From b83b43ffc6e4b514ca034a0fbdee01322e2f7022 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Tue, 15 Oct 2019 09:00:55 -0400 Subject: fgraph: Fix function type mismatches of ftrace_graph_return using ftrace_stub The C compiler is allowing more checks to make sure that function pointers are assigned to the correct prototype function. Unfortunately, the function graph tracer uses a special name with its assigned ftrace_graph_return function pointer that maps to a stub function used by the function tracer (ftrace_stub). The ftrace_graph_return variable is compared to the ftrace_stub in some archs to know if the function graph tracer is enabled or not. This means we can not just simply create a new function stub that compares it without modifying all the archs. Instead, have the linker script create a function_graph_stub that maps to ftrace_stub, and this way we can define the prototype for it to match the prototype of ftrace_graph_return, and make the compiler checks all happy! Link: http://lkml.kernel.org/r/20191015090055.789a0aed@gandalf.local.home Cc: linux-sh@vger.kernel.org Cc: Yoshinori Sato Cc: Rich Felker Reported-by: Sami Tolvanen Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/fgraph.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'kernel/trace') diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index 7950a0356042..fa3ce10d0405 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -332,9 +332,14 @@ int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace) return 0; } +/* + * Simply points to ftrace_stub, but with the proper protocol. + * Defined by the linker script in linux/vmlinux.lds.h + */ +extern void ftrace_graph_stub(struct ftrace_graph_ret *); + /* The callbacks that hook a function */ -trace_func_graph_ret_t ftrace_graph_return = - (trace_func_graph_ret_t)ftrace_stub; +trace_func_graph_ret_t ftrace_graph_return = ftrace_graph_stub; trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub; static trace_func_graph_ent_t __ftrace_graph_entry = ftrace_graph_entry_stub; @@ -614,7 +619,7 @@ void unregister_ftrace_graph(struct fgraph_ops *gops) goto out; ftrace_graph_active--; - ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub; + ftrace_graph_return = ftrace_graph_stub; ftrace_graph_entry = ftrace_graph_entry_stub; __ftrace_graph_entry = ftrace_graph_entry_stub; ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET); -- cgit