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If a direct hook is attached to a function that ftrace also has a function attached to it, then it is required that the ftrace_ops_list_func() is used to iterate over the registered ftrace callbacks. This will also include the direct ftrace_ops helper, that tells ftrace_regs_caller where to return to (the direct callback and not the function that called it). As this direct helper is only to handle the case of ftrace callbacks attached to the same function as the direct callback, the ftrace callback allocated trampolines (used to only call them), should never be used to return back to a direct callback. Only copy the portion of the ftrace_regs_caller that will return back to what called it, and not the portion that returns back to the direct caller. The direct ftrace_ops must then pick the ftrace_regs_caller builtin function as its own trampoline to ensure that it will never have one allocated for it (which would not include the handling of direct callbacks). Link: http://lkml.kernel.org/r/20200422162750.495903799@goodmis.org Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.