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x86_64 has had fentry support for some time. I did not add support to x86_32 as I was unsure if it will be used much in the future. It is still very much used, and there's issues with function graph tracing with gcc playing around with the mcount frames, causing function graph to panic. The fentry code does not have this issue, and is able to cope as there is no frame to mess up. Note, this only adds support for fentry when DYNAMIC_FTRACE is set. There's really no reason to not have that set, because the performance of the machine drops significantly when it's not enabled. Keep !DYNAMIC_FTRACE around to test it off, as there's still some archs that have FTRACE but not DYNAMIC_FTRACE. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20170323143446.052202377@goodmis.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.