Debugging Linux Kernel Using SystemTap Part3 - call and return

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To probe a function at the entrance ( call the handler ) add the .call at the end of the probe , and to probe the function at the exit add the .return at the end of the probe.

Syntax:

 probe kernel.function("function_name").call {
...
}

probe kernel.function("function_name").return {
...
}

Example:

probe kernel.function("do_sys_open").call{
    printf("File %s\n", user_string($filename))
}

probe kernel.function("do_sys_open").return{
    printf("Return %d\n", $return)
}

O/P:


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