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  • Frederic Weisbecker's avatar
    tracing, x86: add low level support for ftrace return tracing · caf4b323
    Frederic Weisbecker authored
    
    
    Impact: add infrastructure for function-return tracing
    
    Add low level support for ftrace return tracing.
    
    This plug-in stores return addresses on the thread_info structure of
    the current task.
    
    The index of the current return address is initialized when the task
    is the first one (init) and when a process forks (the child). It is
    not needed when a task does a sys_execve because after this syscall,
    it still needs to return on the kernel functions it called.
    
    Note that the code of return_to_handler has been suggested by Steven
    Rostedt as almost all of the ideas of improvements in this V3.
    
    For purpose of security, arch/x86/kernel/process_32.c is not traced
    because __switch_to() changes the current task during its execution.
    That could cause inconsistency in the stored return address of this
    function even if I didn't have any crash after testing with tracing on
    this function enabled.
    
    Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    caf4b323