LoongArch: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

mainline inclusion
from mainline-v6.5-rc1
commit 5779e3c0
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MWTU
CVE: NA

--------------------------------

The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the LoongArch platform.

We introduce a new structure called fgraph_ret_regs for the LoongArch
platform to hold return registers and the frame pointer. We then fill
its content in the return_to_handler and pass its address to the
function ftrace_return_to_handler to record the return value.

Link: https://lkml.kernel.org/r/c5462255e435fab363895c2d7433bc0f5a140411.1680954589.git.pengdonglin@sangfor.com.cn



Signed-off-by: Yongzhen Zhang <zhangyongzhen@kylinos.cn>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>