe_open,
    + .read = function_read,
    };

    static __init int init_function_trace(void)
    --


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